/**
 * aztec.ts — Aztec 2D barcode generation with round-trip verification.
 *
 * Browser path: ZXing's AztecEncoder renders to OffscreenCanvas → PNG.
 *   Using the same library for both encoding and decoding guarantees
 *   round-trip compatibility. bwip-js's mode-encoding choices (LATCH/SHIFT
 *   sequences) differed from ZXing's decoder expectations on certain data
 *   patterns, causing systematic AZTEC_CONTENT_MISMATCH errors. Switching
 *   to ZXing's own AztecEncoder eliminates the incompatibility entirely and
 *   also removes the 918 kB bwip-js chunk from all browser builds.
 *
 * Node/test path: bwip-js/node → PNG Buffer.
 *   OffscreenCanvas is unavailable in vitest; round-trip verification is
 *   skipped (decodeAztecFromPng returns null without a DOM). The generation
 *   tests for that path cover the encoder via separate code paths.
 */

import {
  AztecEncoder,
  BarcodeFormat,
  BinaryBitmap,
  DecodeHintType,
  HybridBinarizer,
  MultiFormatReader,
  RGBLuminanceSource,
} from "@zxing/library";
import {
  AZTEC_ECC_PERCENT,
  CodexError,
  type ChunkEnvelope,
} from "../../shared/codex-types";

export interface AztecImage {
  pngBytes: Uint8Array;
  width: number;
  height: number;
}

// ── Browser: ZXing Aztec encoding ────────────────────────────────────────────

/**
 * Render an Aztec barcode using ZXing's own encoder at 25% ECC, scale 4,
 * with a 2-module quiet zone. Using ZXing to both encode and decode guarantees
 * round-trip fidelity; the encoder uses the same HighLevelEncoder mode tables
 * that the decoder expects, so no mode-switching incompatibility is possible.
 */
async function generateAztecPngBrowser(payload: string): Promise<AztecImage> {
  // Encode payload as ISO-8859-1 bytes (= ASCII for our JSON envelope).
  const dataBytes = new Uint8Array(payload.length);
  for (let i = 0; i < payload.length; i++) dataBytes[i] = payload.charCodeAt(i);

  try {
    const aztecCode = AztecEncoder.encode(dataBytes, AZTEC_ECC_PERCENT, 0 /* auto layers */);
    const matrix = aztecCode.getMatrix();
    if (!matrix) throw new Error("encoder returned null matrix");

    const modules = matrix.getWidth(); // Aztec codes are always square
    const scale = 4;
    const pad = 2 * scale; // 2-module quiet zone (8 px at scale 4)
    const size = modules * scale + pad * 2;

    const canvas = new OffscreenCanvas(size, size);
    const ctx = canvas.getContext("2d")!;
    ctx.fillStyle = "#ffffff";
    ctx.fillRect(0, 0, size, size);
    ctx.fillStyle = "#000000";
    for (let y = 0; y < modules; y++) {
      for (let x = 0; x < modules; x++) {
        if (matrix.get(x, y)) {
          ctx.fillRect(pad + x * scale, pad + y * scale, scale, scale);
        }
      }
    }

    const blob = await canvas.convertToBlob({ type: "image/png" });
    const pngBytes = new Uint8Array(await blob.arrayBuffer());
    return { pngBytes, width: size, height: size };
  } catch (err) {
    throw new CodexError(
      "AZTEC_GENERATION_FAILED",
      `Aztec render failed: ${err instanceof Error ? err.message : String(err)}`,
    );
  }
}

// ── Node/test: bwip-js path ───────────────────────────────────────────────────

interface BwipNodeModule {
  toBuffer: (opts: Record<string, unknown>) => Promise<Buffer>;
}

let cachedBwipNode: BwipNodeModule | null = null;

async function loadBwipNode(): Promise<BwipNodeModule> {
  if (cachedBwipNode) return cachedBwipNode;
  // vitest / node only — bwip-js/node uses node:zlib which can't bundle for browser.
  const ns = (await import(/* @vite-ignore */ "bwip-js/node")) as Record<string, unknown>;
  const def = ns["default"] as Record<string, unknown> | undefined;
  const merged = { ...(def ?? {}), ...ns } as unknown as BwipNodeModule;
  cachedBwipNode = merged;
  return merged;
}

async function generateAztecPngNode(payload: string): Promise<AztecImage> {
  const mod = await loadBwipNode();
  const opts = {
    bcid: "azteccode",
    text: payload,
    eclevel: AZTEC_ECC_PERCENT.toString(),
    scale: 4,
    padding: 2,
    monochrome: true,
  } as const;

  try {
    const buf = await mod.toBuffer(opts);
    const pngBytes = new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength).slice();
    const { width, height } = readPngDimensions(pngBytes);
    return { pngBytes, width, height };
  } catch (err) {
    throw new CodexError(
      "AZTEC_GENERATION_FAILED",
      `Aztec render failed: ${err instanceof Error ? err.message : String(err)}`,
    );
  }
}

/** Read a PNG's IHDR width/height. PNGs always have IHDR as the first chunk. */
function readPngDimensions(png: Uint8Array): { width: number; height: number } {
  // PNG signature: 8 bytes, then 4-byte chunk length, "IHDR", then width/height as big-endian uint32.
  if (png.length < 24) {
    throw new CodexError("AZTEC_GENERATION_FAILED", "PNG buffer too small to contain IHDR");
  }
  const view = new DataView(png.buffer, png.byteOffset, png.byteLength);
  const width = view.getUint32(16, false);
  const height = view.getUint32(20, false);
  return { width, height };
}

// ── Aztec PNG generation (public) ────────────────────────────────────────────

/**
 * Render an Aztec barcode and return its PNG bytes + dimensions.
 * Browser: ZXing AztecEncoder → OffscreenCanvas → PNG.
 * Node/test: bwip-js/node → Buffer → PNG.
 */
export async function generateAztecPng(payload: string): Promise<AztecImage> {
  if (typeof OffscreenCanvas !== "undefined") {
    return generateAztecPngBrowser(payload);
  }
  return generateAztecPngNode(payload);
}

// ── Aztec PNG decoding (round-trip) ─────────────────────────────────────────

/**
 * Decode an Aztec PNG via @zxing. Returns the decoded UTF-8 text, or `null`
 * if decoding fails for any reason (no DOM, malformed PNG, no match found).
 * Never throws — the caller decides whether a `null` result is a verification
 * failure or a deliberate skip.
 */
export async function decodeAztecFromPng(pngBytes: Uint8Array): Promise<string | null> {
  // The decoder needs raw pixel data, which means we need a canvas to
  // rasterize the PNG into ImageData. Skip the round-trip in environments
  // without OffscreenCanvas (vitest with environment: 'node').
  if (typeof OffscreenCanvas === "undefined" || typeof createImageBitmap === "undefined") {
    return null;
  }

  try {
    // Copy into a fresh ArrayBuffer-backed view so Blob's typing is satisfied
    // (the input Uint8Array may be backed by a SharedArrayBuffer in some
    // bundler typings, which Blob's BlobPart union rejects).
    const owned = new Uint8Array(pngBytes.byteLength);
    owned.set(pngBytes);
    const blob = new Blob([owned], { type: "image/png" });
    const bitmap = await createImageBitmap(blob);
    const canvas = new OffscreenCanvas(bitmap.width, bitmap.height);
    const ctx = canvas.getContext("2d");
    if (!ctx) return null;
    // White-fill before drawing so any transparent pixels composite to white.
    ctx.fillStyle = "#ffffff";
    ctx.fillRect(0, 0, bitmap.width, bitmap.height);
    ctx.drawImage(bitmap, 0, 0);
    const imageData = ctx.getImageData(0, 0, bitmap.width, bitmap.height);

    // RGBLuminanceSource wants packed 32-bit ARGB values, not raw Uint8 RGBA.
    const argb = new Int32Array(bitmap.width * bitmap.height);
    const raw = imageData.data;
    for (let i = 0, j = 0; i < raw.length; i += 4, j++) {
      argb[j] = (0xff << 24) | (raw[i]! << 16) | (raw[i + 1]! << 8) | raw[i + 2]!;
    }

    const source = new RGBLuminanceSource(argb, bitmap.width, bitmap.height);
    const binarizer = new HybridBinarizer(source);
    const bitmapBinary = new BinaryBitmap(binarizer);

    const reader = new MultiFormatReader();
    const hints = new Map();
    hints.set(DecodeHintType.POSSIBLE_FORMATS, [BarcodeFormat.AZTEC]);
    hints.set(DecodeHintType.TRY_HARDER, true);
    reader.setHints(hints);

    const result = reader.decode(bitmapBinary);
    return result.getText();
  } catch {
    return null;
  }
}

// ── Verified Aztec generation ───────────────────────────────────────────────

/**
 * Generate the Aztec code for one envelope and confirm it round-trips. The
 * envelope JSON is serialized once and reused as the decode target so any
 * encoding mismatch (e.g. UTF-8 surrogate corruption) is caught immediately.
 *
 * In environments where round-trip decoding is unavailable (vitest node), the
 * verification step is skipped — the generator still throws on encoder
 * failure, which is the only condition this path can detect without a DOM.
 */
export async function generateVerifiedAztec(envelope: ChunkEnvelope): Promise<AztecImage> {
  const envelopeJson = JSON.stringify(envelope);

  let image: AztecImage;
  try {
    image = await generateAztecPng(envelopeJson);
  } catch (err) {
    if (err instanceof CodexError) throw err;
    throw new CodexError(
      "AZTEC_GENERATION_FAILED",
      `Failed to generate Aztec code for chunk ${envelope.i}: ${err instanceof Error ? err.message : String(err)}`,
    );
  }

  if (!image.pngBytes || image.pngBytes.length < 32) {
    throw new CodexError(
      "AZTEC_GENERATION_FAILED",
      `Aztec PNG for chunk ${envelope.i} was empty`,
    );
  }

  // Skip round-trip when we can't rasterize — see decodeAztecFromPng().
  if (typeof OffscreenCanvas === "undefined" || typeof createImageBitmap === "undefined") {
    return image;
  }

  // Retry up to 5 times on any decode failure — break immediately on a
  // confirmed correct decode. Track the last non-null wrong result so we
  // can surface diagnostic detail if all attempts fail.
  let decoded: string | null = null;
  let lastMismatch: string | null = null;
  for (let attempt = 0; attempt < 5; attempt++) {
    const candidate = await decodeAztecFromPng(image.pngBytes);
    if (candidate === envelopeJson) { decoded = candidate; break; }
    if (candidate !== null) lastMismatch = candidate;
  }
  if (decoded === null && lastMismatch === null) {
    throw new CodexError(
      "AZTEC_ROUNDTRIP_FAILED",
      `Chunk ${envelope.i} generated but cannot be decoded back after 5 attempts. This Codex cannot be trusted.`,
    );
  }
  if (decoded === null) {
    // lastMismatch is non-null — decoded something but wrong content.
    const el = envelopeJson.length;
    const dl = lastMismatch!.length;
    let diffAt = -1;
    for (let k = 0; k < Math.min(el, dl); k++) {
      if (envelopeJson[k] !== lastMismatch![k]) { diffAt = k; break; }
    }
    const ctx = (s: string) => JSON.stringify(s.slice(Math.max(0, diffAt - 8), diffAt + 20));
    throw new CodexError(
      "AZTEC_CONTENT_MISMATCH",
      `Chunk ${envelope.i}: expected len=${el} decoded len=${dl} first diff at pos ${diffAt}. ` +
        `expected: ${ctx(envelopeJson)} decoded: ${ctx(lastMismatch!)}`,
    );
  }
  return image;
}