[esplora] Support proxies in EsploraBlockchain

src/blockchain/esplora/reqwest.rs

@@ -333,6 +333,17 @@ pub struct EsploraBlockchainConfig {
     ///
     /// eg. `https://blockstream.info/api/`
     pub base_url: String,
+    /// Optional URL of the proxy to use to make requests to the Esplora server
+    ///
+    /// The string should be formatted as: `<protocol>://<user>:<password>@host:<port>`.
+    ///
+    /// Note that the format of this value and the supported protocols change slightly between the
+    /// sync version of esplora (using `ureq`) and the async version (using `reqwest`). For more
+    /// details check with the documentation of the two crates. Both of them are compiled with
+    /// the `socks` feature enabled.
+    ///
+    /// The proxy is ignored when targeting `wasm32`.
+    pub proxy: Option<String>,
     /// Number of parallel requests sent to the esplora service (default: 4)
     pub concurrency: Option<u8>,
     /// Stop searching addresses for transactions after finding an unused gap of this length.
@@ -343,10 +354,19 @@ impl ConfigurableBlockchain for EsploraBlockchain {
     type Config = EsploraBlockchainConfig;
 
     fn from_config(config: &Self::Config) -> Result<Self, Error> {
+        let map_e = |e: reqwest::Error| Error::Esplora(Box::new(e.into()));
+
         let mut blockchain = EsploraBlockchain::new(config.base_url.as_str(), config.stop_gap);
         if let Some(concurrency) = config.concurrency {
             blockchain.url_client.concurrency = concurrency;
-        };
+        }
+        #[cfg(not(target_arch = "wasm32"))]
+        if let Some(proxy) = &config.proxy {
+            blockchain.url_client.client = Client::builder()
+                .proxy(reqwest::Proxy::all(proxy).map_err(map_e)?)
+                .build()
+                .map_err(map_e)?;
+        }
         Ok(blockchain)
     }
 }