-- Copyright 2007-2013 Mitchell mitchell.att.foicica.com. See LICENSE.

local M = {}

--[[ This comment is for LuaDoc.
---
-- Handles file type detection for Textadept.
-- @field _G.events.LANGUAGE_MODULE_LOADED (string)
--   Emitted after loading a language-specific module.
--   This is useful for overriding a language-specific module's key bindings
--   or other properties since the module is not loaded when Textadept starts.
--   Arguments:
--
--   * *`lang`*: The language lexer name.
module('_M.textadept.mime_types')]]

-- Events.
local events, events_connect = events, events.connect
events.LANGUAGE_MODULE_LOADED = 'language_module_loaded'

---
-- Map of file extensions (excluding the leading '.') to their associated
-- lexers.
-- If the file type is not recognized by shebang words or first-line patterns,
-- each file extension is matched against the file's extension.
-- @class table
-- @name extensions
M.extensions = {}

---
-- Map of shebang words to their associated lexers.
-- If the file has a shebang line, a line that starts with "#!" and is the first
-- line in the file, each shebang word is matched against that line.
-- @class table
-- @name shebangs
M.shebangs = {}

---
-- Map of first-line patterns to their associated lexers.
-- If a file type is not recognized by shebang words, each pattern is matched
-- against the first line in the file.
-- @class table
-- @name patterns
M.patterns = {}

-- Load mime-types from *modules/textadept/mime_types.conf*.
local mime_types
local f = io.open(_HOME..'/modules/textadept/mime_types.conf', 'rb')
if f then
  mime_types = f:read('*all')
  f:close()
end
f = io.open(_USERHOME..'/mime_types.conf', 'rb')
if f then
  mime_types = mime_types..'\n'..f:read('*all')
  f:close()
end
for line in mime_types:gmatch('[^\r\n]+') do
  if not line:find('^%s*%%') then
    if line:find('^%s*[^#/]') then -- extension definition
      local ext, lexer_name = line:match('^%s*(.+)%s+(%S+)$')
      if ext and lexer_name then M.extensions[ext] = lexer_name end
    else -- shebang or pattern
      local ch, text, lexer_name = line:match('^%s*([#/])(.+)%s+(%S+)$')
      if ch and text and lexer_name then
        (ch == '#' and M.shebangs or M.patterns)[text] = lexer_name
      end
    end
  end
end

---
-- List of lexers found in `_LEXERPATH`.
-- @class table
-- @name lexers
M.lexers = {}

-- Generate lexer list
local lexers_found = {}
for dir in _LEXERPATH:gsub('[/\\]%?%.lua', ''):gmatch('[^;]+') do
  if lfs.attributes(dir) then
    for lexer in lfs.dir(dir) do
      if lexer:find('%.lua$') and lexer ~= 'lexer.lua' then
        lexers_found[lexer:match('^(.+)%.lua$')] = true
      end
    end
  end
end
for lexer in pairs(lexers_found) do M.lexers[#M.lexers + 1] = lexer end
table.sort(M.lexers)

---
-- Prompts the user to select a lexer for the current buffer.
-- @see buffer.set_lexer
-- @name select_lexer
function M.select_lexer()
  local lexer = gui.filteredlist(_L['Select Lexer'], _L['Name'], M.lexers)
  if lexer then buffer:set_lexer(lexer) end
end

-- LuaDoc is in core/.buffer.luadoc.
local function get_style_name(buffer, style_num)
  buffer:check_global()
  if style_num < 0 or style_num > 255 then error('0 <= style_num < 256') end
  return buffer:private_lexer_call(style_num)
end

-- Contains the whitespace styles for lexers.
-- These whitespace styles are used to determine the lexer at the caret position
-- since the styles have the name "[lang]_whitespace".
-- @class table
-- @name ws_styles
local ws_styles = {}
local SETDIRECTPOINTER = _SCINTILLA.properties.doc_pointer[2]
local SETLEXERLANGUAGE = _SCINTILLA.properties.lexer_language[2]
-- LuaDoc is in core/.buffer.luadoc.
local function set_lexer(buffer, lang)
  buffer:check_global()
  buffer._lexer = lang
  buffer:private_lexer_call(SETDIRECTPOINTER, buffer.direct_pointer)
  buffer:private_lexer_call(SETLEXERLANGUAGE, lang)
  if package.searchpath(lang, package.path) then
    _M[lang] = require(lang)
    local post_init = lang..'.post_init'
    if package.searchpath(post_init, package.path) then require(post_init) end
    if _M[lang].set_buffer_properties then _M[lang].set_buffer_properties() end
    events.emit(events.LANGUAGE_MODULE_LOADED, lang)
  end
  local last_line = buffer.first_visible_line + buffer.lines_on_screen
  buffer:colourise(0, buffer:position_from_line(last_line + 1))
  -- Create the ws_styles[lexer] lookup table for `get_lexer()`.
  if ws_styles[lang] then return end
  local ws = {}
  for i = 0, 255 do
    ws[i] = buffer:private_lexer_call(i):find('whitespace') ~= nil
  end
  ws_styles[lang] = ws
end

local GETLEXERLANGUAGE = _SCINTILLA.properties.lexer_language[1]
-- LuaDoc is in core/.buffer.luadoc.
local function get_lexer(buffer, current)
  buffer:check_global()
  local lexer = buffer:private_lexer_call(GETLEXERLANGUAGE)
  if not current then return lexer end
  local i, ws, style_at = buffer.current_pos, ws_styles[lexer], buffer.style_at
  if ws then while i > 0 and not ws[style_at[i]] do i = i - 1 end end
  return get_style_name(buffer, style_at[i]):match('^(.+)_whitespace$') or lexer
end

events_connect(events.BUFFER_NEW, function()
  buffer.set_lexer, buffer.get_lexer = set_lexer, get_lexer
  buffer.get_style_name = get_style_name
end, 1)
-- Scintilla's first buffer does not have these.
if not RESETTING then
  buffer.set_lexer, buffer.get_lexer = set_lexer, get_lexer
  buffer.get_style_name = get_style_name
end

-- Performs actions suitable for a new buffer.
-- Sets the buffer's lexer language and loads the language module.
local function handle_new()
  local lexer
  local line = buffer:get_line(0)
  if line:find('^#!') then
    for word in line:gsub('[/\\]', ' '):gmatch('%S+') do
      lexer = M.shebangs[word]
      if lexer then break end
    end
  end
  if not lexer then
    for patt, lex in pairs(M.patterns) do
      if line:find(patt) then lexer = lex break end
    end
  end
  if not lexer and buffer.filename then
    lexer = M.extensions[buffer.filename:match('[^/\\.]+$')]
  end
  buffer:set_lexer(lexer or 'text')
end
events_connect(events.FILE_OPENED, handle_new)
events_connect(events.FILE_SAVED_AS, handle_new)

-- Sets the buffer's lexer based on filename, shebang words, or
-- first line pattern.
local function restore_lexer()
  buffer:private_lexer_call(SETDIRECTPOINTER, buffer.direct_pointer)
  buffer:private_lexer_call(SETLEXERLANGUAGE, buffer._lexer or 'text')
end
events_connect(events.BUFFER_AFTER_SWITCH, restore_lexer)
events_connect(events.VIEW_NEW, restore_lexer, 1)

events_connect(events.RESET_AFTER,
               function() buffer:set_lexer(buffer._lexer or 'text') end)

return M