//! The `startpage` module handles the scraping of results from the startpage search engine
//! by querying the upstream startpage search engine with user provided query and with a page
//! number if provided.

use std::collections::HashMap;

use reqwest::header::HeaderMap;
use reqwest::Client;
use scraper::Html;

use crate::models::aggregation_models::SearchResult;

use crate::models::engine_models::{EngineError, SearchEngine};

use error_stack::{Report, Result, ResultExt};

use super::search_result_parser::SearchResultParser;

/// A new Startpage 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 Startpage {
    /// The parser, used to interpret the search result.
    parser: SearchResultParser,
}

impl Startpage {
    /// Creates the Startpage parser.
    pub fn new() -> Result<Self, EngineError> {
        Ok(Self {
            parser: SearchResultParser::new(
                ".no-results",
                ".w-gl__result__main",
                ".w-gl__result-second-line-container>.w-gl__result-title>h3",
                ".w-gl__result-url",
                ".w-gl__description",
            )?,
        })
    }
}

#[async_trait::async_trait]
impl SearchEngine for Startpage {
    async fn results(
        &self,
        query: &str,
        page: u32,
        user_agent: &str,
        client: &Client,
        _safe_search: u8,
    ) -> Result<HashMap<String, SearchResult>, 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 | 0 => {
                format!("https://startpage.com/do/dsearch?q={query}&num=10&start=0")
            }
            _ => {
                format!(
                    "https://startpage.com/do/dsearch?q={query}&num=10&start={}",
                    page * 10,
                )
            }
        };

        // initializing HeaderMap and adding appropriate headers.
        let header_map = HeaderMap::try_from(&HashMap::from([
            ("USER_AGENT".to_string(), user_agent.to_string()),
            ("REFERER".to_string(), "https://google.com/".to_string()),
            (
                "CONTENT_TYPE".to_string(),
                "application/x-www-form-urlencoded".to_string(),
            ),
            ("COOKIE".to_string(), "preferences=connect_to_serverEEE0N1Ndate_timeEEEworldN1Ndisable_family_filterEEE0N1Ndisable_open_in_new_windowEEE0N1Nenable_post_methodEEE1N1Nenable_proxy_safety_suggestEEE1N1Nenable_stay_controlEEE0N1Ninstant_answersEEE1N1Nlang_homepageEEEs%2Fnight%2FenN1NlanguageEEEenglishN1Nlanguage_uiEEEenglishN1Nnum_of_resultsEEE10N1Nsearch_results_regionEEEallN1NsuggestionsEEE1N1Nwt_unitEEEcelsius".to_string()),
        ]))
        .change_context(EngineError::UnexpectedError)?;

        let document: Html = Html::parse_document(
            &Startpage::fetch_html_from_upstream(self, &url, header_map, client).await?,
        );

        if self.parser.parse_for_no_results(&document).next().is_some() {
            return Err(Report::new(EngineError::EmptyResultSet));
        }

        // scrape all the results from the html
        self.parser
            .parse_for_results(&document, |title, url, desc| {
                Some(SearchResult::new(
                    title.inner_html().trim(),
                    url.inner_html().trim(),
                    desc.inner_html().trim(),
                    &["startpage"],
                ))
            })
    }
}