package vegeta

import (
	"code.google.com/p/plotinum/plot"
	"code.google.com/p/plotinum/plotter"
	"code.google.com/p/plotinum/plotutil"
	"code.google.com/p/plotinum/vg"
	"code.google.com/p/plotinum/vg/vgsvg"
	"container/list"
	"io"
	"time"
)

type TimingsPlotReporter struct {
	responses *list.List
}

// NewTimingsPlotReporter initializes a TimingsPlotReporter
func NewTimingsPlotReporter() *TimingsPlotReporter {
	return &TimingsPlotReporter{responses: list.New()}
}

// add inserts response to be used in the report, sorted by timestamp.
func (r *TimingsPlotReporter) add(res *result) {
	// Empty list
	if r.responses.Len() == 0 {
		r.responses.PushFront(res)
		return
	}
	// Happened after all others
	if last := r.responses.Back().Value.(*result); last.timestamp.Before(res.timestamp) {
		r.responses.PushBack(res)
		return
	}
	// Happened before all others
	if first := r.responses.Front().Value.(*result); first.timestamp.After(res.timestamp) {
		r.responses.PushFront(res)
		return
	}
	// O(n) worst case insertion time
	for e := r.responses.Front(); e != nil; e = e.Next() {
		needle := e.Value.(*result)
		if res.timestamp.Before(needle.timestamp) {
			r.responses.InsertBefore(res, e)
			return
		}
	}
}

// Report builds up a plot of the response times of the requests
// in SVG format and writes it to out
func (r *TimingsPlotReporter) Report(out io.Writer) error {
	timestamps := make([]time.Time, 0)
	timings := make([]time.Duration, 0)

	for e := r.responses.Front(); e != nil; e = e.Next() {
		r := e.Value.(*result)
		timestamps = append(timestamps, r.timestamp)
		timings = append(timings, r.timing)
	}

	p, err := plot.New()
	if err != nil {
		return err
	}
	pts := make(plotter.XYs, len(timestamps))
	for i := 0; i < len(pts); i++ {
		pts[i].X = timestamps[i].Sub(timestamps[0]).Seconds()
		pts[i].Y = timings[i].Seconds() * 1000
	}

	line, err := plotter.NewLine(pts)
	if err != nil {
		return err
	}
	line.Color = plotutil.Color(1)

	p.Add(line)
	p.X.Padding = vg.Length(3.0)
	p.X.Label.Text = "Time elapsed"
	p.Y.Padding = vg.Length(3.0)
	p.Y.Label.Text = "Latency (ms)"

	w, h := vg.Millimeters(float64(len(timestamps))), vg.Centimeters(12.0)
	canvas := vgsvg.New(w, h)
	p.Draw(plot.MakeDrawArea(canvas))

	_, err = canvas.WriteTo(out)
	return err
}