package main

import (
	"context"
	"fmt"
	"log"
	"net"

	messages "git.tornberg.me/go-cart-actor/proto"
	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"
)

// cartActorGRPCServer implements the CartActor and ControlPlane gRPC services.
// It delegates cart operations to a grain pool and cluster operations to a synced pool.
type cartActorGRPCServer struct {
	messages.UnimplementedCartActorServer
	messages.UnimplementedControlPlaneServer

	pool       GrainPool  // For cart state mutations and queries
	syncedPool *SyncedPool // For cluster membership and control
}

// NewCartActorGRPCServer creates and initializes the server.
func NewCartActorGRPCServer(pool GrainPool, syncedPool *SyncedPool) *cartActorGRPCServer {
	return &cartActorGRPCServer{
		pool:       pool,
		syncedPool: syncedPool,
	}
}

// Mutate applies a mutation from an envelope to the corresponding cart grain.
func (s *cartActorGRPCServer) Mutate(ctx context.Context, envelope *messages.MutationEnvelope) (*messages.MutationReply, error) {
	if envelope.GetCartId() == "" {
		return &messages.MutationReply{
			StatusCode: 400,
			Result:     &messages.MutationReply_Error{Error: "cart_id is required"},
		}, nil
	}
	cartID := ToCartId(envelope.GetCartId())

	var mutation interface{}
	switch m := envelope.Mutation.(type) {
	case *messages.MutationEnvelope_AddRequest:
		mutation = m.AddRequest
	case *messages.MutationEnvelope_AddItem:
		mutation = m.AddItem
	case *messages.MutationEnvelope_RemoveItem:
		mutation = m.RemoveItem
	case *messages.MutationEnvelope_RemoveDelivery:
		mutation = m.RemoveDelivery
	case *messages.MutationEnvelope_ChangeQuantity:
		mutation = m.ChangeQuantity
	case *messages.MutationEnvelope_SetDelivery:
		mutation = m.SetDelivery
	case *messages.MutationEnvelope_SetPickupPoint:
		mutation = m.SetPickupPoint
	case *messages.MutationEnvelope_CreateCheckoutOrder:
		mutation = m.CreateCheckoutOrder
	case *messages.MutationEnvelope_SetCartItems:
		mutation = m.SetCartItems
	case *messages.MutationEnvelope_OrderCompleted:
		mutation = m.OrderCompleted
	default:
		return &messages.MutationReply{
			StatusCode: 400,
			Result:     &messages.MutationReply_Error{Error: fmt.Sprintf("unsupported mutation type: %T", m)},
		}, nil
	}

	// Delegate the mutation to the grain pool.
	// The pool is responsible for routing it to the correct grain (local or remote).
	grain, err := s.pool.Process(cartID, mutation)
	if err != nil {
		return &messages.MutationReply{
			StatusCode: 500,
			Result:     &messages.MutationReply_Error{Error: err.Error()},
		}, nil
	}

	// Map the internal grain state to the protobuf representation.
	cartState := ToCartState(grain)

	return &messages.MutationReply{
		StatusCode: 200,
		Result:     &messages.MutationReply_State{State: cartState},
	}, nil
}

// GetState retrieves the current state of a cart grain.
func (s *cartActorGRPCServer) GetState(ctx context.Context, req *messages.StateRequest) (*messages.StateReply, error) {
	if req.GetCartId() == "" {
		return &messages.StateReply{
			StatusCode: 400,
			Result:     &messages.StateReply_Error{Error: "cart_id is required"},
		}, nil
	}
	cartID := ToCartId(req.GetCartId())

	grain, err := s.pool.Get(cartID)
	if err != nil {
		return &messages.StateReply{
			StatusCode: 500,
			Result:     &messages.StateReply_Error{Error: err.Error()},
		}, nil
	}

	cartState := ToCartState(grain)

	return &messages.StateReply{
		StatusCode: 200,
		Result:     &messages.StateReply_State{State: cartState},
	}, nil
}

// StartGRPCServer configures and starts the unified gRPC server on the given address.
// It registers both the CartActor and ControlPlane services.
func StartGRPCServer(addr string, pool GrainPool, syncedPool *SyncedPool) (*grpc.Server, error) {
	lis, err := net.Listen("tcp", addr)
	if err != nil {
		return nil, fmt.Errorf("failed to listen: %w", err)
	}

	grpcServer := grpc.NewServer()
	server := NewCartActorGRPCServer(pool, syncedPool)

	messages.RegisterCartActorServer(grpcServer, server)
	messages.RegisterControlPlaneServer(grpcServer, server)
	reflection.Register(grpcServer)

	log.Printf("gRPC server listening on %s", addr)
	go func() {
		if err := grpcServer.Serve(lis); err != nil {
			log.Fatalf("failed to serve gRPC: %v", err)
		}
	}()

	return grpcServer, nil
}