// Utils used to parse miaf-based files (avif/heic/heif)
//
//  - image collections are not supported (only last size is reported)
//  - images with metadata encoded after image data are not supported
//  - images without any `ispe` box are not supported
//

/* eslint-disable consistent-return */

'use strict';


var str2arr      = require('../common').str2arr;
var sliceEq      = require('../common').sliceEq;
var readUInt32BE = require('../common').readUInt32BE;
var miaf         = require('../miaf_utils');
var exif         = require('../exif_utils');

var SIG_FTYP = str2arr('ftyp');


module.exports = function (data) {
  // ISO media file (avif format) starts with ftyp box:
  // 0000 0020 6674 7970 6176 6966
  //  (length)  f t  y p  a v  i f
  //
  if (!sliceEq(data, 4, SIG_FTYP)) return;

  var firstBox = miaf.unbox(data, 0);
  if (!firstBox) return;

  var fileType = miaf.getMimeType(firstBox.data);
  if (!fileType) return;

  var meta, offset = firstBox.end;

  for (;;) {
    var box = miaf.unbox(data, offset);
    if (!box) break;
    offset = box.end;

    // mdat block SHOULD be last (but not strictly required),
    // so it's unlikely that metadata is after it
    if (box.boxtype === 'mdat') return;
    if (box.boxtype === 'meta') {
      meta = box.data;
      break;
    }
  }

  if (!meta) return;

  var imgSize = miaf.readSizeFromMeta(meta);

  if (!imgSize) return;

  var result = {
    width:    imgSize.width,
    height:   imgSize.height,
    type:     fileType.type,
    mime:     fileType.mime,
    wUnits:   'px',
    hUnits:   'px'
  };

  if (imgSize.variants.length > 1) {
    result.variants = imgSize.variants;
  }

  if (imgSize.orientation) {
    result.orientation = imgSize.orientation;
  }

  if (imgSize.exif_location &&
      imgSize.exif_location.offset + imgSize.exif_location.length <= data.length) {

    var sig_offset = readUInt32BE(data, imgSize.exif_location.offset);
    var exif_data = data.slice(
      imgSize.exif_location.offset + sig_offset + 4,
      imgSize.exif_location.offset + imgSize.exif_location.length);

    var orientation = exif.get_orientation(exif_data);

    if (orientation > 0) result.orientation = orientation;
  }

  return result;
};