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

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

-- Note for now only works for termguicolors scope can be bg or fg or any other
-- attr parameter like bold/italic/reverse
function M.extract_highlight_colors(color_group, scope)
  if vim.fn.hlexists(color_group) == 0 then return nil end
  local color = vim.api.nvim_get_hl_by_name(color_group, true)
  if color.background ~= nil then
    color.bg = string.format('#%06x', color.background)
    color.background = nil
  end
  if color.foreground ~= nil then
    color.fg = string.format('#%06x', color.foreground)
    color.foreground = nil
  end
  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, highlight_args)
  M.loaded_highlights[highlight_name] = highlight_args
end

function M.reload_highlights()
  local highlight = require('lualine.highlight')
  for _, highlight_args in pairs(M.loaded_highlights) do
    highlight.highlight(unpack(highlight_args))
  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

-- 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

-- remove empty strings from list
function M.list_shrink(list)
  local new_list = {}
  for i = 1, #list do
    if list[i] and #list[i] > 0 then table.insert(new_list, list[i]) end
  end
  return new_list
end

-- Check if a auto command is already defined
local function autocmd_is_defined(event, patern, command_str)
  return vim.api.nvim_exec(string.format("au lualine %s %s",
                           event, patern), true):find(command_str) ~= nil
end

-- Define a auto command if it's not already defined
function M.define_autocmd(event, patern, cmd)
  if not cmd then cmd = patern; patern = '*' end
  if not autocmd_is_defined(event, patern, cmd) then
    vim.cmd(string.format("autocmd lualine %s %s %s", event, patern, cmd))
  end
end

-- Check if statusline is on focused window or not
function M.is_focused()
  return tonumber(vim.g.actual_curwin) == vim.fn.win_getid()
end

function M.is_valid_filename(name)
  local invalid_chars="[^a-zA-Z0-9_. -]"
  return name:find(invalid_chars) == nil
end

function M.charAt(str, pos)
  return string.char(str:byte(pos))
end

return M