/*
 *  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"


#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;
} xdlclass_t;

typedef struct s_xdlclassifier {
        unsigned int hbits;
        long hsize;
        xdlclass_t **rchash;
        chastore_t ncha;
        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(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
                               xrecord_t *rec);
static int xdl_prepare_ctx(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(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(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->count = 0;

        return 0;
}


static void xdl_free_classifier(xdlclassifier_t *cf) {

        xdl_free(cf->rchash);
        xdl_cha_free(&cf->ncha);
}


static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
                               xrecord_t *rec) {
        long hi;
        char const *line;
        xdlclass_t *rcrec;

        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++;
                rcrec->line = line;
                rcrec->size = rec->size;
                rcrec->ha = rec->ha;
                rcrec->next = cf->rchash[hi];
                cf->rchash[hi] = rcrec;
        }

        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(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 (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 (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
                                xdl_classify_record(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;

        /*
         * 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 = 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 (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
                xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {

                return -1;
        }

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

                xdl_free_classifier(&cf);
                return -1;
        }
        if (xdl_prepare_ctx(mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {

                xdl_free_ctx(&xe->xdf1);
                xdl_free_classifier(&cf);
                return -1;
        }

        if (!(xpp->flags & XDF_HISTOGRAM_DIFF))
                xdl_free_classifier(&cf);

        if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
                        !(xpp->flags & XDF_HISTOGRAM_DIFF) &&
                        xdl_optimize_ctxs(&xe->xdf1, &xe->xdf2) < 0) {

                xdl_free_ctx(&xe->xdf2);
                xdl_free_ctx(&xe->xdf1);
                return -1;
        }

        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(xdfile_t *xdf1, xdfile_t *xdf2) {
        long i, nm, rhi, nreff, mlim;
        unsigned long hav;
        xrecord_t **recs;
        xrecord_t *rec;
        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++) {
                hav = (*recs)->ha;
                rhi = (long) XDL_HASHLONG(hav, xdf2->hbits);
                for (nm = 0, rec = xdf2->rhash[rhi]; rec; rec = rec->next)
                        if (rec->ha == hav && ++nm == mlim)
                                break;
                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++) {
                hav = (*recs)->ha;
                rhi = (long) XDL_HASHLONG(hav, xdf1->hbits);
                for (nm = 0, rec = xdf1->rhash[rhi]; rec; rec = rec->next)
                        if (rec->ha == hav && ++nm == mlim)
                                break;
                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(xdfile_t *xdf1, xdfile_t *xdf2) {

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

                return -1;
        }

        return 0;
}