scrabble-game/backend/internal/notify/encode.go

package notify

import (
	flatbuffers "github.com/google/flatbuffers/go"

	"scrabble/backend/internal/engine"
	fb "scrabble/pkg/fbs/scrabblefb"
)

// The builders below encode the nested wire tables embedded in enriched event
// payloads (R4). They mirror the gateway's transcode encoders, but read the domain's
// already-resolved values (notify.* input structs and the decoded engine.MoveRecord)
// rather than the gateway's REST DTOs. Each returns the offset of the table it built;
// callers must build every nested table before opening the parent event table.

// buildGameView builds a GameView table from a GameSummary and returns its offset.
func buildGameView(b *flatbuffers.Builder, g GameSummary) flatbuffers.UOffsetT {
	seatOffs := make([]flatbuffers.UOffsetT, len(g.Seats))
	for i, s := range g.Seats {
		aid := b.CreateString(s.AccountID)
		dname := b.CreateString(s.DisplayName)
		fb.SeatViewStart(b)
		fb.SeatViewAddSeat(b, int32(s.Seat))
		fb.SeatViewAddAccountId(b, aid)
		fb.SeatViewAddScore(b, int32(s.Score))
		fb.SeatViewAddHintsUsed(b, int32(s.HintsUsed))
		fb.SeatViewAddIsWinner(b, s.IsWinner)
		fb.SeatViewAddDisplayName(b, dname)
		seatOffs[i] = fb.SeatViewEnd(b)
	}
	fb.GameViewStartSeatsVector(b, len(seatOffs))
	for i := len(seatOffs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(seatOffs[i])
	}
	seats := b.EndVector(len(seatOffs))

	id := b.CreateString(g.ID)
	variant := b.CreateString(g.Variant)
	dictVer := b.CreateString(g.DictVersion)
	status := b.CreateString(g.Status)
	endReason := b.CreateString(g.EndReason)

	fb.GameViewStart(b)
	fb.GameViewAddId(b, id)
	fb.GameViewAddVariant(b, variant)
	fb.GameViewAddDictVersion(b, dictVer)
	fb.GameViewAddStatus(b, status)
	fb.GameViewAddPlayers(b, int32(g.Players))
	fb.GameViewAddToMove(b, int32(g.ToMove))
	fb.GameViewAddTurnTimeoutSecs(b, int32(g.TurnTimeoutSecs))
	fb.GameViewAddMoveCount(b, int32(g.MoveCount))
	fb.GameViewAddEndReason(b, endReason)
	fb.GameViewAddSeats(b, seats)
	fb.GameViewAddLastActivityUnix(b, g.LastActivityUnix)
	return fb.GameViewEnd(b)
}

// buildMoveRecord builds a MoveRecord table from a decoded engine move and returns
// its offset. The values match the move-result DTO (Count is the engine count: the
// number of tiles swapped on an exchange, zero otherwise).
func buildMoveRecord(b *flatbuffers.Builder, m engine.MoveRecord) flatbuffers.UOffsetT {
	tileOffs := make([]flatbuffers.UOffsetT, len(m.Tiles))
	for i, t := range m.Tiles {
		letter := b.CreateString(t.Letter)
		fb.TileRecordStart(b)
		fb.TileRecordAddRow(b, int32(t.Row))
		fb.TileRecordAddCol(b, int32(t.Col))
		fb.TileRecordAddLetter(b, letter)
		fb.TileRecordAddBlank(b, t.Blank)
		tileOffs[i] = fb.TileRecordEnd(b)
	}
	fb.MoveRecordStartTilesVector(b, len(tileOffs))
	for i := len(tileOffs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(tileOffs[i])
	}
	tiles := b.EndVector(len(tileOffs))

	wordOffs := make([]flatbuffers.UOffsetT, len(m.Words))
	for i, w := range m.Words {
		wordOffs[i] = b.CreateString(w)
	}
	fb.MoveRecordStartWordsVector(b, len(wordOffs))
	for i := len(wordOffs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(wordOffs[i])
	}
	words := b.EndVector(len(wordOffs))

	action := b.CreateString(m.Action.String())
	dir := b.CreateString(m.Dir.String())
	fb.MoveRecordStart(b)
	fb.MoveRecordAddPlayer(b, int32(m.Player))
	fb.MoveRecordAddAction(b, action)
	fb.MoveRecordAddDir(b, dir)
	fb.MoveRecordAddMainRow(b, int32(m.MainRow))
	fb.MoveRecordAddMainCol(b, int32(m.MainCol))
	fb.MoveRecordAddTiles(b, tiles)
	fb.MoveRecordAddWords(b, words)
	fb.MoveRecordAddCount(b, int32(m.Count))
	fb.MoveRecordAddScore(b, int32(m.Score))
	fb.MoveRecordAddTotal(b, int32(m.Total))
	return fb.MoveRecordEnd(b)
}

// buildAlphabet builds the AlphabetEntry vector embedded in a StateView and returns
// its offset.
func buildAlphabet(b *flatbuffers.Builder, entries []AlphabetLetter) flatbuffers.UOffsetT {
	offs := make([]flatbuffers.UOffsetT, len(entries))
	for i, e := range entries {
		letter := b.CreateString(e.Letter)
		fb.AlphabetEntryStart(b)
		fb.AlphabetEntryAddIndex(b, byte(e.Index))
		fb.AlphabetEntryAddLetter(b, letter)
		fb.AlphabetEntryAddValue(b, int32(e.Value))
		offs[i] = fb.AlphabetEntryEnd(b)
	}
	fb.StateViewStartAlphabetVector(b, len(offs))
	for i := len(offs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(offs[i])
	}
	return b.EndVector(len(offs))
}

// buildStateView builds a StateView table from a PlayerState and returns its offset.
func buildStateView(b *flatbuffers.Builder, s PlayerState) flatbuffers.UOffsetT {
	game := buildGameView(b, s.Game)
	rackBytes := make([]byte, len(s.Rack))
	for i, v := range s.Rack {
		rackBytes[i] = byte(v)
	}
	rack := b.CreateByteVector(rackBytes)
	hasAlphabet := len(s.Alphabet) > 0
	var alphabet flatbuffers.UOffsetT
	if hasAlphabet {
		alphabet = buildAlphabet(b, s.Alphabet)
	}
	fb.StateViewStart(b)
	fb.StateViewAddGame(b, game)
	fb.StateViewAddSeat(b, int32(s.Seat))
	fb.StateViewAddRack(b, rack)
	fb.StateViewAddBagLen(b, int32(s.BagLen))
	fb.StateViewAddHintsRemaining(b, int32(s.HintsRemaining))
	if hasAlphabet {
		fb.StateViewAddAlphabet(b, alphabet)
	}
	return fb.StateViewEnd(b)
}

// buildAccountRef builds an AccountRef table and returns its offset.
func buildAccountRef(b *flatbuffers.Builder, a AccountRef) flatbuffers.UOffsetT {
	aid := b.CreateString(a.AccountID)
	name := b.CreateString(a.DisplayName)
	fb.AccountRefStart(b)
	fb.AccountRefAddAccountId(b, aid)
	fb.AccountRefAddDisplayName(b, name)
	return fb.AccountRefEnd(b)
}

// buildInvitation builds an Invitation table from an InvitationSummary and returns its offset.
func buildInvitation(b *flatbuffers.Builder, inv InvitationSummary) flatbuffers.UOffsetT {
	inviter := buildAccountRef(b, inv.Inviter)
	inviteeOffs := make([]flatbuffers.UOffsetT, len(inv.Invitees))
	for i, iv := range inv.Invitees {
		aid := b.CreateString(iv.AccountID)
		name := b.CreateString(iv.DisplayName)
		resp := b.CreateString(iv.Response)
		fb.InvitationInviteeStart(b)
		fb.InvitationInviteeAddAccountId(b, aid)
		fb.InvitationInviteeAddDisplayName(b, name)
		fb.InvitationInviteeAddSeat(b, int32(iv.Seat))
		fb.InvitationInviteeAddResponse(b, resp)
		inviteeOffs[i] = fb.InvitationInviteeEnd(b)
	}
	fb.InvitationStartInviteesVector(b, len(inviteeOffs))
	for i := len(inviteeOffs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(inviteeOffs[i])
	}
	invitees := b.EndVector(len(inviteeOffs))

	id := b.CreateString(inv.ID)
	variant := b.CreateString(inv.Variant)
	dropout := b.CreateString(inv.DropoutTiles)
	status := b.CreateString(inv.Status)
	gameID := b.CreateString(inv.GameID)
	fb.InvitationStart(b)
	fb.InvitationAddId(b, id)
	fb.InvitationAddInviter(b, inviter)
	fb.InvitationAddInvitees(b, invitees)
	fb.InvitationAddVariant(b, variant)
	fb.InvitationAddTurnTimeoutSecs(b, int32(inv.TurnTimeoutSecs))
	fb.InvitationAddHintsAllowed(b, inv.HintsAllowed)
	fb.InvitationAddHintsPerPlayer(b, int32(inv.HintsPerPlayer))
	fb.InvitationAddDropoutTiles(b, dropout)
	fb.InvitationAddStatus(b, status)
	fb.InvitationAddGameId(b, gameID)
	fb.InvitationAddExpiresAtUnix(b, inv.ExpiresAtUnix)
	return fb.InvitationEnd(b)
}