package handlers

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os/exec"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/jackc/pgx/v5/pgxpool"

	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
)

// vipInfo enthält die für einen VIP-Schwenk notwendigen Daten.
type vipInfo struct {
	ID      int64  `json:"id"`
	Address string `json:"address"`
	Prefix  int    `json:"prefix"`
	Device  string `json:"device"`
}

// VIPStatusEntry kombiniert einen VIP mit den Nodes die ihn gerade halten.
type VIPStatusEntry struct {
	VIP      vipInfo  `json:"vip"`
	ActiveOn []string `json:"active_on"` // FQDNs der Nodes mit diesem VIP
}

// AgentActiveIPs gibt alle aktiven IPv4-Adressen dieses Nodes zurück.
// Wird vom Primary genutzt um zu prüfen welcher Node welchen VIP hält.
func (h *ClusterHandler) AgentActiveIPs(c *gin.Context) {
	ips, err := localActiveIPs()
	if err != nil {
		response.Internal(c, err)
		return
	}
	response.OK(c, gin.H{"ips": ips})
}

// vipCmdRequest ist der Body für den AgentVIPCmd-Endpoint.
type vipCmdRequest struct {
	Action  string `json:"action"`  // "add" | "del"
	Address string `json:"address"` // z.B. "10.0.5.1"
	Prefix  int    `json:"prefix"`  // z.B. 24
	Device  string `json:"device"`  // z.B. "vlan100"
}

// AgentVIPCmd führt `ip addr add/del` auf diesem Node aus.
// Wird vom Primary via mTLS für VIP-Schwenk-Tests aufgerufen.
func (h *ClusterHandler) AgentVIPCmd(c *gin.Context) {
	var req vipCmdRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	if req.Action != "add" && req.Action != "del" {
		response.BadRequest(c, simpleError("action must be 'add' or 'del'"))
		return
	}
	if req.Address == "" || req.Device == "" || req.Prefix <= 0 || req.Prefix > 128 {
		response.BadRequest(c, simpleError("address, device, prefix required"))
		return
	}
	if err := runVIPCmd(req.Action, req.Address, req.Prefix, req.Device); err != nil {
		slog.Warn("cluster: agent vip-cmd failed",
			"action", req.Action, "addr", req.Address, "dev", req.Device, "error", err)
		response.Internal(c, err)
		return
	}
	slog.Info("cluster: agent vip-cmd ok",
		"action", req.Action, "addr", req.Address, "prefix", req.Prefix,
		"dev", req.Device, "caller", c.ClientIP())
	response.OK(c, gin.H{"ok": true})
}

// VIPStatus liest alle VIPs (is_vip=true) aus der DB und fragt alle Nodes
// welche davon sie gerade aktiv haben. Nur sinnvoll im Cluster-Modus.
func (h *ClusterHandler) VIPStatus(c *gin.Context) {
	vips, err := loadVIPs(c.Request.Context(), h.Store.Pool)
	if err != nil {
		response.Internal(c, err)
		return
	}
	nodeIPs := h.collectActiveIPs(c.Request.Context())
	result := make([]VIPStatusEntry, 0, len(vips))
	for _, v := range vips {
		entry := VIPStatusEntry{VIP: v}
		for fqdn, ips := range nodeIPs {
			for _, ip := range ips {
				if ip == v.Address {
					entry.ActiveOn = append(entry.ActiveOn, fqdn)
					break
				}
			}
		}
		result = append(result, entry)
	}
	response.OK(c, gin.H{"vips": result})
}

// vipTestRequest steuert einen VIP-Schwenk.
type vipTestRequest struct {
	IPAddressID int64  `json:"ip_address_id"`
	Action      string `json:"action"` // "to_secondary" | "restore"
}

// vipTestStep beschreibt einen Schritt des Schwenk-Prozesses.
type vipTestStep struct {
	Step    string `json:"step"`
	OK      bool   `json:"ok"`
	Message string `json:"message,omitempty"`
}

// VIPTest schwenkt einen VIP vom Primary auf den Secondary ("to_secondary")
// oder zurück ("restore"). Nur vom Primary aufzurufen.
func (h *ClusterHandler) VIPTest(c *gin.Context) {
	var req vipTestRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	if req.Action != "to_secondary" && req.Action != "restore" {
		response.BadRequest(c, simpleError("action must be 'to_secondary' or 'restore'"))
		return
	}

	vips, err := loadVIPs(c.Request.Context(), h.Store.Pool)
	if err != nil {
		response.Internal(c, err)
		return
	}
	var target *vipInfo
	for i := range vips {
		if vips[i].ID == req.IPAddressID {
			target = &vips[i]
			break
		}
	}
	if target == nil {
		response.NotFound(c, simpleError("VIP not found or not marked as VIP"))
		return
	}

	all, err := h.Store.List(c.Request.Context())
	if err != nil {
		response.Internal(c, err)
		return
	}
	var peer *models.HANode
	for i := range all {
		if all[i].ID != h.LocalID {
			peer = &all[i]
			break
		}
	}
	if peer == nil {
		response.BadRequest(c, simpleError("kein Secondary-Peer gefunden"))
		return
	}

	var steps []vipTestStep
	addrPfx := fmt.Sprintf("%s/%d", target.Address, target.Prefix)

	if req.Action == "to_secondary" {
		// 1. VIP auf Secondary via mTLS hinzufügen
		steps = append(steps, h.peerVIPCmd(c.Request.Context(), *peer, target, "add",
			fmt.Sprintf("add %s dev %s auf %s", addrPfx, target.Device, peer.FQDN)))
		// 2. VIP vom Primary entfernen (nur wenn Secondary-Add erfolgreich)
		if steps[0].OK {
			steps = append(steps, localVIPStep(target, "del",
				fmt.Sprintf("del %s dev %s lokal", addrPfx, target.Device)))
		}
	} else {
		// 1. VIP auf Primary zurückholen
		steps = append(steps, localVIPStep(target, "add",
			fmt.Sprintf("add %s dev %s lokal", addrPfx, target.Device)))
		// 2. VIP auf Secondary entfernen
		steps = append(steps, h.peerVIPCmd(c.Request.Context(), *peer, target, "del",
			fmt.Sprintf("del %s dev %s auf %s", addrPfx, target.Device, peer.FQDN)))
	}

	slog.Info("cluster: vip-test", "action", req.Action, "vip", target.Address,
		"dev", target.Device, "peer", peer.FQDN, "actor", actorOf(c))
	response.OK(c, gin.H{"steps": steps})
}

// ── Hilfsfunktionen ───────────────────────────────────────────────────────

func loadVIPs(ctx context.Context, pool *pgxpool.Pool) ([]vipInfo, error) {
	rows, err := pool.Query(ctx, `
		SELECT ia.id, ia.address, ia.prefix, ni.name
		FROM ip_addresses ia
		JOIN network_interfaces ni ON ni.id = ia.interface_id
		WHERE ia.is_vip = true AND ia.active = true
		ORDER BY ni.name, ia.address`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []vipInfo
	for rows.Next() {
		var v vipInfo
		if err := rows.Scan(&v.ID, &v.Address, &v.Prefix, &v.Device); err != nil {
			return nil, err
		}
		out = append(out, v)
	}
	return out, rows.Err()
}

// collectActiveIPs fragt alle Cluster-Nodes (lokal + Peers via mTLS) nach
// ihren aktiven IPv4-Adressen und gibt eine Map[fqdn][]ip zurück.
func (h *ClusterHandler) collectActiveIPs(ctx context.Context) map[string][]string {
	result := make(map[string][]string)
	if h.Store == nil {
		return result
	}
	all, err := h.Store.List(ctx)
	if err != nil {
		return result
	}
	// Lokaler Node
	if ips, err := localActiveIPs(); err == nil {
		for _, n := range all {
			if n.ID == h.LocalID {
				result[n.FQDN] = ips
				break
			}
		}
	}
	// Peers via mTLS-Aggregator
	if h.Aggregator != nil {
		var peers []models.HANode
		for _, n := range all {
			if n.ID != h.LocalID {
				peers = append(peers, n)
			}
		}
		if len(peers) > 0 {
			peerResults := h.Aggregator.FanOut(ctx, peers, "/agent/cluster/active-ips", h.LocalID)
			for _, pr := range peerResults {
				if !pr.OK || len(pr.Data) == 0 {
					continue
				}
				var payload struct {
					IPs []string `json:"ips"`
				}
				if err := json.Unmarshal(pr.Data, &payload); err == nil {
					result[pr.FQDN] = payload.IPs
				}
			}
		}
	}
	return result
}

// localActiveIPs liest alle aktiven IPv4-Adressen des lokalen Nodes via `ip`.
func localActiveIPs() ([]string, error) {
	out, err := exec.Command("ip", "-4", "-o", "addr", "show").Output()
	if err != nil {
		return nil, err
	}
	var ips []string
	for _, line := range strings.Split(string(out), "\n") {
		parts := strings.Fields(line)
		for i, p := range parts {
			if p == "inet" && i+1 < len(parts) {
				addr := strings.SplitN(parts[i+1], "/", 2)[0]
				ips = append(ips, addr)
			}
		}
	}
	return ips, nil
}

// peerVIPCmd ruft AgentVIPCmd auf dem Peer via mTLS auf.
func (h *ClusterHandler) peerVIPCmd(ctx context.Context, peer models.HANode, vip *vipInfo, action, stepLabel string) vipTestStep {
	step := vipTestStep{Step: stepLabel}
	if h.Aggregator == nil {
		step.Message = "aggregator nicht verfügbar"
		return step
	}
	body, _ := json.Marshal(vipCmdRequest{
		Action:  action,
		Address: vip.Address,
		Prefix:  vip.Prefix,
		Device:  vip.Device,
	})
	res := h.Aggregator.PostPeerWithBody(ctx, peer, "/agent/cluster/vip-cmd", body)
	step.OK = res.OK
	if !res.OK {
		step.Message = res.Err
	}
	return step
}

// localVIPStep führt ip addr add/del auf dem lokalen Node aus.
func localVIPStep(vip *vipInfo, action, stepLabel string) vipTestStep {
	step := vipTestStep{Step: stepLabel}
	if err := runVIPCmd(action, vip.Address, vip.Prefix, vip.Device); err != nil {
		step.Message = err.Error()
		return step
	}
	step.OK = true
	return step
}

// runVIPCmd führt `sudo /usr/lib/edgeguard/vip-cmd.sh {action} {addr/prefix} {dev}` aus.
func runVIPCmd(action, address string, prefix int, device string) error {
	addrPfx := fmt.Sprintf("%s/%d", address, prefix)
	out, err := exec.Command("sudo", "-n", "/usr/lib/edgeguard/vip-cmd.sh", action, addrPfx, device).CombinedOutput()
	if err != nil {
		return fmt.Errorf("vip-cmd.sh %s %s %s: %s", action, addrPfx, device, strings.TrimSpace(string(out)))
	}
	return nil
}