/*

 *  LibXDiff by Davide Libenzi ( File Differential Library )

 *  Copyright (C) 2003-2006 Davide Libenzi, Johannes E. Schindelin

 *

 *  This library is free software; you can redistribute it and/or

 *  modify it under the terms of the GNU Lesser General Public

 *  License as published by the Free Software Foundation; either

 *  version 2.1 of the License, or (at your option) any later version.

 *

 *  This library is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 *  Lesser General Public License for more details.

 *

 *  You should have received a copy of the GNU Lesser General Public

 *  License along with this library; if not, write to the Free Software

 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 *  Davide Libenzi <davidel@xmailserver.org>

 *

 */

#include "xinclude.h"

#include "common.h"

typedef struct s_xdmerge {

	struct s_xdmerge *next;

	/*

	 * 0 = conflict,

	 * 1 = no conflict, take first,

	 * 2 = no conflict, take second.

	 * 3 = no conflict, take both.

	 */

	int mode;

	/*

	 * These point at the respective postimages.  E.g. <i1,chg1> is

	 * how side #1 wants to change the common ancestor; if there is no

	 * overlap, lines before i1 in the postimage of side #1 appear

	 * in the merge result as a region touched by neither side.

	 */

	long i1, i2;

	long chg1, chg2;

	/*

	 * These point at the preimage; of course there is just one

	 * preimage, that is from the shared common ancestor.

	 */

	long i0;

	long chg0;

} xdmerge_t;

static int xdl_append_merge(xdmerge_t **merge, int mode,

			    long i0, long chg0,

			    long i1, long chg1,

			    long i2, long chg2)

{

	xdmerge_t *m = *merge;

	if (m && (i1 <= m->i1 + m->chg1 || i2 <= m->i2 + m->chg2)) {

		if (mode != m->mode)

			m->mode = 0;

		m->chg0 = i0 + chg0 - m->i0;

		m->chg1 = i1 + chg1 - m->i1;

		m->chg2 = i2 + chg2 - m->i2;

	} else {

		m = xdl_malloc(sizeof(xdmerge_t));

		if (!m)

			return -1;

		m->next = NULL;

		m->mode = mode;

		m->i0 = i0;

		m->chg0 = chg0;

		m->i1 = i1;

		m->chg1 = chg1;

		m->i2 = i2;

		m->chg2 = chg2;

		if (*merge)

			(*merge)->next = m;

		*merge = m;

	}

	return 0;

}

static int xdl_cleanup_merge(xdmerge_t *c)

{

	int count = 0;

	xdmerge_t *next_c;

	/* were there conflicts? */

	for (; c; c = next_c) {

		if (c->mode == 0)

			count++;

		next_c = c->next;

		free(c);

	}

	return count;

}

static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,

		int line_count, long flags)

{

	int i;

	xrecord_t **rec1 = xe1->xdf2.recs + i1;

	xrecord_t **rec2 = xe2->xdf2.recs + i2;

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

		int result = xdl_recmatch(rec1[i]->ptr, rec1[i]->size,

			rec2[i]->ptr, rec2[i]->size, flags);

		if (!result)

			return -1;

	}

	return 0;

}

static int xdl_recs_copy_0(size_t *out, int use_orig, xdfenv_t *xe, int i, int count, int add_nl, char *dest)

{

	xrecord_t **recs;

	size_t size = 0;

	*out = 0;

	recs = (use_orig ? xe->xdf1.recs : xe->xdf2.recs) + i;

	if (count < 1)

		return 0;

	for (i = 0; i < count; ) {

		if (dest)

			memcpy(dest + size, recs[i]->ptr, recs[i]->size);

		GITERR_CHECK_ALLOC_ADD(&size, size, recs[i++]->size);

	}

	if (add_nl) {

		i = recs[count - 1]->size;

		if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {

			if (dest)

				dest[size] = '\n';

			GITERR_CHECK_ALLOC_ADD(&size, size, 1);

		}

	}

	*out = size;

	return 0;

}

static int xdl_recs_copy(size_t *out, xdfenv_t *xe, int i, int count, int add_nl, char *dest)

{

	return xdl_recs_copy_0(out, 0, xe, i, count, add_nl, dest);

}

static int xdl_orig_copy(size_t *out, xdfenv_t *xe, int i, int count, int add_nl, char *dest)

{

	return xdl_recs_copy_0(out, 1, xe, i, count, add_nl, dest);

}

static int fill_conflict_hunk(size_t *out, xdfenv_t *xe1, const char *name1,

			      xdfenv_t *xe2, const char *name2,

			      const char *name3,

			      size_t size, int i, int style,

			      xdmerge_t *m, char *dest, int marker_size)

{

	int marker1_size = (name1 ? (int)strlen(name1) + 1 : 0);

	int marker2_size = (name2 ? (int)strlen(name2) + 1 : 0);

	int marker3_size = (name3 ? (int)strlen(name3) + 1 : 0);

	size_t copied;

	*out = 0;

	if (marker_size <= 0)

		marker_size = DEFAULT_CONFLICT_MARKER_SIZE;

	/* Before conflicting part */

	if (xdl_recs_copy(&copied, xe1, i, m->i1 - i, 0,

			      dest ? dest + size : NULL) < 0)

		return -1;

	GITERR_CHECK_ALLOC_ADD(&size, size, copied);

	if (!dest) {

		GITERR_CHECK_ALLOC_ADD4(&size, size, marker_size, 1, marker1_size);

	} else {

		memset(dest + size, '<', marker_size);

		size += marker_size;

		if (marker1_size) {

			dest[size] = ' ';

			memcpy(dest + size + 1, name1, marker1_size - 1);

			size += marker1_size;

		}

		dest[size++] = '\n';

	}

	/* Postimage from side #1 */

	if (xdl_recs_copy(&copied, xe1, m->i1, m->chg1, 1,

			      dest ? dest + size : NULL) < 0)

		return -1;

	GITERR_CHECK_ALLOC_ADD(&size, size, copied);

	if (style == XDL_MERGE_DIFF3) {

		/* Shared preimage */

		if (!dest) {

			GITERR_CHECK_ALLOC_ADD4(&size, size, marker_size, 1, marker3_size);

		} else {

			memset(dest + size, '|', marker_size);

			size += marker_size;

			if (marker3_size) {

				dest[size] = ' ';

				memcpy(dest + size + 1, name3, marker3_size - 1);

				size += marker3_size;

			}

			dest[size++] = '\n';

		}

		if (xdl_orig_copy(&copied, xe1, m->i0, m->chg0, 1,

				      dest ? dest + size : NULL) < 0)

			return -1;

		GITERR_CHECK_ALLOC_ADD(&size, size, copied);

	}

	if (!dest) {

		GITERR_CHECK_ALLOC_ADD3(&size, size, marker_size, 1);

	} else {

		memset(dest + size, '=', marker_size);

		size += marker_size;

		dest[size++] = '\n';

	}

	/* Postimage from side #2 */

	if (xdl_recs_copy(&copied, xe2, m->i2, m->chg2, 1,

			      dest ? dest + size : NULL) < 0)

		return -1;

	GITERR_CHECK_ALLOC_ADD(&size, size, copied);

	if (!dest) {

		GITERR_CHECK_ALLOC_ADD4(&size, size, marker_size, 1, marker2_size);

	} else {

		memset(dest + size, '>', marker_size);

		size += marker_size;

		if (marker2_size) {

			dest[size] = ' ';

			memcpy(dest + size + 1, name2, marker2_size - 1);

			size += marker2_size;

		}

		dest[size++] = '\n';

	}

	*out = size;

	return 0;

}

static int xdl_fill_merge_buffer(size_t *out,

				 xdfenv_t *xe1, const char *name1,

				 xdfenv_t *xe2, const char *name2,

				 const char *ancestor_name,

				 int favor,

				 xdmerge_t *m, char *dest, int style,

				 int marker_size)

{

	size_t size, copied;

	int i;

	*out = 0;

	for (size = i = 0; m; m = m->next) {

		if (favor && !m->mode)

			m->mode = favor;

		if (m->mode == 0) {

			if (fill_conflict_hunk(&size, xe1, name1, xe2, name2,

						  ancestor_name,

						  size, i, style, m, dest,

						  marker_size) < 0)

				return -1;

		}

		else if (m->mode & 3) {

			/* Before conflicting part */

			if (xdl_recs_copy(&copied, xe1, i, m->i1 - i, 0,

					      dest ? dest + size : NULL) < 0)

				return -1;

			GITERR_CHECK_ALLOC_ADD(&size, size, copied);

			/* Postimage from side #1 */

			if (m->mode & 1) {

				if (xdl_recs_copy(&copied, xe1, m->i1, m->chg1, (m->mode & 2),

						      dest ? dest + size : NULL) < 0)

					return -1;

				GITERR_CHECK_ALLOC_ADD(&size, size, copied);

			}

			/* Postimage from side #2 */

			if (m->mode & 2) {

				if (xdl_recs_copy(&copied, xe2, m->i2, m->chg2, 0,

						      dest ? dest + size : NULL) < 0)

					return -1;

				GITERR_CHECK_ALLOC_ADD(&size, size, copied);

			}

		} else

			continue;

		i = m->i1 + m->chg1;

	}

	if (xdl_recs_copy(&copied, xe1, i, xe1->xdf2.nrec - i, 0,

			      dest ? dest + size : NULL) < 0)

		return -1;

	GITERR_CHECK_ALLOC_ADD(&size, size, copied);

	*out = size;

	return 0;

}

/*

 * Sometimes, changes are not quite identical, but differ in only a few

 * lines. Try hard to show only these few lines as conflicting.

 */

static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,

		xpparam_t const *xpp)

{

	for (; m; m = m->next) {

		mmfile_t t1, t2;

		xdfenv_t xe;

		xdchange_t *xscr, *x;

		int i1 = m->i1, i2 = m->i2;

		/* let's handle just the conflicts */

		if (m->mode)

			continue;

		/* no sense refining a conflict when one side is empty */

		if (m->chg1 == 0 || m->chg2 == 0)

			continue;

		/*

		 * This probably does not work outside git, since

		 * we have a very simple mmfile structure.

		 */

		t1.ptr = (char *)xe1->xdf2.recs[m->i1]->ptr;

		t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1]->ptr

			+ xe1->xdf2.recs[m->i1 + m->chg1 - 1]->size - t1.ptr;

		t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;

		t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1]->ptr

			+ xe2->xdf2.recs[m->i2 + m->chg2 - 1]->size - t2.ptr;

		if (xdl_do_diff(&t1, &t2, xpp, &xe) < 0)

			return -1;

		if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||

		    xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||

		    xdl_build_script(&xe, &xscr) < 0) {

			xdl_free_env(&xe;;

			return -1;

		}

		if (!xscr) {

			/* If this happens, the changes are identical. */

			xdl_free_env(&xe;;

			m->mode = 4;

			continue;

		}

		x = xscr;

		m->i1 = xscr->i1 + i1;

		m->chg1 = xscr->chg1;

		m->i2 = xscr->i2 + i2;

		m->chg2 = xscr->chg2;

		while (xscr->next) {

			xdmerge_t *m2 = xdl_malloc(sizeof(xdmerge_t));

			if (!m2) {

				xdl_free_env(&xe;;

				xdl_free_script(x);

				return -1;

			}

			xscr = xscr->next;

			m2->next = m->next;

			m->next = m2;

			m = m2;

			m->mode = 0;

			m->i1 = xscr->i1 + i1;

			m->chg1 = xscr->chg1;

			m->i2 = xscr->i2 + i2;

			m->chg2 = xscr->chg2;

		}

		xdl_free_env(&xe;;

		xdl_free_script(x);

	}

	return 0;

}

static int line_contains_alnum(const char *ptr, long size)

{

	while (size--)

		if (isalnum((unsigned char)*(ptr++)))

			return 1;

	return 0;

}

static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)

{

	for (; chg; chg--, i++)

		if (line_contains_alnum(xe->xdf2.recs[i]->ptr,

				xe->xdf2.recs[i]->size))

			return 1;

	return 0;

}

/*

 * This function merges m and m->next, marking everything between those hunks

 * as conflicting, too.

 */

static void xdl_merge_two_conflicts(xdmerge_t *m)

{

	xdmerge_t *next_m = m->next;

	m->chg1 = next_m->i1 + next_m->chg1 - m->i1;

	m->chg2 = next_m->i2 + next_m->chg2 - m->i2;

	m->next = next_m->next;

	free(next_m);

}

/*

 * If there are less than 3 non-conflicting lines between conflicts,

 * it appears simpler -- because it takes up less (or as many) lines --

 * if the lines are moved into the conflicts.

 */

static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m,

				      int simplify_if_no_alnum)

{

	int result = 0;

	if (!m)

		return result;

	for (;;) {

		xdmerge_t *next_m = m->next;

		int begin, end;

		if (!next_m)

			return result;

		begin = m->i1 + m->chg1;

		end = next_m->i1;

		if (m->mode != 0 || next_m->mode != 0 ||

		    (end - begin > 3 &&

		     (!simplify_if_no_alnum ||

		      lines_contain_alnum(xe1, begin, end - begin)))) {

			m = next_m;

		} else {

			result++;

			xdl_merge_two_conflicts(m);

		}

	}

}

/*

 * level == 0: mark all overlapping changes as conflict

 * level == 1: mark overlapping changes as conflict only if not identical

 * level == 2: analyze non-identical changes for minimal conflict set

 * level == 3: analyze non-identical changes for minimal conflict set, but

 *             treat hunks not containing any letter or number as conflicting

 *

 * returns < 0 on error, == 0 for no conflicts, else number of conflicts

 */

static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1,

		xdfenv_t *xe2, xdchange_t *xscr2,

		xmparam_t const *xmp, mmbuffer_t *result)

{

	xdmerge_t *changes, *c;

	xpparam_t const *xpp = &xmp->xpp;

	const char *const ancestor_name = xmp->ancestor;

	const char *const name1 = xmp->file1;

	const char *const name2 = xmp->file2;

	int i0, i1, i2, chg0, chg1, chg2;

	int level = xmp->level;

	int style = xmp->style;

	int favor = xmp->favor;

	if (style == XDL_MERGE_DIFF3) {

		/*

		 * "diff3 -m" output does not make sense for anything

		 * more aggressive than XDL_MERGE_EAGER.

		 */

		if (XDL_MERGE_EAGER < level)

			level = XDL_MERGE_EAGER;

	}

	c = changes = NULL;

	while (xscr1 && xscr2) {

		if (!changes)

			changes = c;

		if (xscr1->i1 + xscr1->chg1 < xscr2->i1) {

			i0 = xscr1->i1;

			i1 = xscr1->i2;

			i2 = xscr2->i2 - xscr2->i1 + xscr1->i1;

			chg0 = xscr1->chg1;

			chg1 = xscr1->chg2;

			chg2 = xscr1->chg1;

			if (xdl_append_merge(&c, 1,

					     i0, chg0, i1, chg1, i2, chg2)) {

				xdl_cleanup_merge(changes);

				return -1;

			}

			xscr1 = xscr1->next;

			continue;

		}

		if (xscr2->i1 + xscr2->chg1 < xscr1->i1) {

			i0 = xscr2->i1;

			i1 = xscr1->i2 - xscr1->i1 + xscr2->i1;

			i2 = xscr2->i2;

			chg0 = xscr2->chg1;

			chg1 = xscr2->chg1;

			chg2 = xscr2->chg2;

			if (xdl_append_merge(&c, 2,

					     i0, chg0, i1, chg1, i2, chg2)) {

				xdl_cleanup_merge(changes);

				return -1;

			}

			xscr2 = xscr2->next;

			continue;

		}

		if (level == XDL_MERGE_MINIMAL || xscr1->i1 != xscr2->i1 ||

				xscr1->chg1 != xscr2->chg1 ||

				xscr1->chg2 != xscr2->chg2 ||

				xdl_merge_cmp_lines(xe1, xscr1->i2,

					xe2, xscr2->i2,

					xscr1->chg2, xpp->flags)) {

			/* conflict */

			int off = xscr1->i1 - xscr2->i1;

			int ffo = off + xscr1->chg1 - xscr2->chg1;

			i0 = xscr1->i1;

			i1 = xscr1->i2;

			i2 = xscr2->i2;

			if (off > 0) {

				i0 -= off;

				i1 -= off;

			}

			else

				i2 += off;

			chg0 = xscr1->i1 + xscr1->chg1 - i0;

			chg1 = xscr1->i2 + xscr1->chg2 - i1;

			chg2 = xscr2->i2 + xscr2->chg2 - i2;

			if (ffo < 0) {

				chg0 -= ffo;

				chg1 -= ffo;

			} else

				chg2 += ffo;

			if (xdl_append_merge(&c, 0,

					     i0, chg0, i1, chg1, i2, chg2)) {

				xdl_cleanup_merge(changes);

				return -1;

			}

		}

		i1 = xscr1->i1 + xscr1->chg1;

		i2 = xscr2->i1 + xscr2->chg1;

		if (i1 >= i2)

			xscr2 = xscr2->next;

		if (i2 >= i1)

			xscr1 = xscr1->next;

	}

	while (xscr1) {

		if (!changes)

			changes = c;

		i0 = xscr1->i1;

		i1 = xscr1->i2;

		i2 = xscr1->i1 + xe2->xdf2.nrec - xe2->xdf1.nrec;

		chg0 = xscr1->chg1;

		chg1 = xscr1->chg2;

		chg2 = xscr1->chg1;

		if (xdl_append_merge(&c, 1,

				     i0, chg0, i1, chg1, i2, chg2)) {

			xdl_cleanup_merge(changes);

			return -1;

		}

		xscr1 = xscr1->next;

	}

	while (xscr2) {

		if (!changes)

			changes = c;

		i0 = xscr2->i1;

		i1 = xscr2->i1 + xe1->xdf2.nrec - xe1->xdf1.nrec;

		i2 = xscr2->i2;

		chg0 = xscr2->chg1;

		chg1 = xscr2->chg1;

		chg2 = xscr2->chg2;

		if (xdl_append_merge(&c, 2,

				     i0, chg0, i1, chg1, i2, chg2)) {

			xdl_cleanup_merge(changes);

			return -1;

		}

		xscr2 = xscr2->next;

	}

	if (!changes)

		changes = c;

	/* refine conflicts */

	if (XDL_MERGE_ZEALOUS <= level &&

	    (xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||

	     xdl_simplify_non_conflicts(xe1, changes,

					XDL_MERGE_ZEALOUS < level) < 0)) {

		xdl_cleanup_merge(changes);

		return -1;

	}

	/* output */

	if (result) {

		int marker_size = xmp->marker_size;

		size_t size;

		if (xdl_fill_merge_buffer(&size, xe1, name1, xe2, name2,

						 ancestor_name,

						 favor, changes, NULL, style,

						 marker_size) < 0)

			return -1;

		result->ptr = xdl_malloc(size);

		if (!result->ptr) {

			xdl_cleanup_merge(changes);

			return -1;

		}

		result->size = size;

		if (xdl_fill_merge_buffer(&size, xe1, name1, xe2, name2,

				      ancestor_name, favor, changes,

				      result->ptr, style, marker_size) < 0)

			return -1;

	}

	return xdl_cleanup_merge(changes);

}

int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,

		xmparam_t const *xmp, mmbuffer_t *result)

{

	xdchange_t *xscr1, *xscr2;

	xdfenv_t xe1, xe2;

	int status;

	xpparam_t const *xpp = &xmp->xpp;

	result->ptr = NULL;

	result->size = 0;

	if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0) {

		return -1;

	}

	if (xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {

		xdl_free_env(&xe1);

		return -1;

	}

	if (xdl_change_compact(&xe1.xdf1, &xe1.xdf2, xpp->flags) < 0 ||

	    xdl_change_compact(&xe1.xdf2, &xe1.xdf1, xpp->flags) < 0 ||

	    xdl_build_script(&xe1, &xscr1) < 0) {

		xdl_free_env(&xe1);

		return -1;

	}

	if (xdl_change_compact(&xe2.xdf1, &xe2.xdf2, xpp->flags) < 0 ||

	    xdl_change_compact(&xe2.xdf2, &xe2.xdf1, xpp->flags) < 0 ||

	    xdl_build_script(&xe2, &xscr2) < 0) {

		xdl_free_script(xscr1);

		xdl_free_env(&xe1);

		xdl_free_env(&xe2);

		return -1;

	}

	status = 0;

	if (!xscr1) {

		result->ptr = xdl_malloc(mf2->size);

		memcpy(result->ptr, mf2->ptr, mf2->size);

		result->size = mf2->size;

	} else if (!xscr2) {

		result->ptr = xdl_malloc(mf1->size);

		memcpy(result->ptr, mf1->ptr, mf1->size);

		result->size = mf1->size;

	} else {

		status = xdl_do_merge(&xe1, xscr1,

				      &xe2, xscr2,

				      xmp, result);

	}

	xdl_free_script(xscr1);

	xdl_free_script(xscr2);

	xdl_free_env(&xe1);

	xdl_free_env(&xe2);

	return status;

}