fn main() {
    // Initialize repository
    let repo = git2::Repository::open(std::env::var("REPOSITORY").unwrap()).unwrap();
    let mut revwalk = repo.revwalk().unwrap();
    revwalk
        .set_sorting(git2::Sort::NONE | git2::Sort::TIME)
        .unwrap();
    revwalk.push_head().unwrap();

    // Parse commits
    let mut fixes = Vec::new();
    let mut features = Vec::new();
    for commit in revwalk
        .filter_map(|id| id.ok())
        .filter_map(|id| repo.find_commit(id).ok())
    {
        let message = commit.message().unwrap();
        if message.starts_with("feat") {
            features.push(commit);
        } else if message.starts_with("fix") {
            fixes.push(commit);
        }
    }

    // Generate changelog
    let generate = |commits: Vec<git2::Commit>| -> Vec<String> {
        commits
            .iter()
            .map(|commit| {
                let id = commit.id().to_string();
                format!(
                    "* {} ([{}]({}))",
                    commit.message().unwrap().trim(),
                    &id[0..7],
                    &id[0..7],
                )
            })
            .collect()
    };
    let mut result = Vec::new();
    result.push(String::from("## 0.1.0"));
    result.push(String::from("\n### Bug Fixes\n"));
    result.extend(generate(fixes));
    result.push(String::from("\n### Features\n"));
    result.extend(generate(features));
    result.push(String::from("\n"));

    // Print to file or stdout
    use std::io::Write;
    write!(std::io::stdout(), "{}", result.join("\n")).unwrap();
}