// Copyright 2017-2018 New Vector Ltd
// Copyright 2019-2020 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 sqlite3

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"

	"github.com/matrix-org/dendrite/internal"
	"github.com/matrix-org/dendrite/internal/sqlutil"
	"github.com/matrix-org/dendrite/syncapi/storage/tables"
	"github.com/matrix-org/dendrite/syncapi/types"
	"github.com/matrix-org/gomatrixserverlib"
)

const currentRoomStateSchema = `
-- Stores the current room state for every room.
CREATE TABLE IF NOT EXISTS syncapi_current_room_state (
    room_id TEXT NOT NULL,
    event_id TEXT NOT NULL,
    type TEXT NOT NULL,
    sender TEXT NOT NULL,
    contains_url BOOL NOT NULL DEFAULT false,
    state_key TEXT NOT NULL,
    headered_event_json TEXT NOT NULL,
    membership TEXT,
    added_at BIGINT,
    UNIQUE (room_id, type, state_key)
);
-- for event deletion
CREATE UNIQUE INDEX IF NOT EXISTS syncapi_event_id_idx ON syncapi_current_room_state(event_id, room_id, type, sender, contains_url);
-- for querying membership states of users
-- CREATE INDEX IF NOT EXISTS syncapi_membership_idx ON syncapi_current_room_state(type, state_key, membership) WHERE membership IS NOT NULL AND membership != 'leave';
-- for querying state by event IDs
CREATE UNIQUE INDEX IF NOT EXISTS syncapi_current_room_state_eventid_idx ON syncapi_current_room_state(event_id);
`

const upsertRoomStateSQL = "" +
	"INSERT INTO syncapi_current_room_state (room_id, event_id, type, sender, contains_url, state_key, headered_event_json, membership, added_at)" +
	" VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)" +
	" ON CONFLICT (room_id, type, state_key)" +
	" DO UPDATE SET event_id = $2, sender=$4, contains_url=$5, headered_event_json = $7, membership = $8, added_at = $9"

const deleteRoomStateByEventIDSQL = "" +
	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"

const DeleteRoomStateForRoomSQL = "" +
	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"

const selectRoomIDsWithMembershipSQL = "" +
	"SELECT DISTINCT room_id FROM syncapi_current_room_state WHERE type = 'm.room.member' AND state_key = $1 AND membership = $2"

const selectCurrentStateSQL = "" +
	"SELECT event_id, headered_event_json FROM syncapi_current_room_state WHERE room_id = $1"

// WHEN, ORDER BY and LIMIT will be added by prepareWithFilter

const selectJoinedUsersSQL = "" +
	"SELECT room_id, state_key FROM syncapi_current_room_state WHERE type = 'm.room.member' AND membership = 'join'"

const selectStateEventSQL = "" +
	"SELECT headered_event_json FROM syncapi_current_room_state WHERE room_id = $1 AND type = $2 AND state_key = $3"

const selectEventsWithEventIDsSQL = "" +
	// TODO: The session_id and transaction_id blanks are here because otherwise
	// the rowsToStreamEvents expects there to be exactly six columns. We need to
	// figure out if these really need to be in the DB, and if so, we need a
	// better permanent fix for this. - neilalexander, 2 Jan 2020
	"SELECT event_id, added_at, headered_event_json, 0 AS session_id, false AS exclude_from_sync, '' AS transaction_id" +
	" FROM syncapi_current_room_state WHERE event_id IN ($1)"

type currentRoomStateStatements struct {
	db                              *sql.DB
	streamIDStatements              *streamIDStatements
	upsertRoomStateStmt             *sql.Stmt
	deleteRoomStateByEventIDStmt    *sql.Stmt
	DeleteRoomStateForRoomStmt      *sql.Stmt
	selectRoomIDsWithMembershipStmt *sql.Stmt
	selectJoinedUsersStmt           *sql.Stmt
	selectStateEventStmt            *sql.Stmt
}

func NewSqliteCurrentRoomStateTable(db *sql.DB, streamID *streamIDStatements) (tables.CurrentRoomState, error) {
	s := &currentRoomStateStatements{
		db:                 db,
		streamIDStatements: streamID,
	}
	_, err := db.Exec(currentRoomStateSchema)
	if err != nil {
		return nil, err
	}
	if s.upsertRoomStateStmt, err = db.Prepare(upsertRoomStateSQL); err != nil {
		return nil, err
	}
	if s.deleteRoomStateByEventIDStmt, err = db.Prepare(deleteRoomStateByEventIDSQL); err != nil {
		return nil, err
	}
	if s.DeleteRoomStateForRoomStmt, err = db.Prepare(DeleteRoomStateForRoomSQL); err != nil {
		return nil, err
	}
	if s.selectRoomIDsWithMembershipStmt, err = db.Prepare(selectRoomIDsWithMembershipSQL); err != nil {
		return nil, err
	}
	if s.selectJoinedUsersStmt, err = db.Prepare(selectJoinedUsersSQL); err != nil {
		return nil, err
	}
	if s.selectStateEventStmt, err = db.Prepare(selectStateEventSQL); err != nil {
		return nil, err
	}
	return s, nil
}

// JoinedMemberLists returns a map of room ID to a list of joined user IDs.
func (s *currentRoomStateStatements) SelectJoinedUsers(
	ctx context.Context,
) (map[string][]string, error) {
	rows, err := s.selectJoinedUsersStmt.QueryContext(ctx)
	if err != nil {
		return nil, err
	}
	defer internal.CloseAndLogIfError(ctx, rows, "selectJoinedUsers: rows.close() failed")

	result := make(map[string][]string)
	for rows.Next() {
		var roomID string
		var userID string
		if err := rows.Scan(&roomID, &userID); err != nil {
			return nil, err
		}
		users := result[roomID]
		users = append(users, userID)
		result[roomID] = users
	}
	return result, nil
}

// SelectRoomIDsWithMembership returns the list of room IDs which have the given user in the given membership state.
func (s *currentRoomStateStatements) SelectRoomIDsWithMembership(
	ctx context.Context,
	txn *sql.Tx,
	userID string,
	membership string, // nolint: unparam
) ([]string, error) {
	stmt := sqlutil.TxStmt(txn, s.selectRoomIDsWithMembershipStmt)
	rows, err := stmt.QueryContext(ctx, userID, membership)
	if err != nil {
		return nil, err
	}
	defer internal.CloseAndLogIfError(ctx, rows, "selectRoomIDsWithMembership: rows.close() failed")

	var result []string
	for rows.Next() {
		var roomID string
		if err := rows.Scan(&roomID); err != nil {
			return nil, err
		}
		result = append(result, roomID)
	}
	return result, nil
}

// CurrentState returns all the current state events for the given room.
func (s *currentRoomStateStatements) SelectCurrentState(
	ctx context.Context, txn *sql.Tx, roomID string,
	stateFilter *gomatrixserverlib.StateFilter,
	excludeEventIDs []string,
) ([]*gomatrixserverlib.HeaderedEvent, error) {
	stmt, params, err := prepareWithFilters(
		s.db, txn, selectCurrentStateSQL,
		[]interface{}{
			roomID,
		},
		stateFilter.Senders, stateFilter.NotSenders,
		stateFilter.Types, stateFilter.NotTypes,
		excludeEventIDs, stateFilter.Limit, FilterOrderNone,
	)
	if err != nil {
		return nil, fmt.Errorf("s.prepareWithFilters: %w", err)
	}

	rows, err := stmt.QueryContext(ctx, params...)
	if err != nil {
		return nil, err
	}
	defer internal.CloseAndLogIfError(ctx, rows, "selectCurrentState: rows.close() failed")

	return rowsToEvents(rows)
}

func (s *currentRoomStateStatements) DeleteRoomStateByEventID(
	ctx context.Context, txn *sql.Tx, eventID string,
) error {
	stmt := sqlutil.TxStmt(txn, s.deleteRoomStateByEventIDStmt)
	_, err := stmt.ExecContext(ctx, eventID)
	return err
}

func (s *currentRoomStateStatements) DeleteRoomStateForRoom(
	ctx context.Context, txn *sql.Tx, roomID string,
) error {
	stmt := sqlutil.TxStmt(txn, s.DeleteRoomStateForRoomStmt)
	_, err := stmt.ExecContext(ctx, roomID)
	return err
}

func (s *currentRoomStateStatements) UpsertRoomState(
	ctx context.Context, txn *sql.Tx,
	event *gomatrixserverlib.HeaderedEvent, membership *string, addedAt types.StreamPosition,
) error {
	// Parse content as JSON and search for an "url" key
	containsURL := false
	var content map[string]interface{}
	if json.Unmarshal(event.Content(), &content) != nil {
		// Set containsURL to true if url is present
		_, containsURL = content["url"]
	}

	headeredJSON, err := json.Marshal(event)
	if err != nil {
		return err
	}

	// upsert state event
	stmt := sqlutil.TxStmt(txn, s.upsertRoomStateStmt)
	_, err = stmt.ExecContext(
		ctx,
		event.RoomID(),
		event.EventID(),
		event.Type(),
		event.Sender(),
		containsURL,
		*event.StateKey(),
		headeredJSON,
		membership,
		addedAt,
	)
	return err
}

func minOfInts(a, b int) int {
	if a <= b {
		return a
	}
	return b
}

func (s *currentRoomStateStatements) SelectEventsWithEventIDs(
	ctx context.Context, txn *sql.Tx, eventIDs []string,
) ([]types.StreamEvent, error) {
	iEventIDs := make([]interface{}, len(eventIDs))
	for k, v := range eventIDs {
		iEventIDs[k] = v
	}
	res := make([]types.StreamEvent, 0, len(eventIDs))
	var start int
	for start < len(eventIDs) {
		n := minOfInts(len(eventIDs)-start, 999)
		query := strings.Replace(selectEventsWithEventIDsSQL, "($1)", sqlutil.QueryVariadic(n), 1)
		rows, err := txn.QueryContext(ctx, query, iEventIDs[start:start+n]...)
		if err != nil {
			return nil, err
		}
		start = start + n
		events, err := rowsToStreamEvents(rows)
		internal.CloseAndLogIfError(ctx, rows, "selectEventsWithEventIDs: rows.close() failed")
		if err != nil {
			return nil, err
		}
		res = append(res, events...)
	}
	return res, nil
}

func rowsToEvents(rows *sql.Rows) ([]*gomatrixserverlib.HeaderedEvent, error) {
	result := []*gomatrixserverlib.HeaderedEvent{}
	for rows.Next() {
		var eventID string
		var eventBytes []byte
		if err := rows.Scan(&eventID, &eventBytes); err != nil {
			return nil, err
		}
		// TODO: Handle redacted events
		var ev gomatrixserverlib.HeaderedEvent
		if err := ev.UnmarshalJSONWithEventID(eventBytes, eventID); err != nil {
			return nil, err
		}
		result = append(result, &ev)
	}
	return result, nil
}

func (s *currentRoomStateStatements) SelectStateEvent(
	ctx context.Context, roomID, evType, stateKey string,
) (*gomatrixserverlib.HeaderedEvent, error) {
	stmt := s.selectStateEventStmt
	var res []byte
	err := stmt.QueryRowContext(ctx, roomID, evType, stateKey).Scan(&res)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	var ev gomatrixserverlib.HeaderedEvent
	if err = json.Unmarshal(res, &ev); err != nil {
		return nil, err
	}
	return &ev, err
}
