use glob::glob;
use serde::Serialize;
use std::path::Path;
use toml;

pub fn generate(root: &Path) -> String {
    let mut bins = vec![];

    let root_glob = {
        let mut p = root.to_owned();
        p.push("**");
        p.push("*.rs");
        p
    };

    let mut exercise_paths: Vec<_> = glob(root_glob.to_str().unwrap())
        .unwrap()
        .collect::<Result<_, _>>()
        .expect("Error traversing root");

    exercise_paths.sort();

    for path in &exercise_paths {
        let name = path
            .file_stem()
            .expect("Malformed exercise path")
            .to_str()
            .expect("Invalid UTF8 in exercise path")
            .to_string();

        let target_path = path.strip_prefix(root).unwrap();

        bins.push(Bin {
            name,
            path: target_path.to_str().unwrap().to_string(),
        });
    }

    let manifest = Manifest {
        package: Package {
            name: "exercises",
            version: "0.1.0",
            authors: &["The Rustlings Maintainers"],
            edition: "2018",
            publish: false,
        },
        bin: bins,
    };

    format!(
        "# This Cargo.toml is AUTOGENERATED, you shouldn't need to edit it.\n\
         # The `rustling` commands do not rely on this manifest at all, its only purpose\n\
         # is to help editors analyze your code.\n\
         # To regenerate it, run `cargo generate-manifest`.\n\
         {}",
        toml::ser::to_string_pretty(&manifest).expect("Invalid toml")
    )
}

#[derive(Serialize)]
struct Manifest {
    package: Package,
    bin: Vec<Bin>,
}

#[derive(Serialize)]
struct Package {
    name: &'static str,
    version: &'static str,
    edition: &'static str,
    authors: &'static [&'static str],
    publish: bool,
}

#[derive(Serialize)]
struct Bin {
    name: String,
    path: String,
}