package firewall

import (
	"fmt"
	"net"
	"regexp"
	"strconv"
	"strings"
	"time"
)

func inferProtocol(v map[string]any) string {
	inv, p := plain(strings.ToLower(text(v, "protocol")))
	family, _ := v["ip_version"].(float64)
	if p == "6" {
		p = "tcp"
	}
	if p == "17" {
		p = "udp"
	}
	if p == "1" {
		p = "icmp"
	}
	if p == "58" || p == "icmpv6" {
		p = "ipv6-icmp"
	}
	if family == 6 && p == "icmp" {
		p = "ipv6-icmp"
	}
	if p == "" || p == "all" {
		if text(v, "icmp_options") != "" {
			p = "icmp"
			if family == 6 {
				p = "ipv6-icmp"
			}
		} else if text(v, "src_port") != "" || text(v, "dst_port") != "" || text(v, "any_port") != "" || text(v, "tcp_flags") != "" || text(v, "tcp_mss") != "" || text(v, "action") == "change-mss" {
			p = "tcp"
		}
	}
	if inv != "" {
		return "!" + p
	}
	return p
}
func parseRange(s string, max int) (string, error) {
	s = portValue(s)
	parts := strings.Split(s, ":")
	if len(parts) > 2 {
		return "", fmt.Errorf("invalid range")
	}
	for _, p := range parts {
		if e := intRange(p, 0, max); e != nil {
			return "", e
		}
	}
	if len(parts) == 2 {
		a, _ := strconv.Atoi(parts[0])
		b, _ := strconv.Atoi(parts[1])
		if a > b {
			return "", fmt.Errorf("reversed range")
		}
	}
	return s, nil
}
func tcpFlags(s string) (string, string, error) {
	var mask, on []string
	for _, part := range strings.Split(strings.ToUpper(s), ",") {
		inv, p := plain(strings.TrimSpace(part))
		switch p {
		case "SYN", "ACK", "FIN", "RST", "URG", "PSH":
		default:
			return "", "", fmt.Errorf("unsupported TCP flag %q", p)
		}
		mask = append(mask, p)
		if inv == "" {
			on = append(on, p)
		}
	}
	set := "NONE"
	if len(on) > 0 {
		set = strings.Join(on, ",")
	}
	return strings.Join(mask, ","), set, nil
}
func ttlParts(s string) (string, string, error) {
	op := "eq"
	n := s
	if i := strings.IndexByte(s, ':'); i >= 0 {
		n = s[i+1:]
		switch s[:i] {
		case "equal":
			op = "eq"
		case "less-than":
			op = "lt"
		case "greater-than":
			op = "gt"
		default:
			return "", "", fmt.Errorf("TTL expects equal:N, less-than:N, or greater-than:N")
		}
	}
	if err := intRange(n, 0, 255); err != nil {
		return "", "", err
	}
	return op, n, nil
}

var ratePattern = regexp.MustCompile(`^([0-9]+(?:\.[0-9]+)?)(?:/([0-9]*)(s|sec|second|m|min|minute|h|hour))?$`)

func rateParts(s string) (string, string, error) {
	s = strings.TrimSuffix(s, ":packet")
	parts := strings.Split(s, ",")
	if len(parts) > 2 {
		return "", "", fmt.Errorf("limit expects rate[,burst], for example 100/second,5")
	}
	m := ratePattern.FindStringSubmatch(parts[0])
	if m == nil {
		return "", "", fmt.Errorf("invalid packet rate")
	}
	rate, _ := strconv.ParseFloat(m[1], 64)
	period := 1.0
	if m[2] != "" {
		period, _ = strconv.ParseFloat(m[2], 64)
	}
	switch m[3] {
	case "m", "min", "minute":
		period *= 60
	case "h", "hour":
		period *= 3600
	}
	if period <= 0 || rate <= 0 {
		return "", "", fmt.Errorf("rate must be positive")
	}
	burst := "5"
	if len(parts) == 2 {
		burst = parts[1]
		if e := intRange(burst, 1, 2147483647); e != nil {
			return "", "", e
		}
	}
	return strconv.FormatFloat(rate/period, 'f', 6, 64) + "/second", burst, nil
}

var weekdays = map[string]string{"sun": "Sun", "mon": "Mon", "tue": "Tue", "wed": "Wed", "thu": "Thu", "fri": "Fri", "sat": "Sat"}

func clock(s string) (string, error) {
	layout := "15:04:05"
	if len(s) == 5 {
		layout = "15:04"
	}
	t, e := time.Parse(layout, s)
	if e != nil {
		return "", fmt.Errorf("time must use HH:MM:SS")
	}
	return t.Format("15:04:05"), nil
}
func validateAdvanced(v map[string]any) error {
	p := inferProtocol(v)
	_, proto := plain(p)
	if proto == "ipv6-icmp" && v["ip_version"] != float64(6) {
		return fmt.Errorf("ICMPv6 requires IPv6")
	}
	if p != "" && p != "all" && !safeIdentifier.MatchString(proto) {
		return fmt.Errorf("invalid protocol")
	}
	if strings.HasPrefix(p, "!") && proto == "all" {
		return fmt.Errorf("cannot invert the all-protocols selection")
	}
	ports := text(v, "src_port") != "" || text(v, "dst_port") != "" || text(v, "any_port") != ""
	if ports && (strings.HasPrefix(p, "!") || (proto != "tcp" && proto != "udp")) {
		return fmt.Errorf("port matching requires positive TCP or UDP protocol")
	}
	if text(v, "tcp_flags") != "" || text(v, "tcp_mss") != "" {
		if p != "tcp" {
			return fmt.Errorf("TCP flags/MSS matching requires TCP")
		}
	}
	if s := text(v, "tcp_flags"); s != "" {
		if _, _, e := tcpFlags(s); e != nil {
			return e
		}
	}
	if text(v, "action") == "change-mss" && text(v, "tcp_flags") != "" {
		_, on, _ := tcpFlags(text(v, "tcp_flags"))
		found := false
		for _, flag := range strings.Split(on, ",") {
			found = found || flag == "SYN"
		}
		if !found {
			return fmt.Errorf("MSS rewriting requires SYN in the TCP flags")
		}
	}
	if len(text(v, "log_prefix")) > 29 {
		return fmt.Errorf("log prefix is limited to 29 bytes")
	}
	if len(text(v, "content")) > 128 {
		return fmt.Errorf("content matching is limited to 128 bytes")
	}

	for _, key := range []string{"tcp_mss", "packet_size"} {
		if s := text(v, key); s != "" {
			if _, e := parseRange(s, 65535); e != nil {
				return fmt.Errorf("%s: %w", key, e)
			}
		}
	}
	if s := text(v, "src_mac_address"); s != "" {
		_, s = plain(s)
		if _, e := net.ParseMAC(s); e != nil {
			return fmt.Errorf("invalid source MAC")
		}
	}
	if s := text(v, "dscp"); s != "" {
		if e := intRange(s, 0, 63); e != nil {
			return e
		}
	}
	if s := text(v, "tos"); s != "" {
		s = normalizeTOS(s)
		parts := strings.Split(s, "/")
		if len(parts) > 2 {
			return fmt.Errorf("invalid TOS")
		}
		for _, n := range parts {
			if _, e := strconv.ParseUint(n, 0, 8); e != nil {
				return fmt.Errorf("invalid TOS byte or mask")
			}
		}
	}
	if s := text(v, "connection_type"); s != "" && !safeIdentifier.MatchString(s) {
		return fmt.Errorf("invalid connection helper")
	}
	if s := text(v, "ttl"); s != "" {
		if _, _, e := ttlParts(s); e != nil {
			return e
		}
	}
	if text(v, "action") == "change-ttl" {
		if e := intRange(strings.TrimLeft(text(v, "new_ttl"), "+-"), 0, 255); e != nil {
			return fmt.Errorf("invalid new TTL")
		}
	}
	if s := text(v, "random"); s != "" {
		n, e := strconv.ParseFloat(strings.TrimSuffix(s, "%"), 64)
		if e != nil || n < 0 || n > 100 {
			return fmt.Errorf("random must be 0–100 percent")
		}
	}
	if s := text(v, "icmp_options"); s != "" {
		if p != "icmp" && p != "ipv6-icmp" {
			return fmt.Errorf("ICMP options require ICMP protocol")
		}
		_, s = plain(s)
		for _, n := range strings.Split(s, ":") {
			if e := intRange(n, 0, 255); e != nil {
				return fmt.Errorf("invalid ICMP type/code")
			}
		}
		if len(strings.Split(s, ":")) > 2 {
			return fmt.Errorf("invalid ICMP options")
		}
	}
	if s := text(v, "ipsec_policy"); s != "" {
		parts := strings.Split(strings.ReplaceAll(s, ":", ","), ",")
		if len(parts) != 2 || (parts[0] != "in" && parts[0] != "out") || (parts[1] != "ipsec" && parts[1] != "none") {
			return fmt.Errorf("IPsec policy must be in,ipsec / out,ipsec / in,none / out,none")
		}
	}
	if s := text(v, "limit"); s != "" {
		if _, _, e := rateParts(s); e != nil {
			return e
		}
	}
	if s := text(v, "time"); s != "" {
		parts := strings.Split(s, "-")
		if len(parts) != 2 {
			return fmt.Errorf("time expects start-stop in UTC")
		}
		for _, part := range parts {
			if _, e := clock(part); e != nil {
				return e
			}
		}
	}
	if s := text(v, "days"); s != "" {
		for _, day := range strings.Split(s, ",") {
			if weekdays[strings.ToLower(day)] == "" {
				return fmt.Errorf("invalid weekday %q", day)
			}
		}
	}
	if s := text(v, "nth"); s != "" {
		parts := strings.Split(s, ",")
		if len(parts) != 2 {
			return fmt.Errorf("nth expects every,packet (packet starts at 1)")
		}
		every, e := strconv.Atoi(parts[0])
		packet, e2 := strconv.Atoi(parts[1])
		if e != nil || e2 != nil || every < 1 || packet < 1 || packet > every {
			return fmt.Errorf("invalid nth values")
		}
	}
	if s := text(v, "connection_limit"); s != "" {
		parts := strings.Split(s, ",")
		if len(parts) != 2 {
			return fmt.Errorf("connection limit expects count,mask")
		}
		if e := intRange(parts[0], 1, 2147483647); e != nil {
			return e
		}
		max := 32
		if v["ip_version"] == float64(6) {
			max = 128
		}
		if e := intRange(parts[1], 0, max); e != nil {
			return e
		}
	}
	for _, key := range []string{"src_address_type", "dst_address_type"} {
		s := text(v, key)
		if s != "" {
			switch strings.ToUpper(s) {
			case "LOCAL", "UNICAST", "BROADCAST", "MULTICAST", "ANYCAST", "BLACKHOLE", "UNREACHABLE", "PROHIBIT":
			default:
				return fmt.Errorf("unsupported address type")
			}
		}
	}
	if s := text(v, "ip_fragment"); s != "" {
		if s != "yes" && s != "no" {
			return fmt.Errorf("fragment expects yes/no")
		}
		if v["ip_version"] == float64(6) {
			return fmt.Errorf("fragment matching is IPv4-only")
		}
	}
	return nil
}
func appendAdvanced(args []string, rule any) []string {
	v := values(rule)
	if s := text(v, "any_port"); s != "" {
		inv, s := plain(s)
		args = append(args, "-m multiport "+inv+"--ports "+portValue(s))
	}
	if s := text(v, "packet_mark"); s != "" {
		inv, s := plain(s)
		args = append(args, fmt.Sprintf("-m mark %s--mark %d", inv, MarkNameToID(s)))
	}
	if s := text(v, "connection_type"); s != "" {
		args = append(args, "-m helper --helper "+s)
	}
	if items, ok := v["connection_nat_state"].([]any); ok && len(items) > 0 {
		var states []string
		for _, i := range items {
			state := strings.ToUpper(i.(string))
			state = strings.ReplaceAll(state, "SRCNAT", "SNAT")
			state = strings.ReplaceAll(state, "DSTNAT", "DNAT")
			states = append(states, state)
		}
		args = append(args, "-m conntrack --ctstate "+strings.Join(states, ","))
	}
	if s := text(v, "content"); s != "" {
		args = append(args, "-m string --algo bm --string "+quote(s))
	}
	if s := text(v, "src_mac_address"); s != "" {
		inv, s := plain(s)
		args = append(args, "-m mac "+inv+"--mac-source "+s)
	}
	for _, direction := range []string{"in", "out"} {
		if s := text(v, direction+"_bridge_port"); s != "" {
			inv, s := plain(s)
			args = append(args, "-m physdev "+inv+"--physdev-"+direction+" "+s)
		}
	}
	if s := text(v, "ipsec_policy"); s != "" {
		p := strings.Split(strings.ReplaceAll(s, ":", ","), ",")
		args = append(args, "-m policy --dir "+p[0]+" --pol "+p[1])
	}
	if s := text(v, "dscp"); s != "" {
		args = append(args, "-m dscp --dscp "+s)
	}
	if s := text(v, "tcp_mss"); s != "" {
		r, _ := parseRange(s, 65535)
		args = append(args, "-m tcpmss --mss "+r)
	}
	if s := text(v, "tos"); s != "" {
		args = append(args, "-m tos --tos "+normalizeTOS(s))
	}
	if s := text(v, "packet_size"); s != "" {
		r, _ := parseRange(s, 65535)
		args = append(args, "-m length --length "+r)
	}
	if s := text(v, "random"); s != "" {
		n, _ := strconv.ParseFloat(strings.TrimSuffix(s, "%"), 64)
		args = append(args, fmt.Sprintf("-m statistic --mode random --probability %.8f", n/100))
	}
	if s := text(v, "tcp_flags"); s != "" {
		mask, on, _ := tcpFlags(s)
		args = append(args, "--tcp-flags "+mask+" "+on)
	}
	if s := text(v, "icmp_options"); s != "" {
		inv, s := plain(s)
		flag := "--icmp-type"
		if inferProtocol(v) == "ipv6-icmp" {
			flag = "--icmpv6-type"
		}
		args = append(args, inv+flag+" "+strings.ReplaceAll(s, ":", "/"))
	}
	if s := text(v, "ttl"); s != "" {
		op, n, _ := ttlParts(s)
		module := "ttl"
		if v["ip_version"] == float64(6) {
			module = "hl"
		}
		args = append(args, "-m "+module+" --"+module+"-"+op+" "+n)
	}
	if s := text(v, "limit"); s != "" {
		rate, burst, _ := rateParts(s)
		args = append(args, "-m limit --limit "+rate+" --limit-burst "+burst)
	}
	if text(v, "time") != "" || text(v, "days") != "" {
		args = append(args, "-m time")
		if s := text(v, "time"); s != "" {
			p := strings.Split(s, "-")
			start, _ := clock(p[0])
			stop, _ := clock(p[1])
			args = append(args, "--timestart "+start+" --timestop "+stop)
			if start > stop {
				args = append(args, "--contiguous")
			}
		}
		if s := text(v, "days"); s != "" {
			var days []string
			for _, d := range strings.Split(s, ",") {
				days = append(days, weekdays[strings.ToLower(d)])
			}
			args = append(args, "--weekdays "+strings.Join(days, ","))
		}
	}
	if s := text(v, "nth"); s != "" {
		p := strings.Split(s, ",")
		packet, _ := strconv.Atoi(p[1])
		args = append(args, fmt.Sprintf("-m statistic --mode nth --every %s --packet %d", p[0], packet-1))
	}
	if s := text(v, "connection_limit"); s != "" {
		p := strings.Split(s, ",")
		args = append(args, "-m connlimit --connlimit-above "+p[0]+" --connlimit-mask "+p[1])
	}
	for _, direction := range []string{"src", "dst"} {
		if s := text(v, direction+"_address_type"); s != "" {
			args = append(args, "-m addrtype --"+direction+"-type "+strings.ToUpper(s))
		}
	}
	if s := text(v, "ip_fragment"); s != "" {
		if s == "yes" {
			args = append(args, "-f")
		} else {
			args = append(args, "! -f")
		}
	}
	return args
}

func normalizeTOS(s string) string {
	switch s {
	case "min-delay":
		return "0x10/0x1e"
	case "max-throughput":
		return "0x08/0x1e"
	case "max-reliability":
		return "0x04/0x1e"
	case "min-cost":
		return "0x02/0x1e"
	}
	return s
}