// Package triangle determines what kind of triangle three side lengths make.
package triangle

import "math"

// An enumeration of triangle types
const (
	NaT Kind = iota // Not a triangle
	Equ             // Equlateral
	Iso             // Isometric
	Sca             // Scalene

	testVersion = 2
)

// A Kind is an integer representation of the kind of triangle.
type Kind int

// KindFromSides determines whether the three side lengths given
// constitute a triangle and if so, what type of triangle it is.
func KindFromSides(a, b, c float64) (k Kind) {
	// Return NaT when any side is zero, negative, infinite, or NaN.
	for _, f := range []float64{a, b, c} {
		if f <= 0 || f != f || math.IsInf(f, 0) {
			return NaT
		}
	}
	switch {
	// Return NaT if the sides fail triangle inequality tests.
	case a+b < c || b+c < a || a+c < b:
		k = NaT
	case a == b && b == c: // 3 equal length sides (Equ)
		k = Equ
	case a == b || b == c || a == c: // 2 equal length sides (Iso)
		k = Iso
	case a != b && b != c && a != c: // No equal length sides (Sca)
		k = Sca
	}
	return k
}

// Iteration 2 benkmark results:
//
// PASS
// BenchmarkKind-12	 2000000	       651 ns/op
//