package v1

import (
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/wild-cloud/wild-central/internal/certbot"
	"github.com/wild-cloud/wild-central/internal/config"
	"github.com/wild-cloud/wild-central/internal/haproxy"
	"github.com/wild-cloud/wild-central/internal/network"
	"github.com/wild-cloud/wild-central/internal/services"
	"github.com/wild-cloud/wild-central/internal/sse"
)

// EnsureCentralService registers (or updates) Central's own domain as a service
// so it participates in DNS, HAProxy routing, and TLS cert tracking like any
// other service. Called on startup and when global config changes.
func (api *API) EnsureCentralService() {
	centralDomain := api.getCentralDomain()
	port := api.getRunningPort()
	backend := fmt.Sprintf("127.0.0.1:%d", port)

	// Check if the current registration already matches — skip if so.
	if centralDomain != "" {
		if existing, _ := api.services.Get(centralDomain); existing != nil &&
			existing.Source == "central" &&
			existing.Backend.Address == backend {
			return
		}
	}

	// Clean up stale Central registrations (e.g. domain changed).
	svcs, _ := api.services.List()
	for _, svc := range svcs {
		if svc.Source == "central" && svc.Domain != centralDomain {
			_ = api.services.Deregister(svc.Domain)
		}
	}

	if centralDomain == "" {
		return
	}

	_ = api.services.Register(services.Service{
		Domain: centralDomain,
		Source: "central",
		Backend: services.Backend{
			Address: backend,
			Type:    services.BackendHTTP,
		},
		Reach: services.ReachInternal,
		TLS:   services.TLSTerminate,
	})
}

// Reconcile runs networking reconciliation immediately. Called on startup
// and automatically whenever a service is registered/updated/deregistered.
func (api *API) Reconcile() {
	api.reconcileNetworking()
}

// reconcileNetworking reads all registered services and regenerates
// dnsmasq DNS entries and HAProxy routes to match.
func (api *API) reconcileNetworking() {
	svcs, err := api.services.List()
	if err != nil {
		slog.Error("reconcile: failed to list services", "error", err)
		return
	}

	globalConfigPath := filepath.Join(api.dataDir, "config.yaml")
	globalCfg, err := config.LoadGlobalConfig(globalConfigPath)
	if err != nil {
		slog.Warn("reconcile: failed to load global config, using empty", "error", err)
		globalCfg = &config.GlobalConfig{}
	}

	// Build HAProxy routes from registered services
	var instanceRoutes []haproxy.InstanceRoute
	var httpRoutes []haproxy.HTTPRoute

	for _, svc := range svcs {
		switch svc.Backend.Type {
		case services.BackendTCPPassthrough:
			instanceRoutes = append(instanceRoutes, haproxy.InstanceRoute{
				Name:       svc.Domain,
				Domain:     svc.Domain,
				BackendIP:  extractHost(svc.Backend.Address),
				Subdomains: svc.Subdomains,
			})
		case services.BackendHTTP:
			httpRoutes = append(httpRoutes, haproxy.HTTPRoute{
				Name:       svc.Domain,
				Domain:     svc.Domain,
				Backend:    svc.Backend.Address,
				HealthPath: svc.Backend.Health,
			})
		}
	}

	// Only include L7 HTTP routes for services that have a cert.
	certsDir := "/etc/haproxy/certs/"
	var activeHTTPRoutes []haproxy.HTTPRoute
	for _, route := range httpRoutes {
		if hasCertForDomain(certsDir, route.Domain) {
			activeHTTPRoutes = append(activeHTTPRoutes, route)
		} else {
			slog.Warn("reconcile: skipping L7 route (no cert)", "domain", route.Domain)
		}
	}

	// Generate and write HAProxy config
	haproxyCfg := api.haproxy.GenerateWithOpts(instanceRoutes, nil, haproxy.GenerateOpts{
		HTTPRoutes: activeHTTPRoutes,
		CertsDir:   certsDir,
	})

	if err := api.haproxy.WriteConfig(haproxyCfg); err != nil {
		slog.Error("reconcile: failed to write HAProxy config", "error", err)
	} else {
		if err := api.haproxy.ReloadService(); err != nil {
			slog.Warn("reconcile: failed to reload HAProxy", "error", err)
		} else {
			api.broadcastHaproxyEvent("haproxy:config", "HAProxy config regenerated from registered services")
		}
	}

	// Generate dnsmasq DNS entries from registered services.
	// DNS target IP depends on service type:
	//   tcp-passthrough (k8s): DNS → k8s LB IP (LAN traffic goes direct to k8s)
	//   http/static: DNS → Central IP (HAProxy terminates TLS)
	// Use the configured dnsmasq IP (eth0) as Central's IP, not auto-detected
	// (auto-detect can pick wlan0 if that's the default route).
	centralIP := globalCfg.Cloud.Dnsmasq.IP
	if centralIP == "" {
		centralIP, _ = network.GetWildCentralIP()
	}
	if centralIP == "" {
		centralIP = "127.0.0.1"
	}

	var instanceConfigs []config.InstanceConfig
	for _, svc := range svcs {
		if svc.Domain == "" {
			continue
		}

		// Choose the DNS target IP based on service type
		dnsIP := centralIP
		if svc.Backend.Type == services.BackendTCPPassthrough {
			// k8s instances: LAN clients connect directly to the k8s LB
			dnsIP = extractHost(svc.Backend.Address)
		}

		ic := config.InstanceConfig{}
		ic.Cluster.LoadBalancerIp = dnsIP

		if svc.Reach == services.ReachInternal {
			// Internal-only: local=/ prevents upstream DNS forwarding
			ic.Cloud.InternalDomain = svc.Domain
		} else {
			ic.Cloud.Domain = svc.Domain
		}

		instanceConfigs = append(instanceConfigs, ic)
	}

	if err := api.dnsmasq.UpdateConfig(globalCfg, instanceConfigs, true); err != nil {
		slog.Error("reconcile: failed to update dnsmasq", "error", err)
	} else {
		api.broadcastDnsmasqEvent("dnsmasq:config", "DNS config regenerated from registered services")
	}

	// Ensure TLS certs exist for HTTP services (where Central terminates TLS).
	// For services under the gateway domain, a wildcard cert covers them all.
	// For others, provision individual certs.
	if len(httpRoutes) > 0 {
		api.ensureTLSCerts(globalCfg, svcs)
	}

	slog.Info("reconcile: networking updated",
		"services", len(svcs),
		"l4Routes", len(instanceRoutes),
		"l7Routes", len(httpRoutes),
	)
}

// ensureTLSCerts logs which certificates are missing for registered services.
// Does NOT auto-provision — cert provisioning is user-initiated via the
// Certificates page. This just logs warnings so the operator knows what's needed.
func (api *API) ensureTLSCerts(globalCfg *config.GlobalConfig, svcs []services.Service) {
	gatewayDomain := ""
	if parts := strings.SplitN(globalCfg.Cloud.Central.Domain, ".", 2); len(parts) == 2 {
		gatewayDomain = parts[1]
	}

	for _, svc := range svcs {
		if svc.TLS != services.TLSTerminate || svc.Domain == "" {
			continue
		}

		// Check if covered by wildcard
		if gatewayDomain != "" && strings.HasSuffix(svc.Domain, "."+gatewayDomain) {
			wildcardCert := certbot.HAProxyCertPath(gatewayDomain)
			if _, err := os.Stat(wildcardCert); err != nil {
				slog.Warn("reconcile/tls: no wildcard cert for gateway domain — provision via Certificates page",
					"domain", svc.Domain, "needed", "*."+gatewayDomain)
			}
			continue
		}

		// Check individual cert
		if _, err := os.Stat(certbot.HAProxyCertPath(svc.Domain)); err != nil {
			slog.Warn("reconcile/tls: no cert for service — provision via Certificates page",
				"domain", svc.Domain)
		}
	}
}

// hasCertForDomain checks if a cert exists for a domain — either an individual
// cert (<domain>.pem) or a wildcard cert that covers it.
func hasCertForDomain(certsDir, domain string) bool {
	// Check individual cert
	if _, err := os.Stat(certbot.HAProxyCertPath(domain)); err == nil {
		return true
	}
	// Check wildcard certs — a *.example.com cert covers foo.example.com
	parts := strings.SplitN(domain, ".", 2)
	if len(parts) == 2 {
		// Wildcard cert might be stored as the base domain PEM
		wildcardBase := parts[1]
		if _, err := os.Stat(certbot.HAProxyCertPath(wildcardBase)); err == nil {
			return true
		}
	}
	// Check if the certs directory has ANY .pem files (HAProxy needs at least one)
	entries, err := os.ReadDir(certsDir)
	if err != nil {
		return false
	}
	for _, e := range entries {
		if strings.HasSuffix(e.Name(), ".pem") {
			// There's at least one cert — HAProxy can start with the dir bind.
			// The specific domain may not have its own cert but HAProxy won't crash.
			// It will serve whichever cert matches best (or the first one as default).
			return true
		}
	}
	return false
}

// extractHost gets the host part from a host:port string
func extractHost(addr string) string {
	for i := len(addr) - 1; i >= 0; i-- {
		if addr[i] == ':' {
			return addr[:i]
		}
	}
	return addr
}

// broadcastDnsmasqEvent broadcasts SSE events for dnsmasq status changes
func (api *API) broadcastDnsmasqEvent(eventType string, message string) {
	if api.sseManager == nil {
		return
	}

	// Get current dnsmasq status
	status, err := api.dnsmasq.GetStatus()
	if err != nil {
		status = nil
	}

	event := &sse.Event{
		ID:           fmt.Sprintf("dnsmasq-%d", time.Now().UnixNano()),
		Type:         eventType,
		InstanceName: "global", // dnsmasq is global/central-level, not instance-specific
		Timestamp:    time.Now(),
		Data: map[string]any{
			"message": message,
			"status":  status,
		},
	}

	api.sseManager.Broadcast(event)
}

// broadcastHaproxyEvent broadcasts SSE events for HAProxy status changes
func (api *API) broadcastHaproxyEvent(eventType string, message string) {
	if api.sseManager == nil {
		return
	}

	event := &sse.Event{
		ID:           fmt.Sprintf("haproxy-%d", time.Now().UnixNano()),
		Type:         eventType,
		InstanceName: "global",
		Timestamp:    time.Now(),
		Data: map[string]any{
			"message": message,
		},
	}

	api.sseManager.Broadcast(event)
}

// broadcastCentralStatusEvent broadcasts SSE events for central status changes
func (api *API) broadcastCentralStatusEvent(startTime time.Time) {
	if api.sseManager == nil {
		return
	}

	uptime := time.Since(startTime)

	event := &sse.Event{
		ID:           fmt.Sprintf("central-%d", time.Now().UnixNano()),
		Type:         "central:status",
		InstanceName: "global",
		Timestamp:    time.Now(),
		Data: map[string]any{
			"status":        "running",
			"version":       api.version,
			"uptime":        uptime.String(),
			"uptimeSeconds": int(uptime.Seconds()),
		},
	}

	api.sseManager.Broadcast(event)
}