#define _GNU_SOURCE
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/fail.h>
#include <caml/callback.h>
#include <caml/custom.h>
#include <caml/alloc.h>
#include <sys/param.h>
#include <string.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdcompat.h>
#include "pyml_stubs.h"

static FILE *(*Python__Py_fopen)(const char *pathname, const char *mode);

static FILE *(*Python__Py_wfopen)(const wchar_t *pathname, const char *mode);

static void *xmalloc(size_t size)
{
    void *p = malloc(size);
    if (!p) {
        failwith("Virtual memory exhausted\n");
    }
    return p;
}

#ifdef _WIN32
#include <windows.h>

typedef HINSTANCE library_t;

static library_t
open_library(const char *filename)
{
    return LoadLibrary(filename);
}

void
close_library(library_t library)
{
    if (!FreeLibrary(library)) {
        fprintf(stderr, "close_library.\n");
        exit(EXIT_FAILURE);
    }
}

static library_t
get_default_library(void)
{
    return GetModuleHandle(0);
}

static void *
find_symbol(library_t library, const char *name)
{
    return GetProcAddress(library, name);
}

int
unsetenv(const char *name)
{
    size_t len = strlen(name);
    char string[len + 2];
    snprintf(string, len + 2, "%s=", name);
    return _putenv(string);
}

extern int win_CRT_fd_of_filedescr(value handle);

static FILE *
file_of_file_descr(value file_descr, const char *mode)
{
    CAMLparam1(file_descr);
    int fd = win_CRT_fd_of_filedescr(file_descr);
    FILE *result = _fdopen(dup(fd), mode);
    CAMLreturnT(FILE *, result);
}
#else
#include <dlfcn.h>

typedef void *library_t;

static library_t
open_library(const char *filename)
{
    return dlopen(filename, RTLD_LAZY | RTLD_GLOBAL);
}

void
close_library(library_t filename)
{
    if (dlclose(filename)) {
        fprintf(stderr, "close_library: %s.\n", dlerror());
        exit(EXIT_FAILURE);
    }
}

static library_t
get_default_library(void)
{
    return RTLD_DEFAULT;
}

static void *
find_symbol(library_t library, const char *name)
{
    return dlsym(library, name);
}

static FILE *
file_of_file_descr(value file_descr, const char *mode)
{
    CAMLparam1(file_descr);
    int fd = Int_val(file_descr);
    FILE *result = fdopen(dup(fd), mode);
    CAMLreturnT(FILE *, result);
}
#endif

/* The following definitions are extracted and simplified from
#include <Python.h>
*/

typedef struct {
    int cf_flags;
} PyCompilerFlags;

#define Py_TPFLAGS_INT_SUBCLASS         (1L<<23)
#define Py_TPFLAGS_LONG_SUBCLASS        (1UL << 24)
#define Py_TPFLAGS_LIST_SUBCLASS        (1UL << 25)
#define Py_TPFLAGS_TUPLE_SUBCLASS       (1UL << 26)
#define Py_TPFLAGS_BYTES_SUBCLASS       (1UL << 27)
#define Py_TPFLAGS_UNICODE_SUBCLASS     (1UL << 28)
#define Py_TPFLAGS_DICT_SUBCLASS        (1UL << 29)
#define Py_TPFLAGS_BASE_EXC_SUBCLASS    (1UL << 30)
#define Py_TPFLAGS_TYPE_SUBCLASS        (1UL << 31)

#define Py_LT 0
#define Py_LE 1
#define Py_EQ 2
#define Py_NE 3
#define Py_GT 4
#define Py_GE 5

typedef PyObject *(*PyCFunction)(PyObject *, PyObject *);

typedef struct PyMethodDef {
    const char *ml_name;
    PyCFunction ml_meth;
    int ml_flags;
    const char	*ml_doc;
} PyMethodDef;

typedef void (*PyCapsule_Destructor)(PyObject *);

static void *Python27__PyObject_NextNotImplemented;

/* Global variables for the library */

/* version_major != 0 iff the library is initialized */
static int version_major;
static int version_minor;

static library_t library;

/* Functions that are special enough to deserved to be wrapped specifically */

/* Wrapped by pywrap_closure */
static PyObject *(*Python_PyCFunction_NewEx)
(PyMethodDef *, PyObject *, PyObject *);

/* Wrapped by closure and capsule */
static void *(*Python27_PyCapsule_New)
    (void *, const char *, PyCapsule_Destructor);
static void *(*Python27_PyCapsule_GetPointer)(PyObject *, const char *);
static int (*Python27_PyCapsule_IsValid)(PyObject *, const char *);
static void *(*Python2_PyCObject_FromVoidPtr)(void *, void (*)(void *));
static void *(*Python2_PyCObject_AsVoidPtr)(PyObject *);

/* Hack for multi-arguments */
static PyObject *(*Python_PyObject_CallFunctionObjArgs)(PyObject *, ...);
static PyObject *(*Python_PyObject_CallMethodObjArgs)(
  PyObject *, PyObject *, ...);

/* Wrapped by PyErr_Fetch_wrapper */
static void (*Python_PyErr_Fetch)(PyObject **, PyObject **, PyObject **);
static void (*Python_PyErr_NormalizeException)
(PyObject **, PyObject **, PyObject **);

/* Resolved differently between Python 2 and Python 3 */
static PyObject *Python__Py_FalseStruct;

/* Buffer and size */
static int (*Python_PyString_AsStringAndSize)
(PyObject *, char **, Py_ssize_t *);
static int (*Python_PyObject_AsCharBuffer)
(PyObject *, const char **, Py_ssize_t *);
static int (*Python_PyObject_AsReadBuffer)
(PyObject *, const void **, Py_ssize_t *);
static int (*Python_PyObject_AsWriteBuffer)
(PyObject *, void **, Py_ssize_t *);

/* Length argument */
static PyObject *(*Python_PyLong_FromString)(const char *, const char **, int);

/* Internal use only */
static void (*Python_PyMem_Free)(void *);

static enum UCS { UCS_NONE, UCS2, UCS4 } ucs;

/* Single instance of () */
static PyObject *tuple_empty;

#include "pyml.h"

static void *getcustom( value v )
{
    return *((void **)Data_custom_val(v));
}

static void pydecref( value v )
{
    if (getcustom(v)) {
        Py_DECREF((PyObject *)getcustom(v));
    }
}

static int
rich_compare_bool_nofail
(PyObject *o1, PyObject *o2, int opid)
{
    int result = Python_PyObject_RichCompareBool(o1, o2, opid);
    if (result == -1) {
        Python_PyErr_Clear();
        result = 0;
    }
    return result;
}

static int
pycompare(value v1, value v2)
{
    int result;
    PyObject *o1 = getcustom(v1);
    PyObject *o2 = getcustom(v2);

    if (o1 && !o2)
        result = -1;
    else if (o2 && !o1)
        result = 1;
    else if (!o1 && !o2)
        result = 0;
    else if (version_major < 3)
        Python2_PyObject_Cmp(o1, o2, &result);
    else if (rich_compare_bool_nofail(o1, o2, Py_EQ))
        result = 0;
    else if (rich_compare_bool_nofail(o1, o2, Py_LT))
        result = -1;
    else if (rich_compare_bool_nofail(o1, o2, Py_GT))
        result = 1;
    else
        result = -1;

    return result;
}

static intnat
pyhash( value v )
{
    if (getcustom(v)) {
        intnat result = Python_PyObject_Hash((PyObject *)getcustom(v));
        if (result == -1) {
            Python_PyErr_Clear();
        }
        return result;
    }
    else {
        return 0;
    }
}

static uintnat
pydeserialize(void *dst)
{
    return 0L;
}

struct custom_operations pyops =
{
    "PythonObject",
    pydecref,
    pycompare,
    pyhash,
    custom_serialize_default,
    pydeserialize
};

enum code {
    CODE_NULL,
    CODE_NONE,
    CODE_TRUE,
    CODE_FALSE,
    CODE_TUPLE_EMPTY
};

static void *
resolve(const char *symbol)
{
    void *result = find_symbol(library, symbol);
    if (!result) {
        char *fmt = "Cannot resolve %s.\n";
        ssize_t size = snprintf(NULL, 0, fmt, symbol);
        char *msg = xmalloc(size + 1);
        snprintf(msg, size + 1, fmt, symbol);
        failwith(msg);
    }
    return result;
}

static void *
resolve_optional(const char *symbol)
{
    return find_symbol(library, symbol);
}

value
pyml_wrap(PyObject *object, bool steal)
{
    CAMLparam0();
    CAMLlocal1(v);
    if (!object) {
        CAMLreturn(Val_int(CODE_NULL));
    }
    if (object == Python__Py_NoneStruct) {
        CAMLreturn(Val_int(CODE_NONE));
    }
    if (object == Python__Py_TrueStruct) {
        CAMLreturn(Val_int(CODE_TRUE));
    }
    if (object == Python__Py_FalseStruct) {
        CAMLreturn(Val_int(CODE_FALSE));
    }
    unsigned long flags =
        ((struct _typeobject *) pyobjectdescr(pyobjectdescr(object)->ob_type))
        ->tp_flags;
    if (flags & Py_TPFLAGS_TUPLE_SUBCLASS
        && Python_PySequence_Length(object) == 0) {
        CAMLreturn(Val_int(CODE_TUPLE_EMPTY));
    }
    if (!steal) {
        Py_INCREF(object);
    }
    v = caml_alloc_custom(&pyops, sizeof(PyObject *), 100, 30000000);
    *((PyObject **)Data_custom_val(v)) = object;
    CAMLreturn(v);
}

PyObject *
pyml_unwrap(value v)
{
    if (Is_long(v))
        switch (Int_val(v)) {
        case CODE_NULL:
            return NULL;
        case CODE_NONE:
            return Python__Py_NoneStruct;
        case CODE_TRUE:
            return Python__Py_TrueStruct;
        case CODE_FALSE:
            return Python__Py_FalseStruct;
        case CODE_TUPLE_EMPTY:
            return tuple_empty;
        }

    return *((PyObject **)Data_custom_val(v));
}

/*
static value
pyml_wrap_compilerflags(PyCompilerFlags *flags)
{
    CAMLparam0();
    CAMLlocal2(ref, some);
    if (!flags) {
        CAMLreturn(Val_int(0));
    }
    else {
        ref = caml_alloc(0, 1);
        Store_field(ref, 0, Val_int(flags->cf_flags));
        some = caml_alloc(0, 1);
        Store_field(some, 0, ref);
        CAMLreturn(some);
    }
}
*/

static PyCompilerFlags *
pyml_unwrap_compilerflags(value v)
{
    CAMLparam1(v);
    if (Is_block(v)) {
        PyCompilerFlags *flags = malloc(sizeof(PyCompilerFlags));
        flags->cf_flags = Int_val(Field(Field(v, 0), 0));
        CAMLreturnT(PyCompilerFlags *, flags);
    }
    else {
        CAMLreturnT(PyCompilerFlags *, NULL);
    }
}

/*
static value
pyml_wrap_intref(int v)
{
    CAMLparam0();
    CAMLlocal1(ref);
    ref = caml_alloc(0, 1);
    Store_field(ref, 0, Val_int(v));
    CAMLreturn(ref);
}
*/

static int
pyml_unwrap_intref(value v)
{
    CAMLparam1(v);
    CAMLreturnT(int, Int_val(Field(v, 0)));
}

static void *
unwrap_capsule(PyObject *obj, const char *type)
{
    if (Python27_PyCapsule_GetPointer) {
        return Python27_PyCapsule_GetPointer(obj, type);
    }
    else {
        return Python2_PyCObject_AsVoidPtr(obj);
    }
}


static PyObject *
wrap_capsule(void *ptr, char *type, void (*destr)(PyObject *))
{
    if (Python27_PyCapsule_New) {
        return Python27_PyCapsule_New(ptr, type, destr);
    }
    else {
        return Python2_PyCObject_FromVoidPtr(ptr, (void(*)(void *))destr);
    }
}

static PyObject *
pycall_callback(PyObject *obj, PyObject *args)
{
    CAMLparam0();
    CAMLlocal3(ml_out, ml_func, ml_args);
    PyObject *out;
    void *p = unwrap_capsule(obj, "ocaml-closure");
    if (!p) {
        Py_INCREF(Python__Py_NoneStruct);
        CAMLreturnT(PyObject *, Python__Py_NoneStruct);
    }
    ml_func = *(value *) p;
    ml_args = pyml_wrap(args, false);
    ml_out = caml_callback(ml_func, ml_args);
    out = pyml_unwrap(ml_out);
    Py_XINCREF(out);
    CAMLreturnT(PyObject *, out);
}

static PyObject *
pycall_callback_with_keywords(PyObject *obj, PyObject *args, PyObject *keywords)
{
    CAMLparam0();
    CAMLlocal4(ml_out, ml_func, ml_args, ml_keywords);
    PyObject *out;
    void *p = unwrap_capsule(obj, "ocaml-closure");
    if (!p) {
        Py_INCREF(Python__Py_NoneStruct);
        CAMLreturnT(PyObject *, Python__Py_NoneStruct);
    }
    ml_func = *(value *) p;
    ml_args = pyml_wrap(args, false);
    ml_keywords = pyml_wrap(keywords, false);
    ml_out = caml_callback2(ml_func, ml_args, ml_keywords);
    out = pyml_unwrap(ml_out);
    Py_XINCREF(out);
    CAMLreturnT(PyObject *, out);
}

static void
caml_destructor(PyObject *v, const char *capsule_name)
{
    value *valptr = (value *) unwrap_capsule(v, capsule_name);
    caml_remove_global_root(valptr);
    free(valptr);
}

static void
camldestr_capsule(PyObject *v)
{
    caml_destructor(v, "ocaml-capsule");
}

static PyObject *
camlwrap_capsule(value val, void *aux_str, int size)
{
    value *v = (value *) malloc(sizeof(value) + size);
    *v = val;
    memcpy((void *)v + sizeof(value), aux_str, size);
    caml_register_global_root(v);
    return wrap_capsule(v, "ocaml-capsule", camldestr_capsule);
}

static void *
caml_aux(PyObject *obj)
{
    value *v = (value *) unwrap_capsule(obj, "ocaml-closure");
    return (void *) v + sizeof(value);
}

void
pyml_assert_initialized()
{
    if (!version_major) {
        failwith("Run 'Py.initialize ()' first");
    }
}

void
pyml_assert_python2()
{
    if (version_major != 2) {
        pyml_assert_initialized();
        failwith("Python 2 needed");
    }
}

void
pyml_assert_ucs2()
{
    if (ucs != UCS2) {
        pyml_assert_initialized();
        failwith("Python with UCS2 needed");
    }
}

void
pyml_assert_ucs4()
{
    if (ucs != UCS4) {
        pyml_assert_initialized();
        failwith("Python with UCS4 needed");
    }
}

void
pyml_assert_python3()
{
    if (version_major != 3) {
        pyml_assert_initialized();
        failwith("Python 3 needed");
    }
}

void
pyml_check_symbol_available(void *symbol, char *symbol_name)
{
    if (!symbol) {
        char *fmt = "Symbol unavailable with this version of Python: %s.\n";
        ssize_t size = snprintf(NULL, 0, fmt, symbol_name);
        if (size < 0) {
          failwith("Symbol unavailable with this version of Python.\n");
          return;
        }
        char *msg = xmalloc(size + 1);
        size = snprintf(msg, size + 1, fmt, symbol_name);
        if (size < 0) {
          failwith("Symbol unavailable with this version of Python.\n");
          return;
        }
        failwith(msg);
    }
}

void *
deref_not_null(void *pointer)
{
    if (pointer) {
        return *(void **) pointer;
    }
    else {
        return NULL;
    }
}

struct pyml_closure {
  value value;
  PyMethodDef method;
};

static char *anon_closure = "anonymous_closure";

static void
camldestr_closure(PyObject *v)
{
    struct pyml_closure *valptr = unwrap_capsule(v, "ocaml-closure");
    const char *ml_doc = valptr->method.ml_doc;
    const char *ml_name = valptr->method.ml_name;
    caml_remove_global_root((value *)valptr);
    free(valptr);
    free((void *) ml_doc);
    if (ml_name != anon_closure) free((void *) ml_name);
}

CAMLprim value
pyml_wrap_closure(value name, value docstring, value closure)
{
    CAMLparam3(name, docstring, closure);
    pyml_assert_initialized();
    PyMethodDef ml;
    PyObject *obj;
    PyMethodDef *ml_def;
    ml.ml_name = anon_closure;
    if (name != Val_int(0)) {
      ml.ml_name = strdup(String_val(Field(name, 0)));
    }
    if (Tag_val(closure) == 0) {
        ml.ml_flags = 1;
        ml.ml_meth = pycall_callback;
    }
    else {
        ml.ml_flags = 3;
        ml.ml_meth = (PyCFunction) pycall_callback_with_keywords;
    }
    ml.ml_doc = strdup(String_val(docstring));
    struct pyml_closure *v = malloc(sizeof(struct pyml_closure));
    v->value = Field(closure, 0);
    v->method = ml;
    caml_register_global_root(&v->value);
    obj = wrap_capsule(v, "ocaml-closure", camldestr_closure);
    ml_def = (PyMethodDef *) caml_aux(obj);
    PyObject *f = Python_PyCFunction_NewEx(ml_def, obj, NULL);
    Py_DECREF(obj);
    CAMLreturn(pyml_wrap(f, true));
}

int debug_build;

CAMLprim value
py_load_library(value filename_ocaml, value debug_build_ocaml)
{
    CAMLparam2(filename_ocaml, debug_build_ocaml);
    if (Is_block(filename_ocaml)) {
        const char *filename = String_val(Field(filename_ocaml, 0));
        library = open_library(filename);
        if (!library) {
            failwith("Library not found");
        }
    }
    else {
        library = get_default_library();
    }
    Python_Py_GetVersion = find_symbol(library, "Py_GetVersion");
    if (!Python_Py_GetVersion) {
        failwith("No Python symbol");
    }
    const char *version = Python_Py_GetVersion();
    version_major = version[0] - '0';
    version_minor = version[2] - '0';
    Python_PyCFunction_NewEx = resolve("PyCFunction_NewEx");
    if ((version_major == 2 && version_minor >= 7) || version_major >= 3) {
        Python27_PyCapsule_New = resolve("PyCapsule_New");
        Python27_PyCapsule_GetPointer = resolve("PyCapsule_GetPointer");
        Python27_PyCapsule_IsValid = resolve("PyCapsule_IsValid");
        Python27__PyObject_NextNotImplemented =
            resolve("_PyObject_NextNotImplemented");
    }
    Python_PyObject_CallFunctionObjArgs =
        resolve("PyObject_CallFunctionObjArgs");
    Python_PyObject_CallMethodObjArgs =
        resolve("PyObject_CallMethodObjArgs");
    Python_PyErr_Fetch = resolve("PyErr_Fetch");
    Python_PyErr_NormalizeException = resolve("PyErr_NormalizeException");
    Python_PyObject_AsCharBuffer = resolve_optional("PyObject_AsCharBuffer");
    Python_PyObject_AsReadBuffer = resolve_optional("PyObject_AsReadBuffer");
    Python_PyObject_AsWriteBuffer = resolve_optional("PyObject_AsWriteBuffer");
    if (version_major >= 3) {
        Python__Py_FalseStruct = resolve("_Py_FalseStruct");
        Python_PyString_AsStringAndSize = resolve("PyBytes_AsStringAndSize");
    }
    else {
        Python__Py_FalseStruct = resolve("_Py_ZeroStruct");
        Python_PyString_AsStringAndSize = resolve("PyString_AsStringAndSize");
    }
    Python_PyLong_FromString = resolve("PyLong_FromString");
    Python_PyMem_Free = resolve("PyMem_Free");
    if (version_major >= 3) {
        Python__Py_wfopen = resolve_optional("_Py_wfopen"); /* Python >=3.10 */
        Python__Py_fopen = resolve_optional("_Py_fopen");
    }
    else {
        Python2_PyCObject_FromVoidPtr = resolve("PyCObject_FromVoidPtr");
        Python2_PyCObject_AsVoidPtr = resolve("PyCObject_AsVoidPtr");
    }
    if (find_symbol(library, "PyUnicodeUCS2_AsEncodedString")) {
        ucs = UCS2;
    }
    else if (find_symbol(library, "PyUnicodeUCS4_AsEncodedString")) {
        ucs = UCS4;
    }
    else {
        ucs = UCS_NONE;
    }
#include "pyml_dlsyms.inc"
    Python_Py_Initialize();
    if (Is_block(debug_build_ocaml)) {
        debug_build = Int_val(Field(debug_build_ocaml, 0));
    }
    else {
        PyObject *sysconfig = Python_PyImport_ImportModule("sysconfig");
        PyObject *get_config_var =
            Python_PyObject_GetAttrString(sysconfig, "get_config_var");
        PyObject *args;
        PyObject *py_debug;
        PyObject *debug_build_py;
        char *py_debug_str = "Py_DEBUG";
        if (version_major >= 3) {
            py_debug = Python3_PyUnicode_FromStringAndSize(py_debug_str, 8);
        }
        else {
            py_debug = Python2_PyString_FromStringAndSize(py_debug_str, 8);
        }
        if (!py_debug) {
            failwith("py_debug");
        }
        args = Python_PyTuple_New(1);
        if (!args) {
            failwith("PyTuple_New");
        }
        if (Python_PyTuple_SetItem(args, 0, py_debug)) {
            failwith("PyTuple_SetItem");
        }
        debug_build_py =
            Python_PyEval_CallObjectWithKeywords(get_config_var, args, NULL);
        if (!debug_build_py) {
            failwith("PyEval_CallObjectWithKeywords");
        }
        if (version_major >= 3) {
            debug_build = Python_PyLong_AsLong(debug_build_py);
        }
        else {
            debug_build = Python2_PyInt_AsLong(debug_build_py);
        }
        if (debug_build == -1) {
            failwith("AsLong");
        }
    }
    tuple_empty = Python_PyTuple_New(0);
    CAMLreturn(Val_unit);
}

struct PyObjectDebug {
    PyObject *_ob_next;           \
    PyObject *_ob_prev;
    PyObjectDescr descr;
};

PyObjectDescr *pyobjectdescr(PyObject *obj) {
    if (debug_build) {
        return &((struct PyObjectDebug *) obj)->descr;
    }
    else {
        return (PyObjectDescr *) obj;
    }
}

CAMLprim value
py_is_debug_build()
{
    CAMLparam0();
    CAMLreturn(Val_int(debug_build));
}

CAMLprim value
py_finalize_library(value unit)
{
    CAMLparam1(unit);
    pyml_assert_initialized();
    Py_DECREF(tuple_empty);
    if (library != get_default_library()) {
        close_library(library);
    }
    version_major = 0;
    ucs = UCS_NONE;
    CAMLreturn(Val_unit);
}

CAMLprim value
py_unsetenv(value name_ocaml)
{
    CAMLparam1(name_ocaml);
    const char *name = String_val(name_ocaml);
    if (unsetenv(name) == -1) {
        failwith(strerror(errno));
    }
    CAMLreturn(Val_unit);
}

CAMLprim value
py_get_UCS(value unit)
{
    CAMLparam1(unit);
    pyml_assert_initialized();
    CAMLreturn(Val_int(ucs));
}

CAMLprim value
PyNull_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLreturn(Val_int(CODE_NULL));
}

CAMLprim value
PyNone_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLreturn(Val_int(CODE_NONE));
}

CAMLprim value
PyTrue_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLreturn(Val_int(CODE_TRUE));
}

CAMLprim value
PyFalse_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLreturn(Val_int(CODE_FALSE));
}

CAMLprim value
PyTuple_Empty_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLreturn(Val_int(CODE_TUPLE_EMPTY));
}

enum pytype_labels {
    PyUnknown,
    Bool,
    Bytes,
    Callable,
    Capsule,
    Closure,
    Dict,
    Float,
    List,
    Int,
    Long,
    Module,
    NoneType,
    Null,
    Tuple,
    Type,
    Unicode,
    Iter,
    Set
};

CAMLprim value
pytype(value object_ocaml)
{
    CAMLparam1(object_ocaml);
    pyml_assert_initialized();
    PyObject *object = pyml_unwrap(object_ocaml);
    if (!object) {
        CAMLreturn(Val_int(Null));
    }
    PyObject *ob_type = pyobjectdescr(object)->ob_type;
    struct _typeobject *typeobj = (struct _typeobject *) pyobjectdescr(ob_type);
    unsigned long flags = typeobj->tp_flags;
    int result;
    if (ob_type == Python_PyBool_Type) {
        result = Bool;
    }
    else if (flags & Py_TPFLAGS_BYTES_SUBCLASS) {
        result = Bytes;
    }
    else if (Python_PyCallable_Check(object)) {
        result = Callable;
    }
    else if (Python27_PyCapsule_IsValid
        && Python27_PyCapsule_IsValid(object, "ocaml-capsule")) {
        result = Capsule;
    }
    else if (Python27_PyCapsule_IsValid
        && Python27_PyCapsule_IsValid(object, "ocaml-closure")) {
        result = Closure;
    }
    else if (flags & Py_TPFLAGS_DICT_SUBCLASS) {
        result = Dict;
    }
    else if (ob_type == Python_PyFloat_Type ||
        Python_PyType_IsSubtype(ob_type, Python_PyFloat_Type)) {
        result = Float;
    }
    else if (flags & Py_TPFLAGS_LIST_SUBCLASS) {
        result = List;
    }
    else if (flags & Py_TPFLAGS_INT_SUBCLASS) {
        result = Int;
    }
    else if (flags & Py_TPFLAGS_LONG_SUBCLASS) {
        result = Long;
    }
    else if (ob_type == Python_PyModule_Type ||
        Python_PyType_IsSubtype(ob_type, Python_PyModule_Type)) {
        result = Module;
    }
    else if (object == Python__Py_NoneStruct) {
        result = NoneType;
    }
    else if (flags & Py_TPFLAGS_TUPLE_SUBCLASS) {
        result = Tuple;
    }
    else if (flags & Py_TPFLAGS_TYPE_SUBCLASS) {
        result = Type;
    }
    else if (flags & Py_TPFLAGS_UNICODE_SUBCLASS) {
        result = Unicode;
    }
    else if (ob_type == Python_PySet_Type) {
        result = Set;
    }
    else if (typeobj->tp_iternext != NULL &&
        typeobj->tp_iternext != &Python27__PyObject_NextNotImplemented) {
        result = Iter;
    }
    else {
        result = PyUnknown;
    }
    CAMLreturn(Val_int(result));
}

CAMLprim value
PyObject_CallFunctionObjArgs_wrapper(
    value callable_ocaml, value arguments_ocaml)
{
    CAMLparam2(callable_ocaml, arguments_ocaml);
    pyml_assert_initialized();
    PyObject *callable = pyml_unwrap(callable_ocaml);
    PyObject *result;
    mlsize_t argument_count = Wosize_val(arguments_ocaml);
    switch (argument_count) {
    case 0:
        result = Python_PyObject_CallFunctionObjArgs(callable, NULL);
        break;
    case 1:
        result = Python_PyObject_CallFunctionObjArgs
            (callable,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             NULL);
        break;
    case 2:
        result = Python_PyObject_CallFunctionObjArgs
            (callable,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             NULL);
        break;
    case 3:
        result = Python_PyObject_CallFunctionObjArgs
            (callable,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             NULL);
        break;
    case 4:
        result = Python_PyObject_CallFunctionObjArgs
            (callable,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             pyml_unwrap(Field(arguments_ocaml, 3)),
             NULL);
        break;
    case 5:
        result = Python_PyObject_CallFunctionObjArgs
            (callable,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             pyml_unwrap(Field(arguments_ocaml, 3)),
             pyml_unwrap(Field(arguments_ocaml, 4)),
             NULL);
        break;
    default:
        fprintf(stderr,
                "PyObject_CallFunctionObjArgs_wrapper not implemented for more "
                "than 5 arguments\n");
        exit(EXIT_FAILURE);
    }

    CAMLreturn(pyml_wrap(result, true));
}

CAMLprim value
PyObject_CallMethodObjArgs_wrapper(
    value object_ocaml, value name_ocaml, value arguments_ocaml)
{
    CAMLparam3(object_ocaml, name_ocaml, arguments_ocaml);
    pyml_assert_initialized();
    PyObject *object = pyml_unwrap(object_ocaml);
    PyObject *name = pyml_unwrap(name_ocaml);
    PyObject *result;
    mlsize_t argument_count = Wosize_val(arguments_ocaml);
    switch (argument_count) {
    case 0:
        result = Python_PyObject_CallMethodObjArgs(object, name, NULL);
        break;
    case 1:
        result = Python_PyObject_CallMethodObjArgs
            (object, name,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             NULL);
        break;
    case 2:
        result = Python_PyObject_CallMethodObjArgs
            (object, name,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             NULL);
        break;
    case 3:
        result = Python_PyObject_CallMethodObjArgs
            (object, name,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             NULL);
        break;
    case 4:
        result = Python_PyObject_CallMethodObjArgs
            (object, name,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             pyml_unwrap(Field(arguments_ocaml, 3)),
             NULL);
        break;
    case 5:
        result = Python_PyObject_CallMethodObjArgs
            (object, name,
             pyml_unwrap(Field(arguments_ocaml, 0)),
             pyml_unwrap(Field(arguments_ocaml, 1)),
             pyml_unwrap(Field(arguments_ocaml, 2)),
             pyml_unwrap(Field(arguments_ocaml, 3)),
             pyml_unwrap(Field(arguments_ocaml, 4)),
             NULL);
        break;
    default:
        fprintf(stderr,
                "PyObject_CallMethodObjArgs_wrapper not implemented for more "
                "than 5 arguments\n");
        exit(EXIT_FAILURE);
    }

    CAMLreturn(pyml_wrap(result, true));
}

CAMLprim value
pyml_capsule_check(value v)
{
    CAMLparam1(v);
    pyml_assert_initialized();
    PyObject *o = getcustom(v);
    PyObject *ob_type = pyobjectdescr(o)->ob_type;
    int check_result = ob_type == Python_PyCapsule_Type;
    CAMLreturn(Val_int(check_result));
}

CAMLprim value
pyml_wrap_value(value v)
{
    CAMLparam1(v);
    pyml_assert_initialized();
    PyObject *result = camlwrap_capsule(v, NULL, 0);
    CAMLreturn(pyml_wrap(result, true));
}

CAMLprim value
pyml_unwrap_value(value x_ocaml)
{
    CAMLparam1(x_ocaml);
    CAMLlocal1(v);
    pyml_assert_initialized();
    PyObject *x = pyml_unwrap(x_ocaml);
    void *p = unwrap_capsule(x, "ocaml-capsule");
    if (!p) {
        fprintf(stderr, "pyml_unwrap_value: type mismatch");
        exit(EXIT_FAILURE);
    }
    v = *(value *) p;
    CAMLreturn(v);
}

CAMLprim value
PyErr_Fetch_wrapper(value unit)
{
    CAMLparam1(unit);
    CAMLlocal1(result);
    pyml_assert_initialized();
    PyObject *excType, *excValue, *excTraceback;
    Python_PyErr_Fetch(&excType, &excValue, &excTraceback);
    Python_PyErr_NormalizeException(&excType, &excValue, &excTraceback);
    result = caml_alloc_tuple(3);
    Store_field(result, 0, pyml_wrap(excType, false));
    Store_field(result, 1, pyml_wrap(excValue, false));
    Store_field(result, 2, pyml_wrap(excTraceback, false));
    CAMLreturn(result);
}

CAMLprim value
pyml_wrap_string_option(const char *s)
{
    CAMLparam0();
    CAMLlocal1(result);
    if (!s) {
        CAMLreturn(Val_int(0));
    }
    result = caml_alloc_tuple(1);
    Store_field(result, 0, caml_copy_string(s));
    CAMLreturn(result);
}

CAMLprim value
pyrefcount(value pyobj)
{
    CAMLparam1(pyobj);
    PyObject *obj = pyml_unwrap(pyobj);
    CAMLreturn(Val_int(pyobjectdescr(obj)->ob_refcnt));
}

static value
pyml_wrap_wide_string(wchar_t *ws)
{
    CAMLparam0();
    CAMLlocal1(result);
    size_t n = wcstombs(NULL, ws, 0);
    if (n == (size_t) -1) {
        fprintf(stderr, "pyml_wrap_wide_string failure.\n");
        exit(EXIT_FAILURE);
    }
    char *s = xmalloc((n + 1) * sizeof (char));
    wcstombs(s, ws, n);
    result = caml_copy_string(s);
    free(s);
    CAMLreturn(result);
}

static wchar_t *
wide_string_of_string(const char *s)
{
    size_t n = mbstowcs(NULL, s, 0);
    if (n == (size_t) -1) {
        fprintf(stderr, "wide_string_of_string failure.\n");
        exit(EXIT_FAILURE);
    }
    wchar_t *ws = xmalloc((n + 1) * sizeof (wchar_t));
    mbstowcs(ws, s, n);
    return ws;
}

static wchar_t *
pyml_unwrap_wide_string(value string_ocaml)
{
    CAMLparam1(string_ocaml);
    wchar_t *ws = wide_string_of_string(String_val(string_ocaml));
    CAMLreturnT(wchar_t *, ws);
}

static int16_t *
pyml_unwrap_ucs2(value array_ocaml)
{
    CAMLparam1(array_ocaml);
    mlsize_t len = Wosize_val(array_ocaml);
    int16_t *result = xmalloc(len * sizeof(int16_t));
    size_t i;
    for (i = 0; i < len; i++) {
        result[i] = Field(array_ocaml, i);
    }
    CAMLreturnT(int16_t *, result);
}

static int32_t *
pyml_unwrap_ucs4(value array_ocaml)
{
    CAMLparam1(array_ocaml);
    mlsize_t len = Wosize_val(array_ocaml);
    int32_t *result = xmalloc(len * sizeof(int32_t));
    size_t i;
    for (i = 0; i < len; i++) {
        result[i] = Field(array_ocaml, i);
    }
    CAMLreturnT(int32_t *, result);
}

static value
pyml_wrap_ucs2_option(int16_t *buffer)
{
    CAMLparam0();
    CAMLlocal2(result, array);
    mlsize_t len;
    if (buffer == NULL) {
        CAMLreturn(Val_int(0));
    }
    len = 0;
    while (buffer[len]) {
        len++;
    }
    array = caml_alloc_tuple(len);
    size_t i;
    for (i = 0; i < len; i++) {
        Store_field(array, i, buffer[i]);
    }
    result = caml_alloc_tuple(1);
    Store_field(result, 0, array);
    CAMLreturn(result);
}

static value
pyml_wrap_ucs4_option_and_free(int32_t *buffer, bool free)
{
    CAMLparam0();
    CAMLlocal2(result, array);
    mlsize_t len;
    if (buffer == NULL) {
        CAMLreturn(Val_int(0));
    }
    len = 0;
    while (buffer[len]) {
        len++;
    }
    array = caml_alloc_tuple(len);
    size_t i;
    for (i = 0; i < len; i++) {
        Store_field(array, i, buffer[i]);
    }
    result = caml_alloc_tuple(1);
    Store_field(result, 0, array);
    if (free) {
        Python_PyMem_Free(buffer);
    }
    CAMLreturn(result);
}

#define StringAndSize_wrapper(func, byte_type)                          \
    CAMLprim value                                                      \
    func##_wrapper(value arg_ocaml)                                     \
    {                                                                   \
        CAMLparam1(arg_ocaml);                                          \
        CAMLlocal2(result, string);                                     \
        PyObject *arg = pyml_unwrap(arg_ocaml);                         \
        byte_type *buffer;                                              \
        Py_ssize_t length;                                              \
        int return_value;                                               \
        return_value = Python_##func(arg, &buffer, &length);            \
        if (return_value == -1) {                                       \
            CAMLreturn(Val_int(0));                                     \
        }                                                               \
        string = caml_alloc_initialized_string(length, buffer);         \
        result = caml_alloc_tuple(1);                                   \
        Store_field(result, 0, string);                                 \
        CAMLreturn(result);                                             \
    }

StringAndSize_wrapper(PyString_AsStringAndSize, char);
StringAndSize_wrapper(PyObject_AsCharBuffer, const char);
StringAndSize_wrapper(PyObject_AsReadBuffer, const void);
StringAndSize_wrapper(PyObject_AsWriteBuffer, void);

static FILE *
open_file(value file, const char *mode)
{
    CAMLparam1(file);
    FILE *result;
    if (Tag_val(file) == 0) {
        const char *filename = String_val(Field(file, 0));
        if (Python__Py_fopen != NULL) {
            result = Python__Py_fopen(filename, mode);
        }
        else if (Python__Py_wfopen != NULL) {
            wchar_t *wide_filename = wide_string_of_string(filename);
            result = Python__Py_wfopen(wide_filename, mode);
            free(wide_filename);
        }
        else {
            result = fopen(filename, mode);
        }
    }
    else {
        result = file_of_file_descr(Field(file, 0), mode);
    }
    CAMLreturnT(FILE *, result);
}

static void
close_file(value file, FILE *file_struct)
{
    CAMLparam1(file);
    fclose(file_struct);
    CAMLreturn0;
}

/* Numpy */

void **
pyml_get_pyarray_api(PyObject *c_api)
{
    if (version_major >= 3) {
        return (void **)Python27_PyCapsule_GetPointer(c_api, NULL);
    }
    else {
        return (void **)Python2_PyCObject_AsVoidPtr(c_api);
    }
}

CAMLprim value
get_pyarray_type(value numpy_api_ocaml)
{
    CAMLparam1(numpy_api_ocaml);
    PyObject *c_api = pyml_unwrap(numpy_api_ocaml);
    void **PyArray_API = pyml_get_pyarray_api(c_api);
    PyObject *result = PyArray_API[2];
    CAMLreturn(pyml_wrap(result, true));
}

CAMLprim value
pyarray_of_floatarray_wrapper(
    value numpy_api_ocaml, value array_type_ocaml, value array_ocaml)
{
    CAMLparam3(numpy_api_ocaml, array_type_ocaml, array_ocaml);
    pyml_assert_initialized();
    PyObject *c_api = pyml_unwrap(numpy_api_ocaml);
    void **PyArray_API = pyml_get_pyarray_api(c_api);
    PyObject *(*PyArray_New)
        (PyTypeObject *, int, npy_intp *, int, npy_intp *, void *, int, int,
         PyObject *) = PyArray_API[93];
    npy_intp length = Wosize_val(array_ocaml);
    void *data = (double *) array_ocaml;
    PyTypeObject (*PyArray_SubType) =
        (PyTypeObject *) pyml_unwrap(array_type_ocaml);
    PyObject *result = PyArray_New(
        PyArray_SubType, 1, &length, NPY_DOUBLE, NULL, data, 0,
        NPY_ARRAY_CARRAY, NULL);
    CAMLreturn(pyml_wrap(result, true));
}

CAMLprim value
pyarray_move_floatarray_wrapper(value numpy_array_ocaml, value array_ocaml)
{
    CAMLparam2(numpy_array_ocaml, array_ocaml);
    pyml_assert_initialized();
    PyObject *numpy_array = pyml_unwrap(numpy_array_ocaml);
    PyArrayObject_fields *fields =
      (PyArrayObject_fields *) pyobjectdescr(numpy_array);
    fields->data = (void *) array_ocaml;
    CAMLreturn(Val_unit);
}

CAMLprim value
PyLong_FromString_wrapper(value str_ocaml, value base_ocaml)
{
    CAMLparam2(str_ocaml, base_ocaml);
    CAMLlocal1(result);
    pyml_assert_initialized();
    const char *str = String_val(str_ocaml);
    const char *pend;
    int base = Int_val(base_ocaml);
    PyObject *l = Python_PyLong_FromString(str, &pend, base);
    ssize_t len = pend - str;
    result = caml_alloc_tuple(2);
    Store_field(result, 0, pyml_wrap(l, true));
    Store_field(result, 1, Val_int(len));
    CAMLreturn(result);
}

CAMLprim value
Python27_PyCapsule_IsValid_wrapper(value arg0_ocaml, value arg1_ocaml)
{
    CAMLparam2(arg0_ocaml, arg1_ocaml);

    pyml_assert_initialized();
    if (!Python27_PyCapsule_IsValid) {
        failwith("PyCapsule_IsValid is only available in Python >2.7");
    }
    PyObject *arg0 = pyml_unwrap(arg0_ocaml);
    const char *arg1 = String_val(arg1_ocaml);
    int result = Python27_PyCapsule_IsValid(arg0, arg1);
    CAMLreturn(Val_int(result));
}

#include "pyml_wrappers.inc"
