const KeyGenerator = require('./key_generator.js');

// handles creating new and requesting existing documents
class DocumentHandler {
    constructor(options) {
        if (!options) {
            options = {};
        }
        this.store = options.store;
        this.logger = options.logger;
        this.maxLength = options.maxLength || 50000;
        this.keyLength = options.keyLength || 10;
        this.createKey = options.createKey || '';
        this.keyGenerator = new KeyGenerator();

        if (this.createKey !== '') {
            this.logger.info("Creation-Key is configured.");
        }
    }

    // handles existing documents
    handleGet(key, res) {
        this.store.get(key, (ret) => {
            if (ret) {
                this.logger.verbose(`Open paste: ${key}`);
                res.writeHead(200, { 'content-type': 'application/json' });
                res.end(JSON.stringify({ key: key, data: ret.replace(/\t/g, '    ') }));
            } else {
                this.logger.verbose(`Paste not found: ${key}`);
                res.writeHead(404, { 'content-type': 'application/json' });
                res.end(JSON.stringify({ message: 'Paste not found.' }));
            }
        });
    }

    // handles existing documents (raw)
    handleRawGet(key, res) {
        this.store.get(key, (ret) => {
            if (ret) {
                this.logger.verbose(`Open raw paste: ${key}`);
                res.writeHead(200, { 'content-type': 'text/plain; charset=utf-8' });
                res.end(ret);
            } else {
                this.logger.verbose(`Paste not found: ${key}`);
                res.writeHead(404, { 'content-type': 'application/json' });
                res.end(JSON.stringify({ message: 'Paste not found.' }));
            }
        });
    }

    // handles creating new documents
    handlePost(req, res) {
        let buffer = '';
        let cancelled = false;

        req.on('data', (data) => {
            if (cancelled) return;
            buffer += data.toString();
            if (this.maxLength && buffer.length > this.maxLength) {
                cancelled = true;
                this.logger.warn('Paste exceeds maximum length.');
                res.writeHead(400, { 'content-type': 'application/json' });
                res.end(JSON.stringify({ message: 'Paste exceeds maximum length.' }));
            }
        });

        req.on('end', () => {
            if (cancelled) return;

            if (this.createKey !== '') {
                if (!buffer.startsWith(this.createKey)) {
                    this.logger.warn('Error adding new paste: wrong key');
                    res.writeHead(403, { 'content-type': 'application/json' });
                    res.end(JSON.stringify({ message: 'Error adding new paste: wrong key' }));
                    return;
                }
                buffer = buffer.substring(this.createKey.length);
            }

            this.chooseKey((key) => {
                this.store.set(key, buffer, (success) => {
                    if (success) {
                        this.logger.verbose(`New paste: ${key}`);
                        res.writeHead(200, { 'content-type': 'application/json' });
                        res.end(JSON.stringify({ key: key }));
                    } else {
                        this.logger.warn('Error adding new paste.');
                        res.writeHead(500, { 'content-type': 'application/json' });
                        res.end(JSON.stringify({ message: 'Error adding new paste.' }));
                    }
                });
            });
        });

        req.on('error', (error) => {
            this.logger.error(`Connection error: ${error.message}`);
            res.writeHead(500, { 'content-type': 'application/json' });
            res.end(JSON.stringify({ message: 'Connection error.' }));
        });
    }

    // creates new keys until one is not taken
    chooseKey(callback) {
        const key = this.acceptableKey();
        this.store.get(key, (success) => {
            if (success) {
                this.chooseKey(callback);
            } else {
                callback(key);
            }
        });
    }

    // creates a new key using the key-generator
    acceptableKey() {
        return this.keyGenerator.createKey(this.keyLength);
    }
}

module.exports = DocumentHandler;