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//! The `duckduckgo` module handles the scraping of results from the duckduckgo search engine
//! by querying the upstream duckduckgo search engine with user provided query and with a page
//! number if provided.
use std::collections::HashMap;
use reqwest::header::{HeaderMap, CONTENT_TYPE, COOKIE, REFERER, USER_AGENT};
use scraper::{Html, Selector};
use crate::results::aggregation_models::RawSearchResult;
use super::engine_models::{EngineError, SearchEngine};
use error_stack::{IntoReport, Report, Result, ResultExt};
/// A new DuckDuckGo engine type defined in-order to implement the `SearchEngine` trait which allows to
/// reduce code duplication as well as allows to create vector of different search engines easily.
pub struct DuckDuckGo;
#[async_trait::async_trait]
impl SearchEngine for DuckDuckGo {
/// This function scrapes results from the upstream engine duckduckgo and puts all the scraped
/// results like title, visiting_url (href in html),engine (from which engine it was fetched from)
/// and description in a RawSearchResult and then adds that to HashMap whose keys are url and
/// values are RawSearchResult struct and then returns it within a Result enum.
///
/// # Arguments
///
/// * `query` - Takes the user provided query to query to the upstream search engine with.
/// * `page` - Takes an u32 as an argument.
/// * `user_agent` - Takes a random user agent string as an argument.
///
/// # Errors
///
/// Returns an `EngineErrorKind` if the user is not connected to the internet or if their is failure to
/// reach the above `upstream search engine` page or if the `upstream search engine` is unable to
/// provide results for the requested search query and also returns error if the scraping selector
/// or HeaderMap fails to initialize.
async fn results(
&self,
query: String,
page: u32,
user_agent: String,
) -> Result<HashMap<String, RawSearchResult>, EngineError> {
// Page number can be missing or empty string and so appropriate handling is required
// so that upstream server recieves valid page number.
let url: String = match page {
1 => {
format!("https://html.duckduckgo.com/html/?q={query}&s=&dc=&v=1&o=json&api=/d.js")
}
_ => {
format!(
"https://duckduckgo.com/html/?q={}&s={}&dc={}&v=1&o=json&api=/d.js",
query,
(page / 2 + (page % 2)) * 30,
(page / 2 + (page % 2)) * 30 + 1
)
}
};
// initializing HeaderMap and adding appropriate headers.
let mut header_map = HeaderMap::new();
header_map.insert(
USER_AGENT,
user_agent
.parse()
.into_report()
.change_context(EngineError::UnexpectedError)?,
);
header_map.insert(
REFERER,
"https://google.com/"
.parse()
.into_report()
.change_context(EngineError::UnexpectedError)?,
);
header_map.insert(
CONTENT_TYPE,
"application/x-www-form-urlencoded"
.parse()
.into_report()
.change_context(EngineError::UnexpectedError)?,
);
header_map.insert(
COOKIE,
"kl=wt-wt"
.parse()
.into_report()
.change_context(EngineError::UnexpectedError)?,
);
let document: Html = Html::parse_document(
&DuckDuckGo::fetch_html_from_upstream(self, url, header_map).await?,
);
let no_result: Selector = Selector::parse(".no-results")
.map_err(|_| Report::new(EngineError::UnexpectedError))
.attach_printable_lazy(|| format!("invalid CSS selector: {}", ".no-results"))?;
if document.select(&no_result).next().is_some() {
return Err(Report::new(EngineError::EmptyResultSet));
}
let results: Selector = Selector::parse(".result")
.map_err(|_| Report::new(EngineError::UnexpectedError))
.attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result"))?;
let result_title: Selector = Selector::parse(".result__a")
.map_err(|_| Report::new(EngineError::UnexpectedError))
.attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__a"))?;
let result_url: Selector = Selector::parse(".result__url")
.map_err(|_| Report::new(EngineError::UnexpectedError))
.attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__url"))?;
let result_desc: Selector = Selector::parse(".result__snippet")
.map_err(|_| Report::new(EngineError::UnexpectedError))
.attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__snippet"))?;
// scrape all the results from the html
Ok(document
.select(&results)
.map(|result| {
RawSearchResult::new(
result
.select(&result_title)
.next()
.unwrap()
.inner_html()
.trim()
.to_string(),
format!(
"https://{}",
result
.select(&result_url)
.next()
.unwrap()
.inner_html()
.trim()
),
result
.select(&result_desc)
.next()
.unwrap()
.inner_html()
.trim()
.to_string(),
vec!["duckduckgo".to_string()],
)
})
.map(|search_result| (search_result.visiting_url.clone(), search_result))
.collect())
}
}
|