import type { Encounter, UndoRedoState } from "@initiative/domain";
import { EMPTY_UNDO_REDO_STATE } from "@initiative/domain";
import { rehydrateEncounter } from "./encounter-storage.js";

const UNDO_KEY = "initiative:encounter:undo";
const REDO_KEY = "initiative:encounter:redo";

export function saveUndoRedoStacks(state: UndoRedoState): void {
	try {
		localStorage.setItem(UNDO_KEY, JSON.stringify(state.undoStack));
		localStorage.setItem(REDO_KEY, JSON.stringify(state.redoStack));
	} catch {
		// Silently swallow errors (quota exceeded, storage unavailable)
	}
}

function loadStack(key: string): readonly Encounter[] {
	try {
		const raw = localStorage.getItem(key);
		if (raw === null) return [];

		const parsed: unknown = JSON.parse(raw);
		if (!Array.isArray(parsed)) return [];

		const valid: Encounter[] = [];
		for (const entry of parsed) {
			const rehydrated = rehydrateEncounter(entry);
			if (rehydrated !== null) {
				valid.push(rehydrated);
			}
		}
		return valid;
	} catch {
		return [];
	}
}

export function loadUndoRedoStacks(): UndoRedoState {
	const undoStack = loadStack(UNDO_KEY);
	const redoStack = loadStack(REDO_KEY);
	if (undoStack.length === 0 && redoStack.length === 0) {
		return EMPTY_UNDO_REDO_STATE;
	}
	return { undoStack, redoStack };
}