import { test } from 'node:test';
import assert from 'node:assert/strict';
import { PNG } from 'pngjs';
import { splitSheet, reassemble, pixelsEqual, verifySheet } from '../ui-migration/frame-io.mjs';

/** 造一张 w×h 网格的测试图，每格填不同颜色，便于验证切分位置 */
function makeSheet(cols, rows, cellW, cellH) {
  const png = new PNG({ width: cols * cellW, height: rows * cellH });
  for (let r = 0; r < rows; r++) {
    for (let c = 0; c < cols; c++) {
      const idx = r * cols + c;               // 行优先编号
      for (let y = 0; y < cellH; y++) {
        for (let x = 0; x < cellW; x++) {
          const o = ((r * cellH + y) * png.width + (c * cellW + x)) << 2;
          png.data[o] = (idx * 20) & 0xff;     // R 编码帧号，便于断言
          png.data[o + 1] = 0x40;
          png.data[o + 2] = 0x80;
          png.data[o + 3] = 0xff;
        }
      }
    }
  }
  return PNG.sync.write(png);
}

const IMG = { id: 1, w_all: 60, h_all: 40, w: 3, h: 2, frame_all: 6, bmp: 'test.png', w1: 20, h1: 20 };

test('splitSheet 切出 frame_all 张，尺寸为单帧尺寸', () => {
  const frames = splitSheet(makeSheet(3, 2, 20, 20), IMG);
  assert.equal(frames.length, 6);
  const first = PNG.sync.read(frames[0]);
  assert.equal(first.width, 20);
  assert.equal(first.height, 20);
});

test('splitSheet 按行优先取帧：下标 0..5 的 R 通道依次为 0,20,40,60,80,100', () => {
  const frames = splitSheet(makeSheet(3, 2, 20, 20), IMG);
  const reds = frames.map((b) => PNG.sync.read(b).data[0]);
  assert.deepEqual(reds, [0, 20, 40, 60, 80, 100],
    '若切成列优先，顺序会变为 0,60,20,80,40,100');
});

test('reassemble(splitSheet(x)) 的像素与 x 完全一致（完全验证的核心不变量）', () => {
  const sheet = makeSheet(3, 2, 20, 20);
  const back = reassemble(splitSheet(sheet, IMG), IMG);
  assert.equal(pixelsEqual(sheet, back), true);
});

test('pixelsEqual 对像素不同的图返回 false', () => {
  const a = makeSheet(3, 2, 20, 20);
  const bPng = PNG.sync.read(a);
  bPng.data[0] = (bPng.data[0] + 1) & 0xff;   // 改一个字节
  assert.equal(pixelsEqual(a, PNG.sync.write(bPng)), false);
});

test('pixelsEqual 忽略编码差异：同像素不同压缩等级仍为 true', () => {
  const src = PNG.sync.read(makeSheet(3, 2, 20, 20));
  const enc0 = PNG.sync.write(src, { deflateLevel: 0 });
  const enc9 = PNG.sync.write(src, { deflateLevel: 9 });
  assert.notEqual(Buffer.compare(enc0, enc9), 0, '前提：两种编码的文件字节确实不同');
  assert.equal(pixelsEqual(enc0, enc9), true, '但像素数据必须判为相同');
});

test('verifySheet 对正常图返回 ok', () => {
  assert.deepEqual(verifySheet(makeSheet(3, 2, 20, 20), IMG), { ok: true });
});

test('verifySheet 对尺寸与网格声明不符的图返回失败原因', () => {
  const wrong = makeSheet(2, 2, 20, 20);   // 实际 40x40，但 IMG 声明 60x40
  const r = verifySheet(wrong, IMG);
  assert.equal(r.ok, false);
  assert.match(r.reason, /尺寸/);
});