// Package tunnel manages Cloudflare Tunnel (cloudflared) configuration.
//
// Services with reach=public are projected onto the internet at
// <subdomain>.<publicDomain>. The tunnel bridges each public hostname
// to Central's gateway via Host/SNI rewriting, so the gateway's wildcard
// cert validates and existing routing works unchanged.
//
// The config is locally-managed (a config.yml with an explicit ingress
// list), not a remotely-managed token tunnel — the public surface is
// exactly the set of registered public services.
package tunnel

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

	"gopkg.in/yaml.v3"

	"github.com/wild-cloud/wild-central/internal/storage"
)

// Config holds tunnel configuration.
type Config struct {
	Enabled        bool   `yaml:"enabled" json:"enabled"`
	TunnelID       string `yaml:"tunnelId" json:"tunnelId"`
	PublicDomain   string `yaml:"publicDomain" json:"publicDomain"`   // e.g. "pub.payne.io"
	GatewayDomain  string `yaml:"gatewayDomain" json:"gatewayDomain"` // e.g. "payne.io" (internal)
	CredentialsDir string `yaml:"credentialsDir" json:"credentialsDir"`
}

// PublicDomain describes a domain that should be exposed through the tunnel.
type PublicDomain struct {
	Name      string // domain name (used as subdomain)
	Subdomain string // explicit subdomain override (defaults to Name)
}

// Manager handles cloudflared tunnel configuration.
type Manager struct {
	dataDir string
}

// NewManager creates a new tunnel manager.
func NewManager(dataDir string) *Manager {
	return &Manager{dataDir: dataDir}
}

// configPath returns the path to the generated cloudflared config.
func (m *Manager) configPath() string {
	return filepath.Join(m.dataDir, "tunnel", "config.yml")
}

// credentialsPath returns the path to the tunnel credentials JSON.
func credentialsPath(credentialsDir, tunnelID string) string {
	if credentialsDir == "" {
		credentialsDir = filepath.Join(os.Getenv("HOME"), ".cloudflared")
	}
	return filepath.Join(credentialsDir, tunnelID+".json")
}

// ingressEntry is a single cloudflared ingress rule.
type ingressEntry struct {
	Hostname      string               `yaml:"hostname,omitempty"`
	Service       string               `yaml:"service"`
	OriginRequest *originRequestConfig `yaml:"originRequest,omitempty"`
}

type originRequestConfig struct {
	OriginServerName string `yaml:"originServerName,omitempty"`
	HTTPHostHeader   string `yaml:"httpHostHeader,omitempty"`
}

type cloudflaredConfig struct {
	Tunnel          string         `yaml:"tunnel"`
	CredentialsFile string         `yaml:"credentials-file"`
	Ingress         []ingressEntry `yaml:"ingress"`
}

// GenerateConfig renders the cloudflared config.yml for the given public services.
// Returns the YAML string, or empty string if tunnel is not configured or no services are public.
func (m *Manager) GenerateConfig(cfg Config, services []PublicDomain) string {
	if !cfg.Enabled || cfg.TunnelID == "" || cfg.PublicDomain == "" || cfg.GatewayDomain == "" {
		return ""
	}
	if len(services) == 0 {
		return ""
	}

	// The gateway origin — HAProxy terminates TLS on 443, so we connect there.
	gatewayOrigin := "https://localhost:443"

	var ingress []ingressEntry
	for _, svc := range services {
		subdomain := svc.Subdomain
		if subdomain == "" {
			subdomain = svc.Name
		}

		publicHost := subdomain + "." + cfg.PublicDomain
		internalHost := subdomain + "." + cfg.GatewayDomain

		ingress = append(ingress, ingressEntry{
			Hostname: publicHost,
			Service:  gatewayOrigin,
			OriginRequest: &originRequestConfig{
				OriginServerName: internalHost,
				HTTPHostHeader:   internalHost,
			},
		})
	}

	// Cloudflared requires a terminal catch-all
	ingress = append(ingress, ingressEntry{
		Service: "http_status:404",
	})

	config := cloudflaredConfig{
		Tunnel:          cfg.TunnelID,
		CredentialsFile: credentialsPath(cfg.CredentialsDir, cfg.TunnelID),
		Ingress:         ingress,
	}

	data, err := yaml.Marshal(config)
	if err != nil {
		slog.Error("failed to marshal tunnel config", "error", err)
		return ""
	}

	return string(data)
}

// ValidateConfig checks tunnel config for common errors before generating.
func ValidateConfig(cfg Config) error {
	if !cfg.Enabled {
		return nil // disabled is valid
	}
	if cfg.TunnelID == "" {
		return fmt.Errorf("tunnel ID is required")
	}
	if cfg.PublicDomain == "" {
		return fmt.Errorf("public domain is required")
	}
	if cfg.GatewayDomain == "" {
		return fmt.Errorf("gateway domain is required")
	}
	credsFile := credentialsPath(cfg.CredentialsDir, cfg.TunnelID)
	if _, err := os.Stat(credsFile); err != nil {
		return fmt.Errorf("credentials file not found: %s", credsFile)
	}
	return nil
}

// WriteConfig validates, generates, and writes the cloudflared config to disk.
func (m *Manager) WriteConfig(cfg Config, services []PublicDomain) error {
	if err := ValidateConfig(cfg); err != nil {
		return fmt.Errorf("config validation: %w", err)
	}
	content := m.GenerateConfig(cfg, services)
	if content == "" {
		// Remove config if tunnel is disabled or no public services
		path := m.configPath()
		if _, err := os.Stat(path); err == nil {
			os.Remove(path)
			slog.Info("tunnel config removed (no public services)")
		}
		return nil
	}

	if err := storage.WriteFileAtomic(m.configPath(), []byte(content), 0644); err != nil {
		return fmt.Errorf("writing tunnel config: %w", err)
	}

	slog.Info("tunnel config written", "path", m.configPath(), "services", len(services))
	return nil
}

// GetStatus returns the current tunnel status.
func (m *Manager) GetStatus(cfg Config) map[string]any {
	status := map[string]any{
		"enabled":      cfg.Enabled,
		"tunnelId":     cfg.TunnelID,
		"publicDomain": cfg.PublicDomain,
		"configPath":   m.configPath(),
	}

	// Check if cloudflared is running
	cmd := exec.Command("systemctl", "is-active", "cloudflared.service")
	output, err := cmd.Output()
	if err != nil {
		status["service"] = "inactive"
	} else {
		status["service"] = strings.TrimSpace(string(output))
	}

	// Check if config exists
	if _, err := os.Stat(m.configPath()); err == nil {
		status["configExists"] = true
	} else {
		status["configExists"] = false
	}

	return status
}

// ReloadService restarts the cloudflared service to pick up new config.
func (m *Manager) ReloadService() error {
	cmd := exec.Command("systemctl", "restart", "cloudflared.service")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to restart cloudflared: %w (output: %s)", err, string(output))
	}
	slog.Info("cloudflared service restarted")
	return nil
}