const express = require('express')
const { spawn } = require('child_process');
const readline = require('readline');
const AWS = require('aws-sdk');
const config = require('./config.js');
const fs = require('fs');
const path = require('path');
const { get } = require('http');
const app = express();
const port = 3000;

// FILE FUNCS
// Configure S3 client if not using local
let s3;
if (config.buckregion !== 'local') { // assuming 'local' means local file system
  s3 = new AWS.S3({
    accessKeyId: config.accessKeyId,
    secretAccessKey: config.secretAccessKey,
    endpoint: config.endpoint,
    s3ForcePathStyle: true, // needed for self-hosted S3 like MinIO or garage
  });
} else {
  console.log("!! Using local storage for files. This is not recommended for production.")
}

function getFileFromStorage(loc) {
  return new Promise((resolve, reject) => {
    if (config.buckregion === 'local') {
      fs.readFile(path.join("localstorage", loc), { encoding: 'utf-8' }, (err, data) => {
        if (err) return reject(err);
        resolve(data);
      });
    } else {
      // S3 access
      const params = {
        Bucket: config.bucketname,
        Key: loc, // loc is the file key in S3
      };
      s3.getObject(params, (err, data) => {
        if (err) return reject(err);
        resolve(data.Body.toString('utf-8'));
      });
    }
  });
}

function writeLocalFile(loc, data) {
  return new Promise((resolve, reject) => {
    fs.writeFile(loc, data, (err) => {
      if (err) return reject(err);
      resolve();
    });
  });
}

app.get('/', (req, res) => {
  res.send(`<h1>ShittyServerless execution instance.</h1> If you are an end-user, contact site-admin for documentation.<br>
    If you are a developer, deploy your serverless functions by placing files in the garage webui manually.`);
})

const exitCodeLookup = {
  0: 200,
  1: 500,
  2: 403,
  3: 401,
  4: 404,
} // Lookup table to map exit codes to HTTP status codes

function execFileAsync(req,res, command, location, opts = {}) {
  // opts: { timeoutMs: number } optional
  const timeoutMs = opts.timeoutMs || Infinity; // default no timeout
  let killTimer; // to hold timeout timer
  return new Promise((resolve, reject) => {
    let finished = false;
    function onceFinish(err) {
      if (finished) return;
      finished = true;
      try{clearTimeout(killTimer);console.log("Cleared timer")}catch(e){}
      if (err) {
        try { res.status(500).end(); } catch (e) {}
        reject(err);
      } else {
        resolve();
      }
    }

    (async () => {
      try {
        // --- prepare temp file (keeps your original logic) ---
        const tempDir = '/tmp';
        const fileName = path.basename(location[0]);
        const tempFilePath = path.join(tempDir, fileName);

        const contents = await getFileFromStorage(location[0]);
        await writeLocalFile(tempFilePath, contents);

        // --- spawn process ---
        const child = spawn(command, [tempFilePath]);

        // make sure we DONT close stdin (we need to send data to the child for it to have reactiveness)

        child.on('error', (err) => {
          console.error('child process error', err);
          onceFinish(new Error('Failed to spawn child process: ' + err.message));
        });

        // safety timeout to avoid indefinite hangs
        killTimer = setTimeout(() => {
          if (finished) return;
          console.error(`child timeout after ${timeoutMs}ms — killing pid ${child.pid}`);
          try { child.kill('SIGKILL'); } catch (e) {}
          onceFinish(new Error(`Child process timeout after ${timeoutMs}ms`));
        }, timeoutMs);

        // --- streaming header parser ---
        let isReadingHeaders = true;
        let headerBuf = ''; // string buffer for header parsing
        let headers = { 'Content-Type': 'text/plain' };
        let statusCode = 200;

        function parseHeadersAndFlush(remainder) {
          const lines = headerBuf.split(/\r?\n/);
          for (const line of lines) {
            if (!line.trim()) continue;
            // if line looks like "Key: value"
            const idx = line.indexOf(':');
            if (idx > -1) {
              const key = line.slice(0, idx).trim();
              const val = line.slice(idx + 1).trim();
              // treat status header specially if you want
              if (key.toLowerCase() === 'status') {
                const parsed = parseInt(val, 10);
                if (!Number.isNaN(parsed)) statusCode = parsed;
              } else {
                headers[key] = val;
              }
            }
          }
          // Send headers and write remainder
          try {
            res.writeHead(statusCode, headers);
          } catch (e) {
            console.warn('res.writeHead failed', e);
          }
          if (remainder && remainder.length) {
            res.write(remainder);
          }
        }

        // We will listen on stdout data and look for the token.
        child.stdout.on('data', (chunk) => {
          if (finished) return;
          const str = chunk.toString('utf8');

          if (isReadingHeaders) {
            headerBuf += str;
            // Look for the token on its own line anywhere in headerBuf
            const token = '\n!!STARTBODY';
            let index = headerBuf.indexOf(token);

            // also allow token at very start (no preceding newline)
            if (index === -1 && headerBuf.indexOf('!!STARTBODY') === 0) {
              index = 0;
            }

            if (headerBuf.endsWith("!!RECVDATA")) {
              console.log("Child is requesting data from us...");
              child.stdin.write(JSON.stringify({
                method: req.method,
                headers: req.headers,
                query: req.query,
                params: req.params
              }));
              child.stdin.write("\n"); // newline to signal end of JSON, because child most likely uses input() or readline()
              headerBuf = headerBuf.slice(0, headerBuf.length - "!!RECVDATA".length); // remove the token, to avoid cluttering headerspace
              return; // wait for more data
            }

            if (index !== -1) {
              // header portion is everything before token (strip a preceding newline)
              let headerPart = headerBuf.slice(0, index);
              // remainder after token
              let remainder = headerBuf.slice(index + token.length);
              // If token was at start without the leading \n, we've included token; handle that case
              if (headerPart.startsWith('\n')) headerPart = headerPart.slice(1);

              // parse headerPart lines
              headerBuf = headerPart;
              parseHeadersAndFlush(remainder);

              // switch mode
              isReadingHeaders = false;
            } else {
              // if no token yet, keep buffering — but to avoid unbounded growth, cap buffer size
              const MAX_HEADER_BUF = 64 * 1024; // 64KB
              if (headerBuf.length > MAX_HEADER_BUF) {
                // give up and treat whole buffer as headers
                parseHeadersAndFlush('');
                isReadingHeaders = false;
              }
            }
          } else {
            // already reading body — stream straight to response
            res.write(str);
          }
        });

        // also forward stderr to console (and optionally to response)
        child.stderr.on('data', (data) => {
          console.error(`stderr: ${data.toString()}`);
        });

        child.on('close', (code) => {
          // If we never left header mode, send a helpful message
          if (isReadingHeaders) {
            try {
              res.writeHead(200, headers);
              res.write("No body content. Double check that the child process emits the delimiter `!!STARTBODY` followed by a newline.\n");
            } catch (e) {
              console.warn('writeHead on close failed', e);
            }
          }
          console.log(`child process exited with code ${code}`);
          const mappedStatus = exitCodeLookup[code] || 500;
          console.log(`Mapping exit code ${code} to HTTP status ${mappedStatus}`);
          try { res.status(mappedStatus);
            res.end(); } catch (e) {console.log(e)}
          // Remove temp file
          try {
            fs.unlink(tempFilePath, (err) => {
              if (err) {
                console.warn('Failed to remove temp file', tempFilePath, err);
              } else {
                console.log('Temp file removed', tempFilePath);
              }
            });
          } catch (e) {
            console.warn('unlink failed', e);
          }
          onceFinish(null,code);
        });

      } catch (err) {
        onceFinish(err);
      }
    })();
  });
}



const lookup = {
  sh: 'bash',
  py: 'python3',
  js: 'node',
}




app.get('/*path', async (req, res) => {
  const filePath = req.path.replace(/^\/+/, ''); // remove leading slash(s)
  console.log(`[request] filePath="${filePath}"`);

  if (!filePath) {
    return res.status(400).send('No file requested');
  }

  // default timeout (ms) for execFileAsync; tune as needed
  const execOpts = { timeoutMs: 30_000 };

  try {
    if (filePath.includes('.')) {
      const ext = filePath.split('.').pop();
      console.log(`[lookup] requested ext="${ext}"`);
      if (lookup[ext]) {
        await execFileAsync(req,res, lookup[ext], [filePath], execOpts);
        return; // response handled by execFileAsync
      } else {
        console.log(`[lookup] no handler for extension "${ext}"`);
      }
    }

    // Brute-force check (ensure fs checks the correct cwd or use absolute paths)
    let found = false;
    for (const ext in lookup) {
      const candidate = filePath + '.' + ext;
      console.log(`[bruteforce] checking ${candidate}`);
      try{
        await getFileFromStorage(candidate);
        console.log(`[bruteforce] found ${candidate} -> handler ${lookup[ext]}`);
        await execFileAsync(req,res, lookup[ext], [candidate], execOpts);
        found = true;
        break;
      } catch {continue;}
    }

    if (!found) {
      if (!res.headersSent) {
        res.status(404).send("No matching file found for serverless execution");
      } else {
        res.end();
      }
      return;
    }
  } catch (err) {
    console.error('[execFileAsync] error:', err && err.stack ? err.stack : err);
    // If execFileAsync already sent headers/body, don't try to send another response
    if (!res.headersSent) {
      res.status(500).send("Serverless function failed to execute");
    } else {
      try { res.end(); } catch (e) {}
    }
    return;
  }
});
app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})