import { Meteor } from 'meteor/meteor';

const hasOwn = Object.prototype.hasOwnProperty;

function Log(...args) {
  Log.info(...args);
}

/// FOR TESTING
let intercept = 0;
let interceptedLines = [];
let suppress = 0;

// Intercept the next 'count' calls to a Log function. The actual
// lines printed to the console can be cleared and read by calling
// Log._intercepted().
Log._intercept = (count) => {
  intercept += count;
};

// Suppress the next 'count' calls to a Log function. Use this to stop
// tests from spamming the console, especially with red errors that
// might look like a failing test.
Log._suppress = (count) => {
  suppress += count;
};

// Returns intercepted lines and resets the intercept counter.
Log._intercepted = () => {
  const lines = interceptedLines;
  interceptedLines = [];
  intercept = 0;
  return lines;
};

// Either 'json' or 'colored-text'.
//
// When this is set to 'json', print JSON documents that are parsed by another
// process ('satellite' or 'meteor run'). This other process should call
// 'Log.format' for nice output.
//
// When this is set to 'colored-text', call 'Log.format' before printing.
// This should be used for logging from within satellite, since there is no
// other process that will be reading its standard output.
Log.outputFormat = 'json';

const LEVEL_COLORS = {
  debug: 'green',
  // leave info as the default color
  warn: 'magenta',
  error: 'red'
};

const META_COLOR = 'blue';

// Default colors cause readability problems on Windows Powershell,
// switch to bright variants. While still capable of millions of
// operations per second, the benchmark showed a 25%+ increase in
// ops per second (on Node 8) by caching "process.platform".
const isWin32 = typeof process === 'object' && process.platform === 'win32';
const platformColor = (color) => {
  if (isWin32 && typeof color === 'string' && !color.endsWith('Bright')) {
    return `${color}Bright`;
  }
  return color;
};

// XXX package
const RESTRICTED_KEYS = ['time', 'timeInexact', 'level', 'file', 'line',
                        'program', 'originApp', 'satellite', 'stderr'];

const FORMATTED_KEYS = [...RESTRICTED_KEYS, 'app', 'message'];

const logInBrowser = obj => {
  const str = Log.format(obj);

  // XXX Some levels should be probably be sent to the server
  const level = obj.level;

  if ((typeof console !== 'undefined') && console[level]) {
    console[level](str);
  } else {
    // XXX Uses of Meteor._debug should probably be replaced by Log.debug or
    //     Log.info, and we should have another name for "do your best to
    //     call call console.log".
    Meteor._debug(str);
  }
};

// @returns {Object: { line: Number, file: String }}
Log._getCallerDetails = () => {
  const getStack = () => {
    // We do NOT use Error.prepareStackTrace here (a V8 extension that gets us a
    // pre-parsed stack) since it's impossible to compose it with the use of
    // Error.prepareStackTrace used on the server for source maps.
    const err = new Error;
    const stack = err.stack;
    return stack;
  };

  const stack = getStack();

  if (!stack) {
    return {};
  }

  // looking for the first line outside the logging package (or an
  // eval if we find that first)
  let line;
  const lines = stack.split('\n').slice(1);
  for (line of lines) {
    if (line.match(/^\s*at eval \(eval/)) {
      return {file: "eval"};
    }

    if (!line.match(/packages\/(?:local-test[:_])?logging(?:\/|\.js)/)) {
      break;
    }
  }

  const details = {};

  // The format for FF is 'functionName@filePath:lineNumber'
  // The format for V8 is 'functionName (packages/logging/logging.js:81)' or
  //                      'packages/logging/logging.js:81'
  const match = /(?:[@(]| at )([^(]+?):([0-9:]+)(?:\)|$)/.exec(line);
  if (!match) {
    return details;
  }

  // in case the matched block here is line:column
  details.line = match[2].split(':')[0];

  // Possible format: https://foo.bar.com/scripts/file.js?random=foobar
  // XXX: if you can write the following in better way, please do it
  // XXX: what about evals?
  details.file = match[1].split('/').slice(-1)[0].split('?')[0];

  return details;
};

['debug', 'info', 'warn', 'error'].forEach((level) => {
 // @param arg {String|Object}
 Log[level] = (arg) => {
  if (suppress) {
    suppress--;
    return;
  }

  let intercepted = false;
  if (intercept) {
    intercept--;
    intercepted = true;
  }

  let obj = (arg === Object(arg)
    && !(arg instanceof RegExp)
    && !(arg instanceof Date))
    ? arg
    : { message: new String(arg).toString() };

  RESTRICTED_KEYS.forEach(key => {
    if (obj[key]) {
      throw new Error(`Can't set '${key}' in log message`);
    }
  });

  if (hasOwn.call(obj, 'message') && typeof obj.message !== 'string') {
    throw new Error("The 'message' field in log objects must be a string");
  }

  if (!obj.omitCallerDetails) {
    obj = { ...Log._getCallerDetails(), ...obj };
  }

  obj.time = new Date();
  obj.level = level;

  // XXX allow you to enable 'debug', probably per-package
  if (level === 'debug') {
    return;
  }

  if (intercepted) {
    interceptedLines.push(EJSON.stringify(obj));
  } else if (Meteor.isServer) {
    if (Log.outputFormat === 'colored-text') {
      console.log(Log.format(obj, {color: true}));
    } else if (Log.outputFormat === 'json') {
      console.log(EJSON.stringify(obj));
    } else {
      throw new Error(`Unknown logging output format: ${Log.outputFormat}`);
    }
  } else {
    logInBrowser(obj);
  }
};
});


// tries to parse line as EJSON. returns object if parse is successful, or null if not
Log.parse = (line) => {
  let obj = null;
  if (line && line.startsWith('{')) { // might be json generated from calling 'Log'
    try { obj = EJSON.parse(line); } catch (e) {}
  }

  // XXX should probably check fields other than 'time'
  if (obj && obj.time && (obj.time instanceof Date)) {
    return obj;
  } else {
    return null;
  }
};

// formats a log object into colored human and machine-readable text
Log.format = (obj, options = {}) => {
  obj = { ...obj }; // don't mutate the argument
  let {
    time,
    timeInexact,
    level = 'info',
    file,
    line: lineNumber,
    app: appName = '',
    originApp,
    message = '',
    program = '',
    satellite = '',
    stderr = '',
  } = obj;

  if (!(time instanceof Date)) {
    throw new Error("'time' must be a Date object");
  }

  FORMATTED_KEYS.forEach((key) => { delete obj[key]; });

  if (Object.keys(obj).length > 0) {
    if (message) {
      message += ' ';
    }
    message += EJSON.stringify(obj);
  }

  const pad2 = n => n.toString().padStart(2, '0');
  const pad3 = n => n.toString().padStart(3, '0');

  const dateStamp = time.getFullYear().toString() +
    pad2(time.getMonth() + 1 /*0-based*/) +
    pad2(time.getDate());
  const timeStamp = pad2(time.getHours()) +
        ':' +
        pad2(time.getMinutes()) +
        ':' +
        pad2(time.getSeconds()) +
        '.' +
        pad3(time.getMilliseconds());

  // eg in San Francisco in June this will be '(-7)'
  const utcOffsetStr = `(${(-(new Date().getTimezoneOffset() / 60))})`;

  let appInfo = '';
  if (appName) {
    appInfo += appName;
  }
  if (originApp && originApp !== appName) {
    appInfo += ` via ${originApp}`;
  }
  if (appInfo) {
    appInfo = `[${appInfo}] `;
  }

  const sourceInfoParts = [];
  if (program) {
    sourceInfoParts.push(program);
  }
  if (file) {
    sourceInfoParts.push(file);
  }
  if (lineNumber) {
    sourceInfoParts.push(lineNumber);
  }

  let sourceInfo = !sourceInfoParts.length ?
    '' : `(${sourceInfoParts.join(':')}) `;

  if (satellite)
    sourceInfo += `[${satellite}]`;

  const stderrIndicator = stderr ? '(STDERR) ' : '';

  const metaPrefix = [
    level.charAt(0).toUpperCase(),
    dateStamp,
    '-',
    timeStamp,
    utcOffsetStr,
    timeInexact ? '? ' : ' ',
    appInfo,
    sourceInfo,
    stderrIndicator].join('');

  const prettify = function (line, color) {
    return (options.color && Meteor.isServer && color) ?
      require('cli-color')[color](line) : line;
  };

  return prettify(metaPrefix, platformColor(options.metaColor || META_COLOR)) +
    prettify(message, platformColor(LEVEL_COLORS[level]));
};

// Turn a line of text into a loggable object.
// @param line {String}
// @param override {Object}
Log.objFromText = (line, override) => {
  return {
    message: line,
    level: 'info',
    time: new Date(),
    timeInexact: true,
    ...override
  };
};

export { Log };