// This file is part of the uutils coreutils package.
//
// For the full copyright and license information, please view the LICENSE
// file that was distributed with this source code.
// spell-checker:disable

use crate::error::UError;

use fluent::{FluentArgs, FluentBundle, FluentResource};
use fluent_syntax::parser::ParserError;

use std::cell::Cell;
use std::fs;
use std::path::{Path, PathBuf};
use std::str::FromStr;
use std::sync::OnceLock;

use os_display::Quotable;
use thiserror::Error;
use unic_langid::LanguageIdentifier;

#[derive(Error, Debug)]
pub enum LocalizationError {
    #[error("I/O error loading '{path}': {source}")]
    Io {
        source: std::io::Error,
        path: PathBuf,
    },
    #[error("Parse-locale error: {0}")]
    ParseLocale(String),
    #[error("Resource parse error at '{snippet}': {error:?}")]
    ParseResource {
        #[source]
        error: ParserError,
        snippet: String,
    },
    #[error("Bundle error: {0}")]
    Bundle(String),
    #[error("Locales directory not found: {0}")]
    LocalesDirNotFound(String),
    #[error("Path resolution error: {0}")]
    PathResolution(String),
}

impl From<std::io::Error> for LocalizationError {
    fn from(error: std::io::Error) -> Self {
        Self::Io {
            source: error,
            path: PathBuf::from("<unknown>"),
        }
    }
}

// Add a generic way to convert LocalizationError to UError
impl UError for LocalizationError {
    fn code(&self) -> i32 {
        1
    }
}

pub const DEFAULT_LOCALE: &str = "en-US";

// Include embedded locale files as fallback
include!(concat!(env!("OUT_DIR"), "/embedded_locales.rs"));

// A struct to handle localization with optional English fallback
struct Localizer {
    primary_bundle: FluentBundle<&'static FluentResource>,
    fallback_bundle: Option<FluentBundle<&'static FluentResource>>,
}

impl Localizer {
    fn new(primary_bundle: FluentBundle<&'static FluentResource>) -> Self {
        Self {
            primary_bundle,
            fallback_bundle: None,
        }
    }

    fn with_fallback(mut self, fallback_bundle: FluentBundle<&'static FluentResource>) -> Self {
        self.fallback_bundle = Some(fallback_bundle);
        self
    }

    fn format(&self, id: &str, args: Option<&FluentArgs>) -> String {
        // Try primary bundle first
        if let Some(message) = self.primary_bundle.get_message(id).and_then(|m| m.value()) {
            let mut errs = Vec::new();
            return self
                .primary_bundle
                .format_pattern(message, args, &mut errs)
                .to_string();
        }

        // Fall back to English bundle if available
        if let Some(ref fallback) = self.fallback_bundle {
            if let Some(message) = fallback.get_message(id).and_then(|m| m.value()) {
                let mut errs = Vec::new();
                return fallback
                    .format_pattern(message, args, &mut errs)
                    .to_string();
            }
        }

        // Return the key ID if not found anywhere
        id.to_string()
    }
}

// Cache localizer. FluentResource cannot be shared between threads while FluentBundle can be shared
static UUCORE_FLUENT: OnceLock<FluentResource> = OnceLock::new();
static CHECKSUM_FLUENT: OnceLock<FluentResource> = OnceLock::new();
static UTIL_FLUENT: OnceLock<FluentResource> = OnceLock::new();
thread_local! {
    static LOCALIZER: OnceLock<Localizer> = const { OnceLock::new() };
}

/// Helper function to find the uucore locales directory from a utility's locales directory
fn find_uucore_locales_dir(utility_locales_dir: &Path) -> Option<PathBuf> {
    // Normalize the path to get absolute path
    let normalized_dir = utility_locales_dir
        .canonicalize()
        .unwrap_or_else(|_| utility_locales_dir.to_path_buf());

    // Walk up: locales -> printenv -> uu -> src
    let uucore_locales = normalized_dir
        .parent()? // printenv
        .parent()? // uu
        .parent()? // src
        .join("uucore")
        .join("locales");

    // Only return if the directory actually exists
    uucore_locales.exists().then_some(uucore_locales)
}

/// Create a bundle that combines common and utility-specific strings
fn create_bundle(
    locale: &LanguageIdentifier,
    locales_dir: &Path,
    util_name: &str,
) -> Result<FluentBundle<&'static FluentResource>, LocalizationError> {
    let mut bundle: FluentBundle<&'static FluentResource> = FluentBundle::new(vec![locale.clone()]);

    // Disable Unicode directional isolate characters
    bundle.set_use_isolating(false);

    let mut try_add_resource_from = |dir_opt: Option<PathBuf>| {
        if let Some(resource) = dir_opt
            .map(|dir| dir.join(format!("{locale}.ftl")))
            .and_then(|locale_path| fs::read_to_string(locale_path).ok())
            .and_then(|ftl| FluentResource::try_new(ftl).ok())
        {
            // use Box::leak to provide 'static lifetime for shared FluentBundle between threads
            bundle.add_resource_overriding(Box::leak(Box::new(resource)));
        }
    };

    // Load common strings from uucore locales directory
    try_add_resource_from(find_uucore_locales_dir(locales_dir));
    // Then, try to load utility-specific strings from the utility's locale directory
    try_add_resource_from(get_locales_dir(util_name).ok());

    // checksum binaries also require fluent files from the checksum_common crate
    if [
        "cksum",
        "b2sum",
        "md5sum",
        "sha1sum",
        "sha224sum",
        "sha256sum",
        "sha384sum",
        "sha512sum",
    ]
    .contains(&util_name)
    {
        try_add_resource_from(get_locales_dir("checksum_common").ok());
    }

    // If we have at least one resource, return the bundle
    if bundle.has_message("common-error") || bundle.has_message(&format!("{util_name}-about")) {
        Ok(bundle)
    } else {
        Err(LocalizationError::LocalesDirNotFound(format!(
            "No localization strings found for {locale} and utility {util_name}"
        )))
    }
}

/// Initialize localization with common strings in addition to utility-specific strings
fn init_localization(
    locale: &LanguageIdentifier,
    locales_dir: &Path,
    util_name: &str,
) -> Result<(), LocalizationError> {
    let default_locale = LanguageIdentifier::from_str(DEFAULT_LOCALE)
        .expect("Default locale should always be valid");

    // Try to create a bundle that combines common and utility-specific strings
    let english_bundle: FluentBundle<&'static FluentResource> =
        create_bundle(&default_locale, locales_dir, util_name).or_else(|_| {
            // Fallback to embedded utility-specific and common strings
            create_english_bundle_from_embedded(&default_locale, util_name)
        })?;

    let loc = if locale == &default_locale {
        // If requesting English, just use English as primary (no fallback needed)
        Localizer::new(english_bundle)
    } else {
        // Try to load the requested locale with common strings
        if let Ok(primary_bundle) = create_bundle(locale, locales_dir, util_name) {
            // Successfully loaded requested locale, load English as fallback
            Localizer::new(primary_bundle).with_fallback(english_bundle)
        } else {
            // Failed to load requested locale, just use English as primary
            Localizer::new(english_bundle)
        }
    };

    LOCALIZER.with(|lock| {
        lock.set(loc)
            .map_err(|_| LocalizationError::Bundle("Localizer already initialized".into()))
    })?;
    Ok(())
}

/// Helper function to parse FluentResource from content string
fn parse_fluent_resource(
    content: &str,
    cache: &'static OnceLock<FluentResource>,
) -> Result<&'static FluentResource, LocalizationError> {
    // global cache breaks unit tests
    #[cfg(not(test))]
    if let Some(res) = cache.get() {
        return Ok(res);
    }

    let resource = FluentResource::try_new(content.to_string()).map_err(
        |(_partial_resource, errs): (FluentResource, Vec<ParserError>)| {
            if let Some(first_err) = errs.into_iter().next() {
                let snippet = first_err
                    .slice
                    .clone()
                    .and_then(|range| content.get(range))
                    .unwrap_or("")
                    .to_string();
                LocalizationError::ParseResource {
                    error: first_err,
                    snippet,
                }
            } else {
                LocalizationError::LocalesDirNotFound("Parse error without details".to_string())
            }
        },
    )?;
    // global cache breaks unit tests
    if cfg!(not(test)) {
        Ok(cache.get_or_init(|| resource))
    } else {
        Ok(Box::leak(Box::new(resource)))
    }
}

/// Create a bundle from embedded English locale files with common uucore strings
fn create_english_bundle_from_embedded(
    locale: &LanguageIdentifier,
    util_name: &str,
) -> Result<FluentBundle<&'static FluentResource>, LocalizationError> {
    // Only support English from embedded files
    if *locale != "en-US" {
        return Err(LocalizationError::LocalesDirNotFound(
            "Embedded locales only support en-US".to_string(),
        ));
    }

    let mut bundle: FluentBundle<&'static FluentResource> = FluentBundle::new(vec![locale.clone()]);
    bundle.set_use_isolating(false);

    // First, try to load common uucore strings
    if let Some(uucore_content) = get_embedded_locale("uucore/en-US.ftl") {
        let uucore_resource = parse_fluent_resource(uucore_content, &UUCORE_FLUENT)?;
        bundle.add_resource_overriding(uucore_resource);
    }

    // Checksum algorithms need locale messages from checksum_common
    if util_name.ends_with("sum") {
        if let Some(uucore_content) = get_embedded_locale("checksum_common/en-US.ftl") {
            let uucore_resource = parse_fluent_resource(uucore_content, &CHECKSUM_FLUENT)?;
            bundle.add_resource_overriding(uucore_resource);
        }
    }

    // Then, try to load utility-specific strings
    let locale_key = format!("{util_name}/en-US.ftl");
    if let Some(ftl_content) = get_embedded_locale(&locale_key) {
        let resource = parse_fluent_resource(ftl_content, &UTIL_FLUENT)?;
        bundle.add_resource_overriding(resource);
    }

    // Return the bundle if we have either common strings or utility-specific strings
    if bundle.has_message("common-error") || bundle.has_message(&format!("{util_name}-about")) {
        Ok(bundle)
    } else {
        Err(LocalizationError::LocalesDirNotFound(format!(
            "No embedded locale found for {util_name} and no common strings found"
        )))
    }
}

/// Create a bundle from embedded locale files for any locale on WASI.
/// Bypasses the global OnceLock cache (uses Box::leak) so it can be
/// called for multiple locales in the same process.
#[cfg(target_os = "wasi")]
fn create_wasi_bundle_from_embedded(
    locale: &LanguageIdentifier,
    util_name: &str,
) -> Result<FluentBundle<&'static FluentResource>, LocalizationError> {
    let locale_str = locale.to_string();
    let mut bundle: FluentBundle<&'static FluentResource> = FluentBundle::new(vec![locale.clone()]);
    bundle.set_use_isolating(false);

    let mut try_add = |key: &str| {
        if let Some(content) = get_embedded_locale(key) {
            if let Ok(resource) = FluentResource::try_new(content.to_string()) {
                bundle.add_resource_overriding(Box::leak(Box::new(resource)));
            }
        }
    };

    try_add(&format!("uucore/{locale_str}.ftl"));
    if util_name.ends_with("sum") {
        try_add(&format!("checksum_common/{locale_str}.ftl"));
    }
    try_add(&format!("{util_name}/{locale_str}.ftl"));

    if bundle.has_message("common-error") || bundle.has_message(&format!("{util_name}-about")) {
        Ok(bundle)
    } else {
        Err(LocalizationError::LocalesDirNotFound(format!(
            "No embedded locale found for {util_name}/{locale_str}"
        )))
    }
}

fn get_message_internal(id: &str, args: Option<FluentArgs>) -> String {
    LOCALIZER.with(|lock| {
        lock.get()
            .map_or_else(|| id.to_string(), |loc| loc.format(id, args.as_ref())) // Return the key ID if localizer not initialized
    })
}

/// Retrieves a localized message by its identifier.
///
/// Looks up a message with the given ID in the current locale bundle and returns
/// the localized text. If the message ID is not found in the current locale,
/// it will fall back to English. If the message is not found in English either,
/// returns the message ID itself.
///
/// # Arguments
///
/// * `id` - The message identifier in the Fluent resources
///
/// # Returns
///
/// A `String` containing the localized message, or the message ID if not found
///
/// # Examples
///
/// ```
/// use uucore::locale::get_message;
///
/// // Get a localized greeting (from .ftl files)
/// let greeting = get_message("greeting");
/// println!("{greeting}");
/// ```
pub fn get_message(id: &str) -> String {
    get_message_internal(id, None)
}

/// Retrieves a localized message with variable substitution.
///
/// Looks up a message with the given ID in the current locale bundle,
/// substitutes variables from the provided arguments map, and returns the
/// localized text. If the message ID is not found in the current locale,
/// it will fall back to English. If the message is not found in English either,
/// returns the message ID itself.
///
/// # Arguments
///
/// * `id` - The message identifier in the Fluent resources
/// * `ftl_args` - Key-value pairs for variable substitution in the message
///
/// # Returns
///
/// A `String` containing the localized message with variable substitution, or the message ID if not found
///
/// # Examples
///
/// ```
/// use uucore::locale::get_message_with_args;
/// use fluent::FluentArgs;
///
/// // For a Fluent message like: "Hello, { $name }! You have { $count } notifications."
/// let mut args = FluentArgs::new();
/// args.set("name".to_string(), "Alice".to_string());
/// args.set("count".to_string(), 3);
///
/// let message = get_message_with_args("notification", args);
/// println!("{message}");
/// ```
pub fn get_message_with_args(id: &str, ftl_args: FluentArgs) -> String {
    get_message_internal(id, Some(ftl_args))
}

/// Function to detect system locale from environment variables
fn detect_system_locale() -> Result<LanguageIdentifier, LocalizationError> {
    let locale_str = std::env::var("LANG")
        .unwrap_or_else(|_| DEFAULT_LOCALE.to_string())
        .split('.')
        .next()
        .unwrap_or(DEFAULT_LOCALE)
        .to_string();
    LanguageIdentifier::from_str(&locale_str).map_err(|_| {
        LocalizationError::ParseLocale(format!("Failed to parse locale: {locale_str}"))
    })
}

/// Sets up localization using the system locale with English fallback.
/// Always loads common strings in addition to utility-specific strings.
///
/// This function initializes the localization system based on the system's locale
/// preferences (via the LANG environment variable) or falls back to English
/// if the system locale cannot be determined or the locale file doesn't exist.
/// English is always loaded as a fallback.
///
/// # Arguments
///
/// * `p` - Path to the directory containing localization (.ftl) files
///
/// # Returns
///
/// * `Ok(())` if initialization succeeds
/// * `Err(LocalizationError)` if initialization fails
///
/// # Errors
///
/// Returns a `LocalizationError` if:
/// * The en-US.ftl file cannot be read (English is required)
/// * The files contain invalid Fluent syntax
/// * The bundle cannot be initialized properly
///
/// # Examples
///
/// ```
/// use uucore::locale::setup_localization;
///
/// // Initialize localization using files in the "locales" directory
/// // Make sure you have at least an "en-US.ftl" file in this directory
/// // Other locale files like "fr-FR.ftl" are optional
/// match setup_localization("./locales") {
///     Ok(_) => println!("Localization initialized successfully"),
///     Err(e) => eprintln!("Failed to initialize localization: {e}"),
/// }
/// ```
pub fn setup_localization(p: &str) -> Result<(), LocalizationError> {
    // Avoid duplicated and high-cost localizer setup
    thread_local! {
        static LOCALIZER_IS_SET: Cell<bool> = const { Cell::new(false) };
    }
    if LOCALIZER_IS_SET.with(Cell::get) {
        return Ok(());
    }

    let locale = detect_system_locale().unwrap_or_else(|_| {
        LanguageIdentifier::from_str(DEFAULT_LOCALE).expect("Default locale should always be valid")
    });

    // Load common strings along with utility-specific strings
    if let Ok(locales_dir) = get_locales_dir(p) {
        // Load both utility-specific and common strings
        init_localization(&locale, &locales_dir, p)?;
    } else {
        // No locales directory found, use embedded locales
        let default_locale = LanguageIdentifier::from_str(DEFAULT_LOCALE)
            .expect("Default locale should always be valid");

        #[cfg(target_os = "wasi")]
        let localizer = {
            let english_bundle = create_wasi_bundle_from_embedded(&default_locale, p)?;
            if locale == default_locale {
                Localizer::new(english_bundle)
            } else if let Ok(localized) = create_wasi_bundle_from_embedded(&locale, p) {
                Localizer::new(localized).with_fallback(english_bundle)
            } else {
                Localizer::new(english_bundle)
            }
        };

        #[cfg(not(target_os = "wasi"))]
        let localizer = {
            let english_bundle = create_english_bundle_from_embedded(&default_locale, p)?;
            Localizer::new(english_bundle)
        };

        LOCALIZER.with(|lock| {
            lock.set(localizer)
                .map_err(|_| LocalizationError::Bundle("Localizer already initialized".into()))
        })?;
    }
    LOCALIZER_IS_SET.with(|f| f.set(true));
    Ok(())
}

#[cfg(not(debug_assertions))]
fn resolve_locales_dir_from_exe_dir(exe_dir: &Path, p: &str) -> Option<PathBuf> {
    // 1. <bindir>/locales/<prog>
    let coreutils = exe_dir.join("locales").join(p);
    if coreutils.is_dir() {
        return Some(coreutils);
    }

    // 2. <prefix>/share/locales/<prog>
    if let Some(prefix) = exe_dir.parent() {
        let fhs = prefix.join("share").join("locales").join(p);
        if fhs.is_dir() {
            return Some(fhs);
        }
    }

    // 3. <bindir>/<prog>   (legacy fall-back)
    let fallback = exe_dir.join(p);
    if fallback.is_dir() {
        return Some(fallback);
    }

    None
}

/// Helper function to get the locales directory based on the build configuration
fn get_locales_dir(p: &str) -> Result<PathBuf, LocalizationError> {
    #[cfg(debug_assertions)]
    {
        // During development, use the project's locales directory
        let manifest_dir = env!("CARGO_MANIFEST_DIR");
        // from uucore path, load the locales directory from the program directory
        let dev_path = PathBuf::from(manifest_dir)
            .join("../uu")
            .join(p)
            .join("locales");

        if dev_path.exists() {
            return Ok(dev_path);
        }

        // Fallback for development if the expected path doesn't exist
        let fallback_dev_path = PathBuf::from(manifest_dir).join(p);
        if fallback_dev_path.exists() {
            return Ok(fallback_dev_path);
        }

        Err(LocalizationError::LocalesDirNotFound(format!(
            "Development locales directory not found at {} or {}",
            dev_path.quote(),
            fallback_dev_path.quote()
        )))
    }

    #[cfg(not(debug_assertions))]
    {
        use std::env;
        // In release builds, look relative to executable
        let exe_path = env::current_exe().map_err(|e| {
            LocalizationError::PathResolution(format!("Failed to get executable path: {e}"))
        })?;

        let exe_dir = exe_path.parent().ok_or_else(|| {
            LocalizationError::PathResolution("Failed to get executable directory".to_string())
        })?;

        if let Some(dir) = resolve_locales_dir_from_exe_dir(exe_dir, p) {
            return Ok(dir);
        }

        Err(LocalizationError::LocalesDirNotFound(format!(
            "Release locales directory not found starting from {}",
            exe_dir.quote()
        )))
    }
}

/// Macro for retrieving localized messages with optional arguments.
///
/// This macro provides a unified interface for both simple message retrieval
/// and message retrieval with variable substitution. It accepts a message ID
/// and optionally key-value pairs using the `"key" => value` syntax.
///
/// # Arguments
///
/// * `$id` - The message identifier string
/// * Optional key-value pairs in the format `"key" => value`
///
/// # Examples
///
/// ```
/// use uucore::translate;
/// use fluent::FluentArgs;
///
/// // Simple message without arguments
/// let greeting = translate!("greeting");
///
/// // Message with one argument
/// let welcome = translate!("welcome", "name" => "Alice");
///
/// // Message with multiple arguments
/// let username = "user name";
/// let item_count = 2;
/// let notification = translate!(
///     "user-stats",
///     "name" => username,
///     "count" => item_count,
///     "status" => "active"
/// );
/// ```
#[macro_export]
macro_rules! translate {
    // Case 1: Message ID only (no arguments)
    ($id:expr) => {
        $crate::locale::get_message($id)
    };

    // Case 2: Message ID with key-value arguments
    ($id:expr, $($key:expr => $value:expr),+ $(,)?) => {
        {
            let mut args = fluent::FluentArgs::new();
            $(
                let value_str = $value.to_string();
                if let Ok(num_val) = value_str.parse::<i64>() {
                    args.set($key, num_val);
                } else if let Ok(float_val) = value_str.parse::<f64>() {
                    args.set($key, float_val);
                } else {
                    // Keep as string if not a number
                    args.set($key, value_str);
                }
            )+
            $crate::locale::get_message_with_args($id, args)
        }
    };
}

// Re-export the macro for easier access
pub use translate;

#[cfg(test)]
mod tests {
    use super::*;
    use std::env;
    use std::fs;
    use std::path::PathBuf;
    use tempfile::TempDir;

    /// Test-specific helper function to create a bundle from test directory only
    #[cfg(test)]
    fn create_test_bundle(
        locale: &LanguageIdentifier,
        test_locales_dir: &Path,
    ) -> Result<FluentBundle<&'static FluentResource>, LocalizationError> {
        let mut bundle: FluentBundle<&'static FluentResource> =
            FluentBundle::new(vec![locale.clone()]);
        bundle.set_use_isolating(false);

        // Only load from the test directory - no common strings or utility-specific paths
        let locale_path = test_locales_dir.join(format!("{locale}.ftl"));
        if let Ok(ftl_content) = fs::read_to_string(&locale_path) {
            let resource = parse_fluent_resource(&ftl_content, &UUCORE_FLUENT)?;
            bundle.add_resource_overriding(resource);
            return Ok(bundle);
        }

        Err(LocalizationError::LocalesDirNotFound(format!(
            "No localization strings found for {locale} in {}",
            test_locales_dir.quote()
        )))
    }

    /// Test-specific initialization function for test directories
    #[cfg(test)]
    fn init_test_localization(
        locale: &LanguageIdentifier,
        test_locales_dir: &Path,
    ) -> Result<(), LocalizationError> {
        let default_locale = LanguageIdentifier::from_str(DEFAULT_LOCALE)
            .expect("Default locale should always be valid");

        // Create English bundle from test directory
        let english_bundle = create_test_bundle(&default_locale, test_locales_dir)?;

        let loc = if locale == &default_locale {
            // If requesting English, just use English as primary
            Localizer::new(english_bundle)
        } else {
            // Try to load the requested locale from test directory
            if let Ok(primary_bundle) = create_test_bundle(locale, test_locales_dir) {
                // Successfully loaded requested locale, load English as fallback
                Localizer::new(primary_bundle).with_fallback(english_bundle)
            } else {
                // Failed to load requested locale, just use English as primary
                Localizer::new(english_bundle)
            }
        };

        LOCALIZER.with(|lock| {
            lock.set(loc)
                .map_err(|_| LocalizationError::Bundle("Localizer already initialized".into()))
        })?;
        Ok(())
    }

    /// Helper function to create a temporary directory with test locale files
    fn create_test_locales_dir() -> TempDir {
        let temp_dir = TempDir::new().expect("Failed to create temp directory");

        // Create en-US.ftl
        let en_content = r"
greeting = Hello, world!
welcome = Welcome, { $name }!
count-items = You have { $count ->
    [one] { $count } item
   *[other] { $count } items
}
missing-in-other = This message only exists in English
";

        // Create fr-FR.ftl
        let fr_content = r"
greeting = Bonjour, le monde!
welcome = Bienvenue, { $name }!
count-items = Vous avez { $count ->
    [one] { $count } élément
   *[other] { $count } éléments
}
";

        // Create ja-JP.ftl (Japanese)
        let ja_content = r"
greeting = こんにちは、世界！
welcome = ようこそ、{ $name }さん！
count-items = { $count }個のアイテムがあります
";

        // Create ar-SA.ftl (Arabic - Right-to-Left)
        let ar_content = r"
greeting = أهلاً بالعالم！
welcome = أهلاً وسهلاً، { $name }！
count-items = لديك { $count ->
    [zero] لا عناصر
    [one] عنصر واحد
    [two] عنصران
    [few] { $count } عناصر
   *[other] { $count } عنصر
}
";

        // Create es-ES.ftl with invalid syntax
        let es_invalid_content = r"
greeting = Hola, mundo!
invalid-syntax = This is { $missing
";

        fs::write(temp_dir.path().join("en-US.ftl"), en_content)
            .expect("Failed to write en-US.ftl");
        fs::write(temp_dir.path().join("fr-FR.ftl"), fr_content)
            .expect("Failed to write fr-FR.ftl");
        fs::write(temp_dir.path().join("ja-JP.ftl"), ja_content)
            .expect("Failed to write ja-JP.ftl");
        fs::write(temp_dir.path().join("ar-SA.ftl"), ar_content)
            .expect("Failed to write ar-SA.ftl");
        fs::write(temp_dir.path().join("es-ES.ftl"), es_invalid_content)
            .expect("Failed to write es-ES.ftl");

        temp_dir
    }

    #[test]
    fn test_create_bundle_success() {
        let temp_dir = create_test_locales_dir();
        let locale = LanguageIdentifier::from_str("en-US").unwrap();

        let result = create_test_bundle(&locale, temp_dir.path());
        assert!(result.is_ok());

        let bundle = result.unwrap();
        assert!(bundle.get_message("greeting").is_some());
    }

    #[test]
    fn test_create_bundle_file_not_found() {
        let temp_dir = TempDir::new().unwrap();
        let locale = LanguageIdentifier::from_str("de-DE").unwrap();

        let result = create_test_bundle(&locale, temp_dir.path());
        assert!(result.is_err());

        if let Err(LocalizationError::LocalesDirNotFound(_)) = result {
            // Expected - no localization strings found
        } else {
            panic!("Expected LocalesDirNotFound error");
        }
    }

    #[test]
    fn test_create_bundle_invalid_syntax() {
        let temp_dir = create_test_locales_dir();
        let locale = LanguageIdentifier::from_str("es-ES").unwrap();

        let result = create_test_bundle(&locale, temp_dir.path());

        // The result should be an error due to invalid syntax
        match result {
            Err(LocalizationError::ParseResource {
                error: _parser_err,
                snippet: _,
            }) => {
                // Expected ParseResource variant - test passes
            }
            Ok(_) => {
                panic!("Expected ParseResource error, but bundle was created successfully");
            }
            Err(other) => {
                panic!("Expected ParseResource error, but got: {other:?}");
            }
        }
    }

    #[test]
    fn test_localizer_format_primary_bundle() {
        let temp_dir = create_test_locales_dir();
        let en_bundle: FluentBundle<&'static FluentResource> = create_test_bundle(
            &LanguageIdentifier::from_str("en-US").unwrap(),
            temp_dir.path(),
        )
        .unwrap();

        let localizer = Localizer::new(en_bundle);
        let result = localizer.format("greeting", None);
        assert_eq!(result, "Hello, world!");
    }

    #[test]
    fn test_localizer_format_with_args() {
        use fluent::FluentArgs;
        let temp_dir = create_test_locales_dir();
        let en_bundle = create_test_bundle(
            &LanguageIdentifier::from_str("en-US").unwrap(),
            temp_dir.path(),
        )
        .unwrap();

        let localizer = Localizer::new(en_bundle);
        let mut args = FluentArgs::new();
        args.set("name", "Alice");

        let result = localizer.format("welcome", Some(&args));
        assert_eq!(result, "Welcome, Alice!");
    }

    #[test]
    fn test_localizer_fallback_to_english() {
        let temp_dir = create_test_locales_dir();
        let fr_bundle = create_test_bundle(
            &LanguageIdentifier::from_str("fr-FR").unwrap(),
            temp_dir.path(),
        )
        .unwrap();
        let en_bundle = create_test_bundle(
            &LanguageIdentifier::from_str("en-US").unwrap(),
            temp_dir.path(),
        )
        .unwrap();

        let localizer = Localizer::new(fr_bundle).with_fallback(en_bundle);

        // This message exists in French
        let result1 = localizer.format("greeting", None);
        assert_eq!(result1, "Bonjour, le monde!");

        // This message only exists in English, should fallback
        let result2 = localizer.format("missing-in-other", None);
        assert_eq!(result2, "This message only exists in English");
    }

    #[test]
    fn test_localizer_format_message_not_found() {
        let temp_dir = create_test_locales_dir();
        let en_bundle = create_test_bundle(
            &LanguageIdentifier::from_str("en-US").unwrap(),
            temp_dir.path(),
        )
        .unwrap();

        let localizer = Localizer::new(en_bundle);
        let result = localizer.format("nonexistent-message", None);
        assert_eq!(result, "nonexistent-message");
    }

    #[test]
    fn test_init_localization_english_only() {
        // Run in a separate thread to avoid conflicts with other tests
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("en-US").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test that we can get messages
            let message = get_message("greeting");
            assert_eq!(message, "Hello, world!");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_init_localization_with_fallback() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("fr-FR").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test French message
            let message1 = get_message("greeting");
            assert_eq!(message1, "Bonjour, le monde!");

            // Test fallback to English
            let message2 = get_message("missing-in-other");
            assert_eq!(message2, "This message only exists in English");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_init_localization_invalid_locale_falls_back_to_english() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("de-DE").unwrap(); // No German file

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Should use English as primary since German failed to load
            let message = get_message("greeting");
            assert_eq!(message, "Hello, world!");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_init_localization_already_initialized() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("en-US").unwrap();

            // Initialize once
            let result1 = init_test_localization(&locale, temp_dir.path());
            assert!(result1.is_ok());

            // Try to initialize again - should fail
            let result2 = init_test_localization(&locale, temp_dir.path());
            assert!(result2.is_err());

            match result2 {
                Err(LocalizationError::Bundle(msg)) => {
                    assert!(msg.contains("already initialized"));
                }
                _ => panic!("Expected Bundle error"),
            }
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_get_message() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("fr-FR").unwrap();

            init_test_localization(&locale, temp_dir.path()).unwrap();

            let message = get_message("greeting");
            assert_eq!(message, "Bonjour, le monde!");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_get_message_with_args() {
        use fluent::FluentArgs;
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("en-US").unwrap();

            init_test_localization(&locale, temp_dir.path()).unwrap();

            let mut args = FluentArgs::new();
            args.set("name".to_string(), "Bob".to_string());

            let message = get_message_with_args("welcome", args);
            assert_eq!(message, "Welcome, Bob!");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_get_message_with_args_pluralization() {
        use fluent::FluentArgs;
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("en-US").unwrap();

            init_test_localization(&locale, temp_dir.path()).unwrap();

            // Test singular
            let mut args1 = FluentArgs::new();
            args1.set("count", 1);
            let message1 = get_message_with_args("count-items", args1);
            assert_eq!(message1, "You have 1 item");

            // Test plural
            let mut args2 = FluentArgs::new();
            args2.set("count", 5);
            let message2 = get_message_with_args("count-items", args2);
            assert_eq!(message2, "You have 5 items");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_thread_local_isolation() {
        use std::thread;

        let temp_dir = create_test_locales_dir();

        // Initialize in main thread with French
        let temp_path_main = temp_dir.path().to_path_buf();
        let main_handle = thread::spawn(move || {
            let locale = LanguageIdentifier::from_str("fr-FR").unwrap();
            init_test_localization(&locale, &temp_path_main).unwrap();
            let main_message = get_message("greeting");
            assert_eq!(main_message, "Bonjour, le monde!");
        });
        main_handle.join().unwrap();

        // Test in a different thread - should not be initialized
        let temp_path = temp_dir.path().to_path_buf();
        let handle = thread::spawn(move || {
            // This thread should have its own uninitialized LOCALIZER
            let thread_message = get_message("greeting");
            assert_eq!(thread_message, "greeting"); // Returns ID since not initialized

            // Initialize in this thread with English
            let en_locale = LanguageIdentifier::from_str("en-US").unwrap();
            init_test_localization(&en_locale, &temp_path).unwrap();
            let thread_message_after_init = get_message("greeting");
            assert_eq!(thread_message_after_init, "Hello, world!");
        });

        handle.join().unwrap();

        // Test another thread to verify French doesn't persist across threads
        let final_handle = thread::spawn(move || {
            // Should be uninitialized again
            let final_message = get_message("greeting");
            assert_eq!(final_message, "greeting");
        });
        final_handle.join().unwrap();
    }

    #[test]
    fn test_japanese_localization() {
        use fluent::FluentArgs;
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("ja-JP").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test Japanese greeting
            let message = get_message("greeting");
            assert_eq!(message, "こんにちは、世界！");

            // Test Japanese with arguments
            let mut args = FluentArgs::new();
            args.set("name".to_string(), "田中".to_string());
            let welcome = get_message_with_args("welcome", args);
            assert_eq!(welcome, "ようこそ、田中さん！");

            // Test Japanese count (no pluralization)
            let mut count_args = FluentArgs::new();
            count_args.set("count".to_string(), "5".to_string());
            let count_message = get_message_with_args("count-items", count_args);
            assert_eq!(count_message, "5個のアイテムがあります");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_arabic_localization() {
        use fluent::FluentArgs;
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("ar-SA").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test Arabic greeting (RTL text)
            let message = get_message("greeting");
            assert_eq!(message, "أهلاً بالعالم！");

            // Test Arabic with arguments
            let mut args = FluentArgs::new();
            args.set("name", "أحمد".to_string());
            let welcome = get_message_with_args("welcome", args);
            assert_eq!(welcome, "أهلاً وسهلاً، أحمد！");

            // Test Arabic pluralization (zero case)
            let mut args_zero = FluentArgs::new();
            args_zero.set("count", 0);
            let message_zero = get_message_with_args("count-items", args_zero);
            assert_eq!(message_zero, "لديك لا عناصر");

            // Test Arabic pluralization (one case)
            let mut args_one = FluentArgs::new();
            args_one.set("count", 1);
            let message_one = get_message_with_args("count-items", args_one);
            assert_eq!(message_one, "لديك عنصر واحد");

            // Test Arabic pluralization (two case)
            let mut args_two = FluentArgs::new();
            args_two.set("count", 2);
            let message_two = get_message_with_args("count-items", args_two);
            assert_eq!(message_two, "لديك عنصران");

            // Test Arabic pluralization (few case - 3-10)
            let mut args_few = FluentArgs::new();
            args_few.set("count", 5);
            let message_few = get_message_with_args("count-items", args_few);
            assert_eq!(message_few, "لديك 5 عناصر");

            // Test Arabic pluralization (other case - 11+)
            let mut args_many = FluentArgs::new();
            args_many.set("count", 15);
            let message_many = get_message_with_args("count-items", args_many);
            assert_eq!(message_many, "لديك 15 عنصر");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_arabic_localization_with_macro() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("ar-SA").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test Arabic greeting (RTL text)
            let message = translate!("greeting");
            assert_eq!(message, "أهلاً بالعالم！");

            // Test Arabic with arguments
            let welcome = translate!("welcome", "name" => "أحمد");
            assert_eq!(welcome, "أهلاً وسهلاً، أحمد！");

            // Test Arabic pluralization (zero case)
            let message_zero = translate!("count-items", "count" => 0);
            assert_eq!(message_zero, "لديك لا عناصر");

            // Test Arabic pluralization (one case)
            let message_one = translate!("count-items", "count" => 1);
            assert_eq!(message_one, "لديك عنصر واحد");

            // Test Arabic pluralization (two case)
            let message_two = translate!("count-items", "count" => 2);
            assert_eq!(message_two, "لديك عنصران");

            // Test Arabic pluralization (few case - 3-10)
            let message_few = translate!("count-items", "count" => 5);
            assert_eq!(message_few, "لديك 5 عناصر");

            // Test Arabic pluralization (other case - 11+)
            let message_many = translate!("count-items", "count" => 15);
            assert_eq!(message_many, "لديك 15 عنصر");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_mixed_script_fallback() {
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("ar-SA").unwrap();

            let result = init_test_localization(&locale, temp_dir.path());
            assert!(result.is_ok());

            // Test Arabic message exists
            let arabic_message = get_message("greeting");
            assert_eq!(arabic_message, "أهلاً بالعالم！");

            // Test fallback to English for missing message
            let fallback_message = get_message("missing-in-other");
            assert_eq!(fallback_message, "This message only exists in English");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_unicode_directional_isolation_disabled() {
        use fluent::FluentArgs;
        std::thread::spawn(|| {
            let temp_dir = create_test_locales_dir();
            let locale = LanguageIdentifier::from_str("ar-SA").unwrap();

            init_test_localization(&locale, temp_dir.path()).unwrap();

            // Test that Latin script names are NOT isolated in RTL context
            // since we disabled Unicode directional isolation
            let mut args = FluentArgs::new();
            args.set("name".to_string(), "John Smith".to_string());
            let message = get_message_with_args("welcome", args);

            // The Latin name should NOT be wrapped in directional isolate characters
            assert!(!message.contains("\u{2068}John Smith\u{2069}"));
            assert_eq!(message, "أهلاً وسهلاً، John Smith！");
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_parse_resource_error_includes_snippet() {
        let temp_dir = create_test_locales_dir();
        let locale = LanguageIdentifier::from_str("es-ES").unwrap();

        let result = create_test_bundle(&locale, temp_dir.path());
        assert!(result.is_err());

        if let Err(LocalizationError::ParseResource {
            error: _err,
            snippet,
        }) = result
        {
            // The snippet should contain exactly the invalid text from es-ES.ftl
            assert!(
                snippet.contains("This is { $missing"),
                "snippet was `{snippet}` but did not include the invalid text"
            );
        } else {
            panic!("Expected LocalizationError::ParseResource with snippet");
        }
    }

    #[test]
    fn test_localization_error_from_io_error() {
        let io_error = std::io::Error::new(std::io::ErrorKind::NotFound, "File not found");
        let loc_error = LocalizationError::from(io_error);

        match loc_error {
            LocalizationError::Io { source: _, path } => {
                assert_eq!(path, PathBuf::from("<unknown>"));
            }
            _ => panic!("Expected IO error variant"),
        }
    }

    #[test]
    fn test_localization_error_uerror_impl() {
        let error = LocalizationError::Bundle("some error".to_string());
        assert_eq!(error.code(), 1);
    }

    #[test]
    fn test_get_message_not_initialized() {
        std::thread::spawn(|| {
            let message = get_message("greeting");
            assert_eq!(message, "greeting"); // Should return the ID itself
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_detect_system_locale_from_lang_env() {
        // Test locale parsing logic directly instead of relying on environment variables
        // which can have race conditions in multi-threaded test environments

        // Test parsing logic with UTF-8 encoding
        let locale_with_encoding = "fr-FR.UTF-8";
        let parsed = locale_with_encoding.split('.').next().unwrap();
        let lang_id = LanguageIdentifier::from_str(parsed).unwrap();
        assert_eq!(lang_id.to_string(), "fr-FR");

        // Test parsing logic without encoding
        let locale_without_encoding = "es-ES";
        let lang_id = LanguageIdentifier::from_str(locale_without_encoding).unwrap();
        assert_eq!(lang_id.to_string(), "es-ES");

        // Test that DEFAULT_LOCALE is valid
        let default_lang_id = LanguageIdentifier::from_str(DEFAULT_LOCALE).unwrap();
        assert_eq!(default_lang_id.to_string(), "en-US");
    }

    #[test]
    fn test_detect_system_locale_no_lang_env() {
        // Save current LANG value
        let original_lang = env::var("LANG").ok();

        // Remove LANG environment variable
        unsafe {
            env::remove_var("LANG");
        }

        let result = detect_system_locale();
        assert!(result.is_ok());
        assert_eq!(result.unwrap().to_string(), "en-US");

        // Restore original LANG value
        if let Some(val) = original_lang {
            unsafe {
                env::set_var("LANG", val);
            }
        } else {
            {} // Was already unset
        }
    }

    #[test]
    fn test_setup_localization_success() {
        std::thread::spawn(|| {
            // Save current LANG value
            let original_lang = env::var("LANG").ok();
            unsafe {
                env::set_var("LANG", "en-US.UTF-8"); // Use English since we have embedded resources for "test"
            }

            let result = setup_localization("test");
            assert!(result.is_ok());

            // Test that we can get messages (should use embedded English for "test" utility)
            let message = get_message("test-about");
            // Since we're using embedded resources, we should get the expected message
            assert!(!message.is_empty());

            // Restore original LANG value
            if let Some(val) = original_lang {
                unsafe {
                    env::set_var("LANG", val);
                }
            } else {
                unsafe {
                    env::remove_var("LANG");
                }
            }
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_setup_localization_falls_back_to_english() {
        std::thread::spawn(|| {
            // Save current LANG value
            let original_lang = env::var("LANG").ok();
            unsafe {
                env::set_var("LANG", "de-DE.UTF-8"); // German file doesn't exist, should fallback
            }

            let result = setup_localization("test");
            assert!(result.is_ok());

            // Should fall back to English embedded resources
            let message = get_message("test-about");
            assert!(!message.is_empty()); // Should get something, not just the key

            // Restore original LANG value
            if let Some(val) = original_lang {
                unsafe {
                    env::set_var("LANG", val);
                }
            } else {
                unsafe {
                    env::remove_var("LANG");
                }
            }
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_setup_localization_fallback_to_embedded() {
        std::thread::spawn(|| {
            // Force English locale for this test
            unsafe {
                env::set_var("LANG", "en-US");
            }

            // Test with a utility name that has embedded locales
            // This should fall back to embedded English when filesystem files aren't found
            let result = setup_localization("test");
            if let Err(e) = &result {
                eprintln!("Setup localization failed: {e}");
            }
            assert!(result.is_ok());

            // Verify we can get messages (using embedded English)
            let message = get_message("test-about");
            assert_eq!(message, "Check file types and compare values."); // Should use embedded English
        })
        .join()
        .unwrap();
    }

    #[test]
    fn test_error_display() {
        let io_error = LocalizationError::Io {
            source: std::io::Error::new(std::io::ErrorKind::NotFound, "File not found"),
            path: PathBuf::from("/test/path.ftl"),
        };
        let error_string = format!("{io_error}");
        assert!(error_string.contains("I/O error loading"));
        assert!(error_string.contains("/test/path.ftl"));

        let bundle_error = LocalizationError::Bundle("Bundle creation failed".to_string());
        let bundle_string = format!("{bundle_error}");
        assert!(bundle_string.contains("Bundle error: Bundle creation failed"));
    }

    #[test]
    fn test_clap_localization_fallbacks() {
        std::thread::spawn(|| {
            // Test the scenario where localization isn't properly initialized
            // and we need fallbacks for clap error handling

            // First, test when localizer is not initialized
            let error_msg = get_message("common-error");
            assert_eq!(error_msg, "common-error"); // Should return key when not initialized

            let tip_msg = get_message("common-tip");
            assert_eq!(tip_msg, "common-tip"); // Should return key when not initialized

            // Now initialize with setup_localization
            let result = setup_localization("comm");
            if result.is_err() {
                // If setup fails (e.g., no embedded locales for comm), try with a known utility
                let _ = setup_localization("test");
            }

            // Test that common strings are available after initialization
            let error_after_init = get_message("common-error");
            // Should either be translated or return the key (but not panic)
            assert!(!error_after_init.is_empty());

            let tip_after_init = get_message("common-tip");
            assert!(!tip_after_init.is_empty());

            // Test that clap error keys work with fallbacks
            let unknown_arg_key = get_message("clap-error-unexpected-argument");
            assert!(!unknown_arg_key.is_empty());

            // Test usage key fallback
            let usage_key = get_message("common-usage");
            assert!(!usage_key.is_empty());
        })
        .join()
        .unwrap();
    }
}

#[cfg(all(test, not(debug_assertions)))]
mod fhs_tests {
    use super::*;
    use tempfile::TempDir;

    #[test]
    fn resolves_fhs_share_locales_layout() {
        // 1. Set up a fake installation prefix in a temp directory
        let prefix = TempDir::new().unwrap(); // e.g.  /tmp/xyz
        let bin_dir = prefix.path().join("bin"); //        /tmp/xyz/bin
        let share_dir = prefix.path().join("share").join("locales").join("cut"); // /tmp/xyz/share/locales/cut
        std::fs::create_dir_all(&share_dir).unwrap();
        std::fs::create_dir_all(&bin_dir).unwrap();

        // 2. Pretend the executable lives in <prefix>/bin
        let exe_dir = bin_dir.as_path();

        // 3. Ask the helper to resolve the locales dir
        let result = resolve_locales_dir_from_exe_dir(exe_dir, "cut")
            .expect("should find locales via FHS path");

        assert_eq!(result, share_dir);
    }
}
