/*

 *  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_KPDIS_RUN 4

#define XDL_MAX_EQLIMIT 1024

#define XDL_SIMSCAN_WINDOW 100

#define XDL_GUESS_NLINES1 256

#define XDL_GUESS_NLINES2 20

typedef struct s_xdlclass {

	struct s_xdlclass *next;

	unsigned long ha;

	char const *line;

	long size;

	long idx;

	long len1, len2;

} xdlclass_t;

typedef struct s_xdlclassifier {

	unsigned int hbits;

	long hsize;

	xdlclass_t **rchash;

	chastore_t ncha;

	xdlclass_t **rcrecs;

	long alloc;

	long count;

	long flags;

} xdlclassifier_t;

static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);

static void xdl_free_classifier(xdlclassifier_t *cf);

static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,

			       unsigned int hbits, xrecord_t *rec);

static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,

			   xdlclassifier_t *cf, xdfile_t *xdf);

static void xdl_free_ctx(xdfile_t *xdf);

static int xdl_clean_mmatch(char const *dis, long i, long s, long e);

static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);

static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);

static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);

static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {

	cf->flags = flags;

	cf->hbits = xdl_hashbits((unsigned int) size);

	cf->hsize = 1 << cf->hbits;

	if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {

		return -1;

	}

	if (!(cf->rchash = (xdlclass_t **) xdl_malloc(cf->hsize * sizeof(xdlclass_t *)))) {

		xdl_cha_free(&cf->ncha);

		return -1;

	}

	memset(cf->rchash, 0, cf->hsize * sizeof(xdlclass_t *));

	cf->alloc = size;

	if (!(cf->rcrecs = (xdlclass_t **) xdl_malloc(cf->alloc * sizeof(xdlclass_t *)))) {

		xdl_free(cf->rchash);

		xdl_cha_free(&cf->ncha);

		return -1;

	}

	cf->count = 0;

	return 0;

}

static void xdl_free_classifier(xdlclassifier_t *cf) {

	xdl_free(cf->rcrecs);

	xdl_free(cf->rchash);

	xdl_cha_free(&cf->ncha);

}

static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,

			       unsigned int hbits, xrecord_t *rec) {

	long hi;

	char const *line;

	xdlclass_t *rcrec;

	xdlclass_t **rcrecs;

	line = rec->ptr;

	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);

	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)

		if (rcrec->ha == rec->ha &&

				xdl_recmatch(rcrec->line, rcrec->size,

					rec->ptr, rec->size, cf->flags))

			break;

	if (!rcrec) {

		if (!(rcrec = xdl_cha_alloc(&cf->ncha))) {

			return -1;

		}

		rcrec->idx = cf->count++;

		if (cf->count > cf->alloc) {

			cf->alloc *= 2;

			if (!(rcrecs = (xdlclass_t **) xdl_realloc(cf->rcrecs, cf->alloc * sizeof(xdlclass_t *)))) {

				return -1;

			}

			cf->rcrecs = rcrecs;

		}

		cf->rcrecs[rcrec->idx] = rcrec;

		rcrec->line = line;

		rcrec->size = rec->size;

		rcrec->ha = rec->ha;

		rcrec->len1 = rcrec->len2 = 0;

		rcrec->next = cf->rchash[hi];

		cf->rchash[hi] = rcrec;

	}

	(pass == 1) ? rcrec->len1++ : rcrec->len2++;

	rec->ha = (unsigned long) rcrec->idx;

	hi = (long) XDL_HASHLONG(rec->ha, hbits);

	rec->next = rhash[hi];

	rhash[hi] = rec;

	return 0;

}

static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,

			   xdlclassifier_t *cf, xdfile_t *xdf) {

	unsigned int hbits;

	long nrec, hsize, bsize;

	unsigned long hav;

	char const *blk, *cur, *top, *prev;

	xrecord_t *crec;

	xrecord_t **recs, **rrecs;

	xrecord_t **rhash;

	unsigned long *ha;

	char *rchg;

	long *rindex;

	ha = NULL;

	rindex = NULL;

	rchg = NULL;

	rhash = NULL;

	recs = NULL;

	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)

		goto abort;

	if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))

		goto abort;

	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)

		hbits = hsize = 0;

	else {

		hbits = xdl_hashbits((unsigned int) narec);

		hsize = 1 << hbits;

		if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))

			goto abort;

		memset(rhash, 0, hsize * sizeof(xrecord_t *));

	}

	nrec = 0;

	if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {

		for (top = blk + bsize; cur < top; ) {

			prev = cur;

			hav = xdl_hash_record(&cur, top, xpp->flags);

			if (nrec >= narec) {

				narec *= 2;

				if (!(rrecs = (xrecord_t **) xdl_realloc(recs, narec * sizeof(xrecord_t *))))

					goto abort;

				recs = rrecs;

			}

			if (!(crec = xdl_cha_alloc(&xdf->rcha)))

				goto abort;

			crec->ptr = prev;

			crec->size = (long) (cur - prev);

			crec->ha = hav;

			recs[nrec++] = crec;

			if ((XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&

			    xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)

				goto abort;

		}

	}

	if (!(rchg = (char *) xdl_malloc((nrec + 2) * sizeof(char))))

		goto abort;

	memset(rchg, 0, (nrec + 2) * sizeof(char));

	if (!(rindex = (long *) xdl_malloc((nrec + 1) * sizeof(long))))

		goto abort;

	if (!(ha = (unsigned long *) xdl_malloc((nrec + 1) * sizeof(unsigned long))))

		goto abort;

	xdf->nrec = nrec;

	xdf->recs = recs;

	xdf->hbits = hbits;

	xdf->rhash = rhash;

	xdf->rchg = rchg + 1;

	xdf->rindex = rindex;

	xdf->nreff = 0;

	xdf->ha = ha;

	xdf->dstart = 0;

	xdf->dend = nrec - 1;

	return 0;

abort:

	xdl_free(ha);

	xdl_free(rindex);

	xdl_free(rchg);

	xdl_free(rhash);

	xdl_free(recs);

	xdl_cha_free(&xdf->rcha);

	return -1;

}

static void xdl_free_ctx(xdfile_t *xdf) {

	xdl_free(xdf->rhash);

	xdl_free(xdf->rindex);

	xdl_free(xdf->rchg - 1);

	xdl_free(xdf->ha);

	xdl_free(xdf->recs);

	xdl_cha_free(&xdf->rcha);

}

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

		    xdfenv_t *xe) {

	long enl1, enl2, sample;

	xdlclassifier_t cf;

	memset(&cf, 0, sizeof(cf));

	/*

	 * For histogram diff, we can afford a smaller sample size and

	 * thus a poorer estimate of the number of lines, as the hash

	 * table (rhash) won't be filled up/grown. The number of lines

	 * (nrecs) will be updated correctly anyway by

	 * xdl_prepare_ctx().

	 */

	sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF

		  ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);

	enl1 = xdl_guess_lines(mf1, sample) + 1;

	enl2 = xdl_guess_lines(mf2, sample) + 1;

	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF &&

	    xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)

		return -1;

	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {

		xdl_free_classifier(&cf);

		return -1;

	}

	if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {

		xdl_free_ctx(&xe->xdf1);

		xdl_free_classifier(&cf);

		return -1;

	}

	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&

	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&

	    xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {

		xdl_free_ctx(&xe->xdf2);

		xdl_free_ctx(&xe->xdf1);

		xdl_free_classifier(&cf);

		return -1;

	}

	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)

		xdl_free_classifier(&cf);

	return 0;

}

void xdl_free_env(xdfenv_t *xe) {

	xdl_free_ctx(&xe->xdf2);

	xdl_free_ctx(&xe->xdf1);

}

static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {

	long r, rdis0, rpdis0, rdis1, rpdis1;

	/*

	 * Limits the window the is examined during the similar-lines

	 * scan. The loops below stops when dis[i - r] == 1 (line that

	 * has no match), but there are corner cases where the loop

	 * proceed all the way to the extremities by causing huge

	 * performance penalties in case of big files.

	 */

	if (i - s > XDL_SIMSCAN_WINDOW)

		s = i - XDL_SIMSCAN_WINDOW;

	if (e - i > XDL_SIMSCAN_WINDOW)

		e = i + XDL_SIMSCAN_WINDOW;

	/*

	 * Scans the lines before 'i' to find a run of lines that either

	 * have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).

	 * Note that we always call this function with dis[i] > 1, so the

	 * current line (i) is already a multimatch line.

	 */

	for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {

		if (!dis[i - r])

			rdis0++;

		else if (dis[i - r] == 2)

			rpdis0++;

		else

			break;

	}

	/*

	 * If the run before the line 'i' found only multimatch lines, we

	 * return 0 and hence we don't make the current line (i) discarded.

	 * We want to discard multimatch lines only when they appear in the

	 * middle of runs with nomatch lines (dis[j] == 0).

	 */

	if (rdis0 == 0)

		return 0;

	for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {

		if (!dis[i + r])

			rdis1++;

		else if (dis[i + r] == 2)

			rpdis1++;

		else

			break;

	}

	/*

	 * If the run after the line 'i' found only multimatch lines, we

	 * return 0 and hence we don't make the current line (i) discarded.

	 */

	if (rdis1 == 0)

		return 0;

	rdis1 += rdis0;

	rpdis1 += rpdis0;

	return rpdis1 * XDL_KPDIS_RUN < (rpdis1 + rdis1);

}

/*

 * Try to reduce the problem complexity, discard records that have no

 * matches on the other file. Also, lines that have multiple matches

 * might be potentially discarded if they happear in a run of discardable.

 */

static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

	long i, nm, nreff, mlim;

	xrecord_t **recs;

	xdlclass_t *rcrec;

	char *dis, *dis1, *dis2;

	if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {

		return -1;

	}

	memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);

	dis1 = dis;

	dis2 = dis1 + xdf1->nrec + 1;

	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)

		mlim = XDL_MAX_EQLIMIT;

	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {

		rcrec = cf->rcrecs[(*recs)->ha];

		nm = rcrec ? rcrec->len2 : 0;

		dis1[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;

	}

	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)

		mlim = XDL_MAX_EQLIMIT;

	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {

		rcrec = cf->rcrecs[(*recs)->ha];

		nm = rcrec ? rcrec->len1 : 0;

		dis2[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;

	}

	for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];

	     i <= xdf1->dend; i++, recs++) {

		if (dis1[i] == 1 ||

		    (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {

			xdf1->rindex[nreff] = i;

			xdf1->ha[nreff] = (*recs)->ha;

			nreff++;

		} else

			xdf1->rchg[i] = 1;

	}

	xdf1->nreff = nreff;

	for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];

	     i <= xdf2->dend; i++, recs++) {

		if (dis2[i] == 1 ||

		    (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {

			xdf2->rindex[nreff] = i;

			xdf2->ha[nreff] = (*recs)->ha;

			nreff++;

		} else

			xdf2->rchg[i] = 1;

	}

	xdf2->nreff = nreff;

	xdl_free(dis);

	return 0;

}

/*

 * Early trim initial and terminal matching records.

 */

static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {

	long i, lim;

	xrecord_t **recs1, **recs2;

	recs1 = xdf1->recs;

	recs2 = xdf2->recs;

	for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;

	     i++, recs1++, recs2++)

		if ((*recs1)->ha != (*recs2)->ha)

			break;

	xdf1->dstart = xdf2->dstart = i;

	recs1 = xdf1->recs + xdf1->nrec - 1;

	recs2 = xdf2->recs + xdf2->nrec - 1;

	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)

		if ((*recs1)->ha != (*recs2)->ha)

			break;

	xdf1->dend = xdf1->nrec - i - 1;

	xdf2->dend = xdf2->nrec - i - 1;

	return 0;

}

static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

	if (xdl_trim_ends(xdf1, xdf2) < 0 ||

	    xdl_cleanup_records(cf, xdf1, xdf2) < 0) {

		return -1;

	}

	return 0;

}