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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
#[derive(Debug)]
enum Language {
    Rust,
    Java,
    Perl,
}

#[derive(Clone, Debug)]
struct Dependency {
    name: String,
    version_expression: String,
}

/// 软件包的表示。
#[derive(Debug)]
struct Package {
    name: String,
    version: String,
    authors: Vec<String>,
    dependencies: Vec<Dependency>,
    language: Option<Language>,
}

impl Package {
    /// 将该包表示为依赖项，供构建其他包时使用。
    fn to_dependency(&self) -> Dependency {
        Dependency {
            name: self.name.clone(),
            version_expression: self.version.clone(),
        }
    }
}

/// Package 的构建器。使用 `build()` 创建 `Package` 本身。
struct PackageBuilder(Package);

impl PackageBuilder {
    fn new(name: impl Into<String>) -> Self {
        Self(Package {
            name: name.into(),
            version: "0.1".into(),
            authors: Vec::new(),
            dependencies: Vec::new(),
            language: None,
        })
    }

    /// 设置包版本。
    fn version(mut self, version: impl Into<String>) -> Self {
        self.0.version = version.into();
        self
    }

    /// 设置包作者。
    fn authors(mut self, authors: Vec<String>) -> Self {
        self.0.authors = authors;
        self
    }

    /// 追加一个依赖项。
    fn dependency(mut self, dependency: Dependency) -> Self {
        self.0.dependencies.push(dependency);
        self
    }

    /// 设置语言。若未设置，language 默认为 None。
    fn language(mut self, language: Language) -> Self {
        self.0.language = Some(language);
        self
    }

    fn build(self) -> Package {
        self.0
    }
}

fn main() {
    let base64 = PackageBuilder::new("base64").version("0.13").build();
    dbg!(&base64);
    let log =
        PackageBuilder::new("log").version("0.4").language(Language::Rust).build();
    dbg!(&log);
    let serde = PackageBuilder::new("serde")
        .authors(vec!["djmitche".into()])
        .version(String::from("4.0"))
        .dependency(base64.to_dependency())
        .dependency(log.to_dependency())
        .build();
    dbg!(serde);
}