extern crate serde;
extern crate serde_yaml;

use std::fs::{File};
use std::path::Path;
use std::io::prelude::*;
use std::process::exit;
use std::env;

use self::serde::{Deserialize};

mod config {}

// TODO: built-in validator.
// For now, ensure any built Config has called validate()
#[derive(Debug, PartialEq, Deserialize)]
pub struct Config {
    pub words: Vec<String>,
    pub choose: usize,
    pub rows: Option<usize>,
    pub cols: Option<usize>
}

pub fn default_config_file() -> String {
    let config_folders = [
        env::var("XDG_CONFIG_HOME"),
        env::var("HOME").and_then(|s| Ok(String::from(Path::new(&s).join(".config").to_str().unwrap()))),
        Ok(String::from("./"))
    ];

    for f in config_folders.iter() {
        match f {
            Err(_) => continue,
            Ok(dir) => {
                let config_file_location = Path::new(dir).join("fallout-terminal.yaml");
                if Path::is_file(&config_file_location) {
                    return config_file_location.into_os_string().into_string().unwrap()
                }
            }
        }
    }

    String::from("")
}

pub fn load_config_file(config_file_path: String) -> Config {
    let mut config_file = match File::open(config_file_path.as_str()) {
        Ok(config_file) => config_file,
        Err(e) => {
            println!("Could not open {}: {}", config_file_path, e);
            exit(1);
        }
    };

    let mut config_str = String::new();
    let config: Config;
    match config_file.read_to_string(&mut config_str) {
        Ok(_) => {
            config = match serde_yaml::from_str(&config_str) {
                Ok(conf) => conf,
                Err(e) => {
                    println!("Could not parse YAML in {}: {}", config_file_path, e);
                    exit(1);
                }
            };
        }
        Err(e) => {
            println!("Could not read {}: {}", config_file_path, e);
            exit(1);
        }
    };

    validate(&config);
    config

}


fn validate(config: &Config) {
    if config.words.is_empty() {
        panic!("Config file validation error: word list must not be empty");
    }

    let first_len = config.words[0].len();
    for s in &config.words[1..] {
        if s.len() != first_len {
            panic!("Config file validation error: All words must be the same length [len({}) != len({})]", config.words[0], s);
        }
    }

    if config.choose > config.words.len() {
        panic!("'choose' value is greater than the number of available words.");
    }
}