1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
// Copyright (c) 2015 Daniel Grunwald
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use libc::c_int;
use std::ffi::CString;
use std::marker::PhantomData;

use crate::err::{self, PyErr, PyResult};
use crate::ffi;
use crate::objects::{PyBool, PyDict, PyModule, PyObject, PyType};
use crate::pythonrun::GILGuard;

/// Marker type that indicates that the GIL is currently held.
///
/// The 'Python' struct is a zero-size marker struct that is required for most Python operations.
/// This is used to indicate that the operation accesses/modifies the Python interpreter state,
/// and thus can only be called if the Python interpreter is initialized and the
/// Python global interpreter lock (GIL) is acquired.
/// The lifetime `'p` represents the lifetime of the Python interpreter.
///
/// You can imagine the GIL to be a giant `Mutex<PythonInterpreterState>`.
/// The type `Python<'p>` then acts like a reference `&'p PythonInterpreterState`.
#[derive(Copy, Clone)]
pub struct Python<'p>(PhantomData<&'p GILGuard>);

/// Trait implemented by all Python object types.
pub trait PythonObject: crate::conversion::ToPyObject + Send + Sized + 'static {
    /// Casts the Python object to PyObject.
    fn as_object(&self) -> &PyObject;

    /// Casts the Python object to PyObject.
    fn into_object(self) -> PyObject;

    /// Unchecked downcast from PyObject to Self.
    /// Undefined behavior if the input object does not have the expected type.
    unsafe fn unchecked_downcast_from(obj: PyObject) -> Self;

    /// Unchecked downcast from PyObject to Self.
    /// Undefined behavior if the input object does not have the expected type.
    unsafe fn unchecked_downcast_borrow_from(obj: &PyObject) -> &Self;
}

// Marker type that indicates an error while downcasting
pub struct PythonObjectDowncastError<'p> {
    pub(crate) py: Python<'p>,
    pub(crate) expected_type_name: String,
    pub(crate) received_type: PyType,
}

impl<'p> PythonObjectDowncastError<'p> {
    pub fn new(
        py: Python<'p>,
        expected_type_name: impl Into<String>,
        received_type: PyType,
    ) -> Self {
        let expected_type_name = expected_type_name.into();
        PythonObjectDowncastError {
            py,
            expected_type_name,
            received_type,
        }
    }
}

/// Trait implemented by Python object types that allow a checked downcast.
pub trait PythonObjectWithCheckedDowncast: PythonObject {
    /// Cast from PyObject to a concrete Python object type.
    fn downcast_from(py: Python<'_>, obj: PyObject) -> Result<Self, PythonObjectDowncastError<'_>>;

    /// Cast from PyObject to a concrete Python object type.
    fn downcast_borrow_from<'a, 'p>(
        py: Python<'p>,
        obj: &'a PyObject,
    ) -> Result<&'a Self, PythonObjectDowncastError<'p>>;
}

/// Trait implemented by Python object types that have a corresponding type object.
pub trait PythonObjectWithTypeObject: PythonObjectWithCheckedDowncast {
    /// Retrieves the type object for this Python object type.
    fn type_object(py: Python) -> PyType;
}

pub trait PyClone: Sized {
    fn clone_ref(&self, py: Python) -> Self;
}

impl<T> PyClone for T
where
    T: PythonObject,
{
    #[inline]
    fn clone_ref(&self, py: Python) -> T {
        let ptr = self.as_object().as_ptr();
        unsafe { T::unchecked_downcast_from(PyObject::from_borrowed_ptr(py, ptr)) }
    }
}

impl<T> PyClone for Option<T>
where
    T: PyClone,
{
    #[inline]
    fn clone_ref(&self, py: Python) -> Option<T> {
        self.as_ref().map(|v| v.clone_ref(py))
    }
}

pub trait PyDrop: Sized {
    fn release_ref(self, py: Python);
}

impl<T> PyDrop for T
where
    T: PythonObject,
{
    #[inline]
    fn release_ref(self, _py: Python) {
        let ptr = self.into_object().steal_ptr();
        unsafe {
            ffi::Py_DECREF(ptr);
        }
    }
}

impl<T> PyDrop for Option<T>
where
    T: PyDrop,
{
    #[inline]
    fn release_ref(self, py: Python) {
        if let Some(v) = self {
            v.release_ref(py)
        }
    }
}

/// This trait allows retrieving the underlying FFI pointer from Python objects.
pub trait ToPythonPointer {
    /// Retrieves the underlying FFI pointer (as a borrowed pointer).
    fn as_ptr(&self) -> *mut ffi::PyObject;

    /// Retrieves the underlying FFI pointer as a "stolen pointer".
    fn steal_ptr(self, py: Python) -> *mut ffi::PyObject;
}

/// ToPythonPointer for borrowed Python pointers.
impl ToPythonPointer for PyObject {
    #[inline]
    fn as_ptr(&self) -> *mut ffi::PyObject {
        self.as_ptr()
    }

    #[inline]
    fn steal_ptr(self, _py: Python) -> *mut ffi::PyObject {
        self.steal_ptr()
    }
}

/// ToPythonPointer for borrowed Python pointers.
impl<'a, T> ToPythonPointer for &'a T
where
    T: PythonObject,
{
    #[inline]
    fn as_ptr(&self) -> *mut ffi::PyObject {
        self.as_object().as_ptr()
    }

    #[inline]
    fn steal_ptr(self, py: Python) -> *mut ffi::PyObject {
        self.as_object().clone_ref(py).steal_ptr()
    }
}

/// Convert None into a null pointer.
impl<T> ToPythonPointer for Option<T>
where
    T: ToPythonPointer,
{
    #[inline]
    fn as_ptr(&self) -> *mut ffi::PyObject {
        match *self {
            Some(ref t) => t.as_ptr(),
            None => std::ptr::null_mut(),
        }
    }

    #[inline]
    fn steal_ptr(self, py: Python) -> *mut ffi::PyObject {
        match self {
            Some(t) => t.steal_ptr(py),
            None => std::ptr::null_mut(),
        }
    }
}

impl<'p> Python<'p> {
    /// Retrieve Python instance under the assumption that the GIL is already acquired at this point,
    /// and stays acquired for the lifetime `'p`.
    ///
    /// Because the output lifetime `'p` is not connected to any input parameter,
    /// care must be taken that the compiler infers an appropriate lifetime for `'p`
    /// when calling this function.
    #[inline]
    pub unsafe fn assume_gil_acquired() -> Python<'p> {
        Python(PhantomData)
    }

    /// Acquires the global interpreter lock, which allows access to the Python runtime.
    ///
    /// If the Python runtime is not already initialized, this function will initialize it.
    /// See [prepare_freethreaded_python()](fn.prepare_freethreaded_python.html) for details.
    #[inline]
    pub fn acquire_gil() -> GILGuard {
        GILGuard::acquire()
    }

    /// Temporarily releases the GIL, thus allowing other Python threads to run.
    pub fn allow_threads<T, F>(self, f: F) -> T
    where
        F: Send + FnOnce() -> T,
    {
        // The `Send` bound on the closure prevents the user from
        // transferring the `Python` token into the closure.
        unsafe {
            let save = ffi::PyEval_SaveThread();
            let result = f();
            ffi::PyEval_RestoreThread(save);
            result
        }
    }

    /// Evaluates a Python expression in the given context and returns the result.
    ///
    /// If `globals` is `None`, it defaults to Python module `__main__`.
    /// If `locals` is `None`, it defaults to the value of `globals`.
    pub fn eval(
        self,
        code: &str,
        globals: Option<&PyDict>,
        locals: Option<&PyDict>,
    ) -> PyResult<PyObject> {
        self.run_code(code, ffi::Py_eval_input, globals, locals)
    }

    /// Executes one or more Python statements in the given context.
    ///
    /// If `globals` is `None`, it defaults to Python module `__main__`.
    /// If `locals` is `None`, it defaults to the value of `globals`.
    pub fn run(
        self,
        code: &str,
        globals: Option<&PyDict>,
        locals: Option<&PyDict>,
    ) -> PyResult<()> {
        self.run_code(code, ffi::Py_file_input, globals, locals)?;
        Ok(())
    }

    /// Runs code in the given context.
    /// `start` indicates the type of input expected:
    /// one of `Py_single_input`, `Py_file_input`, or `Py_eval_input`.
    ///
    /// If `globals` is `None`, it defaults to Python module `__main__`.
    /// If `locals` is `None`, it defaults to the value of `globals`.
    fn run_code(
        self,
        code: &str,
        start: c_int,
        globals: Option<&PyDict>,
        locals: Option<&PyDict>,
    ) -> PyResult<PyObject> {
        let code = CString::new(code).unwrap();

        unsafe {
            let mptr = ffi::PyImport_AddModule("__main__\0".as_ptr() as *const _);

            if mptr.is_null() {
                return Err(PyErr::fetch(self));
            }

            let mdict = ffi::PyModule_GetDict(mptr);

            let globals = match globals {
                Some(g) => g.as_ptr(),
                None => mdict,
            };

            let locals = match locals {
                Some(l) => l.as_ptr(),
                None => globals,
            };

            let res_ptr =
                ffi::PyRun_StringFlags(code.as_ptr(), start, globals, locals, std::ptr::null_mut());

            err::result_from_owned_ptr(self, res_ptr)
        }
    }

    /// Gets the Python builtin value `None`.
    #[allow(non_snake_case)] // the Python keyword starts with uppercase
    #[inline]
    pub fn None(self) -> PyObject {
        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_None()) }
    }

    /// Gets the Python builtin value `True`.
    #[allow(non_snake_case)] // the Python keyword starts with uppercase
    #[inline]
    pub fn True(self) -> PyBool {
        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_True()).unchecked_cast_into::<PyBool>() }
    }

    /// Gets the Python builtin value `False`.
    #[allow(non_snake_case)] // the Python keyword starts with uppercase
    #[inline]
    pub fn False(self) -> PyBool {
        unsafe {
            PyObject::from_borrowed_ptr(self, ffi::Py_False()).unchecked_cast_into::<PyBool>()
        }
    }

    /// Gets the Python builtin value `NotImplemented`.
    #[allow(non_snake_case)] // the Python keyword starts with uppercase
    #[inline]
    pub fn NotImplemented(self) -> PyObject {
        unsafe { PyObject::from_borrowed_ptr(self, ffi::Py_NotImplemented()) }
    }

    /// Gets the Python type object for type T.
    pub fn get_type<T>(self) -> PyType
    where
        T: PythonObjectWithTypeObject,
    {
        T::type_object(self)
    }

    /// Import the Python module with the specified name.
    pub fn import(self, name: &str) -> PyResult<PyModule> {
        PyModule::import(self, name)
    }
}

impl<'p> std::fmt::Debug for PythonObjectDowncastError<'p> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
        f.write_str("PythonObjectDowncastError")
    }
}

#[cfg(test)]
mod test {
    use crate::{PyDict, Python};

    #[test]
    fn test_eval() {
        let gil = Python::acquire_gil();
        let py = gil.python();

        // Make sure builtin names are accessible
        let v: i32 = py
            .eval("min(1, 2)", None, None)
            .unwrap()
            .extract(py)
            .unwrap();
        assert_eq!(v, 1);

        let d = PyDict::new(py);
        d.set_item(py, "foo", 13).unwrap();

        // Inject our own local namespace
        let v: i32 = py
            .eval("foo + 29", None, Some(&d))
            .unwrap()
            .extract(py)
            .unwrap();
        assert_eq!(v, 42);

        // Make sure builtin names are still accessible when using a local namespace
        let v: i32 = py
            .eval("min(foo, 2)", None, Some(&d))
            .unwrap()
            .extract(py)
            .unwrap();
        assert_eq!(v, 2);
    }
}