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use malachite_bigint::Sign;

use num_traits::ToPrimitive;

use crate::{

Py, VirtualMachine,

builtins::PyFloat,

object::{AsObject, PyObject, PyObjectRef, PyPayload, PyRef, PyResult},

};

/// Implemented by any type that can be created from a Python object.

///

/// Any type that implements `TryFromObject` is automatically `FromArgs`, and

/// so can be accepted as a argument to a built-in function.

pub trait TryFromObject: Sized {

/// Attempt to convert a Python object to a value of this type.

fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self>;

}

/// Rust-side only version of TryFromObject to reduce unnecessary Rc::clone

impl<T: for<'a> TryFromBorrowedObject<'a>> TryFromObject for T {

fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {

TryFromBorrowedObject::try_from_borrowed_object(vm, &obj)

}

impl PyObjectRef {

pub fn try_into_value<T>(self, vm: &VirtualMachine) -> PyResult<T>

where

T: TryFromObject,

{

T::try_from_object(vm, self)

}

impl PyObject {

pub fn try_to_value<'a, T>(&'a self, vm: &VirtualMachine) -> PyResult<T>

where

T: 'a + TryFromBorrowedObject<'a>,

{

T::try_from_borrowed_object(vm, self)

}

pub fn try_to_ref<'a, T>(&'a self, vm: &VirtualMachine) -> PyResult<&'a Py<T>>

where

T: 'a + PyPayload,

{

self.try_to_value::<&Py<T>>(vm)

}

pub fn try_value_with<T, F, R>(&self, f: F, vm: &VirtualMachine) -> PyResult<R>

where

T: PyPayload,

F: Fn(&T) -> PyResult<R>,

{

let class = T::class(&vm.ctx);

let py_ref = if self.fast_isinstance(class) {

self.downcast_ref()

.ok_or_else(|| vm.new_downcast_runtime_error(class, self))?

} else {

return Err(vm.new_downcast_type_error(class, self));

};

f(py_ref)

}

/// Lower-cost variation of [`TryFromObject`].

pub trait TryFromBorrowedObject<'a>: Sized

where

Self: 'a,

{

/// Attempt to convert a Python object to a value of this type.

fn try_from_borrowed_object(vm: &VirtualMachine, obj: &'a PyObject) -> PyResult<Self>;

}

impl<T> TryFromObject for PyRef<T>

where

T: PyPayload,

{

#[inline]

fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {

let class = T::class(&vm.ctx);

if obj.fast_isinstance(class) {

T::try_downcast_from(&obj, vm)?;

Ok(unsafe { obj.downcast_unchecked() })

} else {

Err(vm.new_downcast_type_error(class, &obj))

}

impl TryFromObject for PyObjectRef {

#[inline]

fn try_from_object(_vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {

Ok(obj)

}

impl<T: TryFromObject> TryFromObject for Option<T> {

fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {

if vm.is_none(&obj) {

Ok(None)

} else {

T::try_from_object(vm, obj).map(Some)

}

impl<'a, T: 'a + TryFromObject> TryFromBorrowedObject<'a> for Vec<T> {

fn try_from_borrowed_object(vm: &VirtualMachine, value: &'a PyObject) -> PyResult<Self> {

vm.extract_elements_with(value, |obj| T::try_from_object(vm, obj))

}

impl<'a, T: PyPayload> TryFromBorrowedObject<'a> for &'a Py<T> {

fn try_from_borrowed_object(vm: &VirtualMachine, obj: &'a PyObject) -> PyResult<Self> {

let class = T::class(&vm.ctx);

if obj.fast_isinstance(class) {

obj.downcast_ref()

.ok_or_else(|| vm.new_downcast_runtime_error(class, &obj))

} else {

Err(vm.new_downcast_type_error(class, &obj))

}

impl TryFromObject for core::time::Duration {

fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {

if let Some(float) = obj.downcast_ref::<PyFloat>() {

let f = float.to_f64();

if f.is_nan() {

return Err(vm.new_value_error("Invalid value NaN (not a number)"));

}

if f < 0.0 {

return Err(vm.new_value_error("negative duration"));

}

if !f.is_finite() || f > u64::MAX as f64 {

return Err(vm.new_overflow_error("timestamp too large to convert to C PyTime_t"));

}

// Convert float to Duration using floor rounding (_PyTime_ROUND_FLOOR)

let secs = f.trunc() as u64;

let frac = f.fract();

// Use floor to round down the nanoseconds

let nanos = (frac * 1_000_000_000.0).floor() as u32;

Ok(Self::new(secs, nanos))

} else if let Some(int) = obj.try_index_opt(vm) {

let int = int?;

let bigint = int.as_bigint();

if bigint.sign() == Sign::Minus {

return Err(vm.new_value_error("negative duration"));

}

let sec = bigint

.to_u64()

.ok_or_else(|| vm.new_value_error("value out of range"))?;

Ok(Self::from_secs(sec))

} else {

Err(vm.new_type_error(format!(

"expected an int or float for duration, got {}",

obj.class()

)))

}

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