package config

import (
	"fmt"
	"os"
	"time"
)

// Config is the top-level configuration for the Kedge DaemonSet.
type Config struct {
	NodeID       string              `json:"node_id"`
	ClusterID    string              `json:"cluster_id"`
	Mesh         MeshConfig          `json:"mesh"`
	VLAN         VLANConfig          `json:"vlan"`
	Shellstream  ShellstreamConfig   `json:"shellstream"`
	Quartermaster QuartermasterConfig `json:"quartermaster"`
	Underlay     UnderlayConfig      `json:"underlay"`
	Health       HealthConfig        `json:"health"`
	Headscale    HeadscaleConfig     `json:"headscale"`
}

// MeshConfig configures the WireGuard overlay mesh.
type MeshConfig struct {
	Enabled         bool          `json:"enabled"`
	InterfaceName   string        `json:"interface_name"`
	ListenPort      int           `json:"listen_port"`
	PrivateKeyPath  string        `json:"private_key_path"`
	HealthInterval  time.Duration `json:"health_interval"`
	DeadPeerTimeout time.Duration `json:"dead_peer_timeout"`
	InitialPeers    []PeerEntry   `json:"initial_peers"`
}

// PeerEntry defines a WireGuard peer from configuration.
type PeerEntry struct {
	PublicKey  string   `json:"public_key"`
	Endpoint  string   `json:"endpoint"`
	AllowedIPs []string `json:"allowed_ips"`
}

// VLANConfig configures underlay VLAN interfaces.
type VLANConfig struct {
	Enabled bool        `json:"enabled"`
	VLANs   []VLANEntry `json:"vlans"`
}

// VLANEntry defines a VLAN to be managed on the node.
type VLANEntry struct {
	ID              int    `json:"id"`
	ParentInterface string `json:"parent_interface"`
	Subnet          string `json:"subnet"`
	Description     string `json:"description"`
}

// ShellstreamConfig configures the Shellstream handshake listener.
type ShellstreamConfig struct {
	ListenAddr       string `json:"listen_addr"`
	ClusterID        string `json:"cluster_id"`
	TrustBundlePath  string `json:"trust_bundle_path"`
	AccordPolicyPath string `json:"accord_policy_path"`
}

// QuartermasterConfig configures the Quartermaster gRPC client.
type QuartermasterConfig struct {
	Endpoint string `json:"endpoint"`
	UseTLS   bool   `json:"use_tls"`
	CertPath string `json:"cert_path,omitempty"`
	KeyPath  string `json:"key_path,omitempty"`
	CAPath   string `json:"ca_path,omitempty"`
}

// UnderlayConfig configures the YANG watcher and compilation trigger.
type UnderlayConfig struct {
	Enabled       bool   `json:"enabled"`
	Namespace     string `json:"namespace"`
	ConfigMapName string `json:"configmap_name"`
	CompilerPath  string `json:"compiler_path"`
}

// HealthConfig configures the health and metrics server.
type HealthConfig struct {
	ListenAddr string `json:"listen_addr"`
}

// HeadscaleConfig configures Headscale peer discovery.
type HeadscaleConfig struct {
	Enabled      bool          `json:"enabled"`
	Endpoint     string        `json:"endpoint"`
	APIKey       string        `json:"api_key"`
	PollInterval time.Duration `json:"poll_interval"`
}

// Load reads the DaemonSet configuration from environment variables and
// the config file at /etc/kedge/config.json.
func Load() (*Config, error) {
	cfg := &Config{
		NodeID:    getEnv("KEDGE_NODE_ID", ""),
		ClusterID: getEnv("KEDGE_CLUSTER_ID", ""),
		Mesh: MeshConfig{
			Enabled:         getEnv("KEDGE_OVERLAY_ENABLED", "true") == "true",
			InterfaceName:   getEnv("KEDGE_WG_INTERFACE", "wg0"),
			ListenPort:      51820,
			PrivateKeyPath:  getEnv("KEDGE_WG_PRIVATE_KEY", "/etc/kedge/wg-private.key"),
			HealthInterval:  30 * time.Second,
			DeadPeerTimeout: 5 * time.Minute,
		},
		VLAN: VLANConfig{
			Enabled: getEnv("KEDGE_UNDERLAY_ENABLED", "false") == "true",
		},
		Shellstream: ShellstreamConfig{
			ListenAddr:       getEnv("KEDGE_SHELLSTREAM_ADDR", ":8443"),
			ClusterID:        getEnv("KEDGE_CLUSTER_ID", ""),
			TrustBundlePath:  getEnv("KEDGE_TRUST_BUNDLE", "/run/spire/bundle/bundle.pem"),
			AccordPolicyPath: getEnv("KEDGE_ACCORD_POLICY", "/etc/kedge/accord-policy.json"),
		},
		Quartermaster: QuartermasterConfig{
			Endpoint: getEnv("KEDGE_QM_ENDPOINT", "quartermaster.guildhouse.svc:50051"),
		},
		Underlay: UnderlayConfig{
			Enabled:       getEnv("KEDGE_UNDERLAY_ENABLED", "false") == "true",
			Namespace:     getEnv("KEDGE_UNDERLAY_NAMESPACE", "kedge"),
			ConfigMapName: getEnv("KEDGE_UNDERLAY_CONFIGMAP", "kedge-underlay"),
			CompilerPath:  getEnv("KEDGE_YANG_COMPILER", "/opt/kedge/yang/compiler/compile.py"),
		},
		Health: HealthConfig{
			ListenAddr: getEnv("KEDGE_HEALTH_ADDR", ":9090"),
		},
		Headscale: HeadscaleConfig{
			Enabled:      getEnv("KEDGE_HEADSCALE_ENABLED", "false") == "true",
			Endpoint:     getEnv("KEDGE_HEADSCALE_ENDPOINT", ""),
			PollInterval: 60 * time.Second,
		},
	}

	if cfg.NodeID == "" {
		hostname, err := os.Hostname()
		if err != nil {
			return nil, fmt.Errorf("KEDGE_NODE_ID not set and hostname unavailable: %w", err)
		}
		cfg.NodeID = hostname
	}

	if cfg.ClusterID == "" {
		return nil, fmt.Errorf("KEDGE_CLUSTER_ID is required")
	}

	return cfg, nil
}

func getEnv(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}