package proto

import (
	"strconv"
	"strings"
)

// versionParts reads "0.2.5" (a leading v and a "-suffix" are allowed) as
// numbers; ok is false for anything that is not a dotted number.
func versionParts(v string) (parts []int, ok bool) {
	v = strings.TrimPrefix(strings.TrimSpace(v), "v")
	if i := strings.IndexAny(v, "-+"); i >= 0 {
		v = v[:i]
	}
	if v == "" {
		return nil, false
	}
	for _, p := range strings.Split(v, ".") {
		n, err := strconv.Atoi(p)
		if err != nil || n < 0 {
			return nil, false
		}
		parts = append(parts, n)
	}
	return parts, true
}

// VersionNewer reports whether version a is higher than b. Anything that is
// not a dotted number (a build named "dev", an empty string) is never newer
// and never older - so a program is never "updated" down, or from a guess.
func VersionNewer(a, b string) bool {
	pa, okA := versionParts(a)
	pb, okB := versionParts(b)
	if !okA || !okB {
		return false
	}
	for i := 0; i < len(pa) || i < len(pb); i++ {
		var x, y int
		if i < len(pa) {
			x = pa[i]
		}
		if i < len(pb) {
			y = pb[i]
		}
		if x != y {
			return x > y
		}
	}
	return false
}