/*

 *  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"

static int xdl_emit_record(xdfile_t *xdf, long ri, char const *pre, xdemitcb_t *ecb)

{

  xrecord_t *rec = &xdf->recs[ri];

  if (xdl_emit_diffrec((char const *)rec->ptr, (long)rec->size, pre, strlen(pre), ecb) < 0)

    return -1;

  return 0;

}

static long saturating_add(long a, long b)

{

  return signed_add_overflows(a, b) ? LONG_MAX : a + b;

}

/*

 * 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;

  long max_ignorable;

  long ignored = 0; /* number of ignored blank lines */

  if (xecfg->ctxlen < 0)

    BUG("negative context length: %ld", xecfg->ctxlen);

  if (xecfg->interhunkctxlen < 0)

    BUG("negative inter-hunk context length: %ld", xecfg->interhunkctxlen);

  max_common = saturating_add(saturating_add(xecfg->ctxlen,

               xecfg->ctxlen),

            xecfg->interhunkctxlen);

  max_ignorable = xecfg->ctxlen;

  /* 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)

    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)

{

  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)

{

  xrecord_t *rec = &xdf->recs[ri];

  if (!xecfg->find_func)

    return def_ff((const char *)rec->ptr, (long)rec->size, buf, sz);

  return xecfg->find_func((const char *)rec->ptr, (long)rec->size, buf, sz, xecfg->find_func_priv);

}

static int is_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri)

{

  char dummy[1];

  return match_func_rec(xdf, xecfg, ri, dummy, sizeof(dummy)) >= 0;

}

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 < (long)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;

}

static int is_empty_rec(xdfile_t *xdf, long ri)

{

  xrecord_t *rec = &xdf->recs[ri];

  size_t i = 0;

  for (; i < rec->size && XDL_ISSPACE(rec->ptr[i]); i++);

  return i == rec->size;

}

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) {

    xdchange_t *xchp = xch;

    xche = xdl_get_hunk(&xch, xecfg);

    if (!xch)

      break;

pre_context_calculation:

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

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

    if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {

      long fs1, i1 = xch->i1;

      /* Appended chunk? */

      if (i1 >= (long)xe->xdf1.nrec) {

        long i2 = xch->i2;

        /*

         * We don't need additional context if

         * a whole function was added.

         */

        while (i2 < (long)xe->xdf2.nrec) {

          if (is_func_rec(&xe->xdf2, xecfg, i2))

            goto post_context_calculation;

          i2++;

        }

        /*

         * Otherwise get more context from the

         * pre-image.

         */

        i1 = (long)xe->xdf1.nrec - 1;

      }

      fs1 = get_func_line(xe, xecfg, NULL, i1, -1);

      while (fs1 > 0 && !is_empty_rec(&xe->xdf1, fs1 - 1) &&

             !is_func_rec(&xe->xdf1, xecfg, fs1 - 1))

        fs1--;

      if (fs1 < 0)

        fs1 = 0;

      if (fs1 < s1) {

        s2 = XDL_MAX(s2 - (s1 - fs1), 0);

        s1 = fs1;

        /*

         * Did we extend context upwards into an

         * ignored change?

         */

        while (xchp != xch &&

               xchp->i1 + xchp->chg1 <= s1 &&

               xchp->i2 + xchp->chg2 <= s2)

          xchp = xchp->next;

        /* If so, show it after all. */

        if (xchp != xch) {

          xch = xchp;

          goto pre_context_calculation;

        }

      }

    }

 post_context_calculation:

    lctx = xecfg->ctxlen;

    lctx = XDL_MIN(lctx, (long)xe->xdf1.nrec - (xche->i1 + xche->chg1));

    lctx = XDL_MIN(lctx, (long)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,

             (long)xe->xdf1.nrec);

      while (fe1 > 0 && is_empty_rec(&xe->xdf1, fe1 - 1))

        fe1--;

      if (fe1 < 0)

        fe1 = (long)xe->xdf1.nrec;

      if (fe1 > e1) {

        e2 = XDL_MIN(e2 + (fe1 - e1), (long)xe->xdf2.nrec);

        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 = XDL_MIN(xche->next->i1,

             (long)xe->xdf1.nrec - 1);

        if (l - xecfg->ctxlen <= e1 ||

            get_func_line(xe, xecfg, NULL, l, e1) < 0) {

          xche = xche->next;

          goto post_context_calculation;

        }

      }

    }

    /*

     * Emit current hunk header.

     */

    if (xecfg->flags & XDL_EMIT_FUNCNAMES) {

      get_func_line(xe, xecfg, &func_line,

              s1 - 1, funclineprev);

      funclineprev = s1 - 1;

    }

    if (!(xecfg->flags & XDL_EMIT_NO_HUNK_HDR) &&

        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;

}