/**

* Copyright (c) 2017-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 set_unsupported_operation(void) {

	PyObject* iomod;

	PyObject* exc;

	iomod = PyImport_ImportModule("io");

	if (NULL == iomod) {

		return;

	}

	exc = PyObject_GetAttrString(iomod, "UnsupportedOperation");

	if (NULL == exc) {

		Py_DECREF(iomod);

		return;

	}

	PyErr_SetNone(exc);

	Py_DECREF(exc);

	Py_DECREF(iomod);

}

static void reader_dealloc(ZstdCompressionReader* self) {

	Py_XDECREF(self->compressor);

	Py_XDECREF(self->reader);

	if (self->buffer.buf) {

		PyBuffer_Release(&self->buffer);

		memset(&self->buffer, 0, sizeof(self->buffer));

	}

	PyObject_Del(self);

}

static ZstdCompressionReader* reader_enter(ZstdCompressionReader* self) {

	size_t zresult;

	if (self->entered) {

		PyErr_SetString(PyExc_ValueError, "cannot __enter__ multiple times");

		return NULL;

	}

	zresult = ZSTD_CCtx_setPledgedSrcSize(self->compressor->cctx, self->sourceSize);

	if (ZSTD_isError(zresult)) {

		PyErr_Format(ZstdError, "error setting source size: %s",

			ZSTD_getErrorName(zresult));

		return NULL;

	}

	self->entered = 1;

	Py_INCREF(self);

	return self;

}

static PyObject* reader_exit(ZstdCompressionReader* self, PyObject* args) {

	PyObject* exc_type;

	PyObject* exc_value;

	PyObject* exc_tb;

	if (!PyArg_ParseTuple(args, "OOO:__exit__", &exc_type, &exc_value, &exc_tb)) {

		return NULL;

	}

	self->entered = 0;

	self->closed = 1;

	/* Release resources associated with source. */

	Py_CLEAR(self->reader);

	if (self->buffer.buf) {

		PyBuffer_Release(&self->buffer);

		memset(&self->buffer, 0, sizeof(self->buffer));

	}

    Py_CLEAR(self->compressor);

	Py_RETURN_FALSE;

}

static PyObject* reader_readable(ZstdCompressionReader* self) {

	Py_RETURN_TRUE;

}

static PyObject* reader_writable(ZstdCompressionReader* self) {

	Py_RETURN_FALSE;

}

static PyObject* reader_seekable(ZstdCompressionReader* self) {

	Py_RETURN_FALSE;

}

static PyObject* reader_readline(PyObject* self, PyObject* args) {

	set_unsupported_operation();

	return NULL;

}

static PyObject* reader_readlines(PyObject* self, PyObject* args) {

	set_unsupported_operation();

	return NULL;

}

static PyObject* reader_write(PyObject* self, PyObject* args) {

	PyErr_SetString(PyExc_OSError, "stream is not writable");

	return NULL;

}

static PyObject* reader_writelines(PyObject* self, PyObject* args) {

	PyErr_SetString(PyExc_OSError, "stream is not writable");

	return NULL;

}

static PyObject* reader_isatty(PyObject* self) {

	Py_RETURN_FALSE;

}

static PyObject* reader_flush(PyObject* self) {

	Py_RETURN_NONE;

}

static PyObject* reader_close(ZstdCompressionReader* self) {

	self->closed = 1;

	Py_RETURN_NONE;

}

static PyObject* reader_closed(ZstdCompressionReader* self) {

	if (self->closed) {

		Py_RETURN_TRUE;

	}

	else {

		Py_RETURN_FALSE;

	}

}

static PyObject* reader_tell(ZstdCompressionReader* self) {

	/* TODO should this raise OSError since stream isn't seekable? */

	return PyLong_FromUnsignedLongLong(self->bytesCompressed);

}

static PyObject* reader_read(ZstdCompressionReader* self, PyObject* args, PyObject* kwargs) {

	static char* kwlist[] = {

		"size",

		NULL

	};

	Py_ssize_t size = -1;

	PyObject* result = NULL;

	char* resultBuffer;

	Py_ssize_t resultSize;

	size_t zresult;

	size_t oldPos;

	if (!self->entered) {

		PyErr_SetString(ZstdError, "read() must be called from an active context manager");

		return NULL;

	}

	if (self->closed) {

		PyErr_SetString(PyExc_ValueError, "stream is closed");

		return NULL;

	}

	if (self->finishedOutput) {

		return PyBytes_FromStringAndSize("", 0);

	}

	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "n", kwlist, &size)) {

		return NULL;

	}

	if (size < 1) {

		PyErr_SetString(PyExc_ValueError, "cannot read negative or size 0 amounts");

		return NULL;

	}

	result = PyBytes_FromStringAndSize(NULL, size);

	if (NULL == result) {

		return NULL;

	}

	PyBytes_AsStringAndSize(result, &resultBuffer, &resultSize);

	self->output.dst = resultBuffer;

	self->output.size = resultSize;

	self->output.pos = 0;

readinput:

	/* If we have data left over, consume it. */

	if (self->input.pos < self->input.size) {

		oldPos = self->output.pos;

		Py_BEGIN_ALLOW_THREADS

		zresult = ZSTD_compress_generic(self->compressor->cctx,

			&self->output, &self->input, ZSTD_e_continue);

		Py_END_ALLOW_THREADS

		self->bytesCompressed += self->output.pos - oldPos;

		/* Input exhausted. Clear out state tracking. */

		if (self->input.pos == self->input.size) {

			memset(&self->input, 0, sizeof(self->input));

			Py_CLEAR(self->readResult);

			if (self->buffer.buf) {

				self->finishedInput = 1;

			}

		}

		if (ZSTD_isError(zresult)) {

			PyErr_Format(ZstdError, "zstd compress error: %s", ZSTD_getErrorName(zresult));

			return NULL;

		}

		if (self->output.pos) {

			/* If no more room in output, emit it. */

			if (self->output.pos == self->output.size) {

				memset(&self->output, 0, sizeof(self->output));

				return result;

			}

			/*

			 * There is room in the output. We fall through to below, which will either

			 * get more input for us or will attempt to end the stream.

			 */

		}

		/* Fall through to gather more input. */

	}

	if (!self->finishedInput) {

		if (self->reader) {

			Py_buffer buffer;

			assert(self->readResult == NULL);

			self->readResult = PyObject_CallMethod(self->reader, "read",

				"k", self->readSize);

			if (self->readResult == NULL) {

				return NULL;

			}

			memset(&buffer, 0, sizeof(buffer));

			if (0 != PyObject_GetBuffer(self->readResult, &buffer, PyBUF_CONTIG_RO)) {

				return NULL;

			}

			/* EOF */

			if (0 == buffer.len) {

				self->finishedInput = 1;

				Py_CLEAR(self->readResult);

			}

			else {

				self->input.src = buffer.buf;

				self->input.size = buffer.len;

				self->input.pos = 0;

			}

			PyBuffer_Release(&buffer);

		}

		else {

			assert(self->buffer.buf);

			self->input.src = self->buffer.buf;

			self->input.size = self->buffer.len;

			self->input.pos = 0;

		}

	}

	if (self->input.size) {

		goto readinput;

	}

	/* Else EOF */

	oldPos = self->output.pos;

	zresult = ZSTD_compress_generic(self->compressor->cctx, &self->output,

		&self->input, ZSTD_e_end);

	self->bytesCompressed += self->output.pos - oldPos;

	if (ZSTD_isError(zresult)) {

		PyErr_Format(ZstdError, "error ending compression stream: %s",

			ZSTD_getErrorName(zresult));

		return NULL;

	}

	assert(self->output.pos);

	if (0 == zresult) {

		self->finishedOutput = 1;

	}

	if (safe_pybytes_resize(&result, self->output.pos)) {

		Py_XDECREF(result);

		return NULL;

	}

	memset(&self->output, 0, sizeof(self->output));

	return result;

}

static PyObject* reader_readall(PyObject* self) {

	PyErr_SetNone(PyExc_NotImplementedError);

	return NULL;

}

static PyObject* reader_iter(PyObject* self) {

	set_unsupported_operation();

	return NULL;

}

static PyObject* reader_iternext(PyObject* self) {

	set_unsupported_operation();

	return NULL;

}

static PyMethodDef reader_methods[] = {

	{ "__enter__", (PyCFunction)reader_enter, METH_NOARGS,

	PyDoc_STR("Enter a compression context") },

	{ "__exit__", (PyCFunction)reader_exit, METH_VARARGS,

	PyDoc_STR("Exit a compression context") },

	{ "close", (PyCFunction)reader_close, METH_NOARGS,

	PyDoc_STR("Close the stream so it cannot perform any more operations") },

	{ "closed", (PyCFunction)reader_closed, METH_NOARGS,

	PyDoc_STR("Whether stream is closed") },

	{ "flush", (PyCFunction)reader_flush, METH_NOARGS, PyDoc_STR("no-ops") },

	{ "isatty", (PyCFunction)reader_isatty, METH_NOARGS, PyDoc_STR("Returns False") },

	{ "readable", (PyCFunction)reader_readable, METH_NOARGS,

	PyDoc_STR("Returns True") },

	{ "read", (PyCFunction)reader_read, METH_VARARGS | METH_KEYWORDS, PyDoc_STR("read compressed data") },

	{ "readall", (PyCFunction)reader_readall, METH_NOARGS, PyDoc_STR("Not implemented") },

	{ "readline", (PyCFunction)reader_readline, METH_VARARGS, PyDoc_STR("Not implemented") },

	{ "readlines", (PyCFunction)reader_readlines, METH_VARARGS, PyDoc_STR("Not implemented") },

	{ "seekable", (PyCFunction)reader_seekable, METH_NOARGS,

	PyDoc_STR("Returns False") },

	{ "tell", (PyCFunction)reader_tell, METH_NOARGS,

	PyDoc_STR("Returns current number of bytes compressed") },

	{ "writable", (PyCFunction)reader_writable, METH_NOARGS,

	PyDoc_STR("Returns False") },

	{ "write", reader_write, METH_VARARGS, PyDoc_STR("Raises OSError") },

	{ "writelines", reader_writelines, METH_VARARGS, PyDoc_STR("Not implemented") },

	{ NULL, NULL }

};

PyTypeObject ZstdCompressionReaderType = {

	PyVarObject_HEAD_INIT(NULL, 0)

	"zstd.ZstdCompressionReader", /* tp_name */

	sizeof(ZstdCompressionReader), /* tp_basicsize */

	0, /* tp_itemsize */

	(destructor)reader_dealloc, /* tp_dealloc */

	0, /* tp_print */

	0, /* tp_getattr */

	0, /* tp_setattr */

	0, /* tp_compare */

	0, /* tp_repr */

	0, /* tp_as_number */

	0, /* tp_as_sequence */

	0, /* tp_as_mapping */

	0, /* tp_hash */

	0, /* tp_call */

	0, /* tp_str */

	0, /* tp_getattro */

	0, /* tp_setattro */

	0, /* tp_as_buffer */

	Py_TPFLAGS_DEFAULT, /* tp_flags */

	0, /* tp_doc */

	0, /* tp_traverse */

	0, /* tp_clear */

	0, /* tp_richcompare */

	0, /* tp_weaklistoffset */

	reader_iter, /* tp_iter */

	reader_iternext, /* tp_iternext */

	reader_methods, /* tp_methods */

	0, /* tp_members */

	0, /* tp_getset */

	0, /* tp_base */

	0, /* tp_dict */

	0, /* tp_descr_get */

	0, /* tp_descr_set */

	0, /* tp_dictoffset */

	0, /* tp_init */

	0, /* tp_alloc */

	PyType_GenericNew, /* tp_new */

};

void compressionreader_module_init(PyObject* mod) {

	/* TODO make reader a sub-class of io.RawIOBase */

	Py_TYPE(&ZstdCompressionReaderType) = &PyType_Type;

	if (PyType_Ready(&ZstdCompressionReaderType) < 0) {

		return;

	}

}