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[dygraphs.git] / dygraph-utils.js

// Copyright 2011 Dan Vanderkam (danvdk@gmail.com)
// All Rights Reserved.

/**
 * @fileoverview This file contains utility functions used by dygraphs. These
 * are typically static (i.e. not related to any particular dygraph). Examples
 * include date/time formatting functions, basic algorithms (e.g. binary
 * search) and generic DOM-manipulation functions.
 */

Dygraph.LOG_SCALE = 10;
Dygraph.LN_TEN = Math.log(Dygraph.LOG_SCALE);

/** @private */
Dygraph.log10 = function(x) {
  return Math.log(x) / Dygraph.LN_TEN;
}

// Various logging levels.
Dygraph.DEBUG = 1;
Dygraph.INFO = 2;
Dygraph.WARNING = 3;
Dygraph.ERROR = 3;

// TODO(danvk): any way I can get the line numbers to be this.warn call?
/**
 * @private
 * Log an error on the JS console at the given severity.
 * @param { Integer } severity One of Dygraph.{DEBUG,INFO,WARNING,ERROR}
 * @param { String } The message to log.
 */
Dygraph.log = function(severity, message) {
  if (typeof(console) != 'undefined') {
    switch (severity) {
      case Dygraph.DEBUG:
        console.debug('dygraphs: ' + message);
        break;
      case Dygraph.INFO:
        console.info('dygraphs: ' + message);
        break;
      case Dygraph.WARNING:
        console.warn('dygraphs: ' + message);
        break;
      case Dygraph.ERROR:
        console.error('dygraphs: ' + message);
        break;
    }
  }
};

/** @private */
Dygraph.info = function(message) {
  Dygraph.log(Dygraph.INFO, message);
};
/** @private */
Dygraph.prototype.info = Dygraph.info;

/** @private */
Dygraph.warn = function(message) {
  Dygraph.log(Dygraph.WARNING, message);
};
/** @private */
Dygraph.prototype.warn = Dygraph.warn;

/** @private */
Dygraph.error = function(message) {
  Dygraph.log(Dygraph.ERROR, message);
};
/** @private */
Dygraph.prototype.error = Dygraph.error;

/**
 * @private
 * Return the 2d context for a dygraph canvas.
 *
 * This method is only exposed for the sake of replacing the function in
 * automated tests, e.g.
 *
 * var oldFunc = Dygraph.getContext();
 * Dygraph.getContext = function(canvas) {
 *   var realContext = oldFunc(canvas);
 *   return new Proxy(realContext);
 * };
 */
Dygraph.getContext = function(canvas) {
  return canvas.getContext("2d");
};

/**
 * @private
 * Add an event handler. This smooths a difference between IE and the rest of
 * the world.
 * @param { DOM element } el The element to add the event to.
 * @param { String } evt The name of the event, e.g. 'click' or 'mousemove'.
 * @param { Function } fn The function to call on the event. The function takes
 * one parameter: the event object.
 */
Dygraph.addEvent = function(el, evt, fn) {
  var normed_fn = function(e) {
    if (!e) var e = window.event;
    fn(e);
  };
  if (window.addEventListener) {  // Mozilla, Netscape, Firefox
    el.addEventListener(evt, normed_fn, false);
  } else {  // IE
    el.attachEvent('on' + evt, normed_fn);
  }
};

/**
 * @private
 * Cancels further processing of an event. This is useful to prevent default
 * browser actions, e.g. highlighting text on a double-click.
 * Based on the article at
 * http://www.switchonthecode.com/tutorials/javascript-tutorial-the-scroll-wheel
 * @param { Event } e The event whose normal behavior should be canceled.
 */
Dygraph.cancelEvent = function(e) {
  e = e ? e : window.event;
  if (e.stopPropagation) {
    e.stopPropagation();
  }
  if (e.preventDefault) {
    e.preventDefault();
  }
  e.cancelBubble = true;
  e.cancel = true;
  e.returnValue = false;
  return false;
};

/**
 * Convert hsv values to an rgb(r,g,b) string. Taken from MochiKit.Color. This
 * is used to generate default series colors which are evenly spaced on the
 * color wheel.
 * @param { Number } hue Range is 0.0-1.0.
 * @param { Number } saturation Range is 0.0-1.0.
 * @param { Number } value Range is 0.0-1.0.
 * @return { String } "rgb(r,g,b)" where r, g and b range from 0-255.
 * @private
 */
Dygraph.hsvToRGB = function (hue, saturation, value) {
  var red;
  var green;
  var blue;
  if (saturation === 0) {
    red = value;
    green = value;
    blue = value;
  } else {
    var i = Math.floor(hue * 6);
    var f = (hue * 6) - i;
    var p = value * (1 - saturation);
    var q = value * (1 - (saturation * f));
    var t = value * (1 - (saturation * (1 - f)));
    switch (i) {
      case 1: red = q; green = value; blue = p; break;
      case 2: red = p; green = value; blue = t; break;
      case 3: red = p; green = q; blue = value; break;
      case 4: red = t; green = p; blue = value; break;
      case 5: red = value; green = p; blue = q; break;
      case 6: // fall through
      case 0: red = value; green = t; blue = p; break;
    }
  }
  red = Math.floor(255 * red + 0.5);
  green = Math.floor(255 * green + 0.5);
  blue = Math.floor(255 * blue + 0.5);
  return 'rgb(' + red + ',' + green + ',' + blue + ')';
};

// The following functions are from quirksmode.org with a modification for Safari from
// http://blog.firetree.net/2005/07/04/javascript-find-position/
// http://www.quirksmode.org/js/findpos.html

/** @private */
Dygraph.findPosX = function(obj) {
  var curleft = 0;
  if(obj.offsetParent)
    while(1)
    {
      curleft += obj.offsetLeft;
      if(!obj.offsetParent)
        break;
      obj = obj.offsetParent;
    }
  else if(obj.x)
    curleft += obj.x;
  return curleft;
};

/** @private */
Dygraph.findPosY = function(obj) {
  var curtop = 0;
  if(obj.offsetParent)
    while(1)
    {
      curtop += obj.offsetTop;
      if(!obj.offsetParent)
        break;
      obj = obj.offsetParent;
    }
  else if(obj.y)
    curtop += obj.y;
  return curtop;
};

/**
 * @private
 * Returns the x-coordinate of the event in a coordinate system where the
 * top-left corner of the page (not the window) is (0,0).
 * Taken from MochiKit.Signal
 */
Dygraph.pageX = function(e) {
  if (e.pageX) {
    return (!e.pageX || e.pageX < 0) ? 0 : e.pageX;
  } else {
    var de = document;
    var b = document.body;
    return e.clientX +
        (de.scrollLeft || b.scrollLeft) -
        (de.clientLeft || 0);
  }
};

/**
 * @private
 * Returns the y-coordinate of the event in a coordinate system where the
 * top-left corner of the page (not the window) is (0,0).
 * Taken from MochiKit.Signal
 */
Dygraph.pageY = function(e) {
  if (e.pageY) {
    return (!e.pageY || e.pageY < 0) ? 0 : e.pageY;
  } else {
    var de = document;
    var b = document.body;
    return e.clientY +
        (de.scrollTop || b.scrollTop) -
        (de.clientTop || 0);
  }
};

/**
 * @private
 * @param { Number } x The number to consider.
 * @return { Boolean } Whether the number is zero or NaN.
 */
// TODO(danvk): rename this function to something like 'isNonZeroNan'.
Dygraph.isOK = function(x) {
  return x && !isNaN(x);
};

/**
 * Number formatting function which mimicks the behavior of %g in printf, i.e.
 * either exponential or fixed format (without trailing 0s) is used depending on
 * the length of the generated string.  The advantage of this format is that
 * there is a predictable upper bound on the resulting string length,
 * significant figures are not dropped, and normal numbers are not displayed in
 * exponential notation.
 *
 * NOTE: JavaScript's native toPrecision() is NOT a drop-in replacement for %g.
 * It creates strings which are too long for absolute values between 10^-4 and
 * 10^-6, e.g. '0.00001' instead of '1e-5'. See tests/number-format.html for
 * output examples.
 *
 * @param {Number} x The number to format
 * @param {Number} opt_precision The precision to use, default 2.
 * @return {String} A string formatted like %g in printf.  The max generated
 *                  string length should be precision + 6 (e.g 1.123e+300).
 */
Dygraph.floatFormat = function(x, opt_precision) {
  // Avoid invalid precision values; [1, 21] is the valid range.
  var p = Math.min(Math.max(1, opt_precision || 2), 21);

  // This is deceptively simple.  The actual algorithm comes from:
  //
  // Max allowed length = p + 4
  // where 4 comes from 'e+n' and '.'.
  //
  // Length of fixed format = 2 + y + p
  // where 2 comes from '0.' and y = # of leading zeroes.
  //
  // Equating the two and solving for y yields y = 2, or 0.00xxxx which is
  // 1.0e-3.
  //
  // Since the behavior of toPrecision() is identical for larger numbers, we
  // don't have to worry about the other bound.
  //
  // Finally, the argument for toExponential() is the number of trailing digits,
  // so we take off 1 for the value before the '.'.
  return (Math.abs(x) < 1.0e-3 && x != 0.0) ?
      x.toExponential(p - 1) : x.toPrecision(p);
};

/**
 * @private
 * Converts '9' to '09' (useful for dates)
 */
Dygraph.zeropad = function(x) {
  if (x < 10) return "0" + x; else return "" + x;
};

/**
 * Return a string version of the hours, minutes and seconds portion of a date.
 * @param {Number} date The JavaScript date (ms since epoch)
 * @return {String} A time of the form "HH:MM:SS"
 * @private
 */
Dygraph.hmsString_ = function(date) {
  var zeropad = Dygraph.zeropad;
  var d = new Date(date);
  if (d.getSeconds()) {
    return zeropad(d.getHours()) + ":" +
           zeropad(d.getMinutes()) + ":" +
           zeropad(d.getSeconds());
  } else {
    return zeropad(d.getHours()) + ":" + zeropad(d.getMinutes());
  }
};

/**
 * Convert a JS date (millis since epoch) to YYYY/MM/DD
 * @param {Number} date The JavaScript date (ms since epoch)
 * @return {String} A date of the form "YYYY/MM/DD"
 * @private
 */
Dygraph.dateString_ = function(date) {
  var zeropad = Dygraph.zeropad;
  var d = new Date(date);

  // Get the year:
  var year = "" + d.getFullYear();
  // Get a 0 padded month string
  var month = zeropad(d.getMonth() + 1);  //months are 0-offset, sigh
  // Get a 0 padded day string
  var day = zeropad(d.getDate());

  var ret = "";
  var frac = d.getHours() * 3600 + d.getMinutes() * 60 + d.getSeconds();
  if (frac) ret = " " + Dygraph.hmsString_(date);

  return year + "/" + month + "/" + day + ret;
};

/**
 * Round a number to the specified number of digits past the decimal point.
 * @param {Number} num The number to round
 * @param {Number} places The number of decimals to which to round
 * @return {Number} The rounded number
 * @private
 */
Dygraph.round_ = function(num, places) {
  var shift = Math.pow(10, places);
  return Math.round(num * shift)/shift;
};

/**
 * @private
 * Implementation of binary search over an array.
 * Currently does not work when val is outside the range of arry's values.
 * @param { Integer } val the value to search for
 * @param { Integer[] } arry is the value over which to search
 * @param { Integer } abs If abs > 0, find the lowest entry greater than val
 * If abs < 0, find the highest entry less than val.
 * if abs == 0, find the entry that equals val.
 * @param { Integer } [low] The first index in arry to consider (optional)
 * @param { Integer } [high] The last index in arry to consider (optional)
 */
Dygraph.binarySearch = function(val, arry, abs, low, high) {
  if (low == null || high == null) {
    low = 0;
    high = arry.length - 1;
  }
  if (low > high) {
    return -1;
  }
  if (abs == null) {
    abs = 0;
  }
  var validIndex = function(idx) {
    return idx >= 0 && idx < arry.length;
  }
  var mid = parseInt((low + high) / 2);
  var element = arry[mid];
  if (element == val) {
    return mid;
  }
  if (element > val) {
    if (abs > 0) {
      // Accept if element > val, but also if prior element < val.
      var idx = mid - 1;
      if (validIndex(idx) && arry[idx] < val) {
        return mid;
      }
    }
    return Dygraph.binarySearch(val, arry, abs, low, mid - 1);
  }
  if (element < val) {
    if (abs < 0) {
      // Accept if element < val, but also if prior element > val.
      var idx = mid + 1;
      if (validIndex(idx) && arry[idx] > val) {
        return mid;
      }
    }
    return Dygraph.binarySearch(val, arry, abs, mid + 1, high);
  }
};

/**
 * @private
 * Parses a date, returning the number of milliseconds since epoch. This can be
 * passed in as an xValueParser in the Dygraph constructor.
 * TODO(danvk): enumerate formats that this understands.
 * @param {String} A date in YYYYMMDD format.
 * @return {Number} Milliseconds since epoch.
 */
Dygraph.dateParser = function(dateStr) {
  var dateStrSlashed;
  var d;
  if (dateStr.search("-") != -1) {  // e.g. '2009-7-12' or '2009-07-12'
    dateStrSlashed = dateStr.replace("-", "/", "g");
    while (dateStrSlashed.search("-") != -1) {
      dateStrSlashed = dateStrSlashed.replace("-", "/");
    }
    d = Dygraph.dateStrToMillis(dateStrSlashed);
  } else if (dateStr.length == 8) {  // e.g. '20090712'
    // TODO(danvk): remove support for this format. It's confusing.
    dateStrSlashed = dateStr.substr(0,4) + "/" + dateStr.substr(4,2)
                       + "/" + dateStr.substr(6,2);
    d = Dygraph.dateStrToMillis(dateStrSlashed);
  } else {
    // Any format that Date.parse will accept, e.g. "2009/07/12" or
    // "2009/07/12 12:34:56"
    d = Dygraph.dateStrToMillis(dateStr);
  }

  if (!d || isNaN(d)) {
    Dygraph.error("Couldn't parse " + dateStr + " as a date");
  }
  return d;
};

/**
 * @private
 * This is identical to JavaScript's built-in Date.parse() method, except that
 * it doesn't get replaced with an incompatible method by aggressive JS
 * libraries like MooTools or Joomla.
 * @param { String } str The date string, e.g. "2011/05/06"
 * @return { Integer } millis since epoch
 */
Dygraph.dateStrToMillis = function(str) {
  return new Date(str).getTime();
};

// These functions are all based on MochiKit.
/**
 * Copies all the properties from o to self.
 *
 * @private
 */
Dygraph.update = function (self, o) {
  if (typeof(o) != 'undefined' && o !== null) {
    for (var k in o) {
      if (o.hasOwnProperty(k)) {
        self[k] = o[k];
      }
    }
  }
  return self;
};

/**
 * @private
 */
Dygraph.isArrayLike = function (o) {
  var typ = typeof(o);
  if (
      (typ != 'object' && !(typ == 'function' &&
        typeof(o.item) == 'function')) ||
      o === null ||
      typeof(o.length) != 'number' ||
      o.nodeType === 3
     ) {
    return false;
  }
  return true;
};

/**
 * @private
 */
Dygraph.isDateLike = function (o) {
  if (typeof(o) != "object" || o === null ||
      typeof(o.getTime) != 'function') {
    return false;
  }
  return true;
};

/**
 * @private
 */
Dygraph.clone = function(o) {
  // TODO(danvk): figure out how MochiKit's version works
  var r = [];
  for (var i = 0; i < o.length; i++) {
    if (Dygraph.isArrayLike(o[i])) {
      r.push(Dygraph.clone(o[i]));
    } else {
      r.push(o[i]);
    }
  }
  return r;
};

/**
 * @private
 * Create a new canvas element. This is more complex than a simple
 * document.createElement("canvas") because of IE and excanvas.
 */
Dygraph.createCanvas = function() {
  var canvas = document.createElement("canvas");

  isIE = (/MSIE/.test(navigator.userAgent) && !window.opera);
  if (isIE && (typeof(G_vmlCanvasManager) != 'undefined')) {
    canvas = G_vmlCanvasManager.initElement(canvas);
  }

  return canvas;
};