use std::{collections::HashMap, fs::{self, File}, io::BufReader, process::Command};
use derive_more::From;
use rocket_dyn_templates::tera::{self, Value};

use gettext::Catalog;

#[derive(From, Debug)]
pub enum LoadCatalogsError {
    Io(std::io::Error),
    Parse(gettext::Error),
    MissingDefaultLanguage,
}

const DEFAULT: &str = "ja";

pub fn load_catalogs() -> Result<HashMap<String, Catalog>, LoadCatalogsError> {
    let mut catalogs = HashMap::new();
    for file in fs::read_dir("i18n")? {
        let file = file?;
        let path = file.path();
        if !file.file_type()?.is_file() || !path.extension().map(|extension| extension.eq("po")).unwrap_or(false) {
            continue;
        }
        let language_code = path
            .file_stem()
            .expect("Invalid translation file name")
            .to_string_lossy()
            .to_string();
        let po_file_path = path;
        let mo_file_path = format!("i18n/{}.mo", language_code);
        Command::new("msgfmt")
            .arg(&po_file_path)
            .arg("-o")
            .arg(&mo_file_path)
            .output()?;
        catalogs.insert(language_code, Catalog::parse(BufReader::new(File::open(mo_file_path)?))?);
    }
    if !catalogs.contains_key(DEFAULT) {
        return Err(LoadCatalogsError::MissingDefaultLanguage);
    }
    Ok(catalogs)
}

pub fn i18n_filter(value: &Value, _args: &HashMap<String, Value>, catalogs: &HashMap<String, Catalog>) -> tera::Result<Value> {
    let key = value.as_str().ok_or_else(|| {
        tera::Error::msg("The translation key must be a string")
    })?;

    let translation = catalogs
        .get(DEFAULT)
        .expect("Missing catalog")
        .gettext(key);

    Ok(Value::String(translation.to_owned()))
}