new_ls_colors.lua

-- OSC 4 Color Parser for Neovim
-- Copyright Senghan Bright 2021

local uv = vim.loop

-- check if COLORTERM is advertised by the terminal emulator
local colorterm = os.getenv("COLORTERM")
if not (colorterm == "truecolor") then
  error("Truecolor environment not found. Ensure your terminal enables the 'COLORTERM' environment variable.")
end

if not vim.o.termguicolors then
  error("`termguicolors` option is not set. 256 color mode only works for RGB UIs.")
end

-- Ascii decimal value lookup
local char = string.char
local ascii = {
  BEL = char(7),
  ESC = char(27),
  NUM_FOUR = char(52),
  BACKSLASH = char(92),
  RBRACKET = char(93),
}

local OS_CMD_START = ascii.ESC .. ascii.RBRACKET .. ascii.NUM_FOUR
local OS_CMD_END = ascii.BACKSLASH .. ascii.BEL

--

local function stty_cmd(fd, cmd)
  local sys = vim.fn.system
  local stty_bin = "stty"
  local cmd_str = ("%s --file %s %s"):format(stty_bin, fd, cmd)

  return sys(cmd_str)
end

local function parse_rgb_entries(data)
  local rgb_pattern = "(%d+;rgb:%x+/%x+/%x+)"
  local color_pattern = "%x%x(%x%x)"

  local idx, rgb_str
  local res = {}
  for rgb_entry in data:gmatch(rgb_pattern) do
    idx = rgb_entry:match ".-(%d+);"
    rgb_str = "#"
    for c in rgb_entry:gmatch(color_pattern) do
      rgb_str = rgb_str .. c
    end
    res[idx] = rgb_str
  end

  return res
end

local function get_colors()
  local nvim_pid = vim.fn.getpid()
  local ppid = vim.api.nvim_get_proc(nvim_pid).ppid
  local fd = ("/proc/%d/fd/0"):format(ppid)

  -- save current mode settings and set raw mode
  local orig_mode = stty_cmd(fd, "--save")
  stty_cmd(fd, "raw -echo")

  -- open connection to STTY file
  local file_handle = assert(uv.fs_open(fd, "r+", 438))

  local TTY_BUF_READ_SIZE = 8192
  local chunk_size = 32

  local res = {}
  local query, data, chunk_results
  for j = 0, 255, chunk_size do
    -- build query string
    query = OS_CMD_START
    for idx = j + 0, j + chunk_size do
      query = query .. (";%d;?"):format(idx)
    end
    query = query .. OS_CMD_END
    assert(uv.fs_write(file_handle, query))

    -- read response
    data = assert(uv.fs_read(file_handle, TTY_BUF_READ_SIZE))
    chunk_results = parse_rgb_entries(data)
    for i, r in pairs(chunk_results) do
      res[i + 1] = r
    end
  end

  -- restore original TTY mode
  stty_cmd(fd, orig_mode)

  return res
end

local terminal_colors = get_colors()
local term_color
for i, color in ipairs(terminal_colors) do
  term_color = ("terminal_color_%d"):format(i-1)
  vim.g[term_color] = color
end