/*

 bdiff.c - efficient binary diff extension for Mercurial

 Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>

 This software may be used and distributed according to the terms of

 the GNU General Public License, incorporated herein by reference.

 Based roughly on Python difflib

*/

#define PY_SSIZE_T_CLEAN

#include <Python.h>

#include <limits.h>

#include <stdlib.h>

#include <string.h>

#include "bdiff.h"

#include "bitmanipulation.h"

#include "util.h"

static PyObject *blocks(PyObject *self, PyObject *args)

{

	PyObject *sa, *sb, *rl = NULL, *m;

	struct bdiff_line *a, *b;

	struct bdiff_hunk l, *h;

	int an, bn, count, pos = 0;

	l.next = NULL;

	if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb))

		return NULL;

	an = bdiff_splitlines(PyBytes_AsString(sa), PyBytes_Size(sa), &a);

	bn = bdiff_splitlines(PyBytes_AsString(sb), PyBytes_Size(sb), &b);

	if (!a || !b)

		goto nomem;

	count = bdiff_diff(a, an, b, bn, &l);

	if (count < 0)

		goto nomem;

	rl = PyList_New(count);

	if (!rl)

		goto nomem;

	for (h = l.next; h; h = h->next) {

		m = Py_BuildValue("iiii", h->a1, h->a2, h->b1, h->b2);

		PyList_SetItem(rl, pos, m);

		pos++;

	}

nomem:

	free(a);

	free(b);

	bdiff_freehunks(l.next);

	return rl ? rl : PyErr_NoMemory();

}

static PyObject *bdiff(PyObject *self, PyObject *args)

{

	char *sa, *sb, *rb, *ia, *ib;

	PyObject *result = NULL;

	struct bdiff_line *al, *bl;

	struct bdiff_hunk l, *h;

	int an, bn, count;

	Py_ssize_t len = 0, la, lb, li = 0, lcommon = 0, lmax;

	PyThreadState *_save;

	l.next = NULL;

	if (!PyArg_ParseTuple(args, "s#s#:bdiff", &sa, &la, &sb, &lb))

		return NULL;

	if (la > UINT_MAX || lb > UINT_MAX) {

		PyErr_SetString(PyExc_ValueError, "bdiff inputs too large");

		return NULL;

	}

	_save = PyEval_SaveThread();

	lmax = la > lb ? lb : la;

	for (ia = sa, ib = sb;

	     li < lmax && *ia == *ib;

	     ++li, ++ia, ++ib)

		if (*ia == '\n')

			lcommon = li + 1;

	/* we can almost add: if (li == lmax) lcommon = li; */

	an = bdiff_splitlines(sa + lcommon, la - lcommon, &al);

	bn = bdiff_splitlines(sb + lcommon, lb - lcommon, &bl);

	if (!al || !bl)

		goto nomem;

	count = bdiff_diff(al, an, bl, bn, &l);

	if (count < 0)

		goto nomem;

	/* calculate length of output */

	la = lb = 0;

	for (h = l.next; h; h = h->next) {

		if (h->a1 != la || h->b1 != lb)

			len += 12 + bl[h->b1].l - bl[lb].l;

		la = h->a2;

		lb = h->b2;

	}

	PyEval_RestoreThread(_save);

	_save = NULL;

	result = PyBytes_FromStringAndSize(NULL, len);

	if (!result)

		goto nomem;

	/* build binary patch */

	rb = PyBytes_AsString(result);

	la = lb = 0;

	for (h = l.next; h; h = h->next) {

		if (h->a1 != la || h->b1 != lb) {

			len = bl[h->b1].l - bl[lb].l;

			putbe32((uint32_t)(al[la].l + lcommon - al->l), rb);

			putbe32((uint32_t)(al[h->a1].l + lcommon - al->l), rb + 4);

			putbe32((uint32_t)len, rb + 8);

			memcpy(rb + 12, bl[lb].l, len);

			rb += 12 + len;

		}

		la = h->a2;

		lb = h->b2;

	}

nomem:

	if (_save)

		PyEval_RestoreThread(_save);

	free(al);

	free(bl);

	bdiff_freehunks(l.next);

	return result ? result : PyErr_NoMemory();

}

/*

 * If allws != 0, remove all whitespace (' ', \t and \r). Otherwise,

 * reduce whitespace sequences to a single space and trim remaining whitespace

 * from end of lines.

 */

static PyObject *fixws(PyObject *self, PyObject *args)

{

	PyObject *s, *result = NULL;

	char allws, c;

	const char *r;

	Py_ssize_t i, rlen, wlen = 0;

	char *w;

	if (!PyArg_ParseTuple(args, "Sb:fixws", &s, &allws))

		return NULL;

	r = PyBytes_AsString(s);

	rlen = PyBytes_Size(s);

	w = (char *)PyMem_Malloc(rlen ? rlen : 1);

	if (!w)

		goto nomem;

	for (i = 0; i != rlen; i++) {

		c = r[i];

		if (c == ' ' || c == '\t' || c == '\r') {

			if (!allws && (wlen == 0 || w[wlen - 1] != ' '))

				w[wlen++] = ' ';

		} else if (c == '\n' && !allws

			  && wlen > 0 && w[wlen - 1] == ' ') {

			w[wlen - 1] = '\n';

		} else {

			w[wlen++] = c;

		}

	}

	result = PyBytes_FromStringAndSize(w, wlen);

nomem:

	PyMem_Free(w);

	return result ? result : PyErr_NoMemory();

}

static char mdiff_doc[] = "Efficient binary diff.";

static PyMethodDef methods[] = {

	{"bdiff", bdiff, METH_VARARGS, "calculate a binary diff\n"},

	{"blocks", blocks, METH_VARARGS, "find a list of matching lines\n"},

	{"fixws", fixws, METH_VARARGS, "normalize diff whitespaces\n"},

	{NULL, NULL}

};

static const int version = 1;

#ifdef IS_PY3K

static struct PyModuleDef bdiff_module = {

	PyModuleDef_HEAD_INIT,

	"bdiff",

	mdiff_doc,

	-1,

	methods

};

PyMODINIT_FUNC PyInit_bdiff(void)

{

	PyObject *m;

	m = PyModule_Create(&bdiff_module);

	PyModule_AddIntConstant(m, "version", version);

	return m;

}

#else

PyMODINIT_FUNC initbdiff(void)

{

	PyObject *m;

	m = Py_InitModule3("bdiff", methods, mdiff_doc);

	PyModule_AddIntConstant(m, "version", version);

}

#endif