Implement a minimal BTC/USD price feed feature

Author: zahorodnyi

crates/cli-client/Cargo.toml

@@ -48,3 +48,6 @@ nostr = { version = "0.44.2" }
 nostr-sdk = { version = "0.44.1" }
 
 minreq = { version = "2.14", features = ["https", "json-using-serde"] }
+reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
+rust_decimal = { version = "1", features = ["serde"] }
+async-trait = "0.1.89"

crates/cli-client/src/cli/commands.rs

@@ -33,6 +33,9 @@ pub enum Command {
     /// Show my holdings with expiration warnings
     Positions,
 
+    /// Show current BTC/USD price feed
+    PriceFeed,
+
     /// Sync coin-store with blockchain via Esplora and/or NOSTR
     Sync {
         #[command(subcommand)]

crates/cli-client/src/cli/mod.rs

@@ -4,6 +4,7 @@ mod interactive;
 mod option;
 mod option_offer;
 mod positions;
+mod price;
 mod sync;
 mod tables;
 mod tx;
@@ -102,6 +103,7 @@ impl Cli {
             Command::Browse => self.run_browse(config).await,
             Command::Positions => self.run_positions(config).await,
             Command::Sync { command } => self.run_sync(config, command).await,
+            Command::PriceFeed => price::run_price_feed().await,
             Command::Config => {
                 println!("{config:#?}");
                 Ok(())

crates/cli-client/src/cli/price.rs

@@ -0,0 +1,16 @@
+use crate::error::Error;
+use crate::price_fetcher::{CoingeckoPriceFetcher, PriceFetcher};
+use rust_decimal::Decimal;
+
+pub async fn fetch_btc_usd_price<T: PriceFetcher>(fetcher: &T) -> Result<Decimal, Error> {
+    Ok(fetcher.fetch_price().await?)
+}
+
+pub async fn run_price_feed() -> Result<(), Error> {
+    let fetcher = CoingeckoPriceFetcher::new()?;
+    let price = fetch_btc_usd_price(&fetcher).await?;
+
+    println!("1 BTC = ${}", price.round_dp(2));
+
+    Ok(())
+}

crates/cli-client/src/error.rs

@@ -55,4 +55,7 @@ pub enum Error {
 
     #[error("Taproot pubkey generation error: {0}")]
     TaprootPubkeyGen(#[from] contracts::error::TaprootPubkeyGenError),
+
+    #[error("Price feed error: {0}")]
+    PriceFeed(#[from] crate::price_fetcher::PriceFetcherError),
 }

crates/cli-client/src/main.rs

@@ -7,6 +7,7 @@ mod explorer;
 mod fee;
 mod logging;
 mod metadata;
+mod price_fetcher;
 mod signing;
 mod sync;
 mod wallet;

crates/cli-client/src/price_fetcher.rs

@@ -0,0 +1,76 @@
+use async_trait::async_trait;
+use rust_decimal::Decimal;
+use serde::Deserialize;
+use std::time::Duration;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum PriceFetcherError {
+    #[error("Request error: {0}")]
+    Request(#[from] reqwest::Error),
+    #[error("Rate limit exceeded (429)")]
+    RateLimit,
+    #[error("Response status error: {0}")]
+    Status(u16),
+    #[error("Parse error: {0}")]
+    Parse(String),
+    #[error("Client build error: {0}")]
+    Build(String),
+}
+
+#[derive(Deserialize)]
+struct BitcoinResponse {
+    bitcoin: BitcoinPrice,
+}
+
+#[derive(Deserialize)]
+struct BitcoinPrice {
+    usd: Decimal,
+}
+
+#[async_trait]
+pub trait PriceFetcher {
+    async fn fetch_price(&self) -> Result<Decimal, PriceFetcherError>;
+}
+
+pub struct CoingeckoPriceFetcher {
+    client: reqwest::Client,
+}
+
+impl CoingeckoPriceFetcher {
+    const URL: &'static str = "https://api.coingecko.com/api/v3";
+    const REQUEST_TIMEOUT: Duration = Duration::from_secs(5);
+
+    pub fn new() -> Result<Self, PriceFetcherError> {
+        let client = reqwest::Client::builder()
+            .user_agent("simplicity-dex/1.0")
+            .timeout(Self::REQUEST_TIMEOUT)
+            .build()
+            .map_err(|e| PriceFetcherError::Build(e.to_string()))?;
+
+        Ok(Self { client })
+    }
+}
+
+#[async_trait]
+impl PriceFetcher for CoingeckoPriceFetcher {
+    async fn fetch_price(&self) -> Result<Decimal, PriceFetcherError> {
+        let url = format!("{}/simple/price", Self::URL);
+
+        let resp = self
+            .client
+            .get(&url)
+            .query(&[("ids", "bitcoin"), ("vs_currencies", "usd"), ("precision", "8")])
+            .send()
+            .await?;
+
+        match resp.status() {
+            reqwest::StatusCode::OK => {
+                let data: BitcoinResponse = resp.json().await.map_err(|e| PriceFetcherError::Parse(e.to_string()))?;
+                Ok(data.bitcoin.usd)
+            }
+            reqwest::StatusCode::TOO_MANY_REQUESTS => Err(PriceFetcherError::RateLimit),
+            status => Err(PriceFetcherError::Status(status.as_u16())),
+        }
+    }
+}