/*

 *  LibXDiff by Davide Libenzi ( File Differential Library )

 *  Copyright (C) 2003	Davide Libenzi

 *

 *  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"

static long xdl_get_rec(xdfile_t *xdf, long ri, char const **rec);

static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb);

static long xdl_get_rec(xdfile_t *xdf, long ri, char const **rec) {

	*rec = xdf->recs[ri]->ptr;

	return xdf->recs[ri]->size;

}

static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb) {

	long size, psize = (long)strlen(pre);

	char const *rec;

	size = xdl_get_rec(xdf, ri, &rec);

	if (xdl_emit_diffrec(rec, size, pre, psize, ecb) < 0) {

		return -1;

	}

	return 0;

}

/*

 * Starting at the passed change atom, find the latest change atom to be included

 * inside the differential hunk according to the specified configuration.

 * Also advance xscr if the first changes must be discarded.

 */

xdchange_t *xdl_get_hunk(xdchange_t **xscr, xdemitconf_t const *xecfg)

{

	xdchange_t *xch, *xchp, *lxch;

	long max_common = 2 * xecfg->ctxlen + xecfg->interhunkctxlen;

	long max_ignorable = xecfg->ctxlen;

	unsigned long ignored = 0; /* number of ignored blank lines */

	/* remove ignorable changes that are too far before other changes */

	for (xchp = *xscr; xchp && xchp->ignore; xchp = xchp->next) {

		xch = xchp->next;

		if (xch == NULL ||

		    xch->i1 - (xchp->i1 + xchp->chg1) >= max_ignorable)

			*xscr = xch;

	}

	if (*xscr == NULL)

		return NULL;

	lxch = *xscr;

	for (xchp = *xscr, xch = xchp->next; xch; xchp = xch, xch = xch->next) {

		long distance = xch->i1 - (xchp->i1 + xchp->chg1);

		if (distance > max_common)

			break;

		if (distance < max_ignorable && (!xch->ignore || lxch == xchp)) {

			lxch = xch;

			ignored = 0;

		} else if (distance < max_ignorable && xch->ignore) {

			ignored += xch->chg2;

		} else if (lxch != xchp &&

			   xch->i1 + ignored - (lxch->i1 + lxch->chg1) > (unsigned long)max_common) {

			break;

		} else if (!xch->ignore) {

			lxch = xch;

			ignored = 0;

		} else {

			ignored += xch->chg2;

		}

	}

	return lxch;

}

static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)

{

	(void)priv;

	if (len > 0 &&

			(isalpha((unsigned char)*rec) || /* identifier? */

			 *rec == '_' ||	/* also identifier? */

			 *rec == '$')) { /* identifiers from VMS and other esoterico */

		if (len > sz)

			len = sz;

		while (0 < len && isspace((unsigned char)rec[len - 1]))

			len--;

		memcpy(buf, rec, len);

		return len;

	}

	return -1;

}

static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,

                           xdemitconf_t const *xecfg) {

	xdfile_t *xdf = &xe->xdf2;

	const char *rchg = xdf->rchg;

	long ix;

	(void)xscr;

	(void)xecfg;

	for (ix = 0; ix < xdf->nrec; ix++) {

		if (rchg[ix])

			continue;

		if (xdl_emit_record(xdf, ix, "", ecb))

			return -1;

	}

	return 0;

}

struct func_line {

	long len;

	char buf[80];

};

static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,

			  struct func_line *func_line, long start, long limit)

{

	find_func_t ff = xecfg->find_func ? xecfg->find_func : def_ff;

	long l, size, step = (start > limit) ? -1 : 1;

	char *buf, dummy[1];

	buf = func_line ? func_line->buf : dummy;

	size = func_line ? sizeof(func_line->buf) : sizeof(dummy);

	for (l = start; l != limit && 0 <= l && l < xe->xdf1.nrec; l += step) {

		const char *rec;

		long reclen = xdl_get_rec(&xe->xdf1, l, &rec);

		long len = ff(rec, reclen, buf, size, xecfg->find_func_priv);

		if (len >= 0) {

			if (func_line)

				func_line->len = len;

			return l;

		}

	}

	return -1;

}

int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,

		  xdemitconf_t const *xecfg) {

	long s1, s2, e1, e2, lctx;

	xdchange_t *xch, *xche;

	long funclineprev = -1;

	struct func_line func_line = { 0 };

	if (xecfg->flags & XDL_EMIT_COMMON)

		return xdl_emit_common(xe, xscr, ecb, xecfg);

	for (xch = xscr; xch; xch = xche->next) {

		xche = xdl_get_hunk(&xch, xecfg);

		if (!xch)

			break;

		s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0);

		s2 = XDL_MAX(xch->i2 - xecfg->ctxlen, 0);

		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {

			long fs1 = get_func_line(xe, xecfg, NULL, xch->i1, -1);

			if (fs1 < 0)

				fs1 = 0;

			if (fs1 < s1) {

				s2 -= s1 - fs1;

				s1 = fs1;

			}

		}

 again:

		lctx = xecfg->ctxlen;

		lctx = XDL_MIN(lctx, xe->xdf1.nrec - (xche->i1 + xche->chg1));

		lctx = XDL_MIN(lctx, xe->xdf2.nrec - (xche->i2 + xche->chg2));

		e1 = xche->i1 + xche->chg1 + lctx;

		e2 = xche->i2 + xche->chg2 + lctx;

		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {

			long fe1 = get_func_line(xe, xecfg, NULL,

						 xche->i1 + xche->chg1,

						 xe->xdf1.nrec);

			if (fe1 < 0)

				fe1 = xe->xdf1.nrec;

			if (fe1 > e1) {

				e2 += fe1 - e1;

				e1 = fe1;

			}

			/*

			 * Overlap with next change?  Then include it

			 * in the current hunk and start over to find

			 * its new end.

			 */

			if (xche->next) {

				long l = xche->next->i1;

				if (l <= e1 ||

				    get_func_line(xe, xecfg, NULL, l, e1) < 0) {

					xche = xche->next;

					goto again;

				}

			}

		}

		/*

		 * Emit current hunk header.

		 */

		if (xecfg->flags & XDL_EMIT_FUNCNAMES) {

			get_func_line(xe, xecfg, &func_line,

				      s1 - 1, funclineprev);

			funclineprev = s1 - 1;

		}

		if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,

				      func_line.buf, func_line.len, ecb) < 0)

			return -1;

		/*

		 * Emit pre-context.

		 */

		for (; s2 < xch->i2; s2++)

			if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)

				return -1;

		for (s1 = xch->i1, s2 = xch->i2;; xch = xch->next) {

			/*

			 * Merge previous with current change atom.

			 */

			for (; s1 < xch->i1 && s2 < xch->i2; s1++, s2++)

				if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)

					return -1;

			/*

			 * Removes lines from the first file.

			 */

			for (s1 = xch->i1; s1 < xch->i1 + xch->chg1; s1++)

				if (xdl_emit_record(&xe->xdf1, s1, "-", ecb) < 0)

					return -1;

			/*

			 * Adds lines from the second file.

			 */

			for (s2 = xch->i2; s2 < xch->i2 + xch->chg2; s2++)

				if (xdl_emit_record(&xe->xdf2, s2, "+", ecb) < 0)

					return -1;

			if (xch == xche)

				break;

			s1 = xch->i1 + xch->chg1;

			s2 = xch->i2 + xch->chg2;

		}

		/*

		 * Emit post-context.

		 */

		for (s2 = xche->i2 + xche->chg2; s2 < e2; s2++)

			if (xdl_emit_record(&xe->xdf2, s2, " ", ecb) < 0)

				return -1;

	}

	return 0;

}