'use strict'

var readUInt16LE = require('../common').readUInt16LE

var HEADER = 0

var TYPE_ICO = 1

var INDEX_SIZE = 16

// Format specification:

// https://en.wikipedia.org/wiki/ICO_(file_format)#Icon_resource_structure

module.exports = function (data) {

var header = readUInt16LE(data, 0)

var type = readUInt16LE(data, 2)

var numImages = readUInt16LE(data, 4)

if (header !== HEADER || type !== TYPE_ICO || !numImages) {

return

}

if (data.length < 6 + numImages * INDEX_SIZE) return

var variants = []

var maxSize = { width: 0, height: 0 }

for (var i = 0; i < numImages; i++) {

var width = data[6 + INDEX_SIZE * i] || 256

var height = data[6 + INDEX_SIZE * i + 1] || 256

var size = { width: width, height: height }

variants.push(size)

if (width > maxSize.width || height > maxSize.height) {

maxSize = size

}

}

return {

width: maxSize.width,

height: maxSize.height,

variants: variants,

type: 'ico',

mime: 'image/x-icon',

wUnits: 'px',

hUnits: 'px'

}

}