//! rule34video.com video-page resolution for the `/proxy/rule34video/` redirect.
//!
//! Lives here (always compiled) because `HOT_TUB_PROVIDER=<id>` single-provider
//! builds only compile the selected provider, while the proxy routes are
//! always registered.
//!
//! yt-dlp's Rule34Video extractor no longer resolves the page URL ("No video
//! formats found"), so the signed mp4 URLs (360p/480p/720p, valid ~12h, no
//! cookie/Referer needed) come from the page's `var flashvars`.

use crate::util::requester::Requester;

const BASE_URL: &str = "https://rule34video.com";

/// Reads a single-quoted JS string value (`key: '...'`) from the
/// `flashvars` object, honouring `\'` escapes.
fn flashvar(block: &str, key: &str) -> Option<String> {
    let marker = format!("{}: '", key);
    let start = block.find(&marker)? + marker.len();
    let mut out = String::new();
    let mut chars = block[start..].chars();
    while let Some(c) = chars.next() {
        match c {
            '\\' => out.push(chars.next()?),
            '\'' => return Some(out),
            other => out.push(other),
        }
    }
    None
}

/// `(height, url)` for every quality on the page, best first.
pub fn parse_formats(html: &str) -> Vec<(u32, String)> {
    let Some(start) = html.find("var flashvars") else {
        return vec![];
    };
    let block = &html[start..];
    let block = &block[..block.len().min(6000)];

    let mut formats: Vec<(u32, String)> = Vec::new();
    for (url_key, text_key) in [
        ("video_url", "video_url_text"),
        ("video_alt_url", "video_alt_url_text"),
        ("video_alt_url2", "video_alt_url2_text"),
        ("video_alt_url3", "video_alt_url3_text"),
    ] {
        let Some(url) = flashvar(block, url_key).filter(|url| url.starts_with("http")) else {
            continue;
        };
        let height = flashvar(block, text_key)
            .and_then(|quality| quality.trim_end_matches('p').parse::<u32>().ok())
            .unwrap_or(0);
        formats.push((height, url));
    }
    formats.sort_by(|a, b| b.0.cmp(&a.0));
    formats
}

/// `{id}/{slug}[/]` -> the video page URL. Only digits, letters, `-` and `_`
/// are accepted so the endpoint cannot steer the request elsewhere.
pub fn page_url(endpoint: &str) -> Option<String> {
    let mut parts = endpoint.trim_matches('/').split('/');
    let id = parts.next().filter(|id| !id.is_empty() && id.chars().all(|c| c.is_ascii_digit()))?;
    let slug = parts.next().filter(|slug| {
        !slug.is_empty() && slug.chars().all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_')
    })?;
    match parts.next() {
        None => Some(format!("{BASE_URL}/video/{id}/{slug}/")),
        Some(_) => None,
    }
}

/// The best signed mp4 URL (or the one of `height`) for a video page.
pub async fn resolve_media_url(
    requester: &mut Requester,
    page_url: &str,
    height: Option<u32>,
) -> Option<String> {
    let headers = vec![("Referer".to_string(), format!("{BASE_URL}/"))];
    let html = requester.get_probe(page_url, headers).await.ok().flatten()?;
    let formats = parse_formats(&html);
    height
        .and_then(|h| formats.iter().find(|(height, _)| *height == h))
        .or_else(|| formats.first())
        .map(|(_, url)| url.clone())
}

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

    #[test]
    fn parses_flashvars_formats_best_first() {
        let html = r#"var flashvars = { video_id: '1', video_url: 'https://rule34video.com/get_file/a_360.mp4/?v-acctoken=1', video_url_text: '360p', video_alt_url: 'https://rule34video.com/get_file/a_480p.mp4/?v-acctoken=2', video_alt_url_text: '480p', video_alt_url2: 'https://rule34video.com/get_file/a_720p.mp4/?v-acctoken=3', video_alt_url2_text: '720p', video_title: 'It\'s' };"#;
        let formats = parse_formats(html);
        assert_eq!(formats.len(), 3);
        assert_eq!(formats[0].0, 720);
        assert!(formats[0].1.contains("a_720p"));
        assert!(formats[2].1.contains("a_360"));
    }

    #[test]
    fn page_without_flashvars_yields_nothing() {
        assert!(parse_formats("<html></html>").is_empty());
    }

    #[test]
    fn builds_page_url_from_safe_endpoints_only() {
        assert_eq!(
            page_url("123/some-slug/").as_deref(),
            Some("https://rule34video.com/video/123/some-slug/")
        );
        assert_eq!(page_url("123/../x"), None);
        assert_eq!(page_url("abc/slug"), None);
        assert_eq!(page_url("123/slug/extra"), None);
    }
}