/*

 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)

{

	Py_buffer ba, bb;

	char *rb, *ia, *ib;

	PyObject *result = NULL;

	struct bdiff_line *al = NULL, *bl = NULL;

	struct bdiff_hunk l, *h;

	int an, bn, count;

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

	PyThreadState *_save = NULL;

	l.next = NULL;

	if (!PyArg_ParseTuple(args, PY23("s*s*:bdiff", "y*y*:bdiff"), &ba, &bb))

		return NULL;

	if (!PyBuffer_IsContiguous(&ba, 'C') || ba.ndim > 1) {

		PyErr_SetString(PyExc_ValueError, "bdiff input not contiguous");

		goto cleanup;

	}

	if (!PyBuffer_IsContiguous(&bb, 'C') || bb.ndim > 1) {

		PyErr_SetString(PyExc_ValueError, "bdiff input not contiguous");

		goto cleanup;

	}

	la = ba.len;

	lb = bb.len;

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

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

		goto cleanup;

	}

	_save = PyEval_SaveThread();

	lmax = la > lb ? lb : la;

	for (ia = ba.buf, ib = bb.buf; 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(ba.buf + lcommon, la - lcommon, &al);

	bn = bdiff_splitlines(bb.buf + lcommon, lb - lcommon, &bl);

	if (!al || !bl) {

		PyErr_NoMemory();

		goto cleanup;

	}

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

	if (count < 0) {

		PyErr_NoMemory();

		goto cleanup;

	}

	/* 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 cleanup;

	/* 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;

	}

cleanup:

	if (_save)

		PyEval_RestoreThread(_save);

	PyBuffer_Release(&ba);

	PyBuffer_Release(&bb);

	if (al) {

		free(al);

	}

	if (bl) {

		free(bl);

	}

	if (l.next) {

		bdiff_freehunks(l.next);

	}

	return result;

}

/*

 * 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 bool sliceintolist(PyObject *list, Py_ssize_t destidx,

                          const char *source, Py_ssize_t len)

{

	PyObject *sliced = PyBytes_FromStringAndSize(source, len);

	if (sliced == NULL)

		return false;

	PyList_SET_ITEM(list, destidx, sliced);

	return true;

}

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

{

	const char *text;

	Py_ssize_t nelts = 0, size, i, start = 0;

	PyObject *result = NULL;

	if (!PyArg_ParseTuple(args, PY23("s#", "y#"), &text, &size)) {

		goto abort;

	}

	if (!size) {

		return PyList_New(0);

	}

	/* This loops to size-1 because if the last byte is a newline,

	 * we don't want to perform a split there. */

	for (i = 0; i < size - 1; ++i) {

		if (text[i] == '\n') {

			++nelts;

		}

	}

	if ((result = PyList_New(nelts + 1)) == NULL)

		goto abort;

	nelts = 0;

	for (i = 0; i < size - 1; ++i) {

		if (text[i] == '\n') {

			if (!sliceintolist(result, nelts++, text + start,

			                   i - start + 1))

				goto abort;

			start = i + 1;

		}

	}

	if (!sliceintolist(result, nelts++, text + start, size - start))

		goto abort;

	return result;

abort:

	Py_XDECREF(result);

	return NULL;

}

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"},

    {"splitnewlines", splitnewlines, METH_VARARGS,

     "like str.splitlines, but only split on newlines\n"},

    {NULL, NULL},

};

#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