//! Contains types for working with Python objects that own the underlying data.

use std::{ops::Deref, ptr::NonNull, sync::Arc};

use crate::{
    types::{
        any::PyAnyMethods, bytearray::PyByteArrayMethods, bytes::PyBytesMethods,
        string::PyStringMethods, PyByteArray, PyBytes, PyString,
    },
    Bound, DowncastError, FromPyObject, Py, PyAny, PyErr, PyResult,
};

/// A wrapper around `str` where the storage is owned by a Python `bytes` or `str` object.
///
/// This type gives access to the underlying data via a `Deref` implementation.
#[derive(Clone)]
pub struct PyBackedStr {
    #[allow(dead_code)] // only held so that the storage is not dropped
    storage: Py<PyAny>,
    data: NonNull<str>,
}

impl Deref for PyBackedStr {
    type Target = str;
    fn deref(&self) -> &str {
        // Safety: `data` is known to be immutable and owned by self
        unsafe { self.data.as_ref() }
    }
}

impl AsRef<str> for PyBackedStr {
    fn as_ref(&self) -> &str {
        self
    }
}

impl AsRef<[u8]> for PyBackedStr {
    fn as_ref(&self) -> &[u8] {
        self.as_bytes()
    }
}

// Safety: the underlying Python str (or bytes) is immutable and
// safe to share between threads
unsafe impl Send for PyBackedStr {}
unsafe impl Sync for PyBackedStr {}

impl std::fmt::Display for PyBackedStr {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.deref().fmt(f)
    }
}

impl_traits!(PyBackedStr, str);

impl TryFrom<Bound<'_, PyString>> for PyBackedStr {
    type Error = PyErr;
    fn try_from(py_string: Bound<'_, PyString>) -> Result<Self, Self::Error> {
        #[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
        {
            let s = py_string.to_str()?;
            let data = NonNull::from(s);
            Ok(Self {
                storage: py_string.as_any().to_owned().unbind(),
                data,
            })
        }
        #[cfg(not(any(Py_3_10, not(Py_LIMITED_API))))]
        {
            let bytes = py_string.encode_utf8()?;
            let s = unsafe { std::str::from_utf8_unchecked(bytes.as_bytes()) };
            let data = NonNull::from(s);
            Ok(Self {
                storage: bytes.into_any().unbind(),
                data,
            })
        }
    }
}

impl FromPyObject<'_> for PyBackedStr {
    fn extract_bound(obj: &Bound<'_, PyAny>) -> PyResult<Self> {
        let py_string = obj.downcast::<PyString>()?.to_owned();
        Self::try_from(py_string)
    }
}

/// A wrapper around `[u8]` where the storage is either owned by a Python `bytes` object, or a Rust `Box<[u8]>`.
///
/// This type gives access to the underlying data via a `Deref` implementation.
#[derive(Clone)]
pub struct PyBackedBytes {
    #[allow(dead_code)] // only held so that the storage is not dropped
    storage: PyBackedBytesStorage,
    data: NonNull<[u8]>,
}

#[allow(dead_code)]
#[derive(Clone)]
enum PyBackedBytesStorage {
    Python(Py<PyBytes>),
    Rust(Arc<[u8]>),
}

impl Deref for PyBackedBytes {
    type Target = [u8];
    fn deref(&self) -> &[u8] {
        // Safety: `data` is known to be immutable and owned by self
        unsafe { self.data.as_ref() }
    }
}

impl AsRef<[u8]> for PyBackedBytes {
    fn as_ref(&self) -> &[u8] {
        self
    }
}

// Safety: the underlying Python bytes or Rust bytes is immutable and
// safe to share between threads
unsafe impl Send for PyBackedBytes {}
unsafe impl Sync for PyBackedBytes {}

impl<const N: usize> PartialEq<[u8; N]> for PyBackedBytes {
    fn eq(&self, other: &[u8; N]) -> bool {
        self.deref() == other
    }
}

impl<const N: usize> PartialEq<PyBackedBytes> for [u8; N] {
    fn eq(&self, other: &PyBackedBytes) -> bool {
        self == other.deref()
    }
}

impl<const N: usize> PartialEq<&[u8; N]> for PyBackedBytes {
    fn eq(&self, other: &&[u8; N]) -> bool {
        self.deref() == *other
    }
}

impl<const N: usize> PartialEq<PyBackedBytes> for &[u8; N] {
    fn eq(&self, other: &PyBackedBytes) -> bool {
        self == &other.deref()
    }
}

impl_traits!(PyBackedBytes, [u8]);

impl From<Bound<'_, PyBytes>> for PyBackedBytes {
    fn from(py_bytes: Bound<'_, PyBytes>) -> Self {
        let b = py_bytes.as_bytes();
        let data = NonNull::from(b);
        Self {
            storage: PyBackedBytesStorage::Python(py_bytes.to_owned().unbind()),
            data,
        }
    }
}

impl From<Bound<'_, PyByteArray>> for PyBackedBytes {
    fn from(py_bytearray: Bound<'_, PyByteArray>) -> Self {
        let s = Arc::<[u8]>::from(py_bytearray.to_vec());
        let data = NonNull::from(s.as_ref());
        Self {
            storage: PyBackedBytesStorage::Rust(s),
            data,
        }
    }
}

impl FromPyObject<'_> for PyBackedBytes {
    fn extract_bound(obj: &Bound<'_, PyAny>) -> PyResult<Self> {
        if let Ok(bytes) = obj.downcast::<PyBytes>() {
            Ok(Self::from(bytes.to_owned()))
        } else if let Ok(bytearray) = obj.downcast::<PyByteArray>() {
            Ok(Self::from(bytearray.to_owned()))
        } else {
            Err(DowncastError::new(obj, "`bytes` or `bytearray`").into())
        }
    }
}

macro_rules! impl_traits {
    ($slf:ty, $equiv:ty) => {
        impl std::fmt::Debug for $slf {
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                self.deref().fmt(f)
            }
        }

        impl PartialEq for $slf {
            fn eq(&self, other: &Self) -> bool {
                self.deref() == other.deref()
            }
        }

        impl PartialEq<$equiv> for $slf {
            fn eq(&self, other: &$equiv) -> bool {
                self.deref() == other
            }
        }

        impl PartialEq<&$equiv> for $slf {
            fn eq(&self, other: &&$equiv) -> bool {
                self.deref() == *other
            }
        }

        impl PartialEq<$slf> for $equiv {
            fn eq(&self, other: &$slf) -> bool {
                self == other.deref()
            }
        }

        impl PartialEq<$slf> for &$equiv {
            fn eq(&self, other: &$slf) -> bool {
                self == &other.deref()
            }
        }

        impl Eq for $slf {}

        impl PartialOrd for $slf {
            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
                Some(self.cmp(other))
            }
        }

        impl PartialOrd<$equiv> for $slf {
            fn partial_cmp(&self, other: &$equiv) -> Option<std::cmp::Ordering> {
                self.deref().partial_cmp(other)
            }
        }

        impl PartialOrd<$slf> for $equiv {
            fn partial_cmp(&self, other: &$slf) -> Option<std::cmp::Ordering> {
                self.partial_cmp(other.deref())
            }
        }

        impl Ord for $slf {
            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
                self.deref().cmp(other.deref())
            }
        }

        impl std::hash::Hash for $slf {
            fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
                self.deref().hash(state)
            }
        }
    };
}
use impl_traits;

#[cfg(test)]
mod test {
    use super::*;
    use crate::Python;
    use std::collections::hash_map::DefaultHasher;
    use std::hash::{Hash, Hasher};

    #[test]
    fn py_backed_str_empty() {
        Python::with_gil(|py| {
            let s = PyString::new_bound(py, "");
            let py_backed_str = s.extract::<PyBackedStr>().unwrap();
            assert_eq!(&*py_backed_str, "");
        });
    }

    #[test]
    fn py_backed_str() {
        Python::with_gil(|py| {
            let s = PyString::new_bound(py, "hello");
            let py_backed_str = s.extract::<PyBackedStr>().unwrap();
            assert_eq!(&*py_backed_str, "hello");
        });
    }

    #[test]
    fn py_backed_str_try_from() {
        Python::with_gil(|py| {
            let s = PyString::new_bound(py, "hello");
            let py_backed_str = PyBackedStr::try_from(s).unwrap();
            assert_eq!(&*py_backed_str, "hello");
        });
    }

    #[test]
    fn py_backed_bytes_empty() {
        Python::with_gil(|py| {
            let b = PyBytes::new_bound(py, &[]);
            let py_backed_bytes = b.extract::<PyBackedBytes>().unwrap();
            assert_eq!(&*py_backed_bytes, &[]);
        });
    }

    #[test]
    fn py_backed_bytes() {
        Python::with_gil(|py| {
            let b = PyBytes::new_bound(py, b"abcde");
            let py_backed_bytes = b.extract::<PyBackedBytes>().unwrap();
            assert_eq!(&*py_backed_bytes, b"abcde");
        });
    }

    #[test]
    fn py_backed_bytes_from_bytes() {
        Python::with_gil(|py| {
            let b = PyBytes::new_bound(py, b"abcde");
            let py_backed_bytes = PyBackedBytes::from(b);
            assert_eq!(&*py_backed_bytes, b"abcde");
        });
    }

    #[test]
    fn py_backed_bytes_from_bytearray() {
        Python::with_gil(|py| {
            let b = PyByteArray::new_bound(py, b"abcde");
            let py_backed_bytes = PyBackedBytes::from(b);
            assert_eq!(&*py_backed_bytes, b"abcde");
        });
    }

    #[test]
    fn test_backed_types_send_sync() {
        fn is_send<T: Send>() {}
        fn is_sync<T: Sync>() {}

        is_send::<PyBackedStr>();
        is_sync::<PyBackedStr>();

        is_send::<PyBackedBytes>();
        is_sync::<PyBackedBytes>();
    }

    #[test]
    fn test_backed_str_clone() {
        Python::with_gil(|py| {
            let s1: PyBackedStr = PyString::new_bound(py, "hello").try_into().unwrap();
            let s2 = s1.clone();
            assert_eq!(s1, s2);

            drop(s1);
            assert_eq!(s2, "hello");
        });
    }

    #[test]
    fn test_backed_str_eq() {
        Python::with_gil(|py| {
            let s1: PyBackedStr = PyString::new_bound(py, "hello").try_into().unwrap();
            let s2: PyBackedStr = PyString::new_bound(py, "hello").try_into().unwrap();
            assert_eq!(s1, "hello");
            assert_eq!(s1, s2);

            let s3: PyBackedStr = PyString::new_bound(py, "abcde").try_into().unwrap();
            assert_eq!("abcde", s3);
            assert_ne!(s1, s3);
        });
    }

    #[test]
    fn test_backed_str_hash() {
        Python::with_gil(|py| {
            let h = {
                let mut hasher = DefaultHasher::new();
                "abcde".hash(&mut hasher);
                hasher.finish()
            };

            let s1: PyBackedStr = PyString::new_bound(py, "abcde").try_into().unwrap();
            let h1 = {
                let mut hasher = DefaultHasher::new();
                s1.hash(&mut hasher);
                hasher.finish()
            };

            assert_eq!(h, h1);
        });
    }

    #[test]
    fn test_backed_str_ord() {
        Python::with_gil(|py| {
            let mut a = vec!["a", "c", "d", "b", "f", "g", "e"];
            let mut b = a
                .iter()
                .map(|s| PyString::new_bound(py, s).try_into().unwrap())
                .collect::<Vec<PyBackedStr>>();

            a.sort();
            b.sort();

            assert_eq!(a, b);
        })
    }

    #[test]
    fn test_backed_bytes_from_bytes_clone() {
        Python::with_gil(|py| {
            let b1: PyBackedBytes = PyBytes::new_bound(py, b"abcde").into();
            let b2 = b1.clone();
            assert_eq!(b1, b2);

            drop(b1);
            assert_eq!(b2, b"abcde");
        });
    }

    #[test]
    fn test_backed_bytes_from_bytearray_clone() {
        Python::with_gil(|py| {
            let b1: PyBackedBytes = PyByteArray::new_bound(py, b"abcde").into();
            let b2 = b1.clone();
            assert_eq!(b1, b2);

            drop(b1);
            assert_eq!(b2, b"abcde");
        });
    }

    #[test]
    fn test_backed_bytes_eq() {
        Python::with_gil(|py| {
            let b1: PyBackedBytes = PyBytes::new_bound(py, b"abcde").into();
            let b2: PyBackedBytes = PyByteArray::new_bound(py, b"abcde").into();

            assert_eq!(b1, b"abcde");
            assert_eq!(b1, b2);

            let b3: PyBackedBytes = PyBytes::new_bound(py, b"hello").into();
            assert_eq!(b"hello", b3);
            assert_ne!(b1, b3);
        });
    }

    #[test]
    fn test_backed_bytes_hash() {
        Python::with_gil(|py| {
            let h = {
                let mut hasher = DefaultHasher::new();
                b"abcde".hash(&mut hasher);
                hasher.finish()
            };

            let b1: PyBackedBytes = PyBytes::new_bound(py, b"abcde").into();
            let h1 = {
                let mut hasher = DefaultHasher::new();
                b1.hash(&mut hasher);
                hasher.finish()
            };

            let b2: PyBackedBytes = PyByteArray::new_bound(py, b"abcde").into();
            let h2 = {
                let mut hasher = DefaultHasher::new();
                b2.hash(&mut hasher);
                hasher.finish()
            };

            assert_eq!(h, h1);
            assert_eq!(h, h2);
        });
    }

    #[test]
    fn test_backed_bytes_ord() {
        Python::with_gil(|py| {
            let mut a = vec![b"a", b"c", b"d", b"b", b"f", b"g", b"e"];
            let mut b = a
                .iter()
                .map(|&b| PyBytes::new_bound(py, b).into())
                .collect::<Vec<PyBackedBytes>>();

            a.sort();
            b.sort();

            assert_eq!(a, b);
        })
    }
}
