package transcode

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

	"scrabble/gateway/internal/backendclient"
	fb "scrabble/pkg/fbs/scrabblefb"
)

// Stage 8 encoders: friends, blocks, invitations, statistics and GCG. They follow
// encode.go's bottom-up rule (build every string/child vector before the table).

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

// buildAccountRefVector builds a [AccountRef] vector using the table-specific
// StartXVector function and returns the vector offset.
func buildAccountRefVector(b *flatbuffers.Builder, refs []backendclient.AccountRefResp, start func(*flatbuffers.Builder, int) flatbuffers.UOffsetT) flatbuffers.UOffsetT {
	offs := make([]flatbuffers.UOffsetT, len(refs))
	for i, r := range refs {
		offs[i] = buildAccountRef(b, r)
	}
	start(b, len(offs))
	for i := len(offs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(offs[i])
	}
	return b.EndVector(len(offs))
}

// encodeFriendList builds a FriendList payload.
func encodeFriendList(r backendclient.FriendListResp) []byte {
	b := flatbuffers.NewBuilder(256)
	v := buildAccountRefVector(b, r.Friends, fb.FriendListStartFriendsVector)
	fb.FriendListStart(b)
	fb.FriendListAddFriends(b, v)
	b.Finish(fb.FriendListEnd(b))
	return b.FinishedBytes()
}

// encodeIncomingList builds an IncomingRequestList payload.
func encodeIncomingList(r backendclient.IncomingListResp) []byte {
	b := flatbuffers.NewBuilder(256)
	v := buildAccountRefVector(b, r.Requests, fb.IncomingRequestListStartRequestsVector)
	fb.IncomingRequestListStart(b)
	fb.IncomingRequestListAddRequests(b, v)
	b.Finish(fb.IncomingRequestListEnd(b))
	return b.FinishedBytes()
}

// encodeBlockList builds a BlockList payload.
func encodeBlockList(r backendclient.BlockListResp) []byte {
	b := flatbuffers.NewBuilder(256)
	v := buildAccountRefVector(b, r.Blocked, fb.BlockListStartBlockedVector)
	fb.BlockListStart(b)
	fb.BlockListAddBlocked(b, v)
	b.Finish(fb.BlockListEnd(b))
	return b.FinishedBytes()
}

// encodeFriendCode builds a FriendCode payload.
func encodeFriendCode(r backendclient.FriendCodeResp) []byte {
	b := flatbuffers.NewBuilder(64)
	code := b.CreateString(r.Code)
	fb.FriendCodeStart(b)
	fb.FriendCodeAddCode(b, code)
	fb.FriendCodeAddExpiresAtUnix(b, r.ExpiresAtUnix)
	b.Finish(fb.FriendCodeEnd(b))
	return b.FinishedBytes()
}

// encodeRedeemResult builds a RedeemResult payload.
func encodeRedeemResult(r backendclient.RedeemResultResp) []byte {
	b := flatbuffers.NewBuilder(128)
	friend := buildAccountRef(b, r.Friend)
	fb.RedeemResultStart(b)
	fb.RedeemResultAddFriend(b, friend)
	b.Finish(fb.RedeemResultEnd(b))
	return b.FinishedBytes()
}

// encodeStats builds a StatsView payload.
func encodeStats(r backendclient.StatsResp) []byte {
	b := flatbuffers.NewBuilder(64)
	fb.StatsViewStart(b)
	fb.StatsViewAddWins(b, int32(r.Wins))
	fb.StatsViewAddLosses(b, int32(r.Losses))
	fb.StatsViewAddDraws(b, int32(r.Draws))
	fb.StatsViewAddMaxGamePoints(b, int32(r.MaxGamePoints))
	fb.StatsViewAddMaxWordPoints(b, int32(r.MaxWordPoints))
	b.Finish(fb.StatsViewEnd(b))
	return b.FinishedBytes()
}

// buildInvitation builds an Invitation table and returns its offset.
func buildInvitation(b *flatbuffers.Builder, inv backendclient.InvitationResp) flatbuffers.UOffsetT {
	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))

	inviter := buildAccountRef(b, inv.Inviter)
	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)
}

// encodeInvitation builds an Invitation payload.
func encodeInvitation(inv backendclient.InvitationResp) []byte {
	b := flatbuffers.NewBuilder(512)
	b.Finish(buildInvitation(b, inv))
	return b.FinishedBytes()
}

// encodeInvitationList builds an InvitationList payload.
func encodeInvitationList(r backendclient.InvitationListResp) []byte {
	b := flatbuffers.NewBuilder(1024)
	offs := make([]flatbuffers.UOffsetT, len(r.Invitations))
	for i, inv := range r.Invitations {
		offs[i] = buildInvitation(b, inv)
	}
	fb.InvitationListStartInvitationsVector(b, len(offs))
	for i := len(offs) - 1; i >= 0; i-- {
		b.PrependUOffsetT(offs[i])
	}
	v := b.EndVector(len(offs))
	fb.InvitationListStart(b)
	fb.InvitationListAddInvitations(b, v)
	b.Finish(fb.InvitationListEnd(b))
	return b.FinishedBytes()
}

// encodeGcg builds a GcgExport payload.
func encodeGcg(r backendclient.GcgResp) []byte {
	b := flatbuffers.NewBuilder(1024)
	gid := b.CreateString(r.GameID)
	fn := b.CreateString(r.Filename)
	content := b.CreateString(r.Content)
	fb.GcgExportStart(b)
	fb.GcgExportAddGameId(b, gid)
	fb.GcgExportAddFilename(b, fn)
	fb.GcgExportAddContent(b, content)
	b.Finish(fb.GcgExportEnd(b))
	return b.FinishedBytes()
}