package woocommerce

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"strings"
)

var (
	ErrInvalidStoreURL = errors.New("invalid store url")
	ErrBlockedStoreURL = errors.New("store url host is not allowed")
)

// NormalizeStoreURL validates and normalizes a WooCommerce store base URL.
// Requires https (http only for localhost). Blocks metadata and private ranges (SSRF).
func NormalizeStoreURL(raw string) (string, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return "", ErrInvalidStoreURL
	}
	if !strings.Contains(raw, "://") {
		raw = "https://" + raw
	}
	u, err := url.Parse(raw)
	if err != nil || u.Host == "" {
		return "", ErrInvalidStoreURL
	}
	scheme := strings.ToLower(u.Scheme)
	if scheme != "https" && scheme != "http" {
		return "", ErrInvalidStoreURL
	}
	host := strings.ToLower(u.Hostname())
	if host == "" {
		return "", ErrInvalidStoreURL
	}
	if host == "metadata.google.internal" || host == "metadata" {
		return "", ErrBlockedStoreURL
	}
	ips, err := resolveHostIPs(host)
	if err != nil {
		if isLiteralIP(host) {
			return "", err
		}
	} else {
		for _, ip := range ips {
			if !allowedIP(ip, host) {
				return "", ErrBlockedStoreURL
			}
		}
	}
	if scheme == "http" && !isLoopbackHost(host) {
		return "", fmt.Errorf("%w: https required (http only allowed for localhost)", ErrInvalidStoreURL)
	}
	u.Scheme = scheme
	if u.Port() != "" {
		u.Host = net.JoinHostPort(u.Hostname(), u.Port())
	} else {
		u.Host = u.Hostname()
	}
	u.Path = strings.TrimRight(u.Path, "/")
	u.RawQuery = ""
	u.Fragment = ""
	u.User = nil
	return u.String(), nil
}

func resolveHostIPs(host string) ([]net.IP, error) {
	if ip := net.ParseIP(host); ip != nil {
		return []net.IP{ip}, nil
	}
	addrs, err := net.LookupIP(host)
	if err != nil {
		return nil, ErrInvalidStoreURL
	}
	return addrs, nil
}

func isLiteralIP(host string) bool {
	return net.ParseIP(host) != nil
}

func isLoopbackHost(host string) bool {
	if host == "localhost" {
		return true
	}
	ip := net.ParseIP(host)
	return ip != nil && ip.IsLoopback()
}

func allowedIP(ip net.IP, host string) bool {
	if ip.IsLoopback() {
		return isLoopbackHost(host)
	}
	if ip.IsUnspecified() || ip.IsMulticast() || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() {
		return false
	}
	if ip4 := ip.To4(); ip4 != nil {
		if ip4[0] == 10 {
			return false
		}
		if ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31 {
			return false
		}
		if ip4[0] == 192 && ip4[1] == 168 {
			return false
		}
		if ip4[0] == 169 && ip4[1] == 254 {
			return false
		}
		if ip4[0] == 100 && ip4[1] >= 64 && ip4[1] <= 127 {
			return false
		}
	} else if ip.IsPrivate() {
		return false
	}
	return true
}