import type { AssetManager } from '@/lib/assets/assetManager'

export type AssetMetaItem = {
  originalName: string
  mimeType: string
  size: number
  hash8: string
  ext: string
  zipPath: string
  integrity: string
  group: 'images' | 'fonts' | 'other'
  referencedAt: string[]
}

// Minimal synchronous SHA-256 implementation returning base64 string.
// Derived from the SHA-256 specification. Suitable for small payloads (asset bytes).
function sha256Base64(bytes: Uint8Array): string {
  const K = new Uint32Array([
    0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
    0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
    0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
    0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
    0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
    0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
    0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
    0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
  ])
  const H = new Uint32Array([
    0x6a09e667,0xbb67ae85,0x3c6ef372,0xa54ff53a,0x510e527f,0x9b05688c,0x1f83d9ab,0x5be0cd19
  ])
  const l = bytes.length
  const bitLenHi = Math.floor((l >>> 29))
  const bitLenLo = (l << 3) >>> 0
  // Pre-processing (padding)
  const withOne = l + 1
  // pad to congruent 56 mod 64
  const padLen = ((withOne % 64) <= 56) ? (56 - (withOne % 64)) : (56 + 64 - (withOne % 64))
  const totalLen = withOne + padLen + 8
  const m = new Uint8Array(totalLen)
  m.set(bytes)
  m[l] = 0x80
  // append 64-bit big-endian length
  m[totalLen - 8] = (bitLenHi >>> 24) & 0xff
  m[totalLen - 7] = (bitLenHi >>> 16) & 0xff
  m[totalLen - 6] = (bitLenHi >>> 8) & 0xff
  m[totalLen - 5] = (bitLenHi >>> 0) & 0xff
  m[totalLen - 4] = (bitLenLo >>> 24) & 0xff
  m[totalLen - 3] = (bitLenLo >>> 16) & 0xff
  m[totalLen - 2] = (bitLenLo >>> 8) & 0xff
  m[totalLen - 1] = (bitLenLo >>> 0) & 0xff
  const W = new Uint32Array(64)
  for (let i = 0; i < totalLen; i += 64) {
    for (let t = 0; t < 16; t++) {
      const j = i + t * 4
      W[t] = (m[j] << 24) | (m[j + 1] << 16) | (m[j + 2] << 8) | (m[j + 3])
    }
    for (let t = 16; t < 64; t++) {
      const s0 = (rotr(W[t - 15], 7) ^ rotr(W[t - 15], 18) ^ (W[t - 15] >>> 3)) >>> 0
      const s1 = (rotr(W[t - 2], 17) ^ rotr(W[t - 2], 19) ^ (W[t - 2] >>> 10)) >>> 0
      W[t] = (W[t - 16] + s0 + W[t - 7] + s1) >>> 0
    }
    let a = H[0], b = H[1], c = H[2], d = H[3], e = H[4], f = H[5], g = H[6], h = H[7]
    for (let t = 0; t < 64; t++) {
      const S1 = (rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25)) >>> 0
      const ch = ((e & f) ^ (~e & g)) >>> 0
      const temp1 = (h + S1 + ch + K[t] + W[t]) >>> 0
      const S0 = (rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22)) >>> 0
      const maj = ((a & b) ^ (a & c) ^ (b & c)) >>> 0
      const temp2 = (S0 + maj) >>> 0
      h = g
      g = f
      f = e
      e = (d + temp1) >>> 0
      d = c
      c = b
      b = a
      a = (temp1 + temp2) >>> 0
    }
    H[0] = (H[0] + a) >>> 0
    H[1] = (H[1] + b) >>> 0
    H[2] = (H[2] + c) >>> 0
    H[3] = (H[3] + d) >>> 0
    H[4] = (H[4] + e) >>> 0
    H[5] = (H[5] + f) >>> 0
    H[6] = (H[6] + g) >>> 0
    H[7] = (H[7] + h) >>> 0
  }
  const out = new Uint8Array(32)
  for (let i = 0; i < 8; i++) {
    out[i * 4 + 0] = (H[i] >>> 24) & 0xff
    out[i * 4 + 1] = (H[i] >>> 16) & 0xff
    out[i * 4 + 2] = (H[i] >>> 8) & 0xff
    out[i * 4 + 3] = (H[i] >>> 0) & 0xff
  }
  // base64 encode
  let b64 = ''
  if (typeof Buffer !== 'undefined') {
    b64 = Buffer.from(out).toString('base64')
  } else {
    let s = ''
    for (let i = 0; i < out.length; i++) s += String.fromCharCode(out[i])
    // btoa is available in browsers
    b64 = btoa(s)
  }
  return b64
  function rotr(x: number, n: number) { return (x >>> n) | (x << (32 - n)) }
}

export function buildAssetsMetadata(am: AssetManager): Uint8Array {
  const list = am.list()
  const referenced = new Set(am.referencedList())
  const items: AssetMetaItem[] = list.map((ref) => {
    // Compute real SHA-256(base64) integrity synchronously for browser/Node
    const b64 = sha256Base64(ref.bytes)
    const group: 'images' | 'fonts' | 'other' = ref.mimeType.startsWith('image/')
      ? 'images'
      : ref.mimeType.startsWith('font/')
      ? 'fonts'
      : 'other'
    const referencedAt = referenced.has(ref.originalName) ? [`local:${ref.originalName}`] : []
    return {
      originalName: ref.originalName,
      mimeType: ref.mimeType,
      size: ref.bytes.byteLength,
      hash8: ref.hash8,
      ext: ref.ext,
      zipPath: ref.path,
      integrity: `sha256-${b64}`,
      group,
      referencedAt,
    }
  })
  const json = JSON.stringify({ assets: items }, null, 2)
  return new TextEncoder().encode(json)
}