package rpc

import (
	"context"
	"sync"

	"forge.cadoles.com/arcad/edge/pkg/app"
	"forge.cadoles.com/arcad/edge/pkg/bus"
	edgehttp "forge.cadoles.com/arcad/edge/pkg/http"
	"forge.cadoles.com/arcad/edge/pkg/module/util"
	"github.com/dop251/goja"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type Module struct {
	server    *app.Server
	bus       bus.Bus
	callbacks sync.Map
}

func (m *Module) Name() string {
	return "rpc"
}

func (m *Module) Export(export *goja.Object) {
	if err := export.Set("register", m.register); err != nil {
		panic(errors.Wrap(err, "could not set 'register' function"))
	}

	if err := export.Set("unregister", m.unregister); err != nil {
		panic(errors.Wrap(err, "could not set 'unregister' function"))
	}
}

func (m *Module) OnInit(ctx context.Context, rt *goja.Runtime) error {
	requestErrs := m.bus.Reply(ctx, Address, m.handleRequest)
	go func() {
		for err := range requestErrs {
			logger.Error(ctx, "error while replying to rpc requests", logger.CapturedE(errors.WithStack(err)))
		}
	}()

	httpIncomingMessages, err := m.bus.Subscribe(ctx, edgehttp.AddressIncomingMessage)
	if err != nil {
		return errors.WithStack(err)
	}

	go m.handleIncomingHTTPMessages(ctx, httpIncomingMessages)

	return nil
}

func (m *Module) register(call goja.FunctionCall, rt *goja.Runtime) goja.Value {
	fnName := util.AssertString(call.Argument(0), rt)

	var (
		callable goja.Callable
		ok       bool
	)

	if len(call.Arguments) > 1 {
		callable, ok = goja.AssertFunction(call.Argument(1))
	} else {
		callable, ok = goja.AssertFunction(rt.Get(fnName))
	}

	if !ok {
		panic(rt.NewTypeError("method should be a valid function"))
	}

	ctx := context.Background()

	logger.Debug(ctx, "registering method", logger.F("method", fnName))

	m.callbacks.Store(fnName, callable)

	return nil
}

func (m *Module) unregister(call goja.FunctionCall, rt *goja.Runtime) goja.Value {
	fnName := util.AssertString(call.Argument(0), rt)

	m.callbacks.Delete(fnName)

	return nil
}

func (m *Module) handleRequest(env bus.Envelope) (any, error) {
	request, ok := env.Message().(*Request)
	if !ok {
		logger.Warn(context.Background(), "unexpected bus message", logger.F("message", env.Message()))

		return nil, errors.WithStack(bus.ErrUnexpectedMessage)
	}

	ctx := logger.With(request.Context, logger.F("request", request))

	logger.Debug(ctx, "received rpc request")

	rawCallable, exists := m.callbacks.Load(request.Method)
	if !exists {
		logger.Debug(ctx, "method not found")

		return nil, errors.WithStack(ErrMethodNotFound)
	}

	callable, ok := rawCallable.(goja.Callable)
	if !ok {
		logger.Debug(ctx, "invalid method")

		return nil, errors.WithStack(ErrMethodNotFound)
	}

	result, err := m.server.Exec(ctx, callable, request.Context, request.Params)
	if err != nil {
		logger.Error(
			ctx, "rpc call error",
			logger.CapturedE(errors.WithStack(err)),
		)

		return nil, errors.WithStack(err)
	}

	return result, nil
}

func (m *Module) handleIncomingHTTPMessages(ctx context.Context, incoming <-chan bus.Envelope) {
	defer func() {
		m.bus.Unsubscribe(edgehttp.AddressIncomingMessage, incoming)
	}()

	for env := range incoming {
		msg, ok := env.Message().(*edgehttp.IncomingMessage)
		if !ok {
			logger.Error(ctx, "unexpected incoming http message type", logger.F("message", env.Message()))
			continue
		}

		jsonReq, ok := m.isRPCRequest(msg.Payload)
		if !ok {
			continue
		}

		sessionID, ok := edgehttp.ContextSessionID(msg.Context)
		if !ok {
			logger.Error(ctx, "could not find session id in context")
			continue
		}

		request := NewRequestEnvelope(msg.Context, jsonReq.Method, jsonReq.Params)

		requestCtx := logger.With(msg.Context, logger.F("rpcRequestMethod", jsonReq.Method), logger.F("rpcRequestID", jsonReq.ID))

		reply, err := m.bus.Request(requestCtx, request)
		if err != nil {
			err = errors.WithStack(err)

			logger.Error(
				ctx, "could not execute rpc request",
				logger.CapturedE(err),
			)

			if errors.Is(err, ErrMethodNotFound) {
				if err := m.sendMethodNotFoundResponse(sessionID, jsonReq.ID); err != nil {
					logger.Error(
						ctx, "could not send json rpc error response",
						logger.CapturedE(errors.WithStack(err)),
					)
				}

				continue
			}

			if err := m.sendErrorResponse(sessionID, jsonReq.ID, err); err != nil {
				logger.Error(
					ctx, "could not send json rpc error response",
					logger.CapturedE(errors.WithStack(err)),
				)
			}

			continue
		}

		if err := m.sendResponse(sessionID, jsonReq.ID, reply.Message(), nil); err != nil {
			logger.Error(
				ctx, "could not send json rpc result response",
				logger.CapturedE(err),
			)
		}
	}
}

func (m *Module) sendErrorResponse(sessionID string, requestID any, err error) error {
	return m.sendResponse(sessionID, requestID, nil, &JSONRPCError{
		Code:    -32603,
		Message: err.Error(),
	})
}

func (m *Module) sendMethodNotFoundResponse(sessionID string, requestID any) error {
	return m.sendResponse(sessionID, requestID, nil, &JSONRPCError{
		Code:    -32601,
		Message: "method not found",
	})
}

func (m *Module) sendResponse(sessionID string, requestID any, result any, err error) error {
	env := edgehttp.NewOutgoingMessageEnvelope(sessionID, map[string]interface{}{
		"jsonrpc": "2.0",
		"id":      requestID,
		"error":   err,
		"result":  result,
	})

	if err := m.bus.Publish(env); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (m *Module) isRPCRequest(payload map[string]any) (*JSONRPCRequest, bool) {
	jsonRPC, exists := payload["jsonrpc"]
	if !exists || jsonRPC != "2.0" {
		return nil, false
	}

	rawMethod, exists := payload["method"]
	if !exists {
		return nil, false
	}

	method, ok := rawMethod.(string)
	if !ok {
		return nil, false
	}

	id := payload["id"]
	params := payload["params"]

	return &JSONRPCRequest{
		ID:     id,
		Method: method,
		Params: params,
	}, true
}

func ModuleFactory(bus bus.Bus) app.ServerModuleFactory {
	return func(server *app.Server) app.ServerModule {
		mod := &Module{
			server: server,
			bus:    bus,
		}

		return mod
	}
}

var _ app.InitializableModule = &Module{}