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




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.
 */
static xdchange_t *xdl_get_hunk(xdchange_t *xscr, xdemitconf_t const *xecfg) {
        xdchange_t *xch, *xchp;

        for (xchp = xscr, xch = xscr->next; xch; xchp = xch, xch = xch->next)
                if (xch->i1 - (xchp->i1 + xchp->chg1) > 2 * xecfg->ctxlen)
                        break;

        return xchp;
}


static void xdl_find_func(xdfile_t *xf, long i, char *buf, long sz, long *ll) {

        /*
         * Be quite stupid about this for now.  Find a line in the old file
         * before the start of the hunk (and context) which starts with a
         * plausible character.
         */

        const char *rec;
        long len;

        *ll = 0;
        while (i-- > 0) {
                len = xdl_get_rec(xf, i, &rec);
                if (len > 0 &&
                    (isalpha((unsigned char)*rec) || /* identifier? */
                     *rec == '_' ||     /* also identifier? */
                     *rec == '(' ||     /* lisp defun? */
                     *rec == '#')) {    /* #define? */
                        if (len > sz)
                                len = sz;
                        if (len && rec[len - 1] == '\n')
                                len--;
                        memcpy(buf, rec, len);
                        *ll = len;
                        return;
                }
        }
}


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;
        char funcbuf[40];
        long funclen = 0;

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

                s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0);
                s2 = XDL_MAX(xch->i2 - xecfg->ctxlen, 0);

                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;

                /*
                 * Emit current hunk header.
                 */

                if (xecfg->flags & XDL_EMIT_FUNCNAMES) {
                        xdl_find_func(&xe->xdf1, s1, funcbuf,
                                      sizeof(funcbuf), &funclen);
                }
                if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
                                      funcbuf, funclen, ecb) < 0)
                        return -1;

                /*
                 * Emit pre-context.
                 */
                for (; s1 < xch->i1; s1++)
                        if (xdl_emit_record(&xe->xdf1, s1, " ", 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->xdf1, s1, " ", 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 (s1 = xche->i1 + xche->chg1; s1 < e1; s1++)
                        if (xdl_emit_record(&xe->xdf1, s1, " ", ecb) < 0)
                                return -1;
        }

        return 0;
}