import { readUInt, toHexString, toUTF8String } from "./utils.js";
function readIFD(input, isBigEndian) {
  const ifdOffset = readUInt(input, 32, 4, isBigEndian);
  return input.slice(ifdOffset + 2);
}
function readValue(input, isBigEndian) {
  const low = readUInt(input, 16, 8, isBigEndian);
  const high = readUInt(input, 16, 10, isBigEndian);
  return (high << 16) + low;
}
function nextTag(input) {
  if (input.length > 24) {
    return input.slice(12);
  }
}
function extractTags(input, isBigEndian) {
  const tags = {};
  let temp = input;
  while (temp && temp.length) {
    const code = readUInt(temp, 16, 0, isBigEndian);
    const type = readUInt(temp, 16, 2, isBigEndian);
    const length = readUInt(temp, 32, 4, isBigEndian);
    if (code === 0) {
      break;
    } else {
      if (length === 1 && (type === 3 || type === 4)) {
        tags[code] = readValue(temp, isBigEndian);
      }
      temp = nextTag(temp);
    }
  }
  return tags;
}
function determineEndianness(input) {
  const signature = toUTF8String(input, 0, 2);
  if ("II" === signature) {
    return "LE";
  } else if ("MM" === signature) {
    return "BE";
  }
}
const signatures = [
  // '492049', // currently not supported
  "49492a00",
  // Little endian
  "4d4d002a"
  // Big Endian
  // '4d4d002a', // BigTIFF > 4GB. currently not supported
];
const TIFF = {
  validate: (input) => signatures.includes(toHexString(input, 0, 4)),
  calculate(input) {
    const isBigEndian = determineEndianness(input) === "BE";
    const ifdBuffer = readIFD(input, isBigEndian);
    const tags = extractTags(ifdBuffer, isBigEndian);
    const width = tags[256];
    const height = tags[257];
    if (!width || !height) {
      throw new TypeError("Invalid Tiff. Missing tags");
    }
    return { height, width };
  }
};
export {
  TIFF
};