get_term_colors.lua

#!/usr/bin/env luajit
local TOTAL_COLORS = 256

local char = string.char
local io_read = io.read
local byte = string.byte
local INDEX_MAX_DIGITS = #(tostring(TOTAL_COLORS)) + 1

-- Ascii decimal value lookup
local ascii = {
  BEL = 7,
  ESC = 27,
  NUM_FOUR = 52,
  SEMICOLON = 59,
  QUESTIONMARK = 63,
  BACKSLASH = 92,
  RBRACKET = 93,
}

-- control sequences
local RGB_START = { ascii.ESC, ascii.RBRACKET, ascii.NUM_FOUR, ascii.SEMICOLON }
local RGB_END = { ascii.ESC, ascii.BACKSLASH }
local OS_CMD_START = char(ascii.ESC) .. char(ascii.RBRACKET) .. char(ascii.NUM_FOUR)
local OS_CMD_END = char(ascii.BACKSLASH) .. char(ascii.BEL)

--

local util = {}

util.to_string = function(byte_array)
  local s = ""
  for i = 1, #byte_array do
    s = s .. char(byte_array[i])
  end
  return s
end

-- shallow check if two tables are identical
util.match = function(a, b)
  if #a ~= #b then
    return nil
  end
  for i = 1, #a do
    if a[i] ~= b[i] then
      return false
    end
  end
  return true
end

-- consumes n bytes from the IO stream
util.chomp = function(n) -- TODO: stop using string
  local bytes = assert({ byte(io_read(n), 1, n) }, "read_error")
  if bytes[n] then
    return bytes
  else
    return nil
  end
end


-- Terminal
local terminal = {}
terminal.setrawmode = function()
  return os.execute "stty raw -echo 2> /dev/null"
end

terminal.savemode = function()
  local handle = assert(io.popen("stty -g", "r"))
  local mode = assert(handle:read "*all")
  local success, e, msg = handle:close()
  -- print(inspect(mode))
  return success and mode or nil, e, msg -- TODO: handle all errors like this
end

terminal.restoremode = function(mode)
  return os.execute("stty " .. mode)
end

--
-- Args come in as a single 'index1;rgb1 ... ;indexN;rgbN' string.
--
local function get_color_entry(index)
  local b = util
  if not b.match(b.chomp(4), RGB_START) then
    error "NO HEADER FOUND"
    return nil
  end

  local color_id = {}
  local c = nil
  for i = 1, INDEX_MAX_DIGITS + 1 do
    c = b.chomp(1)[1]
    if c == ascii.SEMICOLON then
      break
    else
      color_id[i] = c
    end
  end

  if color_id == {} then
    error("Error: Index not found at " .. index .. "/" .. TOTAL_COLORS)
    return nil
  end

  -- get the bytes containing the RGB values
  local hex_color
  local chunk_bytes = b.chomp(20)

  -- check for the end marker
  if b.match({ chunk_bytes[19], chunk_bytes[20] }, RGB_END) then
    local rgb_values = {
      -- parse RGB from chunk: 'rgb:xxRR/xxGG/xxBB'
      chunk_bytes[7],
      chunk_bytes[8],
      chunk_bytes[12],
      chunk_bytes[13],
      chunk_bytes[17],
      chunk_bytes[18],
    }
    -- id = tonumber(b.to_string(color_id))
    hex_color = "#" .. b.to_string(rgb_values)
  else
    error("DEBUG: " .. b.to_string(chunk_bytes))
  end

  return hex_color
end

-- send escape sequence to query palette
local function osc_query_palette()
  -- build the query string
  local query = OS_CMD_START
  for idx = 0, TOTAL_COLORS do
    query = query .. char(ascii.SEMICOLON) .. idx .. char(ascii.SEMICOLON) .. char(ascii.QUESTIONMARK)
  end
  query = query .. OS_CMD_END
  -- print('DEBUG: '..query)
  -- write arguments to stdout, then flush.
  io.write(query)
  io.flush()
end

local function get_term_colors()
  local mode, _ = terminal.savemode()
  terminal.setrawmode()
  osc_query_palette()

  local results = {}
  for i = 1, TOTAL_COLORS do
    results[i] = get_color_entry(i)
  end
  -- local results = get_term_colors()
  terminal.restoremode(mode)

  print(#results)
  --
  for i, hex_color in ipairs(results) do
    print(string.format("[%s] - %s", i - 1, hex_color))
  end
end

get_term_colors()