/*
 * Various types to support iteration.
 */

use super::super::pyobject::{
    AttributeProtocol, PyContext, PyFuncArgs, PyObjectKind, PyObjectRef, PyResult, TypeProtocol,
};
use super::super::vm::VirtualMachine;
use super::objbool;
// use super::objstr;
use super::objtype; // Required for arg_check! to use isinstance

/*
 * This helper function is called at multiple places. First, it is called
 * in the vm when a for loop is entered. Next, it is used when the builtin
 * function 'iter' is called.
 */
pub fn get_iter(vm: &mut VirtualMachine, iter_target: &PyObjectRef) -> PyResult {
    vm.call_method(iter_target, "__iter__", vec![])
    // let type_str = objstr::get_value(&vm.to_str(iter_target.typ()).unwrap());
    // let type_error = vm.new_type_error(format!("Cannot iterate over {}", type_str));
    // return Err(type_error);
}

/*
 * Helper function to retrieve the next object (or none) from an iterator.
 */
pub fn get_next_object(
    vm: &mut VirtualMachine,
    iter_obj: &PyObjectRef,
) -> Result<Option<PyObjectRef>, PyObjectRef> {
    let next_obj: PyResult = vm.call_method(iter_obj, "__next__", vec![]);

    match next_obj {
        Ok(value) => Ok(Some(value)),
        Err(next_error) => {
            // Check if we have stopiteration, or something else:
            if objtype::isinstance(&next_error, &vm.ctx.exceptions.stop_iteration) {
                Ok(None)
            } else {
                Err(next_error)
            }
        }
    }
}

/* Retrieve all elements from an iterator */
pub fn get_all(
    vm: &mut VirtualMachine,
    iter_obj: &PyObjectRef,
) -> Result<Vec<PyObjectRef>, PyObjectRef> {
    let mut elements = vec![];
    loop {
        let element = get_next_object(vm, iter_obj)?;
        match element {
            Some(v) => elements.push(v),
            None => break,
        }
    }
    Ok(elements)
}

// Sequence iterator:
fn iter_new(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
    arg_check!(vm, args, required = [(iter_target, None)]);

    get_iter(vm, iter_target)
}

fn iter_iter(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
    arg_check!(vm, args, required = [(iter, Some(vm.ctx.iter_type()))]);
    // Return self:
    Ok(iter.clone())
}

fn iter_contains(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
    arg_check!(
        vm,
        args,
        required = [(iter, Some(vm.ctx.iter_type())), (needle, None)]
    );
    loop {
        match vm.call_method(&iter, "__next__", vec![]) {
            Ok(element) => match vm.call_method(needle, "__eq__", vec![element.clone()]) {
                Ok(value) => {
                    if objbool::get_value(&value) {
                        return Ok(vm.new_bool(true));
                    } else {
                        continue;
                    }
                }
                Err(_) => return Err(vm.new_type_error("".to_string())),
            },
            Err(_) => return Ok(vm.new_bool(false)),
        }
    }
}

fn iter_next(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
    arg_check!(vm, args, required = [(iter, Some(vm.ctx.iter_type()))]);

    if let PyObjectKind::Iterator {
        ref mut position,
        iterated_obj: ref iterated_obj_ref,
    } = iter.borrow_mut().kind
    {
        let iterated_obj = &*iterated_obj_ref.borrow_mut();
        match iterated_obj.kind {
            PyObjectKind::Sequence { ref elements } => {
                if *position < elements.len() {
                    let obj_ref = elements[*position].clone();
                    *position += 1;
                    Ok(obj_ref)
                } else {
                    let stop_iteration_type = vm.ctx.exceptions.stop_iteration.clone();
                    let stop_iteration =
                        vm.new_exception(stop_iteration_type, "End of iterator".to_string());
                    Err(stop_iteration)
                }
            }
            _ => {
                panic!("NOT IMPL");
            }
        }
    } else {
        panic!("NOT IMPL");
    }
}

pub fn init(context: &PyContext) {
    let ref iter_type = context.iter_type;
    iter_type.set_attr("__contains__", context.new_rustfunc(iter_contains));
    iter_type.set_attr("__iter__", context.new_rustfunc(iter_iter));
    iter_type.set_attr("__new__", context.new_rustfunc(iter_new));
    iter_type.set_attr("__next__", context.new_rustfunc(iter_next));
}