/**
 * 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 NotionPage {
  id: string;
  code: string;
  rate: number | null;
  updatedAt: string | null;
}

interface NotionQueryResponse {
  results: Array<{
    id: string;
    properties: {
      Code: { title: Array<{ plain_text: string }> };
      Rate: { number: number | null };
      'Updated At': { date: { start: string } | null };
    };
  }>;
  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[];
}

interface ConvertResult {
  success: boolean;
  from: string;
  to: string;
  amount: number;
  rate: number;
  result: number;
  timestamp: string | null;
  error?: string;
}

interface RatesResult {
  base: string;
  timestamp: string | null;
  rates: Record<string, number>;
}

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 fetchNotionRates(
  databaseId: string,
  token: string
): Promise<NotionPage[]> {
  const pages: NotionPage[] = [];
  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) {
        pages.push({
          id: page.id,
          code,
          rate: page.properties.Rate.number,
          updatedAt: page.properties['Updated At'].date?.start || null,
        });
      }
    }

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

  return pages;
}

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: [],
  };

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

  try {
    console.log('Fetching existing pages from Notion...');
    const notionPages = await fetchNotionRates(env.NOTION_DATABASE_ID, env.NOTION_TOKEN);
    result.currenciesFound = notionPages.length;
    console.log(`Found ${notionPages.length} currencies in Notion database`);

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

    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}`);

    const results: UpdateResult[] = [];

    for (const page of notionPages) {
      const rate = oxrData.rates[page.code];

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

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

    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;
}

async function getRatesFromNotion(env: Env): Promise<RatesResult> {
  if (!env.NOTION_TOKEN || !env.NOTION_DATABASE_ID) {
    throw new Error('Missing NOTION_TOKEN or NOTION_DATABASE_ID');
  }

  const pages = await fetchNotionRates(env.NOTION_DATABASE_ID, env.NOTION_TOKEN);

  const rates: Record<string, number> = {};
  let latestTimestamp: string | null = null;

  for (const page of pages) {
    if (page.rate !== null) {
      rates[page.code] = page.rate;
      if (page.updatedAt && (!latestTimestamp || page.updatedAt > latestTimestamp)) {
        latestTimestamp = page.updatedAt;
      }
    }
  }

  return {
    base: 'USD',
    timestamp: latestTimestamp,
    rates,
  };
}

async function convertCurrency(
  env: Env,
  from: string,
  to: string,
  amount: number
): Promise<ConvertResult> {
  const result: ConvertResult = {
    success: false,
    from: from.toUpperCase(),
    to: to.toUpperCase(),
    amount,
    rate: 0,
    result: 0,
    timestamp: null,
  };

  try {
    const ratesData = await getRatesFromNotion(env);
    result.timestamp = ratesData.timestamp;

    const fromRate = ratesData.rates[from.toUpperCase()];
    const toRate = ratesData.rates[to.toUpperCase()];

    if (!fromRate) {
      result.error = `Unknown currency: ${from}`;
      return result;
    }

    if (!toRate) {
      result.error = `Unknown currency: ${to}`;
      return result;
    }

    // Convert: amount in USD = amount / fromRate
    // Then convert to target: result = amountInUSD * toRate
    const amountInUSD = amount / fromRate;
    const convertedAmount = amountInUSD * toRate;

    // Calculate the direct rate (1 from = X to)
    const directRate = toRate / fromRate;

    result.rate = directRate;
    result.result = convertedAmount;
    result.success = true;
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : String(error);
    result.error = errorMessage;
  }

  return result;
}

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

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

    // Currency conversion endpoint (data from Notion)
    if (url.pathname === '/convert') {
      const from = url.searchParams.get('from');
      const to = url.searchParams.get('to');
      const amountStr = url.searchParams.get('amount');

      if (!from || !to || !amountStr) {
        return new Response(
          JSON.stringify({
            error: 'Missing required parameters: from, to, amount',
            usage: '/convert?from=USD&to=CNY&amount=100',
          }),
          {
            status: 400,
            headers: { 'Content-Type': 'application/json' },
          }
        );
      }

      const amount = parseFloat(amountStr);
      if (isNaN(amount)) {
        return new Response(
          JSON.stringify({ error: 'Invalid amount. Must be a number.' }),
          {
            status: 400,
            headers: { 'Content-Type': 'application/json' },
          }
        );
      }

      const result = await convertCurrency(env, from, to, amount);
      return new Response(JSON.stringify(result, null, 2), {
        headers: { 'Content-Type': 'application/json' },
      });
    }

    // Rates endpoint - get all rates from Notion database
    if (url.pathname === '/rates') {
      const base = url.searchParams.get('base') || 'USD';

      try {
        const ratesData = await getRatesFromNotion(env);

        // If base is USD, return as-is
        if (base.toUpperCase() === 'USD') {
          return new Response(
            JSON.stringify(ratesData, null, 2),
            { headers: { 'Content-Type': 'application/json' } }
          );
        }

        // Otherwise, recalculate rates for the new base
        const baseRate = ratesData.rates[base.toUpperCase()];
        if (!baseRate) {
          return new Response(
            JSON.stringify({ error: `Unknown currency: ${base}` }),
            { status: 400, headers: { 'Content-Type': 'application/json' } }
          );
        }

        const convertedRates: Record<string, number> = {};
        for (const [currency, rate] of Object.entries(ratesData.rates)) {
          convertedRates[currency] = rate / baseRate;
        }
        convertedRates['USD'] = 1 / baseRate;

        return new Response(
          JSON.stringify(
            {
              base: base.toUpperCase(),
              timestamp: ratesData.timestamp,
              rates: convertedRates,
            },
            null,
            2
          ),
          { headers: { 'Content-Type': 'application/json' } }
        );
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return new Response(
          JSON.stringify({ error: errorMessage }),
          { status: 500, headers: { 'Content-Type': 'application/json' } }
        );
      }
    }

    // Home page
    return new Response(
      `Notion Exchange Rate Worker

API Endpoints:
  GET /convert?from=USD&to=CNY&amount=100  - Convert currency (data from Notion)
  GET /rates?base=USD                      - Get exchange rates (data from Notion)
  GET /sync                                - Sync rates from OXR to Notion`,
      { 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>;