path: root/.config/vis/plugins/vis-lspc/init.lua

-- Copyright (c) 2021-2024 Florian Fischer. All rights reserved.
--
-- This file is part of vis-lspc.
--
-- vis-lspc is free software: you can redistribute it and/or modify it under the
-- terms of the GNU General Public License as published by the Free Software
-- Foundation, either version 3 of the License, or (at your option) any later
-- version.
--
-- vis-lspc is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-- FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License along with
-- vis-lspc found in the LICENSE file. If not, see <https://www.gnu.org/licenses/>.
--
-- We require vis compiled with the communicate patch
if not vis.communicate then
  vis:info('LSPC Error: language server support requires vis communicate patch')
  return {}
end

local source_str = debug.getinfo(1, 'S').source:sub(2)
local source_path = source_str:match('(.*/)')

-- state of our language server client
local lspc = dofile(source_path .. 'lspc.lua')

-- initialise the logging system
lspc.logger = dofile(source_path .. 'log.lua').lazyNew('lspc', lspc)

local parser = dofile(source_path .. 'parser.lua')

-- initialise the util module
local util = dofile(source_path .. 'util.lua').init(lspc)

-- initialise the settings module
local settings = dofile(source_path .. 'settings.lua').init(lspc)

-- load a suitable json module
lspc.json = dofile(source_path .. 'json.lua')

local jsonrpc = {}
jsonrpc.error_codes = {
  -- json rpc errors
  ParseError = -32700,
  InvalidRequest = -32600,
  MethodNotFound = -32601,
  InvalidParams = -32602,
  InternalError = -32603,

  ServerNotInitialized = -32002,
  UnknownErrorCode = -32001,

  -- lsp errors
  ContentModified = -32801,
  RequestCancelled = -32800,
}

-- get vis's pid to pass it to the language servers
local vis_pid
do
  local vis_proc_file = io.open('/proc/self/stat', 'r')
  if vis_proc_file then
    vis_pid = vis_proc_file:read('*n')
    vis_proc_file:close()

  else -- fallback if /proc/self/stat
    local out = util.capture_cmd('sh -c "echo $PPID"')
    vis_pid = tonumber(out)
  end
end
assert(vis_pid)

-- mapping function between vis lexer names and LSP languageIds
local function syntax_to_languageId(syntax)
  -- LuaFormatter off
  local map = {
    ansi_c = 'c',
    javascript = 'jsx',
    typescript = 'tsx',
  }
  -- LuaFormatter on

  return map[syntax] or syntax
end

-- map of known language servers per syntax
lspc.ls_map = dofile(source_path .. 'supported-servers.lua')

--- Return the name of the language server for this syntax
-- @param syntax the syntax the language server should support
-- @return the name of the languauge server configured for syntax
local function get_ls_name_for_syntax(syntax)
  local ls_def = lspc.ls_map[syntax]
  if not ls_def then
    return nil, 'No language server available for ' .. syntax
  end
  return ls_def.name
end

-- Document position code
-- https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocumentPositionParams

-- We use the following position/location/file related types in  vis-lspc:
-- pos - like in vis a 0-based byte offset into the file.
-- path - posix path used by vis
-- uri - file uri used by LSP

-- lsp_position - 0-based tuple (line, character)
-- lsp_document_position - aka. LSP TextDocumentPosition, tuple of (uri, lsp_position)

-- vis_selection - 1-based tuple (line, cul) (character)
--              Can be used with with Selection:to
-- vis_document_position - 1-based tuple of (path, line, cul)

-- vis_range - tuple of 0-based byte offsets (finish, start)
-- lsp_range - aka. Range, tuple of two lsp_positions (start, end)

-- There exist helper function to convert from one type into another
-- aswell as helper to retrieve the current primary selection from a vis.window

local function path_to_uri(path)
  return 'file://' .. path
end

-- uri decode logic taken from
-- https://stackoverflow.com/questions/20405985/lua-decodeuri-luvit
local uri_decode_table = {}
for i = 0, 255 do
  uri_decode_table[string.format('%02x', i)] = string.char(i)
  uri_decode_table[string.format('%02X', i)] = string.char(i)
end

local function decode_uri(s)
  return (s:gsub('%%(%x%x)', uri_decode_table))
end

local function uri_to_path(uri)
  return decode_uri(uri:gsub('file://', ''))
end

-- get the vis_selection from current primary selection
local function get_selection(win)
  return {line = win.selection.line, col = win.selection.col}
end

-- convert lsp_position to vis_selection
local function lsp_pos_to_vis_sel(pos)
  return {line = pos.line + 1, col = pos.character + 1}
end

-- convert vis_selection to lsp_position
local function vis_sel_to_lsp_pos(pos)
  return {line = pos.line - 1, character = pos.col - 1}
end

-- convert our vis_document_position to lsp_document_position aka. TextDocumentPosition
local function vis_doc_pos_to_lsp(doc_pos)
  return {
    textDocument = {uri = path_to_uri(doc_pos.file)},
    position = vis_sel_to_lsp_pos({line = doc_pos.line, col = doc_pos.col}),
  }
end

-- convert lsp_document_position to vis_document_position
local function lsp_doc_pos_to_vis(doc_pos)
  local pos = lsp_pos_to_vis_sel(doc_pos.position)
  return {
    file = uri_to_path(doc_pos.textDocument.uri),
    line = pos.line,
    col = pos.col,
  }
end

-- get document position of the main curser
local function vis_get_doc_pos(win)
  return {
    file = win.file.path,
    line = win.selection.line,
    col = win.selection.col,
  }
end

--- Convert a lsp_range to a vis_range
-- @param file the file in which the range lies
-- @param lsp_range the LSP range that should be converted
-- @return the according vis range
local function lsp_range_to_vis_range(file, lsp_range)
  local start = lsp_pos_to_vis_sel(lsp_range.start)
  local finish = lsp_pos_to_vis_sel(lsp_range['end'])

  local positions = util.vis_sorted_selections_to_pos(file, {start, finish})
  local start_pos = positions[1]
  local finish_pos = positions[2]

  return {start = start_pos, finish = finish_pos}
end

--- Check if a lsp_position lies before another.
-- @param p1 first lsp_position to compare
-- @param p2 second lsp_position to compare
-- @return true if p1 lies before p2
local function lsp_pos_before(p1, p2)
  return p1.line < p2.line or (p1.line == p2.line and p1.character < p2.character)
end

--- Check if a lsp_range starts before another.
-- The ranges may overlap since only their start positions are compared.
-- @param r1 first lsp_range to compare
-- @param r2 second lsp_range to compare
-- @return true if r1 is starts before r2
local function lsp_range_starts_before(r1, r2)
  return lsp_pos_before(r1.start, r2.start)
end

-- concatenate all numeric values in choices and pass it on stdin to lspc.menu_cmd
local function lspc_select(choices)
  local menu_input = ''
  local i = 0
  for _, c in ipairs(choices) do
    i = i + 1
    menu_input = menu_input .. c .. '\n'
  end

  -- select the only possible choice
  if i < 2 then
    return choices[1]
  end

  local fullscreen = lspc.menu_cmd == 'fzf'
  local status, output = util.vis_pipe(menu_input, lspc.menu_cmd, fullscreen)

  local choice = nil
  if status == 0 then
    -- trim newline from selection
    if output:sub(-1) == '\n' then
      choice = output:sub(1, -2)
    else
      choice = output
    end
  end

  vis:redraw()
  return choice
end

local function lspc_select_location(locations)
  -- Collect all paths with a list of their locations so we
  -- can sort the locations before calling file_line_iterator_to_n
  local collected = {}

  for _, location in ipairs(locations) do
    local path = uri_to_path(location.uri or location.targetUri)
    local range = location.range or location.targetSelectionRange
    local position = lsp_pos_to_vis_sel(range.start)

    if collected[path] == nil then
      table.insert(collected, path)
      collected[path] = {}
    end

    table.insert(collected[path], {
      ['location'] = location,
      ['position'] = position,
    })
  end

  local choices = {}
  local cwd_components = util.capture_cmd('pwd')
  -- Strip trailing newline
  cwd_components = util.split_path_into_components(cwd_components:sub(1, #cwd_components - 1))

  for _, path in ipairs(collected) do
    -- Sort positions
    table.sort(collected[path], function(a, b)
      return a['position'].line < b['position'].line
    end)

    local rel_path = util.get_relative_path(cwd_components, path)
    -- Use the already open file if present to get accurate line content for references
    local line_iter
    if lspc.open_files[path] ~= nil then
      line_iter = function(n)
        if n == -1 then
          return nil
        end

        return lspc.open_files[path].file.lines[n]
      end
    else
      line_iter = util.file_line_iterator_to_n(path)
    end

    for _, val in ipairs(collected[path]) do
      local position = val['position']
      local location = val['location']

      local choice = rel_path .. ':' .. ('%.0f'):format(position.line) .. ':' ..
                         ('%.0f'):format(position.col) .. ':' .. (line_iter(position.line) or '')
      table.insert(choices, choice)
      choices[choice] = location
    end

    -- close the iterator
    line_iter(-1)
  end

  -- select a location
  local choice = lspc_select(choices)
  if not choice then
    return nil
  end

  return choices[choice]
end

-- get a user confirmation
-- return true if user selected yes, false otherwise
local function lspc_confirm(prompt)
  local choices = 'no\nyes'

  local cmd = lspc.confirm_cmd

  if prompt then
    cmd = cmd .. ' -p \'' .. prompt .. '\''
  end

  lspc:log('get confirmation using: ' .. cmd)

  local choice = nil
  local status, output = util.vis_pipe(choices, cmd)
  if status == 0 then
    -- trim newline from selection
    if output:sub(-1) == '\n' then
      choice = output:sub(1, -2)
    else
      choice = output
    end
  end

  vis:redraw()
  return choice == 'yes'
end

local function vis_open_file(file, cmd)
  vis:command(('%s %s'):format(cmd, file:gsub('[\\\t "\']', '\\%1'):gsub('\n', '\\n')))
end

-- open a doc_pos using the vis command <cmd>
local function vis_open_doc_pos(doc_pos, cmd, win)
  if win and win ~= vis.win then
    vis.win = win
  end
  assert(cmd)
  if vis.win.file.path ~= doc_pos.file then
    if vis.win.file.modified and cmd == 'e' then
      if lspc_confirm('Save currently open file:') then
        vis:command('w')
      else
        vis:info('Not opening new file, current file has unsaved changes')
        return
      end
    end
    vis_open_file(doc_pos.file, cmd)
    if doc_pos.line then
      vis.win.selection:to(doc_pos.line, doc_pos.col or 0)
    end
    vis:command('lspc-open')
  else
    vis.win.selection:to(doc_pos.line, doc_pos.col)
  end
end

-- Support jumping between document positions
-- Stack of edited document positions
local doc_pos_history = {}

local function vis_push_doc_pos(win)
  local old_doc_pos = vis_get_doc_pos(win)
  table.insert(doc_pos_history, old_doc_pos)
end

-- open a new doc_pos remembering the old if it is replaced
local function vis_open_new_doc_pos(doc_pos, cmd, win)
  win = win or vis.win
  if cmd == 'e' then
    vis_push_doc_pos(win)
  end

  vis_open_doc_pos(doc_pos, cmd, win)
end

lspc.open_file = function(win, path, line, col, cmd)
  vis_open_new_doc_pos({file = path, line = line, col = col}, cmd or 'e', win)
end

local function vis_pop_doc_pos(win)
  local last_doc_pos = table.remove(doc_pos_history)
  if not last_doc_pos then
    return 'Document history is empty'
  end

  vis_open_doc_pos(last_doc_pos, 'e', win)
end

-- apply a textEdit received from the language server
local function vis_apply_textEdit(win, file, textEdit)
  assert(win.file == file)

  local range = lsp_range_to_vis_range(file, textEdit.range)

  file:delete(range)
  file:insert(range.start, textEdit.newText)

  win.selection.anchored = false
  win.selection.pos = range.start + string.len(textEdit.newText)

  win:draw()
end

-- apply a list of textEdits received from the language server
local function vis_apply_textEdits(win, file, textEdits)
  assert(win.file == file)

  local edits = {}
  for _, textEdit in ipairs(textEdits) do
    local range = lsp_range_to_vis_range(file, textEdit.range)
    table.insert(edits, {
      mark = file:mark_set(range.start),
      len = range.finish - range.start,
      newText = textEdit.newText,
    })
  end
  for _, edit in ipairs(edits) do
    local pos = file:mark_get(edit.mark)
    file:delete(pos, edit.len)
    file:insert(pos, edit.newText)
  end
  win:draw()
end

--- Close the message window
-- TODO: close the dedicated lspc message window
local function lspc_close_message_win()
  if lspc.show_message == 'message' then
    vis:message('')
    vis:command('q')
  end
end

--- Present a message to the user
-- TODO: use a dedicated lspc message window
local function lspc_show_message(msg, hdr, syntax)
  local current_win = vis.win

  if lspc.show_message == 'message' then
    local to_show = (hdr or '') .. msg .. '\n'
    vis:message(to_show)
    vis.win.selection = vis.win.file.size - #to_show
    vis:feedkeys('zt')

  elseif lspc.show_message == 'open' then
    vis:command('open')
    if syntax then
      vis:command('set syntax ' .. syntax)
    end

    vis.win.file:insert(0, msg)
    vis.win.selection.pos = 0
  else
    lspc:err('invalid message configuration "' .. lspc.show_message .. '".')
  end

  -- reset the focus to the current window
  vis.win = current_win
end

-- apply a WorkspaceEdit received from the language server
local function vis_apply_workspaceEdit(_, _, workspaceEdit)
  local file_edits = workspaceEdit.changes
  assert(file_edits or workspaceEdit.documentChanges)

  -- try to convert NOT SUPPORTED TextDocumentEdit[]
  -- We do not announce support for versioned DocumentChanges in our
  -- client capabilities, but some LSP servers ignore our capabilities
  -- sending them anyway.
  if not file_edits then
    file_edits = {}
    for _, edit in ipairs(workspaceEdit.documentChanges) do
      file_edits[edit.textDocument.uri] = edit.edits
    end
  end

  if not lspc.autoconfirm_edits then
    -- generate change summary
    local summary = '--- workspace edit summary ---\n'
    for uri, edits in pairs(file_edits) do
      local path = uri_to_path(uri)
      summary = summary .. path .. ':\n'
      for i, edit in ipairs(edits) do
        summary = summary .. '\t' .. i .. '.: ' .. lspc.json.encode(edit) .. '\n'
      end
    end

    lspc_show_message(summary)
    vis:redraw()

    -- get user confirmation
    local confirmation = lspc_confirm('apply changes:')

    -- close summary window
    lspc_close_message_win()

    if not confirmation then
      return
    end
  end

  -- apply changes to open files
  for uri, edits in pairs(file_edits) do
    local path = uri_to_path(uri)

    -- search all open windows for this uri
    local win_with_file
    for win in vis:windows() do
      if win.file and win.file.path == path then
        win_with_file = win
        break
      end
    end

    -- The file is not currently opened -> open it
    local opened
    if not win_with_file then
      vis_open_file(path, 'o')
      win_with_file = vis.win
      opened = true
    end

    -- Remember the current primary cursor position
    local old_pos = win_with_file.selection.pos

    for _, edit in ipairs(edits) do
      vis_apply_textEdit(win_with_file, win_with_file.file, edit)
    end

    -- Restore the remembered primary cursor position
    if lspc.workspace_edit_remember_cursor then
      win_with_file.selection.pos = old_pos
    end

    -- save changes and close the opened window
    if opened then
      vis:command('wq')
    end
  end
end

-- translate file line number to the relative row the line is displayed in the view of a window
-- returns an integer relative to the window if line is in view (starting at 1)
-- returns nil otherwise
local function file_lineno_to_viewport_lineno(win, file_lineno)
  -- The line is not in the current viewport
  if file_lineno < win.viewport.lines.start or file_lineno > win.viewport.lines.finish then
    return nil
  end

  -- The line is in the viewport and there is no wrapped line
  if win.viewport.lines.finish - win.viewport.lines.start == win.viewport.height then
    return file_lineno - win.viewport.lines.start
  else -- Determine the position in the viewport considering possible prior wrapped lines
    local view_lineno = 0
    for n = win.viewport.lines.start, file_lineno do
      view_lineno = view_lineno + 1
      -- Wrapped lines shift our displayed line down
      local line_len = #win.file.lines[n]
      if not win.options.expandtab then
        line_len = util.visual_chars_in_line(win, win.file.lines[n], line_len)
      end

      if line_len >= win.viewport.width then
        view_lineno = view_lineno + math.floor(line_len / win.viewport.width)
      end
    end
    return view_lineno
  end
end

local function lspc_highlight_server_diagnostics(win, server_diagnostics, style)
  if not style then
    style = lspc.diagnostic_style_id or win.STYLE_LEXER_MAX
  end

  local level_mapping = {
    [1] = lspc.diagnostic_styles.error,
    [2] = lspc.diagnostic_styles.warning,
    [3] = lspc.diagnostic_styles.information,
    [4] = lspc.diagnostic_styles.hint,
  }

  for _, diagnostic in ipairs(server_diagnostics) do
    local diagnostic_style = level_mapping[diagnostic.severity] or level_mapping[1]
    assert(win:style_define(style, diagnostic_style))

    if lspc.highlight_diagnostics == 'range' then
      local range = diagnostic.vis_range

      -- LSP ranges use an exclusive finish
      local finish = range.finish - 1

      -- make sure to highlight only ranges which actually contain the diagnostic
      if diagnostic.content == win.file:content(range) then
        win:style(style, range.start, finish)
      end

    elseif lspc.highlight_diagnostics == 'line' then
      if not win.style_pos then
        lspc:err('Vis build does not support style_pos')
        return
      end

      local start_line = diagnostic.range.start.line
      local end_line = diagnostic.range['end'].line
      for line = start_line, end_line, 1 do
        local row = file_lineno_to_viewport_lineno(win, line)
        if row then
          -- Heuristic how many cells need to be styled
          -- (at least one plus the decimal places of the line number).
          for i = 0, #('' .. line) do
            win:style_pos(style, i, row)
          end
        end
      end
    end
  end
end

local function lspc_highlight_diagnostics(win, diagnostics, style)
  for _, server_diagnostics in pairs(diagnostics) do
    lspc_highlight_server_diagnostics(win, server_diagnostics, style)
  end
end

--- LanguageServer class metatable
local LanguageServer = {}

--- send a RPC message to the language server
-- @param req The request to send
function LanguageServer:rpc(req)
  req.jsonrpc = '2.0'

  local content_part = lspc.json.encode(req)
  local content_len = string.len(content_part)

  local header_part = 'Content-Length: ' .. tostring(content_len)
  local msg = header_part .. '\r\n\r\n' .. content_part
  lspc:log('LSPC Sending -> ' .. self.name .. ': ' .. msg)

  self.fd:write(msg)
  self.fd:flush()
end

--- Send a RPC notification to the language server
-- @param name the name of the notification
-- @param params the parameters to send
function LanguageServer:send_notification(name, params)
  self:rpc({method = name, params = params})
end

--- Send a textDocument/didChange notification to the language server
-- @param the vis file object which changed
function LanguageServer:send_did_change(file)
  lspc:log('send didChange')
  local new_version = assert(lspc.open_files[file.path]).version + 1
  lspc.open_files[file.path].version = new_version

  local document = {uri = path_to_uri(file.path), version = new_version}
  local changes = {{text = file:content(0, file.size)}}
  local params = {textDocument = document, contentChanges = changes}
  self:send_notification('textDocument/didChange', params)
end

function LanguageServer:request_diagnostics(win)
  -- check if the language server has a provider for this method
  if self.capabilities['diagnosticProvider'] then
    local params = {textDocument = {uri = path_to_uri(win.file.path)}}
    self:call_method('textDocument/diagnostic', params, win, params.textDocument)
  end
end

--- Send a rpc method call to the language server.
-- @param method name of remote procedure to call
-- @param params the parameter passed to the remote procedure
-- @param win the related vis window object
-- @param ctx a opaque context value stored with the request
function LanguageServer:call_method(method, params, win, ctx)
  local id = self.id
  self.id = self.id + 1

  local req = {id = id, method = method, params = params}
  self.inflight[id] = req

  self:rpc(req)
  -- remember the current window to apply the effects of a
  -- method call in the original window
  self.inflight[id].win = win

  -- remember the user provided ctx value
  -- ctx can be used to remember arbitrary data from method invocation till
  -- method response handling
  -- The goto-location methods remember in ctx how to open the location
  self.inflight[id].ctx = ctx
end

--- Call textDocument/<method> of the server
-- We send a didChange notification upfront to make sure the server sees our
-- current state. This is not ideal since we are sending more data than needed
-- and the server has less time to parse the new file content and do its work
-- resulting in longer stalls after method invocation.
-- @param method the name of LSP textDocument method
-- @param params the parameters of the method call
-- @param win the related vis window object
-- @param ctx a opaque context value stored with the request
function LanguageServer:call_text_document_method(method, params, win, ctx)
  self:send_did_change(win.file)
  self:call_method('textDocument/' .. method, params, win, ctx)
  self:request_diagnostics(win)
end

--- Call the textDocument/symbol method of the server if provided
function LanguageServer:request_symbols(win, ctx)
  if self.capabilities['documentSymbolProvider'] then
    local params = {textDocument = {uri = path_to_uri(win.file.path)}}
    self:call_text_document_method('documentSymbol', params, win, ctx)
  end
end

local function lspc_handle_goto_method_response(req, result)
  if not result or type(result) ~= 'table' or next(result) == nil then
    lspc:warn(req.method .. ' found no results')
    return
  end

  local location
  -- result actually a list of results
  if type(result) == 'table' then
    location = lspc_select_location(result)
    if not location then
      return
    end
  else
    location = result
  end
  assert(location)

  -- location is a Location
  local lsp_doc_pos
  if location.uri then
    lspc:log('Handle location: ' .. lspc.json.encode(location))
    lsp_doc_pos = {
      textDocument = {uri = location.uri},
      position = {
        line = location.range.start.line,
        character = location.range.start.character,
      },
    }
    -- location is a LocationLink
  elseif location.targetUri then
    lspc:log('Handle locationLink: ' .. lspc.json.encode(location))
    lsp_doc_pos = {
      textDocument = {uri = location.targetUri},
      position = {
        line = location.targetSelectionRange.start.line,
        character = location.targetSelectionRange.start.character,
      },
    }
  else
    lspc:warn('Unknown location type: ' .. lspc.json.encode(location))
  end

  local doc_pos = lsp_doc_pos_to_vis(lsp_doc_pos)
  vis_open_new_doc_pos(doc_pos, req.ctx, req.win)
end

local function lspc_handle_completion_method_response(win, result, old_pos)
  if not result or type(result) ~= 'table' or not result.items then
    lspc:warn('no completion available')
    return
  end

  local completions = result
  if result.isIncomplete ~= nil then
    completions = result.items
  end

  local choices = {}
  for _, completion in ipairs(completions) do
    table.insert(choices, completion.label)
    choices[completion.label] = completion
  end

  -- select a completion
  local choice = lspc_select(choices)
  if not choice then
    return
  end

  local completion = choices[choice]

  if completion.textEdit then
    vis_apply_textEdit(win, win.file, completion.textEdit)
    return
  end

  if completion.insertText or completion.label then
    -- Does our current state correspont to the state when the completion method
    -- was called.
    -- Otherwise we don't have a good way to apply the 'insertText' completion
    if win.selection.pos ~= old_pos then
      lspc:warn('can not apply textInsert because the cursor position changed')
    end

    local new_word = completion.insertText or completion.label
    local old_word_range = win.file:text_object_word(old_pos)
    local old_word = win.file:content(old_word_range)

    lspc:log(string.format('Completion old_pos=%d, old_range={start=%d, finish=%d}, old_word=%s',
                           old_pos, old_word_range.start, old_word_range.finish,
                           old_word:gsub('\n', '\\n')))

    -- update old_word_range and old_word and return if old_word is a prefix of the completion
    local function does_completion_apply_to_pos(pos)
      old_word_range = win.file:text_object_word(pos)
      old_word = win.file:content(old_word_range)

      local is_prefix = new_word:sub(1, string.len(old_word)) == old_word
      return is_prefix
    end

    -- search for a possible completion token which we should replace with this insertText
    local matches = does_completion_apply_to_pos(old_pos)
    if not matches then
      lspc:log('Cursor looks like its not on the completion token')

      -- try the common case the cursor is behind its completion token: fooba┃
      local next_pos_candidate = old_pos - 1
      matches = does_completion_apply_to_pos(next_pos_candidate)
      if matches then
        old_pos = next_pos_candidate
      end
    end

    local completion_start
    -- we found a completion token -> replace it
    if matches then
      lspc:log('replace the token: ' .. old_word .. '  we found being a prefix of the completion')
      win.file:delete(old_word_range)
      completion_start = old_word_range.start
    else
      completion_start = old_pos
    end
    -- apply insertText
    win.file:insert(completion_start, new_word)
    win.selection.pos = completion_start + string.len(new_word)
    win:draw()
    return
  end

  -- neither insertText nor textEdit where present
  lspc:err('Unsupported completion')
end

local function lspc_handle_hover_method_response(win, result, old_pos)
  if not result or type(result) ~= 'table' or not result.contents then
    lspc:warn('no hover available')
    return
  end

  local sel = util.vis_pos_to_sel(win, old_pos)

  local hover_header =
      '--- hover: ' .. (win.file.path or '') .. ': ' .. sel.line .. ', ' .. sel.col .. ' ---\n'
  local hover_msg = ''
  -- The most common markup kind in LSP is markdown
  local markup_kind = 'markdown'

  -- result is MarkedString[]
  if type(result.contents) == 'table' and #result.contents > 0 then
    lspc:log('hover returned list of length ' .. #result.contents)

    for i, marked_string in ipairs(result.contents) do
      if i == 1 then
        hover_msg = marked_string.value or marked_string
      else
        hover_msg = hover_msg .. '\n---\n' .. (marked_string.value or marked_string)
      end
    end
  else -- result is either MarkedString or MarkupContent
    hover_msg = result.contents.value or result.contents
    if result.contents.kind and result.contents.kind == 'plaintext' then
      markup_kind = 'text'
    end
  end
  lspc_show_message(hover_msg, hover_header, markup_kind)
end

local function lspc_handle_signature_help_method_response(win, result, call_pos)
  if not result or type(result) ~= 'table' or not result.signatures or #result.signatures == 0 then
    lspc:warn('no signature help available')
    return
  end

  local signatures = result.signatures

  local sel = util.vis_pos_to_sel(win, call_pos)
  local help_header = '--- signature help: ' .. (win.file.path or '') .. ': ' .. sel.line .. ', ' ..
                          sel.col .. ' ---\n'

  -- local help_msg = lspc.json.encode(result)
  local help_msg = ''
  for _, signature in ipairs(signatures) do
    local sig_msg = signature.label
    if signature.documentation then
      local doc = signature.documentation.value or signature.documentation
      sig_msg = sig_msg .. '\n\tdocumentation: ' .. doc
    end
    help_msg = help_msg .. '\n' .. sig_msg
  end
  -- strip first new line from the message
  help_msg = help_msg:sub(2)
  lspc_show_message(help_msg, help_header)
end

local function lspc_handle_rename_method_response(win, result)
  -- result must always be valid because otherwise we would caught the error
  -- in LanguageServer:handle_method_response
  vis_apply_workspaceEdit(win, win.file, result)
end

local function lspc_handle_formatting_method_response(win, result)
  -- The result of textDocument/formatting is defined as TextEdit[] | null
  if result then
    vis_apply_textEdits(win, win.file, result)
  end
end

local lspc_handle_publish_diagnostics

local function lspc_handle_diagnostic_method_response(ls, result, ctx)
  if result then
    lspc_handle_publish_diagnostics(ls, ctx.uri, result.items)
  end
end

local function lspc_handle_initialize_response(ls, result)
  ls.initialized = true
  ls.capabilities = result.capabilities

  local params = {}
  setmetatable(params, {__jsontype = 'object'})
  ls:send_notification('initialized', params)

  -- According to nvim-lspconfig sendig the lsp server settings shortly after
  -- initialization is an undocumented convention.
  -- See https://github.com/neovim/nvim-lspconfig/blob/ed88435764d8b00442e66d39ec3d9c360e560783/CONTRIBUTING.md
  lspc:log('Loading settings for ' .. ls.name)
  ls:send_default_settings()

  vis.events.emit(lspc.events.LS_INITIALIZED, ls)
end

local function lspc_handle_symbol_method_response(result, ctx)
  if ctx.callback and type(ctx.callback) == 'function' then
    ctx.callback(result, ctx)
  end
end

--- Send didChangeConfiguration notification with the default settings
function LanguageServer:send_default_settings()
  -- Use the rootUri or the open file's path as scope for the initial settings
  local scope = self.rootUri or vis.win.file and vis.win.file.path
  local effective_ls_settings = settings.effective_settings(self, nil, scope)
  if next(effective_ls_settings) then
    self:send_notification('workspace/didChangeConfiguration', {
      settings = effective_ls_settings,
    })
  end
end

--- Dispatch method response from the server
-- @param method_response the response send from the server
-- @param req the request causing this response
function LanguageServer:handle_method_response(method_response, req)
  local win = req.win

  local method = req.method

  local err = method_response.error
  if err then
    local err_msg = err.message
    local err_code = err.code
    lspc:err(err_msg .. ' (' .. err_code .. ') occurred during ' .. method)
    -- Don't try to handle error responses any further
    return
  end

  local result = method_response.result

  -- LuaFormatter off
  if method == 'textDocument/definition' or
     method == 'textDocument/declaration' or
     method == 'textDocument/typeDefinition' or
     method == 'textDocument/implementation' or
     method == 'textDocument/references' then
    -- LuaFormatter on
    lspc_handle_goto_method_response(req, result)

  elseif method == 'initialize' then
    lspc_handle_initialize_response(self, result)

  elseif method == 'textDocument/completion' then
    lspc_handle_completion_method_response(win, result, req.ctx)

  elseif method == 'textDocument/hover' then
    lspc_handle_hover_method_response(win, result, req.ctx)

  elseif method == 'textDocument/signatureHelp' then
    lspc_handle_signature_help_method_response(win, result, req.ctx)

  elseif method == 'textDocument/rename' then
    lspc_handle_rename_method_response(win, result)

  elseif method == 'textDocument/formatting' then
    lspc_handle_formatting_method_response(win, result)

  elseif method == 'textDocument/diagnostic' then
    lspc_handle_diagnostic_method_response(self, result, req.ctx)

  elseif method == 'textDocument/documentSymbol' then
    lspc_handle_symbol_method_response(result, req.ctx)

  elseif method == 'shutdown' then
    self:send_notification('exit')
    self.fd:close()

    -- remove the ls from lspc.running
    for ls_name, rls in pairs(lspc.running) do
      if self == rls then
        lspc.running[ls_name] = nil
        break
      end
    end
  else
    lspc:warn('received unknown method ' .. method)
  end

  self.inflight[method_response.id] = nil
end

--- Handle a workspace/configuration request from a server
-- @param params the parameters send with the request
-- @param response the response we are about to send
local function lspc_handle_workspace_configuration_call(ls, params, response)
  local results = {}
  for _, item in ipairs(params.items) do
    local scope = item.scopeUri and uri_to_path(item.scopeUri)
    local effective_settings = settings.effective_settings(ls, item.section, scope)
    -- If we can not provide any settings LSP requires that null is present in the result array.
    if next(effective_settings) then
      table.insert(results, effective_settings)
    else
      table.insert(results, nil)
    end
  end
  response.result = results
end

--- Handle a method call from the server
-- @param method_call the received method call
function LanguageServer:handle_method_call(method_call)
  local method = method_call.method
  local response = {id = method_call.id}
  if method == 'workspace/configuration' then
    lspc_handle_workspace_configuration_call(self, method_call.params, response)
  else
    lspc:log('Unknown method call ' .. method)
    response['error'] = {
      code = jsonrpc.error_codes.MethodNotFound,
      message = method .. ' not implemented',
    }
  end
  self:rpc(response)
end

-- save the diagnostics received for a file uri
lspc_handle_publish_diagnostics = function(ls, uri, diagnostics)
  local file_path = uri_to_path(uri)
  local file = lspc.open_files[file_path]
  if file then
    for _, diagnostic in ipairs(diagnostics) do
      -- We convert the lsp_range to a vis_range here to do it only once.
      -- It's an expensive operation that involves counting all newlines.
      diagnostic.vis_range = lsp_range_to_vis_range(file.file, diagnostic.range)

      -- In some instances the range defined by the diagnostic starts
      -- and ends at the same position. Highlight the exact position.
      if diagnostic.vis_range.finish == diagnostic.vis_range.start then
        -- We fake a one char range to retrieve its content.
        -- In highlight_diagnostics we inconditionally decrement finish anyway.
        diagnostic.vis_range.finish = diagnostic.vis_range.finish + 1
      end

      -- Remember the content of the diagnostic to only highlight it if the content
      -- did not change
      diagnostic.content = vis.win.file:content(diagnostic.vis_range)
    end

    file.diagnostics[ls] = diagnostics

    lspc:log('remembered ' .. #diagnostics .. ' diagnostics for ' .. file_path)
  else
    lspc:log('Diagnostics for not opened file' .. file_path)
  end
end

local lsp_message_types = {'Error', 'Warning', 'Info', 'Log'}
-- show a message from the server in the UI
local function lspc_handle_show_message(show_message_params)
  if show_message_params.type > lspc.message_level then
    return
  end

  vis:message('--- language server message ---')
  local level = lsp_message_types[show_message_params.type] or 'Unknown'
  vis:message(level .. ': ' .. show_message_params.message)
end

--- Handle a notification received from the server
-- @param notification the received notification
function LanguageServer:handle_notification(notification)
  local method = notification.method
  if method == 'textDocument/publishDiagnostics' then
    lspc_handle_publish_diagnostics(self, notification.params.uri, notification.params.diagnostics)
  elseif method == 'window/showMessage' then
    lspc_handle_show_message(notification.params)
  end
end

--- Dispatch between a method call and a message response
-- Those are distinquiable because for a message response we have a req
-- remembered in the inflight table
-- @param method the method message received from the server
function LanguageServer:handle_method(method)
  local req = self.inflight[method.id]
  if req and not method.method then
    self:handle_method_response(method, req)
  else
    self:handle_method_call(method)
  end
end

--- Dispatch between a method call/response and a notification from the server
-- @param msg the message received from the server
function LanguageServer:handle_msg(msg)
  if msg.id then
    self:handle_method(msg)
  else
    self:handle_notification(msg)
  end
end

-- Parse the data send by the language server
-- Note the chunks received may not end with the end of a message.
-- In the worst case a data chunk contains two partial messages on at the beginning
-- and one at the end
function LanguageServer:recv_data(data)
  local err = self.parser:add(data)
  if err then
    lspc:err(err)
    return
  end

  local msgs = self.parser:get_msgs()
  if not msgs then
    return
  end

  for _, msg in ipairs(msgs) do
    local resp = lspc.json.decode(msg)
    self:handle_msg(resp)
  end
end

--- Return a running language server
-- @param win the window for which the language server might be running
-- @param explicit_syntax the syntax if different from win.syntax
-- @return a running language server or nil and an error message
function lspc.get_running_ls(win, explicit_syntax)
  local ls
  local syntax = explicit_syntax or (win and win.syntax)
  -- try to use the first language server managing the current file
  if not syntax then
    if win and win.file and lspc.open_files[win.file.path] and
        next(lspc.open_files[win.file.path].language_servers) then
      ls = next(lspc.open_files[win.file.path].language_servers)

    else -- there is no language server with this file open and we have no syntax to guess
      return nil, 'No syntax provided and no server is running'
    end

  else -- Use the syntax to guess the language server
    local ls_name, err = get_ls_name_for_syntax(syntax)
    if err then
      return nil, err
    end

    ls = lspc.running[ls_name]
    if not ls then
      return nil, 'No language server running for ' .. syntax
    end
  end

  return ls
end

--- Return a running and initialized language server
-- @param win the window for which the language server might be running
-- @param explicit_syntax the syntax if different from win.syntax
-- @return a running and initialized language server or nil and an error message
local function lspc_get_usable_ls(win, explicit_syntax)
  local ls, err = lspc.get_running_ls(win, explicit_syntax)

  if err then
    return nil, err
  end

  assert(ls)
  if not ls.initialized then
    return nil, 'Language server ' .. ls.name .. ' not initialized yet. Please try again'
  end

  return ls
end

local function lspc_new_file_handle(file)
  return {file = file, version = 0, diagnostics = {}, language_servers = {}}
end

--- Detect if a file is already opened by the language server
-- @param file the vis file object to check
-- @return true if the file is already opened by the language server
function LanguageServer:is_file_opened(file)
  return lspc.open_files[file.path] and lspc.open_files[file.path].language_servers[self]
end

-- close the file if associated with the language server
local function lspc_close(ls, file)
  if not ls:is_file_opened(file) then
    return (file.path or '[No Name]') .. ' not open in ' .. ls.name
  end
  ls:send_notification('textDocument/didClose', {
    textDocument = {uri = path_to_uri(file.path)},
  })
  lspc.open_files[file.path].language_servers[ls] = nil
  if not next(lspc.open_files[file.path].language_servers) then
    lspc.open_files[file.path] = nil
  end
end

-- register a file as open with a language server and setup close and save event handlers
-- A file must be opened before any textDocument functions can be used with it.
local function lspc_open(ls, win, file)
  -- already opened
  if ls:is_file_opened(file) then
    return file.path .. ' already open in ' .. ls.name
  end

  local lspc_file_handle = lspc.open_files[file.path] or lspc_new_file_handle(file)
  lspc_file_handle.language_servers[ls] = true
  lspc.open_files[file.path] = lspc_file_handle

  local params = {
    textDocument = {
      uri = 'file://' .. file.path,
      languageId = syntax_to_languageId(win.syntax),
      version = 0,
      text = file:content(0, file.size),
    },
  }

  ls:send_notification('textDocument/didOpen', params)

  vis.events.emit(lspc.events.LS_DID_OPEN, ls, file)
end

--- Initiate the shutdown of the language server
-- Sending the exit notification and closing the file handle are done in
-- the shutdown response handler.
function LanguageServer:shutdown()
  self:call_method('shutdown')
end

--- Find the root project URI for a specific file
-- @param ls the language server
-- @param file_path the path to the file to find the root project of
-- @return the URI of the root project or nil if none was found
local function find_root_uri(ls, file_path)
  local globs = ''

  local roots = ls.roots
  if roots then
    for _, glob in ipairs(roots) do
      globs = globs .. glob .. '\n'
    end
  end

  if lspc.universal_root_globs then
    for _, glob in ipairs(lspc.universal_root_globs) do
      globs = globs .. glob .. '\n'
    end
  end

  local root_path = util.find_upwards(globs, file_path)
  if not root_path and lspc.fallback_dirname_as_root then
    root_path = util.dirname(file_path)
  end
  return root_path and path_to_uri(root_path)
end

local function ls_start(ls, init_options)
  ls.fd = vis:communicate(ls.name, 'exec ' .. ls.conf.cmd)

  -- detect the workspace root
  ls.rootUri = vis.win.file and find_root_uri(ls, vis.win.file.path)

  -- register the response handler
  vis.events.subscribe(vis.events.PROCESS_RESPONSE, function(name, event, code, msg)
    if name ~= ls.name then
      return
    end

    if event == 'EXIT' or event == 'SIGNAL' then
      if event == 'EXIT' then
        vis:info('language server exited with: ' .. code)
      else
        vis:info('language server received signal: ' .. code)
      end

      lspc.running[ls.name] = nil
      return
    end

    lspc:log(ls.name .. ' response(' .. event .. '): ' .. msg)
    if event == 'STDERR' then
      return
    end

    ls:recv_data(msg)
  end)

  local params = {
    processId = vis_pid,
    clientInfo = {name = lspc.name, version = lspc.version},
    rootUri = ls.rootUri or lspc.json.null,
    capabilities = lspc.client_capabilites,
  }

  if init_options then
    params.initializationOptions = init_options
  end

  ls:call_method('initialize', params)
end

function LanguageServer.new(ls_conf)
  local ls = {
    name = ls_conf.name,
    conf = ls_conf,

    initialized = false,
    id = 0,
    inflight = {},
    parser = parser.new(),
    capabilities = {},
  }
  setmetatable(ls, {__index = LanguageServer})

  return ls
end

local function lspc_start_server(syntax)
  local ls_conf = lspc.ls_map[syntax]
  if not ls_conf then
    return nil, 'No language server available for ' .. syntax
  end

  local exe = ls_conf.cmd:gmatch('%S+')()
  if not os.execute('type ' .. exe .. '>/dev/null 2>/dev/null') then
    -- remove the configured language server
    lspc.ls_map[syntax] = nil
    local msg = string.format('Language server for %s configured but %s not found', syntax, exe)
    -- the warning will be visual if the language server was automatically startet
    -- if the user tried to start teh server manually they will see msg as error
    lspc:warn(msg)
    return nil, msg
  end

  if lspc.running[ls_conf.name] then
    return nil, 'Already a language server running for ' .. syntax
  end

  local ls = LanguageServer.new(ls_conf)
  lspc.running[ls_conf.name] = ls
  ls_start(ls, ls_conf.init_options)

  return ls
end

-- generic stub implementation for all textDocument methods taking
-- a textDocumentPositionParams parameter
local function lspc_method_doc_pos(ls, method, win, argv, additional_params)
  -- check if the language server has a provider for this method
  if not ls.capabilities[method .. 'Provider'] then
    return 'language server ' .. ls.name .. ' does not provide ' .. method
  end

  if not ls:is_file_opened(win.file) then
    lspc_open(ls, win, win.file)
  end

  local params = vis_doc_pos_to_lsp(vis_get_doc_pos(win))
  if additional_params then
    for k, v in pairs(additional_params) do
      params[k] = v
    end
  end

  ls:call_text_document_method(method, params, win, argv)
end

local lspc_goto_location_methods = {
  declaration = function(ls, win, open_cmd)
    return lspc_method_doc_pos(ls, 'declaration', win, open_cmd)
  end,
  definition = function(ls, win, open_cmd)
    return lspc_method_doc_pos(ls, 'definition', win, open_cmd)
  end,
  typeDefinition = function(ls, win, open_cmd)
    return lspc_method_doc_pos(ls, 'typeDefinition', win, open_cmd)
  end,
  implementation = function(ls, win, open_cmd)
    return lspc_method_doc_pos(ls, 'implementation', win, open_cmd)
  end,
  references = function(ls, win, open_cmd)
    return lspc_method_doc_pos(ls, 'references', win, open_cmd,
                               {context = {includeDeclaration = false}})
  end,
}

local function has_diagnostics(file)
  if not file or not file.diagnostics then
    return false
  end

  -- detect if at least one server has published diagnostics
  for _, d in pairs(file.diagnostics) do
    if #d then
      return true
    end
  end

  return false
end

local function lspc_goto_next_diagnostic(win, reverse)
  if not lspc.open_files[win.file.path] then
    vis:command('lspc-open')
  end

  local open_file = lspc.open_files[win.file.path]

  if not has_diagnostics(open_file) then
    return (win.file.path or 'window') .. ' has no available diagnostics'
  end

  -- merge diagnostics
  -- TODO: come up with more efficient algorithm
  local diagnostics = {}
  for _, server_diagnostics in pairs(open_file.diagnostics) do
    for _, diagnostic in ipairs(server_diagnostics) do
      table.insert(diagnostics, diagnostic)
    end
  end
  -- sort the merged diagnostics
  table.sort(diagnostics, function(d1, d2)
    return lsp_range_starts_before(d1.range, d2.range)
  end)

  local sel = get_selection(win)

  local previous_diagnostic
  for _, diagnostic in ipairs(diagnostics) do
    local start = lsp_pos_to_vis_sel(diagnostic.range.start)
    local fin = lsp_pos_to_vis_sel(diagnostic.range['end'])

    -- reverse
    if reverse and
        (start.line > sel.line or
            (start.line == sel.line and (start.col >= sel.col or sel.col <= fin.col))) then

      -- wrap around
      if not previous_diagnostic then
        previous_diagnostic = lsp_pos_to_vis_sel(diagnostics[#diagnostics].range.start)
      end

      win.selection:to(previous_diagnostic.line, previous_diagnostic.col)
      return
    end

    -- forward
    if start.line > sel.line or (start.line == sel.line and start.col > sel.col) then
      win.selection:to(start.line, start.col)
      return
    end

    previous_diagnostic = start
  end

  -- wrap around
  if #diagnostics > 0 then
    local first = lsp_pos_to_vis_sel(diagnostics[1].range.start)
    win.selection:to(first.line, first.col)
  end
end

local function lspc_show_diagnostic(win, line)
  if not lspc.open_files[win.file.path] then
    vis:command('lspc-open')
  end
  local file = lspc.open_files[win.file.path]

  if not has_diagnostics(file) then
    return win.file.path .. ' has no diagnostics available'
  end
  local diagnostics = file.diagnostics

  line = line or get_selection(win).line
  lspc:log('Show diagnostics for ' .. line)
  local diagnostics_to_show = {}
  for ls, server_diagnostics in pairs(diagnostics) do
    for _, diagnostic in ipairs(server_diagnostics) do
      local start = lsp_pos_to_vis_sel(diagnostic.range.start)
      if start.line == line then
        diagnostic.start = start
        diagnostic.server = ls.name
        table.insert(diagnostics_to_show, diagnostic)
      end
    end
  end

  local diagnostics_fmt = '%s: %d:%d %s:%s\n'
  local diagnostics_msg = ''
  for _, diagnostic in ipairs(diagnostics_to_show) do
    diagnostics_msg = diagnostics_msg ..
                          string.format(diagnostics_fmt, diagnostic.server, diagnostic.start.line,
                                        diagnostic.start.col, diagnostic.code or 'diagnostic',
                                        diagnostic.message)
  end

  if diagnostics_msg ~= '' then
    lspc_show_message(diagnostics_msg)
  else
    lspc:warn('No diagnostics available for line: ' .. line)
  end
end

local lsp_symbol_kinds = {
  'File',
  'Module',
  'Namespace',
  'Package',
  'Class',
  'Method',
  'Property',
  'Field',
  'Constructor',
  'Enum',
  'Interface',
  'Function',
  'Variable',
  'Constant',
  'String',
  'Number',
  'Boolean',
  'Array',
  'Object',
  'Key',
  'Null',
  'EnumMember',
  'Struct',
  'Event',
  'Operator',
  'TypeParameter',
}

local function recursive_bfs_symbols_flatten(symbols, indent)
  local ranges = {}
  local str = ''
  for _, s in ipairs(symbols) do
    local range = s.selectionRange or s.location.range
    table.insert(ranges, range)
    str = str .. string.format(lspc.navwin_symbol_format, indent, lsp_symbol_kinds[s.kind], s.name,
                               range.start.line + 1, range.start.character + 1)
    -- Remember DocumentSymbol.selectionRange or SymbolInformation.location.range
    if s.children then
      local cstr, cranges = recursive_bfs_symbols_flatten(s.children, indent .. '  ')
      str = str .. cstr
      for _, v in ipairs(cranges) do
        table.insert(ranges, v)
      end
    end
  end
  return str, ranges
end

--- Scroll the code window to the definition of the symbol selected in the navigation window.
local function navwin_scroll_codewin(self, switch_win)
  local line = self.navwin.selection.line
  -- No valid selection in the navigation window
  if line > #self.ranges then
    return
  end
  local sel = lsp_pos_to_vis_sel(self.ranges[line].start)

  -- Set the selection in the code window to the selected symbol
  self.codewin.selection:to(sel.line, sel.col)

  if switch_win then
    vis.win = self.codewin
  end
end

--- Instantiate a new navigation context from the received symbols.
local function lspc_navwin_from_symbols(symbols, ctx)
  local symbols_outline, ranges = recursive_bfs_symbols_flatten(symbols, '')

  local old_layout = vis.ui.layout
  if lspc.navwin_layout:sub(1, 1) == 'v' then
    vis.ui.layout = vis.ui.layouts.VERTICAL
  elseif lspc.navwin_layout:sub(1, 1) == 'h' then
    vis.ui.layout = vis.ui.layouts.HORIZONTAL
  end

  local navwin
  local codewin
  -- The right or bottom (old) window is our navigation window
  if lspc.navwin_layout:sub(2) == 'r' or lspc.navwin_layout:sub(2) == 'b' then
    vis:command('o ' .. ctx.win.file.path)
    navwin = ctx.win
    navwin.file = ''
    navwin.file:delete(0, navwin.file.size)
    codewin = vis.win
    -- The new (old) window is our navigation window
  else
    vis:command('o')
    navwin = vis.win
    codewin = ctx.win
  end

  -- Remove syntax highlighting from the symbols
  navwin:set_syntax(nil)

  assert(navwin)
  assert(codewin)
  ctx = {
    navwin = navwin,
    codewin = codewin,
    ranges = ranges,
    old_layout = old_layout,
  }

  lspc.navwins[navwin] = ctx
  lspc.navwins[codewin] = ctx

  -- Prepare window to be our symbol navigation window
  navwin.file:insert(0, symbols_outline)
  navwin:draw()

  navwin:map(vis.modes.NORMAL, '<Enter>', function()
    navwin_scroll_codewin(ctx, true)
  end, 'jump to the selected symbol')
  navwin:map(vis.modes.NORMAL, 'p', function()
    navwin_scroll_codewin(ctx, false)
  end, 'scroll to the selected symbol')
  navwin:map(vis.modes.NORMAL, 'q', function()
    navwin:close(true)
  end, 'close this window')

  -- Jump to navigation window
  vis.win = navwin

  -- Remove the event handlers.
  local nav_win_close_handler
  nav_win_close_handler = function(win)
    -- Not our windows
    if win ~= navwin and win ~= codewin then
      return true
      -- The code windows was closed, therefore we can also close the navigation window
    elseif win == codewin then
      lspc:log('Code window closed. Force close the navigation window.')
      navwin:close(true)
      return
    end
    -- reset vis' layout
    vis.ui.layout = lspc.navwins[codewin].old_layout

    -- remove the navigation window
    lspc.navwins[navwin] = nil
    lspc.navwins[codewin] = nil
    lspc:log('unsubscribe navwin event handler')
    vis.events.unsubscribe(vis.events.WIN_CLOSE, nav_win_close_handler)
    return true
  end

  vis.events.subscribe(vis.events.WIN_CLOSE, nav_win_close_handler)
end

local function lspc_nav_symbols(ls, win)
  local ctx = {win = win, callback = lspc_navwin_from_symbols}
  ls:request_symbols(win, ctx)
end

-- vis-lspc commands

vis:command_register('lspc-back', function()
  local err = vis_pop_doc_pos()
  if err then
    lspc:err(err)
  end
end)

for name, func in pairs(lspc_goto_location_methods) do
  vis:command_register('lspc-' .. name, function(argv, _, win)
    local ls, err = lspc_get_usable_ls(win, argv[1])
    if err then
      lspc:err(err)
      return
    end
    assert(ls)

    -- vis cmd how to open the new location
    -- 'e' (default): in same window
    -- 'vsplit': in a vertical split window
    -- 'hsplit': in a horizontal split window
    local open_cmd = argv[1] or 'e'
    err = func(ls, win, open_cmd)
    if err then
      lspc:err(err)
    end
  end)
end

vis:command_register('lspc-hover', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- remember the position where hover was called
  err = lspc_method_doc_pos(ls, 'hover', win, win.selection.pos)
  if err then
    lspc:err(err)
  end
end)

vis:command_register('lspc-signature-help', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- remember the position where signatureHelp was called
  err = lspc_method_doc_pos(ls, 'signatureHelp', win, win.selection.pos)
  if err then
    lspc:err(err)
  end
end)

vis:command_register('lspc-rename', function(argv, _, win)
  local new_name = argv[1]
  if not new_name then
    lspc:err('lspc-rename usage: <new name> [syntax]')
    return
  end

  local ls, err = lspc_get_usable_ls(win, argv[2])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- check if the language server has a provider for this method
  if not ls.capabilities['renameProvider'] then
    lspc:err('language server ' .. ls.name .. ' does not provide rename')
    return
  end

  if not ls:is_file_opened(win.file.path) then
    lspc_open(ls, win, win.file)
  end

  local params = vis_doc_pos_to_lsp(vis_get_doc_pos(win))
  params.newName = new_name

  ls:call_text_document_method('rename', params, win)
end)

vis:command_register('lspc-format', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- check if the language server has a provider for this method
  if not ls.capabilities['documentFormattingProvider'] then
    lspc:err('language server ' .. ls.name .. ' does not provide formatting')
    return
  end

  if not lspc.open_files[win.file.path] then
    lspc_open(ls, win, win.file)
  end

  local params = {
    textDocument = {uri = path_to_uri(win.file.path)},
    options = ls.conf.formatting_options,
  }
  if params.options == nil then
    params.options = {
      tabSize = win.options.tabwidth,
      insertSpaces = win.options.expandtab,
    }
  end

  ls:call_text_document_method('formatting', params, win)
end)

vis:command_register('lspc-diagnostic', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- check if the language server has a provider for this method
  if not ls.capabilities['diagnosticProvider'] then
    lspc:err('language server ' .. ls.name .. ' does not provide document diagnostics')
    return
  end

  if not lspc.open_files[win.file.path] then
    lspc_open(ls, win, win.file)
  end

  ls:request_diagnostics(win)
end)

vis:command_register('lspc-completion', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  -- remember the position where completions were requested
  -- to apply insertText completions
  err = lspc_method_doc_pos(ls, 'completion', win, win.selection.pos)
  if err then
    lspc:err(err)
  end
end)

vis:command_register('lspc-start-server', function(argv, _, win)
  local syntax = argv[1] or win.syntax
  if not syntax then
    lspc:err('no language specified')
  end

  local _, err = lspc_start_server(syntax)
  if err then
    lspc:err(err)
  end
end)

vis:command_register('lspc-shutdown-server', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err('no language server running: ' .. err)
    return
  end
  assert(ls)

  ls:shutdown()
end)

vis:command_register('lspc-close', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  lspc_close(ls, win.file)
end)

vis:command_register('lspc-open', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)

  lspc_open(ls, win, win.file)
end)

local function _lspc_next_diagnostic(win, reverse)
  local err = lspc_goto_next_diagnostic(win, reverse)
  if err then
    lspc:err(err)
  end
end

vis:command_register('lspc-next-diagnostic', function(_, _, win)
  _lspc_next_diagnostic(win, false)
end)

vis:command_register('lspc-prev-diagnostic', function(_, _, win)
  _lspc_next_diagnostic(win, true)
end)

vis:command_register('lspc-show-diagnostics', function(argv, _, win)
  local err = lspc_show_diagnostic(win, argv[1])
  if err then
    lspc:err(err)
  end
end)

vis:command_register('lspc-navigate-symbols', function(argv, _, win)
  local ls, err = lspc_get_usable_ls(win, argv[1])
  if err then
    lspc:err(err)
    return
  end
  assert(ls)
  if not ls:is_file_opened(win.file.path) then
    lspc_open(ls, win, win.file)
  end
  if lspc.navwins[win] then
    lspc.navwins[win].navwin:close(true)
  else
    lspc_nav_symbols(ls, win)
  end
end, 'toggle the symbol navigation')

vis:command_register('lspc-navwin-jump', function(_, _, win)
  local navwin = lspc.navwins[win]
  if not navwin then
    lspc:err('no associated navigation window')
  else
    navwin_scroll_codewin(navwin, true)
  end
end, 'jump to the selected symbol')

vis:command_register('lspc-navwin-scroll', function(_, _, win)
  local navwin = lspc.navwins[win]
  if not navwin then
    lspc:err('no associated navigation window')
  else
    navwin_scroll_codewin(navwin, false)
  end
end, 'scroll the code window to the selected symbol')

vis:command_register('lspc-navwin-close', function(_, _, win)
  local navwin = lspc.navwins[win]
  if not navwin then
    lspc:err('no associated navigation window')
  else
    navwin.navwin:close(true)
  end
end, 'close the navigation window')

-- vis-lspc event hooks
vis.events.subscribe(vis.events.WIN_OPEN, function(win)
  if lspc.autostart and win.syntax then
    lspc_start_server(win.syntax)
  end
end)

local function highlight_event()
  local win = vis.win
  if not win or not win.file then
    return
  end

  local open_file = lspc.open_files[win.file.path]
  if open_file and open_file.diagnostics and lspc.highlight_diagnostics then
    lspc_highlight_diagnostics(win, open_file.diagnostics)
  end
end

vis.events.subscribe(vis.events.WIN_HIGHLIGHT, highlight_event)
vis.events.subscribe(vis.events.UI_DRAW, highlight_event)

vis.events.subscribe(vis.events.FILE_OPEN, function(file)
  local win = vis.win
  -- the only window we can access is not our window
  if not win or win.file ~= file then
    return
  end

  local ls = lspc_get_usable_ls(win)
  if not ls then
    return
  end

  lspc_open(ls, win, file)
end)

vis.events.subscribe(vis.events.FILE_SAVE_POST, function(file, path)
  if not vis.win or vis.win.file ~= file then
    return
  end

  local file_handle = lspc.open_files[path]
  if not file_handle then
    return
  end

  for ls in pairs(file_handle.language_servers) do
    ls:send_did_change(file)
    -- the server is interested in didSave notifications
    if ls.capabilities.textDocumentSync and type(ls.capabilities.textDocumentSync) == 'table' and
        ls.capabilities.textDocumentSync.save then
      local did_save_params = {textDocument = {uri = path_to_uri(file.path)}}
      ls:send_notification('textDocument/didSave', did_save_params)
    end
    ls:request_diagnostics(vis.win)
  end
end)

vis.events.subscribe(vis.events.FILE_CLOSE, function(closed_file)
  local file_handle = lspc.open_files[closed_file.path]
  if not file_handle then
    return
  end

  for ls in pairs(file_handle.language_servers) do
    lspc_close(ls, closed_file)
  end
end)

vis.events.subscribe(lspc.events.LS_INITIALIZED, function(ls)
  if vis.win and vis.win.file and lspc_get_usable_ls(vis.win) == ls then
    lspc_open(ls, vis.win, vis.win.file)
  end
end)

vis.events.subscribe(vis.events.QUIT, function()
  for _, ls in pairs(lspc.running) do
    -- attempt to gracefully shutdown the language server
    ls:shutdown()
    -- close the fd handle to terminate the subprocess because
    -- a potential method response from the server will not be read after the
    -- QUIT event
    ls.fd:close()
  end
end)

vis:option_register('lspc-highlight-diagnostics', 'string', function(value)
  lspc.highlight_diagnostics = value
  return true
end, 'How should lspc highlight available diagnostics')

vis:option_register('lspc-menu-cmd', 'string', function(value)
  lspc.menu_cmd = value
  return true
end, 'External tool vis-lspc uses to present choices in a menu')

vis:option_register('lspc-confirm-cmd', 'string', function(value)
  lspc.confirm_cmd = value
  return true
end, 'External tool vis-lspc uses to ask the user for confirmation')

vis:option_register('lspc-message-level', 'number', function(value)
  lspc.message_level = value
  return true
end, 'Message level to show in UI (for server messages)')

vis:option_register('lspc-diagnostic-style-error', 'string', function(value)
  lspc.diagnostic_styles.error = value
end, 'Style for diagnostic errors')

vis:option_register('lspc-diagnostic-style-warning', 'string', function(value)
  lspc.diagnostic_styles.warning = value
end, 'Style for diagnostic warnings')

vis:option_register('lspc-diagnostic-style-information', 'string', function(value)
  lspc.diagnostic_styles.information = value
end, 'Style for diagnostic information')

vis:option_register('lspc-diagnostic-style-hint', 'string', function(value)
  lspc.diagnostic_styles.hint = value
end, 'Style for diagnostic hints')

dofile(source_path .. 'bindings.lua')
return lspc