-- Copyright (c) 2020-2021 hoob3rt
-- MIT license, see LICENSE for more details.

local utils_component = require('lualine.utils.component')
local utils = require('lualine.utils.utils')
local highlight = require('lualine.highlight')

local M = { }

local theme_set = {}

M.options = {
  icons_enabled = true,
  theme = 'gruvbox',
  component_separators = {'', ''},
  section_separators = {'', ''},
}


M.sections = {
  lualine_a = { 'mode' },
  lualine_b = { 'branch' },
  lualine_c = { 'filename' },
  lualine_x = { 'encoding', 'fileformat', 'filetype' },
  lualine_y = { 'progress' },
  lualine_z = { 'location'  },
}

M.inactive_sections = {
  lualine_a = {  },
  lualine_b = {  },
  lualine_c = { 'filename' },
  lualine_x = { 'location' },
  lualine_y = {  },
  lualine_z = {  }
}

M.extensions = { }

local function apply_configuration(config_table)
  if not config_table then return end
  local function parse_sections(section_group_name)
    if not config_table[section_group_name] then return end
    for section_name, section in pairs(config_table[section_group_name]) do
      M[section_group_name][section_name] = config_table[section_group_name][section_name]
      if type(section) == 'table' then
        for _, component in pairs(section) do
          if type(component) == 'table' and type(component[2]) == 'table' then
            local options = component[2]
            component[2] = nil
            for key, val in pairs(options) do
              component[key] = val
            end
          end
        end
      end
    end
  end
  parse_sections('options')
  parse_sections('sections')
  parse_sections('inactive_sections')
  if config_table.extensions then M.extensions = config_table.extensions end
end


local function check_single_separator()
  local compoennt_separator = M.options.component_separators
  local section_separator = M.options.section_separators
  if M.options.component_separators ~=nil then
    if type(M.options.component_separators) == 'string' then
      M.options.component_separators = {compoennt_separator, compoennt_separator}
    elseif #M.options.component_separators == 1 then
      M.options.component_separators = {M.options.component_separators[1], M.options.component_separators[1]}
    end
  end
  if M.options.section_separators ~=nil then
    if type(M.options.section_separators) == 'string' then
      M.options.section_separators = {section_separator, section_separator}
    elseif #M.options.section_separators == 1 then
      M.options.section_separators = {M.options.section_separators[1], M.options.section_separators[1]}
    end
  end
end

local function load_special_components(component)
  return function()
    -- precedence lualine_component > vim_var > lua_var > vim_function
    if component:find('[gvtwb]?o?:') == 1 then
      -- vim veriable component
      -- accepts g:, v:, t:, w:, b:, o, go:, vo:, to:, wo:, bo:
      -- filters g portion from g:var
      local scope = component:match('[gvtwb]?o?')
      -- filters var portion from g:var
      -- For some reason overwriting component var from outer scope causes the
      -- component not to work . So creating a new local name component to use:/
      local component = component:sub(#scope + 2, #component)
      -- Displays nothing when veriable aren't present
      local return_val = vim[scope][component]
      if return_val == nil then return '' end
      local ok
      ok, return_val =  pcall(tostring, return_val)
      if ok then return return_val end
      return ''
    elseif loadstring(string.format('return %s ~= nil', component)) and
      loadstring(string.format([[return %s ~= nil]], component))() then
      -- lua veriable component
      return loadstring(string.format([[
      local ok, return_val = pcall(tostring, %s)
      if ok then return return_val end
      return '']], component))()
    else
      -- vim function component
      local ok, return_val = pcall(vim.fn[component])
      if not ok then return '' end -- function call failed
      ok, return_val =  pcall(tostring, return_val)
      if ok then return return_val else return '' end
    end
  end
end

local function component_loader(component)
  if type(component[1]) == 'function' then return component end
  if type(component[1]) == 'string' then
    -- Keep component name for later use as component[1] will be overwritten
    -- With component function
    component.component_name = component[1]
    -- apply default args
    for opt_name, opt_val in pairs(M.options) do
      if component[opt_name] == nil then
        component[opt_name] = opt_val
      end
    end
    -- load the component
    local ok, loaded_component = pcall(require, 'lualine.components.' .. component.component_name)
    if not ok then
      loaded_component = load_special_components(component.component_name)
    end
    component[1] = loaded_component
    if type(component[1]) == 'table' then
      component[1] = component[1].init(component)
    end
    -- set custom highlights
    if component.color then
      local function update_color()
        component.color_highlight = highlight.create_component_highlight_group(
        component.color, component.component_name, component)
      end
      update_color()
      utils.expand_set_theme(update_color)
    end
  end
end


local function load_components()
  local function load_sections(sections)
    for section_name, section in pairs(sections) do
      for index, component in pairs(section) do
        if type(component) == 'string' or type(component) == 'function' then
          component = {component}
        end
        component.self = {}
        component.self.section = section_name
        component_loader(component)
        section[index] = component
      end
    end
  end
  load_sections(M.sections)
  load_sections(M.inactive_sections)
end

local function  load_extensions()
  for _, extension in pairs(M.extensions) do
    if type(extension) == 'string' then
      require('lualine.extensions.' .. extension).load_extension()
    end
    if type(extension) == 'table' then
      extension.load_extension()
    end
    if type(extension) == 'function' then
      extension()
    end
  end
end

local function lualine_set_theme()
  if type(M.options.theme) == 'string' then
    M.options.theme = require('lualine.themes.'.. M.options.theme)
    -- change the theme table in component so their custom
    -- highlights can reflect theme change
    local function reset_component_theme(sections)
      for _, section in pairs(sections)do
        for _, component in pairs(section) do
          if type(component) == 'table' then
            component.theme = M.options.theme
          end
        end
      end
    end
    reset_component_theme(M.sections)
    reset_component_theme(M.inactive_sections)
  end
  utils.clear_highlights()
  highlight.create_highlight_groups(M.options.theme)
  theme_set = M.options.theme
end

local function statusline(sections, is_focused)
  if M.options.theme ~= theme_set then
    _G.lualine_set_theme()
  end
  local function create_status_builder()
    -- The sequence sections should maintain
    local section_sequence = {'a', 'b', 'c', 'x', 'y', 'z'}
    local status_builder = {}
    for _, section_name in ipairs(section_sequence) do
      if sections['lualine_'..section_name] then
        -- insert highlight+components of this section to status_builder
        local section_highlight = highlight.format_highlight(is_focused,
        'lualine_'..section_name)
        local section_data = utils_component.draw_section(sections['lualine_'..section_name], section_highlight)
        if #section_data > 0 then
          table.insert(status_builder, {name = section_name, data = section_data,})
        end
      end
    end
    return status_builder
  end
  -- status_builder stores statusline without section_separators
  local status_builder = create_status_builder()

  -- Actual statusline
  local status = {}
  local half_passed = false
  for i=1,#status_builder do
    -- midsection divider
    if not half_passed and status_builder[i].name > 'c' then
      table.insert(status, highlight.format_highlight(is_focused, 'lualine_c') .. '%=')
      half_passed = true
    end
    -- provide section_separators when statusline is in focus
    if is_focused then
      -- component separator needs to have fg = current_section.bg
      -- and bg = adjacent_section.bg
      local previous_section = status_builder[i-1] or {}
      local current_section = status_builder[i]
      local next_section = status_builder[i+1] or {}
      -- For 2nd half we need to show separator before section
      if current_section.name > 'x' then
        local transitional_highlight = highlight.get_transitional_highlights(previous_section.data, current_section.data, true)
        if transitional_highlight and M.options.section_separators and M.options.section_separators[2] then
          table.insert(status, transitional_highlight .. M.options.section_separators[2])
        end
      end

      -- **( insert the actual section in the middle )** --
      table.insert(status, status_builder[i].data)

      -- For 1st half we need to show separator after section
      if current_section.name < 'c' then
        local transitional_highlight = highlight.get_transitional_highlights(current_section.data, next_section.data)
        if transitional_highlight and M.options.section_separators and M.options.section_separators[1] then
          table.insert(status, transitional_highlight .. M.options.section_separators[1])
        end
      end
    else -- when not in focus
      table.insert(status, status_builder[i].data)
    end
  end
  -- incase none of x,y,z was configured lets not fill whole statusline with a,b,c section
  if not half_passed then
    table.insert(status, highlight.format_highlight(is_focused,'lualine_c').."%=")
  end
  return table.concat(status)
end

local function status_dispatch()
  if vim.g.statusline_winid == vim.fn.win_getid() then
    return statusline(M.sections, true)
  else
    return statusline(M.inactive_sections, false)
  end
end

local function exec_autocommands()
  _G.lualine_set_theme = lualine_set_theme
  _G.lualine_statusline = status_dispatch
  vim.api.nvim_exec([[
  augroup lualine
  autocmd!
  autocmd ColorScheme * call v:lua.lualine_set_theme()
  autocmd WinLeave,BufLeave * lua vim.wo.statusline=lualine_statusline()
  autocmd WinEnter,BufEnter * setlocal statusline=%!v:lua.lualine_statusline()
  augroup END
  ]], false)
end

function M.status(config)
  apply_configuration(vim.g.lualine)
  apply_configuration(config)
  check_single_separator()
  lualine_set_theme()
  exec_autocommands()
  load_components()
  load_extensions()
end

return M