package main

import (
  "fmt"
  "os"
)

type OTS_DataPoint struct {
  TimeStamp float64
  Rate      float64
}

type OTS_Data struct {
  TSData []OTS_DataPoint
}

/* Functions for the sort interface. */
func (obj *OTS_Data) Len () int {
  return (len (obj.TSData))
}

func (obj *OTS_Data) Less (i, j int) bool {
  if obj.TSData[i].TimeStamp < obj.TSData[j].TimeStamp {
    return true
  }
  return false
}

func (obj *OTS_Data) Swap (i, j int) {
  tmp := obj.TSData[i]
  obj.TSData[i] = obj.TSData[j]
  obj.TSData[j] = tmp
}

func Fmod64 (a float64, b float64) float64 {
  tmp := int (a / b)
  return b * float64 (tmp)
}

func (obj *OTS_Data) Write (name string) os.Error {
  fd, err := os.OpenFile(name, os.O_WRONLY, 0666)
  if err != nil {
    return err
  }

  for i := 0; i < len (obj.TSData); i++ {
    data_point := obj.TSData[i]
    str := fmt.Sprintf ("%.3f,%g\n", data_point.TimeStamp, data_point.Rate)

    fd.WriteString (str)
  }

  fd.Close ()
  return nil
}

func ReadFile (name string) (obj *OTS_Data, err os.Error) {
}

func (raw_data *OTS_Data) Consolidate (interval float64) *OTS_Data {
  if interval <= 0.0 {
    return nil
  }

  ts_raw_first := raw_data.TSData[0].TimeStamp
  ts_raw_last  := ts_raw_first

  /* Determine the first and last data point.
   * XXX: In the future, this should be a sorted list! */
  for i := 1; i < len (raw_data.TSData); i++ {
    data_point := raw_data.TSData[i]

    if ts_raw_first > data_point.TimeStamp {
      ts_raw_first = data_point.TimeStamp
    }

    if ts_raw_last < data_point.TimeStamp {
      ts_raw_last = data_point.TimeStamp
    }
  }

  fmt.Printf ("ts_raw_first = %g; ts_raw_last = %g;\n",
      ts_raw_first, ts_raw_last)

  /* Determine the timespan the consolidated data will span. */
  ts_csl_first := Fmod64 (ts_raw_first, interval)
  ts_csl_last  := Fmod64 (ts_raw_last,  interval)
  if ts_csl_last < ts_raw_last {
    ts_csl_last += interval
  }

  fmt.Printf ("ts_csl_first = %g; ts_csl_last = %g;\n",
      ts_csl_first, ts_csl_last)

  intervals_num := int ((ts_csl_last - ts_csl_first) / interval)
  fmt.Printf ("Got a %gs timespan (%d intervals).\n",
      ts_csl_last - ts_csl_first, intervals_num)

  /* Allocate return structure */
  ret_data := new (OTS_Data)
  ret_data.TSData = make ([]OTS_DataPoint, intervals_num)

  /* FIXME: This is currently a O(n^2) algorithm. It should instead be a O(n)
   * algorithm. This is possible if raw_data is sorted (which, obviously, is a
   * O(n log(n)) task). */
  for i := 0; i < intervals_num; i++ {
      ts := ts_csl_first + (float64 (i) * interval)
      sum := 0.0
      num := 0.0

      fmt.Printf ("Building data for interval %g.\n", ts)

      ret_data.TSData[i].TimeStamp = ts

      for j := 0; j < len (raw_data.TSData); j++ {
        data_point := raw_data.TSData[j]

        if ((data_point.TimeStamp < ts) || (data_point.TimeStamp >= (ts + interval))) {
          continue
        }

        sum += data_point.Rate
        num += 1.0
      }

      /* TODO: Be more clever about how this consolidated rate is computed. */
      if num > 0.0 {
        ret_data.TSData[i].Rate = sum / num
      }
  }

  return ret_data
}

func (obj *OTS_Data) Print () {
  for i := 0; i < len (obj.TSData); i++ {
    data_point := obj.TSData[i]
    fmt.Printf ("[%g] %g\n", data_point.TimeStamp, data_point.Rate)
  }
} /* Print () */

func main () {
  var data_points []OTS_DataPoint
  var raw_data     *OTS_Data
  var new_data     *OTS_Data

  data_points = []OTS_DataPoint {
    {0.0,  1.0},
    {1.0,  2.0},
    {2.0,  5.0},
    {3.0,  8.0},
    {4.0,  0.0},
    {5.0,  3.0}}

  raw_data = new (OTS_Data)
  raw_data.TSData = data_points

  new_data = raw_data.Consolidate (2.0)

  new_data.Print()
}