package service

import (
	"encoding/json"
	"fmt"
	"strings"

	"github.com/mhsanaei/3x-ui/v3/internal/database"
	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
	"github.com/mhsanaei/3x-ui/v3/internal/util/common"

	"gorm.io/gorm"
)

type transportBits uint8

const (
	transportTCP transportBits = 1 << iota
	transportUDP
)

func inboundTransports(protocol model.Protocol, streamSettings, settings string) transportBits {
	// protocols that ignore streamSettings entirely.
	switch protocol {
	case model.Hysteria, model.WireGuard:
		return transportUDP
	case model.MTProto:
		return transportTCP
	}

	var bits transportBits

	// peek at streamSettings.network to spot udp-based transports.
	// parse errors are non-fatal: missing or weird streamSettings just
	// keeps the default tcp bit below.
	network := ""
	if streamSettings != "" {
		var ss map[string]any
		if json.Unmarshal([]byte(streamSettings), &ss) == nil {
			if n, _ := ss["network"].(string); n != "" {
				network = n
			}
		}
	}
	switch network {
	case "kcp", "quic":
		bits |= transportUDP
	default:
		bits |= transportTCP
	}

	// a few protocols carry their L4 choice in settings instead of (or in
	// addition to) streamSettings: SS / Tunnel via a CSV field that wins
	// outright, Mixed via an additive udp boolean.
	if settings != "" {
		var st map[string]any
		if json.Unmarshal([]byte(settings), &st) == nil {
			switch protocol {
			case model.Shadowsocks, model.Tunnel:
				key := "network"
				if protocol == model.Tunnel {
					key = "allowedNetwork"
				}
				if n, ok := st[key].(string); ok && n != "" {
					bits = 0
					for part := range strings.SplitSeq(n, ",") {
						switch strings.TrimSpace(part) {
						case "tcp":
							bits |= transportTCP
						case "udp":
							bits |= transportUDP
						}
					}
				}
			case model.Mixed:
				// socks/http "mixed" inbound: settings.udp=true means it
				// also relays udp on the same port (socks5 udp associate).
				if udpOn, _ := st["udp"].(bool); udpOn {
					bits |= transportUDP
				}
			}
		}
	}

	// safety net: never return zero, even if every parse failed.
	if bits == 0 {
		bits = transportTCP
	}
	return bits
}

func listenOverlaps(a, b string) bool {
	if isAnyListen(a) || isAnyListen(b) {
		return true
	}
	return a == b
}

func isAnyListen(s string) bool {
	return s == "" || s == "0.0.0.0" || s == "::" || s == "::0"
}

type portConflictDetail struct {
	InboundID  int
	Remark     string
	Tag        string
	Listen     string
	Port       int
	Transports transportBits
}

// String renders the detail as a single-line, user-facing summary.
func (d *portConflictDetail) String() string {
	name := d.Remark
	if name == "" {
		name = d.Tag
	}
	if name == "" {
		name = fmt.Sprintf("#%d", d.InboundID)
	} else if d.InboundID > 0 {
		name = fmt.Sprintf("'%s' (#%d)", name, d.InboundID)
	} else {
		// reserved/system inbounds (e.g. the Xray API) have no DB id.
		name = fmt.Sprintf("'%s'", name)
	}
	listen := d.Listen
	if isAnyListen(listen) {
		listen = "*"
	}
	return fmt.Sprintf("port %d (%s) already used by inbound %s on %s",
		d.Port, transportTagSuffix(d.Transports), name, listen)
}

// defaultXrayAPIPort is the loopback port of the internal Xray API inbound
// (tag "api") seeded into the config template. Used as a fallback when the
// template can't be parsed.
const defaultXrayAPIPort = 62789

// reservedAPIPort returns the port of the internal Xray API inbound declared
// in the config template, falling back to defaultXrayAPIPort.
func reservedAPIPort() int {
	tmpl, err := (&SettingService{}).GetXrayConfigTemplate()
	if err != nil || tmpl == "" {
		return defaultXrayAPIPort
	}
	var parsed struct {
		Inbounds []struct {
			Port int    `json:"port"`
			Tag  string `json:"tag"`
		} `json:"inbounds"`
	}
	if json.Unmarshal([]byte(tmpl), &parsed) != nil {
		return defaultXrayAPIPort
	}
	for _, in := range parsed.Inbounds {
		if in.Tag == "api" && in.Port > 0 {
			return in.Port
		}
	}
	return defaultXrayAPIPort
}

// checkPortConflict reads outside any transaction; callers that must not race a
// concurrent create use checkPortConflictTx inside their own transaction.
func (s *InboundService) checkPortConflict(inbound *model.Inbound, ignoreId int) (*portConflictDetail, error) {
	return checkPortConflictTx(database.GetDB(), inbound, ignoreId)
}

func checkPortConflictTx(db *gorm.DB, inbound *model.Inbound, ignoreId int) (*portConflictDetail, error) {
	newBits := inboundTransports(inbound.Protocol, inbound.StreamSettings, inbound.Settings)

	// The internal Xray API inbound (tag "api", loopback TCP) isn't a DB row,
	// so a local user inbound reusing its port would leave Xray binding the
	// port twice (#5304). Nodes run their own Xray, so this only applies to
	// the local panel.
	if inbound.NodeID == nil && inbound.Port == reservedAPIPort() &&
		newBits&transportTCP != 0 && listenOverlaps("127.0.0.1", inbound.Listen) {
		return &portConflictDetail{
			Tag:        "api",
			Listen:     "127.0.0.1",
			Port:       inbound.Port,
			Transports: transportTCP,
		}, nil
	}

	var candidates []*model.Inbound
	q := db.Model(model.Inbound{}).Where("port = ?", inbound.Port)
	if ignoreId > 0 {
		q = q.Where("id != ?", ignoreId)
	}
	if err := q.Find(&candidates).Error; err != nil {
		return nil, err
	}

	for _, c := range candidates {
		if !sameNode(c.NodeID, inbound.NodeID) {
			continue
		}
		if !listenOverlaps(c.Listen, inbound.Listen) {
			continue
		}
		existingBits := inboundTransports(c.Protocol, c.StreamSettings, c.Settings)
		shared := existingBits & newBits
		if shared == 0 {
			continue
		}
		return &portConflictDetail{
			InboundID:  c.Id,
			Remark:     c.Remark,
			Tag:        c.Tag,
			Listen:     c.Listen,
			Port:       c.Port,
			Transports: shared,
		}, nil
	}
	return nil, nil
}

func sameNode(a, b *int) bool {
	if a == nil && b == nil {
		return true
	}
	if a == nil || b == nil {
		return false
	}
	return *a == *b
}

func baseInboundTag(port int) string {
	return fmt.Sprintf("in-%v", port)
}

func transportTagSuffix(b transportBits) string {
	switch b {
	case transportTCP:
		return "tcp"
	case transportUDP:
		return "udp"
	case transportTCP | transportUDP:
		return "tcpudp"
	}
	return "any"
}

// nodeTagPrefix scopes a tag to one remote node so the same listen+port
// can live on the central panel and on a node without bumping the global
// UNIQUE(inbounds.tag) constraint. nil → "" (local panel).
func nodeTagPrefix(nodeID *int) string {
	if nodeID == nil {
		return ""
	}
	return fmt.Sprintf("n%d-", *nodeID)
}

func composeInboundTag(port int, nodeID *int, bits transportBits) string {
	return nodeTagPrefix(nodeID) + baseInboundTag(port) + "-" + transportTagSuffix(bits)
}

func isAutoGeneratedTag(tag string, port int, nodeID *int, bits transportBits) bool {
	base := composeInboundTag(port, nodeID, bits)
	if tag == base {
		return true
	}
	suffix, ok := strings.CutPrefix(tag, base+"-")
	if !ok || suffix == "" {
		return false
	}
	for _, r := range suffix {
		if r < '0' || r > '9' {
			return false
		}
	}
	return true
}

func (s *InboundService) generateInboundTag(inbound *model.Inbound, ignoreId int) (string, error) {
	bits := inboundTransports(inbound.Protocol, inbound.StreamSettings, inbound.Settings)
	candidate := composeInboundTag(inbound.Port, inbound.NodeID, bits)
	exists, err := s.tagExists(candidate, ignoreId)
	if err != nil {
		return "", err
	}
	if !exists {
		return candidate, nil
	}

	for i := 2; i < 100; i++ {
		c := fmt.Sprintf("%s-%d", candidate, i)
		exists, err = s.tagExists(c, ignoreId)
		if err != nil {
			return "", err
		}
		if !exists {
			return c, nil
		}
	}
	return "", common.NewError("could not pick a unique inbound tag for port:", inbound.Port)
}

func (s *InboundService) resolveInboundTag(inbound *model.Inbound, ignoreId int) (string, error) {
	if inbound.Tag != "" {
		taken, err := s.tagExists(inbound.Tag, ignoreId)
		if err != nil {
			return "", err
		}
		if !taken {
			return inbound.Tag, nil
		}
	}
	return s.generateInboundTag(inbound, ignoreId)
}

func (s *InboundService) tagExists(tag string, ignoreId int) (bool, error) {
	db := database.GetDB()
	q := db.Model(model.Inbound{}).Where("tag = ?", tag)
	if ignoreId > 0 {
		q = q.Where("id != ?", ignoreId)
	}
	var count int64
	if err := q.Count(&count).Error; err != nil {
		return false, err
	}
	return count > 0, nil
}
