use std::path::Path;

use regex::Regex;

use crate::utils::{collapse_whitespace, normalize_title};

#[derive(Debug, Clone)]
pub struct FileHints {
    pub title: Option<String>,
    pub normalized_title: Option<String>,
    pub year: Option<i32>,
    pub alt_titles: Vec<String>,
}

pub fn parse_filename(path: &Path) -> FileHints {
    let stem = path
        .file_stem()
        .map(|s| s.to_string_lossy().to_string())
        .unwrap_or_default();

    let year = extract_year(&stem);
    let cleaned = strip_bracketed(&stem);
    let alt_titles = extract_alt_titles(&cleaned, year);
    let tokens = tokenize(&cleaned, year);

    let title = if tokens.is_empty() {
        let mut fallback = cleaned.clone();
        if let Some(year) = year {
            fallback = fallback.replace(&year.to_string(), "");
        }
        let fallback = collapse_whitespace(&fallback);
        if fallback.is_empty() { None } else { Some(fallback) }
    } else {
        Some(collapse_whitespace(&tokens.join(" ")))
    };
    let normalized_title = title.as_deref().map(normalize_title);

    FileHints {
        title,
        normalized_title,
        year,
        alt_titles,
    }
}

fn extract_year(raw: &str) -> Option<i32> {
    let re = Regex::new(r"(19|20)\d{2}").ok()?;
    let mut year: Option<i32> = None;
    for mat in re.find_iter(raw) {
        if let Ok(parsed) = mat.as_str().parse::<i32>() {
            year = Some(parsed);
        }
    }
    year
}

fn strip_bracketed(raw: &str) -> String {
    let re_square = Regex::new(r"\[[^\]]*\]").unwrap();
    let re_round = Regex::new(r"\([^\)]*\)").unwrap();
    let without_square = re_square.replace_all(raw, " ");
    let without_round = re_round.replace_all(&without_square, " ");
    without_round.to_string()
}

fn extract_alt_titles(raw: &str, year: Option<i32>) -> Vec<String> {
    let mut alt_titles = Vec::new();
    if let Some((left, right)) = raw.split_once(" - ") {
        let left = clean_title_fragment(left, year);
        let right = collapse_whitespace(right);
        if !left.is_empty() && !right.is_empty() {
            alt_titles.push(left);
        }
    }
    alt_titles
}

fn clean_title_fragment(fragment: &str, year: Option<i32>) -> String {
    let mut cleaned = fragment.to_string();
    if let Some(year) = year {
        cleaned = cleaned.replace(&year.to_string(), " ");
    }
    collapse_whitespace(&cleaned)
}

fn tokenize(raw: &str, year: Option<i32>) -> Vec<String> {
    let stopwords = stopwords();
    let mut tokens = Vec::new();
    for token in raw.split(|c: char| !c.is_alphanumeric()) {
        if token.is_empty() {
            continue;
        }
        let lower = token.to_ascii_lowercase();
        if let Some(year) = year {
            if lower == year.to_string() {
                continue;
            }
        }
        if stopwords.contains(lower.as_str()) {
            continue;
        }
        if token.chars().all(|c| c.is_ascii_uppercase()) && token.len() <= 8 {
            continue;
        }
        tokens.push(token.to_string());
    }
    tokens
}

fn stopwords() -> std::collections::HashSet<&'static str> {
    [
        "1080p", "720p", "2160p", "480p", "360p", "4k", "uhd", "hdr", "dvdrip",
        "bdrip", "brrip", "bluray", "blu", "webdl", "web-dl", "webrip", "hdrip",
        "remux", "x264", "x265", "h264", "h265", "hevc", "aac", "dts", "ac3",
        "proper", "repack", "limited", "extended", "uncut", "remastered", "subbed",
        "subs", "multi", "dubbed", "dub", "yts", "yify", "rarbg", "web", "hd",
        "hq", "cam", "ts", "dvdscr", "r5", "r6",
    ]
    .into_iter()
    .collect()
}

#[cfg(test)]
mod tests {
    use super::parse_filename;
    use std::path::Path;

    #[test]
    fn parses_basic_title_and_year() {
        let path = Path::new("Some.Movie.2020.1080p.BluRay.x264-GROUP.mkv");
        let hints = parse_filename(path);
        assert_eq!(hints.title.as_deref(), Some("Some Movie"));
        assert_eq!(hints.year, Some(2020));
    }

    #[test]
    fn handles_brackets_and_stopwords() {
        let path = Path::new("[YTS] The.Matrix.(1999).1080p.BluRay.mkv");
        let hints = parse_filename(path);
        assert_eq!(hints.title.as_deref(), Some("The Matrix"));
        assert_eq!(hints.year, Some(1999));
    }

    #[test]
    fn adds_alt_title_for_dash_suffix() {
        let path = Path::new("Zootopia - Vlix.mp4");
        let hints = parse_filename(path);
        assert_eq!(hints.title.as_deref(), Some("Zootopia Vlix"));
        assert!(hints.alt_titles.iter().any(|t| t == "Zootopia"));
    }
}