// JavaScript Document
// basic methods.
ypSimpleScroll.prototype.scrollNorth = function() { this.startScroll(90) }
ypSimpleScroll.prototype.scrollSouth = function() { this.startScroll(270)  }
ypSimpleScroll.prototype.scrollWest  = function() { this.startScroll(180) }
ypSimpleScroll.prototype.scrollEast  = function() { this.startScroll(0)   }


// start scrolling in an arbitrary direction, with an optional arbitrary speed.
// if no speed is provided, the default speed from the constructor parameter is used.
ypSimpleScroll.prototype.startScroll = function(deg, speed) {
  if (this.loaded)
  {
    if (this.aniTimer) window.clearTimeout(this.aniTimer)
    this.overrideScrollAngle(deg)

    this.speed    = speed ? speed : this.origSpeed
    this.lastTime = (new Date()).getTime() - this.y.minRes
    this.aniTimer = window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
  }
}

// kills pending calls to .scroll(), resets speed
ypSimpleScroll.prototype.endScroll = function() {
  if (this.loaded)
  {
    window.clearTimeout(this.aniTimer)
    this.aniTimer = 0;
    this.speed = this.origSpeed
  }
}

// override the current angle from startScroll() with a new angle
// this method should not be used with scrollTo() because it will
// override the angle created by the first two params to scrollTo().
ypSimpleScroll.prototype.overrideScrollAngle = function(deg) {
  if (this.loaded)
  {
    deg = deg % 360
    if (deg % 90 == 0) {
      var cos = deg == 0  ? 1 : deg == 180 ? -1 : 0
      var sin = deg == 90 ? -1 : deg == 270 ? 1 : 0
    } else {
      var angle = deg * Math.PI / 180
      var cos   = Math.cos(angle)
      var sin   = Math.sin(angle)
      sin = -sin
    }
    this.fx = cos / (Math.abs(cos) + Math.abs(sin))
    this.fy = sin / (Math.abs(cos) + Math.abs(sin))
    this.stopH = deg == 90 || deg == 270 ? this.scrollLeft : deg < 90 || deg > 270 ? this.scrollW : 0
    this.stopV = deg == 0 || deg == 180 ? this.scrollTop : deg < 180 ? 0 : this.scrollH
  }
}

// override the speed for the current scroll.
// should not be used with scrollTo, unless you want to 
// override the speed computed from the aniLen param of scrollTo()
ypSimpleScroll.prototype.overrideScrollSpeed = function(speed) {
  if (this.loaded) this.speed = speed
}

// scroll to an arbitrary position in two dimensions over in
// an arbitrary lenth of time.
ypSimpleScroll.prototype.scrollTo = function(stopH, stopV, aniLen) {
  if (this.loaded)
  {
    if (stopH != this.scrollLeft || stopV != this.scrollTop) {
      if (this.aniTimer) window.clearTimeout(this.aniTimer)
      this.lastTime = (new Date()).getTime()
      var dx = Math.abs(stopH - this.scrollLeft)
      var dy = Math.abs(stopV - this.scrollTop)
      var d = Math.sqrt(Math.pow(dx,2) + Math.pow(dy,2))
      this.fx = (stopH - this.scrollLeft) / (dx + dy)
      this.fy = (stopV - this.scrollTop) / (dx + dy)
      this.stopH = stopH
      this.stopV = stopV
      this.speed = d / aniLen * 1000
      window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
    }
  }
}

// jump to an arbitrary position in two dimensions.
ypSimpleScroll.prototype.jumpTo = function(nx, ny) { 
  if (this.loaded)
  {
    nx = Math.min(Math.max(nx, 0), this.scrollW)
    ny = Math.min(Math.max(ny, 0), this.scrollH)
    this.scrollLeft = nx
    this.scrollTop = ny
    if (this.y.ns4)this.content.moveTo(-nx, -ny)
    else {
      this.content.style.left = -nx + "px"
      this.content.style.top = -ny + "px"
    }
  }
}



// =========================================================================
// =============================== private =================================
// =========================================================================

ypSimpleScroll.minRes = 10
ypSimpleScroll.ie  = document.all ? 1 : 0
ypSimpleScroll.ns4 = document.layers ? 1 : 0
ypSimpleScroll.dom = document.getElementById ? 1 : 0
ypSimpleScroll.mac = navigator.platform == "MacPPC"
ypSimpleScroll.mo5 = document.getElementById && !document.all ? 1 : 0

// recursively calls itself to animate
ypSimpleScroll.prototype.scroll = function() {
  this.aniTimer = window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
  var nt = (new Date()).getTime()
  var d = Math.round((nt - this.lastTime) / 1000 * this.speed)
  if (d > 0)
  {
    var nx = d * this.fx + this.scrollLeft
    var ny = d * this.fy + this.scrollTop

    var xOut = (nx >= this.scrollLeft && nx >= this.stopH) || (nx <= this.scrollLeft && nx <= this.stopH)
    var yOut = (ny >= this.scrollTop && ny >= this.stopV)  || (ny <= this.scrollTop && ny <= this.stopV)
    //window.status = nx + " " + this.fx + " " + this.scrollLeft + " " + this.stopH + " | " + ny + " " + this.fy + " " + this.scrollTop + " " + this.stopV + " : " + d
    if (nt - this.lastTime != 0 &&
      ((this.fx == 0 && this.fy == 0) ||
       (this.fy == 0 && xOut) ||
       (this.fx == 0 && yOut) ||
       (this.fx != 0 && this.fy != 0 && xOut && yOut)))
    {
      this.jumpTo(this.stopH, this.stopV)
      this.endScroll()
    }
    else {
      this.jumpTo(nx, ny)
      this.lastTime = nt
    }
  }
}

// constructor
function ypSimpleScroll(id, left, top, width, height, speed, contentWidth, initLeft, initTop)
{
  var y = this.y = ypSimpleScroll
  if (!initLeft)     initLeft     = 0
  if (!initTop)      initTop      = 0
  if (!contentWidth) contentWidth = width

  // fix for netscape4 first-page bug.
  if (document.layers && !y.ns4) history.go(0)

  if (y.ie || y.ns4 || y.dom) {
    this.loaded    = false
    this.id      = id
    this.origSpeed  = speed
    this.aniTimer  = false
    this.op      = ""
    this.lastTime  = 0
    this.clipH    = height
    this.clipW    = width
    this.scrollTop  = initTop
    this.scrollLeft  = initLeft

    // global reference to this object
    this.gRef = "ypSimpleScroll_"+id
    eval(this.gRef+"=this")

    var d = document
    d.write('<style type="text/css">')
    d.write('#' + this.id + 'Container { left:' + left + 'px; top:' + top + 'px; width:' + width + 'px; height:' + height + 'px; clip:rect(0 ' + width + ' ' + height + ' 0); overflow:hidden; }')
    d.write('#' + this.id + 'Container, #' + this.id + 'Content { position:absolute; }')
    d.write('#' + this.id + 'Content { left:' + (-initLeft) + 'px; top:' + (-initTop) + 'px; width:' + contentWidth + 'px; }')
    d.write('</style>')
  }
}

// once the nceesary objects are present in the DOM, this gathers some info about them.
ypSimpleScroll.prototype.load = function() {
  var d, lyrId1, lyrId2

  d = document
  lyrId1 = this.id + "Container"
  lyrId2 = this.id + "Content"

  this.container  = this.y.dom ? d.getElementById(lyrId1) : this.y.ie ? d.all[lyrId1] : d.layers[lyrId1]
  this.content  = obj2 = this.y.ns4 ? this.container.layers[lyrId2] : this.y.ie ? d.all[lyrId2] : d.getElementById(lyrId2)
  this.docH    = Math.max(this.y.ns4 ? this.content.document.height : this.content.offsetHeight, this.clipH)
  this.docW    = Math.max(this.y.ns4 ? this.content.document.width  : this.content.offsetWidth,  this.clipW)
  this.scrollH  = this.docH - this.clipH
  this.scrollW  = this.docW - this.clipW
  this.loaded    = true
  this.scrollLeft = Math.max(Math.min(this.scrollLeft, this.scrollW),0)
  this.scrollTop  = Math.max(Math.min(this.scrollTop, this.scrollH),0)
  this.jumpTo(this.scrollLeft, this.scrollTop)
}