// 把差分掩码（立绘层 = 正常帧 − 藏 canvas 参考帧）压成 ASCII，
// 这样在没有图像输入能力的情况下也能"看"清构图。
// 用法：
//   node tools/ascii.mjs <normal.png> <ref.png> [cols]   差分两幅，打印强度图 + 实体占比图
//   node tools/ascii.mjs <image.png> [cols]              单幅，打印亮度图
// 行数按 2.2:1 的字符高宽比自动换算，保证画面不被压扁。

import { spawn } from "node:child_process";

const flags = process.argv.slice(2).filter((a) => a.startsWith("--"));
const [fileA, fileB, colsArg] = process.argv.slice(2).filter((a) => !a.startsWith("--"));
const solidOnly = flags.includes("--solid");
if (!fileA) {
  console.error("usage: node tools/ascii.mjs <image.png> [ref.png] [cols]");
  process.exit(2);
}

function probe(file) {
  return new Promise((resolve) => {
    const p = spawn("ffprobe", ["-v", "error", "-select_streams", "v:0", "-show_entries", "stream=width,height", "-of", "csv=p=0", file]);
    let out = "";
    p.stdout.on("data", (d) => (out += d));
    p.on("close", () => {
      const [w, h] = out.trim().split(",").map(Number);
      resolve({ w, h });
    });
  });
}

function gray(file) {
  return new Promise((resolve, reject) => {
    const p = spawn("ffmpeg", ["-v", "error", "-i", file, "-f", "rawvideo", "-pix_fmt", "gray", "-"], { stdio: ["ignore", "pipe", "pipe"] });
    const chunks = [];
    let err = "";
    p.stdout.on("data", (d) => chunks.push(d));
    p.stderr.on("data", (d) => (err += d));
    p.on("close", (code) => (code === 0 ? resolve(Buffer.concat(chunks)) : reject(new Error(err || `exit ${code}`))));
  });
}

const RAMP = " .:-=+*#%@";
const { w: W, h: H } = await probe(fileA);
const bufA = await gray(fileA);
if (bufA.length < W * H) {
  console.error(`像素不足：${bufA.length} < ${W * H}`);
  process.exit(1);
}

// 终端字符高约为宽的 2.2 倍，据此把列数换算成行数，保持画面比例
const cols = Math.max(20, Math.min(Number(colsArg) || 110, Math.floor((46 * 2.2 * W) / H)));
const rows = Math.max(6, Math.round((cols * H) / W / 2.2));
const cw = W / cols;
const chh = H / rows;

function grid(fn) {
  const out = [];
  for (let r = 0; r < rows; r++) {
    let line = "";
    for (let c = 0; c < cols; c++) {
      const x0 = Math.floor(c * cw);
      const x1 = Math.min(W, Math.ceil((c + 1) * cw));
      const y0 = Math.floor(r * chh);
      const y1 = Math.min(H, Math.ceil((r + 1) * chh));
      line += RAMP[Math.max(0, Math.min(9, fn(x0, x1, y0, y1)))];
    }
    out.push(line);
  }
  return out;
}

function print(title, lines) {
  console.log(title);
  for (const l of lines) console.log("|" + l + "|");
  console.log("");
}

console.log(`画布 ${W}x${H} → ${cols}列 x ${rows}行，单元 ${cw.toFixed(1)}x${chh.toFixed(1)}px；ramp "${RAMP}"`);

if (!fileB) {
  print(`亮度图  ${fileA}`, grid((x0, x1, y0, y1) => {
    let s = 0;
    let n = 0;
    for (let y = y0; y < y1; y++) for (let x = x0; x < x1; x++) { s += bufA[y * W + x]; n++; }
    return Math.round((s / n / 255) * 9);
  }));
} else {
  const bufB = await gray(fileB);
  if (bufB.length < W * H) {
    console.error(`参考帧像素不足：${bufB.length} < ${W * H}`);
    process.exit(1);
  }
  const d = new Uint8Array(W * H);
  for (let i = 0; i < W * H; i++) d[i] = Math.abs(bufA[i] - bufB[i]);

  if (!solidOnly)
    print(`立绘层 · 平均强度  (${fileA} − ${fileB})`, grid((x0, x1, y0, y1) => {
      let s = 0;
      let n = 0;
      for (let y = y0; y < y1; y++) for (let x = x0; x < x1; x++) { s += d[y * W + x]; n++; }
      return Math.round((s / n / 255) * 9);
    }));

  print(`立绘层 · 实体占比 (>96)`, grid((x0, x1, y0, y1) => {
    let k = 0;
    let n = 0;
    for (let y = y0; y < y1; y++) for (let x = x0; x < x1; x++) { if (d[y * W + x] > 96) k++; n++; }
    return Math.round((k / n) * 9);
  }));
}