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//! Basic config API
//! 
//! Contains a special trait that allows a type to have an associated config file

use serde::{Deserialize, Serialize};
use std::{
    fs,
    io::Result as IoResult
};
use ron::ser::PrettyConfig;

/// The type of config file we are using\
#[derive(Clone, Copy)]
pub enum ConfigType {
    Toml,
    Ron
}

//TODO: use PathBuf instead of String for file paths
//TODO: could I have this trait defined by a macro?
/// The `Config` trait allows a type to have an associated config file
/// 
/// Requires the `Default`, `Serialize`, and `Deserialize` traits (can be derived) to be implemented
pub trait Config: Serialize + Default + for <'de> Deserialize<'de> {
    /// This constant must be set to the file name of the config file
    const FILE_NAME: &'static str;

    /// This constant is the type of config
    /// 
    /// Defaults to TOML
    const TYPE: ConfigType = ConfigType::Toml;

    /// Returns the save directory of the config file.
    /// 
    /// This method must be defined
    fn get_save_dir() -> String;

    /// Returns the full path of the config file
    fn get_full_path() -> String { format!("{}/{}", Self::get_save_dir(), Self::FILE_NAME) }

    /// Load from the config file
    ///
    /// Returns the defaults if the file does not exist or is corrupted
    ///
    /// Panics if the config directory cannot be created
    #[track_caller]
    fn load() -> Self {
        let mut config = Self::default();
        let file_str = match fs::read_to_string(Self::get_full_path()) {
            Ok(file) => file,
            Err(_) => {
                config.save().expect("Unable to load config!");
                return config;
            }
        };

        match Self::TYPE {
            ConfigType::Toml => {
                match toml::from_str(&file_str) {
                    Ok(t) => config = t,
                    Err(_) => return Self::default(),
                }
            }

            ConfigType::Ron => {
                match ron::from_str(&file_str) {
                    Ok(r) => config = r,
                    Err(_) => return Self::default()
                }
            }
        }

        config
    }

    /// Save to the config file
    ///
    /// It is recommended to call this in every method that has &mut self as an argument!
    #[track_caller]
    fn save(&self) -> IoResult<()> {
        let save_str = match Self::TYPE {
            ConfigType::Toml => toml::to_string_pretty(&self).unwrap(),
            ConfigType::Ron => {
                let cfg = PrettyConfig::default();
                ron::ser::to_string_pretty(&self, cfg).unwrap()
            }
        };

        fs::create_dir_all(Self::get_save_dir())?;
        fs::write(Self::get_full_path(), save_str)
    }
}