package notify

import (
	"time"

	flatbuffers "github.com/google/flatbuffers/go"
	"github.com/google/uuid"

	fb "scrabble/pkg/fbs/scrabblefb"
)

// The constructors below build one Intent per live event, FlatBuffers-encoding
// the payload with the shared scrabblefb schema. Keeping the encoding here lets
// the game/social/lobby services emit events without importing the wire schema.

// YourTurn announces to userID that it is their turn in game gameID, with the
// turn's nominal deadline.
func YourTurn(userID, gameID uuid.UUID, deadline time.Time) Intent {
	b := flatbuffers.NewBuilder(64)
	gid := b.CreateString(gameID.String())
	fb.YourTurnEventStart(b)
	fb.YourTurnEventAddGameId(b, gid)
	fb.YourTurnEventAddDeadlineUnix(b, deadline.Unix())
	b.Finish(fb.YourTurnEventEnd(b))
	return Intent{UserID: userID, Kind: KindYourTurn, Payload: b.FinishedBytes(), EventID: eventID()}
}

// OpponentMoved tells userID that seat just committed a move in game gameID,
// summarising it (the client refetches the full state).
func OpponentMoved(userID, gameID uuid.UUID, seat int, action string, score, total int) Intent {
	b := flatbuffers.NewBuilder(64)
	gid := b.CreateString(gameID.String())
	act := b.CreateString(action)
	fb.OpponentMovedEventStart(b)
	fb.OpponentMovedEventAddGameId(b, gid)
	fb.OpponentMovedEventAddSeat(b, int32(seat))
	fb.OpponentMovedEventAddAction(b, act)
	fb.OpponentMovedEventAddScore(b, int32(score))
	fb.OpponentMovedEventAddTotal(b, int32(total))
	b.Finish(fb.OpponentMovedEventEnd(b))
	return Intent{UserID: userID, Kind: KindOpponentMoved, Payload: b.FinishedBytes(), EventID: eventID()}
}

// ChatMessage delivers a stored chat message (or nudge) to userID.
func ChatMessage(userID, gameID, senderID uuid.UUID, id, kind, body string, createdAt time.Time) Intent {
	b := flatbuffers.NewBuilder(128)
	idOff := b.CreateString(id)
	gid := b.CreateString(gameID.String())
	sid := b.CreateString(senderID.String())
	kindOff := b.CreateString(kind)
	bodyOff := b.CreateString(body)
	fb.ChatMessageStart(b)
	fb.ChatMessageAddId(b, idOff)
	fb.ChatMessageAddGameId(b, gid)
	fb.ChatMessageAddSenderId(b, sid)
	fb.ChatMessageAddKind(b, kindOff)
	fb.ChatMessageAddBody(b, bodyOff)
	fb.ChatMessageAddCreatedAtUnix(b, createdAt.Unix())
	b.Finish(fb.ChatMessageEnd(b))
	return Intent{UserID: userID, Kind: KindChatMessage, Payload: b.FinishedBytes(), EventID: eventID()}
}

// Nudge tells userID that fromUserID nudged them in game gameID.
func Nudge(userID, gameID, fromUserID uuid.UUID) Intent {
	b := flatbuffers.NewBuilder(64)
	gid := b.CreateString(gameID.String())
	from := b.CreateString(fromUserID.String())
	fb.NudgeEventStart(b)
	fb.NudgeEventAddGameId(b, gid)
	fb.NudgeEventAddFromUserId(b, from)
	b.Finish(fb.NudgeEventEnd(b))
	return Intent{UserID: userID, Kind: KindNudge, Payload: b.FinishedBytes(), EventID: eventID()}
}

// MatchFound tells userID that game gameID, which they are seated in, has
// started (an auto-match pairing or a robot substitution).
func MatchFound(userID, gameID uuid.UUID) Intent {
	b := flatbuffers.NewBuilder(64)
	gid := b.CreateString(gameID.String())
	fb.MatchFoundEventStart(b)
	fb.MatchFoundEventAddGameId(b, gid)
	b.Finish(fb.MatchFoundEventEnd(b))
	return Intent{UserID: userID, Kind: KindMatchFound, Payload: b.FinishedBytes(), EventID: eventID()}
}

// Notification is a lightweight "re-poll" signal to userID that a friend request or
// invitation changed. kind is a sub-discriminator (NotifyFriendRequest,
// NotifyFriendAdded, NotifyInvitation, NotifyGameStarted) the client may use to
// scope its refresh.
func Notification(userID uuid.UUID, kind string) Intent {
	b := flatbuffers.NewBuilder(32)
	k := b.CreateString(kind)
	fb.NotificationEventStart(b)
	fb.NotificationEventAddKind(b, k)
	b.Finish(fb.NotificationEventEnd(b))
	return Intent{UserID: userID, Kind: KindNotification, Payload: b.FinishedBytes(), EventID: eventID()}
}

// eventID returns a best-effort correlation id for one emitted event.
func eventID() string {
	if id, err := uuid.NewV7(); err == nil {
		return id.String()
	}
	return ""
}