fastsync 0.7.0

use std::fmt::Display;

use rust_i18n::t;

/// fastsync 支持的用户界面语言。
///
/// 该枚举只影响 CLI 帮助、文本摘要和用户可见错误，不改变 JSON 字段与同步语义。
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Language {
    En,
    ZhCn,
}

impl Language {
    pub const DEFAULT: Self = Self::En;

    /// 返回 rust-i18n 使用的 locale 标识。
    pub fn as_locale(self) -> &'static str {
        match self {
            Self::En => "en",
            Self::ZhCn => "zh-CN",
        }
    }

    /// 解析 CLI 或环境变量中的语言标识。
    pub fn parse(raw: &str) -> Option<Self> {
        for candidate in raw.split(':') {
            if let Some(language) = Self::parse_one(candidate) {
                return Some(language);
            }
        }

        None
    }

    /// 从 `FASTSYNC_LANG` 或系统 locale 环境变量读取语言，非法值会被忽略。
    pub fn from_env() -> Option<Self> {
        language_from_env_var("FASTSYNC_LANG").or_else(Self::from_system_env)
    }

    /// 从系统 locale 环境变量读取语言，用于适配 Linux/macOS 终端环境。
    pub fn from_system_env() -> Option<Self> {
        ["LC_ALL", "LC_MESSAGES", "LANGUAGE", "LANG"]
            .into_iter()
            .find_map(language_from_env_var)
    }

    fn parse_one(raw: &str) -> Option<Self> {
        let normalized = normalize_locale(raw)?;

        if matches!(normalized.as_str(), "c" | "posix") || normalized.starts_with("en") {
            return Some(Self::En);
        }

        if normalized == "cn"
            || normalized == "chinese"
            || normalized == "中文"
            || normalized.starts_with("zh")
        {
            return Some(Self::ZhCn);
        }

        None
    }
}

fn language_from_env_var(name: &str) -> Option<Language> {
    std::env::var(name)
        .ok()
        .and_then(|value| Language::parse(&value))
}

fn normalize_locale(raw: &str) -> Option<String> {
    let value = raw.trim();
    if value.is_empty() {
        return None;
    }

    let without_encoding = value.split('.').next().unwrap_or(value);
    let without_modifier = without_encoding
        .split('@')
        .next()
        .unwrap_or(without_encoding);
    let normalized = without_modifier
        .trim()
        .replace('_', "-")
        .to_ascii_lowercase();

    (!normalized.is_empty()).then_some(normalized)
}

/// 设置当前线程后续翻译使用的语言。
pub fn set_language(language: Language) {
    rust_i18n::set_locale(language.as_locale());
}

/// 返回当前全局语言；未知 locale 会回退到英文。
pub fn current_language() -> Language {
    Language::parse(&rust_i18n::locale()).unwrap_or(Language::DEFAULT)
}

/// 获取指定语言的简单翻译文本。
pub fn tr(language: Language, key: &str) -> String {
    t!(key, locale = language.as_locale()).to_string()
}

/// 获取当前语言的简单翻译文本。
pub fn tr_current(key: &str) -> String {
    tr(current_language(), key)
}

/// 获取带单个 `path` 变量的当前语言翻译文本。
pub fn tr_path(key: &str, path: impl Display) -> String {
    t!(
        key,
        locale = current_language().as_locale(),
        path = path.to_string()
    )
    .to_string()
}

/// 获取带 `source` 和 `target` 变量的当前语言翻译文本。
pub fn tr_source_target(key: &str, source: impl Display, target: impl Display) -> String {
    t!(
        key,
        locale = current_language().as_locale(),
        source = source.to_string(),
        target = target.to_string()
    )
    .to_string()
}

/// 获取带 `path`、`source` 和 `target` 变量的当前语言翻译文本。
pub fn tr_path_source_target(
    key: &str,
    path: impl Display,
    source: impl Display,
    target: impl Display,
) -> String {
    t!(
        key,
        locale = current_language().as_locale(),
        path = path.to_string(),
        source = source.to_string(),
        target = target.to_string()
    )
    .to_string()
}

/// 获取带 `value` 变量的当前语言翻译文本。
pub fn tr_value(key: &str, value: impl Display) -> String {
    t!(
        key,
        locale = current_language().as_locale(),
        value = value.to_string()
    )
    .to_string()
}

/// 获取带错误数量和首个错误的当前语言翻译文本。
pub fn tr_many_errors(count: usize, first: &str) -> String {
    t!(
        "error.many",
        locale = current_language().as_locale(),
        count = count,
        first = first
    )
    .to_string()
}

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

    #[test]
    fn parses_common_linux_locale_names() {
        assert_eq!(Language::parse("zh_CN.UTF-8"), Some(Language::ZhCn));
        assert_eq!(Language::parse("zh-CN.UTF-8"), Some(Language::ZhCn));
        assert_eq!(Language::parse("zh_Hans_CN.UTF-8"), Some(Language::ZhCn));
        assert_eq!(Language::parse("en_US.UTF-8"), Some(Language::En));
        assert_eq!(Language::parse("C.UTF-8"), Some(Language::En));
    }

    #[test]
    fn parses_language_priority_list() {
        assert_eq!(Language::parse("fr_FR:zh_CN:en_US"), Some(Language::ZhCn));
        assert_eq!(Language::parse("fr_FR:en_US"), Some(Language::En));
    }
}