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468//! Multi-provider web search engine with auto-fallback.
//!
//! Supports 4 providers: Tavily (AI-agent-native), Brave, Perplexity, and
//! DuckDuckGo (zero-config fallback). Auto mode cascades through available
//! providers based on configured API keys.
//!
//! All API keys use `Zeroizing<String>` via `resolve_api_key()` to auto-wipe
//! secrets from memory on drop.
use crate::web_cache::WebCache;
use crate::web_content::wrap_external_content;
use openfang_types::config::{SearchProvider, WebConfig};
use std::sync::Arc;
use tracing::{debug, warn};
use zeroize::Zeroizing;
/// Multi-provider web search engine.
pub struct WebSearchEngine {
config: WebConfig,
client: reqwest::Client,
cache: Arc<WebCache>,
}
/// Context that bundles both search and fetch engines for passing through the tool runner.
pub struct WebToolsContext {
pub search: WebSearchEngine,
pub fetch: crate::web_fetch::WebFetchEngine,
}
impl WebSearchEngine {
/// Create a new search engine from config with a shared cache.
pub fn new(config: WebConfig, cache: Arc<WebCache>) -> Self {
let client = reqwest::Client::builder()
.timeout(std::time::Duration::from_secs(15))
.build()
.unwrap_or_default();
Self {
config,
client,
cache,
}
}
/// Perform a web search using the configured provider (or auto-fallback).
pub async fn search(&self, query: &str, max_results: usize) -> Result<String, String> {
// Check cache first
let cache_key = format!("search:{}:{}", query, max_results);
if let Some(cached) = self.cache.get(&cache_key) {
debug!(query, "Search cache hit");
return Ok(cached);
}
let result = match self.config.search_provider {
SearchProvider::Brave => self.search_brave(query, max_results).await,
SearchProvider::Tavily => self.search_tavily(query, max_results).await,
SearchProvider::Perplexity => self.search_perplexity(query).await,
SearchProvider::DuckDuckGo => self.search_duckduckgo(query, max_results).await,
SearchProvider::Auto => self.search_auto(query, max_results).await,
};
// Cache successful results
if let Ok(ref content) = result {
self.cache.put(cache_key, content.clone());
}
result
}
/// Auto-select provider based on available API keys.
/// Priority: Tavily → Brave → Perplexity → DuckDuckGo
async fn search_auto(&self, query: &str, max_results: usize) -> Result<String, String> {
// Tavily first (AI-agent-native)
if resolve_api_key(&self.config.tavily.api_key_env).is_some() {
debug!("Auto: trying Tavily");
match self.search_tavily(query, max_results).await {
Ok(result) => return Ok(result),
Err(e) => warn!("Tavily failed, falling back: {e}"),
}
}
// Brave second
if resolve_api_key(&self.config.brave.api_key_env).is_some() {
debug!("Auto: trying Brave");
match self.search_brave(query, max_results).await {
Ok(result) => return Ok(result),
Err(e) => warn!("Brave failed, falling back: {e}"),
}
}
// Perplexity third
if resolve_api_key(&self.config.perplexity.api_key_env).is_some() {
debug!("Auto: trying Perplexity");
match self.search_perplexity(query).await {
Ok(result) => return Ok(result),
Err(e) => warn!("Perplexity failed, falling back: {e}"),
}
}
// DuckDuckGo always available as zero-config fallback
debug!("Auto: falling back to DuckDuckGo");
self.search_duckduckgo(query, max_results).await
}
/// Search via Brave Search API.
async fn search_brave(&self, query: &str, max_results: usize) -> Result<String, String> {
let api_key =
resolve_api_key(&self.config.brave.api_key_env).ok_or("Brave API key not set")?;
let mut params = vec![("q", query.to_string()), ("count", max_results.to_string())];
if !self.config.brave.country.is_empty() {
params.push(("country", self.config.brave.country.clone()));
}
if !self.config.brave.search_lang.is_empty() {
params.push(("search_lang", self.config.brave.search_lang.clone()));
}
if !self.config.brave.freshness.is_empty() {
params.push(("freshness", self.config.brave.freshness.clone()));
}
let resp = self
.client
.get("https://api.search.brave.com/res/v1/web/search")
.query(¶ms)
.header("X-Subscription-Token", api_key.as_str())
.header("Accept", "application/json")
.send()
.await
.map_err(|e| format!("Brave request failed: {e}"))?;
if !resp.status().is_success() {
return Err(format!("Brave API returned {}", resp.status()));
}
let body: serde_json::Value = resp
.json()
.await
.map_err(|e| format!("Brave JSON parse failed: {e}"))?;
let results = body["web"]["results"]
.as_array()
.cloned()
.unwrap_or_default();
if results.is_empty() {
return Ok(format!("No results found for '{query}' (Brave)."));
}
let mut output = format!("Search results for '{query}' (Brave):\n\n");
for (i, r) in results.iter().enumerate().take(max_results) {
let title = r["title"].as_str().unwrap_or("");
let url = r["url"].as_str().unwrap_or("");
let desc = r["description"].as_str().unwrap_or("");
output.push_str(&format!(
"{}. {}\n URL: {}\n {}\n\n",
i + 1,
title,
url,
desc
));
}
Ok(wrap_external_content("brave-search", &output))
}
/// Search via Tavily API (AI-agent-native search).
async fn search_tavily(&self, query: &str, max_results: usize) -> Result<String, String> {
let api_key =
resolve_api_key(&self.config.tavily.api_key_env).ok_or("Tavily API key not set")?;
let body = serde_json::json!({
"api_key": api_key.as_str(),
"query": query,
"search_depth": self.config.tavily.search_depth,
"max_results": max_results,
"include_answer": self.config.tavily.include_answer,
});
let resp = self
.client
.post("https://api.tavily.com/search")
.json(&body)
.send()
.await
.map_err(|e| format!("Tavily request failed: {e}"))?;
if !resp.status().is_success() {
return Err(format!("Tavily API returned {}", resp.status()));
}
let data: serde_json::Value = resp
.json()
.await
.map_err(|e| format!("Tavily JSON parse failed: {e}"))?;
let mut output = format!("Search results for '{query}' (Tavily):\n\n");
// Include AI-generated answer if available
if let Some(answer) = data["answer"].as_str() {
if !answer.is_empty() {
output.push_str(&format!("AI Summary: {answer}\n\n"));
}
}
let results = data["results"].as_array().cloned().unwrap_or_default();
for (i, r) in results.iter().enumerate().take(max_results) {
let title = r["title"].as_str().unwrap_or("");
let url = r["url"].as_str().unwrap_or("");
let content = r["content"].as_str().unwrap_or("");
output.push_str(&format!(
"{}. {}\n URL: {}\n {}\n\n",
i + 1,
title,
url,
content
));
}
if results.is_empty() && !output.contains("AI Summary") {
return Ok(format!("No results found for '{query}' (Tavily)."));
}
Ok(wrap_external_content("tavily-search", &output))
}
/// Search via Perplexity AI (chat completions endpoint).
async fn search_perplexity(&self, query: &str) -> Result<String, String> {
let api_key = resolve_api_key(&self.config.perplexity.api_key_env)
.ok_or("Perplexity API key not set")?;
let body = serde_json::json!({
"model": self.config.perplexity.model,
"messages": [
{"role": "user", "content": query}
],
});
let resp = self
.client
.post("https://api.perplexity.ai/chat/completions")
.header("Authorization", format!("Bearer {}", api_key.as_str()))
.json(&body)
.send()
.await
.map_err(|e| format!("Perplexity request failed: {e}"))?;
if !resp.status().is_success() {
return Err(format!("Perplexity API returned {}", resp.status()));
}
let data: serde_json::Value = resp
.json()
.await
.map_err(|e| format!("Perplexity JSON parse failed: {e}"))?;
let answer = data["choices"][0]["message"]["content"]
.as_str()
.unwrap_or("")
.to_string();
if answer.is_empty() {
return Ok(format!("No answer for '{query}' (Perplexity)."));
}
let mut output = format!("Search results for '{query}' (Perplexity AI):\n\n{answer}\n");
// Include citations if available
if let Some(citations) = data["citations"].as_array() {
output.push_str("\nSources:\n");
for (i, c) in citations.iter().enumerate() {
if let Some(url) = c.as_str() {
output.push_str(&format!(" {}. {}\n", i + 1, url));
}
}
}
Ok(wrap_external_content("perplexity-search", &output))
}
/// Search via DuckDuckGo HTML (no API key needed).
async fn search_duckduckgo(&self, query: &str, max_results: usize) -> Result<String, String> {
debug!(query, "Searching via DuckDuckGo HTML");
let resp = self
.client
.get("https://html.duckduckgo.com/html/")
.query(&[("q", query)])
.header("User-Agent", "Mozilla/5.0 (compatible; OpenFangAgent/0.1)")
.send()
.await
.map_err(|e| format!("DuckDuckGo request failed: {e}"))?;
let body = resp
.text()
.await
.map_err(|e| format!("Failed to read DDG response: {e}"))?;
let results = parse_ddg_results(&body, max_results);
if results.is_empty() {
return Ok(format!("No results found for '{query}'."));
}
let mut output = format!("Search results for '{query}':\n\n");
for (i, (title, url, snippet)) in results.iter().enumerate() {
output.push_str(&format!(
"{}. {}\n URL: {}\n {}\n\n",
i + 1,
title,
url,
snippet
));
}
Ok(output)
}
}
// ---------------------------------------------------------------------------
// DuckDuckGo HTML parser (moved from tool_runner.rs)
// ---------------------------------------------------------------------------
/// Parse DuckDuckGo HTML search results into (title, url, snippet) tuples.
pub fn parse_ddg_results(html: &str, max: usize) -> Vec<(String, String, String)> {
let mut results = Vec::new();
for chunk in html.split("class=\"result__a\"") {
if results.len() >= max {
break;
}
if !chunk.contains("href=") {
continue;
}
let url = extract_between(chunk, "href=\"", "\"")
.unwrap_or_default()
.to_string();
let actual_url = if url.contains("uddg=") {
url.split("uddg=")
.nth(1)
.and_then(|u| u.split('&').next())
.map(urldecode)
.unwrap_or(url)
} else {
url
};
let title = extract_between(chunk, ">", "</a>")
.map(strip_html_tags)
.unwrap_or_default();
let snippet = if let Some(snip_start) = chunk.find("class=\"result__snippet\"") {
let after = &chunk[snip_start..];
extract_between(after, ">", "</a>")
.or_else(|| extract_between(after, ">", "</"))
.map(strip_html_tags)
.unwrap_or_default()
} else {
String::new()
};
if !title.is_empty() && !actual_url.is_empty() {
results.push((title, actual_url, snippet));
}
}
results
}
/// Extract text between two delimiters.
pub fn extract_between<'a>(text: &'a str, start: &str, end: &str) -> Option<&'a str> {
let start_idx = text.find(start)? + start.len();
let remaining = &text[start_idx..];
let end_idx = remaining.find(end)?;
Some(&remaining[..end_idx])
}
/// Strip HTML tags from a string.
pub fn strip_html_tags(s: &str) -> String {
let mut result = String::with_capacity(s.len());
let mut in_tag = false;
for ch in s.chars() {
match ch {
'<' => in_tag = true,
'>' => in_tag = false,
_ if !in_tag => result.push(ch),
_ => {}
}
}
result
.replace("&", "&")
.replace("<", "<")
.replace(">", ">")
.replace(""", "\"")
.replace("'", "'")
.replace(" ", " ")
.replace("'", "'")
}
/// Simple percent-decode for URLs.
pub fn urldecode(s: &str) -> String {
let mut result = String::with_capacity(s.len());
let mut chars = s.chars();
while let Some(ch) = chars.next() {
if ch == '%' {
let hex: String = chars.by_ref().take(2).collect();
if let Ok(byte) = u8::from_str_radix(&hex, 16) {
result.push(byte as char);
} else {
result.push('%');
result.push_str(&hex);
}
} else if ch == '+' {
result.push(' ');
} else {
result.push(ch);
}
}
result
}
/// Resolve an API key from an environment variable name.
/// Returns `Zeroizing<String>` that auto-wipes from memory on drop.
fn resolve_api_key(env_var: &str) -> Option<Zeroizing<String>> {
std::env::var(env_var)
.ok()
.filter(|v| !v.is_empty())
.map(Zeroizing::new)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_format_with_results() {
let html = r#"junk class="result__a" href="https://example.com">Example</a> class="result__snippet">A snippet</a>"#;
let results = parse_ddg_results(html, 5);
assert_eq!(results.len(), 1);
assert_eq!(results[0].0, "Example");
assert_eq!(results[0].1, "https://example.com");
assert_eq!(results[0].2, "A snippet");
}
#[test]
fn test_format_empty() {
let results = parse_ddg_results("<html><body>No results</body></html>", 5);
assert!(results.is_empty());
}
#[test]
fn test_format_with_answer() {
// Tavily-style answer formatting is tested via the DDG parser as basic coverage
let html = r#"before class="result__a" href="https://rust-lang.org">Rust</a> class="result__snippet">Systems programming</a> class="result__a" href="https://go.dev">Go</a> class="result__snippet">Another language</a>"#;
let results = parse_ddg_results(html, 10);
assert_eq!(results.len(), 2);
}
#[test]
fn test_ddg_parser_preserved() {
// Ensure the parser handles URL-encoded DDG redirect URLs
let html = r#"x class="result__a" href="/l/?uddg=https%3A%2F%2Fexample.com&rut=abc">Title</a> class="result__snippet">Desc</a>"#;
let results = parse_ddg_results(html, 5);
assert_eq!(results.len(), 1);
assert_eq!(results[0].1, "https://example.com");
}
}