import { crc32 } from '../util.js';
import { textEncoder } from './util.js';

export type LocalHeaderParams = {
  creationDate?: Date;
  filename: string;
  data: Uint8Array;
  compressedData?: Uint8Array;
  extraDataLength: number;
};

export type CentralDirectoryFileSpec = {
  localHeaderOffset: number;
  deflated: boolean;
  creationDate: Date;
  crc32: number;
  dataLength: number;
  compressedDataLength: number;
  filename: string;
};

export type CentralFileDirectorySpec = {
  files: CentralDirectoryFileSpec[];
  trailingLength: number;
  offset: number;
};

export function buildLocalZipHeader({
  creationDate = new Date(),
  filename,
  data,
  compressedData,
  extraDataLength,
}: LocalHeaderParams): Uint8Array {
  const creationTimeZip =
    (creationDate.getHours() << 11) |
    (creationDate.getDay() << 5) |
    Math.round(creationDate.getSeconds() / 2);
  const creationDateZip =
    ((creationDate.getFullYear() - 1980) << 9) |
    ((creationDate.getMonth() + 1) << 5) |
    creationDate.getDate();
  const dataCrc = crc32(data);
  const filenameEncoded = textEncoder.encode(filename);
  // 2 bytes for zlib header
  const compressedLength = compressedData ? (compressedData.length - 2) : data.length;
  return new Uint8Array([
    // PKZIP magic number
    0x50,
    0x4b,
    // Local File Header magic
    0x03,
    0x04,
    // Required PKZip version
    0x14,
    0x00,
    // General purpose bit flag, 2 bytes
    0b00000000,
    0b00000000,
    // Compression method, 2 bytes little endian
    compressedData ? 0x08 : 0x00,
    0x00,
    // Creation time, 2 bytes little endian
    creationTimeZip & 0xff,
    creationTimeZip >> 8,
    // Creation date, 2 bytes little endian
    creationDateZip & 0xff,
    creationDateZip >> 8,
    // CRC32 of data, 4 bytes little endian
    dataCrc & 0xff,
    (dataCrc >> 8) & 0xff,
    (dataCrc >> 16) & 0xff,
    (dataCrc >> 24) & 0xff,
    // Compressed size, 4 bytes little endian
    compressedLength & 0xff,
    (compressedLength >> 8) & 0xff,
    (compressedLength >> 16) & 0xff,
    (compressedLength >> 24) & 0xff,
    // Uncompressed size, 4 bytes little endian
    data.length & 0xff,
    (data.length >> 8) & 0xff,
    (data.length >> 16) & 0xff,
    (data.length >> 24) & 0xff,
    // Filename length, 2 bytes little endian
    filenameEncoded.length & 0xff,
    filenameEncoded.length >> 8, // Filename length in little endian
    // Extra field length, 2 bytes little endian
    (extraDataLength + 4) & 0xff,
    (extraDataLength + 4) >> 8,
    // Encoded file name
    ...filenameEncoded,
    // Beginning of extra field: identifier, 2 bytes
    0xff,
    0xff,
    // Beginning of extra field: length, 2 bytes little endian
    extraDataLength & 0xff,
    extraDataLength >> 8,
  ]);
}

export function buildCentralFileDirectory({
  files,
  trailingLength,
  offset
}: CentralFileDirectorySpec): Uint8Array {
  const chunks = files.map(buildCentralDirectoryFileHeader);
  const cdSize =  chunks.reduce((acc, chunk) => acc + chunk.length, 0);
  chunks.push(new Uint8Array([
    // PKZIP magic number
    0x50,
    0x4b,
    // End of central directory magic
    0x05,
    0x06,
    // Disk number
    0x00,
    0x00,
    // Disk with central directory
    0x00,
    0x00,
    // Disk entries
    files.length & 0xff,
    files.length >> 8,
    // Total entries
    files.length & 0xff,
    files.length >> 8,
    // Central directory size,
    cdSize & 0xff,
    (cdSize >> 8) & 0xff,
    (cdSize >> 16) & 0xff,
    (cdSize >> 24) & 0xff,
    // Offset of central directory in file
    offset & 0xff,
    (offset >> 8) & 0xff,
    (offset >> 16) & 0xff,
    (offset >> 24) & 0xff,
    // Length of trailing comment
    trailingLength & 0xff,
    trailingLength >> 8,
  ]));
  return new Uint8Array(
    chunks.reduce((acc: number[], curr) => {
      acc.push(...curr);
      return acc;
    }, [])
  );
}

function buildCentralDirectoryFileHeader(
  spec: CentralDirectoryFileSpec
): Uint8Array {
  const creationTimeZip =
    (spec.creationDate.getHours() << 11) |
    (spec.creationDate.getMinutes() << 5) |
    Math.round(spec.creationDate.getSeconds() / 2);
  const creationDateZip =
    ((spec.creationDate.getFullYear() - 1980) << 9) |
    ((spec.creationDate.getMonth() +1) << 5) |
    spec.creationDate.getDate();
  const filenameEncoded = textEncoder.encode(spec.filename);
  return new Uint8Array([
    // PKZIP magic number
    0x50,
    0x4b,
    // Central directory file header magic
    0x01,
    0x02,
    // Version
    0x17,
    0x03,
    //  Version needed
    0x14,
    0x00,
    // Flags, none set
    0x00,
    0x00,
    // Compression method, 2 bytes little endian
    spec.deflated ? 0x08 : 0x00,
    0x00,
    // Creation time, 2 bytes little endian
    creationTimeZip & 0xff,
    creationTimeZip >> 8,
    // Creation date, 2 bytes little endian
    creationDateZip & 0xff,
    creationDateZip >> 8,
    // CRC32 of data, 4 bytes little endian
    spec.crc32 & 0xff,
    (spec.crc32 >> 8) & 0xff,
    (spec.crc32 >> 16) & 0xff,
    (spec.crc32 >> 24) & 0xff,
    // Compressed size, 4 bytes little endian
    spec.compressedDataLength & 0xff,
    (spec.compressedDataLength >> 8) & 0xff,
    (spec.compressedDataLength >> 16) & 0xff,
    (spec.compressedDataLength >> 24) & 0xff,
    // Uncompressed size, 4 bytes little endian
    spec.dataLength & 0xff,
    (spec.dataLength >> 8) & 0xff,
    (spec.dataLength >> 16) & 0xff,
    (spec.dataLength >> 24) & 0xff,
    // Filename length, 2 bytes little endian
    filenameEncoded.length & 0xff,
    filenameEncoded.length >> 8, // Filename length in little endian
    // Extra field length, 2 bytes little endian
    0x00,
    0x00,
    // File comment length, 2 bytes little endian
    0x00,
    0x00,
    // Disk # start, 2 bytes little endian
    0x00,
    0x00,
    // Internal Attribute, 2 bytes little endian
    0x00,
    0x00,
    // External Attribute, 4 bytes little endian
    0x00,
    0x00,
    0xa4,
    0x81,
    // Offset of local header, 4 bytes little endian
    spec.localHeaderOffset & 0xff,
    (spec.localHeaderOffset >> 8) &0xff,
    (spec.localHeaderOffset >> 16) &0xff,
    (spec.localHeaderOffset >> 24) &0xff,
    ...filenameEncoded,
  ]);
}