// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// 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 postgres

import (
	"context"
	"database/sql"
	"time"

	"github.com/lib/pq"
	"github.com/matrix-org/dendrite/internal"
	"github.com/matrix-org/dendrite/internal/sqlutil"
	"github.com/matrix-org/dendrite/keyserver/api"
	"github.com/matrix-org/dendrite/keyserver/storage/tables"
)

var deviceKeysSchema = `
-- Stores device keys for users
CREATE TABLE IF NOT EXISTS keyserver_device_keys (
    user_id TEXT NOT NULL,
	device_id TEXT NOT NULL,
	ts_added_secs BIGINT NOT NULL,
	key_json TEXT NOT NULL,
	-- the stream ID of this key, scoped per-user. This gets updated when the device key changes.
	-- This means we do not store an unbounded append-only log of device keys, which is not actually
	-- required in the spec because in the event of a missed update the server fetches the entire
	-- current set of keys rather than trying to 'fast-forward' or catchup missing stream IDs.
	stream_id BIGINT NOT NULL,
	display_name TEXT,
	-- Clobber based on tuple of user/device.
    CONSTRAINT keyserver_device_keys_unique UNIQUE (user_id, device_id)
);
`

const upsertDeviceKeysSQL = "" +
	"INSERT INTO keyserver_device_keys (user_id, device_id, ts_added_secs, key_json, stream_id, display_name)" +
	" VALUES ($1, $2, $3, $4, $5, $6)" +
	" ON CONFLICT ON CONSTRAINT keyserver_device_keys_unique" +
	" DO UPDATE SET key_json = $4, stream_id = $5, display_name = $6"

const selectDeviceKeysSQL = "" +
	"SELECT key_json, stream_id, display_name FROM keyserver_device_keys WHERE user_id=$1 AND device_id=$2"

const selectBatchDeviceKeysSQL = "" +
	"SELECT device_id, key_json, stream_id, display_name FROM keyserver_device_keys WHERE user_id=$1 AND key_json <> ''"

const selectMaxStreamForUserSQL = "" +
	"SELECT MAX(stream_id) FROM keyserver_device_keys WHERE user_id=$1"

const countStreamIDsForUserSQL = "" +
	"SELECT COUNT(*) FROM keyserver_device_keys WHERE user_id=$1 AND stream_id = ANY($2)"

const deleteAllDeviceKeysSQL = "" +
	"DELETE FROM keyserver_device_keys WHERE user_id=$1"

type deviceKeysStatements struct {
	db                         *sql.DB
	upsertDeviceKeysStmt       *sql.Stmt
	selectDeviceKeysStmt       *sql.Stmt
	selectBatchDeviceKeysStmt  *sql.Stmt
	selectMaxStreamForUserStmt *sql.Stmt
	countStreamIDsForUserStmt  *sql.Stmt
	deleteAllDeviceKeysStmt    *sql.Stmt
}

func NewPostgresDeviceKeysTable(db *sql.DB) (tables.DeviceKeys, error) {
	s := &deviceKeysStatements{
		db: db,
	}
	_, err := db.Exec(deviceKeysSchema)
	if err != nil {
		return nil, err
	}
	if s.upsertDeviceKeysStmt, err = db.Prepare(upsertDeviceKeysSQL); err != nil {
		return nil, err
	}
	if s.selectDeviceKeysStmt, err = db.Prepare(selectDeviceKeysSQL); err != nil {
		return nil, err
	}
	if s.selectBatchDeviceKeysStmt, err = db.Prepare(selectBatchDeviceKeysSQL); err != nil {
		return nil, err
	}
	if s.selectMaxStreamForUserStmt, err = db.Prepare(selectMaxStreamForUserSQL); err != nil {
		return nil, err
	}
	if s.countStreamIDsForUserStmt, err = db.Prepare(countStreamIDsForUserSQL); err != nil {
		return nil, err
	}
	if s.deleteAllDeviceKeysStmt, err = db.Prepare(deleteAllDeviceKeysSQL); err != nil {
		return nil, err
	}
	return s, nil
}

func (s *deviceKeysStatements) SelectDeviceKeysJSON(ctx context.Context, keys []api.DeviceMessage) error {
	for i, key := range keys {
		var keyJSONStr string
		var streamID int
		var displayName sql.NullString
		err := s.selectDeviceKeysStmt.QueryRowContext(ctx, key.UserID, key.DeviceID).Scan(&keyJSONStr, &streamID, &displayName)
		if err != nil && err != sql.ErrNoRows {
			return err
		}
		// this will be '' when there is no device
		keys[i].Type = api.TypeDeviceKeyUpdate
		keys[i].KeyJSON = []byte(keyJSONStr)
		keys[i].StreamID = streamID
		if displayName.Valid {
			keys[i].DisplayName = displayName.String
		}
	}
	return nil
}

func (s *deviceKeysStatements) SelectMaxStreamIDForUser(ctx context.Context, txn *sql.Tx, userID string) (streamID int32, err error) {
	// nullable if there are no results
	var nullStream sql.NullInt32
	err = sqlutil.TxStmt(txn, s.selectMaxStreamForUserStmt).QueryRowContext(ctx, userID).Scan(&nullStream)
	if err == sql.ErrNoRows {
		err = nil
	}
	if nullStream.Valid {
		streamID = nullStream.Int32
	}
	return
}

func (s *deviceKeysStatements) CountStreamIDsForUser(ctx context.Context, userID string, streamIDs []int64) (int, error) {
	// nullable if there are no results
	var count sql.NullInt32
	err := s.countStreamIDsForUserStmt.QueryRowContext(ctx, userID, pq.Int64Array(streamIDs)).Scan(&count)
	if err != nil {
		return 0, err
	}
	if count.Valid {
		return int(count.Int32), nil
	}
	return 0, nil
}

func (s *deviceKeysStatements) InsertDeviceKeys(ctx context.Context, txn *sql.Tx, keys []api.DeviceMessage) error {
	for _, key := range keys {
		now := time.Now().Unix()
		_, err := sqlutil.TxStmt(txn, s.upsertDeviceKeysStmt).ExecContext(
			ctx, key.UserID, key.DeviceID, now, string(key.KeyJSON), key.StreamID, key.DisplayName,
		)
		if err != nil {
			return err
		}
	}
	return nil
}

func (s *deviceKeysStatements) DeleteAllDeviceKeys(ctx context.Context, txn *sql.Tx, userID string) error {
	_, err := sqlutil.TxStmt(txn, s.deleteAllDeviceKeysStmt).ExecContext(ctx, userID)
	return err
}

func (s *deviceKeysStatements) SelectBatchDeviceKeys(ctx context.Context, userID string, deviceIDs []string) ([]api.DeviceMessage, error) {
	rows, err := s.selectBatchDeviceKeysStmt.QueryContext(ctx, userID)
	if err != nil {
		return nil, err
	}
	defer internal.CloseAndLogIfError(ctx, rows, "selectBatchDeviceKeysStmt: rows.close() failed")
	deviceIDMap := make(map[string]bool)
	for _, d := range deviceIDs {
		deviceIDMap[d] = true
	}
	var result []api.DeviceMessage
	for rows.Next() {
		dk := api.DeviceMessage{
			Type:       api.TypeDeviceKeyUpdate,
			DeviceKeys: &api.DeviceKeys{},
		}
		dk.UserID = userID
		var keyJSON string
		var streamID int
		var displayName sql.NullString
		if err := rows.Scan(&dk.DeviceID, &keyJSON, &streamID, &displayName); err != nil {
			return nil, err
		}
		dk.KeyJSON = []byte(keyJSON)
		dk.StreamID = streamID
		if displayName.Valid {
			dk.DisplayName = displayName.String
		}
		// include the key if we want all keys (no device) or it was asked
		if deviceIDMap[dk.DeviceID] || len(deviceIDs) == 0 {
			result = append(result, dk)
		}
	}
	return result, rows.Err()
}