use std::env;
use std::path::PathBuf;

pub struct Configuration {
    // Default Base Directories, default to XDG dirs but can be
    // configured by users.
    pub config_directory: PathBuf,
    pub data_directory: PathBuf,
    pub output_directory: PathBuf,

    pub max_posts: u8,

    // Derived directories: Config
    pub remote_config: PathBuf,

    // Derived directories: Data
    pub posts_directory: PathBuf,
    pub archive_directory: PathBuf,
    pub static_directory: PathBuf,
    pub templates_directory: PathBuf,

    // Derived directories: Output
    pub blog_output_directory: PathBuf,
    pub archive_output_directory: PathBuf,
}

impl Configuration {
    pub fn new() -> Self {
        let config_directory = Configuration::directory(
            "BLOG_CONFIG_DIRECTORY",
            "XDG_CONFIG_HOME",
            ".config",
            "blog",
        );
        let data_directory = Configuration::directory(
            "BLOG_DATA_DIRECTORY",
            "XDG_DATA_HOME",
            ".local/share",
            "blog",
        );
        let output_directory =
            Configuration::directory("BLOG_OUTPUT_DIRECTORY", "XDG_CACHE_HOME", ".cache", "blog");

        let max_posts: u8 = env::var("BLOG_MAX_POSTS")
            .ok()
            .and_then(|v| v.parse().ok())
            .unwrap_or(3);

        let remote_config = config_directory.join("blogremote");

        let posts_directory = data_directory.join("posts");
        let archive_directory = data_directory.join("archive");
        let static_directory = data_directory.join("static");
        let templates_directory = data_directory.join("templates");

        let blog_output_directory = output_directory.join("blog");
        let archive_output_directory = output_directory.join("archive");

        Configuration {
            config_directory,
            data_directory,
            output_directory,
            max_posts,
            remote_config,
            posts_directory,
            archive_directory,
            static_directory,
            templates_directory,
            blog_output_directory,
            archive_output_directory,
        }
    }

    fn directory(
        user_override: &str,
        default_value: &str,
        home_fallback: &str,
        path: &str,
    ) -> PathBuf {
        match env::var(user_override) {
            Ok(directory) => PathBuf::from(directory),
            Err(_) => match env::var(default_value) {
                Ok(directory) => PathBuf::from(directory),
                Err(_) => match env::var("HOME") {
                    Ok(directory) => PathBuf::from(directory).join(home_fallback),
                    Err(_) => panic!(
                        "Could not find required directory, {} or {} should be set and readable.",
                        user_override, default_value
                    ),
                },
            },
        }
        .join(path)
    }
}