import { Bzip2Error, BZIP2_ERROR_CODES } from '../errors.js';
import type { IBitReader, IHuffmanGroup } from '../interfaces.js';

// Re-export Bzip2Error for backward compatibility
export { Bzip2Error };

/**
 * Throw a BZIP2 error with proper error code
 */
function throwError(message: string, code: string = BZIP2_ERROR_CODES.INVALID_BLOCK_DATA): never {
  throw new Bzip2Error(message, code);
}

/**
 * BZIP2 decompression implementation
 */
export class Bzip2 {
  // CRC32 lookup table for BZIP2
  public readonly crcTable: readonly number[] = [
    0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
    0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
    0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 0x4c11db70, 0x48d0c6c7,
    0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
    0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3,
    0x709f7b7a, 0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
    0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, 0xbaea46ef,
    0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
    0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c, 0xc3f706fb,
    0xceb42022, 0xca753d95, 0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
    0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
    0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
    0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x018aeb13, 0x054bf6a4,
    0x0808d07d, 0x0cc9cdca, 0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
    0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08,
    0x571d7dd1, 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
    0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc,
    0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
    0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 0xe0b41de7, 0xe4750050,
    0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
    0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
    0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
    0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, 0x4f040d56, 0x4bc510e1,
    0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
    0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5,
    0x3f9b762c, 0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
    0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e, 0xf5ee4bb9,
    0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
    0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd,
    0xcda1f604, 0xc960ebb3, 0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
    0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
    0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
    0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2,
    0x470cdd2b, 0x43cdc09c, 0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
    0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e,
    0x18197087, 0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
    0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a,
    0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
    0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 0xe3a1cbc1, 0xe760d676,
    0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
    0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
    0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
    0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4,
  ];

  // State arrays initialized in header()
  private byteCount!: Int32Array;
  private symToByte!: Uint8Array;
  private mtfSymbol!: Int32Array;
  private selectors!: Uint8Array;

  /**
   * Create a bit reader from a byte array
   */
  array(bytes: Uint8Array | Buffer): (n: number) => number {
    let bit = 0;
    let byte = 0;
    const BITMASK = [0, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff];

    return function (n: number): number {
      let result = 0;
      while (n > 0) {
        const left = 8 - bit;
        if (n >= left) {
          result <<= left;
          result |= BITMASK[left] & bytes[byte++];
          bit = 0;
          n -= left;
        } else {
          result <<= n;
          result |= (bytes[byte] & (BITMASK[n] << (8 - n - bit))) >> (8 - n - bit);
          bit += n;
          n = 0;
        }
      }
      return result;
    };
  }

  /**
   * Simple decompression from a buffer
   */
  simple(srcbuffer: Uint8Array | Buffer, stream: (byte: number) => void): void {
    const bits = this.array(srcbuffer);
    const size = this.header(bits as IBitReader);
    let ret: number | null = 0;
    const bufsize = 100000 * size;
    const buf = new Int32Array(bufsize);

    do {
      ret = this.decompress(bits as IBitReader, stream, buf, bufsize, ret);
    } while (ret !== null);
  }

  /**
   * Parse BZIP2 header and return block size
   */
  header(bits: IBitReader): number {
    this.byteCount = new Int32Array(256);
    this.symToByte = new Uint8Array(256);
    this.mtfSymbol = new Int32Array(256);
    this.selectors = new Uint8Array(0x8000);

    if (bits(8 * 3) !== 4348520) {
      throwError('No BZIP2 magic number found at start of stream', BZIP2_ERROR_CODES.NO_MAGIC_NUMBER);
    }

    const blockSize = (bits(8) as number) - 48;
    if (blockSize < 1 || blockSize > 9) {
      throwError('Invalid BZIP2 archive: block size must be 1-9', BZIP2_ERROR_CODES.INVALID_ARCHIVE);
    }
    return blockSize;
  }

  /**
   * Decompress a BZIP2 block
   */
  decompress(
    bits: IBitReader,
    stream: (byte: number) => void,
    buf: Int32Array,
    bufsize: number,
    streamCRC?: number | null
  ): number | null {
    const MAX_HUFCODE_BITS = 20;
    const MAX_SYMBOLS = 258;
    const SYMBOL_RUNA = 0;
    const SYMBOL_RUNB = 1;
    const GROUP_SIZE = 50;
    let crc = 0 ^ -1;

    // Read block header
    let headerHex = '';
    for (let i = 0; i < 6; i++) {
      headerHex += (bits(8) as number).toString(16);
    }

    // Check for end-of-stream marker
    if (headerHex === '177245385090') {
      const finalCRC = bits(32) as number | 0;
      if (finalCRC !== streamCRC) {
        throwError('CRC32 mismatch: stream checksum verification failed', BZIP2_ERROR_CODES.CRC_MISMATCH);
      }
      // Align stream to byte boundary
      bits(null);
      return null;
    }

    // Verify block signature (pi digits)
    if (headerHex !== '314159265359') {
      throwError('Invalid block header: expected pi signature (0x314159265359)', BZIP2_ERROR_CODES.INVALID_BLOCK_DATA);
    }

    const crcblock = bits(32) as number | 0;

    if (bits(1)) {
      throwError('Unsupported obsolete BZIP2 format version', BZIP2_ERROR_CODES.INVALID_ARCHIVE);
    }

    const origPtr = bits(24) as number;
    if (origPtr > bufsize) {
      throwError('Initial position larger than buffer size', BZIP2_ERROR_CODES.BUFFER_OVERFLOW);
    }

    // Read symbol map
    let symbolMapBits = bits(16) as number;
    let symTotal = 0;
    for (let i = 0; i < 16; i++) {
      if (symbolMapBits & (1 << (15 - i))) {
        const subMap = bits(16) as number;
        for (let j = 0; j < 16; j++) {
          if (subMap & (1 << (15 - j))) {
            this.symToByte[symTotal++] = 16 * i + j;
          }
        }
      }
    }

    // Read Huffman groups
    const groupCount = bits(3) as number;
    if (groupCount < 2 || groupCount > 6) {
      throwError('Invalid group count: must be between 2 and 6', BZIP2_ERROR_CODES.INVALID_HUFFMAN);
    }

    const nSelectors = bits(15) as number;
    if (nSelectors === 0) {
      throwError('Invalid selector count: cannot be zero', BZIP2_ERROR_CODES.INVALID_SELECTOR);
    }

    // Initialize MTF symbol array
    for (let i = 0; i < groupCount; i++) {
      this.mtfSymbol[i] = i;
    }

    // Read selectors using MTF decoding
    for (let i = 0; i < nSelectors; i++) {
      let j = 0;
      while (bits(1)) {
        j++;
        if (j >= groupCount) {
          throwError('Invalid MTF index: exceeds group count', BZIP2_ERROR_CODES.INVALID_HUFFMAN);
        }
      }
      const uc = this.mtfSymbol[j];
      for (let k = j - 1; k >= 0; k--) {
        this.mtfSymbol[k + 1] = this.mtfSymbol[k];
      }
      this.mtfSymbol[0] = uc;
      this.selectors[i] = uc;
    }

    // Build Huffman tables
    const symCount = symTotal + 2;
    const groups: IHuffmanGroup[] = [];
    const length = new Uint8Array(MAX_SYMBOLS);
    const temp = new Uint16Array(MAX_HUFCODE_BITS + 1);

    for (let j = 0; j < groupCount; j++) {
      let t = bits(5) as number;
      for (let i = 0; i < symCount; i++) {
        while (true) {
          if (t < 1 || t > MAX_HUFCODE_BITS) {
            throwError('Invalid Huffman code length: must be between 1 and 20', BZIP2_ERROR_CODES.INVALID_HUFFMAN);
          }
          if (!bits(1)) break;
          if (!bits(1)) t++;
          else t--;
        }
        length[i] = t;
      }

      let minLen = length[0];
      let maxLen = length[0];
      for (let i = 1; i < symCount; i++) {
        if (length[i] > maxLen) maxLen = length[i];
        else if (length[i] < minLen) minLen = length[i];
      }

      const hufGroup: IHuffmanGroup = {
        permute: new Int32Array(MAX_SYMBOLS),
        limit: new Int32Array(MAX_HUFCODE_BITS + 1),
        base: new Int32Array(MAX_HUFCODE_BITS + 1),
        minLen,
        maxLen,
      };
      groups[j] = hufGroup;

      const base = hufGroup.base;
      const limit = hufGroup.limit;

      let pp = 0;
      for (let i = minLen; i <= maxLen; i++) {
        for (let t = 0; t < symCount; t++) {
          if (length[t] === i) hufGroup.permute[pp++] = t;
        }
      }

      for (let i = minLen; i <= maxLen; i++) {
        temp[i] = 0;
        limit[i] = 0;
      }
      for (let i = 0; i < symCount; i++) {
        temp[length[i]]++;
      }

      pp = 0;
      let tt = 0;
      for (let i = minLen; i < maxLen; i++) {
        pp += temp[i];
        limit[i] = pp - 1;
        pp <<= 1;
        base[i + 1] = pp - (tt += temp[i]);
      }
      limit[maxLen] = pp + temp[maxLen] - 1;
      base[minLen] = 0;
    }

    // Initialize for decoding
    for (let i = 0; i < 256; i++) {
      this.mtfSymbol[i] = i;
      this.byteCount[i] = 0;
    }

    let runPos = 0;
    let count = 0;
    let symCountRemaining = 0;
    let selector = 0;
    let hufGroup = groups[0];
    let base = hufGroup.base;
    let limit = hufGroup.limit;

    // Main decoding loop
    while (true) {
      if (!symCountRemaining--) {
        symCountRemaining = GROUP_SIZE - 1;
        if (selector >= nSelectors) {
          throwError('Invalid selector index: exceeds available groups', BZIP2_ERROR_CODES.INVALID_SELECTOR);
        }
        hufGroup = groups[this.selectors[selector++]];
        base = hufGroup.base;
        limit = hufGroup.limit;
      }

      let i = hufGroup.minLen;
      let j = bits(i) as number;

      while (true) {
        if (i > hufGroup.maxLen) {
          throwError('Huffman decoding error: bit length exceeds maximum allowed', BZIP2_ERROR_CODES.INVALID_HUFFMAN);
        }
        if (j <= limit[i]) break;
        i++;
        j = (j << 1) | (bits(1) as number);
      }

      j -= base[i];
      if (j < 0 || j >= MAX_SYMBOLS) {
        throwError('Symbol index out of bounds during Huffman decoding', BZIP2_ERROR_CODES.INVALID_HUFFMAN);
      }

      const nextSym = hufGroup.permute[j];

      if (nextSym === SYMBOL_RUNA || nextSym === SYMBOL_RUNB) {
        if (!runPos) {
          runPos = 1;
          j = 0;
        }
        if (nextSym === SYMBOL_RUNA) j += runPos;
        else j += 2 * runPos;
        runPos <<= 1;
        continue;
      }

      if (runPos) {
        runPos = 0;
        const runLength = j;
        if (count + runLength > bufsize) {
          throwError('Run-length overflow: decoded run exceeds buffer capacity', BZIP2_ERROR_CODES.BUFFER_OVERFLOW);
        }
        const uc = this.symToByte[this.mtfSymbol[0]];
        this.byteCount[uc] += runLength;
        for (let t = 0; t < runLength; t++) {
          buf[count++] = uc;
        }
      }

      if (nextSym > symTotal) break;

      if (count >= bufsize) {
        throwError('Buffer overflow: decoded data exceeds buffer capacity', BZIP2_ERROR_CODES.BUFFER_OVERFLOW);
      }

      const mtfIndex = nextSym - 1;
      const uc = this.mtfSymbol[mtfIndex];
      for (let k = mtfIndex - 1; k >= 0; k--) {
        this.mtfSymbol[k + 1] = this.mtfSymbol[k];
      }
      this.mtfSymbol[0] = uc;
      const decodedByte = this.symToByte[uc];
      this.byteCount[decodedByte]++;
      buf[count++] = decodedByte;
    }

    if (origPtr < 0 || origPtr >= count) {
      throwError('Invalid original pointer: position outside decoded block', BZIP2_ERROR_CODES.INVALID_POSITION);
    }

    // Inverse BWT transform
    let j = 0;
    for (let i = 0; i < 256; i++) {
      const k = j + this.byteCount[i];
      this.byteCount[i] = j;
      j = k;
    }

    for (let i = 0; i < count; i++) {
      const uc = buf[i] & 0xff;
      buf[this.byteCount[uc]] |= i << 8;
      this.byteCount[uc]++;
    }

    // Output decoded data
    let pos = 0;
    let current = 0;
    let run = 0;

    if (count) {
      pos = buf[origPtr];
      current = pos & 0xff;
      pos >>= 8;
      run = -1;
    }

    let remaining = count;
    while (remaining) {
      remaining--;
      const previous = current;
      pos = buf[pos];
      current = pos & 0xff;
      pos >>= 8;

      let copies: number;
      let outbyte: number;

      if (run++ === 3) {
        copies = current;
        outbyte = previous;
        current = -1;
      } else {
        copies = 1;
        outbyte = current;
      }

      while (copies--) {
        crc = ((crc << 8) ^ this.crcTable[((crc >> 24) ^ outbyte) & 0xff]) & 0xffffffff;
        stream(outbyte);
      }

      if (current !== previous) run = 0;
    }

    crc = (crc ^ -1) >>> 0;
    if ((crc | 0) !== (crcblock | 0)) {
      throwError('CRC32 mismatch: block checksum verification failed', BZIP2_ERROR_CODES.CRC_MISMATCH);
    }

    const newStreamCRC = (crc ^ (((streamCRC || 0) << 1) | ((streamCRC || 0) >>> 31))) & 0xffffffff;
    return newStreamCRC;
  }
}