package service

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

	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
	"github.com/mhsanaei/3x-ui/v3/internal/logger"
	"github.com/mhsanaei/3x-ui/v3/internal/xray"
)

// ForwardingSpec is the stored shape of an inbound's 「转发」 (forwarding)
// form (amo-style, per-inbound granularity). The form is what the panel
// persists on the inbound row; the compiled egress (a socks/http outbound
// plus an inboundTag routing rule on the entry agent) is derived from it
// every time the agent's config is generated — never snapshotted — so
// template edits keep applying to forwarding agents and the spec survives
// inbound re-homing untouched.
type ForwardingSpec struct {
	// Mode: "" or "direct" = no forwarding; "forward" = enabled.
	Mode string `json:"mode"`
	// Landing: "managed" (an existing mixed inbound in this panel) or
	// "manual" (a free-form endpoint).
	Landing string `json:"landing"`
	// Managed only: the landing inbound's id. Address/port/credentials are
	// resolved from that row at config-build time, never copied here.
	TargetInboundId int `json:"targetInboundId"`
	// Manual only: landing endpoint as dialed by the entry agent.
	Address  string `json:"address"`
	Port     int    `json:"port"`
	Protocol string `json:"protocol"` // "socks5" | "http" (entry → exit transport)
	Username string `json:"username"`
	Password string `json:"password"`
}

// Enabled reports whether the spec turns forwarding on.
func (f *ForwardingSpec) Enabled() bool {
	return f != nil && f.Mode == "forward"
}

// ParseForwardingSpec decodes the stored form. Empty input is a nil spec
// (direct), not an error.
func ParseForwardingSpec(raw string) (*ForwardingSpec, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return nil, nil
	}
	var spec ForwardingSpec
	if err := json.Unmarshal([]byte(raw), &spec); err != nil {
		return nil, fmt.Errorf("invalid forwarding settings: %w", err)
	}
	return &spec, nil
}

// validateForwardingSpec is the field-level save gate (no DB access).
func validateForwardingSpec(spec *ForwardingSpec, selfID int) error {
	if !spec.Enabled() {
		return nil
	}
	switch spec.Landing {
	case "managed":
		if spec.TargetInboundId <= 0 {
			return fmt.Errorf("forwarding: a managed landing requires choosing a target inbound")
		}
		if selfID > 0 && spec.TargetInboundId == selfID {
			return fmt.Errorf("forwarding: an inbound cannot forward to itself")
		}
	case "manual":
		if strings.TrimSpace(spec.Address) == "" {
			return fmt.Errorf("forwarding: landing address is required")
		}
		if spec.Port < 1 || spec.Port > 65535 {
			return fmt.Errorf("forwarding: landing port %d out of range", spec.Port)
		}
		if spec.Protocol != "socks5" && spec.Protocol != "http" {
			return fmt.Errorf("forwarding: unsupported entry-to-exit protocol %q", spec.Protocol)
		}
	default:
		return fmt.Errorf("forwarding: unknown landing type %q", spec.Landing)
	}
	return nil
}

// validateForwarding is the save-time gate for AddInbound/UpdateInbound:
// parse + field checks + (for managed landings) target existence and type.
func (s *InboundService) validateForwarding(inbound *model.Inbound) error {
	spec, err := ParseForwardingSpec(inbound.Forwarding)
	if err != nil {
		return err
	}
	if err := validateForwardingSpec(spec, inbound.Id); err != nil {
		return err
	}
	if spec.Enabled() && spec.Landing == "managed" {
		target, err := s.GetInbound(spec.TargetInboundId)
		if err != nil {
			return fmt.Errorf("forwarding: target inbound %d not found", spec.TargetInboundId)
		}
		if !isForwardingLandingProtocol(target.Protocol) {
			return fmt.Errorf("forwarding: target inbound %d (%s) is not a SOCKS landing", target.Id, target.Protocol)
		}
	}
	return nil
}

// isForwardingLandingProtocol reports whether an inbound can serve as a
// managed landing: the fork's SOCKS-family inbound is "mixed" (SOCKS+HTTP
// combined); a bare "socks" row can only arrive via sync from an upstream
// panel, and speaks the same wire protocol.
func isForwardingLandingProtocol(p model.Protocol) bool {
	return p == model.Mixed || p == model.Protocol("socks")
}

// resolvedLanding is a forwarding spec compiled to a concrete endpoint.
type resolvedLanding struct {
	address  string
	port     int
	protocol string // xray outbound protocol: "socks" | "http"
	username string
	password string
}

// resolveForwardingLanding turns a spec into a concrete endpoint. Managed
// landings read the target row live: a concrete listen IP wins (the user's
// internal-network landings are recorded exactly that way), otherwise the
// hosting node's address; credentials come from the target's first account.
func (s *XrayService) resolveForwardingLanding(spec *ForwardingSpec) (*resolvedLanding, error) {
	if spec.Landing == "manual" {
		protocol := "socks"
		if spec.Protocol == "http" {
			protocol = "http"
		}
		return &resolvedLanding{
			address:  strings.TrimSpace(spec.Address),
			port:     spec.Port,
			protocol: protocol,
			username: spec.Username,
			password: spec.Password,
		}, nil
	}
	target, err := s.inboundService.GetInbound(spec.TargetInboundId)
	if err != nil {
		return nil, fmt.Errorf("target inbound %d: %w", spec.TargetInboundId, err)
	}
	if !isForwardingLandingProtocol(target.Protocol) {
		return nil, fmt.Errorf("target inbound %d is %s, not a SOCKS landing", target.Id, target.Protocol)
	}
	address := strings.TrimSpace(target.Listen)
	if address == "" || address == "0.0.0.0" || address == "::" {
		address = ""
		if target.NodeID != nil {
			if node, nerr := s.nodeService.GetById(*target.NodeID); nerr == nil && node != nil {
				address = strings.TrimSpace(node.Address)
			}
		}
		if address == "" {
			return nil, fmt.Errorf("target inbound %d has no resolvable landing address", target.Id)
		}
	}
	user, pass := socksAccountOf(target.Settings)
	return &resolvedLanding{
		address:  address,
		port:     target.Port,
		protocol: "socks",
		username: user,
		password: pass,
	}, nil
}

// socksAccountOf extracts the first account from a mixed/socks inbound's
// settings. noauth (or account-less) settings yield empty credentials.
func socksAccountOf(settings string) (string, string) {
	var st struct {
		Auth     string `json:"auth"`
		Accounts []struct {
			User string `json:"user"`
			Pass string `json:"pass"`
		} `json:"accounts"`
	}
	if err := json.Unmarshal([]byte(settings), &st); err != nil {
		return "", ""
	}
	if st.Auth == "noauth" || len(st.Accounts) == 0 {
		return "", ""
	}
	return st.Accounts[0].User, st.Accounts[0].Pass
}

// applyInboundForwarding compiles the forwarding specs of the inbounds homed
// on one agent into extra outbounds and inboundTag routing rules on cfg. It
// runs after applyAgentEgress, so entries ride on top of whichever egress
// base is in effect (live template or the stored per-agent override) and
// template edits keep flowing to forwarding agents. Unresolvable entries
// are skipped with a warning — a stale landing must never take down the
// whole agent config.
func (s *XrayService) applyInboundForwarding(cfg *xray.Config, inbounds []*model.Inbound) {
	var outbounds []any
	var rules []any
	for _, inbound := range inbounds {
		spec, err := ParseForwardingSpec(inbound.Forwarding)
		if err != nil {
			logger.Warningf("Inbound %s: %v (forwarding ignored)", inbound.Tag, err)
			continue
		}
		if !spec.Enabled() {
			continue
		}
		if spec.Landing == "managed" && spec.TargetInboundId == inbound.Id {
			logger.Warningf("Inbound %s: forwarding target is itself, ignored", inbound.Tag)
			continue
		}
		landing, err := s.resolveForwardingLanding(spec)
		if err != nil {
			logger.Warningf("Inbound %s: forwarding skipped: %v", inbound.Tag, err)
			continue
		}
		tag := fmt.Sprintf("fwd-%d", inbound.Id)
		server := map[string]any{
			"address": landing.address,
			"port":    landing.port,
		}
		if landing.username != "" {
			server["users"] = []any{map[string]any{
				"user": landing.username,
				"pass": landing.password,
			}}
		}
		outbounds = append(outbounds, map[string]any{
			"tag":      tag,
			"protocol": landing.protocol,
			"settings": map[string]any{"servers": []any{server}},
		})
		rules = append(rules, map[string]any{
			"type":        "field",
			"inboundTag":  []any{inbound.Tag},
			"outboundTag": tag,
		})
	}
	if len(outbounds) == 0 {
		return
	}

	var existing []any
	if len(cfg.OutboundConfigs) > 0 {
		_ = json.Unmarshal(cfg.OutboundConfigs, &existing)
	}
	present := make(map[string]bool, len(existing))
	for _, o := range existing {
		if m, ok := o.(map[string]any); ok {
			if t, ok := m["tag"].(string); ok {
				present[t] = true
			}
		}
	}
	for _, o := range outbounds {
		if tag := o.(map[string]any)["tag"].(string); !present[tag] {
			existing = append(existing, o)
		}
	}
	if raw, err := json.Marshal(existing); err == nil {
		cfg.OutboundConfigs = raw
	}

	routing := map[string]any{}
	if len(cfg.RouterConfig) > 0 {
		_ = json.Unmarshal(cfg.RouterConfig, &routing)
	}
	oldRules, _ := routing["rules"].([]any)
	routing["rules"] = append(rules, oldRules...)
	if raw, err := json.Marshal(routing); err == nil {
		cfg.RouterConfig = raw
	}
}