const ChartJSImage = require('chart.js-image');
const pool = require('../shared/database/src/postgresql.js');
const fs = require('fs');
const axios = require('axios');
const logger = require('../shared/logger/src/main.js');

/**
 * Graph generation
 * @param {String} from_currency - The currency that is being converted
 * @param {String} conv_currency - The currency to be converted into
 * @param {String} start_date - Start date of the period
 * @param {String} end_date - End date of the period
 * @returns {Promise<Error|string>}
 */
async function gen_chart(from_currency, conv_currency, start_date, end_date) {
    const data = await pool.query(
        'SELECT date, rate FROM currency WHERE ' +
            '(date BETWEEN $3 AND $4) AND from_currency = $1 AND conv_currency = $2 ORDER BY date ',
        [
            from_currency.toUpperCase(),
            conv_currency.toUpperCase(),
            start_date,
            end_date,
        ],
    );

    if (!data['rows'][0]) return 'Missing data';

    const date = [];
    const rate = [];

    for (let i = 0; i < data.rows.length; i++) {
        date.push(data.rows[i].date.toLocaleDateString());
        rate.push(data.rows[i].rate);
    }

    const chart = ChartJSImage()
        .chart({
            type: 'line',
            options: {
                title: {
                    display: true,
                    text: `${from_currency} / ${conv_currency}`,
                },
                scales: [
                    {
                        yAxes: [
                            {
                                ticks: {
                                    beginAtZero: false,
                                },
                            },
                        ],
                    },
                ],
            },
            data: {
                labels: date,
                datasets: [
                    {
                        borderColor:
                            rate[0] < rate[rate.length - 1]
                                ? 'rgb(24, 218, 39)'
                                : 'rgb(243, 85, 50)',
                        backgroundColor:
                            rate[0] < rate[rate.length - 1]
                                ? 'rgb(36, 175, 47)'
                                : 'rgb(218, 56, 24)',
                        data: rate,
                        borderWidth: 2,
                    },
                ],
            },
            scales: {
                xAxes: [
                    {
                        scaleLabel: {
                            display: true,
                            labelString: 'Day',
                        },
                    },
                ],
                yAxes: [
                    {
                        stacked: false,
                        scaleLabel: {
                            display: true,
                            labelString: 'Rate',
                        },
                    },
                ],
            },
        })
        .width(1000)
        .height(1000);

    logger.debug(chart.toURL());

    return chart.toURL();
}

/**
 * Saving a graph to a file
 * @param {String} url  - URL (or Buffer) to the chart
 * @param {String} filename - filename
 */
function save_chart(url, filename) {
    if (!fs.existsSync('../charts')) fs.mkdirSync('../charts');
    if (!url.startsWith('https://'))
        throw new Error('The passed parameter is not a URL');

    logger.info(
        `The schedule has been saved. The path of the graph 'chart/${filename}'`,
    );
    axios({ url, responseType: 'stream' }).then(
        (response) =>
            new Promise((resolve, reject) => {
                response.data
                    .pipe(fs.createWriteStream(`../charts/${filename}`))
                    .on('finish', () => resolve())
                    .on('error', (e) => reject(e));
            }),
    );
}

module.exports = { gen_chart, save_chart };