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/// A trait to be implemented by all tedge sub-commands.
///
/// A command encapsulates all the required parameters and provides an `execute()` method
/// to trigger the execution, plus a `description` of what is done by that command.
///
/// ```
/// struct SayHello {
/// name: String,
/// };
///
/// impl Command for SayHello {
/// fn description(&self) -> String {
/// format!("say hello to '{}'", name),
/// }
///
/// fn execute(&self) -> anyhow::Result<()> {
/// println!("Hello {}!", name};
/// Ok(())
/// }
/// }
/// ```
///
/// If a command needs some context, say the tedge configuration,
/// this context can be provided to the command struct.
///
/// ```
/// struct GetConfigKey {
/// config: TEdgeConfig,
/// key: String,
/// };
///
/// impl Command for GetConfigKey {
/// fn description(&self) -> String {
/// format!("get the value of the configuration key '{}'", self.key),
/// }
///
/// fn execute(&self) -> anyhow::Result<()> {
/// match self.config.get_config_value(self.key)? {
/// Some(value) => println!("{}", value),
/// None => eprintln!("The configuration key `{}` is not set", self.key),
/// }
/// Ok(())
/// }
/// }
/// ```
///
/// No specific support is provided to a command that needs to update the configuration.
/// The simplest is to acquire a mutable config using `TEdgeConfig::from_default_config()`.
///
/// ```
/// struct SetConfigKey {
/// key: String,
/// value: String,
/// };
///
/// impl Command for SetConfigKey {
/// fn description(&self) -> String {
/// format!("set the value of the configuration key '{}' to '{}'", self.key, self.value),
/// }
///
/// fn execute(&self) -> anyhow::Result<()> {
/// let mut config = TEdgeConfig::from_default_config()?;
/// config.set_config_value(self.key, self.value)?;
/// let _ = config.write_to_default_config()?;
/// Ok(())
/// }
/// }
/// ```
pub trait Command {
/// Display that command to the user, telling what will be done.
///
/// This description is displayed to the end user in case of an error, to give the context of that error.
fn description(&self) -> String;
/// Execute this command.
///
/// The errors returned by this method must be concrete `anyhow::Error` values.
/// The simplest way to implement a specific `anyhow::Error` type is to derive the `thiserror::Error`.
/// Doing so, the command specific error type implements `Into<anyhow::Error>`
/// and such errors can then be returned with no explicit conversion from the `run()` method.
///
/// ```
/// #[derive(thiserror::Error, Debug)]
/// pub enum ConfigError {
/// #[error("Not a Thin Edge property: {key:?}")]
/// UnknownKey{key: String},
/// }
/// ```
fn execute(&self) -> anyhow::Result<()>;
/// Helper method to be used in the `BuildCommand` trait.
///
/// The `BuildCommand::build_command()` method has to return a box around a new command.
///
/// ```
/// fn build_command(self, config: TEdgeConfig) -> Result<Box<dyn Command>, ConfigError> {
/// let cmd = GetConfigKey { config, key };
/// Ok(cmd.into_boxed())
/// }
/// ```
fn into_boxed(self) -> Box<dyn Command>
where
Self: Sized + 'static,
{
Box::new(self)
}
}
/// A trait implemented by the tedge subcommands to build the actual command
/// using a combination of the parameters provided on the command line
/// and those from the configuration.
///
/// In practice, an implementation will also derives the `Structopt` trait.
///
/// ```
/// #[derive(clap::Parser, Debug)]
/// enum ConfigCmd {
/// /// Add new value (overwrite the value if the key exists).
/// Set { key: String, value: String },
///
/// /// Get value.
/// Get { key: String },
/// }
///
/// impl BuildCommand for ConfigCmd {
/// fn build_command(self, context: BuildContext) -> Result<Box<dyn Command>, ConfigError> {
/// let cmd = match self {
/// ConfigCmd::Set { key, value } => SetConfigKey {
/// config: context.config,
/// key,
/// value,
/// },
/// ConfigCmd::Get { key } => GetConfigKey {
/// config: context.config,
/// key,
/// },
/// }
/// Ok(cmd.into_boxed())
/// }
/// }
/// ```
pub trait BuildCommand {
fn build_command(self, context: BuildContext) -> Result<Box<dyn Command>, crate::ConfigError>;
}
/// The context for `BuildCommand`
///
pub struct BuildContext {
pub config_repository: tedge_config::TEdgeConfigRepository,
pub config_location: tedge_config::TEdgeConfigLocation,
}
|
