fix: load and validate required env vars at startup (#24)

.env.example

@@ -1,12 +1,13 @@
-# Copy this file to .env and customize values as needed for your local
-# development or CI environment.
+# Copy this file to .env and replace placeholder values.
 
-# Soroban network selection (profile name). Valid values: testnet, mainnet, sandbox
-SOROBAN_NETWORK=testnet
+# Target Stellar network (for example: testnet, mainnet).
+STELLAR_NETWORK=testnet
 
-# Override the RPC endpoint and network passphrase if necessary
-SOROBAN_RPC_URL=https://rpc.testnet.soroban.stellar.org
-SOROBAN_NETWORK_PASSPHRASE="Test SDF Network ; September 2015"
+# Platform account secret seed used for signing platform transactions.
+STELLAR_PLATFORM_SECRET=SBXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+
+# Horizon REST API endpoint for the selected network.
+HORIZON_URL=https://horizon-testnet.stellar.org
 
-# Example keypair file path; tools may read this
-# SOROBAN_KEY_FILE=./keys/contract-key.json
+# Soroban RPC endpoint for the selected network.
+SOROBAN_RPC_URL=https://rpc.testnet.soroban.stellar.org

Cargo.toml

@@ -25,4 +25,5 @@ tokio       = { version = "1", features = ["rt-multi-thread", "macros"] }
 stellar-strkey  = "0.0.8"
 ed25519-dalek   = "2"
 tracing     = "0.1"
-tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
+dotenvy = "0.15"

src/config.rs

@@ -0,0 +1,43 @@
+use std::env;
+
+use thiserror::Error;
+
+#[derive(Debug, Clone)]
+pub struct Config {
+    pub stellar_network: String,
+    pub stellar_platform_secret: String,
+    pub horizon_url: String,
+    pub soroban_rpc_url: String,
+}
+
+#[derive(Debug, Error)]
+pub enum ConfigError {
+    #[error("missing required environment variable: {0}")]
+    MissingEnvVar(&'static str),
+
+    #[error("environment variable {name} cannot be empty")]
+    EmptyEnvVar { name: &'static str },
+}
+
+impl Config {
+    pub fn from_env() -> Result<Self, ConfigError> {
+        dotenvy::dotenv().ok();
+
+        Ok(Self {
+            stellar_network: read_required_env("STELLAR_NETWORK")?,
+            stellar_platform_secret: read_required_env("STELLAR_PLATFORM_SECRET")?,
+            horizon_url: read_required_env("HORIZON_URL")?,
+            soroban_rpc_url: read_required_env("SOROBAN_RPC_URL")?,
+        })
+    }
+}
+
+fn read_required_env(name: &'static str) -> Result<String, ConfigError> {
+    let value = env::var(name).map_err(|_| ConfigError::MissingEnvVar(name))?;
+
+    if value.trim().is_empty() {
+        return Err(ConfigError::EmptyEnvVar { name });
+    }
+
+    Ok(value)
+}

src/main.rs

@@ -1,8 +1,14 @@
+pub mod config;
 pub mod errors;
 
 pub mod friendbot;
 pub mod horizon;
 mod setup;
 pub mod utils;
 
-fn main() {}
+fn main() {
+    if let Err(err) = config::Config::from_env() {
+        eprintln!("Startup configuration error: {err}");
+        std::process::exit(1);
+    }
+}