package gateway

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"time"

	"gitea.nik4nao.com/nik/home-services/discord-bot/internal/core/ports/driven"
	"gitea.nik4nao.com/nik/home-services/discord-bot/internal/logger"
	hav1 "gitea.nik4nao.com/nik/home-services/gen/ha/v1"
	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/credentials/insecure"
)

// Client implements the app's HA driven port over gRPC.
type Client struct {
	conn         *grpc.ClientConn
	lightClient  hav1.LightServiceClient
	switchClient hav1.SwitchServiceClient
	log          *slog.Logger
}

// New constructs a gRPC client for the internal ha-gateway service.
func New(ctx context.Context, addr, tlsDir string, log *slog.Logger) (*Client, error) {
	transportCreds := insecure.NewCredentials()
	if tlsDir != "" {
		creds, err := loadTransportCredentials(tlsDir)
		if err != nil {
			return nil, fmt.Errorf("load mTLS credentials: %w", err)
		}
		transportCreds = creds
	}

	conn, err := grpc.NewClient(
		addr,
		grpc.WithTransportCredentials(transportCreds),
		grpc.WithStatsHandler(otelgrpc.NewClientHandler()),
	)
	if err != nil {
		return nil, fmt.Errorf("dial ha-gateway: %w", err)
	}

	return &Client{
		conn:         conn,
		lightClient:  hav1.NewLightServiceClient(conn),
		switchClient: hav1.NewSwitchServiceClient(conn),
		log:          log,
	}, nil
}

// Close closes the underlying gRPC connection.
func (c *Client) Close() error {
	if err := c.conn.Close(); err != nil {
		return fmt.Errorf("close ha-gateway client: %w", err)
	}
	return nil
}

func loadTransportCredentials(tlsDir string) (credentials.TransportCredentials, error) {
	cert, err := tls.LoadX509KeyPair(
		filepath.Join(tlsDir, "tls.crt"),
		filepath.Join(tlsDir, "tls.key"),
	)
	if err != nil {
		return nil, fmt.Errorf("load client key pair: %w", err)
	}

	caPEM, err := os.ReadFile(filepath.Join(tlsDir, "ca.crt"))
	if err != nil {
		return nil, fmt.Errorf("read server CA: %w", err)
	}

	rootCAs := x509.NewCertPool()
	if !rootCAs.AppendCertsFromPEM(caPEM) {
		return nil, fmt.Errorf("append server CA: invalid PEM")
	}

	return credentials.NewTLS(&tls.Config{
		Certificates: []tls.Certificate{cert},
		RootCAs:      rootCAs,
		ServerName:   "ha-gateway.home-services.svc.cluster.local",
		MinVersion:   tls.VersionTLS13,
	}), nil
}

// ListLights calls ha-gateway discovery RPCs and maps protobuf messages into
// the driven port type expected by the app layer.
func (c *Client) ListLights(ctx context.Context) ([]driven.Light, error) {
	start := time.Now()
	log := logger.FromContext(ctx).With("grpc.method", "LightService/ListLights")
	resp, err := c.lightClient.ListLights(ctx, &hav1.ListLightsRequest{})
	if err != nil {
		log.Error("grpc call failed",
			"duration_ms", time.Since(start).Milliseconds(),
			"error", err.Error(),
		)
		return nil, fmt.Errorf("list lights: %w", err)
	}
	log.Debug("grpc call completed", "duration_ms", time.Since(start).Milliseconds())

	lights := make([]driven.Light, 0, len(resp.GetLights()))
	for _, light := range resp.GetLights() {
		lights = append(lights, driven.Light{
			EntityID:            light.GetEntityId(),
			FriendlyName:        light.GetFriendlyName(),
			State:               light.GetState(),
			SupportedColorModes: append([]string(nil), light.GetSupportedColorModes()...),
			MinColorTempKelvin:  light.GetMinColorTempKelvin(),
			MaxColorTempKelvin:  light.GetMaxColorTempKelvin(),
			IsHueGroup:          light.GetIsHueGroup(),
			EffectList:          append([]string(nil), light.GetEffectList()...),
		})
	}
	return lights, nil
}

// ListSwitches calls ha-gateway discovery RPCs and maps protobuf messages into
// the driven port type expected by the app layer.
func (c *Client) ListSwitches(ctx context.Context) ([]driven.Switch, error) {
	start := time.Now()
	log := logger.FromContext(ctx).With("grpc.method", "SwitchService/ListSwitches")
	resp, err := c.switchClient.ListSwitches(ctx, &hav1.ListSwitchesRequest{})
	if err != nil {
		log.Error("grpc call failed",
			"duration_ms", time.Since(start).Milliseconds(),
			"error", err.Error(),
		)
		return nil, fmt.Errorf("list switches: %w", err)
	}
	log.Debug("grpc call completed", "duration_ms", time.Since(start).Milliseconds())

	switches := make([]driven.Switch, 0, len(resp.GetSwitches()))
	for _, sw := range resp.GetSwitches() {
		switches = append(switches, driven.Switch{
			EntityID:     sw.GetEntityId(),
			FriendlyName: sw.GetFriendlyName(),
			State:        sw.GetState(),
			DeviceClass:  sw.GetDeviceClass(),
		})
	}
	return switches, nil
}

// TurnOnLight forwards a light turn-on request over gRPC.
func (c *Client) TurnOnLight(ctx context.Context, entityID string, brightnessPct *uint32, colorTempKelvin *uint32) error {
	start := time.Now()
	log := logger.FromContext(ctx).With("grpc.method", "LightService/TurnOn")
	req := &hav1.TurnOnRequest{EntityId: entityID}
	if brightnessPct != nil {
		req.BrightnessPct = brightnessPct
	}
	if colorTempKelvin != nil {
		req.ColorTempKelvin = colorTempKelvin
	}

	if _, err := c.lightClient.TurnOn(ctx, req); err != nil {
		log.Error("grpc call failed",
			"duration_ms", time.Since(start).Milliseconds(),
			"error", err.Error(),
		)
		return fmt.Errorf("turn on light %s: %w", entityID, err)
	}
	log.Debug("grpc call completed", "duration_ms", time.Since(start).Milliseconds())
	return nil
}

// TurnOffLight forwards a light turn-off request over gRPC.
func (c *Client) TurnOffLight(ctx context.Context, entityID string, transition *uint32) error {
	start := time.Now()
	log := logger.FromContext(ctx).With("grpc.method", "LightService/TurnOff")
	req := &hav1.TurnOffRequest{EntityId: entityID}
	if transition != nil {
		req.Transition = transition
	}

	if _, err := c.lightClient.TurnOff(ctx, req); err != nil {
		log.Error("grpc call failed",
			"duration_ms", time.Since(start).Milliseconds(),
			"error", err.Error(),
		)
		return fmt.Errorf("turn off light %s: %w", entityID, err)
	}
	log.Debug("grpc call completed", "duration_ms", time.Since(start).Milliseconds())
	return nil
}

// ToggleLight forwards a light toggle request over gRPC.
func (c *Client) ToggleLight(ctx context.Context, entityID string) error {
	start := time.Now()
	log := logger.FromContext(ctx).With("grpc.method", "LightService/Toggle")
	if _, err := c.lightClient.Toggle(ctx, &hav1.ToggleRequest{EntityId: entityID}); err != nil {
		log.Error("grpc call failed",
			"duration_ms", time.Since(start).Milliseconds(),
			"error", err.Error(),
		)
		return fmt.Errorf("toggle light %s: %w", entityID, err)
	}
	log.Debug("grpc call completed", "duration_ms", time.Since(start).Milliseconds())
	return nil
}