use std::collections::HashMap;

use crate::escape::html_escape;

/// Quote author info for attribution rendering.
pub struct QuoteAuthor {
    pub username: String,
    pub display_name: String,
    pub is_removed: bool,
}

/// Post-process rendered HTML to replace `[quote:POST_ID:HASH]` markers with
/// clickable author attribution.
pub fn post_process_quotes(
    html: &str,
    quote_authors: &HashMap<uuid::Uuid, QuoteAuthor>,
) -> String {
    static QUOTE_RE: std::sync::LazyLock<regex_lite::Regex> = std::sync::LazyLock::new(|| {
        regex_lite::Regex::new(r"\[quote:([0-9a-f\-]{36}):([0-9a-f]{8})\]").unwrap()
    });
    QUOTE_RE
        .replace_all(html, |caps: &regex_lite::Captures| {
            let post_id_str = &caps[1];
            let resolved = uuid::Uuid::parse_str(post_id_str)
                .ok()
                .and_then(|post_id| quote_authors.get(&post_id));

            if let Some(author) = resolved {
                if author.is_removed {
                    format!(
                        "<cite class=\"quote-attribution\"><a href=\"#post-{}\">(original post removed)</a></cite>",
                        post_id_str
                    )
                } else {
                    format!(
                        "<cite class=\"quote-attribution\"><a href=\"#post-{}\">— {} (@{})</a></cite>",
                        post_id_str,
                        html_escape(&author.display_name),
                        html_escape(&author.username),
                    )
                }
            } else {
                caps[0].to_string()
            }
        })
        .to_string()
}

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

    #[test]
    fn replaces_quote_marker_with_attribution() {
        let post_id = uuid::Uuid::new_v4();
        let mut authors = HashMap::new();
        authors.insert(
            post_id,
            QuoteAuthor {
                username: "alice".to_string(),
                display_name: "Alice Smith".to_string(),
                is_removed: false,
            },
        );
        let input = format!("[quote:{}:abcd1234]", post_id);
        let result = post_process_quotes(&input, &authors);
        assert!(result.contains("Alice Smith"));
        assert!(result.contains("@alice"));
        assert!(result.contains("quote-attribution"));
    }

    #[test]
    fn removed_post_shows_removed_text() {
        let post_id = uuid::Uuid::new_v4();
        let mut authors = HashMap::new();
        authors.insert(
            post_id,
            QuoteAuthor {
                username: "bob".to_string(),
                display_name: "Bob".to_string(),
                is_removed: true,
            },
        );
        let input = format!("[quote:{}:abcd1234]", post_id);
        let result = post_process_quotes(&input, &authors);
        assert!(result.contains("original post removed"));
        assert!(!result.contains("Bob"));
    }

    #[test]
    fn unknown_post_id_left_unchanged() {
        let authors = HashMap::new();
        let input = "[quote:00000000-0000-0000-0000-000000000000:abcd1234]";
        let result = post_process_quotes(input, &authors);
        assert_eq!(result, input);
    }

    #[test]
    fn non_quote_text_unchanged() {
        let authors = HashMap::new();
        let input = "<p>Hello world</p>";
        let result = post_process_quotes(input, &authors);
        assert_eq!(result, input);
    }

    #[test]
    fn html_escapes_display_name() {
        let post_id = uuid::Uuid::new_v4();
        let mut authors = HashMap::new();
        authors.insert(
            post_id,
            QuoteAuthor {
                username: "user".to_string(),
                display_name: "A <B> & C".to_string(),
                is_removed: false,
            },
        );
        let input = format!("[quote:{}:abcd1234]", post_id);
        let result = post_process_quotes(&input, &authors);
        assert!(result.contains("A &lt;B&gt; &amp; C"));
        assert!(!result.contains("<B>"));
    }
}