package app

import (
	"fmt"
	"net/netip"
	"strings"
)

func normalizeTransportIntent(in TransportPolicyIntent) (TransportPolicyIntent, string, netip.Prefix, error) {
	out := TransportPolicyIntent{
		SelectorType:  strings.ToLower(strings.TrimSpace(in.SelectorType)),
		SelectorValue: strings.TrimSpace(in.SelectorValue),
		ClientID:      sanitizeID(in.ClientID),
		Priority:      in.Priority,
		Mode:          strings.ToLower(strings.TrimSpace(in.Mode)),
	}
	if out.ClientID == "" {
		return out, "", netip.Prefix{}, fmt.Errorf("missing client_id")
	}
	if out.Priority <= 0 {
		out.Priority = 100
	}
	if out.Mode == "" {
		out.Mode = "strict"
	}
	if out.Mode != "strict" && out.Mode != "fallback" {
		return out, "", netip.Prefix{}, fmt.Errorf("mode must be strict|fallback")
	}
	switch out.SelectorType {
	case "domain":
		out.SelectorValue = strings.ToLower(out.SelectorValue)
	case "cidr":
		pfx, err := parseIntentCIDR(out.SelectorValue)
		if err != nil {
			return out, "", netip.Prefix{}, err
		}
		out.SelectorValue = pfx.String()
		return out, out.SelectorType + ":" + out.SelectorValue, pfx, nil
	case "app_key", "cgroup", "uid":
		// keep as-is
	default:
		return out, "", netip.Prefix{}, fmt.Errorf("selector_type must be domain|cidr|app_key|cgroup|uid")
	}
	if out.SelectorValue == "" {
		return out, "", netip.Prefix{}, fmt.Errorf("selector_value is empty")
	}
	return out, out.SelectorType + ":" + out.SelectorValue, netip.Prefix{}, nil
}

func parseIntentCIDR(raw string) (netip.Prefix, error) {
	v := strings.TrimSpace(raw)
	if v == "" {
		return netip.Prefix{}, fmt.Errorf("selector_value is empty")
	}
	if strings.Contains(v, "/") {
		pfx, err := netip.ParsePrefix(v)
		if err != nil || !pfx.Addr().Is4() {
			return netip.Prefix{}, fmt.Errorf("invalid cidr: %q", raw)
		}
		return pfx.Masked(), nil
	}
	ip, err := netip.ParseAddr(v)
	if err != nil || !ip.Is4() {
		return netip.Prefix{}, fmt.Errorf("invalid cidr: %q", raw)
	}
	return netip.PrefixFrom(ip, 32), nil
}

func prefixOverlap(a, b netip.Prefix) bool {
	if !a.IsValid() || !b.IsValid() {
		return false
	}
	return a.Contains(b.Addr()) || b.Contains(a.Addr())
}