lualine.nvim/lua/lualine/utils/utils.lua

-- Copyright (c) 2020-2021 shadmansaleh
-- MIT license, see LICENSE for more details.
local M = {}

-- Works as a decorator to expand set_lualine_theme functions
-- functionality at runtime .
function M.expand_set_theme(func)
  -- execute a local version of global function to not get in a inf recurtion
  local set_theme = _G.lualine_set_theme
  _G.lualine_set_theme = function()
    set_theme()
    func()
  end
end

-- Note for now only works for termguicolors scope can be background or foreground
function M.extract_highlight_colors(color_group, scope)
  if vim.fn.hlexists(color_group) == 0 then return nil end
  local gui_colors = vim.api.nvim_get_hl_by_name(color_group, true)
  local cterm_colors = vim.api.nvim_get_hl_by_name(color_group, false)
  local color = {
    ctermfg = cterm_colors.foreground,
    ctermbg = cterm_colors.background
  }
  if gui_colors.background then
    color.guibg = string.format('#%06x', gui_colors.background)
    gui_colors.background = nil
  end
  if gui_colors.foreground then
    color.guifg = string.format('#%06x', gui_colors.foreground)
    gui_colors.foreground = nil
  end
  cterm_colors.background = nil
  cterm_colors.foreground = nil
  color = vim.tbl_extend('keep', color, gui_colors, cterm_colors)
  if scope then return color[scope] end
  return color
end

-- table to store the highlight names created by lualine
M.loaded_highlights = {}

-- sets loaded_highlights table
function M.save_highlight(highlight_name)
  M.loaded_highlights[highlight_name] = true
end

-- clears loaded_highlights table and highlights
function M.clear_highlights()
  for highlight_name, _ in pairs(M.loaded_highlights) do
    vim.cmd('highlight clear ' .. highlight_name)
    M.loaded_highlights[highlight_name] = nil
  end
end

-- determine if an highlight exist and isn't cleared
function M.highlight_exists(highlight_name)
  return M.loaded_highlights[highlight_name] and true or false
end

return M