compute optimistic states

Author: tknkaa

app/routes/play/computeOptimisticGameState.ts

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+import type { Fetcher } from "react-router";
+import { sortTehai } from "~/lib/hai/types";
+import type { GameState } from "~/lib/types";
+import { TOTAL_TSUMO_PER_KYOKU } from "./constants";
+
+export function computeOptimisticGameState(
+	loaderData: GameState,
+	discardFetcher: Fetcher<GameState>,
+) {
+	const fetcherGameState =
+		discardFetcher.data && "tehai" in discardFetcher.data
+			? discardFetcher.data
+			: null;
+
+	const currentGameState =
+		fetcherGameState?.kyoku === loaderData.kyoku
+			? fetcherGameState
+			: loaderData;
+
+	const {
+		sutehai,
+		tsumohai,
+		nextTsumohai,
+		junme,
+		kyoku,
+		tehai,
+		remainTsumo,
+		score,
+	} = currentGameState;
+
+	const baseSortedTehai = sortTehai(tehai);
+
+	let optimisticSutehai = sutehai;
+	let optimisticTehai = baseSortedTehai;
+	let optimisticTsumohai = tsumohai;
+	let optimisticJunme = junme;
+	let optimisticRemainTsumo = remainTsumo;
+
+	if (
+		discardFetcher.state !== "idle" &&
+		discardFetcher.formData &&
+		tsumohai !== null
+	) {
+		const nextRemainTsumo = Math.max(0, remainTsumo - 1);
+
+		if (discardFetcher.formAction?.endsWith("/api/tedashi")) {
+			const index = Number(discardFetcher.formData.get("index"));
+			if (
+				Number.isInteger(index) &&
+				index >= 0 &&
+				index < baseSortedTehai.length
+			) {
+				const discardHai = baseSortedTehai[index];
+				const remainingTehai = baseSortedTehai.filter((_, i) => i !== index);
+				optimisticSutehai = [...sutehai, discardHai];
+				optimisticTehai = sortTehai([...remainingTehai, tsumohai]);
+				optimisticTsumohai = nextTsumohai;
+				optimisticJunme = junme + 1;
+				optimisticRemainTsumo = nextRemainTsumo;
+			}
+		} else if (discardFetcher.formAction?.endsWith("/api/tsumogii")) {
+			optimisticSutehai = [...sutehai, tsumohai];
+			optimisticTsumohai = nextTsumohai;
+			optimisticJunme = junme + 1;
+			optimisticRemainTsumo = nextRemainTsumo;
+		}
+	}
+	const tsumoProgressValue = Math.max(
+		0,
+		TOTAL_TSUMO_PER_KYOKU - optimisticRemainTsumo,
+	);
+	return {
+		currentGameState,
+		kyoku,
+		score,
+		optimisticTehai,
+		optimisticTsumohai,
+		optimisticSutehai,
+		optimisticJunme,
+		optimisticRemainTsumo,
+		tsumoProgressValue,
+	};
+}

app/routes/play/constants.ts

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+export const TOTAL_TSUMO_PER_KYOKU = 18;