/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * This module provides the DownloadUtils object which contains useful methods
 * for downloads such as displaying file sizes, transfer times, and download
 * locations.
 *
 * List of methods:
 *
 * [string status, double newLast]
 * getDownloadStatus(int aCurrBytes, [optional] int aMaxBytes,
 *                   [optional] double aSpeed, [optional] double aLastSec)
 *
 * string progress
 * getTransferTotal(int aCurrBytes, [optional] int aMaxBytes)
 *
 * [string timeLeft, double newLast]
 * getTimeLeft(double aSeconds, [optional] double aLastSec)
 *
 * [string dateCompact, string dateComplete]
 * getReadableDates(Date aDate, [optional] Date aNow)
 *
 * [string displayHost, string fullHost]
 * getURIHost(string aURIString)
 *
 * [string convertedBytes, string units]
 * convertByteUnits(int aBytes)
 *
 * [int time, string units, int subTime, string subUnits]
 * convertTimeUnits(double aSecs)
 */

const MS_PER_DAY = 24 * 60 * 60 * 1000;

const BYTE_UNITS = [
  "download-utils-bytes",
  "download-utils-kilobyte",
  "download-utils-megabyte",
  "download-utils-gigabyte",
];

const TIME_UNITS = [
  "download-utils-short-seconds",
  "download-utils-short-minutes",
  "download-utils-short-hours",
  "download-utils-short-days",
];

// These are the maximum values for seconds, minutes, hours corresponding
// with TIME_UNITS without the last item
const TIME_SIZES = [60, 60, 24];

var localeNumberFormatCache = new Map();
function getLocaleNumberFormat(fractionDigits) {
  if (!localeNumberFormatCache.has(fractionDigits)) {
    localeNumberFormatCache.set(
      fractionDigits,
      new Services.intl.NumberFormat(undefined, {
        maximumFractionDigits: fractionDigits,
        minimumFractionDigits: fractionDigits,
      })
    );
  }
  return localeNumberFormatCache.get(fractionDigits);
}

const l10n = new Localization(["toolkit/downloads/downloadUtils.ftl"], true);

// Keep track of at most this many second/lastSec pairs so that multiple calls
// to getTimeLeft produce the same time left
const kCachedLastMaxSize = 10;
var gCachedLast = [];

export var DownloadUtils = {
  /**
   * Generate a full status string for a download given its current progress,
   * total size, speed, last time remaining
   *
   * @param aCurrBytes
   *        Number of bytes transferred so far
   * @param [optional] aMaxBytes
   *        Total number of bytes or -1 for unknown
   * @param [optional] aSpeed
   *        Current transfer rate in bytes/sec or -1 for unknown
   * @param [optional] aLastSec
   *        Last time remaining in seconds or Infinity for unknown
   * @return A pair: [download status text, new value of "last seconds"]
   */
  getDownloadStatus: function DU_getDownloadStatus(
    aCurrBytes,
    aMaxBytes,
    aSpeed,
    aLastSec
  ) {
    let [transfer, timeLeft, newLast, normalizedSpeed] =
      this._deriveTransferRate(aCurrBytes, aMaxBytes, aSpeed, aLastSec);

    let [rate, unit] = DownloadUtils.convertByteUnits(normalizedSpeed);

    let status;
    if (rate === "Infinity") {
      // Infinity download speed doesn't make sense. Show a localized phrase instead.
      status = l10n.formatValueSync("download-utils-status-infinite-rate", {
        transfer,
        timeLeft,
      });
    } else {
      status = l10n.formatValueSync("download-utils-status", {
        transfer,
        rate,
        unit,
        timeLeft,
      });
    }
    return [status, newLast];
  },

  /**
   * Generate a status string for a download given its current progress,
   * total size, speed, last time remaining. The status string contains the
   * time remaining, as well as the total bytes downloaded. Unlike
   * getDownloadStatus, it does not include the rate of download.
   *
   * @param aCurrBytes
   *        Number of bytes transferred so far
   * @param [optional] aMaxBytes
   *        Total number of bytes or -1 for unknown
   * @param [optional] aSpeed
   *        Current transfer rate in bytes/sec or -1 for unknown
   * @param [optional] aLastSec
   *        Last time remaining in seconds or Infinity for unknown
   * @return A pair: [download status text, new value of "last seconds"]
   */
  getDownloadStatusNoRate: function DU_getDownloadStatusNoRate(
    aCurrBytes,
    aMaxBytes,
    aSpeed,
    aLastSec
  ) {
    let [transfer, timeLeft, newLast] = this._deriveTransferRate(
      aCurrBytes,
      aMaxBytes,
      aSpeed,
      aLastSec
    );

    let status = l10n.formatValueSync("download-utils-status-no-rate", {
      transfer,
      timeLeft,
    });
    return [status, newLast];
  },

  /**
   * Helper function that returns a transfer string, a time remaining string,
   * and a new value of "last seconds".
   *
   * @param aCurrBytes
   *        Number of bytes transferred so far
   * @param [optional] aMaxBytes
   *        Total number of bytes or -1 for unknown
   * @param [optional] aSpeed
   *        Current transfer rate in bytes/sec or -1 for unknown
   * @param [optional] aLastSec
   *        Last time remaining in seconds or Infinity for unknown
   * @return A triple: [amount transferred string, time remaining string,
   *                    new value of "last seconds"]
   */
  _deriveTransferRate: function DU__deriveTransferRate(
    aCurrBytes,
    aMaxBytes,
    aSpeed,
    aLastSec
  ) {
    if (aMaxBytes == null) {
      aMaxBytes = -1;
    }
    if (aSpeed == null) {
      aSpeed = -1;
    }
    if (aLastSec == null) {
      aLastSec = Infinity;
    }

    // Calculate the time remaining if we have valid values
    let seconds =
      aSpeed > 0 && aMaxBytes > 0 ? (aMaxBytes - aCurrBytes) / aSpeed : -1;

    let transfer = DownloadUtils.getTransferTotal(aCurrBytes, aMaxBytes);
    let [timeLeft, newLast] = DownloadUtils.getTimeLeft(seconds, aLastSec);
    return [transfer, timeLeft, newLast, aSpeed];
  },

  /**
   * Generate the transfer progress string to show the current and total byte
   * size. Byte units will be as large as possible and the same units for
   * current and max will be suppressed for the former.
   *
   * @param aCurrBytes
   *        Number of bytes transferred so far
   * @param [optional] aMaxBytes
   *        Total number of bytes or -1 for unknown
   * @return The transfer progress text
   */
  getTransferTotal: function DU_getTransferTotal(aCurrBytes, aMaxBytes) {
    if (aMaxBytes == null) {
      aMaxBytes = -1;
    }

    let [progress, progressUnits] = DownloadUtils.convertByteUnits(aCurrBytes);
    let [total, totalUnits] = DownloadUtils.convertByteUnits(aMaxBytes);

    // Figure out which byte progress string to display
    let name;
    if (aMaxBytes < 0) {
      name = "download-utils-transfer-no-total";
    } else if (progressUnits == totalUnits) {
      name = "download-utils-transfer-same-units";
    } else {
      name = "download-utils-transfer-diff-units";
    }

    return l10n.formatValueSync(name, {
      progress,
      progressUnits,
      total,
      totalUnits,
    });
  },

  /**
   * Generate a "time left" string given an estimate on the time left and the
   * last time. The extra time is used to give a better estimate on the time to
   * show. Both the time values are doubles instead of integers to help get
   * sub-second accuracy for current and future estimates.
   *
   * @param aSeconds
   *        Current estimate on number of seconds left for the download
   * @param [optional] aLastSec
   *        Last time remaining in seconds or Infinity for unknown
   * @return A pair: [time left text, new value of "last seconds"]
   */
  getTimeLeft: function DU_getTimeLeft(aSeconds, aLastSec) {
    let nf = new Services.intl.NumberFormat();
    if (aLastSec == null) {
      aLastSec = Infinity;
    }

    if (aSeconds < 0) {
      return [l10n.formatValueSync("download-utils-time-unknown"), aLastSec];
    }

    // Try to find a cached lastSec for the given second
    aLastSec = gCachedLast.reduce(
      (aResult, aItem) => (aItem[0] == aSeconds ? aItem[1] : aResult),
      aLastSec
    );

    // Add the current second/lastSec pair unless we have too many
    gCachedLast.push([aSeconds, aLastSec]);
    if (gCachedLast.length > kCachedLastMaxSize) {
      gCachedLast.shift();
    }

    // Apply smoothing only if the new time isn't a huge change -- e.g., if the
    // new time is more than half the previous time; this is useful for
    // downloads that start/resume slowly
    if (aSeconds > aLastSec / 2) {
      // Apply hysteresis to favor downward over upward swings
      // 30% of down and 10% of up (exponential smoothing)
      let diff = aSeconds - aLastSec;
      aSeconds = aLastSec + (diff < 0 ? 0.3 : 0.1) * diff;

      // If the new time is similar, reuse something close to the last seconds,
      // but subtract a little to provide forward progress
      let diffPct = (diff / aLastSec) * 100;
      if (Math.abs(diff) < 5 || Math.abs(diffPct) < 5) {
        aSeconds = aLastSec - (diff < 0 ? 0.4 : 0.2);
      }
    }

    // Decide what text to show for the time
    let timeLeft;
    if (aSeconds < 4) {
      // Be friendly in the last few seconds
      timeLeft = l10n.formatValueSync("download-utils-time-few-seconds");
    } else {
      // Convert the seconds into its two largest units to display
      let [time1, unit1, time2, unit2] =
        DownloadUtils.convertTimeUnits(aSeconds);

      const pair1 = l10n.formatValueSync("download-utils-time-pair", {
        time: nf.format(time1),
        unit: unit1,
      });

      // Only show minutes for under 1 hour unless there's a few minutes left;
      // or the second pair is 0.
      if ((aSeconds < 3600 && time1 >= 4) || time2 == 0) {
        timeLeft = l10n.formatValueSync("download-utils-time-left-single", {
          time: pair1,
        });
      } else {
        // We've got 2 pairs of times to display
        const pair2 = l10n.formatValueSync("download-utils-time-pair", {
          time: nf.format(time2),
          unit: unit2,
        });
        timeLeft = l10n.formatValueSync("download-utils-time-left-double", {
          time1: pair1,
          time2: pair2,
        });
      }
    }

    return [timeLeft, aSeconds];
  },

  /**
   * Converts a Date object to two readable formats, one compact, one complete.
   * The compact format is relative to the current date, and is not an accurate
   * representation. For example, only the time is displayed for today. The
   * complete format always includes both the date and the time, excluding the
   * seconds, and is often shown when hovering the cursor over the compact
   * representation.
   *
   * @param aDate
   *        Date object representing the date and time to format. It is assumed
   *        that this value represents a past date.
   * @param [optional] aNow
   *        Date object representing the current date and time. The real date
   *        and time of invocation is used if this parameter is omitted.
   * @return A pair: [compact text, complete text]
   */
  getReadableDates: function DU_getReadableDates(aDate, aNow) {
    if (!aNow) {
      aNow = new Date();
    }

    // Figure out when today begins
    let today = new Date(aNow.getFullYear(), aNow.getMonth(), aNow.getDate());

    let dateTimeCompact;
    let dateTimeFull;

    // Figure out if the time is from today, yesterday, this week, etc.
    if (aDate >= today) {
      let dts = new Services.intl.DateTimeFormat(undefined, {
        timeStyle: "short",
      });
      dateTimeCompact = dts.format(aDate);
    } else if (today - aDate < MS_PER_DAY) {
      // After yesterday started, show yesterday
      dateTimeCompact = l10n.formatValueSync("download-utils-yesterday");
    } else if (today - aDate < 6 * MS_PER_DAY) {
      // After last week started, show day of week
      dateTimeCompact = aDate.toLocaleDateString(undefined, {
        weekday: "long",
      });
    } else {
      // Show month/day
      dateTimeCompact = aDate.toLocaleString(undefined, {
        month: "long",
        day: "numeric",
      });
    }

    const dtOptions = { dateStyle: "long", timeStyle: "short" };
    dateTimeFull = new Services.intl.DateTimeFormat(
      undefined,
      dtOptions
    ).format(aDate);

    return [dateTimeCompact, dateTimeFull];
  },

  /**
   * Converts a number of bytes to the appropriate unit that results in an
   * internationalized number that needs fewer than 4 digits.
   *
   * @param aBytes
   *        Number of bytes to convert
   * @return A pair: [new value with 3 sig. figs., its unit]
   */
  convertByteUnits: function DU_convertByteUnits(aBytes) {
    let unitIndex = 0;

    // Convert to next unit if it needs 4 digits (after rounding), but only if
    // we know the name of the next unit
    while (aBytes >= 999.5 && unitIndex < BYTE_UNITS.length - 1) {
      aBytes /= 1024;
      unitIndex++;
    }

    // Get rid of insignificant bits by truncating to 1 or 0 decimal points
    // 0 -> 0; 1.2 -> 1.2; 12.3 -> 12.3; 123.4 -> 123; 234.5 -> 235
    // added in bug 462064: (unitIndex != 0) makes sure that no decimal digit for bytes appears when aBytes < 100
    let fractionDigits = aBytes > 0 && aBytes < 100 && unitIndex != 0 ? 1 : 0;

    // Don't try to format Infinity values using NumberFormat.
    if (aBytes === Infinity) {
      aBytes = "Infinity";
    } else {
      aBytes = getLocaleNumberFormat(fractionDigits).format(aBytes);
    }

    return [aBytes, l10n.formatValueSync(BYTE_UNITS[unitIndex])];
  },

  /**
   * Converts a number of seconds to the two largest units. Time values are
   * whole numbers, and units have the correct plural/singular form.
   *
   * @param aSecs
   *        Seconds to convert into the appropriate 2 units
   * @return 4-item array [first value, its unit, second value, its unit]
   */
  convertTimeUnits: function DU_convertTimeUnits(aSecs) {
    let time = aSecs;
    let scale = 1;
    let unitIndex = 0;

    // Keep converting to the next unit while we have units left and the
    // current one isn't the largest unit possible
    while (unitIndex < TIME_SIZES.length && time >= TIME_SIZES[unitIndex]) {
      time /= TIME_SIZES[unitIndex];
      scale *= TIME_SIZES[unitIndex];
      unitIndex++;
    }

    let value = convertTimeUnitsValue(time);
    let units = convertTimeUnitsUnits(value, unitIndex);

    let extra = aSecs - value * scale;
    let nextIndex = unitIndex - 1;

    // Convert the extra time to the next largest unit
    for (let index = 0; index < nextIndex; index++) {
      extra /= TIME_SIZES[index];
    }

    let value2 = convertTimeUnitsValue(extra);
    let units2 = convertTimeUnitsUnits(value2, nextIndex);

    return [value, units, value2, units2];
  },

  /**
   * Converts a number of seconds to "downloading file opens in X" status.
   *
   * @param aSeconds
   *        Seconds to convert into the time format.
   * @return status object, example:
   *  status = {
   *      l10n: {
   *        id: "downloading-file-opens-in-minutes-and-seconds",
   *        args: { minutes: 2, seconds: 30 },
   *      },
   *   };
   */
  getFormattedTimeStatus: function DU_getFormattedTimeStatus(aSeconds) {
    aSeconds = Math.floor(aSeconds);
    let l10n;
    if (!isFinite(aSeconds) || aSeconds < 0) {
      l10n = {
        id: "downloading-file-opens-in-some-time-2",
      };
    } else if (aSeconds < 60) {
      l10n = {
        id: "downloading-file-opens-in-seconds-2",
        args: { seconds: aSeconds },
      };
    } else if (aSeconds < 3600) {
      let minutes = Math.floor(aSeconds / 60);
      let seconds = aSeconds % 60;
      l10n = seconds
        ? {
            args: { seconds, minutes },
            id: "downloading-file-opens-in-minutes-and-seconds-2",
          }
        : { args: { minutes }, id: "downloading-file-opens-in-minutes-2" };
    } else {
      let hours = Math.floor(aSeconds / 3600);
      let minutes = Math.floor((aSeconds % 3600) / 60);
      l10n = {
        args: { hours, minutes },
        id: "downloading-file-opens-in-hours-and-minutes-2",
      };
    }
    return { l10n };
  },
};

/**
 * Private helper for convertTimeUnits that gets the display value of a time
 *
 * @param aTime
 *        Time value for display
 * @return An integer value for the time rounded down
 */
function convertTimeUnitsValue(aTime) {
  return Math.floor(aTime);
}

/**
 * Private helper for convertTimeUnits that gets the display units of a time
 *
 * @param timeValue
 *        Time value for display
 * @param aIndex
 *        Index into gStr.timeUnits for the appropriate unit
 * @return The appropriate plural form of the unit for the time
 */
function convertTimeUnitsUnits(timeValue, aIndex) {
  // Negative index would be an invalid unit, so just give empty
  if (aIndex < 0) {
    return "";
  }

  return l10n.formatValueSync(TIME_UNITS[aIndex], { timeValue });
}

/**
 * Private helper function to log errors to the error console and command line
 *
 * @param aMsg
 *        Error message to log or an array of strings to concat
 */
// function log(aMsg) {
//   let msg = "DownloadUtils.sys.mjs: " + (aMsg.join ? aMsg.join("") : aMsg);
//   Services.console.logStringMessage(msg);
//   dump(msg + "\n");
// }
