import { useCallback, useEffect, useRef, useState } from "react";
import type { Message } from "../types";

const STORAGE_KEY_PREFIX = "storykit-chat-history:";

function storageKey(projectPath: string): string {
	return `${STORAGE_KEY_PREFIX}${projectPath}`;
}

function loadMessages(projectPath: string): Message[] {
	try {
		const raw = localStorage.getItem(storageKey(projectPath));
		if (!raw) return [];
		const parsed: unknown = JSON.parse(raw);
		if (!Array.isArray(parsed)) return [];
		return parsed as Message[];
	} catch {
		return [];
	}
}

function saveMessages(projectPath: string, messages: Message[]): void {
	try {
		if (messages.length === 0) {
			localStorage.removeItem(storageKey(projectPath));
		} else {
			localStorage.setItem(storageKey(projectPath), JSON.stringify(messages));
		}
	} catch (e) {
		console.warn("Failed to persist chat history to localStorage:", e);
	}
}

export function useChatHistory(projectPath: string) {
	const [messages, setMessagesState] = useState<Message[]>(() =>
		loadMessages(projectPath),
	);
	const projectPathRef = useRef(projectPath);

	// Keep the ref in sync so the effect closure always has the latest path.
	projectPathRef.current = projectPath;

	// Persist whenever messages change.
	useEffect(() => {
		saveMessages(projectPathRef.current, messages);
	}, [messages]);

	const setMessages = useCallback(
		(update: Message[] | ((prev: Message[]) => Message[])) => {
			setMessagesState(update);
		},
		[],
	);

	const clearMessages = useCallback(() => {
		setMessagesState([]);
		// Eagerly remove from storage so clearSession doesn't depend on the
		// effect firing before the component unmounts or re-renders.
		try {
			localStorage.removeItem(storageKey(projectPathRef.current));
		} catch {
			// Ignore — quota or security errors.
		}
	}, []);

	return { messages, setMessages, clearMessages } as const;
}