let onLoad = new Promise(function(resolve, reject) {
  window.onload = resolve;
});

function parseBuildID(buildID) {
  return {
    year: Number(buildID.substring(0, 4)),
    month: Number(buildID.substring(4, 6)),
    day: Number(buildID.substring(6, 8)),
    hour: Number(buildID.substring(8, 10)),
    minute: Number(buildID.substring(10, 12)),
    second: Number(buildID.substring(12, 14)),
  };
}

function compareBuildIDs(buildID1, buildID2) {
  let buildObj1 = parseBuildID(buildID1);
  let buildObj2 = parseBuildID(buildID2);

  if (buildObj1.year > buildObj2.year) {
    return 1;
  } else if (buildObj1.year < buildObj2.year) {
    return -1;
  }

  if (buildObj1.month > buildObj2.month) {
    return 1;
  } else if (buildObj1.month < buildObj2.month) {
    return -1;
  }

  if (buildObj1.day > buildObj2.day) {
    return 1;
  } else if (buildObj1.day < buildObj2.day) {
    return -1;
  }

  if (buildObj1.hour > buildObj2.hour) {
    return 1;
  } else if (buildObj1.hour < buildObj2.hour) {
    return -1;
  }

  if (buildObj1.minute > buildObj2.minute) {
    return 1;
  } else if (buildObj1.minute < buildObj2.minute) {
    return -1;
  }

  if (buildObj1.second > buildObj2.second) {
    return 1;
  } else if (buildObj1.second < buildObj2.second) {
    return -1;
  }

  return 0;
}

function toTwoDigits(num) {
  if (num < 10) {
    return '0' + num;
  }

  return num;
}

function fromBuildIDtoChangeset(buildID) {
  let buildObj = parseBuildID(buildID);

  let directory = 'https://ftp.mozilla.org/pub/firefox/nightly/' + buildObj.year + '/' + toTwoDigits(buildObj.month) + '/' + buildObj.year + '-' + toTwoDigits(buildObj.month) + '-' + toTwoDigits(buildObj.day) + '-' + toTwoDigits(buildObj.hour) + '-' + toTwoDigits(buildObj.minute) + '-' + toTwoDigits(buildObj.second) + '-mozilla-central/';

  return fetch(directory)
  .then(response => response.text())
  .then(data => {
    let file = data.match(/firefox-\d+.0a1.en-US.win32.txt/);
    if (file.length == 1) {
      return file[0];
    } else {
      throw new Error('Couldn\'t find win32.txt file.');
    }
  })
  .then(file => fetch(directory + file))
  .then(response => response.text())
  .then(data => {
    let lines = data.split('\n');
    lines = lines.map(line => line.replace('\r', ''));
    let buildIDfromFile = lines[0];
    if (buildID != buildIDfromFile) {
      throw new Error('Unexpected error: wrong build ID in directory.');
    }
    return lines[1];
  });
}

function getRevFromChangeset(changeset) {
  let re = /https:\/\/hg.mozilla.org\/mozilla-central\/rev\/([A-Za-z0-9]+)/;
  let result = re.exec(changeset);
  return result[1];
}

function getChangesetDate(changeset) {
  return fetch('https://hg.mozilla.org/mozilla-central/json-rev/' + changeset)
  .then(response => response.json())
  .then(json_rev => new Date(json_rev['pushdate'][0] * 1000))
}

function findFirstBuildIDInSet(buildIDs, date, i=0) {
  return fromBuildIDtoChangeset(buildIDs[i])
  .then(buildChangeset => getChangesetDate(getRevFromChangeset(buildChangeset)))
  .then(buildDate => {
    if (buildDate >= date) {
      return buildIDs[i];
    } else {
      return matchBuildID(buildIDs, date, i + 1);
    }
  });
}

function findFirstBuildID(date, year=null, month=null) {
  // Who knows where Firefox is built, so give the build ID some slack.
  let possibleDate = new Date(date.getTime());
  possibleDate.setUTCHours(possibleDate.getUTCHours() - 9);
  let possibleBuildID = '' + possibleDate.getUTCFullYear() + toTwoDigits((possibleDate.getUTCMonth() + 1)) + toTwoDigits(possibleDate.getUTCDate()) + toTwoDigits(possibleDate.getUTCHours()) + toTwoDigits(possibleDate.getUTCMinutes()) + toTwoDigits(possibleDate.getUTCSeconds());

  if (year == null) {
    year = possibleDate.getUTCFullYear();
    month = possibleDate.getUTCMonth() + 1;
  }

  return fetch('https://ftp.mozilla.org/pub/firefox/nightly/' + year + '/' + toTwoDigits(month) + '/')
  .then(response => response.text())
  .then(data => {
    let re = />(\d+)-(\d\d)-(\d\d)-(\d\d)-(\d\d)-(\d\d)-mozilla-central\/</g;
    let results;

    let buildIDs = [];

    while ((results = re.exec(data)) !== null) {
      let buildID = results[1] + results[2] + results[3] + results[4] + results[5] + results[6];

      // Check if this build ID is 'newer' than date.
      if (compareBuildIDs(possibleBuildID, buildID) != 1) {
        buildIDs.push(buildID);
      }
    }

    return buildIDs;
  })
  .then(buildIDs => {
    if (buildIDs.length === 0) {
      return null;
    }

    return findFirstBuildIDInSet(buildIDs, date);
  })
  .then(rev => {
    if (!rev) {
      let nextYear = (month + 1) == 13 ? year + 1 : year;
      let nextMonth = month + 1;
      if (nextMonth == 13) {
        nextMonth = 1;
      }

      if (nextYear > new Date().getUTCFullYear() || (nextYear == new Date().getUTCFullYear() && nextMonth > (new Date().getUTCMonth() + 1))) {
        return null;
      }

      return findFirstBuildID(date, nextYear, nextMonth);
    }

    return rev;
  });
}

function getBuildID(changeset) {
  return getChangesetDate(changeset)
  .then(date => findFirstBuildID(date));
}

onLoad
.then(function() {
  document.getElementById('getChangeset').onclick = function() {
    // e.g. 20161001030430
    fromBuildIDtoChangeset(document.getElementById('buildID').value)
    .then(changeset => document.getElementById('getChangesetResult').textContent = changeset)
  };

  document.getElementById('getBuildID').onclick = function() {
    // e.g. 87cd291d2db6
    // 1: Find date of the changeset
    // 2: Find first build ID that is greater than the date of the changeset
    // 3: Get the changeset for the build ID found in (2), if it's older than changeset, go to the next build.
    getBuildID(document.getElementById('changeset').value)
    .then(buildID => document.getElementById('getBuildIDResult').textContent = buildID ? buildID : 'Not shipped yet.')
  };
});