package shared

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

	"github.com/matrix-org/dendrite/internal"
	"github.com/matrix-org/dendrite/roomserver/api"
	"github.com/matrix-org/dendrite/roomserver/storage/tables"
	"github.com/matrix-org/dendrite/roomserver/types"
	"github.com/matrix-org/gomatrixserverlib"
)

type Database struct {
	DB                  *sql.DB
	EventsTable         tables.Events
	EventJSONTable      tables.EventJSON
	EventTypesTable     tables.EventTypes
	EventStateKeysTable tables.EventStateKeys
	RoomsTable          tables.Rooms
	TransactionsTable   tables.Transactions
}

// EventTypeNIDs implements state.RoomStateDatabase
func (d *Database) EventTypeNIDs(
	ctx context.Context, eventTypes []string,
) (map[string]types.EventTypeNID, error) {
	return d.EventTypesTable.BulkSelectEventTypeNID(ctx, eventTypes)
}

// EventStateKeys implements query.RoomserverQueryAPIDatabase
func (d *Database) EventStateKeys(
	ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID,
) (map[types.EventStateKeyNID]string, error) {
	return d.EventStateKeysTable.BulkSelectEventStateKey(ctx, eventStateKeyNIDs)
}

// EventStateKeyNIDs implements state.RoomStateDatabase
func (d *Database) EventStateKeyNIDs(
	ctx context.Context, eventStateKeys []string,
) (map[string]types.EventStateKeyNID, error) {
	return d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, eventStateKeys)
}

// StateEntriesForEventIDs implements input.EventDatabase
func (d *Database) StateEntriesForEventIDs(
	ctx context.Context, eventIDs []string,
) ([]types.StateEntry, error) {
	return d.EventsTable.BulkSelectStateEventByID(ctx, eventIDs)
}

// EventNIDs implements query.RoomserverQueryAPIDatabase
func (d *Database) EventNIDs(
	ctx context.Context, eventIDs []string,
) (map[string]types.EventNID, error) {
	return d.EventsTable.BulkSelectEventNID(ctx, eventIDs)
}

// SetState implements input.EventDatabase
func (d *Database) SetState(
	ctx context.Context, eventNID types.EventNID, stateNID types.StateSnapshotNID,
) error {
	return d.EventsTable.UpdateEventState(ctx, eventNID, stateNID)
}

// StateAtEventIDs implements input.EventDatabase
func (d *Database) StateAtEventIDs(
	ctx context.Context, eventIDs []string,
) ([]types.StateAtEvent, error) {
	return d.EventsTable.BulkSelectStateAtEventByID(ctx, eventIDs)
}

// SnapshotNIDFromEventID implements state.RoomStateDatabase
func (d *Database) SnapshotNIDFromEventID(
	ctx context.Context, eventID string,
) (types.StateSnapshotNID, error) {
	_, stateNID, err := d.EventsTable.SelectEvent(ctx, nil, eventID)
	return stateNID, err
}

// EventIDs implements input.RoomEventDatabase
func (d *Database) EventIDs(
	ctx context.Context, eventNIDs []types.EventNID,
) (map[types.EventNID]string, error) {
	return d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
}

// EventsFromIDs implements query.RoomserverQueryAPIEventDB
func (d *Database) EventsFromIDs(ctx context.Context, eventIDs []string) ([]types.Event, error) {
	nidMap, err := d.EventNIDs(ctx, eventIDs)
	if err != nil {
		return nil, err
	}

	var nids []types.EventNID
	for _, nid := range nidMap {
		nids = append(nids, nid)
	}

	return d.Events(ctx, nids)
}

// RoomNID implements query.RoomserverQueryAPIDB
func (d *Database) RoomNID(ctx context.Context, roomID string) (types.RoomNID, error) {
	roomNID, err := d.RoomsTable.SelectRoomNID(ctx, nil, roomID)
	if err == sql.ErrNoRows {
		return 0, nil
	}
	return roomNID, err
}

// RoomNIDExcludingStubs implements query.RoomserverQueryAPIDB
func (d *Database) RoomNIDExcludingStubs(ctx context.Context, roomID string) (roomNID types.RoomNID, err error) {
	roomNID, err = d.RoomNID(ctx, roomID)
	if err != nil {
		return
	}
	latestEvents, _, err := d.RoomsTable.SelectLatestEventNIDs(ctx, nil, roomNID)
	if err != nil {
		return
	}
	if len(latestEvents) == 0 {
		roomNID = 0
		return
	}
	return
}

// LatestEventIDs implements query.RoomserverQueryAPIDatabase
func (d *Database) LatestEventIDs(
	ctx context.Context, roomNID types.RoomNID,
) (references []gomatrixserverlib.EventReference, currentStateSnapshotNID types.StateSnapshotNID, depth int64, err error) {
	err = internal.WithTransaction(d.DB, func(txn *sql.Tx) error {
		var eventNIDs []types.EventNID
		eventNIDs, currentStateSnapshotNID, err = d.RoomsTable.SelectLatestEventNIDs(ctx, txn, roomNID)
		if err != nil {
			return err
		}
		references, err = d.EventsTable.BulkSelectEventReference(ctx, txn, eventNIDs)
		if err != nil {
			return err
		}
		depth, err = d.EventsTable.SelectMaxEventDepth(ctx, txn, eventNIDs)
		if err != nil {
			return err
		}
		return nil
	})
	return
}

func (d *Database) GetRoomVersionForRoom(
	ctx context.Context, roomID string,
) (gomatrixserverlib.RoomVersion, error) {
	return d.RoomsTable.SelectRoomVersionForRoomID(
		ctx, nil, roomID,
	)
}

func (d *Database) GetRoomVersionForRoomNID(
	ctx context.Context, roomNID types.RoomNID,
) (gomatrixserverlib.RoomVersion, error) {
	return d.RoomsTable.SelectRoomVersionForRoomNID(
		ctx, roomNID,
	)
}

// Events implements input.EventDatabase
func (d *Database) Events(
	ctx context.Context, eventNIDs []types.EventNID,
) ([]types.Event, error) {
	eventJSONs, err := d.EventJSONTable.BulkSelectEventJSON(ctx, eventNIDs)
	if err != nil {
		return nil, err
	}
	results := make([]types.Event, len(eventJSONs))
	for i, eventJSON := range eventJSONs {
		var roomNID types.RoomNID
		var roomVersion gomatrixserverlib.RoomVersion
		result := &results[i]
		result.EventNID = eventJSON.EventNID
		roomNID, err = d.EventsTable.SelectRoomNIDForEventNID(ctx, eventJSON.EventNID)
		if err != nil {
			return nil, err
		}
		roomVersion, err = d.RoomsTable.SelectRoomVersionForRoomNID(ctx, roomNID)
		if err != nil {
			return nil, err
		}
		result.Event, err = gomatrixserverlib.NewEventFromTrustedJSON(
			eventJSON.EventJSON, false, roomVersion,
		)
		if err != nil {
			return nil, err
		}
	}
	return results, nil
}

// GetTransactionEventID implements input.EventDatabase
func (d *Database) GetTransactionEventID(
	ctx context.Context, transactionID string,
	sessionID int64, userID string,
) (string, error) {
	eventID, err := d.TransactionsTable.SelectTransactionEventID(ctx, transactionID, sessionID, userID)
	if err == sql.ErrNoRows {
		return "", nil
	}
	return eventID, err
}

// StoreEvent implements input.EventDatabase
func (d *Database) StoreEvent(
	ctx context.Context, event gomatrixserverlib.Event,
	txnAndSessionID *api.TransactionID, authEventNIDs []types.EventNID,
) (types.RoomNID, types.StateAtEvent, error) {
	var (
		roomNID          types.RoomNID
		eventTypeNID     types.EventTypeNID
		eventStateKeyNID types.EventStateKeyNID
		eventNID         types.EventNID
		stateNID         types.StateSnapshotNID
		err              error
	)

	err = internal.WithTransaction(d.DB, func(txn *sql.Tx) error {
		if txnAndSessionID != nil {
			if err = d.TransactionsTable.InsertTransaction(
				ctx, txn, txnAndSessionID.TransactionID,
				txnAndSessionID.SessionID, event.Sender(), event.EventID(),
			); err != nil {
				return err
			}
		}

		// TODO: Here we should aim to have two different code paths for new rooms
		// vs existing ones.

		// Get the default room version. If the client doesn't supply a room_version
		// then we will use our configured default to create the room.
		// https://matrix.org/docs/spec/client_server/r0.6.0#post-matrix-client-r0-createroom
		// Note that the below logic depends on the m.room.create event being the
		// first event that is persisted to the database when creating or joining a
		// room.
		var roomVersion gomatrixserverlib.RoomVersion
		if roomVersion, err = extractRoomVersionFromCreateEvent(event); err != nil {
			return err
		}

		if roomNID, err = d.assignRoomNID(ctx, txn, event.RoomID(), roomVersion); err != nil {
			return err
		}

		if eventTypeNID, err = d.assignEventTypeNID(ctx, txn, event.Type()); err != nil {
			return err
		}

		eventStateKey := event.StateKey()
		// Assigned a numeric ID for the state_key if there is one present.
		// Otherwise set the numeric ID for the state_key to 0.
		if eventStateKey != nil {
			if eventStateKeyNID, err = d.assignStateKeyNID(ctx, txn, *eventStateKey); err != nil {
				return err
			}
		}

		if eventNID, stateNID, err = d.EventsTable.InsertEvent(
			ctx,
			txn,
			roomNID,
			eventTypeNID,
			eventStateKeyNID,
			event.EventID(),
			event.EventReference().EventSHA256,
			authEventNIDs,
			event.Depth(),
		); err != nil {
			if err == sql.ErrNoRows {
				// We've already inserted the event so select the numeric event ID
				eventNID, stateNID, err = d.EventsTable.SelectEvent(ctx, txn, event.EventID())
			}
			if err != nil {
				return err
			}
		}

		if err = d.EventJSONTable.InsertEventJSON(ctx, txn, eventNID, event.JSON()); err != nil {
			return err
		}

		return nil
	})
	if err != nil {
		return 0, types.StateAtEvent{}, err
	}

	return roomNID, types.StateAtEvent{
		BeforeStateSnapshotNID: stateNID,
		StateEntry: types.StateEntry{
			StateKeyTuple: types.StateKeyTuple{
				EventTypeNID:     eventTypeNID,
				EventStateKeyNID: eventStateKeyNID,
			},
			EventNID: eventNID,
		},
	}, nil
}

func (d *Database) assignRoomNID(
	ctx context.Context, txn *sql.Tx,
	roomID string, roomVersion gomatrixserverlib.RoomVersion,
) (types.RoomNID, error) {
	// Check if we already have a numeric ID in the database.
	roomNID, err := d.RoomsTable.SelectRoomNID(ctx, txn, roomID)
	if err == sql.ErrNoRows {
		// We don't have a numeric ID so insert one into the database.
		roomNID, err = d.RoomsTable.InsertRoomNID(ctx, txn, roomID, roomVersion)
		if err == sql.ErrNoRows {
			// We raced with another insert so run the select again.
			roomNID, err = d.RoomsTable.SelectRoomNID(ctx, txn, roomID)
		}
	}
	return roomNID, err
}

func (d *Database) assignEventTypeNID(
	ctx context.Context, txn *sql.Tx, eventType string,
) (eventTypeNID types.EventTypeNID, err error) {
	// Check if we already have a numeric ID in the database.
	eventTypeNID, err = d.EventTypesTable.SelectEventTypeNID(ctx, txn, eventType)
	if err == sql.ErrNoRows {
		// We don't have a numeric ID so insert one into the database.
		eventTypeNID, err = d.EventTypesTable.InsertEventTypeNID(ctx, txn, eventType)
		if err == sql.ErrNoRows {
			// We raced with another insert so run the select again.
			eventTypeNID, err = d.EventTypesTable.SelectEventTypeNID(ctx, txn, eventType)
		}
	}
	return
}

func (d *Database) assignStateKeyNID(
	ctx context.Context, txn *sql.Tx, eventStateKey string,
) (types.EventStateKeyNID, error) {
	// Check if we already have a numeric ID in the database.
	eventStateKeyNID, err := d.EventStateKeysTable.SelectEventStateKeyNID(ctx, txn, eventStateKey)
	if err == sql.ErrNoRows {
		// We don't have a numeric ID so insert one into the database.
		eventStateKeyNID, err = d.EventStateKeysTable.InsertEventStateKeyNID(ctx, txn, eventStateKey)
		if err == sql.ErrNoRows {
			// We raced with another insert so run the select again.
			eventStateKeyNID, err = d.EventStateKeysTable.SelectEventStateKeyNID(ctx, txn, eventStateKey)
		}
	}
	return eventStateKeyNID, err
}

func extractRoomVersionFromCreateEvent(event gomatrixserverlib.Event) (
	gomatrixserverlib.RoomVersion, error,
) {
	var err error
	var roomVersion gomatrixserverlib.RoomVersion
	// Look for m.room.create events.
	if event.Type() != gomatrixserverlib.MRoomCreate {
		return gomatrixserverlib.RoomVersion(""), nil
	}
	roomVersion = gomatrixserverlib.RoomVersionV1
	var createContent gomatrixserverlib.CreateContent
	// The m.room.create event contains an optional "room_version" key in
	// the event content, so we need to unmarshal that first.
	if err = json.Unmarshal(event.Content(), &createContent); err != nil {
		return gomatrixserverlib.RoomVersion(""), err
	}
	// A room version was specified in the event content?
	if createContent.RoomVersion != nil {
		roomVersion = gomatrixserverlib.RoomVersion(*createContent.RoomVersion)
	}
	return roomVersion, err
}