ebook-rs 0.11.8

use crate::cfi::Cfi;
use crate::section::Section;
use serde::{Deserialize, Serialize};

/// A single search result item.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SearchResult {
    pub spine_index: usize,
    pub snippet: String,
    pub cfi: String,
    pub char_offset: usize,
}

/// Full-text search engine across chapter sections.
pub struct SearchEngine;

impl SearchEngine {
    /// Perform full-text search over a slice of sections.
    /// P4 Fix: Reuses pre-computed section.plain_text_lower for zero-allocation searching.
    pub fn search(sections: &[Section], query: &str, case_sensitive: bool) -> Vec<SearchResult> {
        if query.trim().is_empty() {
            return Vec::new();
        }

        #[cfg(feature = "parallel")]
        {
            use rayon::prelude::*;
            sections
                .par_iter()
                .flat_map(|section| Self::search_section(section, query, case_sensitive))
                .collect()
        }

        #[cfg(not(feature = "parallel"))]
        {
            let mut results = Vec::new();
            for section in sections {
                results.extend(Self::search_section(section, query, case_sensitive));
            }
            results
        }
    }

    /// Search a single section safely without cross-string offset mismatch panics.
    pub fn search_section(
        section: &Section,
        query: &str,
        case_sensitive: bool,
    ) -> Vec<SearchResult> {
        let mut results = Vec::new();
        if query.trim().is_empty() || section.plain_text.is_empty() {
            return results;
        }

        let text_chars: Vec<char> = section.plain_text.chars().collect();
        let query_chars: Vec<char> = query.chars().collect();
        let t_len = text_chars.len();
        let q_len = query_chars.len();

        if q_len > t_len {
            return results;
        }

        let matches_at = |idx: usize| -> bool {
            if idx + q_len > t_len {
                return false;
            }
            for i in 0..q_len {
                let tc = text_chars[idx + i];
                let qc = query_chars[i];
                if case_sensitive {
                    if tc != qc {
                        return false;
                    }
                } else {
                    if tc != qc && !tc.eq_ignore_ascii_case(&qc) {
                        let tc_low = tc.to_lowercase();
                        let qc_low = qc.to_lowercase();
                        if tc_low.ne(qc_low) {
                            return false;
                        }
                    }
                }
            }
            true
        };

        let mut idx = 0;
        while idx <= t_len.saturating_sub(q_len) {
            if matches_at(idx) {
                let start_c = idx.saturating_sub(40);
                let end_c = (idx + q_len + 40).min(t_len);

                let before: String = text_chars[start_c..idx].iter().collect();
                let matched: String = text_chars[idx..idx + q_len].iter().collect();
                let after: String = text_chars[idx + q_len..end_c].iter().collect();

                let prefix = if start_c > 0 { "..." } else { "" };
                let suffix = if end_c < t_len { "..." } else { "" };

                let snippet = format!(
                    "{}{}<mark>{}</mark>{}{}",
                    prefix,
                    html_escape(&before),
                    html_escape(&matched),
                    html_escape(&after),
                    suffix
                );

                let cfi = Cfi::from_spine_index(section.index, None, idx).to_string();

                results.push(SearchResult {
                    spine_index: section.index,
                    snippet,
                    cfi,
                    char_offset: idx,
                });

                idx += q_len.max(1);
            } else {
                idx += 1;
            }
        }

        results
    }

    /// Perform full-text regex pattern search across chapter sections.
    pub fn search_regex(sections: &[Section], pattern: &str) -> Result<Vec<SearchResult>, String> {
        let re = regex::Regex::new(pattern)
            .map_err(|e| format!("Invalid regex pattern '{}': {}", pattern, e))?;
        let mut results = Vec::new();

        for section in sections {
            for m in re.find_iter(&section.plain_text) {
                let abs_idx = m.start();
                let match_str = m.as_str();

                let text_chars: Vec<char> = section.plain_text.chars().collect();
                let char_idx = section.plain_text[..abs_idx.min(section.plain_text.len())]
                    .chars()
                    .count();
                let q_char_len = match_str.chars().count();

                let start_c = char_idx.saturating_sub(40);
                let end_c = (char_idx + q_char_len + 40).min(text_chars.len());

                let match_end = (char_idx + q_char_len).min(text_chars.len());
                let before: String = text_chars[start_c..char_idx].iter().collect();
                let matched: String = text_chars[char_idx..match_end].iter().collect();
                let after: String = text_chars[match_end..end_c].iter().collect();

                let prefix = if start_c > 0 { "..." } else { "" };
                let suffix = if end_c < text_chars.len() { "..." } else { "" };

                let snippet = format!(
                    "{}{}<mark>{}</mark>{}{}",
                    prefix,
                    html_escape(&before),
                    html_escape(&matched),
                    html_escape(&after),
                    suffix
                );
                let cfi = Cfi::from_spine_index(section.index, None, char_idx).to_string();

                results.push(SearchResult {
                    spine_index: section.index,
                    snippet,
                    cfi,
                    char_offset: char_idx,
                });
            }
        }

        Ok(results)
    }

    /// Format search results into Readium Standard Search Collection JSON (application/vnd.readium.search+json).
    pub fn to_readium_search_json(results: &[SearchResult], query: &str) -> Result<String, String> {
        let locators: Vec<serde_json::Value> = results
            .iter()
            .map(|r| {
                serde_json::json!({
                    "href": format!("section_{}.html", r.spine_index),
                    "type": "application/xhtml+xml",
                    "locations": {
                        "cfi": r.cfi,
                        "position": r.char_offset / 1000 + 1
                    },
                    "text": {
                        "snippet": r.snippet
                    }
                })
            })
            .collect();

        let collection = serde_json::json!({
            "@context": "http://readium.org/webpub-manifest/context.jsonld",
            "metadata": {
                "numberOfResults": results.len(),
                "query": query
            },
            "locators": locators
        });

        serde_json::to_string_pretty(&collection)
            .map_err(|e| format!("Failed to serialize Readium Search JSON: {}", e))
    }
}

/// Helper function to HTML-escape arbitrary text strings to prevent stored XSS attacks.
pub fn html_escape(s: &str) -> String {
    s.replace('&', "&amp;")
        .replace('<', "&lt;")
        .replace('>', "&gt;")
        .replace('"', "&quot;")
        .replace('\'', "&#39;")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_search() {
        let sec = Section {
            index: 0,
            idref: "ch1".to_string(),
            href: "ch1.xhtml".to_string(),
            full_path: "OEBPS/ch1.xhtml".to_string(),
            raw_html: "<p>Hello Rust Reader</p>".to_string(),
            processed_html: "<p>Hello Rust Reader</p>".to_string(),
            plain_text: "Hello Rust Reader".to_string(),
            plain_text_lower: "hello rust reader".to_string(),
            char_count: 17,
            viewport_width: None,
            viewport_height: None,
        };

        let results = SearchEngine::search(&[sec], "Rust", false);
        assert_eq!(results.len(), 1);
        assert_eq!(results[0].spine_index, 0);
        assert!(results[0].snippet.contains("Rust"));
    }
}