package state

import (
	"database/sql"
	"encoding/json"
	"github.com/lib/pq"

	"github.com/jmoiron/sqlx"
)

// InvitesTable stores invites for each user.
// Originally, invites were stored with the main events in a room. We ignored stripped state and
// just kept the m.room.member invite event. This had many problems though:
//   - The room would be initialised by the invite event, causing the room to not populate with state
//     correctly when the user joined the room.
//   - The user could read room data in the room without being joined to the room e.g could pull
//     `required_state` and `timeline` as they would be authorised by the invite to see this data.
//
// Instead, we now completely split out invites from the normal event flow. This fixes the issues
// outlined above but introduce more problems:
//   - How do you sort the invite with rooms?
//   - How do you calculate the room name when you lack heroes?
//
// For now, we say that invites:
//   - are treated as a highlightable event for the purposes of sorting by highlight count.
//   - are given the timestamp of when the invite arrived.
//   - calculate the room name on a best-effort basis given the lack of heroes (same as element-web).
//
// When an invite is rejected, it appears in the `leave` section which then causes the invite to be
// removed from this table.
type InvitesTable struct {
	db *sqlx.DB
}

func NewInvitesTable(db *sqlx.DB) *InvitesTable {
	// make sure tables are made
	db.MustExec(`
	CREATE TABLE IF NOT EXISTS syncv3_invites (
		room_id TEXT NOT NULL,
		user_id TEXT NOT NULL,
		-- JSON array. The contents of 'rooms.invite.$room_id.invite_state.events'
		invite_state BYTEA NOT NULL,
		UNIQUE(user_id, room_id)
	);
	`)
	return &InvitesTable{db}
}

func (t *InvitesTable) RemoveInvite(userID, roomID string) error {
	_, err := t.db.Exec(`DELETE FROM syncv3_invites WHERE user_id = $1 AND room_id = $2`, userID, roomID)
	return err
}

// RemoveSupersededInvites accepts a list of events in the given room. The events should
// either
//   - contain at most one membership event per user, or else
//   - be in timeline order (most recent last)
//
// (corresponding to an Accumulate and an Initialise call, respectively).
//
// The events are scanned in order for membership changes, to determine the "final"
// memberships. Users who final membership is not "invite" have their outstanding
// invites to this room deleted.
func (t *InvitesTable) RemoveSupersededInvites(txn *sqlx.Tx, roomID string, newEvents []Event) error {
	memberships := map[string]string{} // user ID -> memberships
	for _, ev := range newEvents {
		if ev.Type != "m.room.member" {
			continue
		}
		memberships[ev.StateKey] = ev.Membership
	}

	var usersToRemove []string
	for userID, membership := range memberships {
		if membership != "invite" && membership != "_invite" {
			usersToRemove = append(usersToRemove, userID)
		}
	}

	if len(usersToRemove) == 0 {
		return nil
	}

	_, err := txn.Exec(`
		DELETE FROM syncv3_invites
		WHERE user_id = ANY($1) AND room_id = $2
	`, pq.StringArray(usersToRemove), roomID)

	return err
}

func (t *InvitesTable) InsertInvite(userID, roomID string, inviteRoomState []json.RawMessage) error {
	blob, err := json.Marshal(inviteRoomState)
	if err != nil {
		return err
	}
	_, err = t.db.Exec(
		`INSERT INTO syncv3_invites(user_id, room_id, invite_state) VALUES($1,$2,$3)
		ON CONFLICT (user_id, room_id) DO UPDATE SET invite_state = $3`,
		userID, roomID, blob,
	)
	return err
}

func (t *InvitesTable) SelectInviteState(userID, roomID string) (inviteState []json.RawMessage, err error) {
	var blob json.RawMessage
	if err := t.db.QueryRow(`SELECT invite_state FROM syncv3_invites WHERE user_id=$1 AND room_id=$2`, userID, roomID).Scan(&blob); err != nil && err != sql.ErrNoRows {
		return nil, err
	}
	if blob == nil {
		return
	}
	if err := json.Unmarshal(blob, &inviteState); err != nil {
		return nil, err
	}
	return inviteState, nil
}

// Select all invites for this user. Returns a map of room ID to invite_state (json array).
func (t *InvitesTable) SelectAllInvitesForUser(userID string) (map[string][]json.RawMessage, error) {
	rows, err := t.db.Query(`SELECT room_id, invite_state FROM syncv3_invites WHERE user_id = $1`, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	result := make(map[string][]json.RawMessage)
	var roomID string
	var blob json.RawMessage
	for rows.Next() {
		if err := rows.Scan(&roomID, &blob); err != nil {
			return nil, err
		}
		var inviteState []json.RawMessage
		if err := json.Unmarshal(blob, &inviteState); err != nil {
			return nil, err
		}
		result[roomID] = inviteState
	}
	return result, nil
}