import axios from 'axios';

/**
 * I18n client for translation and localization
 * Used by other services to get translations and format values
 */
export class I18nClient {
    constructor(config = {}) {
        this.baseURL = config.baseURL || process.env.I18N_SERVICE_URL || 'http://localhost:3011';
        this.timeout = config.timeout || 30000;
        this.apiVersion = config.apiVersion || 'v1';
        this.defaultLanguage = config.defaultLanguage || 'en';
        this.cache = new Map();
        this.cacheTimeout = config.cacheTimeout || 300000; // 5 minutes
        
        this.client = axios.create({
            baseURL: `${this.baseURL}/api/${this.apiVersion}`,
            timeout: this.timeout,
            headers: {
                'Content-Type': 'application/json'
            }
        });
        
        // Add request interceptor for internal service header
        this.client.interceptors.request.use(config => {
            config.headers['X-Internal-Service'] = process.env.SERVICE_NAME || 'unknown';
            return config;
        });
    }
    
    /**
     * Get single translation
     */
    async translate(key, language = this.defaultLanguage, options = {}) {
        const cacheKey = `${language}:${key}:${options.namespace || 'translation'}`;
        
        // Check cache
        const cached = this.getFromCache(cacheKey);
        if (cached) return cached;
        
        try {
            const response = await this.client.get('/translations', {
                params: {
                    key,
                    language,
                    namespace: options.namespace || 'translation'
                }
            });
            
            const value = response.data.translation.value;
            this.setCache(cacheKey, value);
            
            return this.interpolate(value, options.variables || {});
        } catch (error) {
            console.error('Translation error:', error);
            return options.defaultValue || key;
        }
    }
    
    /**
     * Get multiple translations
     */
    async translateBatch(keys, language = this.defaultLanguage, options = {}) {
        try {
            const response = await this.client.get('/translations', {
                params: {
                    keys: keys.join(','),
                    language,
                    namespace: options.namespace || 'translation'
                }
            });
            
            return response.data.translations;
        } catch (error) {
            console.error('Batch translation error:', error);
            // Return keys as fallback
            return keys.reduce((acc, key) => {
                acc[key] = key;
                return acc;
            }, {});
        }
    }
    
    /**
     * Detect user's language
     */
    async detectLanguage(headers = {}) {
        try {
            const response = await this.client.get('/languages/detect', {
                headers: {
                    'accept-language': headers['accept-language'],
                    'cf-ipcountry': headers['cf-ipcountry']
                }
            });
            
            return response.data.language;
        } catch (error) {
            console.error('Language detection error:', error);
            return this.defaultLanguage;
        }
    }
    
    /**
     * Get enabled languages
     */
    async getLanguages() {
        const cacheKey = 'enabled-languages';
        const cached = this.getFromCache(cacheKey);
        if (cached) return cached;
        
        try {
            const response = await this.client.get('/languages/enabled');
            const languages = response.data.languages;
            
            this.setCache(cacheKey, languages, 3600000); // Cache for 1 hour
            return languages;
        } catch (error) {
            console.error('Get languages error:', error);
            return [];
        }
    }
    
    /**
     * Format number
     */
    async formatNumber(number, language = this.defaultLanguage, options = {}) {
        try {
            const response = await this.client.post('/localization/format/number', {
                number,
                language,
                options
            });
            
            return response.data.formatted;
        } catch (error) {
            console.error('Number formatting error:', error);
            return number.toString();
        }
    }
    
    /**
     * Format currency
     */
    async formatCurrency(amount, language = this.defaultLanguage, currency = 'USD') {
        try {
            const response = await this.client.post('/localization/format/currency', {
                amount,
                language,
                currency
            });
            
            return response.data.formatted;
        } catch (error) {
            console.error('Currency formatting error:', error);
            return `${currency} ${amount}`;
        }
    }
    
    /**
     * Format date
     */
    async formatDate(date, language = this.defaultLanguage, options = {}) {
        try {
            const response = await this.client.post('/localization/format/date', {
                date,
                language,
                options
            });
            
            return response.data.formatted;
        } catch (error) {
            console.error('Date formatting error:', error);
            return new Date(date).toLocaleString();
        }
    }
    
    /**
     * Format relative time
     */
    async formatRelativeTime(date, language = this.defaultLanguage) {
        try {
            const response = await this.client.post('/localization/format/relative-time', {
                date,
                language
            });
            
            return response.data.formatted;
        } catch (error) {
            console.error('Relative time formatting error:', error);
            return date;
        }
    }
    
    /**
     * Get text direction
     */
    async getTextDirection(language = this.defaultLanguage) {
        const cacheKey = `direction:${language}`;
        const cached = this.getFromCache(cacheKey);
        if (cached) return cached;
        
        try {
            const response = await this.client.get(`/localization/direction/${language}`);
            const direction = response.data.direction;
            
            this.setCache(cacheKey, direction, 3600000); // Cache for 1 hour
            return direction;
        } catch (error) {
            console.error('Get text direction error:', error);
            return 'ltr';
        }
    }
    
    /**
     * Create i18n middleware for Express
     */
    middleware() {
        return async (req, res, next) => {
            // Detect language
            req.language = await this.detectLanguage(req.headers);
            
            // Add translation function
            req.t = (key, options = {}) => {
                return this.translate(key, req.language, options);
            };
            
            // Add formatting functions
            req.formatNumber = (number, options) => {
                return this.formatNumber(number, req.language, options);
            };
            
            req.formatCurrency = (amount, currency) => {
                return this.formatCurrency(amount, req.language, currency);
            };
            
            req.formatDate = (date, options) => {
                return this.formatDate(date, req.language, options);
            };
            
            // Set response language header
            res.setHeader('Content-Language', req.language);
            
            next();
        };
    }
    
    /**
     * Interpolate variables in text
     */
    interpolate(text, variables = {}) {
        return text.replace(/\{\{(\w+)\}\}/g, (match, key) => {
            return variables[key] !== undefined ? variables[key] : match;
        });
    }
    
    /**
     * Cache management
     */
    getFromCache(key) {
        const cached = this.cache.get(key);
        if (!cached) return null;
        
        if (Date.now() > cached.expires) {
            this.cache.delete(key);
            return null;
        }
        
        return cached.value;
    }
    
    setCache(key, value, timeout = this.cacheTimeout) {
        this.cache.set(key, {
            value,
            expires: Date.now() + timeout
        });
    }
    
    clearCache() {
        this.cache.clear();
    }
}

// Singleton instance
let defaultClient = null;

export const getI18nClient = (config) => {
    if (!defaultClient) {
        defaultClient = new I18nClient(config);
    }
    return defaultClient;
};

// Direct exports for convenience
export const translate = async (key, language, options) => {
    const client = getI18nClient();
    return client.translate(key, language, options);
};

export const detectLanguage = async (headers) => {
    const client = getI18nClient();
    return client.detectLanguage(headers);
};