/*

 *  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, see

 *  <http://www.gnu.org/licenses/>.

 *

 *  Davide Libenzi <davidel@xmailserver.org>

 *

 */

#include "xinclude.h"

#define XDL_MAX_COST_MIN 256

#define XDL_HEUR_MIN_COST 256

#define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)

#define XDL_SNAKE_CNT 20

#define XDL_K_HEUR 4

typedef struct s_xdpsplit {

	long i1, i2;

	int min_lo, min_hi;

} xdpsplit_t;

static long xdl_split(unsigned long const *ha1, long off1, long lim1,

		      unsigned long const *ha2, long off2, long lim2,

		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,

		      xdalgoenv_t *xenv);

static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2);

/*

 * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.

 * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both

 * the forward diagonal starting from (off1, off2) and the backward diagonal

 * starting from (lim1, lim2). If the K values on the same diagonal crosses

 * returns the furthest point of reach. We might end up having to expensive

 * cases using this algorithm is full, so a little bit of heuristic is needed

 * to cut the search and to return a suboptimal point.

 */

static long xdl_split(unsigned long const *ha1, long off1, long lim1,

		      unsigned long const *ha2, long off2, long lim2,

		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,

		      xdalgoenv_t *xenv) {

	long dmin = off1 - lim2, dmax = lim1 - off2;

	long fmid = off1 - off2, bmid = lim1 - lim2;

	long odd = (fmid - bmid) & 1;

	long fmin = fmid, fmax = fmid;

	long bmin = bmid, bmax = bmid;

	long ec, d, i1, i2, prev1, best, dd, v, k;

	/*

	 * Set initial diagonal values for both forward and backward path.

	 */

	kvdf[fmid] = off1;

	kvdb[bmid] = lim1;

	for (ec = 1;; ec++) {

		int got_snake = 0;

		/*

		 * We need to extent the diagonal "domain" by one. If the next

		 * values exits the box boundaries we need to change it in the

		 * opposite direction because (max - min) must be a power of two.

		 * Also we initialize the external K value to -1 so that we can

		 * avoid extra conditions check inside the core loop.

		 */

		if (fmin > dmin)

			kvdf[--fmin - 1] = -1;

		else

			++fmin;

		if (fmax < dmax)

			kvdf[++fmax + 1] = -1;

		else

			--fmax;

		for (d = fmax; d >= fmin; d -= 2) {

			if (kvdf[d - 1] >= kvdf[d + 1])

				i1 = kvdf[d - 1] + 1;

			else

				i1 = kvdf[d + 1];

			prev1 = i1;

			i2 = i1 - d;

			for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);

			if (i1 - prev1 > xenv->snake_cnt)

				got_snake = 1;

			kvdf[d] = i1;

			if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {

				spl->i1 = i1;

				spl->i2 = i2;

				spl->min_lo = spl->min_hi = 1;

				return ec;

			}

		}

		/*

		 * We need to extent the diagonal "domain" by one. If the next

		 * values exits the box boundaries we need to change it in the

		 * opposite direction because (max - min) must be a power of two.

		 * Also we initialize the external K value to -1 so that we can

		 * avoid extra conditions check inside the core loop.

		 */

		if (bmin > dmin)

			kvdb[--bmin - 1] = XDL_LINE_MAX;

		else

			++bmin;

		if (bmax < dmax)

			kvdb[++bmax + 1] = XDL_LINE_MAX;

		else

			--bmax;

		for (d = bmax; d >= bmin; d -= 2) {

			if (kvdb[d - 1] < kvdb[d + 1])

				i1 = kvdb[d - 1];

			else

				i1 = kvdb[d + 1] - 1;

			prev1 = i1;

			i2 = i1 - d;

			for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);

			if (prev1 - i1 > xenv->snake_cnt)

				got_snake = 1;

			kvdb[d] = i1;

			if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {

				spl->i1 = i1;

				spl->i2 = i2;

				spl->min_lo = spl->min_hi = 1;

				return ec;

			}

		}

		if (need_min)

			continue;

		/*

		 * If the edit cost is above the heuristic trigger and if

		 * we got a good snake, we sample current diagonals to see

		 * if some of the, have reached an "interesting" path. Our

		 * measure is a function of the distance from the diagonal

		 * corner (i1 + i2) penalized with the distance from the

		 * mid diagonal itself. If this value is above the current

		 * edit cost times a magic factor (XDL_K_HEUR) we consider

		 * it interesting.

		 */

		if (got_snake && ec > xenv->heur_min) {

			for (best = 0, d = fmax; d >= fmin; d -= 2) {

				dd = d > fmid ? d - fmid: fmid - d;

				i1 = kvdf[d];

				i2 = i1 - d;

				v = (i1 - off1) + (i2 - off2) - dd;

				if (v > XDL_K_HEUR * ec && v > best &&

				    off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&

				    off2 + xenv->snake_cnt <= i2 && i2 < lim2) {

					for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)

						if (k == xenv->snake_cnt) {

							best = v;

							spl->i1 = i1;

							spl->i2 = i2;

							break;

						}

				}

			}

			if (best > 0) {

				spl->min_lo = 1;

				spl->min_hi = 0;

				return ec;

			}

			for (best = 0, d = bmax; d >= bmin; d -= 2) {

				dd = d > bmid ? d - bmid: bmid - d;

				i1 = kvdb[d];

				i2 = i1 - d;

				v = (lim1 - i1) + (lim2 - i2) - dd;

				if (v > XDL_K_HEUR * ec && v > best &&

				    off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&

				    off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {

					for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)

						if (k == xenv->snake_cnt - 1) {

							best = v;

							spl->i1 = i1;

							spl->i2 = i2;

							break;

						}

				}

			}

			if (best > 0) {

				spl->min_lo = 0;

				spl->min_hi = 1;

				return ec;

			}

		}

		/*

		 * Enough is enough. We spent too much time here and now we collect

		 * the furthest reaching path using the (i1 + i2) measure.

		 */

		if (ec >= xenv->mxcost) {

			long fbest, fbest1, bbest, bbest1;

			fbest = fbest1 = -1;

			for (d = fmax; d >= fmin; d -= 2) {

				i1 = XDL_MIN(kvdf[d], lim1);

				i2 = i1 - d;

				if (lim2 < i2)

					i1 = lim2 + d, i2 = lim2;

				if (fbest < i1 + i2) {

					fbest = i1 + i2;

					fbest1 = i1;

				}

			}

			bbest = bbest1 = XDL_LINE_MAX;

			for (d = bmax; d >= bmin; d -= 2) {

				i1 = XDL_MAX(off1, kvdb[d]);

				i2 = i1 - d;

				if (i2 < off2)

					i1 = off2 + d, i2 = off2;

				if (i1 + i2 < bbest) {

					bbest = i1 + i2;

					bbest1 = i1;

				}

			}

			if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {

				spl->i1 = fbest1;

				spl->i2 = fbest - fbest1;

				spl->min_lo = 1;

				spl->min_hi = 0;

			} else {

				spl->i1 = bbest1;

				spl->i2 = bbest - bbest1;

				spl->min_lo = 0;

				spl->min_hi = 1;

			}

			return ec;

		}

	}

}

/*

 * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling

 * the box splitting function. Note that the real job (marking changed lines)

 * is done in the two boundary reaching checks.

 */

int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,

		 diffdata_t *dd2, long off2, long lim2,

		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {

	unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;

	/*

	 * Shrink the box by walking through each diagonal snake (SW and NE).

	 */

	for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);

	for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);

	/*

	 * If one dimension is empty, then all records on the other one must

	 * be obviously changed.

	 */

	if (off1 == lim1) {

		char *rchg2 = dd2->rchg;

		long *rindex2 = dd2->rindex;

		for (; off2 < lim2; off2++)

			rchg2[rindex2[off2]] = 1;

	} else if (off2 == lim2) {

		char *rchg1 = dd1->rchg;

		long *rindex1 = dd1->rindex;

		for (; off1 < lim1; off1++)

			rchg1[rindex1[off1]] = 1;

	} else {

		xdpsplit_t spl;

		spl.i1 = spl.i2 = 0;

		/*

		 * Divide ...

		 */

		if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,

			      need_min, &spl, xenv) < 0) {

			return -1;

		}

		/*

		 * ... et Impera.

		 */

		if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,

				 kvdf, kvdb, spl.min_lo, xenv) < 0 ||

		    xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,

				 kvdf, kvdb, spl.min_hi, xenv) < 0) {

			return -1;

		}

	}

	return 0;

}

int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,

		xdfenv_t *xe) {

	long ndiags;

	long *kvd, *kvdf, *kvdb;

	xdalgoenv_t xenv;

	diffdata_t dd1, dd2;

	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {

		return -1;

	}

	/*

	 * Allocate and setup K vectors to be used by the differential algorithm.

	 * One is to store the forward path and one to store the backward path.

	 */

	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;

	if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {

		xdl_free_env(xe);

		return -1;

	}

	kvdf = kvd;

	kvdb = kvdf + ndiags;

	kvdf += xe->xdf2.nreff + 1;

	kvdb += xe->xdf2.nreff + 1;

	xenv.mxcost = xdl_bogosqrt(ndiags);

	if (xenv.mxcost < XDL_MAX_COST_MIN)

		xenv.mxcost = XDL_MAX_COST_MIN;

	xenv.snake_cnt = XDL_SNAKE_CNT;

	xenv.heur_min = XDL_HEUR_MIN_COST;

	dd1.nrec = xe->xdf1.nreff;

	dd1.ha = xe->xdf1.ha;

	dd1.rchg = xe->xdf1.rchg;

	dd1.rindex = xe->xdf1.rindex;

	dd2.nrec = xe->xdf2.nreff;

	dd2.ha = xe->xdf2.ha;

	dd2.rchg = xe->xdf2.rchg;

	dd2.rindex = xe->xdf2.rindex;

	if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,

			 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {

		xdl_free(kvd);

		xdl_free_env(xe);

		return -1;

	}

	xdl_free(kvd);

	return 0;

}

static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {

	xdchange_t *xch;

	if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))

		return NULL;

	xch->next = xscr;

	xch->i1 = i1;

	xch->i2 = i2;

	xch->chg1 = chg1;

	xch->chg2 = chg2;

	xch->ignore = 0;

	return xch;

}

static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)

{

	return (rec1->ha == rec2->ha &&

		xdl_recmatch(rec1->ptr, rec1->size,

			     rec2->ptr, rec2->size,

			     flags));

}

/*

 * If a line is indented more than this, get_indent() just returns this value.

 * This avoids having to do absurd amounts of work for data that are not

 * human-readable text, and also ensures that the output of get_indent fits within

 * an int.

 */

#define MAX_INDENT 200

/*

 * Return the amount of indentation of the specified line, treating TAB as 8

 * columns. Return -1 if line is empty or contains only whitespace. Clamp the

 * output value at MAX_INDENT.

 */

static int get_indent(xrecord_t *rec)

{

	long i;

	int ret = 0;

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

		char c = rec->ptr[i];

		if (!XDL_ISSPACE(c))

			return ret;

		else if (c == ' ')

			ret += 1;

		else if (c == '\t')

			ret += 8 - ret % 8;

		/* ignore other whitespace characters */

		if (ret >= MAX_INDENT)

			return MAX_INDENT;

	}

	/* The line contains only whitespace. */

	return -1;

}

/*

 * If more than this number of consecutive blank rows are found, just return this

 * value. This avoids requiring O(N^2) work for pathological cases, and also

 * ensures that the output of score_split fits in an int.

 */

#define MAX_BLANKS 20

/* Characteristics measured about a hypothetical split position. */

struct split_measurement {

	/*

	 * Is the split at the end of the file (aside from any blank lines)?

	 */

	int end_of_file;

	/*

	 * How much is the line immediately following the split indented (or -1 if

	 * the line is blank):

	 */

	int indent;

	/*

	 * How many consecutive lines above the split are blank?

	 */

	int pre_blank;

	/*

	 * How much is the nearest non-blank line above the split indented (or -1

	 * if there is no such line)?

	 */

	int pre_indent;

	/*

	 * How many lines after the line following the split are blank?

	 */

	int post_blank;

	/*

	 * How much is the nearest non-blank line after the line following the

	 * split indented (or -1 if there is no such line)?

	 */

	int post_indent;

};

struct split_score {

	/* The effective indent of this split (smaller is preferred). */

	int effective_indent;

	/* Penalty for this split (smaller is preferred). */

	int penalty;

};

/*

 * Fill m with information about a hypothetical split of xdf above line split.

 */

static void measure_split(const xdfile_t *xdf, long split,

			  struct split_measurement *m)

{

	long i;

	if (split >= xdf->nrec) {

		m->end_of_file = 1;

		m->indent = -1;

	} else {

		m->end_of_file = 0;

		m->indent = get_indent(xdf->recs[split]);

	}

	m->pre_blank = 0;

	m->pre_indent = -1;

	for (i = split - 1; i >= 0; i--) {

		m->pre_indent = get_indent(xdf->recs[i]);

		if (m->pre_indent != -1)

			break;

		m->pre_blank += 1;

		if (m->pre_blank == MAX_BLANKS) {

			m->pre_indent = 0;

			break;

		}

	}

	m->post_blank = 0;

	m->post_indent = -1;

	for (i = split + 1; i < xdf->nrec; i++) {

		m->post_indent = get_indent(xdf->recs[i]);

		if (m->post_indent != -1)

			break;

		m->post_blank += 1;