/*

 * diffhelpers.c - helper routines for mpatch

 *

 * Copyright 2007 Chris Mason <chris.mason@oracle.com>

 *

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

 * of the GNU General Public License v2, incorporated herein by reference.

 */

#include <Python.h>

#include <stdlib.h>

#include <string.h>

static char diffhelpers_doc[] = "Efficient diff parsing";

static PyObject *diffhelpers_Error;

/* fixup the last lines of a and b when the patch has no newline at eof */

static void _fix_newline(PyObject *hunk, PyObject *a, PyObject *b)

{

	int hunksz = PyList_Size(hunk);

	PyObject *s = PyList_GET_ITEM(hunk, hunksz-1);

	char *l = PyString_AS_STRING(s);

	int sz = PyString_GET_SIZE(s);

	int alen = PyList_Size(a);

	int blen = PyList_Size(b);

	char c = l[0];

	PyObject *hline = PyString_FromStringAndSize(l, sz-1);

	if (c == ' ' || c == '+') {

		PyObject *rline = PyString_FromStringAndSize(l+1, sz-2);

		PyList_SetItem(b, blen-1, rline);

	}

	if (c == ' ' || c == '-') {

		Py_INCREF(hline);

		PyList_SetItem(a, alen-1, hline);

	}

	PyList_SetItem(hunk, hunksz-1, hline);

}

/* python callable form of _fix_newline */

static PyObject *

fix_newline(PyObject *self, PyObject *args)

{

	PyObject *hunk, *a, *b;

	if (!PyArg_ParseTuple(args, "OOO", &hunk, &a, &b))

		return NULL;

	_fix_newline(hunk, a, b);

	return Py_BuildValue("l", 0);

}

/*

 * read lines from fp into the hunk.  The hunk is parsed into two arrays

 * a and b.  a gets the old state of the text, b gets the new state

 * The control char from the hunk is saved when inserting into a, but not b

 * (for performance while deleting files)

 */

static PyObject *

addlines(PyObject *self, PyObject *args)

{

	PyObject *fp, *hunk, *a, *b, *x;

	int i;

	int lena, lenb;

	int num;

	int todoa, todob;

	char *s, c;

	PyObject *l;

	if (!PyArg_ParseTuple(args, "OOiiOO", &fp, &hunk, &lena, &lenb, &a, &b))

		return NULL;

	while(1) {

		todoa = lena - PyList_Size(a);

		todob = lenb - PyList_Size(b);

		num = todoa > todob ? todoa : todob;

		if (num == 0)

		    break;

		for (i = 0 ; i < num ; i++) {

			x = PyFile_GetLine(fp, 0);

			s = PyString_AS_STRING(x);

			c = *s;

			if (strcmp(s, "\\ No newline at end of file\n") == 0) {

				_fix_newline(hunk, a, b);

				continue;

			}

			if (c == '\n') {

				/* Some patches may be missing the control char

				 * on empty lines. Supply a leading space. */

				Py_DECREF(x);

				x = PyString_FromString(" \n");

			}

			PyList_Append(hunk, x);

			if (c == '+') {

				l = PyString_FromString(s + 1);

				PyList_Append(b, l);

				Py_DECREF(l);

			} else if (c == '-') {

				PyList_Append(a, x);

			} else {

				l = PyString_FromString(s + 1);

				PyList_Append(b, l);

				Py_DECREF(l);

				PyList_Append(a, x);

			}

			Py_DECREF(x);

		}

	}

	return Py_BuildValue("l", 0);

}

/*

 * compare the lines in a with the lines in b.  a is assumed to have

 * a control char at the start of each line, this char is ignored in the

 * compare

 */

static PyObject *

testhunk(PyObject *self, PyObject *args)

{

	PyObject *a, *b;

	long bstart;

	int alen, blen;

	int i;

	char *sa, *sb;

	if (!PyArg_ParseTuple(args, "OOl", &a, &b, &bstart))

		return NULL;

	alen = PyList_Size(a);

	blen = PyList_Size(b);

	if (alen > blen - bstart) {

		return Py_BuildValue("l", -1);

	}

	for (i = 0 ; i < alen ; i++) {

		sa = PyString_AS_STRING(PyList_GET_ITEM(a, i));

		sb = PyString_AS_STRING(PyList_GET_ITEM(b, i + bstart));

		if (strcmp(sa+1, sb) != 0)

			return Py_BuildValue("l", -1);

	}

	return Py_BuildValue("l", 0);

}

static PyMethodDef methods[] = {

	{"addlines", addlines, METH_VARARGS, "add lines to a hunk\n"},

	{"fix_newline", fix_newline, METH_VARARGS, "fixup newline counters\n"},

	{"testhunk", testhunk, METH_VARARGS, "test lines in a hunk\n"},

	{NULL, NULL}

};

PyMODINIT_FUNC

initdiffhelpers(void)

{

	Py_InitModule3("diffhelpers", methods, diffhelpers_doc);

	diffhelpers_Error = PyErr_NewException("diffhelpers.diffhelpersError",

	                                        NULL, NULL);

}