use config::{Config, ConfigError, Environment, File};
use serde::Deserialize;
use std::{env, fs, io::Error, net::IpAddr, sync::RwLock};

static CONFIG_FILE_DEFAULTS: &str = "config/defaults.hjson";
static CONFIG_FILE: &str = "config/config.hjson";

#[derive(Debug, Deserialize, Clone)]
pub struct Settings {
  pub setup: Option<Setup>,
  pub database: Database,
  pub hostname: String,
  pub bind: IpAddr,
  pub port: u16,
  pub jwt_secret: String,
  pub front_end_dir: String,
  pub rate_limit: RateLimitConfig,
  pub email: Option<EmailConfig>,
  pub federation: Federation,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Setup {
  pub admin_username: String,
  pub admin_password: String,
  pub admin_email: Option<String>,
  pub site_name: String,
}

#[derive(Debug, Deserialize, Clone)]
pub struct RateLimitConfig {
  pub message: i32,
  pub message_per_second: i32,
  pub post: i32,
  pub post_per_second: i32,
  pub register: i32,
  pub register_per_second: i32,
}

#[derive(Debug, Deserialize, Clone)]
pub struct EmailConfig {
  pub smtp_server: String,
  pub smtp_login: Option<String>,
  pub smtp_password: Option<String>,
  pub smtp_from_address: String,
  pub use_tls: bool,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Database {
  pub user: String,
  pub password: String,
  pub host: String,
  pub port: i32,
  pub database: String,
  pub pool_size: u32,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Federation {
  pub enabled: bool,
  pub tls_enabled: bool,
  pub allowed_instances: String,
}

lazy_static! {
  static ref SETTINGS: RwLock<Settings> = RwLock::new(match Settings::init() {
    Ok(c) => c,
    Err(e) => panic!("{}", e),
  });
}

impl Settings {
  /// Reads config from the files and environment.
  /// First, defaults are loaded from CONFIG_FILE_DEFAULTS, then these values can be overwritten
  /// from CONFIG_FILE (optional). Finally, values from the environment (with prefix LEMMY) are
  /// added to the config.
  ///
  /// Note: The env var `LEMMY_DATABASE_URL` is parsed in
  /// `server/lemmy_db/src/lib.rs::get_database_url_from_env()`
  fn init() -> Result<Self, ConfigError> {
    let mut s = Config::new();

    s.merge(File::with_name(&Self::get_config_defaults_location()))?;

    s.merge(File::with_name(CONFIG_FILE).required(false))?;

    // Add in settings from the environment (with a prefix of LEMMY)
    // Eg.. `LEMMY_DEBUG=1 ./target/app` would set the `debug` key
    // Note: we need to use double underscore here, because otherwise variables containing
    //       underscore cant be set from environmnet.
    // https://github.com/mehcode/config-rs/issues/73
    s.merge(Environment::with_prefix("LEMMY").separator("__"))?;

    s.try_into()
  }

  /// Returns the config as a struct.
  pub fn get() -> Self {
    SETTINGS.read().unwrap().to_owned()
  }

  pub fn get_database_url(&self) -> String {
    format!(
      "postgres://{}:{}@{}:{}/{}",
      self.database.user,
      self.database.password,
      self.database.host,
      self.database.port,
      self.database.database
    )
  }

  pub fn api_endpoint(&self) -> String {
    format!("{}/api/v1", self.hostname)
  }

  pub fn get_config_defaults_location() -> String {
    env::var("LEMMY_CONFIG_LOCATION").unwrap_or_else(|_| CONFIG_FILE_DEFAULTS.to_string())
  }

  pub fn read_config_file() -> Result<String, Error> {
    fs::read_to_string(CONFIG_FILE)
  }

  pub fn save_config_file(data: &str) -> Result<String, Error> {
    fs::write(CONFIG_FILE, data)?;

    // Reload the new settings
    // From https://stackoverflow.com/questions/29654927/how-do-i-assign-a-string-to-a-mutable-static-variable/47181804#47181804
    let mut new_settings = SETTINGS.write().unwrap();
    *new_settings = match Settings::init() {
      Ok(c) => c,
      Err(e) => panic!("{}", e),
    };

    Self::read_config_file()
  }
}