package config

import (
	"fmt"
	"strconv"
	"strings"
)

// CompareVersions compares two semver-ish version strings.
//
// Accepts "v1.2.3", "1.2.3", "v1.2.3-rc1" (suffix ignored), with missing
// components defaulting to 0 ("v1" == "1.0.0"). Returns -1 if a < b, 0 if
// equal, +1 if a > b. Returns an error if either argument can't be parsed
// at all.
//
// Used by apply.go to enforce MinCompatibleVersion. Pre-release suffix
// handling is deliberately simple — we ignore it, treating "v1.2.3-rc1"
// equal to "v1.2.3". Edge case: production releases should never carry
// a pre-release suffix, and dev releases are the consumer's responsibility.
func CompareVersions(a, b string) (int, error) {
	pa, err := parseVersion(a)
	if err != nil {
		return 0, fmt.Errorf("parse %q: %w", a, err)
	}
	pb, err := parseVersion(b)
	if err != nil {
		return 0, fmt.Errorf("parse %q: %w", b, err)
	}
	for i := 0; i < 3; i++ {
		if pa[i] < pb[i] {
			return -1, nil
		}
		if pa[i] > pb[i] {
			return 1, nil
		}
	}
	return 0, nil
}

func parseVersion(s string) ([3]int, error) {
	var out [3]int
	s = strings.TrimSpace(s)
	s = strings.TrimPrefix(s, "v")
	// Drop pre-release suffix: "1.2.3-rc1" -> "1.2.3"
	if i := strings.IndexAny(s, "-+"); i >= 0 {
		s = s[:i]
	}
	parts := strings.SplitN(s, ".", 3)
	for i, p := range parts {
		n, err := strconv.Atoi(p)
		if err != nil {
			return out, fmt.Errorf("component %q not numeric", p)
		}
		if n < 0 {
			return out, fmt.Errorf("component %d negative", n)
		}
		out[i] = n
	}
	return out, nil
}