forked from coracle/caravel
Jon Staab
49 lines
1.8 KiB
Rust
49 lines
1.8 KiB
Rust
use anyhow::{Result, anyhow};
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pub async fn fiat_to_msats(amount_fiat_minor: i64, currency: &str) -> Result<u64> {
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let price = get_bitcoin_price(¤cy.to_uppercase()).await?;
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let divisor = 10_f64.powi(currency_minor_exponent(currency)? as i32);
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let amount_fiat = (amount_fiat_minor as f64) / divisor;
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let amount_msats = (amount_fiat / price * 100_000_000_000.0).round();
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Ok(amount_msats as u64)
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}
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#[derive(serde::Deserialize)]
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struct CoinbaseSpotPriceResponse {
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data: CoinbaseSpotPriceData,
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}
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#[derive(serde::Deserialize)]
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struct CoinbaseSpotPriceData {
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amount: String,
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}
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pub async fn get_bitcoin_price(currency: &str) -> Result<f64> {
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let http = reqwest::Client::new();
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let url = format!("https://api.coinbase.com/v2/prices/BTC-{currency}/spot");
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let resp = http.get(url).send().await?;
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let body: CoinbaseSpotPriceResponse = resp.error_for_status()?.json().await?;
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body
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.data
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.amount
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.parse::<f64>()
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.map_err(|e| anyhow!("invalid BTC spot quote for {currency}: {e}"))
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}
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/// Number of decimal places in `currency`'s minor unit, following Stripe's
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/// currency conventions (most are 2, JPY/KRW/… are 0, BHD/KWD/… are 3).
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fn currency_minor_exponent(currency: &str) -> Result<u8> {
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let normalized = currency.to_uppercase();
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let exponent = match normalized.as_str() {
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// Zero-decimal currencies in Stripe.
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"BIF" | "CLP" | "DJF" | "GNF" | "JPY" | "KMF" | "KRW" | "MGA" | "PYG" | "RWF" | "UGX"
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| "VND" | "VUV" | "XAF" | "XOF" | "XPF" => 0,
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// Three-decimal currencies in Stripe.
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"BHD" | "JOD" | "KWD" | "OMR" | "TND" => 3,
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_ if normalized.chars().all(|c| c.is_ascii_alphabetic()) && normalized.len() == 3 => 2,
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_ => return Err(anyhow!("invalid currency code: {currency}")),
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};
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Ok(exponent)
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}
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