candlestick-chart-generator/dataFetcher.js

A Node.js library for generating candlestick chart screenshots using financial data

const yahooFinance = require('yahoo-finance2').default;

class DataFetcher {
    constructor() {
        // Suppress the deprecation notice for historical API
        yahooFinance.suppressNotices(['ripHistorical']);
    }

    /**
     * Fetch historical OHLC data for a given symbol and interval
     * @param {string} symbol - The ticker symbol (e.g., 'AAPL', 'BTC-USD', 'EURUSD=X')
     * @param {string} interval - The time interval ('1m', '1h', '1d', etc.)
     * @param {string|Date} startDate - Start date for historical data
     * @param {string|Date} endDate - End date for historical data
     * @returns {Promise<Array>} Array of OHLC data formatted for Lightweight Charts
     */
    async fetchHistoricalData(symbol, interval, startDate, endDate) {
        try {
            // Convert interval to yahoo-finance2 format
            const yahooInterval = this._convertInterval(interval);
            
            // Prepare query options for chart API
            const queryOptions = {
                period1: startDate ? new Date(startDate) : new Date(Date.now() - 365 * 24 * 60 * 60 * 1000), // Default to 1 year ago
                period2: endDate ? new Date(endDate) : new Date(), // Default to now
                interval: yahooInterval
            };

            // Use chart API instead of historical (which is deprecated)
            const result = await yahooFinance.chart(symbol, queryOptions);
            
            if (!result || !result.quotes || result.quotes.length === 0) {
                throw new Error(`No data found for symbol: ${symbol}`);
            }

            // Transform data to Lightweight Charts format
            return this._transformChartData(result.quotes);
        } catch (error) {
            throw new Error(`Failed to fetch data for ${symbol}: ${error.message}`);
        }
    }

    /**
     * Convert interval string to yahoo-finance2 format
     * @param {string} interval - Input interval (e.g., '1m', '1h', '1d')
     * @returns {string} Yahoo Finance interval format
     */
    _convertInterval(interval) {
        const intervalMap = {
            '1m': '1m',
            '2m': '2m',
            '5m': '5m',
            '15m': '15m',
            '30m': '30m',
            '60m': '60m',
            '90m': '90m',
            '1h': '1h',
            '1d': '1d',
            '5d': '5d',
            '1wk': '1wk',
            '1mo': '1mo',
            '3mo': '3mo'
        };

        const yahooInterval = intervalMap[interval];
        if (!yahooInterval) {
            throw new Error(`Unsupported interval: ${interval}. Supported intervals: ${Object.keys(intervalMap).join(', ')}`);
        }

        return yahooInterval;
    }



    /**
     * Transform Yahoo Finance chart data to Lightweight Charts format
     * @param {Array} quotes - Raw quotes data from Yahoo Finance chart API
     * @returns {Array} Transformed data for Lightweight Charts
     */
    _transformChartData(quotes) {
        return quotes
            .filter(quote => quote.open !== null && quote.high !== null && quote.low !== null && quote.close !== null)
            .map(quote => ({
                time: Math.floor(quote.date.getTime() / 1000), // Convert to Unix timestamp
                open: parseFloat(quote.open),
                high: parseFloat(quote.high),
                low: parseFloat(quote.low),
                close: parseFloat(quote.close)
            }))
            .sort((a, b) => a.time - b.time); // Ensure chronological order
    }
}

module.exports = DataFetcher;