import { ref } from "vue";
import { SettingAPI } from "timi-web-api";

const AI_QUICK_QUESTION_CACHE_KEY = "gao-customer-h5:ai-agent-example";
const AI_QUICK_QUESTION_CACHE_TTL = 24 * 60 * 60 * 1000;
const AI_QUICK_QUESTION_COUNT = 5;

interface AiQuickQuestionCache {
	cachedAt: number;
	questionList: string[];
}

/** 从快捷问题题库中随机抽取指定数量的问题。 */
export function getRandomAiQuickQuestions(count = AI_QUICK_QUESTION_COUNT, questionPool: readonly string[] = []): string[] {
	const result: string[] = [...questionPool];
	const targetCount = Math.min(Math.max(Math.floor(count), 0), result.length);

	for (let index = 0; index < targetCount; index += 1) {
		const randomIndex = index + Math.floor(Math.random() * (result.length - index));
		[result[index], result[randomIndex]] = [result[randomIndex], result[index]];
	}

	return result.slice(0, targetCount);
}

/** 清理并去重快捷问题。 */
function normalizeAiQuickQuestionList(value: unknown): string[] {
	if (!Array.isArray(value)) {
		return [];
	}

	return [...new Set(value.filter((item): item is string => typeof item === "string").map(item => item.trim()).filter(Boolean))];
}

/** 将 Setting 中的题库值解析为有效的快捷问题列表。 */
function parseAiQuickQuestionList(value: unknown): string[] {
	if (typeof value !== "string") {
		return [];
	}

	try {
		return normalizeAiQuickQuestionList(JSON.parse(value));
	} catch {
		return [];
	}
}

/** 读取一天内有效的本地题库缓存。 */
function readAiQuickQuestionCache(): string[] {
	try {
		const cacheValue = localStorage.getItem(AI_QUICK_QUESTION_CACHE_KEY);
		if (!cacheValue) {
			return [];
		}

		const cache: unknown = JSON.parse(cacheValue);
		if (typeof cache !== "object" || cache === null || !("cachedAt" in cache) || !("questionList" in cache)) {
			return [];
		}

		const typedCache = cache as AiQuickQuestionCache;
		if (typeof typedCache.cachedAt !== "number" || !Number.isFinite(typedCache.cachedAt)) {
			return [];
		}

		const cacheAge = Date.now() - typedCache.cachedAt;
		if (cacheAge < 0 || AI_QUICK_QUESTION_CACHE_TTL < cacheAge || !Array.isArray(typedCache.questionList)) {
			return [];
		}

		return normalizeAiQuickQuestionList(typedCache.questionList);
	} catch {
		return [];
	}
}

/** 将动态题库缓存到本地一天。 */
function writeAiQuickQuestionCache(questionList: string[]): void {
	try {
		const cache: AiQuickQuestionCache = {
			cachedAt: Date.now(),
			questionList
		};
		localStorage.setItem(AI_QUICK_QUESTION_CACHE_KEY, JSON.stringify(cache));
	} catch {
		// 本地存储不可用时跳过缓存。
	}
}

/** 从系统设置中获取动态快捷问题题库。 */
async function fetchAiQuickQuestionPool(): Promise<string[]> {
	const settingMap = await SettingAPI.map("GAO_SYSTEM", undefined, ["AI_AGENT_EXAMPLE"]);
	return parseAiQuickQuestionList(settingMap.AI_AGENT_EXAMPLE?.value);
}

let loadingPromise: Promise<void> | undefined;
let currentAiQuickQuestionPool: string[] = [];

/** 从已加载的题库中重新抽取快捷问题。 */
export function refreshAiQuickQuestions(): void {
	aiQuickQuestionList.value = getRandomAiQuickQuestions(AI_QUICK_QUESTION_COUNT, currentAiQuickQuestionPool);
}

/** 加载动态题库并刷新当前会话展示的问题。 */
export async function loadAiQuickQuestions(): Promise<void> {
	if (loadingPromise) {
		await loadingPromise;
		return;
	}

	loadingPromise = (async () => {
		const cachedQuestionList = readAiQuickQuestionCache();
		if (cachedQuestionList.length > 0) {
			currentAiQuickQuestionPool = cachedQuestionList;
			refreshAiQuickQuestions();
			return;
		}

		currentAiQuickQuestionPool = [];
		aiQuickQuestionList.value = [];
		try {
			const questionList = await fetchAiQuickQuestionPool();
			if (questionList.length > 0) {
				currentAiQuickQuestionPool = questionList;
				writeAiQuickQuestionCache(questionList);
				refreshAiQuickQuestions();
			}
		} catch {
			// 接口异常时保持为空。
		}
	})();

	try {
		await loadingPromise;
	} finally {
		loadingPromise = undefined;
	}
}

/** 当前会话欢迎页展示的快捷问题。 */
export const aiQuickQuestionList = ref<string[]>([]);