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

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()))
}