use anyhow::anyhow;
use std::{fs::File, io::Read, path::PathBuf, time::Duration};
use toml::Value;

#[derive(Debug, Clone, Copy)]
pub enum DialogBackend {
    Gtk3,
}

impl DialogBackend {
    pub fn binary_name(&self) -> &str {
        match self {
            Self::Gtk3 => "bscreensaver-dialog-gtk3",
        }
    }
}

impl TryFrom<&str> for DialogBackend {
    type Error = anyhow::Error;
    fn try_from(value: &str) -> Result<Self, Self::Error> {
        match value {
            "gtk3" => Ok(Self::Gtk3),
            other => Err(anyhow!("'{}' is not a valid dialog backend (valid: 'gtk3')", other)),
        }
    }
}

#[derive(Debug, Clone)]
pub struct Configuration {
    pub lock_timeout: Duration,
    pub blank_before_locking: Duration,
    pub dialog_backend: DialogBackend,
    pub new_login_command: Option<String>,
}

impl Configuration {
    pub fn load() -> anyhow::Result<Configuration> {
        use humantime::parse_duration;

        let config_tomls = xdg::BaseDirectories::new()?
            .find_config_files("bscreensaver/bscreensaver.toml")
            .map(|config_path| parse_config_toml(&config_path))
            .collect::<Result<Vec<Value>, _>>()?;

        let mut config = Configuration::default();

        for config_toml in config_tomls {
            config.lock_timeout = match config_toml.get("lock-timeout") {
                None => config.lock_timeout,
                Some(val) => parse_duration(val.as_str().ok_or(anyhow!("'lock-timeout' must be a duration string like '10m' or '90s'"))?)?,
            };
            config.blank_before_locking = match config_toml.get("blank-before-locking") {
                None => config.blank_before_locking,
                Some(val) => parse_duration(val.as_str().ok_or(anyhow!("'blank-before-locking' must be a duration string like '10m' or '90s'"))?)?,
            };
            config.dialog_backend = match config_toml.get("dialog-backend") {
                None => config.dialog_backend,
                Some(val) => DialogBackend::try_from(val.as_str().ok_or(anyhow!("'dialog-backend' must be a string"))?)?,
            };
            config.new_login_command = match config_toml.get("new-login-command") {
                None => config.new_login_command,
                Some(val) => val.as_str().map(|s| s.to_string()),
            };
        }

        if config.blank_before_locking >= config.lock_timeout {
            Err(anyhow!("'blank-before-locking' cannot be greater than 'lock-timeout'"))
        } else {
            Ok(config)
        }
    }
}

fn parse_config_toml(config_path: &PathBuf) -> anyhow::Result<Value> {
    let mut f = File::open(config_path)?;
    let mut config = String::new();
    f.read_to_string(&mut config)?;
    drop(f);

    let config_toml = config.parse::<Value>()?;
    Ok(config_toml)
}

impl Default for Configuration {
    fn default() -> Self {
        Self {
            lock_timeout:  Duration::from_secs(60 * 10),
            blank_before_locking: Duration::ZERO,
            dialog_backend: DialogBackend::Gtk3,
            new_login_command: None,
        }
    }
}