Implement price-feed feature by zahorodnyi · Pull Request #49 · Blockstream/simplicity-dex

zahorodnyi · 2026-01-15T18:25:10Z

Usage: cargo run -p cli-client price-feed

Fix: #40

zahorodnyi · 2026-01-15T18:48:44Z

@greptile review the PR according to the CONTRIBUTION.md

greptile-apps · 2026-01-15T18:51:33Z

Greptile Overview

Greptile Summary

This PR adds BTC/USD price fetching functionality from CoinGecko API, displaying the current Bitcoin price in the positions view.

Key changes:

New price_fetcher module with trait-based design for fetching cryptocurrency prices
CoingeckoPriceFetcher implementation with proper timeout (5s) and error handling
Integration into positions display using tokio::task::spawn_blocking to avoid blocking the async runtime
Comprehensive error handling for rate limits, network errors, and parse failures

Addressed from previous feedback:

Uses spawn_blocking for synchronous HTTP calls ✓
Improved error handling with specific error types ✓
Fixed currency symbol placement ($ prefix) ✓
Derives Default for zero-field struct ✓

The implementation is clean, follows Rust best practices, and properly handles the blocking I/O in an async context.

Confidence Score: 4.5/5

This PR is safe to merge with minimal risk
The implementation is clean and addresses all major concerns from previous reviews. The code properly handles blocking I/O, has comprehensive error handling, and follows established patterns in the codebase. Score is not 5 due to lack of unit tests, but this is acceptable per developer feedback.
No files require special attention

Important Files Changed

Filename	Overview
crates/cli-client/src/price_fetcher.rs	New module implementing BTC/USD price fetching from CoinGecko with proper error handling and timeout
crates/cli-client/src/cli/positions.rs	Integrates price fetcher into positions display with spawn_blocking and proper error handling

Sequence Diagram

sequenceDiagram
    participant User
    participant CLI
    participant Positions
    participant PriceFetcher
    participant CoinGecko

    User->>CLI: cargo run positions
    CLI->>Positions: run_positions()
    Positions->>PriceFetcher: spawn_blocking(fetch_btc_usd_price)
    PriceFetcher->>CoinGecko: GET /api/v3/simple/price
    alt Success (200)
        CoinGecko-->>PriceFetcher: {"bitcoin":{"usd":price}}
        PriceFetcher-->>Positions: Ok(price)
        Positions->>User: Display "$price"
    else Rate Limited (429)
        CoinGecko-->>PriceFetcher: 429 status
        PriceFetcher-->>Positions: Err(RateLimit)
        Positions->>User: Display "Rate limit exceeded"
    else Other Error
        CoinGecko-->>PriceFetcher: Error/timeout
        PriceFetcher-->>Positions: Err(error)
        Positions->>User: Display "Price fetcher service unavailable"
    end
    Positions->>User: Display positions with price info

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

crates/cli-client/src/price_fetcher.rs

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

greptile-apps · 2026-01-16T15:48:03Z

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zahorodnyi · 2026-01-29T11:44:11Z

@greptile review the PR according to the CONTRIBUTION.md

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KyrylR · 2026-01-29T11:59:16Z

@greptile review the PR according to the CONTRIBUTION.md

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crates/cli-client/src/price_fetcher.rs

crates/cli-client/Cargo.toml

crates/cli-client/src/price_fetcher.rs

zahorodnyi · 2026-01-29T16:05:16Z

@greptile review the PR according to the CONTRIBUTION.md

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

KyrylR · 2026-01-30T18:16:17Z

crates/cli-client/Cargo.toml

 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"] }


Use minreq instead

KyrylR · 2026-01-30T18:17:09Z

crates/cli-client/src/price_fetcher.rs

+
+#[derive(Deserialize)]
+struct BitcoinPrice {
+    usd: Decimal,


Why do we need rust_decimal::Decimal?

KyrylR · 2026-01-30T18:17:40Z

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

+use rust_decimal::Decimal;
+
+pub async fn fetch_btc_usd_price<T: PriceFetcher>(fetcher: &T) -> Result<Decimal, Error> {
+    Ok(fetcher.fetch_price().await?)


Suggested change

Ok(fetcher.fetch_price().await?)

fetcher.fetch_price().await

KyrylR · 2026-01-30T18:18:48Z

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

+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(())
+}


What is the purpose of this function?

The purpose is to show the price in the terminal using the command cargo run -- price-feed (according to what was written in the original issue: #40). Don’t we need it?

KyrylR · 2026-01-30T18:19:36Z

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

+pub async fn fetch_btc_usd_price<T: PriceFetcher>(fetcher: &T) -> Result<Decimal, Error> {
+    Ok(fetcher.fetch_price().await?)
+}
+


Let's move this to the: crates/cli-client/src/price_fetcher.rs

zahorodnyi · 2026-02-02T16:56:57Z

@greptile review the PR according to the CONTRIBUTION.md

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greptile-apps · 2026-02-02T16:59:08Z

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

+        let fetcher = CoingeckoPriceFetcher::new();
+        let btc_price = fetch_btc_usd_price(&fetcher)
+            .map(|x| format!("{x:.2}$"))
+            .unwrap_or("'Rate limit exceed'".to_string());


[P1] Swallows non-rate-limit errors as "rate limit"

fetch_btc_usd_price(&fetcher) can fail for reasons other than a 429 (e.g., no network, DNS issues, CoinGecko 5xx, JSON shape changes), but this unwrap_or("'Rate limit exceed'") prints the same message for all failures, which makes debugging and user guidance misleading. Consider matching on the error and only mapping PriceFetcherError::RateLimit to that message, while showing (or logging) other errors.

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/cli/positions.rs Line: 31:34 Comment: [P1] Swallows non-rate-limit errors as "rate limit" `fetch_btc_usd_price(&fetcher)` can fail for reasons other than a 429 (e.g., no network, DNS issues, CoinGecko 5xx, JSON shape changes), but this `unwrap_or("'Rate limit exceed'")` prints the same message for all failures, which makes debugging and user guidance misleading. Consider matching on the error and only mapping `PriceFetcherError::RateLimit` to that message, while showing (or logging) other errors. How can I resolve this? If you propose a fix, please make it concise.

greptile-apps · 2026-02-02T16:59:09Z

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

+        let fetcher = CoingeckoPriceFetcher::new();
+        let btc_price = fetch_btc_usd_price(&fetcher)
+            .map(|x| format!("{x:.2}$"))
+            .unwrap_or("'Rate limit exceed'".to_string());


[P3] User-facing string has typo/quoting

"'Rate limit exceed'" reads like a debug string (extra quotes) and has a grammar typo; it will show up in normal CLI output. Consider a cleaner message like "Rate limit exceeded".

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/cli/positions.rs Line: 34:34 Comment: [P3] User-facing string has typo/quoting `"'Rate limit exceed'"` reads like a debug string (extra quotes) and has a grammar typo; it will show up in normal CLI output. Consider a cleaner message like `"Rate limit exceeded"`. How can I resolve this? If you propose a fix, please make it concise.

greptile-apps · 2026-02-02T16:59:10Z

crates/cli-client/src/price_fetcher.rs

+pub trait PriceFetcher {
+    fn fetch_price(&self) -> Result<f64, Error>;
+}


[P1] Trait returns crate-wide Error instead of PriceFetcherError

PriceFetcher::fetch_price() returning Result<f64, Error> makes the trait harder to reuse and mock because it couples the fetcher layer to the entire CLI error enum. Since this module already defines PriceFetcherError, consider making the trait return Result<f64, PriceFetcherError> and converting to crate::error::Error at the CLI boundary.

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/price_fetcher.rs Line: 27:29 Comment: [P1] Trait returns crate-wide `Error` instead of `PriceFetcherError` `PriceFetcher::fetch_price()` returning `Result<f64, Error>` makes the trait harder to reuse and mock because it couples the fetcher layer to the entire CLI error enum. Since this module already defines `PriceFetcherError`, consider making the trait return `Result<f64, PriceFetcherError>` and converting to `crate::error::Error` at the CLI boundary. Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time! How can I resolve this? If you propose a fix, please make it concise.

zahorodnyi · 2026-02-02T17:32:22Z

@greptile review the PR according to the CONTRIBUTION.md

greptile-apps

_{2 files reviewed, 3 comments}

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greptile-apps · 2026-02-02T17:35:46Z

crates/cli-client/src/price_fetcher.rs

+pub trait PriceFetcher {
+    fn fetch_price(&self) -> Result<f64, PriceFetcherError>;


Trait uses synchronous blocking HTTP in async context. fetch_price() calls blocking minreq::get() which blocks the tokio runtime thread. Either mark trait method as async or use tokio::task::spawn_blocking() when calling it.

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/price_fetcher.rs Line: 26:27 Comment: Trait uses synchronous blocking HTTP in async context. `fetch_price()` calls blocking `minreq::get()` which blocks the tokio runtime thread. Either mark trait method as async or use `tokio::task::spawn_blocking()` when calling it. How can I resolve this? If you propose a fix, please make it concise.

greptile-apps · 2026-02-02T17:35:47Z

crates/cli-client/src/price_fetcher.rs

+    pub fn new() -> Self {
+        Self {}
+    }


Missing Default trait implementation. new() creates empty struct - derive or implement Default instead.

Suggested change

pub fn new() -> Self {

Self {}

}

#[must_use]

pub const fn new() -> Self {

Self

}

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/price_fetcher.rs Line: 36:38 Comment: Missing `Default` trait implementation. `new()` creates empty struct - derive or implement `Default` instead. ```suggestion #[must_use] pub const fn new() -> Self { Self } ``` Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time! How can I resolve this? If you propose a fix, please make it concise.

greptile-apps · 2026-02-02T17:35:48Z

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

+        let fetcher = CoingeckoPriceFetcher::new();
+        let btc_price = match fetch_btc_usd_price(&fetcher) {
+            Ok(price) => format!("{price:.2}$"),
+            Err(PriceFetcherError::RateLimit) => "Rate limit exceeded".to_string(),
+            Err(e) => {
+                eprintln!("Debug error: {e}");
+                "Price fetcher service unavailable".to_string()
+            }
+        };


Blocking HTTP call in async function. fetch_btc_usd_price() uses synchronous minreq and will block the tokio runtime thread. Wrap in tokio::task::spawn_blocking():

let btc_price = match tokio::task::spawn_blocking(move || fetch_btc_usd_price(&fetcher)).await { Ok(Ok(price)) => format!("{price:.2}$"), Ok(Err(PriceFetcherError::RateLimit)) => "Rate limit exceeded".to_string(), Ok(Err(e)) => { eprintln!("Debug error: {e}"); "Price fetcher service unavailable".to_string() } Err(_) => "Price fetcher service unavailable".to_string(), };

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/cli/positions.rs Line: 31:39 Comment: Blocking HTTP call in async function. `fetch_btc_usd_price()` uses synchronous `minreq` and will block the tokio runtime thread. Wrap in `tokio::task::spawn_blocking()`: ``` let btc_price = match tokio::task::spawn_blocking(move || fetch_btc_usd_price(&fetcher)).await { Ok(Ok(price)) => format!("{price:.2}$"), Ok(Err(PriceFetcherError::RateLimit)) => "Rate limit exceeded".to_string(), Ok(Err(e)) => { eprintln!("Debug error: {e}"); "Price fetcher service unavailable".to_string() } Err(_) => "Price fetcher service unavailable".to_string(), }; ``` How can I resolve this? If you propose a fix, please make it concise.

zahorodnyi · 2026-02-02T18:07:21Z

@greptile review the PR according to the CONTRIBUTION.md

greptile-apps

_{2 files reviewed, 2 comments}

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greptile-apps · 2026-02-02T18:11:03Z

crates/cli-client/src/price_fetcher.rs

+pub struct CoingeckoPriceFetcher;
+
+impl CoingeckoPriceFetcher {
+    const URL: &'static str = "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd&precision=8";
+    const TIMEOUT_SECS: u64 = 5;
+
+    #[must_use]
+    pub fn new() -> Self {
+        Self
+    }


derive Default instead of implementing new() for zero-field struct

Suggested change

pub struct CoingeckoPriceFetcher;

impl CoingeckoPriceFetcher {

const URL: &'static str = "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd&precision=8";

const TIMEOUT_SECS: u64 = 5;

#[must_use]

pub fn new() -> Self {

Self

}

#[derive(Default)]

pub struct CoingeckoPriceFetcher;

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/price_fetcher.rs Line: 32:41 Comment: derive `Default` instead of implementing `new()` for zero-field struct ```suggestion #[derive(Default)] pub struct CoingeckoPriceFetcher; ``` Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time! How can I resolve this? If you propose a fix, please make it concise.

greptile-apps · 2026-02-02T18:11:04Z

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

+            .unwrap_or_else(|e| Err(PriceFetcherError::Internal(e.to_string())));
+
+        let btc_price = match btc_result {
+            Ok(price) => format!("{price:.2}$"),


inconsistent currency symbol placement - should be ${price:.2} (USD convention)

Suggested change

Ok(price) => format!("{price:.2}$"),

Ok(price) => format!("${price:.2}"),

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review. Path: crates/cli-client/src/cli/positions.rs Line: 37:37 Comment: inconsistent currency symbol placement - should be `${price:.2}` (USD convention) ```suggestion Ok(price) => format!("${price:.2}"), ``` Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time! How can I resolve this? If you propose a fix, please make it concise.

zahorodnyi · 2026-02-03T12:09:12Z

@greptile review the PR according to the CONTRIBUTION.md

KyrylR · 2026-02-04T08:13:38Z

Rebase onto main pls, also bump to the last simplicityhl-core version and fix compilation errors

KyrylR · 2026-02-04T13:16:22Z

crates/cli-client/src/price_fetcher.rs

+        let price = match resp.status_code {
+            200 => resp
+                .json::<BitcoinResponse>()
+                .map(|data| data.bitcoin.usd)
+                .map_err(|e| PriceFetcherError::Parse(e.to_string()))?,
+            429 => return Err(PriceFetcherError::RateLimit),
+            status => return Err(PriceFetcherError::Status(status)),
+        };
+
+        Ok(price)


Suggested change

let price = match resp.status_code {

200 => resp

.json::<BitcoinResponse>()

.map(|data| data.bitcoin.usd)

.map_err(|e| PriceFetcherError::Parse(e.to_string()))?,

429 => return Err(PriceFetcherError::RateLimit),

status => return Err(PriceFetcherError::Status(status)),

};

Ok(price)

match resp.status_code {

200 => resp

.json::<BitcoinResponse>()

.map(|data| data.bitcoin.usd)

.map_err(|e| PriceFetcherError::Parse(e.to_string()))?,

429 => Err(PriceFetcherError::RateLimit),

status => Err(PriceFetcherError::Status(status)),

}

chore: * bump simplicityhl version from 0.4.0 -> 0.4.1 * remove Cargo.lock from .gitignore

KyrylR

ACK 236885d

zahorodnyi self-assigned this Jan 15, 2026

zahorodnyi requested a review from KyrylR as a code owner January 15, 2026 18:25

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Implement a minimal BTC/USD price feed feature

236885d

chore: * bump simplicityhl version from 0.4.0 -> 0.4.1 * remove Cargo.lock from .gitignore

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KyrylR deleted the feature/price-feed branch February 4, 2026 14:41

		pub trait PriceFetcher {
		fn fetch_price(&self) -> Result<f64, PriceFetcherError>;

	Ok(price) => format!("{price:.2}$"),
	Ok(price) => format!("${price:.2}"),

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Greptile Overview

Greptile Summary

Confidence Score: 4.5/5

Important Files Changed

Sequence Diagram

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