'use strict';

const child_process = require('child_process');

// The port used by servers and wrk
exports.PORT = process.env.PORT || 12346;

function AutocannonBenchmarker() {
  this.name = 'autocannon';
  this.autocannon_exe = process.platform === 'win32'
                      ? 'autocannon.cmd'
                      : 'autocannon';
  const result = child_process.spawnSync(this.autocannon_exe, ['-h']);
  this.present = !(result.error && result.error.code === 'ENOENT');
}

AutocannonBenchmarker.prototype.create = function(options) {
  const args = ['-d', options.duration, '-c', options.connections, '-j', '-n',
                `http://127.0.0.1:${options.port}${options.path}` ];
  const child = child_process.spawn(this.autocannon_exe, args);
  return child;
};

AutocannonBenchmarker.prototype.processResults = function(output) {
  let result;
  try {
    result = JSON.parse(output);
  } catch (err) {
    // Do nothing, let next line handle this
  }
  if (!result || !result.requests || !result.requests.average) {
    return undefined;
  } else {
    return result.requests.average;
  }
};

function WrkBenchmarker() {
  this.name = 'wrk';
  this.regexp = /Requests\/sec:[ \t]+([0-9.]+)/;
  const result = child_process.spawnSync('wrk', ['-h']);
  this.present = !(result.error && result.error.code === 'ENOENT');
}

WrkBenchmarker.prototype.create = function(options) {
  const args = ['-d', options.duration, '-c', options.connections, '-t', 8,
                `http://127.0.0.1:${options.port}${options.path}` ];
  const child = child_process.spawn('wrk', args);
  return child;
};

WrkBenchmarker.prototype.processResults = function(output) {
  const match = output.match(this.regexp);
  const result = match && +match[1];
  if (!result) {
    return undefined;
  } else {
    return result;
  }
};

const http_benchmarkers = [ new WrkBenchmarker(),
                            new AutocannonBenchmarker() ];

const benchmarkers = {};

http_benchmarkers.forEach((benchmarker) => {
  benchmarkers[benchmarker.name] = benchmarker;
  if (!exports.default_http_benchmarker && benchmarker.present) {
    exports.default_http_benchmarker = benchmarker.name;
  }
});

exports.run = function(options, callback) {
  options = Object.assign({
    port: exports.PORT,
    path: '/',
    connections: 100,
    duration: 10,
    benchmarker: exports.default_http_benchmarker
  }, options);
  if (!options.benchmarker) {
    callback(new Error('Could not locate any of the required http ' +
                       'benchmarkers. Check benchmark/README.md for further ' +
                       'instructions.'));
    return;
  }
  const benchmarker = benchmarkers[options.benchmarker];
  if (!benchmarker) {
    callback(new Error(`Requested benchmarker '${options.benchmarker}' is ` +
                       'not supported'));
    return;
  }
  if (!benchmarker.present) {
    callback(new Error(`Requested benchmarker '${options.benchmarker}' is ` +
                       'not installed'));
    return;
  }

  const benchmarker_start = process.hrtime();

  const child = benchmarker.create(options);

  child.stderr.pipe(process.stderr);

  let stdout = '';
  child.stdout.on('data', (chunk) => stdout += chunk.toString());

  child.once('close', function(code) {
    const elapsed = process.hrtime(benchmarker_start);
    if (code) {
      let error_message = `${options.benchmarker} failed with ${code}.`;
      if (stdout !== '') {
        error_message += ` Output: ${stdout}`;
      }
      callback(new Error(error_message), code);
      return;
    }

    const result = benchmarker.processResults(stdout);
    if (!result) {
      callback(new Error(`${options.benchmarker} produced strange output: ` +
                         stdout, code));
      return;
    }

    callback(null, code, options.benchmarker, result, elapsed);
  });

};