package hagateway

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

	"gitea.nik4nao.com/nik/home-services/ai-gateway/internal/core/ports/driven"
	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 HA driven port over gRPC.
type Client struct {
	conn        *grpc.ClientConn
	lightClient hav1.LightServiceClient
	log         *slog.Logger
}

// New constructs a gRPC client for ha-gateway with optional mTLS.
func New(ctx context.Context, addr, tlsDir, serverName string, log *slog.Logger) (*Client, error) {
	transportCreds := insecure.NewCredentials()
	if tlsDir != "" {
		creds, err := loadTransportCredentials(tlsDir, serverName)
		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),
		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
}

// ListLights loads the discovery list used by prompt-building and list replies.
func (c *Client) ListLights(ctx context.Context) ([]driven.Light, error) {
	start := time.Now()
	resp, err := c.lightClient.ListLights(ctx, &hav1.ListLightsRequest{})
	if err != nil {
		return nil, fmt.Errorf("list lights: %w", err)
	}
	c.log.Debug("grpc call completed", "grpc.method", "LightService/ListLights", "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(),
		})
	}
	return lights, nil
}

// TurnOnLight forwards a turn-on request to ha-gateway.
func (c *Client) TurnOnLight(ctx context.Context, entity string, params map[string]string) error {
	start := time.Now()
	req := &hav1.TurnOnRequest{EntityId: entity}
	if v, ok := firstParam(params, "brightness", "brightness_pct"); ok {
		brightness, err := parseUint32(v)
		if err != nil {
			return err
		}
		req.BrightnessPct = &brightness
	}
	if v, ok := firstParam(params, "color_temp", "color_temp_kelvin"); ok {
		colorTemp, err := parseUint32(v)
		if err != nil {
			return err
		}
		req.ColorTempKelvin = &colorTemp
	}

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

// TurnOffLight forwards a turn-off request to ha-gateway.
func (c *Client) TurnOffLight(ctx context.Context, entity string) error {
	start := time.Now()
	if _, err := c.lightClient.TurnOff(ctx, &hav1.TurnOffRequest{EntityId: entity}); err != nil {
		return fmt.Errorf("turn off light %s: %w", entity, err)
	}
	c.log.Debug("grpc call completed", "grpc.method", "LightService/TurnOff", "duration_ms", time.Since(start).Milliseconds())
	return nil
}

func loadTransportCredentials(tlsDir, serverName 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:   serverName,
		MinVersion:   tls.VersionTLS13,
	}), nil
}

func firstParam(params map[string]string, keys ...string) (string, bool) {
	for _, key := range keys {
		if v, ok := params[key]; ok {
			return v, true
		}
	}
	return "", false
}

func parseUint32(v string) (uint32, error) {
	n, err := strconv.ParseUint(v, 10, 32)
	if err != nil {
		return 0, fmt.Errorf("parse uint32 value %q: %w", v, err)
	}
	return uint32(n), nil
}