//! Repl commands
use super::*;
use std::str::FromStr;

use super::env::*;

#[derive(Debug)]
pub struct Context<'a>
{
    /// Environment containing variable name mappings.
    env: &'a mut Lexenv,
}

/// Trait for commands.
///
/// # Defining commands
/// A command object should be created once only, and then referenced and executed using `params` and through mutating `cx`.
pub trait Command: fmt::Debug
{
    fn execute(&self, cx: &mut Context<'_>, params: Vec<Value>) -> eyre::Result<()>;
}

/// Command structurally parsed.
///
/// Can be converted into `Command` with the `TryInto` trait.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct IR
{
    op: String,
    params: Vec<Value>,
}

impl FromStr for IR
{
    type Err = CommandParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
	todo!()
    }
}

/// Error when parsing a command into `IR`.
#[derive(Debug)]
pub struct CommandParseError(String);

impl error::Error for CommandParseError{}

impl fmt::Display for CommandParseError
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f, "failed to parse command from {:?}", self.0)
    }
}