use std::error::Error;
use std::ffi::OsString;
use std::fs::File;
use std::io::BufReader;
use std::path::Path;
use std::process::exit;

use serde::{Deserialize, Serialize};
use serde_json::from_reader;

#[derive(Serialize, Deserialize, Debug)]
#[serde(deny_unknown_fields)]
pub struct Config {
    pub save_directory: Option<String>,
}

pub struct ConfigManager {
    config_path: OsString,
    pub config: Config,
}

fn read_config<P: AsRef<Path>>(path: P) -> Result<Config, Box<dyn Error>> {
    if path.as_ref().exists() {
        let file = File::open(path)?;
        let reader = BufReader::new(file);
        let result: Config = from_reader(reader)?;
        Ok(result)
    } else {
        Ok(Config {
            save_directory: Some(String::from("tmp")),
        })
    }
}

impl ConfigManager {
    pub fn new(config_path: &Path) -> ConfigManager {
        let mut config = ConfigManager {
            config_path: OsString::from(config_path.as_os_str()),
            config: Config {
                save_directory: None,
            },
        };
        config.load();
        config
    }

    fn load(&mut self) {
        match read_config(&self.config_path) {
            Err(e) => {
                println!("Failed to read config file {:#?}: {}", &self.config_path, e);
                exit(1);
            }
            Ok(config) => self.config = config,
        }
    }
}