registerKeyboardHandler = function(callback) {
  var callback = callback;
  d3.select(window).on("keydown", callback);  
};

SimpleGraph = function(elemid, options) {
  var self = this;
  this.chart = document.getElementById(elemid);
  this.cx = this.chart.clientWidth;
  this.cy = this.chart.clientHeight;
  this.options = options || {};
  this.options.xmax = options.xmax || 30;
  this.options.xmin = options.xmin || 0;
  this.options.ymax = options.ymax || 10;
  this.options.ymin = options.ymin || 0;

  this.padding = {
     "top":    this.options.title  ? 40 : 20,
     "right":                 30,
     "bottom": this.options.xlabel ? 60 : 10,
     "left":   this.options.ylabel ? 70 : 45
  };

  this.size = {
    "width":  this.cx - this.padding.left - this.padding.right,
    "height": this.cy - this.padding.top  - this.padding.bottom
  };

  // x-scale
  this.x = d3.scale.linear()
      .domain([this.options.xmin, this.options.xmax])
      .range([0, this.size.width]);

  // drag x-axis logic
  this.downx = Math.NaN;

  // y-scale (inverted domain)
  this.y = d3.scale.linear()
      .domain([this.options.ymax, this.options.ymin])
      .nice()
      .range([0, this.size.height])
      .nice();

  // drag y-axis logic
  this.downy = Math.NaN;

  this.dragged = this.selected = null;

  this.line = d3.svg.line()
      .x(function(d, i) { return this.x(this.points[i].x); })
      .y(function(d, i) { return this.y(this.points[i].y); });

  var xrange =  (this.options.xmax - this.options.xmin),
      yrange2 = (this.options.ymax - this.options.ymin) / 2,
      yrange4 = yrange2 / 2,
      datacount = this.size.width/30;

  this.points = d3.range(datacount).map(function(i) { 
    return { x: i * xrange / datacount, y: this.options.ymin + yrange4 + Math.random() * yrange2 }; 
  }, self);

  this.vis = d3.select(this.chart).append("svg")
      .attr("width",  this.cx)
      .attr("height", this.cy)
      .append("g")
        .attr("transform", "translate(" + this.padding.left + "," + this.padding.top + ")");

  this.plot = this.vis.append("rect")
      .attr("width", this.size.width)
      .attr("height", this.size.height)
      .style("fill", "#EEEEEE")
      .attr("pointer-events", "all")
      .on("mousedown.drag", self.plot_drag())
      .on("touchstart.drag", self.plot_drag())
      this.plot.call(d3.behavior.zoom().x(this.x).y(this.y).on("zoom", this.redraw()));

  this.vis.append("svg")
      .attr("top", 0)
      .attr("left", 0)
      .attr("width", this.size.width)
      .attr("height", this.size.height)
      .attr("viewBox", "0 0 "+this.size.width+" "+this.size.height)
      .attr("class", "line")
      .append("path")
          .attr("class", "line")
          .attr("d", this.line(this.points));

  // add Chart Title
  if (this.options.title) {
    this.vis.append("text")
        .attr("class", "axis")
        .text(this.options.title)
        .attr("x", this.size.width/2)
        .attr("dy","-0.8em")
        .style("text-anchor","middle");
  }

  // Add the x-axis label
  if (this.options.xlabel) {
    this.vis.append("text")
        .attr("class", "axis")
        .text(this.options.xlabel)
        .attr("x", this.size.width/2)
        .attr("y", this.size.height)
        .attr("dy","2.4em")
        .style("text-anchor","middle");
  }

  // add y-axis label
  if (this.options.ylabel) {
    this.vis.append("g").append("text")
        .attr("class", "axis")
        .text(this.options.ylabel)
        .style("text-anchor","middle")
        .attr("transform","translate(" + -40 + " " + this.size.height/2+") rotate(-90)");
  }

  d3.select(this.chart)
      .on("mousemove.drag", self.mousemove())
      .on("touchmove.drag", self.mousemove())
      .on("mouseup.drag",   self.mouseup())
      .on("touchend.drag",  self.mouseup());

  this.redraw()();
};
  
//
// SimpleGraph methods
//

SimpleGraph.prototype.plot_drag = function() {
  var self = this;
  return function() {
    registerKeyboardHandler(self.keydown());
    d3.select('body').style("cursor", "move");
    if (d3.event.altKey) {
      var p = d3.mouse(self.vis.node());
      var newpoint = {};
      newpoint.x = self.x.invert(Math.max(0, Math.min(self.size.width,  p[0])));
      newpoint.y = self.y.invert(Math.max(0, Math.min(self.size.height, p[1])));
      self.points.push(newpoint);
      self.points.sort(function(a, b) {
        if (a.x < b.x) { return -1 };
        if (a.x > b.x) { return  1 };
        return 0
      });
      self.selected = newpoint;
      self.update();
      d3.event.preventDefault();
      d3.event.stopPropagation();
    }    
  }
};

SimpleGraph.prototype.update = function() {
  var self = this;
  var lines = this.vis.select("path").attr("d", this.line(this.points));
        

  var circle = this.vis.select("svg").selectAll("circle")
      .data(this.points);

  circle.enter().append("circle")
      .attr("class", function(d) { return d === self.selected ? "selected" : null; })
      .attr("cx",    function(d) { return self.x(d.x); })
      .attr("cy",    function(d) { return self.y(d.y); })
      .attr("r", 10.0)
      .style("cursor", "ns-resize")
      .on("mousedown.drag",  self.datapoint_drag())
      .on("touchstart.drag", self.datapoint_drag());

  circle
      .attr("class", function(d) { return d === self.selected ? "selected" : null; })
      .attr("cx",    function(d) { 
        return self.x(d.x); })
      .attr("cy",    function(d) { return self.y(d.y); });

  circle.exit().remove();

  if (d3.event && d3.event.keyCode) {
    d3.event.preventDefault();
    d3.event.stopPropagation();
  }
}

SimpleGraph.prototype.datapoint_drag = function() {
  var self = this;
  return function(d) {
    registerKeyboardHandler(self.keydown());
    document.onselectstart = function() { return false; };
    self.selected = self.dragged = d;
    self.update();
    
  }
};

SimpleGraph.prototype.mousemove = function() {
  var self = this;
  return function() {
    var p = d3.mouse(self.vis[0][0]),
        t = d3.event.changedTouches;
    
    if (self.dragged) {
      self.dragged.y = self.y.invert(Math.max(0, Math.min(self.size.height, p[1])));
      self.update();
    };
    if (!isNaN(self.downx)) {
      d3.select('body').style("cursor", "ew-resize");
      var rupx = self.x.invert(p[0]),
          xaxis1 = self.x.domain()[0],
          xaxis2 = self.x.domain()[1],
          xextent = xaxis2 - xaxis1;
      if (rupx != 0) {
        var changex, new_domain;
        changex = self.downx / rupx;
        new_domain = [xaxis1, xaxis1 + (xextent * changex)];
        self.x.domain(new_domain);
        self.redraw()();
      }
      d3.event.preventDefault();
      d3.event.stopPropagation();
    };
    if (!isNaN(self.downy)) {
      d3.select('body').style("cursor", "ns-resize");
      var rupy = self.y.invert(p[1]),
          yaxis1 = self.y.domain()[1],
          yaxis2 = self.y.domain()[0],
          yextent = yaxis2 - yaxis1;
      if (rupy != 0) {
        var changey, new_domain;
        changey = self.downy / rupy;
        new_domain = [yaxis1 + (yextent * changey), yaxis1];
        self.y.domain(new_domain);
        self.redraw()();
      }
      d3.event.preventDefault();
      d3.event.stopPropagation();
    }
  }
};

SimpleGraph.prototype.mouseup = function() {
  var self = this;
  return function() {
    document.onselectstart = function() { return true; };
    d3.select('body').style("cursor", "auto");
    d3.select('body').style("cursor", "auto");
    if (!isNaN(self.downx)) {
      self.redraw()();
      self.downx = Math.NaN;
      d3.event.preventDefault();
      d3.event.stopPropagation();
    };
    if (!isNaN(self.downy)) {
      self.redraw()();
      self.downy = Math.NaN;
      d3.event.preventDefault();
      d3.event.stopPropagation();
    }
    if (self.dragged) { 
      self.dragged = null 
    }
  }
}

SimpleGraph.prototype.keydown = function() {
  var self = this;
  return function() {
    if (!self.selected) return;
    switch (d3.event.keyCode) {
      case 8: // backspace
      case 46: { // delete
        var i = self.points.indexOf(self.selected);
        self.points.splice(i, 1);
        self.selected = self.points.length ? self.points[i > 0 ? i - 1 : 0] : null;
        self.update();
        break;
      }
    }
  }
};

SimpleGraph.prototype.redraw = function() {
  var self = this;
  return function() {
    var tx = function(d) { 
      return "translate(" + self.x(d) + ",0)"; 
    },
    ty = function(d) { 
      return "translate(0," + self.y(d) + ")";
    },
    stroke = function(d) { 
      return d ? "#ccc" : "#666"; 
    },
    fx = self.x.tickFormat(10),
    fy = self.y.tickFormat(10);

    // Regenerate x-ticks…
    var gx = self.vis.selectAll("g.x")
        .data(self.x.ticks(10), String)
        .attr("transform", tx);

    gx.select("text")
        .text(fx);

    var gxe = gx.enter().insert("g", "a")
        .attr("class", "x")
        .attr("transform", tx);

    gxe.append("line")
        .attr("stroke", stroke)
        .attr("y1", 0)
        .attr("y2", self.size.height);

    gxe.append("text")
        .attr("class", "axis")
        .attr("y", self.size.height)
        .attr("dy", "1em")
        .attr("text-anchor", "middle")
        .text(fx)
        .style("cursor", "ew-resize")
        .on("mouseover", function(d) { d3.select(this).style("font-weight", "bold");})
        .on("mouseout",  function(d) { d3.select(this).style("font-weight", "normal");})
        .on("mousedown.drag",  self.xaxis_drag())
        .on("touchstart.drag", self.xaxis_drag());

    gx.exit().remove();

    // Regenerate y-ticks…
    var gy = self.vis.selectAll("g.y")
        .data(self.y.ticks(10), String)
        .attr("transform", ty);

    gy.select("text")
        .text(fy);

    var gye = gy.enter().insert("g", "a")
        .attr("class", "y")
        .attr("transform", ty)
        .attr("background-fill", "#FFEEB6");

    gye.append("line")
        .attr("stroke", stroke)
        .attr("x1", 0)
        .attr("x2", self.size.width);

    gye.append("text")
        .attr("class", "axis")
        .attr("x", -3)
        .attr("dy", ".35em")
        .attr("text-anchor", "end")
        .text(fy)
        .style("cursor", "ns-resize")
        .on("mouseover", function(d) { d3.select(this).style("font-weight", "bold");})
        .on("mouseout",  function(d) { d3.select(this).style("font-weight", "normal");})
        .on("mousedown.drag",  self.yaxis_drag())
        .on("touchstart.drag", self.yaxis_drag());

    gy.exit().remove();
    self.plot.call(d3.behavior.zoom().x(self.x).y(self.y).on("zoom", self.redraw()));
    self.update();    
  }  
}

SimpleGraph.prototype.xaxis_drag = function() {
  var self = this;
  return function(d) {
    document.onselectstart = function() { return false; };
    var p = d3.mouse(self.vis[0][0]);
    self.downx = self.x.invert(p[0]);
  }
};

SimpleGraph.prototype.yaxis_drag = function(d) {
  var self = this;
  return function(d) {
    document.onselectstart = function() { return false; };
    var p = d3.mouse(self.vis[0][0]);
    self.downy = self.y.invert(p[1]);
  }
};