import express from 'express';
import swaggerUi from 'swagger-ui-express';
import YAML from 'yamljs';
import path from 'path';
import { fileURLToPath } from 'url';
import fs from 'fs/promises';
import crypto from 'crypto';
import { getAuthorData, getAuthorFilters } from 'stihirus-reader';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const app = express();
const port = process.env.PORT || 7860;
const CACHE_DIR = __dirname; // Use current directory for cache files
const CACHE_DURATION_MS = 60 * 60 * 1000; // 1 hour

const swaggerDocument = YAML.load(path.join(__dirname, 'openapi.yaml'));

app.use('/docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

// No need for ensureCacheDir anymore

function generateCacheKey(prefix, identifier, queryParams = {}) {
    const identifierPart = String(identifier).replace(/[^a-zA-Z0-9_-]/g, '_');
    let queryPart = '';
    const sortedKeys = Object.keys(queryParams).sort();
    sortedKeys.forEach(key => {
        if (queryParams[key] !== undefined && queryParams[key] !== null) {
            queryPart += `_${key}_${String(queryParams[key])}`;
        } else if (queryParams[key] === null) {
             queryPart += `_${key}_null`;
        }
    });
    // Add prefix to avoid potential collisions with other files
    return `_cache_${prefix}_${identifierPart}${queryPart}.json`;
}

async function readCache(key) {
    const filePath = path.join(CACHE_DIR, key);
    try {
        const stats = await fs.stat(filePath);
        const now = Date.now();
        const mtime = stats.mtime.getTime();
        const isStale = (now - mtime) > CACHE_DURATION_MS;
        const content = await fs.readFile(filePath, 'utf-8');
        const data = JSON.parse(content);
        return { data, isStale, exists: true, mtime };
    } catch (err) {
        if (err.code === 'ENOENT') {
            return { exists: false };
        }
        console.error(`Error reading cache file ${key}:`, err);
        return { exists: false, error: true };
    }
}

async function writeCache(key, data) {
    const filePath = path.join(CACHE_DIR, key);
    try {
        const content = JSON.stringify(data);
        await fs.writeFile(filePath, content, 'utf-8');
    } catch (err) {
        console.error(`Error writing cache file ${key}:`, err);
    }
}

app.get('/author/:identifier', async (req, res) => {
    const identifier = req.params.identifier;
    let page = req.query.page;
    let delay = req.query.delay;
    let pageNum = null;
    if (page !== undefined) {
        const parsedPage = parseInt(page, 10);
        if (!isNaN(parsedPage) && parsedPage >= 0) {
            pageNum = parsedPage;
        } else if (page === 'null' || page === '') {
             pageNum = null;
        } else {
            return res.status(400).json({ status: 'error', error: { code: 400, message: 'Invalid page parameter. Use null, 0, or a positive integer.' } });
        }
    }
    let delayMs = undefined;
     if (delay !== undefined) {
        const parsedDelay = parseInt(delay, 10);
        if (!isNaN(parsedDelay) && parsedDelay >= 0) {
            delayMs = parsedDelay;
        } else {
             return res.status(400).json({ status: 'error', error: { code: 400, message: 'Invalid delay parameter. Use a non-negative integer.' } });
        }
    }
    const cacheKey = generateCacheKey('author', identifier, { page: pageNum });
    let cacheEntry = null;
    try {
        cacheEntry = await readCache(cacheKey);
        if (cacheEntry.exists && !cacheEntry.isStale) {
            return res.json(cacheEntry.data);
        }
        const freshResult = await getAuthorData(identifier, pageNum, delayMs);
        if (freshResult.status === 'success') {
            await writeCache(cacheKey, freshResult);
            return res.json(freshResult);
        } else {
            if (cacheEntry.exists) {
                return res.json(cacheEntry.data);
            } else {
                return res.status(freshResult.error.code >= 400 && freshResult.error.code < 600 ? freshResult.error.code : 500).json(freshResult);
            }
        }
    } catch (err) {
         if (cacheEntry && cacheEntry.exists) {
             return res.json(cacheEntry.data);
         } else {
            console.error(`Error processing /author/${identifier} (CacheKey: ${cacheKey}):`, err);
            return res.status(500).json({ status: 'error', error: { code: 500, message: 'Internal Server Error', originalMessage: err.message } });
         }
    }
});

app.get('/author/:identifier/filters', async (req, res) => {
    const identifier = req.params.identifier;
    const cacheKey = generateCacheKey('filters', identifier);
    let cacheEntry = null;
     try {
        cacheEntry = await readCache(cacheKey);
        if (cacheEntry.exists && !cacheEntry.isStale) {
            return res.json(cacheEntry.data);
        }
        const freshResult = await getAuthorFilters(identifier);
         if (freshResult.status === 'success') {
            await writeCache(cacheKey, freshResult);
            return res.json(freshResult);
        } else {
             if (cacheEntry.exists) {
                return res.json(cacheEntry.data);
             } else {
                return res.status(freshResult.error.code >= 400 && freshResult.error.code < 600 ? freshResult.error.code : 500).json(freshResult);
             }
        }
    } catch (err) {
         if (cacheEntry && cacheEntry.exists) {
             return res.json(cacheEntry.data);
         } else {
            console.error(`Error processing /author/${identifier}/filters (CacheKey: ${cacheKey}):`, err);
            return res.status(500).json({ status: 'error', error: { code: 500, message: 'Internal Server Error', originalMessage: err.message } });
         }
    }
});

app.get('/', (req, res) => {
    res.redirect('/docs');
});

// No need to ensure cache dir here
app.listen(port, () => {
    console.log(`StihiRus API wrapper listening on port ${port}`);
    console.log(`Cache files will be stored in: ${CACHE_DIR}`);
    console.log(`API Docs available at /docs`);
});