import express, { Request, Response } from 'express';
import cors from 'cors';
import { exec } from 'child_process';
import { promises as fs } from 'fs';
import { tmpdir } from 'os';
import { join } from 'path';
import { promisify } from 'util';

const execAsync = promisify(exec);
const app = express();
const PORT = process.env.PORT || 3456;

const EMSDK_PATH = process.env.EMSDK_PATH || `${process.env.HOME}/wasm-toolchains/emsdk`;
const SWIFTWASM_PATH = process.env.SWIFTWASM_PATH || `${process.env.HOME}/wasm-toolchains/swiftwasm`;

app.use(cors());
app.use(express.json({ limit: '5mb' }));
app.use(express.static('public'));

interface CompileRequest {
  code: string;
  flags?: string;
}

interface Diagnostic {
  line?: number;
  column?: number;
  message: string;
  severity: 'error' | 'warning' | 'note';
  file?: string;
}

function getEmsdkEnvCommand(): string {
  return `source "${EMSDK_PATH}/emsdk_env.sh"`;
}

function getSwiftPath(): string {
  return `${SWIFTWASM_PATH}/usr/bin`;
}

async function findCompiler(compilerName: string, extraPaths: string[] = []): Promise<string | null> {
  const paths = [...extraPaths, ...(process.env.PATH?.split(':') || [])];
  for (const p of paths) {
    try {
      await fs.access(join(p, compilerName));
      return join(p, compilerName);
    } catch { /* ignore */ }
  }
  return null;
}

async function findInPathsOnly(compilerName: string, searchPaths: string[]): Promise<string | null> {
  for (const p of searchPaths) {
    try {
      await fs.access(join(p, compilerName));
      return join(p, compilerName);
    } catch { /* ignore */ }
  }
  return null;
}

async function canTargetWasm32(swiftcPath: string): Promise<boolean> {
  try {
    const testDir = await fs.mkdtemp(join(tmpdir(), 'swift-wasm-test-'));
    const testFile = join(testDir, 'test.swift');
    await fs.writeFile(testFile, 'print("hello")\n');
    await execAsync(`"${swiftcPath}" -target wasm32-unknown-wasi -o "${join(testDir, 'test.wasm')}" "${testFile}"`, { timeout: 15000 });
    await fs.rm(testDir, { recursive: true, force: true }).catch(() => { });
    return true;
  } catch {
    return false;
  }
}

function parseDiagnostics(stderr: string, lang: 'cpp' | 'swift'): Diagnostic[] {
  const diagnostics: Diagnostic[] = [];
  if (!stderr) return diagnostics;
  const lines = stderr.split('\n');

  if (lang === 'cpp') {
    // emcc/clang: file.cpp:12:34: error: message
    const re = /^(.+?):(\d+):(\d+):\s*(error|warning|note):\s*(.+)$/;
    for (const line of lines) {
      const m = line.match(re);
      if (m) {
        diagnostics.push({
          file: m[1],
          line: parseInt(m[2], 10),
          column: parseInt(m[3], 10),
          severity: m[4] as Diagnostic['severity'],
          message: m[5],
        });
      }
    }
  } else {
    // swiftc: file.swift:12:34: error: message
    const re = /^(.+?):(\d+):(\d+):\s*(error|warning|note):\s*(.+)$/;
    for (const line of lines) {
      const m = line.match(re);
      if (m) {
        diagnostics.push({
          file: m[1],
          line: parseInt(m[2], 10),
          column: parseInt(m[3], 10),
          severity: m[4] as Diagnostic['severity'],
          message: m[5],
        });
      }
    }
  }
  return diagnostics;
}

function parseWasmExportsImports(wasmBytes: Buffer): { exports: any[]; imports: any[]; memories: any[] } {
  const result = { exports: [] as any[], imports: [] as any[], memories: [] as any[] };
  let pos = 8; // skip magic + version
  while (pos < wasmBytes.length) {
    const id = wasmBytes[pos++];
    if (id > 11) break;
    let len = 0;
    let shift = 0;
    while (true) {
      const b = wasmBytes[pos++];
      len |= (b & 0x7f) << shift;
      shift += 7;
      if ((b & 0x80) === 0) break;
    }
    const end = pos + len;
    if (id === 1) { // Type section - skip
    } else if (id === 2) { // Import section
      let count = readLeb(wasmBytes, pos);
      for (let i = 0; i < count.value; i++) {
        const mod = readString(wasmBytes, pos + count.bytes);
        const name = readString(wasmBytes, pos + count.bytes + mod.bytes);
        const kind = wasmBytes[pos + count.bytes + mod.bytes + name.bytes];
        result.imports.push({ module: mod.str, name: name.str, kind });
      }
    } else if (id === 7) { // Export section
      let count = readLeb(wasmBytes, pos);
      for (let i = 0; i < count.value; i++) {
        const name = readString(wasmBytes, pos + count.bytes);
        const kind = wasmBytes[pos + count.bytes + name.bytes];
        const idx = readLeb(wasmBytes, pos + count.bytes + name.bytes + 1);
        result.exports.push({ name: name.str, kind, index: idx.value });
      }
    } else if (id === 5) { // Memory section
      let count = readLeb(wasmBytes, pos);
      for (let i = 0; i < count.value; i++) {
        const flags = wasmBytes[pos + count.bytes];
        const min = readLeb(wasmBytes, pos + count.bytes + 1);
        result.memories.push({ flags, min: min.value });
      }
    }
    pos = end;
  }
  return result;
}

function readLeb(buf: Buffer, offset: number): { value: number; bytes: number } {
  let value = 0, shift = 0, bytes = 0;
  while (true) {
    const b = buf[offset + bytes++];
    value |= (b & 0x7f) << shift;
    shift += 7;
    if ((b & 0x80) === 0) break;
  }
  return { value, bytes };
}

function readString(buf: Buffer, offset: number): { str: string; bytes: number } {
  const len = readLeb(buf, offset);
  const str = buf.slice(offset + len.bytes, offset + len.bytes + len.value).toString('utf8');
  return { str, bytes: len.bytes + len.value };
}

// --- EXAMPLES ---
const examples = {
  cpp: [
    {
      name: 'Hello WASM',
      code: `#include <emscripten.h>
#include <stdio.h>

int main() {
  printf("Hello from C++ WASM!\\n");
  return 0;
}
`
    },
    {
      name: 'Exported Functions',
      code: `#include <emscripten.h>

extern "C" {
  EMSCRIPTEN_KEEPALIVE
  int add(int a, int b) {
    return a + b;
  }

  EMSCRIPTEN_KEEPALIVE
  int factorial(int n) {
    if (n <= 1) return 1;
    return n * factorial(n - 1);
  }
}

int main() {
  return 0;
}
`
    },
    {
      name: 'Memory & Pointer',
      code: `#include <emscripten.h>
#include <string.h>

extern "C" {
  EMSCRIPTEN_KEEPALIVE
  int sumArray(int* arr, int len) {
    int sum = 0;
    for (int i = 0; i < len; i++) sum += arr[i];
    return sum;
  }

  EMSCRIPTEN_KEEPALIVE
  void reverseInPlace(int* arr, int len) {
    for (int i = 0; i < len / 2; i++) {
      int tmp = arr[i];
      arr[i] = arr[len - 1 - i];
      arr[len - 1 - i] = tmp;
    }
  }
}

int main() { return 0; }
`
    },
    {
      name: 'Fibonacci Benchmark',
      code: `#include <emscripten.h>
#include <stdio.h>

extern "C" {
  EMSCRIPTEN_KEEPALIVE
  int fib(int n) {
    if (n <= 1) return n;
    return fib(n - 1) + fib(n - 2);
  }
}

int main() {
  for (int i = 0; i <= 20; i++) {
    printf("fib(%d) = %d\\n", i, fib(i));
  }
  return 0;
}
`
    }
  ],
  swift: [
    {
      name: 'Hello WASM',
      code: `print("Hello from Swift WASM!")
`
    },
    {
      name: 'Exported Functions',
      code: `@_cdecl("add")
public func add(a: Int32, b: Int32) -> Int32 {
    return a + b
}

@_cdecl("multiply")
public func multiply(a: Int32, b: Int32) -> Int32 {
    return a * b
}
`
    },
    {
      name: 'Recursive Factorial',
      code: `@_cdecl("factorial")
public func factorial(n: Int32) -> Int32 {
    if n <= 1 { return 1 }
    return n * factorial(n: n - 1)
}
`
    },
    {
      name: 'Array Sum',
      code: `@_cdecl("sumArray")
public func sumArray(ptr: UnsafePointer<Int32>, count: Int32) -> Int32 {
    var sum: Int32 = 0
    for i in 0..<count {
        sum += ptr[Int(i)]
    }
    return sum
}
`
    }
  ]
};

app.get('/api/examples', (_req: Request, res: Response) => {
  res.json(examples);
});

app.get('/api/status', async (_req: Request, res: Response) => {
  const emcc = await findCompiler('emcc', [`${EMSDK_PATH}/upstream/emscripten`]);
  const swiftc = await findCompiler('swiftc', [getSwiftPath()]);
  const swiftWasmCapable = swiftc ? await canTargetWasm32(swiftc) : false;
  res.json({
    emccAvailable: !!emcc,
    emccPath: emcc || null,
    swiftcAvailable: swiftWasmCapable,
    swiftcPath: swiftWasmCapable ? swiftc : null,
    emsdkPath: EMSDK_PATH,
    swiftwasmPath: SWIFTWASM_PATH
  });
});

app.post('/api/compile/cpp', async (req: Request, res: Response) => {
  const { code, flags } = req.body as CompileRequest;
  if (!code || typeof code !== 'string') {
    res.status(400).json({ success: false, error: 'Missing code field' });
    return;
  }

  const workDir = await fs.mkdtemp(join(tmpdir(), 'cpp-wasm-'));
  try {
    const emcc = await findInPathsOnly('emcc', [`${EMSDK_PATH}/upstream/emscripten`]);
    if (!emcc) {
      res.status(503).json({ success: false, error: 'emcc not found. Run: ./scripts/install-toolchains.sh' });
      return;
    }

    await fs.writeFile(join(workDir, 'main.cpp'), code);

    const extraFlags = flags ? ` ${flags}` : '';
    const cmd = `bash -c '${getEmsdkEnvCommand()} && emcc "${workDir}/main.cpp" -o "${workDir}/main.js" -s EXPORTED_FUNCTIONS="['_main']" -s EXPORTED_RUNTIME_METHODS="['ccall','cwrap','UTF8ToString']" -s ALLOW_MEMORY_GROWTH=1 -s INITIAL_MEMORY=16MB -s STACK_SIZE=1MB -s SINGLE_FILE=1 -O2${extraFlags}'`;

    const { stdout, stderr } = await execAsync(cmd, {
      timeout: 60000,
      env: { ...process.env, HOME: process.env.HOME || '' }
    });

    const jsFile = await fs.readFile(join(workDir, 'main.js'), 'utf-8');
    const diagnostics = parseDiagnostics(stderr, 'cpp');

    res.json({
      success: true,
      js: jsFile,
      stdout,
      stderr,
      diagnostics
    });
  } catch (err: any) {
    const diagnostics = parseDiagnostics(err.stderr || '', 'cpp');
    res.json({
      success: false,
      error: err.stderr || err.message,
      stdout: err.stdout || '',
      diagnostics
    });
  } finally {
    await fs.rm(workDir, { recursive: true, force: true }).catch(() => { });
  }
});

app.post('/api/compile/swift', async (req: Request, res: Response) => {
  const { code, flags } = req.body as CompileRequest;
  if (!code || typeof code !== 'string') {
    res.status(400).json({ success: false, error: 'Missing code field' });
    return;
  }

  const workDir = await fs.mkdtemp(join(tmpdir(), 'swift-wasm-'));
  try {
    const swiftc = await findInPathsOnly('swiftc', [getSwiftPath()]);
    if (!swiftc) {
      res.status(503).json({ success: false, error: 'swiftc (SwiftWasm) not found. Run: ./scripts/install-toolchains.sh' });
      return;
    }

    await fs.writeFile(join(workDir, 'main.swift'), code);

    const extraFlags = flags ? ` ${flags}` : '';
    const cmd = `PATH="${getSwiftPath()}:$PATH" swiftc -target wasm32-unknown-wasi -o "${workDir}/main.wasm" "${workDir}/main.swift"${extraFlags}`;

    const { stdout, stderr } = await execAsync(cmd, {
      timeout: 60000,
      env: { ...process.env, HOME: process.env.HOME || '' }
    });

    const wasmBytes = await fs.readFile(join(workDir, 'main.wasm'));
    const wasmInfo = parseWasmExportsImports(wasmBytes);
    const diagnostics = parseDiagnostics(stderr, 'swift');

    res.json({
      success: true,
      wasm: wasmBytes.toString('base64'),
      stdout,
      stderr,
      diagnostics,
      wasmInfo
    });
  } catch (err: any) {
    const diagnostics = parseDiagnostics(err.stderr || '', 'swift');
    res.json({
      success: false,
      error: err.stderr || err.message,
      stdout: err.stdout || '',
      diagnostics
    });
  } finally {
    await fs.rm(workDir, { recursive: true, force: true }).catch(() => { });
  }
});

app.post('/api/inspect', async (req: Request, res: Response) => {
  const { wasmBase64 } = req.body;
  if (!wasmBase64 || typeof wasmBase64 !== 'string') {
    res.status(400).json({ success: false, error: 'Missing wasmBase64 field' });
    return;
  }
  try {
    const wasmBytes = Buffer.from(wasmBase64, 'base64');
    const info = parseWasmExportsImports(wasmBytes);
    res.json({ success: true, info });
  } catch (err: any) {
    res.status(500).json({ success: false, error: err.message });
  }
});

app.listen(PORT, () => {
  console.log(`WASM Compiler Bridge running at http://localhost:${PORT}`);
  console.log(`EMSDK_PATH: ${EMSDK_PATH}`);
  console.log(`SWIFTWASM_PATH: ${SWIFTWASM_PATH}`);
});