-- Copyright (c) 2020-2021 hoob3rt
-- MIT license, see LICENSE for more details.
local M = {}
local cterm_colors
local utils = require 'lualine.utils.utils'
local section_highlight_map = {x = 'c', y = 'b', z = 'a'}
local active_theme = nil

local function sanitize_color(color)
  if type(color) == 'string' then
    if color:sub(1,1) == '#' then return color end -- RGB value
    local converter = require 'lualine.utils.cterm_colors'
    return converter.color_name2rgb(color)
  elseif type(color) == 'number' then
    if color > 255 then
      error("What's this it can't be higher then 255 and you've given "..color)
    end
    local converter = require 'lualine.utils.cterm_colors'
    return converter.cterm2rgb(color)
  end
end

function M.highlight(name, foreground, background, gui, link, reload)
  local command = {'highlight!'}
  if link and #link > 0 then
    vim.list_extend(command, {'link', name, link})
  else
    foreground = sanitize_color(foreground)
    background = sanitize_color(background)
    table.insert(command, name)
    if foreground and foreground ~= 'none' then
      table.insert(command, 'guifg=' .. foreground)
      if cterm_colors then
        table.insert(command,
                     'ctermfg=' .. cterm_colors.get_cterm_color(foreground))
      end
    end
    if background and background ~= 'none' then
      table.insert(command, 'guibg=' .. background)
      if cterm_colors then
        table.insert(command,
                     'ctermbg=' .. cterm_colors.get_cterm_color(background))
      end
    end
    if gui then
      table.insert(command, 'cterm=' .. gui)
      table.insert(command, 'gui=' .. gui)
    end
  end
  vim.cmd(table.concat(command, ' '))
  if not reload then
    utils.save_highlight(name, {name, foreground, background, gui, link, true})
  end
end

function M.create_highlight_groups(theme)
  utils.clear_highlights()
  active_theme = theme
  if not vim.opt.termguicolors:get() then
    cterm_colors = require 'lualine.utils.cterm_colors'
  end
  for mode, sections in pairs(theme) do
    for section, color in pairs(sections) do
      local highlight_group_name = {'lualine', section, mode}
      if type(color) == 'string' then -- link to a highlight group
        M.highlight(table.concat(highlight_group_name, '_'), nil,
                    nil, nil, color)
      else -- Define a new highlight
        M.highlight(table.concat(highlight_group_name, '_'), color.fg,
                    color.bg, color.gui, nil)
      end
    end
  end
end

-- @description: adds '_mode' at end of highlight_group
-- @param highlight_group:(string) name of highlight group
-- @return: (string) highlight group name with mode
local function append_mode(highlight_group)
  local mode = require('lualine.utils.mode').get_mode()
  if mode == 'VISUAL' or mode == 'V-BLOCK' or mode == 'V-LINE' or mode ==
      'SELECT' or mode == 'S-LINE' or mode == 'S-BLOCK' then
    highlight_group = highlight_group .. '_visual'
  elseif mode == 'REPLACE' or mode == 'V-REPLACE' then
    highlight_group = highlight_group .. '_replace'
  elseif mode == 'INSERT' then
    highlight_group = highlight_group .. '_insert'
  elseif mode == 'COMMAND' or mode == 'EX' or mode == 'MORE' or mode ==
      'CONFIRM' then
    highlight_group = highlight_group .. '_command'
  elseif mode == 'TERMINAL' then
    highlight_group = highlight_group .. '_terminal'
  else
    highlight_group = highlight_group .. '_normal'
  end
  return highlight_group
end

-- Helper function for create component highlight
-- Handles fall back of colors when crea58ng highlight group
-- @param color table color passed for creating component highlight
-- @param options_color color set by color option for component
--        this is first falk back
-- @param default_color Colors et in theme this is 2nd fall back
-- @param kind (fg/bg))
local function get_default_component_color(color, options_color, default_color, kind)
  if color[kind] then return color[kind] end
  if options_color then
    if type(options_color) == 'table' and options_color[kind] then
      return options_color[kind]
    elseif type(options_color) == 'string' then
      return utils.extract_highlight_colors(options_color, kind)
    end
  end
  if type(default_color) == 'table' then
    return default_color[kind]
  elseif type(default_color) == 'string' then
    return utils.extract_highlight_colors(default_color, kind)
  end
end

-- Create highlight group with fg bg and gui from theme
-- @color has to be { fg = "#rrggbb", bg="#rrggbb" gui = "effect" }
-- all the color elements are optional if fg or bg is not given options must be provided
-- So fg and bg can default the themes colors
-- @highlight_tag is unique tag for highlight group
-- returns the name of highlight group
-- @options is parameter of component.init() function
-- @return: (string) unique name that can be used by component_format_highlight
--   to retrive highlight group
function M.create_component_highlight_group(color, highlight_tag, options)
  local tag_id = 0
  while (utils.highlight_exists(table.concat(
                             {'lualine', highlight_tag, 'no_mode'}, '_'))
      or (options.self.section and utils.highlight_exists(table.concat(
                             {options.self.section, highlight_tag, 'normal'}, '_')))
) do
    highlight_tag = highlight_tag .. '_' .. tostring(tag_id)
    tag_id = tag_id + 1
  end
  if type(color) == 'string' then
    local highlight_group_name = table.concat(
                                     {'lualine', highlight_tag, 'no_mode'}, '_')
    M.highlight(highlight_group_name, nil, nil, nil, color) -- l8nk to group
    return highlight_group_name
  end
  if color.bg and color.fg then
    -- When bg and fg are both present we donn't need to set highlighs for
    -- each mode as they will surely look the same. So we can work without options
    local highlight_group_name = table.concat(
                                     {'lualine', highlight_tag, 'no_mode'}, '_')
    M.highlight(highlight_group_name, color.fg, color.bg, color.gui, nil)
    return highlight_group_name
  end

  local modes = {
    'normal', 'insert', 'visual', 'replace', 'command', 'terminal', 'inactive'
  }
  local normal_hl
  -- convert lualine_a -> a before setting section
  local section = options.self.section:match('lualine_(.*)')
  if section > 'c' and not active_theme.normal[section] then
    section = section_highlight_map[section] end
  for _, mode in ipairs(modes) do
    local highlight_group_name = {options.self.section, highlight_tag, mode}
    local default_color_table = active_theme[mode] and
                                    active_theme[mode][section] or
                                    active_theme.normal[section]
    local bg = get_default_component_color(color, options.color, default_color_table, 'bg')
    local fg = get_default_component_color(color, options.color, default_color_table, 'fg')
    -- Check if it's same as normal mode if it is no need to create aditional highlight
    if mode ~= 'normal' then
      if bg ~= normal_hl.bg or fg ~= normal_hl.fg then
        M.highlight(table.concat(highlight_group_name, '_'), fg, bg, color.gui,
                    nil)
      end
    else
      normal_hl = {bg = bg, fg = fg}
      M.highlight(table.concat(highlight_group_name, '_'), fg, bg, color.gui,
                  nil)
    end
  end
  return options.self.section .. '_' .. highlight_tag
end

-- @description: retrieve highlight_groups for components
-- @param highlight_name:(string) highlight group name without mode
--   return value of create_component_highlight_group is to be passed in
--   this parameter to receive highlight that was created
-- @return: (string) formated highlight group name
function M.component_format_highlight(highlight_name)
  local highlight_group = highlight_name
  if highlight_name:find('no_mode') == #highlight_name - #'no_mode' + 1 then
    return '%#' .. highlight_group .. '#'
  end
  if utils.is_focused() then
    highlight_group = append_mode(highlight_group)
  else
    highlight_group = highlight_group .. '_inactive'
  end
  if utils.highlight_exists(highlight_group) then
    return '%#' .. highlight_group .. '#'
  else
    return '%#' .. highlight_name .. '_normal#'
  end
end

function M.format_highlight(is_focused, highlight_group)
  if highlight_group > 'lualine_c'
    and not utils.highlight_exists(highlight_group .. '_normal') then
    highlight_group = 'lualine_' ..
                          section_highlight_map[highlight_group:match(
                              'lualine_(.)')]
  end
  local highlight_name
  if not is_focused then
    highlight_name = highlight_group .. [[_inactive]]
  else
    highlight_name = append_mode(highlight_group)
  end
  if utils.highlight_exists(highlight_name) then
    return '%#' .. highlight_name .. '#'
  end
  return '%#' .. highlight_group .. '_normal#'
end

-- @description : Provides transitional highlights for section separators.
-- @param left_hl :(string) this highlights bg is used for fg of transitional hl
-- @param right_hl:(string) this highlights bg is used for bg of transitional hl
--    '▶️' and '◀️' ' eeds reverse colors so the caller should swap left and right
-- @return: (string) formated highlight group name
function M.get_transitional_highlights(left_hl, right_hl)
  -- When both left and right highlights are same or one is absent
  -- nothing to transition to.
  if left_hl == nil or right_hl == nil or left_hl == right_hl then return nil end

  -- construct the name of hightlight group
  local highlight_name = table.concat({'lualine_transitional',left_hl,'to',right_hl}, '_')
  if not utils.highlight_exists(highlight_name) then
    -- Create the highlight_group if needed
    -- Get colors from highlights
    local fg = utils.extract_highlight_colors(left_hl, 'bg')
    local bg = utils.extract_highlight_colors(right_hl, 'bg')
    if not fg or not bg then return nil end -- Color retrieval failed
    if bg == fg then return nil end -- Separator won't be visible anyway
    M.highlight(highlight_name, fg, bg, nil)
  end
  return '%#' .. highlight_name .. '#'
end

return M