const express = require("express");
const fs = require("fs/promises");
const path = require("path");
const crypto = require("crypto");
const statsDb = require("./stats-db");

const app = express();
const PORT = process.env.PORT || 5180;
const DB_PATH = path.join(__dirname, "data", "shaders.json");
const THUMB_DIR = path.join(__dirname, "data", "thumbnails");

app.use(express.json({ limit: "4mb" }));
app.use(express.static(__dirname));

async function ensureDb() {
  await fs.mkdir(path.dirname(DB_PATH), { recursive: true });
  try {
    await fs.access(DB_PATH);
  } catch {
    await fs.writeFile(DB_PATH, "[]", "utf8");
  }
}

async function ensureThumbnailsDir() {
  await fs.mkdir(THUMB_DIR, { recursive: true });
}

function thumbPath(id) {
  return path.join(THUMB_DIR, `${id}.png`);
}

async function thumbFileExists(id) {
  try {
    await fs.access(thumbPath(id));
    return true;
  } catch {
    return false;
  }
}

function downloadFilenameBase(name) {
  const s = String(name || "shader").trim() || "shader";
  return s.replace(/[\\/:*?"<>|]/g, "_").slice(0, 120);
}

function decodePngBase64(s) {
  if (!s || typeof s !== "string") return null;
  const t = s.trim();
  const m = /^data:image\/png;base64,(.+)$/i.exec(t);
  const b64 = m ? m[1] : t.replace(/\s/g, "");
  try {
    return Buffer.from(b64, "base64");
  } catch {
    return null;
  }
}

function isPngBuffer(buf) {
  return (
    buf &&
    buf.length >= 8 &&
    buf[0] === 0x89 &&
    buf[1] === 0x50 &&
    buf[2] === 0x4e &&
    buf[3] === 0x47 &&
    buf[4] === 0x0d &&
    buf[5] === 0x0a &&
    buf[6] === 0x1a &&
    buf[7] === 0x0a
  );
}

async function readDb() {
  await ensureDb();
  const raw = await fs.readFile(DB_PATH, "utf8");
  return JSON.parse(raw);
}

async function writeDb(list) {
  await ensureDb();
  await fs.writeFile(DB_PATH, JSON.stringify(list, null, 2), "utf8");
}

function extractFunctionSection(code) {
  const endMarker = code.indexOf("void ANGLE__0_main");
  const end = endMarker >= 0 ? endMarker : code.length;
  const firstFn = code.search(
    /(metal::float[234](x2)?|float|void)\s+[A-Za-z_][A-Za-z0-9_]*\s*\([^)]*\)\s*\{/m
  );
  if (firstFn < 0 || firstFn >= end) return "";
  return code.slice(firstFn, end);
}

function isAngleLike(code) {
  return (
    code.includes("_umainImage") &&
    (code.includes("ANGLE_") ||
      code.includes("metal::") ||
      code.includes("[[function_constant") ||
      code.includes("float2") ||
      code.includes("float3"))
  );
}

function extractFunctionBlocks(code) {
  const blocks = [];
  const sig = /(?:^|\n)\s*(?:void|float|vec[234]|mat[234]|float[234](?:x[234])?)\s+([A-Za-z_][A-Za-z0-9_]*)\s*\([^;]*\)\s*\{/g;
  let m;
  while ((m = sig.exec(code)) !== null) {
    const name = m[1];
    if (name === "main0" || name === "ANGLE__0_main") continue;
    let i = code.indexOf("{", m.index);
    if (i < 0) continue;
    let depth = 0;
    let end = -1;
    for (let p = i; p < code.length; p++) {
      const ch = code[p];
      if (ch === "{") depth++;
      else if (ch === "}") {
        depth--;
        if (depth === 0) {
          end = p + 1;
          break;
        }
      }
    }
    if (end > i) {
      blocks.push(code.slice(m.index, end));
      sig.lastIndex = end;
    }
  }
  return blocks;
}

function buildFunctionMap(blocks) {
  const map = new Map();
  for (const block of blocks) {
    const m = block.match(/^\s*(?:void|float|vec[234]|mat[234]|int|uint)\s+([A-Za-z_][A-Za-z0-9_]*)\s*\(/m);
    if (!m) continue;
    map.set(m[1], block);
  }
  return map;
}

function collectFunctionDependencies(fnMap, roots) {
  const keep = new Set();
  const queue = [...roots];
  while (queue.length) {
    const name = queue.shift();
    if (keep.has(name)) continue;
    const block = fnMap.get(name);
    if (!block) continue;
    keep.add(name);
    const callPattern = /\b([A-Za-z_][A-Za-z0-9_]*)\s*\(/g;
    let m;
    while ((m = callPattern.exec(block)) !== null) {
      const callee = m[1];
      if (fnMap.has(callee) && !keep.has(callee)) queue.push(callee);
    }
  }
  return keep;
}

function convertAngleLikeToGlsl(code) {
  let s = code;
  const cut = s.indexOf("fragment ANGLE_FragmentOut");
  if (cut > 0) s = s.slice(0, cut);

  s = s
    .replace(/metal::fast::normalize/g, "normalize")
    .replace(/metal::/g, "")
    .replace(/\[\[[^\]]+\]\]/g, "")
    .replace(/\bthread\b/g, "")
    .replace(/\bconstant\b/g, "")
    .replace(/\bprecise::tanh\b/g, "tanh")
    .replace(/\bfloat2x2\b/g, "mat2")
    .replace(/\bfloat3x3\b/g, "mat3")
    .replace(/\bfloat4x4\b/g, "mat4")
    .replace(/\bfloat2\b/g, "vec2")
    .replace(/\bfloat3\b/g, "vec3")
    .replace(/\bfloat4\b/g, "vec4")
    .replace(/\bint2\b/g, "ivec2")
    .replace(/\bint3\b/g, "ivec3")
    .replace(/\bint4\b/g, "ivec4")
    .replace(/\buint2\b/g, "uvec2")
    .replace(/\buint3\b/g, "uvec3")
    .replace(/\buint4\b/g, "uvec4")
    .replace(/\buint32_t\b/g, "uint")
    .replace(/\bANGLE_userUniforms\._uiResolution\b/g, "iResolution")
    .replace(/\bANGLE_userUniforms\._uiTime\b/g, "iTime")
    .replace(/\bANGLE_userUniforms\._uiMouse\b/g, "iMouse")
    .replace(/\bANGLE_userUniforms\./g, "")
    .replace(/ANGLE_texture\(\s*ANGLE_textureEnvs\._uiChannel0\s*,\s*([^)]+)\)/g, "texture(iChannel0, $1)")
    .replace(/ANGLE_texture\(\s*ANGLE_textureEnvs\._uiChannel1\s*,\s*([^)]+)\)/g, "texture(iChannel1, $1)")
    .replace(/ANGLE_texture\(\s*ANGLE_textureEnvs\._uiChannel2\s*,\s*([^)]+)\)/g, "texture(iChannel2, $1)")
    .replace(/ANGLE_texture\(\s*ANGLE_textureEnvs\._uiChannel3\s*,\s*([^)]+)\)/g, "texture(iChannel3, $1)")
    .replace(/ANGLE_texelFetch\(\s*ANGLE_textureEnvs\._uiChannel0\s*,\s*([^,]+)\s*,\s*([^)]+)\)/g, "texelFetch(iChannel0, $1, $2)")
    .replace(/ANGLE_texelFetch\(\s*ANGLE_textureEnvs\._uiChannel1\s*,\s*([^,]+)\s*,\s*([^)]+)\)/g, "texelFetch(iChannel1, $1, $2)")
    .replace(/ANGLE_texelFetch\(\s*ANGLE_textureEnvs\._uiChannel2\s*,\s*([^,]+)\s*,\s*([^)]+)\)/g, "texelFetch(iChannel2, $1, $2)")
    .replace(/ANGLE_texelFetch\(\s*ANGLE_textureEnvs\._uiChannel3\s*,\s*([^,]+)\s*,\s*([^)]+)\)/g, "texelFetch(iChannel3, $1, $2)")
    .replace(/ANGLE_texture\([^)]*\)/g, "vec4(0.0)")
    .replace(/ANGLE_texelFetch\([^)]*\)/g, "vec4(0.0)")
    .replace(/\bANGLE_mod\(/g, "mod(")
    .replace(/\bANGLE_out\(([^)]+)\)/g, "$1")
    .replace(/\bANGLE_swizzle_ref\(([^)]+)\)/g, "$1")
    .replace(/\bANGLE_elem_ref\(([^)]+)\)/g, "$1")
    .replace(/\bANGLE_addressof\(([^)]+)\)/g, "$1")
    .replace(/\bANGLE_UserUniforms\s*&\s*ANGLE_userUniforms\s*,?/g, "")
    .replace(/\bANGLE_TextureEnvs\s*&\s*ANGLE_textureEnvs\s*,?/g, "")
    .replace(/\bANGLE_NonConstGlobals\s*&\s*ANGLE_nonConstGlobals\s*,?/g, "")
    .replace(/\(\s*,/g, "(")
    .replace(/,\s*,/g, ",")
    .replace(/,\s*\)/g, ")")
    .replace(/\bANGLE_nonConstGlobals\./g, "")
    .replace(/(\d+\.\d+|\d+)f\b/g, "$1")
    .replace(/;\s*;/g, ";");

  s = s.replace(/void\s+_umainImage\s*\([^)]*\)/g, "void _umainImage(out vec4 _ufragColor, vec2 _ufragCoord)");

  const fnBlocks = extractFunctionBlocks(s).filter((b) =>
    /(ANGLE_sc|ANGLE_sd|_u|mainImage|ANGLE_loopForwardProgress|_umainImage)/.test(b)
  );
  const fnMap = buildFunctionMap(fnBlocks);
  const keepNames = collectFunctionDependencies(fnMap, ["mainImage", "_umainImage"]);
  if (fnMap.has("ANGLE_loopForwardProgress")) keepNames.add("ANGLE_loopForwardProgress");
  const blocks = [...fnMap.entries()]
    .filter(([name]) => keepNames.has(name))
    .map(([, block]) => block);

  if (!blocks.length || !s.includes("_umainImage")) return "";

  const hasMainImage = blocks.some((b) => /void\s+mainImage\s*\(/.test(b));
  const withoutDupLoop = [];
  let seenLoop = false;
  for (const b of blocks) {
    if (/void\s+ANGLE_loopForwardProgress\s*\(/.test(b)) {
      if (seenLoop) continue;
      seenLoop = true;
      withoutDupLoop.push("void ANGLE_loopForwardProgress() {}");
      continue;
    }
    withoutDupLoop.push(b);
  }
  if (!hasMainImage) {
    withoutDupLoop.push("void mainImage(out vec4 fragColor, in vec2 fragCoord) { _umainImage(fragColor, fragCoord); }");
  }

  return withoutDupLoop.join("\n\n");
}

/** Strip ShaderToy export preamble (uniform iResolution…), fix `}uniform` gluing, keep first mainImage only. */
function sanitizeShadertoyUserGlsl(code) {
  if (!code || typeof code !== "string") return "";
  let s = code.replace(/\r\n/g, "\n");
  s = s.replace(/\}\s*(?=uniform\s+)/g, "}\n");
  const lines = s.split("\n");
  s = lines
    .filter((line) => !/^\s*uniform\s+/.test(line.trim()))
    .join("\n");
  s = s.replace(/^\s+/, "").replace(/\s+$/, "");

  const re = /\bvoid\s+mainImage\s*\(/g;
  const matches = [...s.matchAll(re)];
  if (matches.length <= 1) return s;

  const start = matches[0].index;
  const braceStart = s.indexOf("{", s.indexOf("(", start));
  if (braceStart < 0) return s;
  let depth = 0;
  let i = braceStart;
  for (; i < s.length; i++) {
    const ch = s[i];
    if (ch === "{") depth++;
    else if (ch === "}") {
      depth--;
      if (depth === 0) {
        i++;
        break;
      }
    }
  }
  const firstMain = s.slice(start, i);
  const prefix = s.slice(0, start).trimEnd();
  return (prefix ? `${prefix}\n\n` : "") + firstMain.trim();
}

function normalizeIncomingCode(code) {
  if (!code || typeof code !== "string") return { error: "code 不能为空", normalized: "" };
  if (isAngleLike(code)) {
    const converted = convertAngleLikeToGlsl(code);
    if (!converted) {
      return { error: "自动解构失败：请检查粘贴内容是否完整。", normalized: "" };
    }
    return { error: "", normalized: converted };
  }
  const sanitized = sanitizeShadertoyUserGlsl(code);
  if (!sanitized.includes("mainImage")) {
    return { error: "code 必须包含 mainImage", normalized: "" };
  }
  return { error: "", normalized: sanitized };
}

async function autoNormalizeStoredShaders() {
  const shaders = await readDb();
  let changed = false;
  const next = shaders.map((item) => {
    const code = String(item.code || "");
    const angle = isAngleLike(code) || code.includes("struct ANGLE_");
    if (angle) {
      const { error, normalized } = normalizeIncomingCode(code);
      if (!error && normalized && normalized !== code) {
        changed = true;
        return {
          ...item,
          code: normalized,
          updatedAt: new Date().toISOString(),
          sourceFormat: "angle-metal-auto-converted",
        };
      }
      return item;
    }
    const { error, normalized } = normalizeIncomingCode(code);
    if (!error && normalized && normalized !== code) {
      changed = true;
      const fixTag = item.sourceFormat === "angle-metal-auto-converted" ? { sourceFormat: "glsl" } : {};
      return {
        ...item,
        code: normalized,
        updatedAt: new Date().toISOString(),
        ...fixTag,
      };
    }
    return item;
  });
  if (changed) await writeDb(next);
}

app.get("/api/shaders", async (_req, res) => {
  try {
    await ensureThumbnailsDir();
    let shaders = await readDb();
    shaders = shaders.map((item) => {
      const raw = String(item.code || "");
      const { error, normalized } = normalizeIncomingCode(raw);
      if (error || !normalized) return item;
      if (normalized === raw) return item;
      const next = { ...item, code: normalized };
      if (isAngleLike(raw)) next.sourceFormat = "angle-metal-auto-converted";
      return next;
    });
    const visitorId = String(_req.get("x-visitor-id") || "").trim();
    const out = await Promise.all(
      shaders.map(async (item) => {
        const has = await thumbFileExists(item.id);
        const thumbnailUrl = has
          ? `/api/shaders/${encodeURIComponent(item.id)}/thumbnail`
          : null;
        const merged = statsDb.mergeItem({ ...item, thumbnailUrl }, visitorId);
        return merged;
      })
    );
    res.json(out);
  } catch {
    res.status(500).json({ error: "读取失败" });
  }
});

app.get("/api/shaders/:id/download", async (req, res) => {
  try {
    const shaders = await readDb();
    const item = shaders.find((it) => it.id === req.params.id);
    if (!item) {
      return res.status(404).json({ error: "未找到该 shader" });
    }
    const raw =
      item.sourceGlsl != null && String(item.sourceGlsl).length > 0
        ? String(item.sourceGlsl)
        : String(item.code || "");
    const base = downloadFilenameBase(item.name);
    const fullName = `${base}.glsl`;
    const asciiName = `${base.replace(/[^\x20-\x7e]/g, "_")}.glsl`;
    res.setHeader("Content-Type", "text/plain; charset=utf-8");
    res.setHeader(
      "Content-Disposition",
      `attachment; filename="${asciiName}"; filename*=UTF-8''${encodeURIComponent(fullName)}`
    );
    res.send(raw);
  } catch {
    res.status(500).json({ error: "导出失败" });
  }
});

app.post("/api/shaders", async (req, res) => {
  const { name, author = "unknown", code } = req.body || {};
  if (!name || typeof name !== "string") {
    return res.status(400).json({ error: "name 必填" });
  }
  const { error: parseError, normalized } = normalizeIncomingCode(code);
  if (parseError) {
    return res.status(400).json({ error: parseError });
  }

  try {
    const shaders = await readDb();
    const sourceGlsl = typeof code === "string" ? code : "";
    const item = {
      id: crypto.randomUUID(),
      name: name.trim(),
      author: String(author || "unknown").trim() || "unknown",
      code: normalized,
      sourceGlsl,
      views: Math.floor(3000 + Math.random() * 22000),
      likes: Math.floor(40 + Math.random() * 700),
      createdAt: new Date().toISOString(),
      sourceFormat: isAngleLike(code) ? "angle-metal-auto-converted" : "glsl",
    };
    shaders.unshift(item);
    await writeDb(shaders);
    await statsDb.insertStats(item.id, item.views, item.likes);
    res.status(201).json(statsDb.mergeItem(item, ""));
  } catch {
    res.status(500).json({ error: "保存失败" });
  }
});

app.post("/api/shaders/:id/view", async (req, res) => {
  try {
    const shaders = await readDb();
    const item = shaders.find((it) => it.id === req.params.id);
    if (!item) {
      return res.status(404).json({ error: "未找到该 shader" });
    }
    const row = await statsDb.incrementView(item.id, item);
    res.json({ views: row.views, likes: row.likes });
  } catch {
    res.status(500).json({ error: "更新失败" });
  }
});

app.post("/api/shaders/:id/like", async (req, res) => {
  const visitorId = String((req.body && req.body.visitorId) || "").trim();
  if (!visitorId) {
    return res.status(400).json({ error: "visitorId 必填" });
  }
  try {
    const shaders = await readDb();
    const item = shaders.find((it) => it.id === req.params.id);
    if (!item) {
      return res.status(404).json({ error: "未找到该 shader" });
    }
    const out = await statsDb.tryLike(item.id, visitorId, item);
    res.json(out);
  } catch {
    res.status(500).json({ error: "点赞失败" });
  }
});

app.get("/api/shaders/:id/thumbnail", async (req, res) => {
  try {
    const p = thumbPath(req.params.id);
    await fs.access(p);
    res.setHeader("Content-Type", "image/png");
    res.setHeader("Cache-Control", "public, max-age=86400");
    res.sendFile(path.resolve(p));
  } catch {
    res.status(404).end();
  }
});

app.post("/api/shaders/:id/thumbnail", async (req, res) => {
  const { pngBase64 } = req.body || {};
  const buf = decodePngBase64(pngBase64);
  if (!buf || buf.length < 32) {
    return res.status(400).json({ error: "无效 PNG 数据" });
  }
  if (!isPngBuffer(buf)) {
    return res.status(400).json({ error: "必须是 PNG" });
  }
  if (buf.length > 2 * 1024 * 1024) {
    return res.status(400).json({ error: "缩略图过大" });
  }
  try {
    const shaders = await readDb();
    const idx = shaders.findIndex((it) => it.id === req.params.id);
    if (idx < 0) {
      return res.status(404).json({ error: "未找到该 shader" });
    }
    await ensureThumbnailsDir();
    await fs.writeFile(thumbPath(req.params.id), buf);
    const thumbnailAt = new Date().toISOString();
    shaders[idx] = { ...shaders[idx], thumbnailAt };
    await writeDb(shaders);
    const thumbnailUrl = `/api/shaders/${encodeURIComponent(req.params.id)}/thumbnail`;
    res.json({ ok: true, thumbnailUrl, thumbnailAt });
  } catch {
    res.status(500).json({ error: "保存缩略图失败" });
  }
});

app.delete("/api/shaders/:id", async (req, res) => {
  try {
    const shaders = await readDb();
    const next = shaders.filter((it) => it.id !== req.params.id);
    if (next.length === shaders.length) {
      return res.status(404).json({ error: "未找到该 shader" });
    }
    await writeDb(next);
    await statsDb.deleteStats(req.params.id);
    await ensureThumbnailsDir();
    try {
      await fs.unlink(thumbPath(req.params.id));
    } catch (_) {
      /* no thumb */
    }
    res.status(204).end();
  } catch {
    res.status(500).json({ error: "删除失败" });
  }
});

async function start() {
  await ensureDb();
  await statsDb.load();
  const initialList = await readDb();
  await statsDb.migrateIfEmpty(initialList);
  try {
    await autoNormalizeStoredShaders();
  } catch (_) {}
  app.listen(PORT, () => {
    console.log(`Server running: http://localhost:${PORT}`);
  });
}

start().catch((err) => {
  console.error(err);
  process.exit(1);
});