-- Copyright (c) 2017-2019 Florian Fischer. All rights reserved.
-- Use of this source code is governed by a MIT license found in the LICENSE file.
local spellcheck = {}
if os.getenv('LANG') then
  spellcheck.default_lang = os.getenv('LANG'):sub(0, 5)
else
  spellcheck.default_lang = 'en_US'
end

spellcheck.get_lang = function ()
  if vis.win.file.spell_language then
    return vis.win.file.spell_language
  else
    return spellcheck.default_lang
  end
end

local supress_stdout = ' >/dev/null'
local supress_stderr = ' 2>/dev/null'
local supress_output = supress_stdout .. supress_stderr
if os.execute('type enchant' .. supress_output) then
  spellcheck.cmd = 'enchant -d %s -a'
  spellcheck.list_cmd = 'enchant -l -d %s'
elseif os.execute('type enchant-2' .. supress_output) then
  spellcheck.cmd = 'enchant-2 -d %s -a'
  spellcheck.list_cmd = 'enchant-2 -l -d %s'
elseif os.execute('type aspell' .. supress_output) then
  spellcheck.cmd = 'aspell pipe -l %s'
  spellcheck.list_cmd = 'aspell list -l %s'
elseif os.execute('type hunspell' .. supress_output) then
  spellcheck.cmd = 'hunspell -d %s'
  spellcheck.list_cmd = 'hunspell -l -d %s'
else
  vis:info('WARNING: vis-spellcheck loaded but no spellchecker found')
  return nil
end

spellcheck.typo_style_id = 42
spellcheck.typo_style = 'fore:red'
spellcheck.check_full_viewport = {}
spellcheck.disable_syntax_awareness = false

spellcheck.check_tokens = {
  [vis.lexers.STRING] = true,
  [vis.lexers.COMMENT] = true,
  [vis.lexers.DEFAULT] = true,
}

-- Return nil or a string of misspelled word in a specific file range or text
-- by calling the spellchecker's list command.
-- If given a range we will use vis:pipe to get our typos from the spellchecker.
-- If a string was passed we call the spellchecker ourself and redirect its stdout
-- to a temporary file. See http://lua-users.org/lists/lua-l/2007-10/msg00189.html.
-- The returned string consists of each misspell followed by a newline.
local function get_typos(range_or_text)
  local cmd = spellcheck.list_cmd:format(spellcheck.get_lang())
  local typos
  if type(range_or_text) == 'string' then
    local text = range_or_text
    local tmp_name = os.tmpname()
    local full_cmd = cmd .. '> ' .. tmp_name .. supress_stderr
    local proc = assert(io.popen(full_cmd, 'w'))
    proc:write(text)
    -- this error detection may need lua5.2
    local success, _, exit_code = proc:close()
    if not success then
      vis:info('calling ' .. cmd .. ' failed (' .. exit_code .. ')')
      return nil
    end

    local tmp_file = assert(io.open(tmp_name, 'r'))
    typos = tmp_file:read('*a')
    tmp_file:close()
    os.remove(tmp_name)
  else
    local range = range_or_text
    local ret, so, _ = vis:pipe(vis.win.file, range, cmd)

    if ret ~= 0 then
      vis:info('calling ' .. cmd .. ' failed (' .. ret .. ')')
      return nil
    end
    typos = so
  end

  return typos
end

-- plugin global list of ignored typos
local ignored = {}

-- Return an iterator over all not ignored typos and their positions in text.
-- The returned iterator is a self contained statefull iterator function closure.
-- Which will return the next typo and its start and finish in the text, starting by 1.
local function typo_iter(text, typos, ignored) -- luacheck: ignore ignored
  local index = 1
  local unfiltered_iterator, iter_state = typos:gmatch('(.-)\n')

  -- see https://stackoverflow.com/questions/6705872/how-to-escape-a-variable-in-lua
  local escape_lua_pattern
  do
    local matches = {
      ['^'] = '%^',
      ['$'] = '%$',
      ['('] = '%(',
      [')'] = '%)',
      ['%'] = '%%',
      ['.'] = '%.',
      ['['] = '%[',
      [']'] = '%]',
      ['*'] = '%*',
      ['+'] = '%+',
      ['-'] = '%-',
      ['?'] = '%?',
    }

    escape_lua_pattern = function(s)
      return (s:gsub('.', matches))
    end
  end

  return function()
    local typo
    repeat
      typo = unfiltered_iterator(iter_state)
    until (not typo or (typo ~= '' and not ignored[typo]))

    if typo then
      -- to prevent typos from being found in correct words before them
      -- ("stuff stuf", "broken ok", ...)
      -- we match typos only when they are enclosed in non-letter characters.
      local start, finish = text:find('[%A]' .. escape_lua_pattern(typo) ..
                                          '[%A]', index)
      -- typo was not found by our pattern this means it must be either
      -- the first or last word in the text
      if not start then
        -- check start of text
        start = 1
        finish = #typo
        -- typo is not the beginning must be the end of text
        if text:sub(start, finish) ~= typo then
          start = #text - #typo + 1
          finish = start + #typo - 1
        end

        if text:sub(start, finish) ~= typo then
          vis:info(string.format(
                       'can\'t find typo %s after %d. Please report this bug.',
                       typo, index))
        end
        -- our pettern [%A]typo[%A] found it
      else
        start = start + 1 -- ignore leading non letter char
        finish = finish - 1 -- ignore trailing non letter char
      end
      index = finish

      return typo, start, finish
    end
  end
end

local last_viewport, last_data, last_typos = nil, '', ''

vis.events.subscribe(vis.events.WIN_HIGHLIGHT, function(win)
  if not spellcheck.check_full_viewport[win] or
      not win:style_define(spellcheck.typo_style_id, spellcheck.typo_style) then
    return
  end
  local viewport = win.viewport
  local viewport_text = win.file:content(viewport)

  local typos
  if last_viewport == viewport_text then
    typos = last_typos
  else
    typos = get_typos(viewport) or ''
    if not typos then
      return
    end
  end

  for _, start, finish in typo_iter(viewport_text, typos, ignored) do
    win:style(spellcheck.typo_style_id, viewport.start + start - 1, viewport.start + finish - 1)
  end

  last_viewport = viewport_text
  last_typos = typos
  -- TODO: think about returning true here
  -- http://martanne.github.io/vis/doc/index.html#Events
  -- The vis documentation states that a no further event handlers are called if one
  -- returns not nil
  -- Should we terminate the WIN_HIGHLIGHT event handling if we are ready highltighting
  -- typos ?
  return true
end)

local wrapped_lex_funcs = {}

local wrap_lex_func = function(old_lex_func)
  local old_new_tokens = {}

  return function(lexer, data, index, redrawtime_max)
    local tokens, timedout = old_lex_func(lexer, data, index, redrawtime_max)

    -- quit early if the lexer already took to long
    -- TODO: investigate further if timedout is actually set by the lexer.
    --       As I understand lpeg.match used by lexer.lex timedout will always be nil
    if timedout then
      return tokens, timedout
    end

    local new_tokens = {}

    local typos
    if last_data ~= data then
      typos = get_typos(data)
      if not typos then
        return tokens, timedout
      end
      last_data = data
    else
      return old_new_tokens
    end

    local i = 1
    for _, typo_start, typo_end in typo_iter(data, typos, ignored) do
      repeat
        -- no tokens left
        if i > #tokens - 1 then
          break
        end

        local token_type = tokens[i]
        local token_start = (tokens[i - 1] or 1) - 1
        local token_end = tokens[i + 1]

        -- the current token ends before our typo -> append to new stream
        -- or is not spellchecked
        if token_end < typo_start or not spellcheck.check_tokens[token_type] then
          table.insert(new_tokens, token_type)
          table.insert(new_tokens, token_end)

          -- done with this token -> advance token stream
          i = i + 2
          -- typo and checked token overlap
        else
          local pre_typo_end = typo_start - 1
          -- unchanged token part before typo
          if pre_typo_end > token_start then
            table.insert(new_tokens, token_type)
            table.insert(new_tokens, pre_typo_end + 1)
          end

          -- highlight typo
          table.insert(new_tokens, vis.lexers.ERROR)
          -- the typo spans multiple tokens
          if token_end < typo_end then
            table.insert(new_tokens, token_end + 1)
            i = i + 2
          else
            table.insert(new_tokens, typo_end + 1)
          end
        end
      until (not token_end or token_end >= typo_end)
    end

    -- add tokens left after we handled all typos
    for i = i, #tokens, 1 do -- luacheck: ignore i
      table.insert(new_tokens, tokens[i])
    end

    old_new_tokens = new_tokens
    return new_tokens, timedout
  end
end

local enable_spellcheck = function()
  -- prevent wrapping the lex function multiple times
  if wrapped_lex_funcs[vis.win] then
    return
  end

  if not spellcheck.disable_syntax_awareness and vis.win.syntax and
      vis.lexers.load then
    local lexer = vis.lexers.load(vis.win.syntax, nil, true)
    if lexer and lexer.lex then
      local old_lex_func = lexer.lex
      wrapped_lex_funcs[vis.win] = old_lex_func
      lexer.lex = wrap_lex_func(old_lex_func)
      -- reset last data to enforce new highlighting
      last_data = ''
      return
    end
  end

  -- fallback check spellcheck the full viewport
  spellcheck.check_full_viewport[vis.win] = true
end

local is_spellcheck_enabled = function()
  return spellcheck.check_full_viewport[vis.win] or wrapped_lex_funcs[vis.win]
end

vis:map(vis.modes.NORMAL, '<C-w>e', function()
  enable_spellcheck()
end, 'Enable spellchecking in the current window')

local disable_spellcheck = function()
  local old_lex_func = wrapped_lex_funcs[vis.win]
  if old_lex_func then
    local lexer = vis.lexers.load(vis.win.syntax, nil, true)
    lexer.lex = old_lex_func
    wrapped_lex_funcs[vis.win] = nil
  else
    spellcheck.check_full_viewport[vis.win] = nil
  end
end

vis:map(vis.modes.NORMAL, '<C-w>d', function()
  disable_spellcheck()
  -- force new highlight
  vis.win:draw()
end, 'Disable spellchecking in the current window')

-- toggle spellchecking on <F7>
-- <F7> is used by some word processors (LibreOffice) for spellchecking
-- Thanks to @leorosa for the hint.
vis:map(vis.modes.NORMAL, '<F7>', function()
  if not is_spellcheck_enabled() then
    enable_spellcheck()
  else
    disable_spellcheck()
    vis.win:draw()
  end
  return 0
end, 'Toggle spellchecking in the current window')

vis:map(vis.modes.NORMAL, '<C-w>w', function()
  local win = vis.win
  local file = win.file
  local pos = win.selection.pos
  if not pos then
    return
  end
  local range = file:text_object_word(pos);
  if not range then
    return
  end
  if range.start == range.finish then
    return
  end

  local cmd = spellcheck.cmd:format(spellcheck.get_lang())
  local ret, so, se = vis:pipe(win.file, range, cmd)
  if ret ~= 0 then
    vis:message('calling ' .. cmd .. ' failed (' .. se .. ')')
    return false
  end

  local answer_line = so:match('.-\n(.-)\n.*')
  if not answer_line then
    return false
  end

  local suggestions
  local first_char = answer_line:sub(0, 1)
  if first_char == '*' then
    vis:info(file:content(range) .. ' is correctly spelled')
    return true
  elseif first_char == '#' then
    vis:info('No corrections available for ' .. file:content(range))
    return false
  elseif first_char == '&' then
    suggestions = answer_line:match('& %S+ %d+ %d+: (.*)')
  else
    vis:info('Unknown answer: ' .. answer_line)
    return false
  end

  -- select a correction
  cmd = 'printf "' .. suggestions:gsub(', ', '\\n') .. '\\n" | vis-menu'
  local status, correction = vis:pipe(file, {start = 0, finish = 0}, cmd)
  if status == 0 then
    -- trim correction
    correction = correction:match('^%s*(.-)%s*$')
    win.file:delete(range)
    win.file:insert(range.start, correction)
  end

  win.selection.pos = pos

  win:draw()

  return 0
end, 'Correct misspelled word')

vis:map(vis.modes.NORMAL, '<C-w>i', function()
  local win = vis.win
  local file = win.file
  local pos = win.selection.pos
  if not pos then
    return
  end
  local range = file:text_object_word(pos);
  if not range then
    return
  end
  if range.start == range.finish then
    return
  end

  ignored[file:content(range)] = true

  -- Check if we use our syntax aware spellcheck lex-closure
  -- We must rebuild the closure because it captures ignored
  -- to include the new addition
  local old_lex_func = wrapped_lex_funcs[vis.win]
  if old_lex_func then
    local lexer = vis.lexers.load(vis.win.syntax, nil, true)
    lexer.lex = wrap_lex_func(old_lex_func)
    -- reset last data to enforce new highlighting
    last_data = ''
  end

  win:draw()
  return 0
end, 'Ignore misspelled word')

vis:option_register('spelllang', 'string', function(value)
  vis.win.file.spell_language = value
  vis:info('Spellchecking language is now ' .. value)
  -- force new highlight for full viewport
  last_viewport = nil
  -- force new highlight for syntax aware
  last_data = nil
  return true
end, 'The language used for spellchecking')

vis:command_register('spelllang', function()
  vis:info('The spellchecking language is ' .. spellcheck.get_lang())
end, 'Print the language used for spellchecking')

return spellcheck