use crate::object::{BuiltinExit, Int, Value};
use crate::vm::{error::RuntimeError, machine::MachineBuilder};

impl MachineBuilder {
    /// Registers all builtins for calling on the machine.
    pub(super) fn register_builtins(&mut self) {
        self.scope_stack.push_scope();

        //
        // panic
        //
        self.register_builtin_fun("panic", |machine, _| {
            println!("!!! panic");
            println!("!!! top of stack");
            for (i, value) in machine.stack().iter().enumerate().rev() {
                println!("!!!   {}. {:?}", i, value);
            }
            println!("!!! bottom of stack");
            panic!();
        });

        //
        // if
        //
        self.register_builtin_fun("if", |machine, _| {
            let if_false = machine.stack_pop()?;
            let if_true = machine.stack_pop()?;
            let condition = machine.stack_pop()?;
            let value = if condition.is_truthy() {
                if_true
            } else {
                if_false
            };

            if let Value::Quote(quote) = value {
                Ok(BuiltinExit::Call(quote))
            } else {
                return Err(RuntimeError::CannotCall(
                    "if statement requires quote value".to_string(),
                )
                .into());
            }
        });

        //
        // print
        //
        self.register_builtin_fun("print", |machine, _| {
            let value = machine.stack_pop()?;
            print!("{}", value);
            Ok(BuiltinExit::Return)
        });

        //
        // println
        //
        self.register_builtin_fun("println", |machine, _| {
            let value = machine.stack_pop()?;
            println!("{}", value);
            Ok(BuiltinExit::Return)
        });

        //
        // ==
        //
        self.register_builtin_fun("==", |machine, _| {
            let rhs = machine.stack_pop()?;
            let lhs = machine.stack_pop()?;
            machine.stack_push(Value::Int((lhs == rhs) as Int))?;
            Ok(BuiltinExit::Return)
        });

        //
        // ~=
        //
        self.register_builtin_fun("~=", |machine, _| {
            let rhs = machine.stack_pop()?;
            let lhs = machine.stack_pop()?;
            machine.stack_push(Value::Int((lhs != rhs) as Int))?;
            Ok(BuiltinExit::Return)
        });
    }
}