/*
Copyright 2017 Google Inc. All Rights Reserved.

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 testutil

import (
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"testing"
	"time"

	"golang.org/x/net/context"

	"github.com/golang/protobuf/ptypes/empty"
	proto3 "github.com/golang/protobuf/ptypes/struct"
	pbt "github.com/golang/protobuf/ptypes/timestamp"

	sppb "google.golang.org/genproto/googleapis/spanner/v1"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
)

var (
	// KvMeta is the Metadata for mocked KV table.
	KvMeta = sppb.ResultSetMetadata{
		RowType: &sppb.StructType{
			Fields: []*sppb.StructType_Field{
				{
					Name: "Key",
					Type: &sppb.Type{Code: sppb.TypeCode_STRING},
				},
				{
					Name: "Value",
					Type: &sppb.Type{Code: sppb.TypeCode_STRING},
				},
			},
		},
	}
)

// MockCtlMsg encapsulates PartialResultSet/error that might be sent to
// client
type MockCtlMsg struct {
	// If ResumeToken == true, mock server will generate a row with
	// resume token.
	ResumeToken bool
	// If Err != nil, mock server will return error in RPC response.
	Err error
}

// MockCloudSpanner is a mock implementation of SpannerServer interface.
// TODO: make MockCloudSpanner a full-fleged Cloud Spanner implementation.
type MockCloudSpanner struct {
	s      *grpc.Server
	t      *testing.T
	addr   string
	msgs   chan MockCtlMsg
	readTs time.Time
	next   int

	// embed nil interface so updating proto with new methods don't fail the build
	sppb.SpannerServer
}

// Addr returns the listening address of mock server.
func (m *MockCloudSpanner) Addr() string {
	return m.addr
}

// AddMsg generates a new mocked row which can be received by client.
func (m *MockCloudSpanner) AddMsg(err error, resumeToken bool) {
	msg := MockCtlMsg{
		ResumeToken: resumeToken,
		Err:         err,
	}
	if err == io.EOF {
		close(m.msgs)
	} else {
		m.msgs <- msg
	}
}

// Done signals an end to a mocked stream.
func (m *MockCloudSpanner) Done() {
	close(m.msgs)
}

// CreateSession is a placeholder for SpannerServer.CreateSession.
func (m *MockCloudSpanner) CreateSession(c context.Context, r *sppb.CreateSessionRequest) (*sppb.Session, error) {
	m.t.Fatalf("CreateSession is unimplemented")
	return nil, errors.New("Unimplemented")
}

// GetSession is a placeholder for SpannerServer.GetSession.
func (m *MockCloudSpanner) GetSession(c context.Context, r *sppb.GetSessionRequest) (*sppb.Session, error) {
	m.t.Fatalf("GetSession is unimplemented")
	return nil, errors.New("Unimplemented")
}

// DeleteSession is a placeholder for SpannerServer.DeleteSession.
func (m *MockCloudSpanner) DeleteSession(c context.Context, r *sppb.DeleteSessionRequest) (*empty.Empty, error) {
	m.t.Fatalf("DeleteSession is unimplemented")
	return nil, errors.New("Unimplemented")
}

// ExecuteSql is a placeholder for SpannerServer.ExecuteSql.
func (m *MockCloudSpanner) ExecuteSql(c context.Context, r *sppb.ExecuteSqlRequest) (*sppb.ResultSet, error) {
	m.t.Fatalf("ExecuteSql is unimplemented")
	return nil, errors.New("Unimplemented")
}

// EncodeResumeToken return mock resume token encoding for an uint64 integer.
func EncodeResumeToken(t uint64) []byte {
	rt := make([]byte, 16)
	binary.PutUvarint(rt, t)
	return rt
}

// DecodeResumeToken decodes a mock resume token into an uint64 integer.
func DecodeResumeToken(t []byte) (uint64, error) {
	s, n := binary.Uvarint(t)
	if n <= 0 {
		return 0, fmt.Errorf("invalid resume token: %v", t)
	}
	return s, nil
}

// ExecuteStreamingSql is a mock implementation of SpannerServer.ExecuteStreamingSql.
func (m *MockCloudSpanner) ExecuteStreamingSql(r *sppb.ExecuteSqlRequest, s sppb.Spanner_ExecuteStreamingSqlServer) error {
	switch r.Sql {
	case "SELECT * from t_unavailable":
		return grpc.Errorf(codes.Unavailable, "mock table unavailable")
	case "SELECT t.key key, t.value value FROM t_mock t":
		if r.ResumeToken != nil {
			s, err := DecodeResumeToken(r.ResumeToken)
			if err != nil {
				return err
			}
			m.next = int(s) + 1
		}
		for {
			msg, more := <-m.msgs
			if !more {
				break
			}
			if msg.Err == nil {
				var rt []byte
				if msg.ResumeToken {
					rt = EncodeResumeToken(uint64(m.next))
				}
				meta := KvMeta
				meta.Transaction = &sppb.Transaction{
					ReadTimestamp: &pbt.Timestamp{
						Seconds: m.readTs.Unix(),
						Nanos:   int32(m.readTs.Nanosecond()),
					},
				}
				err := s.Send(&sppb.PartialResultSet{
					Metadata: &meta,
					Values: []*proto3.Value{
						{Kind: &proto3.Value_StringValue{StringValue: fmt.Sprintf("foo-%02d", m.next)}},
						{Kind: &proto3.Value_StringValue{StringValue: fmt.Sprintf("bar-%02d", m.next)}},
					},
					ResumeToken: rt,
				})
				m.next = m.next + 1
				if err != nil {
					return err
				}
				continue
			}
			return msg.Err
		}
		return nil
	default:
		return fmt.Errorf("unsupported SQL: %v", r.Sql)
	}
}

// Read is a placeholder for SpannerServer.Read.
func (m *MockCloudSpanner) Read(c context.Context, r *sppb.ReadRequest) (*sppb.ResultSet, error) {
	m.t.Fatalf("Read is unimplemented")
	return nil, errors.New("Unimplemented")
}

// StreamingRead is a placeholder for SpannerServer.StreamingRead.
func (m *MockCloudSpanner) StreamingRead(r *sppb.ReadRequest, s sppb.Spanner_StreamingReadServer) error {
	m.t.Fatalf("StreamingRead is unimplemented")
	return errors.New("Unimplemented")
}

// BeginTransaction is a placeholder for SpannerServer.BeginTransaction.
func (m *MockCloudSpanner) BeginTransaction(c context.Context, r *sppb.BeginTransactionRequest) (*sppb.Transaction, error) {
	m.t.Fatalf("BeginTransaction is unimplemented")
	return nil, errors.New("Unimplemented")
}

// Commit is a placeholder for SpannerServer.Commit.
func (m *MockCloudSpanner) Commit(c context.Context, r *sppb.CommitRequest) (*sppb.CommitResponse, error) {
	m.t.Fatalf("Commit is unimplemented")
	return nil, errors.New("Unimplemented")
}

// Rollback is a placeholder for SpannerServer.Rollback.
func (m *MockCloudSpanner) Rollback(c context.Context, r *sppb.RollbackRequest) (*empty.Empty, error) {
	m.t.Fatalf("Rollback is unimplemented")
	return nil, errors.New("Unimplemented")
}

// Serve runs a MockCloudSpanner listening on a random localhost address.
func (m *MockCloudSpanner) Serve() {
	m.s = grpc.NewServer()
	if m.addr == "" {
		m.addr = "localhost:0"
	}
	lis, err := net.Listen("tcp", m.addr)
	if err != nil {
		m.t.Fatalf("Failed to listen: %v", err)
	}
	_, port, err := net.SplitHostPort(lis.Addr().String())
	if err != nil {
		m.t.Fatalf("Failed to parse listener address: %v", err)
	}
	sppb.RegisterSpannerServer(m.s, m)
	m.addr = "localhost:" + port
	go m.s.Serve(lis)
}

// Stop terminates MockCloudSpanner and closes the serving port.
func (m *MockCloudSpanner) Stop() {
	m.s.Stop()
}

// NewMockCloudSpanner creates a new MockCloudSpanner instance.
func NewMockCloudSpanner(t *testing.T, ts time.Time) *MockCloudSpanner {
	mcs := &MockCloudSpanner{
		t:      t,
		msgs:   make(chan MockCtlMsg, 1000),
		readTs: ts,
	}
	return mcs
}