use std::{
    fs::read_dir, path::PathBuf
};

use freedesktop_entry_parser as fd;
use mlua::prelude::*;
use rayon::prelude::*;
use url::Url;

use crate::lenses::{
    Entry,
    Lense,
    Cache
};

#[derive(Default)]
pub struct Application(pub Cache);

impl Lense for Application {
    const NAME: &str = "Application";

    fn get_cache(&self) -> &Cache {
        &self.0
    }

    fn set_cache(&mut self, cache: Cache) {
        self.0 = cache;
    }

    fn query(_: &Lua, input: String) -> Result<Vec<Entry>, anyhow::Error> {
        let applications_dir = "/usr/share/applications";
        let entries = read_dir(applications_dir)?
            .map(|result| result.map(|e| e.path()))
            .collect::<Result<Vec<_>, std::io::Error>>()?;

        let parsed_entries: Vec<Entry> = entries
            .into_par_iter()
            .filter(|path| path.extension().is_some_and(|ext| ext == "desktop"))
            .filter_map(|path| {
                parse_entry(path).ok().flatten()
            })
            .collect();

        Ok(
            parsed_entries
                .into_iter()
                .filter(|entry| entry.message.to_lowercase().contains(&input.to_lowercase()))
                .collect(),
        )
    }
}

fn parse_entry(path: PathBuf) -> Result<Option<Entry>, ()> {
    let Ok(entry) = fd::parse_entry(&path) else {
        return Err(())
    };

    let section = entry.section("Desktop Entry");
    let name = section.attr("Name").ok_or(())?.to_string();

    if section.attr("Type").ok_or(())? != "Application" {
        return Err(());
    }

    if section.attr("OnlyShowIn").is_some()
        || section.attr("Hidden").is_some()
        || section.attr("NoDisplay").is_some()
    {
        return Err(());
    }

    let exec = section.attr("Exec").ok_or(())?.to_string();
    let mut new_exec = exec.clone();
    for (index, _) in exec.match_indices('%') {
        match exec.chars().nth(index + 1).unwrap().to_ascii_lowercase() {
            'i' => {
                if let Some(icon) = section.attr("Icon") {
                    new_exec.replace_range(index..index + 2, &format!("--icon {icon}"));
                }
            }
            'c' => new_exec.replace_range(index..index + 2, &name),
            'k' => new_exec.replace_range(index..index + 2, Url::from_file_path(&path)?.as_str()),

            'f' | 'u' | 'v' | 'm' | 'd' | 'n' => new_exec.replace_range(index..index + 2, ""),
            _ => continue,
        }
    }

    Ok(Some(Entry {
        message: name,
        exec: Some((
            new_exec,
            section
                .attr("Terminal")
                .unwrap_or("false")
                .parse()
                .map_err(drop)?,
        )),
    }))
}