feat: add server error types and reqwest fetcher

crates/server/Cargo.toml

@@ -5,7 +5,12 @@ edition.workspace = true
 authors.workspace = true
 
 [dependencies]
+async-trait = "0.1"
+reqwest = "0.13"
 serde = { version = "1", features = ["derive"] }
+thiserror = "2"
+tokio = { version = "1", features = ["full"] }
+wasmtime = { version = "45", features = ["component-model"] }
 
 [dev-dependencies]
 serde_json = "1"

crates/server/src/error.rs

@@ -0,0 +1,22 @@
+use thiserror::Error;
+
+/// Errors from hosting/calling a WASM component.
+#[derive(Debug, Error)]
+pub enum HostError {
+    #[error("wasm error: {0}")]
+    Wasm(#[from] wasmtime::Error),
+    #[error("io error: {0}")]
+    Io(#[from] std::io::Error),
+}
+
+#[derive(Debug, Error)]
+pub enum FetchError {
+    #[error("request failed: {0}")]
+    Request(#[from] reqwest::Error),
+}
+
+#[derive(Debug, Error)]
+pub enum ConfigError {
+    #[error("invalid value for {key}: {message}")]
+    Invalid { key: String, message: String },
+}

crates/server/src/fetch.rs

@@ -0,0 +1,33 @@
+use std::time::Duration;
+
+use async_trait::async_trait;
+
+use crate::error::FetchError;
+use crate::model::FetchedResponse;
+use crate::service::Fetch;
+
+pub struct ReqwestFetcher {
+    client: reqwest::Client,
+}
+
+impl ReqwestFetcher {
+    pub fn new(timeout: Duration) -> Result<Self, FetchError> {
+        let client = reqwest::Client::builder()
+            .timeout(timeout)
+            .user_agent(concat!("whoareyou/", env!("CARGO_PKG_VERSION")))
+            .build()?;
+
+        Ok(Self { client })
+    }
+}
+
+#[async_trait]
+impl Fetch for ReqwestFetcher {
+    async fn fetch(&self, url: &str) -> Result<FetchedResponse, FetchError> {
+        let response = self.client.get(url).send().await?;
+        let status = response.status().as_u16();
+        let body = response.text().await?;
+
+        Ok(FetchedResponse { status, body })
+    }
+}

crates/server/src/lib.rs

@@ -1 +1,2 @@
+pub mod error;
 pub mod model;