use sqlx::ConnectOptions;

#[derive(Debug, serde::Deserialize, Clone, Default)]
pub struct Settings {
    pub application: ApplicationSettings,
    pub database: Database,
    pub debug: bool,
    pub email: EmailSettings,
    pub frontend_url: String,
}

impl Settings {
    #[must_use]
    pub fn web_address(&self) -> String {
        if self.debug {
            format!(
                "{}:{}",
                self.application.base_url.clone(),
                self.application.port
            )
        } else {
            self.application.base_url.clone()
        }
    }

    /// Multipurpose function that helps detect the current
    /// environment the application is running in using the
    /// `APP_ENVIRONMENT` environment variable.
    ///
    /// ```text
    /// APP_ENVIRONMENT = development | dev | production | prod
    /// ```
    ///
    /// After detection, it loads the appropriate `.yaml` file. It
    /// then loads the environment variables that overrides whatever
    /// is set in the `.yaml` files. For this to work, the environment
    /// variable MUST be in uppercase and start with `APP`, a `_`
    /// separator, then the category of settings, followed by a `__`
    /// separator, and finally the variable itself. For instance,
    /// `APP__APPLICATION_PORT=3001` for `port` to be set as `3001`.
    ///
    /// # Errors
    ///
    /// Function may return an error if it fails to parse its config
    /// files.
    ///
    /// # Panics
    ///
    /// Panics if the program fails to detect the directory it is
    /// running in. Can also panic if it fails to parse the
    /// environment variable `APP_ENVIRONMENT` and it fails to fall
    /// back to its default value.
    pub fn new() -> Result<Self, config::ConfigError> {
        let base_path = std::env::current_dir().expect("Failed to determine the current directory");
        let settings_directory = base_path.join("settings");
        let environment: Environment = std::env::var("APP_ENVIRONMENT")
            .unwrap_or_else(|_| "development".into())
            .try_into()
            .expect("Failed to parse APP_ENVIRONMENT");
        let environment_filename = format!("{environment}.yaml");
        let settings = config::Config::builder()
            .add_source(config::File::from(settings_directory.join("base.yaml")))
            .add_source(config::File::from(
                settings_directory.join(environment_filename),
            ))
            .add_source(
                config::Environment::with_prefix("APP")
                    .prefix_separator("_")
                    .separator("__"),
            )
            .build()?;
        settings.try_deserialize::<Self>()
    }
}

#[derive(Debug, serde::Deserialize, Clone, Default)]
pub struct ApplicationSettings {
    pub name: String,
    pub version: String,
    pub port: u16,
    pub host: String,
    pub base_url: String,
    pub protocol: String,
}

#[derive(Debug, serde::Deserialize, Clone, Default)]
pub struct Database {
    pub host: String,
    pub port: u16,
    pub name: String,
    pub user: String,
    pub password: String,
    pub require_ssl: bool,
}

impl Database {
    #[must_use]
    pub fn get_connect_options(&self) -> sqlx::postgres::PgConnectOptions {
        let ssl_mode = if self.require_ssl {
            sqlx::postgres::PgSslMode::Require
        } else {
            sqlx::postgres::PgSslMode::Prefer
        };
        sqlx::postgres::PgConnectOptions::new()
            .host(&self.host)
            .username(&self.user)
            .password(&self.password)
            .port(self.port)
            .ssl_mode(ssl_mode)
            .database(&self.name)
            .log_statements(tracing::log::LevelFilter::Trace)
    }
}

#[derive(Debug, PartialEq, Eq)]
pub enum Environment {
    Development,
    Production,
}

impl Default for Environment {
    fn default() -> Self {
        Self::Development
    }
}

impl std::fmt::Display for Environment {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let self_str = match self {
            Self::Development => "development",
            Self::Production => "production",
        };
        write!(f, "{self_str}")
    }
}

impl TryFrom<String> for Environment {
    type Error = String;

    fn try_from(value: String) -> Result<Self, Self::Error> {
        match value.to_lowercase().as_str() {
            "development" | "dev" => Ok(Self::Development),
            "production" | "prod" => Ok(Self::Production),
            other => Err(format!(
                "{other} is not a supported environment. Use either `development` or `production`"
            )),
        }
    }
}

impl TryFrom<&str> for Environment {
    type Error = String;

    fn try_from(value: &str) -> Result<Self, Self::Error> {
        Self::try_from(value.to_string())
    }
}

#[derive(serde::Deserialize, Clone, Debug, Default)]
pub struct EmailSettings {
    pub host: String,
    pub user: String,
    pub password: String,
    pub from: String,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn default_environment_works() {
        let default_environment = Environment::default();
        assert_eq!(Environment::Development, default_environment);
    }

    #[test]
    fn display_environment_works() {
        let expected_prod = "production".to_string();
        let expected_dev = "development".to_string();
        let prod = Environment::Production.to_string();
        let dev = Environment::Development.to_string();
        assert_eq!(expected_prod, prod);
        assert_eq!(expected_dev, dev);
    }

    #[test]
    fn try_from_works() {
        [
            "DEVELOPMENT",
            "DEVEloPmENT",
            "Development",
            "DEV",
            "Dev",
            "dev",
        ]
        .iter()
        .map(|v| (*v).to_string())
        .for_each(|v| {
            let environment = Environment::try_from(v);
            assert!(environment.is_ok());
            assert_eq!(Environment::Development, environment.unwrap());
        });
        [
            "PRODUCTION",
            "Production",
            "PRODuction",
            "production",
            "PROD",
            "Prod",
            "prod",
        ]
        .iter()
        .map(|v| (*v).to_string())
        .for_each(|v| {
            let environment = Environment::try_from(v);
            assert!(environment.is_ok());
            assert_eq!(Environment::Production, environment.unwrap());
        });
        let environment = Environment::try_from("invalid");
        assert!(environment.is_err());
        assert_eq!(
            "invalid is not a supported environment. Use either `development` or `production`"
                .to_string(),
            environment.err().unwrap()
        );
    }

    #[test]
    fn web_address_works() {
        let mut settings = Settings {
            debug: false,
            application: ApplicationSettings {
                base_url: "127.0.0.1".to_string(),
                port: 3000,
                ..Default::default()
            },
            ..Default::default()
        };
        let expected_no_debug = "127.0.0.1".to_string();
        let expected_debug = "127.0.0.1:3000".to_string();
        assert_eq!(expected_no_debug, settings.web_address());
        settings.debug = true;
        assert_eq!(expected_debug, settings.web_address());
    }
}