use std::cmp::Ordering;
use std::path::Path;
use std::time::SystemTime;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EntryKind {
    Directory,
    ZipArchive,
    Image,
    Video,
    OtherFile,
}

impl EntryKind {
    pub fn is_viewable(self) -> bool {
        matches!(self, Self::ZipArchive | Self::Image | Self::Video)
    }
}

#[derive(Debug, Clone)]
pub struct BrowserEntry {
    pub uri: String,
    pub name: String,
    pub kind: EntryKind,
    pub size: Option<u64>,
    pub modified: Option<SystemTime>,
    pub created: Option<SystemTime>,
    pub etag: Option<String>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SortField {
    Name,
    Modified,
    Created,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SortDirection {
    Ascending,
    Descending,
}

pub fn sort_entries(entries: &mut [BrowserEntry], field: SortField, direction: SortDirection) {
    entries.sort_by(|left, right| {
        let kind_order = match (
            left.kind == EntryKind::Directory,
            right.kind == EntryKind::Directory,
        ) {
            (true, false) => Ordering::Less,
            (false, true) => Ordering::Greater,
            _ => Ordering::Equal,
        };
        if kind_order != Ordering::Equal {
            return kind_order;
        }

        match field {
            SortField::Name => apply_direction(natural_cmp(&left.name, &right.name), direction),
            SortField::Modified => compare_optional_time(left.modified, right.modified, direction)
                .then_with(|| apply_direction(natural_cmp(&left.name, &right.name), direction)),
            SortField::Created => compare_optional_time(left.created, right.created, direction)
                .then_with(|| apply_direction(natural_cmp(&left.name, &right.name), direction)),
        }
    });
}

fn compare_optional_time(
    left: Option<SystemTime>,
    right: Option<SystemTime>,
    direction: SortDirection,
) -> Ordering {
    match (left, right) {
        (Some(left), Some(right)) => apply_direction(left.cmp(&right), direction),
        (Some(_), None) => Ordering::Less,
        (None, Some(_)) => Ordering::Greater,
        (None, None) => Ordering::Equal,
    }
}

fn apply_direction(order: Ordering, direction: SortDirection) -> Ordering {
    match direction {
        SortDirection::Ascending => order,
        SortDirection::Descending => order.reverse(),
    }
}

pub fn classify_file(path: &Path) -> EntryKind {
    let extension = path
        .extension()
        .and_then(|extension| extension.to_str())
        .map(str::to_ascii_lowercase);
    match extension.as_deref() {
        Some("zip") => EntryKind::ZipArchive,
        Some("jpg" | "jpeg" | "png" | "webp" | "gif" | "bmp" | "avif") => EntryKind::Image,
        Some("mp4" | "m4v" | "mkv" | "webm" | "mov" | "avi" | "mpeg" | "mpg" | "ogv") => {
            EntryKind::Video
        }
        _ => EntryKind::OtherFile,
    }
}

pub fn natural_cmp(left: &str, right: &str) -> Ordering {
    let mut left_chars = left.chars().peekable();
    let mut right_chars = right.chars().peekable();

    loop {
        match (left_chars.peek(), right_chars.peek()) {
            (None, None) => return Ordering::Equal,
            (None, Some(_)) => return Ordering::Less,
            (Some(_), None) => return Ordering::Greater,
            (Some(left_char), Some(right_char))
                if left_char.is_ascii_digit() && right_char.is_ascii_digit() =>
            {
                let left_number = take_digits(&mut left_chars);
                let right_number = take_digits(&mut right_chars);
                let left_trimmed = left_number.trim_start_matches('0');
                let right_trimmed = right_number.trim_start_matches('0');
                let left_significant = if left_trimmed.is_empty() {
                    "0"
                } else {
                    left_trimmed
                };
                let right_significant = if right_trimmed.is_empty() {
                    "0"
                } else {
                    right_trimmed
                };

                let order = left_significant
                    .len()
                    .cmp(&right_significant.len())
                    .then_with(|| left_significant.cmp(right_significant))
                    .then_with(|| left_number.len().cmp(&right_number.len()));
                if order != Ordering::Equal {
                    return order;
                }
            }
            (Some(_), Some(_)) => {
                let left_char = left_chars.next().unwrap();
                let right_char = right_chars.next().unwrap();
                let order = left_char
                    .to_lowercase()
                    .cmp(right_char.to_lowercase())
                    .then_with(|| left_char.cmp(&right_char));
                if order != Ordering::Equal {
                    return order;
                }
            }
        }
    }
}

fn take_digits<I>(characters: &mut std::iter::Peekable<I>) -> String
where
    I: Iterator<Item = char>,
{
    let mut digits = String::new();
    while characters.peek().is_some_and(char::is_ascii_digit) {
        digits.push(characters.next().unwrap());
    }
    digits
}

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

    #[test]
    fn natural_order_places_two_before_ten() {
        let mut names = ["page10.jpg", "page2.jpg", "page1.jpg"];
        names.sort_by(|left, right| natural_cmp(left, right));
        assert_eq!(names, ["page1.jpg", "page2.jpg", "page10.jpg"]);
    }

    #[test]
    fn natural_order_handles_numbers_larger_than_integers() {
        assert_eq!(
            natural_cmp("9.zip", "123456789012345678901234567890.zip"),
            Ordering::Less
        );
    }

    #[test]
    fn zip_extension_is_case_insensitive() {
        assert_eq!(classify_file(Path::new("comic.ZIP")), EntryKind::ZipArchive);
        assert_ne!(classify_file(Path::new("comic.cbz")), EntryKind::ZipArchive);
    }

    #[test]
    fn classifies_common_media_extensions_case_insensitively() {
        assert_eq!(classify_file(Path::new("photo.JPG")), EntryKind::Image);
        assert_eq!(classify_file(Path::new("animation.webp")), EntryKind::Image);
        assert_eq!(classify_file(Path::new("movie.MP4")), EntryKind::Video);
        assert_eq!(classify_file(Path::new("movie.mkv")), EntryKind::Video);
        assert_eq!(classify_file(Path::new("notes.txt")), EntryKind::OtherFile);
    }

    #[test]
    fn unknown_times_sort_after_known_times() {
        let now = SystemTime::now();
        assert_eq!(
            compare_optional_time(Some(now), None, SortDirection::Ascending),
            Ordering::Less
        );
        assert_eq!(
            compare_optional_time(Some(now), None, SortDirection::Descending),
            Ordering::Less
        );
    }
}