/*
   Copyright 2021 Erigon contributors

   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 remotedb

import (
	"bytes"
	"context"
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"time"

	"github.com/c2h5oh/datasize"
	"github.com/ledgerwatch/erigon-lib/gointerfaces"
	"github.com/ledgerwatch/erigon-lib/gointerfaces/remote"
	"github.com/ledgerwatch/erigon-lib/kv"
	"github.com/ledgerwatch/erigon-lib/kv/mdbx"
	"github.com/ledgerwatch/erigon-lib/log"
	"google.golang.org/grpc"
	"google.golang.org/grpc/backoff"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/keepalive"
	"google.golang.org/grpc/test/bufconn"
	"google.golang.org/protobuf/types/known/emptypb"
)

// generate the messages and services
type remoteOpts struct {
	bucketsCfg  mdbx.TableCfgFunc
	inMemConn   *bufconn.Listener // for tests
	DialAddress string
	version     gointerfaces.Version
	log         log.Logger
}

type RemoteKV struct {
	conn     *grpc.ClientConn
	remoteKV remote.KVClient
	log      log.Logger
	buckets  kv.TableCfg
	opts     remoteOpts
}

type remoteTx struct {
	stream             remote.KV_TxClient
	ctx                context.Context
	streamCancelFn     context.CancelFunc
	db                 *RemoteKV
	cursors            []*remoteCursor
	statelessCursors   map[string]kv.Cursor
	streamingRequested bool
}

type remoteCursor struct {
	ctx        context.Context
	stream     remote.KV_TxClient
	tx         *remoteTx
	bucketName string
	bucketCfg  kv.TableCfgItem
	id         uint32
}

type remoteCursorDupSort struct {
	*remoteCursor
}

func (opts remoteOpts) ReadOnly() remoteOpts {
	return opts
}

func (opts remoteOpts) Path(path string) remoteOpts {
	opts.DialAddress = path
	return opts
}

func (opts remoteOpts) WithBucketsConfig(f mdbx.TableCfgFunc) remoteOpts {
	opts.bucketsCfg = f
	return opts
}

func (opts remoteOpts) InMem(listener *bufconn.Listener) remoteOpts {
	opts.inMemConn = listener
	return opts
}

func (opts remoteOpts) Open(certFile, keyFile, caCert string) (*RemoteKV, error) {
	var dialOpts []grpc.DialOption

	backoffCfg := backoff.DefaultConfig
	backoffCfg.BaseDelay = 500 * time.Millisecond
	backoffCfg.MaxDelay = 10 * time.Second
	dialOpts = []grpc.DialOption{
		grpc.WithConnectParams(grpc.ConnectParams{Backoff: backoffCfg, MinConnectTimeout: 10 * time.Minute}),
		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(int(15 * datasize.MB))),
		grpc.WithKeepaliveParams(keepalive.ClientParameters{}),
	}
	if certFile == "" {
		dialOpts = append(dialOpts, grpc.WithInsecure())
	} else {
		var creds credentials.TransportCredentials
		var err error
		if caCert == "" {
			creds, err = credentials.NewClientTLSFromFile(certFile, "")

			if err != nil {
				return nil, err
			}
		} else {
			// load peer cert/key, ca cert
			peerCert, err := tls.LoadX509KeyPair(certFile, keyFile)
			if err != nil {
				opts.log.Errorf("load peer cert/key: %s", err)
				return nil, err
			}
			caCert, err := ioutil.ReadFile(caCert)
			if err != nil {
				opts.log.Errorf("read ca cert: %s", err)
				return nil, err
			}
			caCertPool := x509.NewCertPool()
			caCertPool.AppendCertsFromPEM(caCert)
			creds = credentials.NewTLS(&tls.Config{
				Certificates: []tls.Certificate{peerCert},
				ClientCAs:    caCertPool,
				ClientAuth:   tls.RequireAndVerifyClientCert,
				//nolint:gosec
				InsecureSkipVerify: true, // This is to make it work when Common Name does not match - remove when procedure is updated for common name
			})
		}

		dialOpts = append(dialOpts, grpc.WithTransportCredentials(creds))
	}

	if opts.inMemConn != nil {
		dialOpts = append(dialOpts, grpc.WithContextDialer(func(ctx context.Context, url string) (net.Conn, error) {
			return opts.inMemConn.Dial()
		}))
	}

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	conn, err := grpc.DialContext(ctx, opts.DialAddress, dialOpts...)
	if err != nil {
		return nil, err
	}

	kvClient := remote.NewKVClient(conn)
	db := &RemoteKV{
		opts:     opts,
		conn:     conn,
		remoteKV: kvClient,
		log:      opts.log,
		buckets:  kv.TableCfg{},
	}
	customBuckets := opts.bucketsCfg(kv.ChaindataTablesCfg)
	for name, cfg := range customBuckets { // copy map to avoid changing global variable
		db.buckets[name] = cfg
	}

	return db, nil
}

func (opts remoteOpts) MustOpen() kv.RwDB {
	db, err := opts.Open("", "", "")
	if err != nil {
		panic(err)
	}
	return db
}

// NewRemote defines new remove KV connection (without actually opening it)
// version parameters represent the version the KV client is expecting,
// compatibility check will be performed when the KV connection opens
func NewRemote(v gointerfaces.Version, logger log.Logger) remoteOpts {
	return remoteOpts{bucketsCfg: mdbx.WithChaindataTables, version: v, log: logger}
}

func (db *RemoteKV) AllBuckets() kv.TableCfg {
	return db.buckets
}

func (db *RemoteKV) GrpcConn() *grpc.ClientConn {
	return db.conn
}

func (db *RemoteKV) EnsureVersionCompatibility() bool {
	versionReply, err := db.remoteKV.Version(context.Background(), &emptypb.Empty{}, grpc.WaitForReady(true))
	if err != nil {
		db.log.Errorf("getting Version", "error", err)
		return false
	}
	if !gointerfaces.EnsureVersion(db.opts.version, versionReply) {
		db.log.Errorf("incompatible interface versions: client=%s", db.opts.version.String(),
			"server", fmt.Sprintf("%d.%d.%d", versionReply.Major, versionReply.Minor, versionReply.Patch))
		return false
	}
	db.log.Infof("interfaces compatible: client=%s", db.opts.version.String(),
		"server", fmt.Sprintf("%d.%d.%d", versionReply.Major, versionReply.Minor, versionReply.Patch))
	return true
}

func (db *RemoteKV) Close() {
	if db.conn != nil {
		if err := db.conn.Close(); err != nil {
			db.log.Warnf("close remote DB: %s", err)
		} else {
			db.log.Infof("remote database closed")
		}
		db.conn = nil
	}
}

func (db *RemoteKV) BeginRo(ctx context.Context) (kv.Tx, error) {
	streamCtx, streamCancelFn := context.WithCancel(ctx) // We create child context for the stream so we can cancel it to prevent leak
	stream, err := db.remoteKV.Tx(streamCtx)
	if err != nil {
		streamCancelFn()
		return nil, err
	}
	return &remoteTx{ctx: ctx, db: db, stream: stream, streamCancelFn: streamCancelFn}, nil
}

func (db *RemoteKV) BeginRw(ctx context.Context) (kv.RwTx, error) {
	return nil, fmt.Errorf("remote db provider doesn't support .BeginRw method")
}

func (db *RemoteKV) View(ctx context.Context, f func(tx kv.Tx) error) (err error) {
	tx, err := db.BeginRo(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	return f(tx)
}

func (db *RemoteKV) Update(ctx context.Context, f func(tx kv.RwTx) error) (err error) {
	return fmt.Errorf("remote db provider doesn't support .Update method")
}

func (tx *remoteTx) CollectMetrics() {}
func (tx *remoteTx) IncrementSequence(bucket string, amount uint64) (uint64, error) {
	panic("not implemented yet")
}
func (tx *remoteTx) ReadSequence(bucket string) (uint64, error) {
	panic("not implemented yet")
}
func (tx *remoteTx) Append(bucket string, k, v []byte) error    { panic("no write methods") }
func (tx *remoteTx) AppendDup(bucket string, k, v []byte) error { panic("no write methods") }

func (tx *remoteTx) Commit() error {
	panic("remote db is read-only")
}

func (tx *remoteTx) Rollback() {
	for _, c := range tx.cursors {
		c.Close()
	}
	tx.closeGrpcStream()
}

func (tx *remoteTx) statelessCursor(bucket string) (kv.Cursor, error) {
	if tx.statelessCursors == nil {
		tx.statelessCursors = make(map[string]kv.Cursor)
	}
	c, ok := tx.statelessCursors[bucket]
	if !ok {
		var err error
		c, err = tx.Cursor(bucket)
		if err != nil {
			return nil, err
		}
		tx.statelessCursors[bucket] = c
	}
	return c, nil
}

func (tx *remoteTx) BucketSize(name string) (uint64, error) { panic("not implemented") }

// TODO: this must be optimized - and implemented as single command on server, with server-side buffered streaming
func (tx *remoteTx) ForEach(bucket string, fromPrefix []byte, walker func(k, v []byte) error) error {
	c, err := tx.Cursor(bucket)
	if err != nil {
		return err
	}
	defer c.Close()

	for k, v, err := c.Seek(fromPrefix); k != nil; k, v, err = c.Next() {
		if err != nil {
			return err
		}
		if err := walker(k, v); err != nil {
			return err
		}
	}
	return nil
}

// TODO: this must be optimized - and implemented as single command on server, with server-side buffered streaming
func (tx *remoteTx) ForPrefix(bucket string, prefix []byte, walker func(k, v []byte) error) error {
	c, err := tx.Cursor(bucket)
	if err != nil {
		return err
	}
	defer c.Close()

	for k, v, err := c.Seek(prefix); k != nil; k, v, err = c.Next() {
		if err != nil {
			return err
		}
		if !bytes.HasPrefix(k, prefix) {
			break
		}
		if err := walker(k, v); err != nil {
			return err
		}
	}
	return nil
}

func (tx *remoteTx) ForAmount(bucket string, fromPrefix []byte, amount uint32, walker func(k, v []byte) error) error {
	c, err := tx.Cursor(bucket)
	if err != nil {
		return err
	}
	defer c.Close()

	for k, v, err := c.Seek(fromPrefix); k != nil && amount > 0; k, v, err = c.Next() {
		if err != nil {
			return err
		}
		if err := walker(k, v); err != nil {
			return err
		}
		amount--
	}
	return nil
}

func (tx *remoteTx) GetOne(bucket string, key []byte) (val []byte, err error) {
	c, err := tx.statelessCursor(bucket)
	if err != nil {
		return nil, err
	}
	_, val, err = c.SeekExact(key)
	return val, err
}

func (tx *remoteTx) Has(bucket string, key []byte) (bool, error) {
	c, err := tx.statelessCursor(bucket)
	if err != nil {
		return false, err
	}
	k, _, err := c.Seek(key)
	if err != nil {
		return false, err
	}
	return bytes.Equal(key, k), nil
}

func (c *remoteCursor) SeekExact(key []byte) (k, val []byte, err error) {
	return c.seekExact(key)
}

func (c *remoteCursor) Prev() ([]byte, []byte, error) {
	return c.prev()
}

func (tx *remoteTx) Cursor(bucket string) (kv.Cursor, error) {
	b := tx.db.buckets[bucket]
	c := &remoteCursor{tx: tx, ctx: tx.ctx, bucketName: bucket, bucketCfg: b, stream: tx.stream}
	tx.cursors = append(tx.cursors, c)
	if err := c.stream.Send(&remote.Cursor{Op: remote.Op_OPEN, BucketName: c.bucketName}); err != nil {
		return nil, err
	}
	msg, err := c.stream.Recv()
	if err != nil {
		return nil, err
	}
	c.id = msg.CursorID
	return c, nil
}

func (c *remoteCursor) Put(key []byte, value []byte) error            { panic("not supported") }
func (c *remoteCursor) PutNoOverwrite(key []byte, value []byte) error { panic("not supported") }
func (c *remoteCursor) Append(key []byte, value []byte) error         { panic("not supported") }
func (c *remoteCursor) Delete(k, v []byte) error                      { panic("not supported") }
func (c *remoteCursor) DeleteCurrent() error                          { panic("not supported") }
func (c *remoteCursor) Count() (uint64, error)                        { panic("not supported") }

func (c *remoteCursor) first() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_FIRST}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}

func (c *remoteCursor) next() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_NEXT}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) nextDup() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_NEXT_DUP}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) nextNoDup() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_NEXT_NO_DUP}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) prev() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_PREV}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) prevDup() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_PREV_DUP}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) prevNoDup() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_PREV_NO_DUP}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) last() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_LAST}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) setRange(k []byte) ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_SEEK, K: k}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) seekExact(k []byte) ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_SEEK_EXACT, K: k}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) getBothRange(k, v []byte) ([]byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_SEEK_BOTH, K: k, V: v}); err != nil {
		return nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return nil, err
	}
	return pair.V, nil
}
func (c *remoteCursor) seekBothExact(k, v []byte) ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_SEEK_BOTH_EXACT, K: k, V: v}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}
func (c *remoteCursor) firstDup() ([]byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_FIRST_DUP}); err != nil {
		return nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return nil, err
	}
	return pair.V, nil
}
func (c *remoteCursor) lastDup() ([]byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_LAST_DUP}); err != nil {
		return nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return nil, err
	}
	return pair.V, nil
}
func (c *remoteCursor) getCurrent() ([]byte, []byte, error) {
	if err := c.stream.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_CURRENT}); err != nil {
		return []byte{}, nil, err
	}
	pair, err := c.stream.Recv()
	if err != nil {
		return []byte{}, nil, err
	}
	return pair.K, pair.V, nil
}

func (c *remoteCursor) Current() ([]byte, []byte, error) {
	return c.getCurrent()
}

// Seek - doesn't start streaming (because much of code does only several .Seek calls without reading sequence of data)
// .Next() - does request streaming (if configured by user)
func (c *remoteCursor) Seek(seek []byte) ([]byte, []byte, error) {
	return c.setRange(seek)
}

func (c *remoteCursor) First() ([]byte, []byte, error) {
	return c.first()
}

// Next - returns next data element from server, request streaming (if configured by user)
func (c *remoteCursor) Next() ([]byte, []byte, error) {
	return c.next()
}

func (c *remoteCursor) Last() ([]byte, []byte, error) {
	return c.last()
}

func (tx *remoteTx) closeGrpcStream() {
	if tx.stream == nil {
		return
	}
	defer tx.streamCancelFn() // hard cancel stream if graceful wasn't successful

	if tx.streamingRequested {
		// if streaming is in progress, can't use `CloseSend` - because
		// server will not read it right not - it busy with streaming data
		// TODO: set flag 'tx.streamingRequested' to false when got terminator from server (nil key or os.EOF)
		tx.streamCancelFn()
	} else {
		// try graceful close stream
		err := tx.stream.CloseSend()
		if err != nil {
			if !errors.Is(err, io.EOF) && !errors.Is(err, context.Canceled) {
				tx.db.log.Warnf("couldn't send msg CloseSend to server: %s", err)
			}
		} else {
			_, err = tx.stream.Recv()
			if err != nil && !errors.Is(err, io.EOF) && !errors.Is(err, context.Canceled) {
				tx.db.log.Warnf("received unexpected error from server after CloseSend: %s", err)
			}
		}
	}
	tx.stream = nil
	tx.streamingRequested = false
}

func (c *remoteCursor) Close() {
	if c.stream == nil {
		return
	}
	st := c.stream
	c.stream = nil
	if err := st.Send(&remote.Cursor{Cursor: c.id, Op: remote.Op_CLOSE}); err == nil {
		_, _ = st.Recv()
	}
}

func (tx *remoteTx) CursorDupSort(bucket string) (kv.CursorDupSort, error) {
	c, err := tx.Cursor(bucket)
	if err != nil {
		return nil, err
	}
	return &remoteCursorDupSort{remoteCursor: c.(*remoteCursor)}, nil
}

func (c *remoteCursorDupSort) SeekBothExact(key, value []byte) ([]byte, []byte, error) {
	return c.seekBothExact(key, value)
}

func (c *remoteCursorDupSort) SeekBothRange(key, value []byte) ([]byte, error) {
	return c.getBothRange(key, value)
}

func (c *remoteCursorDupSort) DeleteExact(k1, k2 []byte) error      { panic("not supported") }
func (c *remoteCursorDupSort) AppendDup(k []byte, v []byte) error   { panic("not supported") }
func (c *remoteCursorDupSort) PutNoDupData(key, value []byte) error { panic("not supported") }
func (c *remoteCursorDupSort) DeleteCurrentDuplicates() error       { panic("not supported") }
func (c *remoteCursorDupSort) CountDuplicates() (uint64, error)     { panic("not supported") }

func (c *remoteCursorDupSort) FirstDup() ([]byte, error) {
	return c.firstDup()
}
func (c *remoteCursorDupSort) NextDup() ([]byte, []byte, error) {
	return c.nextDup()
}
func (c *remoteCursorDupSort) NextNoDup() ([]byte, []byte, error) {
	return c.nextNoDup()
}
func (c *remoteCursorDupSort) PrevDup() ([]byte, []byte, error) {
	return c.prevDup()
}
func (c *remoteCursorDupSort) PrevNoDup() ([]byte, []byte, error) {
	return c.prevNoDup()
}
func (c *remoteCursorDupSort) LastDup() ([]byte, error) {
	return c.lastDup()
}