// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package backend

import (
	"context"
	"sync"

	"github.com/talos-systems/grpc-proxy/proxy"
	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"
)

// Local implements local backend (proxying one2one to local service).
type Local struct {
	name       string
	socketPath string

	mu   sync.Mutex
	conn *grpc.ClientConn
}

// NewLocal builds new Local backend.
func NewLocal(name, socketPath string) *Local {
	return &Local{
		name:       name,
		socketPath: socketPath,
	}
}

func (l *Local) String() string {
	return l.name
}

// GetConnection returns a grpc connection to the backend.
func (l *Local) GetConnection(ctx context.Context) (context.Context, *grpc.ClientConn, error) {
	l.mu.Lock()
	defer l.mu.Unlock()

	// copy metadata
	outCtx := ctx
	if md, ok := metadata.FromIncomingContext(ctx); ok {
		outCtx = metadata.NewOutgoingContext(ctx, md)
	}

	if l.conn != nil {
		return outCtx, l.conn, nil
	}

	var err error
	l.conn, err = grpc.DialContext(
		ctx,
		"unix:"+l.socketPath,
		grpc.WithInsecure(),
		grpc.WithCodec(proxy.Codec()), //nolint: staticcheck

	)

	return outCtx, l.conn, err
}

// AppendInfo is called to enhance response from the backend with additional data.
func (l *Local) AppendInfo(streaming bool, resp []byte) ([]byte, error) {
	return resp, nil
}

// BuildError is called to convert error from upstream into response field.
func (l *Local) BuildError(streaming bool, err error) ([]byte, error) {
	return nil, nil
}