use std::{

    cell::Cell,

    fs::File,

    io::Error,

    os::fd::{AsRawFd, FromRawFd},

    path::{Path, PathBuf},

};

use cpython::{

    ObjectProtocol, PyBytes, PyClone, PyDict, PyErr, PyInt, PyObject,

    PyResult, PyTuple, Python, PythonObject, ToPyObject,

};

use hg::{

    errors::{HgError, IoResultExt},

    exit_codes,

    utils::files::{get_bytes_from_path, get_path_from_bytes},

    vfs::Vfs,

};

/// Wrapper around a Python VFS object to call back into Python from `hg-core`.

pub struct PyVfs {

    inner: PyObject,

}

impl Clone for PyVfs {

    fn clone(&self) -> Self {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        Self {

            inner: self.inner.clone_ref(py),

        }

    }

}

impl PyVfs {

    pub fn new(_py: Python, py_vfs: PyObject) -> PyResult<Self> {

        Ok(Self { inner: py_vfs })

    }

    fn inner_open(

        &self,

        filename: &Path,

        create: bool,

        check_ambig: bool,

        atomic_temp: bool,

        write: bool,

    ) -> Result<(File, Option<PathBuf>), HgError> {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        let mode = if atomic_temp {

            PyBytes::new(py, b"w")

        } else if create {

            PyBytes::new(py, b"w+")

        } else if write {

            PyBytes::new(py, b"r+")

        } else {

            PyBytes::new(py, b"rb")

        };

        let res = self.inner.call(

            py,

            (

                PyBytes::new(py, &get_bytes_from_path(filename)),

                mode,

                atomic_temp,

                check_ambig,

            ),

            None,

        );

        match res {

            Ok(tup) => {

                let tup = tup

                    .extract::<PyTuple>(py)

                    .map_err(|e| vfs_error("vfs did not return a tuple", e))?;

                let fileno = tup.get_item(py, 0).extract(py).map_err(|e| {

                    vfs_error("vfs did not return a valid fileno", e)

                })?;

                let temp_name = tup.get_item(py, 1);

                // Safety: this must be a valid owned file descriptor, and

                // Python has just given it to us, it will only exist here now

                let file = unsafe { File::from_raw_fd(fileno) };

                let temp_name = if atomic_temp {

                    Some(

                        get_path_from_bytes(

                            temp_name

                                .extract::<PyBytes>(py)

                                .map_err(|e| vfs_error("invalid tempname", e))?

                                .data(py),

                        )

                        .to_owned(),

                    )

                } else {

                    None

                };

                Ok((file, temp_name))

            }

            Err(mut e) => {

                // TODO surely there is a better way of comparing

                if e.instance(py).get_type(py).name(py) == "FileNotFoundError"

                {

                    return Err(HgError::IoError {

                        error: Error::new(

                            std::io::ErrorKind::NotFound,

                            e.instance(py).to_string(),

                        ),

                        context: hg::errors::IoErrorContext::ReadingFile(

                            filename.to_owned(),

                        ),

                    });

                }

                Err(vfs_error("failed to call opener", e))

            }

        }

    }

}

fn vfs_error(reason: impl Into<String>, mut error: PyErr) -> HgError {

    let gil = &Python::acquire_gil();

    let py = gil.python();

    HgError::abort(

        format!("{}: {}", reason.into(), error.instance(py)),

        exit_codes::ABORT,

        None,

    )

}

py_class!(pub class PyFile |py| {

    data number: Cell<i32>;

    def fileno(&self) -> PyResult<PyInt> {

        Ok(self.number(py).get().to_py_object(py))

    }

});

impl Vfs for PyVfs {

    fn open(&self, filename: &Path) -> Result<File, HgError> {

        self.inner_open(filename, false, false, false, true)

            .map(|(f, _)| f)

    }

    fn open_read(&self, filename: &Path) -> Result<File, HgError> {

        self.inner_open(filename, false, false, false, false)

            .map(|(f, _)| f)

    }

    fn open_check_ambig(

        &self,

        filename: &Path,

    ) -> Result<std::fs::File, HgError> {

        self.inner_open(filename, false, true, false, true)

            .map(|(f, _)| f)

    }

    fn create(&self, filename: &Path) -> Result<std::fs::File, HgError> {

        self.inner_open(filename, true, false, false, true)

            .map(|(f, _)| f)

    }

    fn create_atomic(

        &self,

        filename: &Path,

        check_ambig: bool,

    ) -> Result<hg::vfs::AtomicFile, HgError> {

        self.inner_open(filename, true, false, true, true).map(

            |(fp, temp_name)| {

                hg::vfs::AtomicFile::new(

                    fp,

                    check_ambig,

                    temp_name.expect("temp name should exist"),

                    filename.to_owned(),

                )

            },

        )

    }

    fn file_size(&self, file: &File) -> Result<u64, HgError> {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        let raw_fd = file.as_raw_fd();

        let py_fd = PyFile::create_instance(py, Cell::new(raw_fd))

            .expect("create_instance cannot fail");

        let fstat = self

            .inner

            .call_method(py, "fstat", (py_fd,), None)

            .map_err(|e| {

                vfs_error(format!("failed to fstat fd '{}'", raw_fd), e)

            })?;

        fstat

            .getattr(py, "st_size")

            .map(|v| {

                v.extract(py).map_err(|e| {

                    vfs_error(format!("invalid size for fd '{}'", raw_fd), e)

                })

            })

            .map_err(|e| {

                vfs_error(format!("failed to get size of fd '{}'", raw_fd), e)

            })?

    }

    fn exists(&self, filename: &Path) -> bool {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        self.inner

            .call_method(

                py,

                "exists",

                (PyBytes::new(py, &get_bytes_from_path(filename)),),

                None,

            )

            .unwrap_or_else(|_| false.into_py_object(py).into_object())

            .extract(py)

            .unwrap()

    }

    fn unlink(&self, filename: &Path) -> Result<(), HgError> {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        if let Err(e) = self.inner.call_method(

            py,

            "unlink",

            (PyBytes::new(py, &get_bytes_from_path(filename)),),

            None,

        ) {

            return Err(vfs_error(

                format!("failed to unlink '{}'", filename.display()),

                e,

            ));

        }

        Ok(())

    }

    fn rename(

        &self,

        from: &Path,

        to: &Path,

        check_ambig: bool,

    ) -> Result<(), HgError> {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        let kwargs = PyDict::new(py);

        kwargs

            .set_item(py, "checkambig", check_ambig)

            .map_err(|e| vfs_error("dict setitem failed", e))?;

        if let Err(e) = self.inner.call_method(

            py,

            "rename",

            (

                PyBytes::new(py, &get_bytes_from_path(from)),

                PyBytes::new(py, &get_bytes_from_path(to)),

            ),

            Some(&kwargs),

        ) {

            let msg = format!(

                "failed to rename '{}' to '{}'",

                from.display(),

                to.display()

            );

            return Err(vfs_error(msg, e));

        }

        Ok(())

    }

    fn copy(&self, from: &Path, to: &Path) -> Result<(), HgError> {

        let gil = &Python::acquire_gil();

        let py = gil.python();

        let from = self

            .inner

            .call_method(

                py,

                "join",

                (PyBytes::new(py, &get_bytes_from_path(from)),),

                None,

            )

            .unwrap();

        let from = from.extract::<PyBytes>(py).unwrap();

        let from = get_path_from_bytes(from.data(py));

        let to = self

            .inner

            .call_method(

                py,

                "join",

                (PyBytes::new(py, &get_bytes_from_path(to)),),

                None,

            )

            .unwrap();

        let to = to.extract::<PyBytes>(py).unwrap();

        let to = get_path_from_bytes(to.data(py));

        std::fs::copy(from, to).when_writing_file(to)?;

        Ok(())

    }

}