feat: add Brave Search API client module

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/services/brave_search.rs

@@ -0,0 +1,148 @@
+//! Brave Search API client.
+//!
+//! Calls the Brave Web Search API and returns structured results.
+//! Used as an alternative to LLM web search in Phase 2.
+
+use crate::errors::AppError;
+use serde::Deserialize;
+
+/// A single result from the Brave Search API.
+#[derive(Debug, Clone)]
+pub struct BraveResult {
+    pub title: String,
+    pub url: String,
+    pub description: String,
+}
+
+/// Map `max_age_days` to Brave's `freshness` parameter.
+fn freshness_from_days(max_age_days: i32) -> &'static str {
+    match max_age_days {
+        d if d <= 1 => "pd",
+        d if d <= 7 => "pw",
+        d if d <= 30 => "pm",
+        _ => "py",
+    }
+}
+
+/// Brave API response structures (only the fields we need).
+#[derive(Deserialize)]
+struct BraveSearchResponse {
+    web: Option<BraveWebResults>,
+}
+
+#[derive(Deserialize)]
+struct BraveWebResults {
+    results: Option<Vec<BraveWebResult>>,
+}
+
+#[derive(Deserialize)]
+struct BraveWebResult {
+    title: Option<String>,
+    url: Option<String>,
+    description: Option<String>,
+}
+
+/// Search the Brave Web Search API.
+pub async fn search(
+    http_client: &reqwest::Client,
+    api_key: &str,
+    query: &str,
+    count: u32,
+    max_age_days: i32,
+) -> Result<Vec<BraveResult>, AppError> {
+    let freshness = freshness_from_days(max_age_days);
+
+    let response = http_client
+        .get("https://api.search.brave.com/res/v1/web/search")
+        .header("X-Subscription-Token", api_key)
+        .header("Accept", "application/json")
+        .query(&[
+            ("q", query),
+            ("count", &count.to_string()),
+            ("freshness", freshness),
+            ("search_lang", "fr"),
+        ])
+        .send()
+        .await
+        .map_err(|e| {
+            tracing::warn!(error = %e, "Brave Search API request failed");
+            AppError::Internal(anyhow::anyhow!("Brave Search API request failed: {}", e))
+        })?;
+
+    if !response.status().is_success() {
+        let status = response.status();
+        let body = response.text().await.unwrap_or_default();
+        tracing::warn!(status = %status, body = %body, "Brave Search API error");
+        return Err(AppError::Internal(anyhow::anyhow!(
+            "Brave Search API returned status {}: {}",
+            status,
+            body
+        )));
+    }
+
+    let api_response: BraveSearchResponse = response.json().await.map_err(|e| {
+        AppError::Internal(anyhow::anyhow!("Failed to parse Brave Search response: {}", e))
+    })?;
+
+    let results = api_response
+        .web
+        .and_then(|w| w.results)
+        .unwrap_or_default()
+        .into_iter()
+        .filter_map(|r| {
+            let url = r.url?;
+            if url.is_empty() {
+                return None;
+            }
+            Some(BraveResult {
+                title: r.title.unwrap_or_default(),
+                url,
+                description: r.description.unwrap_or_default(),
+            })
+        })
+        .collect();
+
+    Ok(results)
+}
+
+/// Test the Brave Search API key with a simple query.
+pub async fn test_api_key(
+    http_client: &reqwest::Client,
+    api_key: &str,
+) -> Result<(), AppError> {
+    let response = http_client
+        .get("https://api.search.brave.com/res/v1/web/search")
+        .header("X-Subscription-Token", api_key)
+        .header("Accept", "application/json")
+        .query(&[("q", "test"), ("count", "1")])
+        .send()
+        .await
+        .map_err(|e| AppError::Internal(anyhow::anyhow!("Brave API request failed: {}", e)))?;
+
+    if response.status().is_success() {
+        Ok(())
+    } else {
+        let status = response.status();
+        Err(AppError::BadRequest(format!(
+            "Brave Search API returned status {}. Check your API key.",
+            status
+        )))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn freshness_mapping() {
+        assert_eq!(freshness_from_days(1), "pd");
+        assert_eq!(freshness_from_days(0), "pd");
+        assert_eq!(freshness_from_days(7), "pw");
+        assert_eq!(freshness_from_days(3), "pw");
+        assert_eq!(freshness_from_days(30), "pm");
+        assert_eq!(freshness_from_days(14), "pm");
+        assert_eq!(freshness_from_days(31), "py");
+        assert_eq!(freshness_from_days(365), "py");
+    }
+}

backend/src/services/mod.rs

@@ -1,4 +1,5 @@
 pub mod auth;
+pub mod brave_search;
 pub mod csv;
 pub mod email;
 pub mod encryption;