// ABOUTME: Locale detection and string lookup for the power menu UI.
// ABOUTME: Reads system locale (LANG or /etc/locale.conf) and provides DE or EN strings.

use std::env;
use std::fs;
use std::path::Path;

const DEFAULT_LOCALE_CONF: &str = "/etc/locale.conf";

/// All user-visible strings for the power menu UI.
#[derive(Debug, Clone)]
pub struct Strings {
    // Button labels
    pub lock_label: &'static str,
    pub logout_label: &'static str,
    pub hibernate_label: &'static str,
    pub reboot_label: &'static str,
    pub shutdown_label: &'static str,

    // Confirmation prompts
    pub logout_confirm: &'static str,
    pub hibernate_confirm: &'static str,
    pub reboot_confirm: &'static str,
    pub shutdown_confirm: &'static str,

    // Confirmation buttons
    pub confirm_yes: &'static str,
    pub confirm_no: &'static str,

    // Error messages
    pub lock_failed: &'static str,
    pub logout_failed: &'static str,
    pub hibernate_failed: &'static str,
    pub reboot_failed: &'static str,
    pub shutdown_failed: &'static str,
}

const STRINGS_DE: Strings = Strings {
    lock_label: "Sperren",
    logout_label: "Abmelden",
    hibernate_label: "Ruhezustand",
    reboot_label: "Neustart",
    shutdown_label: "Herunterfahren",
    logout_confirm: "Wirklich abmelden?",
    hibernate_confirm: "Wirklich in den Ruhezustand?",
    reboot_confirm: "Wirklich neu starten?",
    shutdown_confirm: "Wirklich herunterfahren?",
    confirm_yes: "Ja",
    confirm_no: "Abbrechen",
    lock_failed: "Sperren fehlgeschlagen",
    logout_failed: "Abmelden fehlgeschlagen",
    hibernate_failed: "Ruhezustand fehlgeschlagen",
    reboot_failed: "Neustart fehlgeschlagen",
    shutdown_failed: "Herunterfahren fehlgeschlagen",
};

const STRINGS_EN: Strings = Strings {
    lock_label: "Lock",
    logout_label: "Log out",
    hibernate_label: "Hibernate",
    reboot_label: "Reboot",
    shutdown_label: "Shut down",
    logout_confirm: "Really log out?",
    hibernate_confirm: "Really hibernate?",
    reboot_confirm: "Really reboot?",
    shutdown_confirm: "Really shut down?",
    confirm_yes: "Yes",
    confirm_no: "Cancel",
    lock_failed: "Lock failed",
    logout_failed: "Log out failed",
    hibernate_failed: "Hibernate failed",
    reboot_failed: "Reboot failed",
    shutdown_failed: "Shutdown failed",
};

/// Extract the language prefix from a LANG value like "de_DE.UTF-8" → "de".
/// Returns "en" for empty, "C", or "POSIX" values.
fn parse_lang_prefix(lang: &str) -> String {
    if lang.is_empty() || lang == "C" || lang == "POSIX" {
        return "en".to_string();
    }

    let prefix = lang
        .split('_')
        .next()
        .unwrap_or(lang)
        .split('.')
        .next()
        .unwrap_or(lang)
        .to_lowercase();

    if prefix.chars().all(|c| c.is_ascii_alphabetic()) && !prefix.is_empty() {
        prefix
    } else {
        "en".to_string()
    }
}

/// Read the LANG= value from a locale.conf file.
fn read_lang_from_conf(path: &Path) -> Option<String> {
    let content = fs::read_to_string(path).ok()?;
    for line in content.lines() {
        if let Some(value) = line.strip_prefix("LANG=") {
            let value = value.trim();
            if !value.is_empty() {
                return Some(value.to_string());
            }
        }
    }
    None
}

/// Determine the system language from LANG env var or /etc/locale.conf.
pub fn detect_locale() -> String {
    let lang = env::var("LANG")
        .ok()
        .filter(|s| !s.is_empty())
        .or_else(|| read_lang_from_conf(Path::new(DEFAULT_LOCALE_CONF)));

    match lang {
        Some(l) => parse_lang_prefix(&l),
        None => "en".to_string(),
    }
}

/// Return the string table for the given locale, defaulting to English.
pub fn load_strings(locale: Option<&str>) -> &'static Strings {
    let locale = match locale {
        Some(l) => l.to_string(),
        None => detect_locale(),
    };

    match locale.as_str() {
        "de" => &STRINGS_DE,
        _ => &STRINGS_EN,
    }
}

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

    // -- parse_lang_prefix tests (no env manipulation needed) --

    #[test]
    fn parse_german_locale() {
        assert_eq!(parse_lang_prefix("de_DE.UTF-8"), "de");
    }

    #[test]
    fn parse_english_locale() {
        assert_eq!(parse_lang_prefix("en_US.UTF-8"), "en");
    }

    #[test]
    fn parse_c_falls_back_to_english() {
        assert_eq!(parse_lang_prefix("C"), "en");
    }

    #[test]
    fn parse_posix_falls_back_to_english() {
        assert_eq!(parse_lang_prefix("POSIX"), "en");
    }

    #[test]
    fn parse_empty_falls_back_to_english() {
        assert_eq!(parse_lang_prefix(""), "en");
    }

    #[test]
    fn parse_unsupported_returns_prefix() {
        assert_eq!(parse_lang_prefix("fr_FR.UTF-8"), "fr");
    }

    #[test]
    fn parse_bare_language_code() {
        assert_eq!(parse_lang_prefix("de"), "de");
    }

    // -- read_lang_from_conf tests --

    #[test]
    fn read_conf_extracts_lang() {
        let dir = tempfile::tempdir().unwrap();
        let conf = dir.path().join("locale.conf");
        let mut f = fs::File::create(&conf).unwrap();
        writeln!(f, "LANG=de_DE.UTF-8").unwrap();
        assert_eq!(read_lang_from_conf(&conf), Some("de_DE.UTF-8".to_string()));
    }

    #[test]
    fn read_conf_returns_none_for_missing_file() {
        assert_eq!(read_lang_from_conf(Path::new("/nonexistent/locale.conf")), None);
    }

    #[test]
    fn read_conf_returns_none_for_empty_lang() {
        let dir = tempfile::tempdir().unwrap();
        let conf = dir.path().join("locale.conf");
        let mut f = fs::File::create(&conf).unwrap();
        writeln!(f, "LANG=").unwrap();
        assert_eq!(read_lang_from_conf(&conf), None);
    }

    #[test]
    fn read_conf_skips_non_lang_lines() {
        let dir = tempfile::tempdir().unwrap();
        let conf = dir.path().join("locale.conf");
        let mut f = fs::File::create(&conf).unwrap();
        writeln!(f, "LC_ALL=en_US.UTF-8").unwrap();
        writeln!(f, "LANG=de_DE.UTF-8").unwrap();
        assert_eq!(read_lang_from_conf(&conf), Some("de_DE.UTF-8".to_string()));
    }

    // -- load_strings tests --

    #[test]
    fn load_strings_german() {
        let strings = load_strings(Some("de"));
        assert_eq!(strings.lock_label, "Sperren");
        assert_eq!(strings.confirm_yes, "Ja");
        assert_eq!(strings.confirm_no, "Abbrechen");
    }

    #[test]
    fn load_strings_english() {
        let strings = load_strings(Some("en"));
        assert_eq!(strings.lock_label, "Lock");
        assert_eq!(strings.confirm_yes, "Yes");
    }

    #[test]
    fn load_strings_unknown_falls_back_to_english() {
        let strings = load_strings(Some("fr"));
        assert_eq!(strings.lock_label, "Lock");
    }

    #[test]
    fn all_string_fields_nonempty() {
        for locale in &["de", "en"] {
            let s = load_strings(Some(locale));
            assert!(!s.lock_label.is_empty(), "{locale}: lock_label empty");
            assert!(!s.logout_label.is_empty(), "{locale}: logout_label empty");
            assert!(!s.hibernate_label.is_empty(), "{locale}: hibernate_label empty");
            assert!(!s.reboot_label.is_empty(), "{locale}: reboot_label empty");
            assert!(!s.shutdown_label.is_empty(), "{locale}: shutdown_label empty");
            assert!(!s.logout_confirm.is_empty(), "{locale}: logout_confirm empty");
            assert!(!s.hibernate_confirm.is_empty(), "{locale}: hibernate_confirm empty");
            assert!(!s.reboot_confirm.is_empty(), "{locale}: reboot_confirm empty");
            assert!(!s.shutdown_confirm.is_empty(), "{locale}: shutdown_confirm empty");
            assert!(!s.confirm_yes.is_empty(), "{locale}: confirm_yes empty");
            assert!(!s.confirm_no.is_empty(), "{locale}: confirm_no empty");
            assert!(!s.lock_failed.is_empty(), "{locale}: lock_failed empty");
            assert!(!s.logout_failed.is_empty(), "{locale}: logout_failed empty");
            assert!(!s.hibernate_failed.is_empty(), "{locale}: hibernate_failed empty");
            assert!(!s.reboot_failed.is_empty(), "{locale}: reboot_failed empty");
            assert!(!s.shutdown_failed.is_empty(), "{locale}: shutdown_failed empty");
        }
    }

    #[test]
    fn error_messages_contain_failed() {
        let s = load_strings(Some("en"));
        assert!(s.lock_failed.to_lowercase().contains("failed"));
        assert!(s.logout_failed.to_lowercase().contains("failed"));
        assert!(s.hibernate_failed.to_lowercase().contains("failed"));
        assert!(s.reboot_failed.to_lowercase().contains("failed"));
        assert!(s.shutdown_failed.to_lowercase().contains("failed"));
    }
}