/**
 * Notion Exchange Rate Worker
 *
 * Fetches daily exchange rates from Open Exchange Rates API
 * and updates a Notion database with the latest rates.
 *
 * - Run `npm run dev` in your terminal to start a development server
 * - Run `curl "http://localhost:8787/__scheduled?cron=0+0+*+*+*"` to test the scheduled handler
 * - Run `npm run deploy` to publish your Worker
 */

interface OXRResponse {
	base: string;
	rates: Record<string, number>;
	timestamp: number;
}

interface NotionQueryResponse {
	results: Array<{
		id: string;
		properties: {
			Code: { title: Array<{ plain_text: string }> };
		};
	}>;
	has_more: boolean;
	next_cursor: string | null;
}

interface UpdateResult {
	currency: string;
	success: boolean;
	error?: string;
}

interface SyncResult {
	success: boolean;
	currenciesFound: number;
	ratesFetched: number;
	succeeded: number;
	failed: number;
	errors: string[];
}

async function fetchExchangeRates(appId: string): Promise<OXRResponse> {
	const url = `https://openexchangerates.org/api/latest.json?app_id=${appId}`;
	const response = await fetch(url);

	if (!response.ok) {
		throw new Error(`OXR API error: ${response.status} ${response.statusText}`);
	}

	return response.json() as Promise<OXRResponse>;
}

async function fetchAllNotionPages(
	databaseId: string,
	token: string
): Promise<Map<string, string>> {
	const currencyMap = new Map<string, string>();
	let hasMore = true;
	let nextCursor: string | null = null;

	while (hasMore) {
		const body: { page_size: number; start_cursor?: string } = { page_size: 100 };
		if (nextCursor) {
			body.start_cursor = nextCursor;
		}

		const response = await fetch(`https://api.notion.com/v1/databases/${databaseId}/query`, {
			method: 'POST',
			headers: {
				'Authorization': `Bearer ${token}`,
				'Content-Type': 'application/json',
				'Notion-Version': '2022-06-28',
			},
			body: JSON.stringify(body),
		});

		if (!response.ok) {
			const errorText = await response.text();
			throw new Error(`Notion query error: ${response.status} - ${errorText}`);
		}

		const data = (await response.json()) as NotionQueryResponse;

		for (const page of data.results) {
			const code = page.properties.Code.title[0]?.plain_text;
			if (code) {
				currencyMap.set(code, page.id);
			}
		}

		hasMore = data.has_more;
		nextCursor = data.next_cursor;
	}

	return currencyMap;
}

async function updateNotionPage(
	pageId: string,
	token: string,
	rate: number
): Promise<void> {
	const now = new Date().toISOString();

	const response = await fetch(`https://api.notion.com/v1/pages/${pageId}`, {
		method: 'PATCH',
		headers: {
			'Authorization': `Bearer ${token}`,
			'Content-Type': 'application/json',
			'Notion-Version': '2022-06-28',
		},
		body: JSON.stringify({
			properties: {
				Rate: {
					number: rate,
				},
				'Updated At': {
					date: {
						start: now,
					},
				},
			},
		}),
	});

	if (!response.ok) {
		const errorText = await response.text();
		throw new Error(`Notion update error: ${response.status} - ${errorText}`);
	}
}

async function syncExchangeRates(env: Env): Promise<SyncResult> {
	const result: SyncResult = {
		success: false,
		currenciesFound: 0,
		ratesFetched: 0,
		succeeded: 0,
		failed: 0,
		errors: [],
	};

	// Validate environment variables
	if (!env.OXR_APP_ID || !env.NOTION_TOKEN || !env.NOTION_DATABASE_ID) {
		result.errors.push('Missing required environment variables');
		return result;
	}

	try {
		// Step 1: Fetch all existing pages from Notion database
		console.log('Fetching existing pages from Notion...');
		const currencyMap = await fetchAllNotionPages(env.NOTION_DATABASE_ID, env.NOTION_TOKEN);
		result.currenciesFound = currencyMap.size;
		console.log(`Found ${currencyMap.size} currencies in Notion database`);

		if (currencyMap.size === 0) {
			result.success = true;
			console.log('No currencies found in Notion database. Nothing to update.');
			return result;
		}

		// Step 2: Fetch exchange rates from OXR
		console.log('Fetching exchange rates from OXR...');
		const oxrData = await fetchExchangeRates(env.OXR_APP_ID);
		result.ratesFetched = Object.keys(oxrData.rates).length;
		console.log(`Fetched ${result.ratesFetched} currency rates. Base: ${oxrData.base}`);

		// Step 3: Update only currencies that exist in Notion
		const results: UpdateResult[] = [];

		for (const [currencyCode, pageId] of currencyMap) {
			const rate = oxrData.rates[currencyCode];

			if (rate === undefined) {
				console.warn(`No rate found for ${currencyCode} in OXR data`);
				continue;
			}

			try {
				await updateNotionPage(pageId, env.NOTION_TOKEN, rate);
				results.push({ currency: currencyCode, success: true });
			} catch (error) {
				const errorMessage = error instanceof Error ? error.message : String(error);
				results.push({ currency: currencyCode, success: false, error: errorMessage });
				result.errors.push(`${currencyCode}: ${errorMessage}`);
				console.error(`Failed to update ${currencyCode}: ${errorMessage}`);
			}
		}

		// Summary
		result.succeeded = results.filter((r) => r.success).length;
		result.failed = results.filter((r) => !r.success).length;
		result.success = true;
		console.log(`Sync completed: ${result.succeeded} succeeded, ${result.failed} failed`);
	} catch (error) {
		const errorMessage = error instanceof Error ? error.message : String(error);
		result.errors.push(errorMessage);
		console.error(`Exchange rate sync failed: ${errorMessage}`);
	}

	return result;
}

export default {
	async fetch(req, env, ctx): Promise<Response> {
		const url = new URL(req.url);

		// Manual trigger endpoint
		if (url.pathname === '/sync') {
			const result = await syncExchangeRates(env);
			return new Response(JSON.stringify(result, null, 2), {
				headers: { 'Content-Type': 'application/json' },
			});
		}

		return new Response('Notion Exchange Rate Worker\n\nUse /sync to manually trigger sync.', {
			headers: { 'Content-Type': 'text/plain' },
		});
	},

	async scheduled(event, env, ctx): Promise<void> {
		console.log(`Exchange rate sync started at ${event.cron}`);
		await syncExchangeRates(env);
	},
} satisfies ExportedHandler<Env>;