use std::{
    collections::{HashMap, VecDeque},
    str::FromStr,
};

use lazy_static::lazy_static;
use mime::Mime;

lazy_static! {
    static ref ALIASES: HashMap<Mime, Mime> = load_mime_aliases();
    static ref PARENTS: Vec<(Mime, Mime)> = load_mime_parent_relations();
    static ref EXTENSIONS: HashMap<Mime, &'static str> = load_mime_extensions();
}

fn load_mime_aliases() -> HashMap<Mime, Mime> {
    tree_magic_db::aliases()
        .lines()
        .flat_map(|line| line.split_once(' '))
        .flat_map(|(alias, mime)| Some((Mime::from_str(alias).ok()?, Mime::from_str(mime).ok()?)))
        .collect()
}

fn load_mime_parent_relations() -> Vec<(Mime, Mime)> {
    tree_magic_db::subclasses()
        .lines()
        .flat_map(|line| line.split_once(' '))
        .flat_map(|(child, parent)| {
            Some((Mime::from_str(child).ok()?, Mime::from_str(parent).ok()?))
        })
        .collect()
}

fn load_mime_extensions() -> HashMap<Mime, &'static str> {
    include_str!("../mime.types")
        .lines()
        .filter(|line| !line.is_empty() && !line.starts_with('#'))
        .map(|line| line.split_whitespace())
        .flat_map(|mut elements| Some((Mime::from_str(elements.next()?).ok()?, elements.next()?)))
        .flat_map(|(mime, extension)| {
            Some((ALIASES.get(&mime).unwrap_or(&mime).clone(), extension))
        })
        .collect()
}

pub(crate) fn get_alias(mimetype: Mime) -> Mime {
    ALIASES.get(&mimetype).cloned().unwrap_or(mimetype)
}

fn get_mime_parents(mimetype: &Mime) -> Vec<&Mime> {
    PARENTS
        .iter()
        .filter_map(|(child, parent)| (child == mimetype).then_some(parent))
        .collect()
}

pub(crate) fn matches_text(mime: &Mime) -> bool {
    if mime.type_() == mime::TEXT {
        return true;
    }
    return get_mime_parents(mime).into_iter().any(matches_text);
}

pub(crate) fn get_extension(mimetype: &Mime) -> Option<&'static str> {
    let mut queue = VecDeque::new();
    queue.push_back(mimetype);
    while let Some(mime) = queue.pop_front() {
        match EXTENSIONS.get(mimetype).copied() {
            Some(ext) => return Some(ext),
            None => queue.extend(get_mime_parents(mime)),
        }
    }
    None
}