satshkd-vercel/calculate.js

const axios = require('axios')
const fs = require('fs');

module.exports = {
    bfx: async function() {
        const eurrate = 0.92 // approximate EUR/USD rate
        const btcDataURL = "https://api-pub.bitfinex.com/v2/ticker/tBTCUSD"
        const response = await axios.get(btcDataURL)
        const data = response.data
            //console.log(data[6])

        const satDenominator = 100000000
            // see docs : https://docs.bitfinex.com/reference#rest-public-ticker
        btcLastPrice = data[6]

        const sateur = Math.round((1 / btcLastPrice) * satDenominator * eurrate)
            //console.log("bitfinex last price: ", btcLastPrice, "current satEUR: ", sateur)
        return sateur
    },

    get10yr: async function() {
        //        console.log("get10yr")
        try {
            // const content = await fs.readFile('./public/historical')
            const content = fs.readFileSync('./public/historical', { encoding: 'utf8' })

            const historical = JSON.parse(content)
            hist_entries = []
            let datelist = []

            // get all the years you need from 1 - 10
            for (let i = 1; i < 11; i++) {
                const targetDate = new Date(new Date().setFullYear(new Date().getFullYear() - i))
                const targetDateStr = targetDate.toISOString().slice(0, 10)

                // Find the closest date in historical data
                let closestEntry = null
                let minDiff = Infinity

                for (let j = 0; j < historical.length; j++) {
                    const entryDate = new Date(historical[j]['date'])
                    const diff = Math.abs(entryDate - targetDate)

                    if (diff < minDiff) {
                        minDiff = diff
                        closestEntry = historical[j]
                    }
                }

                if (closestEntry) {
                    hist_entries.push(closestEntry)
                }
            }
            //  console.log(hist_entries)
            let final_list = []

            // Try to get current price from API, fallback to latest historical data if API fails
            let today_sats
            try {
                today_sats = await this.bfx()
            } catch (apiError) {
                console.log("API failed, using latest historical data as fallback")
                // Use the most recent entry in historical data as today's price
                today_sats = historical[historical.length - 1]['sateur_rate']
            }

            for (var v = 0; v < hist_entries.length; v++) {
                const date = new Date(hist_entries[v]['date'])
                year = date.getFullYear();
                rawsat = hist_entries[v]['sateur_rate']
                percentage = (-100 * ((rawsat - today_sats) / rawsat)).toFixed(3)
                final_list.push({ "year": date.toLocaleDateString(), "sats": rawsat.toLocaleString("en-US"), "percent": percentage });
            }
            return final_list.reverse()
        } catch (error) {
            console.error("Error trying to read file ", error)
        }
    }

}