/*
 *  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 = 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) > 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)
{
        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 long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
                           char *buf, long sz)
{
        const char *rec;
        long len = xdl_get_rec(xdf, ri, &rec);
        if (!xecfg->find_func)
                return def_ff(rec, len, buf, sz, xecfg->find_func_priv);
        return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
}

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)
{
        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) {
                long len = match_func_rec(&xe->xdf1, xecfg, l, buf, size);
                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 };

        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;
}