package storage

import (
	"context"
	"errors"
)

// ErrNoSuchPusher is a pusher that does not exist.
var ErrNoSuchPusher = errors.New("no such pusher")

// Pusher is one place a user's notifications are pushed to: an app on a
// device, reached through its push gateway.
type Pusher struct {
	Localpart string

	// DeviceID is the session that registered the pusher, so that logging
	// the device out removes it. Empty for a pusher whose session is not
	// known.
	DeviceID string

	Kind    string
	AppID   string
	PushKey string

	AppDisplayName    string
	DeviceDisplayName string
	ProfileTag        string
	Lang              string

	// Data is the pusher's data object as the client sent it: the gateway
	// URL, the payload format, and anything else the app wants passed to
	// its gateway.
	Data []byte

	// PushKeyTSMS is when the push key was last set, which a gateway uses
	// to tell an old registration of a key from a newer one.
	PushKeyTSMS int64
}

// NewNotification is one event that notifies one user.
type NewNotification struct {
	UserID  string
	RoomID  string
	EventID string

	// EventPos is the event's position in the room event stream, which is
	// what a read receipt is compared against.
	EventPos int64

	// ThreadID is the thread the event is in: the root its m.relates_to
	// names when rel_type is m.thread, or ThreadMain for an event on the
	// main timeline. A thread root is itself on the main timeline.
	ThreadID string

	TimestampMS int64
	Highlight   bool

	// Actions are the matched rule's actions, as JSON, which GET
	// /notifications reports.
	Actions []byte
}

// Notification is a stored notification.
type Notification struct {
	NewNotification

	// ID orders a user's notifications, newest highest, and is what GET
	// /notifications pages by.
	ID int64

	Read bool
}

// Threads a read receipt can be for, as the thread argument of
// MarkNotificationsRead. Any other value is a thread root's event ID.
const (
	// ThreadMain is the main timeline: the thread ID of an event in no
	// thread, and what a receipt with thread_id "main" reads.
	ThreadMain = ""

	// AllThreads is an unthreaded receipt, which reads the main timeline
	// and every thread together. It cannot be mistaken for a thread root:
	// an event ID starts with '$'.
	AllThreads = "*"
)

// NotificationCounts is a room's unread notifications for one user.
type NotificationCounts struct {
	Notifications int
	Highlights    int
}

// PushStore persists pushers and the notifications push rules produce.
//
// Notification counts are a stream of their own: every write that changes
// a user's counts in a room stamps the room with a new position, inside
// the transaction that changes them, so that an incremental sync can ask
// which rooms' counts moved since its token. A count moves without an
// event — a read receipt sent from another device sets it back to zero —
// and a sync that only looked at events would go on showing the old one.
type PushStore interface {
	// Pushers lists a user's pushers.
	Pushers(ctx context.Context, localpart string) ([]Pusher, error)

	// SetPusher creates or replaces the user's pusher with the same app ID
	// and push key. Unless appendOthers is set, any other user's pusher
	// with the same app ID and push key is removed: a push key names a
	// device, and the device is now this user's.
	SetPusher(ctx context.Context, p Pusher, appendOthers bool) error

	// DeletePusher removes one of a user's pushers. Removing one that is
	// not there is not an error.
	DeletePusher(ctx context.Context, localpart, appID, pushKey string) error

	// DeletePushersForDevices removes the pushers registered by the given
	// sessions, or by every session of the user when deviceIDs is empty.
	DeletePushersForDevices(ctx context.Context, localpart string, deviceIDs []string) error

	// AddNotifications records notifications and moves the counts of
	// each (user, room) they are for, returning the position the last
	// count moved to.
	AddNotifications(ctx context.Context, ns []NewNotification) (int64, error)

	// MarkNotificationsRead marks a user's notifications in a room up to
	// and including an event position as read, and reports whether the
	// counts moved. thread limits it to one thread — ThreadMain for the
	// main timeline, a root's event ID for a thread — or is AllThreads.
	MarkNotificationsRead(ctx context.Context, userID, roomID, thread string, upTo int64) (pos int64, moved bool, err error)

	// NotificationCounts reads a user's unread counts in the given rooms.
	// A room with nothing unread is in the result with zero counts.
	NotificationCounts(ctx context.Context, userID string, roomIDs []string) (map[string]NotificationCounts, error)

	// ThreadNotificationCounts reads a user's unread counts in the given
	// rooms one thread at a time, keyed by room and then by thread ID, with
	// the main timeline under ThreadMain. Only threads with something
	// unread are in the result. The room's move in the notification stream
	// covers its threads: any change to a thread's counts is a change to
	// the room's.
	ThreadNotificationCounts(ctx context.Context, userID string, roomIDs []string) (map[string]map[string]NotificationCounts, error)

	// NotificationCountChanges lists the rooms whose counts for a user
	// moved after from and at or before to.
	NotificationCountChanges(ctx context.Context, userID string, from, to int64) ([]string, error)

	// UnreadNotifications is a user's unread notifications across every
	// room, which a push tells the device to show as its badge.
	UnreadNotifications(ctx context.Context, userID string) (int, error)

	// Notifications pages through a user's notifications, newest first,
	// starting below the ID before (0 for the newest).
	Notifications(ctx context.Context, userID string, before int64, limit int, onlyHighlight bool) ([]Notification, error)

	// PruneNotifications removes read notifications older than a time,
	// returning how many went.
	PruneNotifications(ctx context.Context, beforeMS int64) (int64, error)
}