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//! This modules provides helper functionalities for parsing a html document into internal SearchResult.
use crate::models::{aggregation_models::SearchResult, engine_models::EngineError};
use error_stack::{Report, Result};
use scraper::{html::Select, ElementRef, Html, Selector};
/// A html search result parser, based on a predefined CSS selectors.
pub struct SearchResultParser {
/// selector to locate the element which is displayed, if there were nothing found.
no_result: Selector,
/// selector to locate the element which contains one item from the search result.
results: Selector,
/// selector to locate the title relative to the search result item.
result_title: Selector,
/// selector to locate the url relative to the search result item.
result_url: Selector,
/// selector to locate the description relative to the search result item.
result_desc: Selector,
}
impl SearchResultParser {
/// Creates a new parser, if all the selectors are valid, otherwise it returns an EngineError
pub fn new(
no_result_selector: &str,
results_selector: &str,
result_title_selector: &str,
result_url_selector: &str,
result_desc_selector: &str,
) -> Result<SearchResultParser, EngineError> {
Ok(SearchResultParser {
no_result: new_selector(no_result_selector)?,
results: new_selector(results_selector)?,
result_title: new_selector(result_title_selector)?,
result_url: new_selector(result_url_selector)?,
result_desc: new_selector(result_desc_selector)?,
})
}
/// Parse the html and returns element representing the 'no result found' response.
pub fn parse_for_no_results<'a>(&'a self, document: &'a Html) -> Select<'a, 'a> {
document.select(&self.no_result)
}
/// Parse the html, and convert the results to SearchResult with the help of the builder function
pub fn parse_for_results(
&self,
document: &Html,
builder: impl Fn(&ElementRef<'_>, &ElementRef<'_>, &ElementRef<'_>) -> Option<SearchResult>,
) -> Result<Vec<(String, SearchResult)>, EngineError> {
let res = document
.select(&self.results)
.filter_map(|result| {
let title = result.select(&self.result_title).next();
let url = result.select(&self.result_url).next();
let desc = result.select(&self.result_desc).next();
match (title, url, desc) {
(Some(ref t), Some(ref u), Some(ref d)) => builder(t, u, d),
_ => None,
}
})
.map(|search_result| (search_result.url.clone(), search_result))
.collect();
Ok(res)
}
}
/// Create a Selector struct, if the given parameter is a valid css expression, otherwise convert it into an EngineError.
fn new_selector(selector: &str) -> Result<Selector, EngineError> {
Selector::parse(selector).map_err(|err| {
Report::new(EngineError::UnexpectedError).attach_printable(format!(
"invalid CSS selector: {}, err: {:?}",
selector, err
))
})
}
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