package utilities

import "errors"

/*
The Pair and PairList have been taken from google groups forum,
https://groups.google.com/forum/#!topic/golang-nuts/FT7cjmcL7gw
*/

// Utility struct that helps in sorting the available power by value.
type Pair struct {
  Key string
  Value float64
}

// A slice of pairs that implements the sort.Interface to sort by value.
type PairList []Pair

// Swap pairs in the PairList
func (plist PairList) Swap(i, j int) {
  plist[i], plist[j] = plist[j], plist[i]
}

// function to return the length of the pairlist.
func (plist PairList) Len() int {
  return len(plist)
}

// function to compare two elements in pairlist.
func (plist PairList) Less(i, j int) bool {
  return plist[i].Value < plist[j].Value
}

// convert a PairList to a map[string]float64
func OrderedKeys(plist PairList) ([]string, error) {
  // Validation
  if plist == nil {
    return nil, errors.New("Invalid argument: plist")
  }
  ordered_keys := make([]string, len(plist))
  for _, pair := range plist {
    ordered_keys = append(ordered_keys, pair.Key)
  }
  return ordered_keys, nil
}

// determine the max value
func Max(a, b float64) float64 {
  if a > b {
    return a
  } else {
    return b
  }
}