//
//	aegis - project change supervisor
//	Copyright (C) 2001, 2003-2008 Peter Miller
//
//	This program is free software; you can redistribute it and/or modify
//	it under the terms of the GNU General Public License as published by
//	the Free Software Foundation; either version 3 of the License, or
//	(at your option) any later version.
//
//	This program 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 General Public License for more details.
//
//	You should have received a copy of the GNU General Public License
//	along with this program. If not, see
//	<http://www.gnu.org/licenses/>.
//

#include <libaegis/change/branch.h>
#include <common/error.h> // for assert
#include <libaegis/interval.h>
#include <common/skip_unlucky.h>
#include <common/trace.h>


long
change_branch_next_change_number(change::pointer cp, int is_a_change)
{
    cstate_ty       *cstate_data;
    cstate_branch_change_list_ty *lp;
    long            change_number;
    size_t          j, k;
    long            minchanum;
    int             reuse;

    trace(("change_branch_next_change_number(cp = %8.8lX)\n{\n",
	(long)cp));
    cstate_data = cp->cstate_get();
    assert(cstate_data->branch);
    if (!cstate_data->branch->change)
    {
	cstate_data->branch->change =
	    (cstate_branch_change_list_ty *)
            cstate_branch_change_list_type.alloc();
    }
    lp = cstate_data->branch->change;

    //
    // build an interval which contains the set of changes
    // (it could be empty)
    //
    interval ip1;
    for (j = 0; j < lp->length; )
    {
	for (k = j + 1; k < lp->length; ++k)
	    if (lp->list[k - 1] + 1 != lp->list[k])
	       	break;
	ip1 += interval(lp->list[j], lp->list[k - 1]);
	j = k;
    }

    //
    // difference the above set from the interval [minchanum..max)
    // This avoids zero.  If the user wants a zero-numbered change,
    // she must ask for it.
    //
    if (is_a_change)
	minchanum = change_branch_minimum_change_number_get(cp);
    else
	minchanum = change_branch_minimum_branch_number_get(cp);
    interval ip2(minchanum, TRUNK_CHANGE_NUMBER - 1);
    interval ip3 = ip2 - ip1;
    assert(!ip3.empty());

    //
    // The result is the minimum acceptable number in the interval.
    // But !reuse means the first number in the last interval.
    //
    reuse = !is_a_change || change_branch_reuse_change_numbers_get(cp);
    if (!change_branch_skip_unlucky_get(cp))
    {
	if (reuse)
    	    change_number = ip3.first();
	else
    	    change_number = ip3.second_last();
    }
    else
    {
	for (;;)
	{
	    if (reuse)
		change_number = ip3.first();
	    else
		change_number = ip3.second_last();
	    minchanum = skip_unlucky(change_number);
	    if (minchanum == change_number)
		break;
	    ip3 -= interval(change_number, minchanum - 1);
	}
    }
    trace(("return %ld;\n", change_number));
    trace(("}\n"));
    return change_number;
}