/*
   Copyright 2020 Docker Compose CLI authors

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package server

import (
	"context"
	"errors"
	"strings"

	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"

	"github.com/docker/compose-cli/api/client"
	"github.com/docker/compose-cli/api/config"
	apicontext "github.com/docker/compose-cli/api/context"
	"github.com/docker/compose-cli/api/context/store"
	"github.com/docker/compose-cli/cli/server/proxy"
)

// key is the key where the current docker context is stored in the metadata
// of a gRPC request
const key = "context_key"

// unaryServerInterceptor configures the context and sends it to the next handler
func unaryServerInterceptor(clictx context.Context) grpc.UnaryServerInterceptor {
	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
		currentContext, err := getIncomingContext(ctx)
		if err != nil {
			currentContext, err = getConfigContext()
			if err != nil {
				return nil, err
			}
		}
		configuredCtx, err := configureContext(clictx, currentContext, info.FullMethod)
		if err != nil {
			return nil, err
		}

		return handler(configuredCtx, req)
	}
}

// streamServerInterceptor configures the context and sends it to the next handler
func streamServerInterceptor(clictx context.Context) grpc.StreamServerInterceptor {
	return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
		currentContext, err := getIncomingContext(ss.Context())
		if err != nil {
			currentContext, err = getConfigContext()
			if err != nil {
				return err
			}
		}
		ctx, err := configureContext(clictx, currentContext, info.FullMethod)
		if err != nil {
			return err
		}

		return handler(srv, &contextServerStream{
			ss:  ss,
			ctx: ctx,
		})
	}
}

// Returns the current context from the configuration file
func getConfigContext() (string, error) {
	configDir := config.Dir()
	configFile, err := config.LoadFile(configDir)
	if err != nil {
		return "", err
	}
	return configFile.CurrentContext, nil
}

// Returns the context set by the caller if any, error otherwise
func getIncomingContext(ctx context.Context) (string, error) {
	if md, ok := metadata.FromIncomingContext(ctx); ok {
		if key, ok := md[key]; ok {
			return key[0], nil
		}
	}

	return "", errors.New("not found")
}

// configureContext populates the request context with objects the client
// needs: the context store and the api client
func configureContext(ctx context.Context, currentContext string, method string) (context.Context, error) {
	configDir := config.Dir()

	apicontext.WithCurrentContext(currentContext)

	// The contexts service doesn't need the client
	if !strings.Contains(method, "/com.docker.api.protos.context.v1.Contexts") {
		c, err := client.New(ctx)
		if err != nil {
			return nil, err
		}

		ctx = proxy.WithClient(ctx, c)
	}

	s, err := store.New(configDir)
	if err != nil {
		return nil, err
	}
	store.WithContextStore(s)

	return ctx, nil
}