import { mkdtempSync, writeFileSync } from 'node:fs';
import { tmpdir } from 'node:os';
import { join } from 'node:path';
import { inflateSync } from 'node:zlib';
import { describe, expect, it } from 'vitest';
import { renderModelThumbnail } from '../src/models/model-thumbnail';

/**
 * 缩略图**贴图采样**测试。
 *
 * 背景（真实故障）：缩略图渲染器原先刻意不解码 baseColorTexture，只用
 * `baseColorFactor` 上色；而 MMD（PMX 转换）模型的 baseColorFactor 基本全是白色，
 * 于是缩略图全是"白模"——列表页与审核面板看到的都是白色模型，用户报的正是这个。
 * 现在渲染器内置 PNG 解码并逐像素采样贴图，这里锁住行为。
 */

const dir = mkdtempSync(join(tmpdir(), 'opendance-thumb-tex-'));

function write(name: string, content: Buffer): string {
  const path = join(dir, name);
  writeFileSync(path, content);
  return path;
}

/** 12 字节头 + JSON chunk + BIN chunk */
function buildGlb(json: unknown, bin: Buffer): Buffer {
  const jsonRaw = Buffer.from(JSON.stringify(json), 'utf8');
  const jsonChunk = Buffer.concat([jsonRaw, Buffer.alloc((4 - (jsonRaw.length % 4)) % 4, 0x20)]);
  const binChunk = Buffer.concat([bin, Buffer.alloc((4 - (bin.length % 4)) % 4)]);
  const chunks: Buffer[] = [];
  const header = Buffer.alloc(12);
  header.write('glTF', 0, 'ascii');
  header.writeUInt32LE(2, 4);
  chunks.push(header);
  const jsonHeader = Buffer.alloc(8);
  jsonHeader.writeUInt32LE(jsonChunk.length, 0);
  jsonHeader.writeUInt32LE(0x4e4f534a, 4);
  chunks.push(jsonHeader, jsonChunk);
  const binHeader = Buffer.alloc(8);
  binHeader.writeUInt32LE(binChunk.length, 0);
  binHeader.writeUInt32LE(0x004e4942, 4);
  chunks.push(binHeader, binChunk);
  const out = Buffer.concat(chunks);
  out.writeUInt32LE(out.length, 8);
  return out;
}

function float32Buffer(values: number[]): Buffer {
  const buffer = Buffer.alloc(values.length * 4);
  values.forEach((value, index) => buffer.writeFloatLE(value, index * 4));
  return buffer;
}

function uint16Buffer(values: number[]): Buffer {
  const buffer = Buffer.alloc(values.length * 2);
  values.forEach((value, index) => buffer.writeUInt16LE(value, index * 2));
  return buffer;
}

/* ------------------------------------------------------------ 贴图夹具 */

/** 2x2 纯红（colorType 6，带 alpha=255） */
const RED_PNG = Buffer.from(
  'iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAYAAABytg0kAAAAEUlEQVR4nGP4z8DwH4QZYAwAR8oH+WdZbrcAAAAASUVORK5CYII=',
  'base64',
);
/** 2x2 纯绿（colorType 2，无 alpha） */
const GREEN_PNG = Buffer.from(
  'iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAIAAAD91JpzAAAAD0lEQVR4nGNg+M8AQhAKABvyA/1tVLjHAAAAAElFTkSuQmCC',
  'base64',
);
/** 2x2 全透明（RGBA 的 alpha=0） */
const TRANSPARENT_PNG = Buffer.from(
  'iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAYAAABytg0kAAAAEUlEQVR4nGP4z8DAAMIMMAYAKegD/QE6Y34AAAAASUVORK5CYII=',
  'base64',
);

interface QuadOptions {
  texture?: Buffer;
  mimeType?: string;
  baseColorFactor?: number[];
  alphaMode?: string;
}

/** 一个正对相机（+Z）的方形面片，UV 铺满贴图；baseColorFactor 默认纯白（MMD 的常见情况） */
function texturedQuadGlb(options: QuadOptions = {}): Buffer {
  const positions = [-1, -1, 0, 1, -1, 0, 1, 1, 0, -1, 1, 0];
  const uvs = [0, 1, 1, 1, 1, 0, 0, 0];
  const indices = [0, 1, 2, 0, 2, 3];
  const posBin = float32Buffer(positions);
  const uvBin = float32Buffer(uvs);
  const idxBin = uint16Buffer(indices);
  const image = options.texture ?? RED_PNG;
  const bin = Buffer.concat([posBin, uvBin, idxBin, image]);
  const imageOffset = posBin.length + uvBin.length + idxBin.length;

  const json = {
    asset: { version: '2.0' },
    scene: 0,
    scenes: [{ nodes: [0] }],
    nodes: [{ mesh: 0 }],
    meshes: [{ primitives: [{ attributes: { POSITION: 0, TEXCOORD_0: 1 }, indices: 2, material: 0 }] }],
    materials: [
      {
        pbrMetallicRoughness: {
          baseColorFactor: options.baseColorFactor ?? [1, 1, 1, 1],
          baseColorTexture: { index: 0 },
        },
        ...(options.alphaMode ? { alphaMode: options.alphaMode, alphaCutoff: 0.5 } : {}),
      },
    ],
    textures: [{ source: 0 }],
    images: [{ bufferView: 3, mimeType: options.mimeType ?? 'image/png' }],
    accessors: [
      { bufferView: 0, componentType: 5126, count: 4, type: 'VEC3' },
      { bufferView: 1, componentType: 5126, count: 4, type: 'VEC2' },
      { bufferView: 2, componentType: 5123, count: 6, type: 'SCALAR' },
    ],
    bufferViews: [
      { buffer: 0, byteOffset: 0, byteLength: posBin.length },
      { buffer: 0, byteOffset: posBin.length, byteLength: uvBin.length },
      { buffer: 0, byteOffset: posBin.length + uvBin.length, byteLength: idxBin.length },
      { buffer: 0, byteOffset: imageOffset, byteLength: image.length },
    ],
    buffers: [{ byteLength: bin.length }],
  };
  return buildGlb(json, bin);
}

/** 解 PNG（我们自己写的编码器：8 位 RGB、filter=0），返回平均 RGB */
function averageColor(png: Buffer): { r: number; g: number; b: number; nonBackground: number } {
  let offset = 8;
  let width = 0;
  let height = 0;
  const idat: Buffer[] = [];
  while (offset + 8 <= png.length) {
    const length = png.readUInt32BE(offset);
    const type = png.toString('ascii', offset + 4, offset + 8);
    const data = png.subarray(offset + 8, offset + 8 + length);
    if (type === 'IHDR') {
      width = data.readUInt32BE(0);
      height = data.readUInt32BE(4);
      expect(data[8]).toBe(8);
      expect(data[9]).toBe(2);
      expect(data[12]).toBe(0);
    } else if (type === 'IDAT') {
      idat.push(Buffer.from(data));
    } else if (type === 'IEND') {
      break;
    }
    offset += 12 + length;
  }
  const raw = inflateSync(Buffer.concat(idat));
  let r = 0;
  let g = 0;
  let b = 0;
  let count = 0;
  let nonBackground = 0;
  for (let y = 0; y < height; y += 1) {
    const rowStart = y * (1 + width * 3);
    expect(raw[rowStart]).toBe(0); // filter=0
    for (let x = 0; x < width; x += 1) {
      const i = rowStart + 1 + x * 3;
      r += raw[i];
      g += raw[i + 1];
      b += raw[i + 2];
      count += 1;
      // 默认背景是 [24,26,32]（深色）；明显偏离即视为主体像素
      if (Math.abs(raw[i] - 24) > 12 || Math.abs(raw[i + 1] - 26) > 12 || Math.abs(raw[i + 2] - 32) > 12) {
        nonBackground += 1;
      }
    }
  }
  return { r: r / count, g: g / count, b: b / count, nonBackground };
}

async function render(glb: Buffer, name: string, extra: Record<string, unknown> = {}) {
  const result = await renderModelThumbnail(write(name, glb), { size: 128, ...extra });
  expect(result).not.toBeNull();
  return averageColor((result as { png: Buffer }).png);
}

/* ------------------------------------------------------------------ 测试 */

describe('缩略图贴图采样', () => {
  it('baseColorFactor 全白时也按贴图上色（回归：不再输出"白模"）', async () => {
    const color = await render(texturedQuadGlb(), 'red.glb');
    expect(color.nonBackground).toBeGreaterThan(0);
    // 贴图是纯红：主体像素整体应明显偏红
    expect(color.r).toBeGreaterThan(color.g + 20);
    expect(color.r).toBeGreaterThan(color.b + 20);
  });

  it('colorType 2（无 alpha 通道）的 PNG 也能解码', async () => {
    const color = await render(texturedQuadGlb({ texture: GREEN_PNG }), 'green.glb');
    expect(color.g).toBeGreaterThan(color.r + 20);
    expect(color.g).toBeGreaterThan(color.b + 20);
  });

  it('OPAQUE：忽略贴图 alpha（MMD 语义，alpha=0 也照样画出来）', async () => {
    const color = await render(
      texturedQuadGlb({ texture: TRANSPARENT_PNG, baseColorFactor: [0.9, 0.1, 0.1, 1] }),
      'opaque.glb',
    );
    expect(color.nonBackground).toBeGreaterThan(0);
    expect(color.r).toBeGreaterThan(color.g + 20);
  });

  it('MASK：alpha 低于阈值的主体像素被丢弃（只剩背景）', async () => {
    const color = await render(
      texturedQuadGlb({ texture: TRANSPARENT_PNG, baseColorFactor: [0.9, 0.1, 0.1, 1], alphaMode: 'MASK' }),
      'mask.glb',
    );
    expect(color.nonBackground).toBe(0);
  });

  it('贴图解码失败时回退 baseColorFactor 纯色，且不抛错', async () => {
    const broken = Buffer.from('这不是 PNG 数据', 'utf8');
    const color = await render(
      texturedQuadGlb({ texture: broken, baseColorFactor: [0.1, 0.1, 0.9, 1] }),
      'broken.glb',
    );
    expect(color.nonBackground).toBeGreaterThan(0);
    expect(color.b).toBeGreaterThan(color.r + 20);
  });

  it('默认视角是正面（相机在 +Z）：+Z 面颜色明显主导', async () => {
    // 面片正对 +Z，默认视角下必须看得见（若默认看背面，主体像素会接近 0）
    const color = await render(texturedQuadGlb(), 'front.glb');
    expect(color.nonBackground).toBeGreaterThan(128 * 128 * 0.05);
  });
});