/**
 * Low-level SWF file parsing: decompression, tag reading, symbol class.
 */

import { inflateSync } from 'node:zlib'
import LZMA from 'lzma'

// ── SWF Tag Types ──────────────────────────────────────────────────
export const TAG_END = 0
export const TAG_DEFINE_BITS_LOSSLESS = 20
export const TAG_DEFINE_BITS_JPEG2 = 21
export const TAG_DEFINE_BITS_JPEG3 = 35
export const TAG_DEFINE_BITS_LOSSLESS2 = 36
export const TAG_SYMBOL_CLASS = 76
export const TAG_DEFINE_BINARY_DATA = 87

// ── Interfaces ─────────────────────────────────────────────────────

export interface SwfTag {
  type: number
  data: Buffer
}

export interface SymbolClassResult {
  /** charID → first symbol name (canonical name) */
  classNames: Map<number, string>
  /** symbol name → charID (all symbols including aliases) */
  symbols: Map<string, number>
}

// ── SWF Header Parsing ─────────────────────────────────────────────

export function decompressSwf(buffer: Buffer): Buffer {
  const sig = buffer.toString('ascii', 0, 3)

  if (sig === 'FWS') {
    return buffer
  }

  if (sig === 'CWS') {
    const header = Buffer.alloc(8)
    buffer.copy(header, 0, 0, 8)
    header.write('FWS', 0, 3, 'ascii')
    const compressed = buffer.subarray(8)
    const decompressed = inflateSync(compressed)
    return Buffer.concat([header, decompressed])
  }

  if (sig === 'ZWS') {
    const fileLength = buffer.readUInt32LE(4)
    const compressedSize = buffer.readUInt32LE(8)
    const lzmaData = buffer.subarray(12, 12 + compressedSize)

    const props = lzmaData.subarray(0, 5)
    const compressedPayload = lzmaData.subarray(5)

    const uncompressedSize = fileLength - 8
    const lzmaHeader = Buffer.alloc(13)
    props.copy(lzmaHeader, 0)
    lzmaHeader.writeUInt32LE(uncompressedSize, 5)
    lzmaHeader.writeUInt32LE(0, 9)

    const lzmaStream = Buffer.concat([lzmaHeader, compressedPayload])
    const decompressed = Buffer.from(LZMA.decompress(lzmaStream) as number[])

    const header = Buffer.alloc(8)
    buffer.copy(header, 0, 0, 8)
    header.write('FWS', 0, 3, 'ascii')
    return Buffer.concat([header, decompressed])
  }

  throw new Error(`Unknown SWF signature: ${sig}`)
}

function readRect(buf: Buffer, offset: number): number {
  const nbits = (buf[offset] >> 3) & 0x1f
  const totalBits = 5 + nbits * 4
  const totalBytes = Math.ceil(totalBits / 8)
  return offset + totalBytes
}

// ── SWF Tag Reader ─────────────────────────────────────────────────

export function parseSwfTags(swfBuffer: Buffer): SwfTag[] {
  const tags: SwfTag[] = []

  let offset = 8
  offset = readRect(swfBuffer, offset)
  offset += 4

  while (offset < swfBuffer.length) {
    if (offset + 2 > swfBuffer.length) break

    const tagCodeAndLength = swfBuffer.readUInt16LE(offset)
    offset += 2

    const tagType = (tagCodeAndLength >> 6) & 0x3ff
    let tagLength = tagCodeAndLength & 0x3f

    if (tagLength === 0x3f) {
      if (offset + 4 > swfBuffer.length) break
      tagLength = swfBuffer.readUInt32LE(offset)
      offset += 4
    }

    if (tagType === TAG_END) break
    if (offset + tagLength > swfBuffer.length) break

    const tagData = swfBuffer.subarray(offset, offset + tagLength)
    tags.push({ type: tagType, data: Buffer.from(tagData) })
    offset += tagLength
  }

  return tags
}

// ── SymbolClass Parser ─────────────────────────────────────────────

export function parseSymbolClass(data: Buffer): SymbolClassResult {
  const classNames = new Map<number, string>()
  const symbols = new Map<string, number>()
  let offset = 0

  const numSymbols = data.readUInt16LE(offset)
  offset += 2

  for (let i = 0; i < numSymbols; i++) {
    if (offset + 2 > data.length) break
    const charId = data.readUInt16LE(offset)
    offset += 2

    const strStart = offset
    while (offset < data.length && data[offset] !== 0) offset++
    const name = data.toString('utf-8', strStart, offset)
    offset++

    symbols.set(name, charId)
    if (!classNames.has(charId)) {
      classNames.set(charId, name)
    }
  }

  return { classNames, symbols }
}

// ── DefineBinaryData Parser ────────────────────────────────────────

export function parseBinaryData(data: Buffer): { id: number; content: Buffer } {
  const id = data.readUInt16LE(0)
  const content = data.subarray(6)
  return { id, content }
}