/**
 * Copyright (c) 2016-present, Gregory Szorc
 * All rights reserved.
 *
 * This software may be modified and distributed under the terms
 * of the BSD license. See the LICENSE file for details.
 */

#include "python-zstandard.h"

extern PyObject *ZstdError;

static void DecompressionObj_dealloc(ZstdDecompressionObj *self) {
    Py_XDECREF(self->decompressor);
    Py_CLEAR(self->unused_data);

    PyObject_Del(self);
}

static PyObject *DecompressionObj_decompress(ZstdDecompressionObj *self,
                                             PyObject *args, PyObject *kwargs) {
    static char *kwlist[] = {"data", NULL};

    Py_buffer source;
    size_t zresult;
    ZSTD_inBuffer input;
    ZSTD_outBuffer output;
    PyObject *result = NULL;
    Py_ssize_t resultSize = 0;

    output.dst = NULL;

    if (self->finished) {
        PyErr_SetString(ZstdError, "cannot use a decompressobj multiple times");
        return NULL;
    }

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "y*:decompress", kwlist,
                                     &source)) {
        return NULL;
    }

    /* Special case of empty input. Output will always be empty. */
    if (source.len == 0) {
        result = PyBytes_FromString("");
        goto finally;
    }

    input.src = source.buf;
    input.size = source.len;
    input.pos = 0;

    output.dst = PyMem_Malloc(self->outSize);
    if (!output.dst) {
        PyErr_NoMemory();
        goto except;
    }
    output.size = self->outSize;
    output.pos = 0;

    while (1) {
        Py_BEGIN_ALLOW_THREADS zresult =
            ZSTD_decompressStream(self->decompressor->dctx, &output, &input);
        Py_END_ALLOW_THREADS

        if (ZSTD_isError(zresult)) {
            PyErr_Format(ZstdError, "zstd decompressor error: %s",
                         ZSTD_getErrorName(zresult));
            goto except;
        }

        if (output.pos) {
            if (result) {
                resultSize = PyBytes_GET_SIZE(result);
                if (-1 ==
                    safe_pybytes_resize(&result, resultSize + output.pos)) {
                    Py_XDECREF(result);
                    goto except;
                }

                memcpy(PyBytes_AS_STRING(result) + resultSize, output.dst,
                       output.pos);
            }
            else {
                result = PyBytes_FromStringAndSize(output.dst, output.pos);
                if (!result) {
                    goto except;
                }
            }
        }

        if (0 == zresult && !self->readAcrossFrames) {
            self->finished = 1;

            /* We should only get here at most once. */
            assert(!self->unused_data);
            self->unused_data = PyBytes_FromStringAndSize((char *)(input.src) + input.pos, input.size - input.pos);

            break;
        }
        else if (0 == zresult && self->readAcrossFrames) {
            if (input.pos == input.size) {
                break;
            } else {
                output.pos = 0;
            }
        }
        else if (input.pos == input.size && output.pos == 0) {
            break;
        }
        else {
            output.pos = 0;
        }
    }

    if (!result) {
        result = PyBytes_FromString("");
    }

    goto finally;

except:
    Py_CLEAR(result);

finally:
    PyMem_Free(output.dst);
    PyBuffer_Release(&source);

    return result;
}

static PyObject *DecompressionObj_flush(ZstdDecompressionObj *self,
                                        PyObject *args, PyObject *kwargs) {
    static char *kwlist[] = {"length", NULL};

    PyObject *length = NULL;

    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O:flush", kwlist,
                                     &length)) {
        return NULL;
    }

    return PyBytes_FromString("");
}

static PyObject *DecompressionObj_unused_data(PyObject *self, void *unused) {
    ZstdDecompressionObj *slf = (ZstdDecompressionObj *)(self);

    if (slf->unused_data) {
        Py_INCREF(slf->unused_data);
        return slf->unused_data;
    } else {
        return PyBytes_FromString("");
    }
}

static PyObject *DecompressionObj_unconsumed_tail(PyObject *self, void *unused) {
    return PyBytes_FromString("");
}

static PyObject *DecompressionObj_eof(PyObject *self, void *unused) {
    ZstdDecompressionObj *slf = (ZstdDecompressionObj*)(self);

    if (slf->finished) {
        Py_RETURN_TRUE;
    } else {
        Py_RETURN_FALSE;
    }
}

static PyMethodDef DecompressionObj_methods[] = {
    {"decompress", (PyCFunction)DecompressionObj_decompress,
     METH_VARARGS | METH_KEYWORDS, PyDoc_STR("decompress data")},
    {"flush", (PyCFunction)DecompressionObj_flush, METH_VARARGS | METH_KEYWORDS,
     PyDoc_STR("no-op")},
    {NULL, NULL}};

static PyGetSetDef DecompressionObj_getset[] = {
    {"unused_data", DecompressionObj_unused_data, NULL, NULL, NULL },
    {"unconsumed_tail", DecompressionObj_unconsumed_tail, NULL, NULL, NULL },
    {"eof", DecompressionObj_eof, NULL, NULL, NULL },
    {NULL}};

PyType_Slot ZstdDecompressionObjSlots[] = {
    {Py_tp_dealloc, DecompressionObj_dealloc},
    {Py_tp_methods, DecompressionObj_methods},
    {Py_tp_getset, DecompressionObj_getset},
    {Py_tp_new, PyType_GenericNew},
    {0, NULL},
};

PyType_Spec ZstdDecompressionObjSpec = {
    "zstd.ZstdDecompressionObj",
    sizeof(ZstdDecompressionObj),
    0,
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    ZstdDecompressionObjSlots,
};

PyTypeObject *ZstdDecompressionObjType;

void decompressobj_module_init(PyObject *module) {
    ZstdDecompressionObjType =
        (PyTypeObject *)PyType_FromSpec(&ZstdDecompressionObjSpec);
    if (PyType_Ready(ZstdDecompressionObjType) < 0) {
        return;
    }
}