/*
	 * Copyright 2013-2026 the Pacemaker project contributors
	 *
	 * The version control history for this file may have further details.
	 *
	 * This source code is licensed under the GNU General Public License version 2
	 * or later (GPLv2+) WITHOUT ANY WARRANTY.
	 */
	
	#include <crm_internal.h>
	
	#include <stdbool.h>
	
	#include <crm/cluster.h>
	#include <crm/cluster/election_internal.h>
	#include <crm/common/xml.h>
	
	#include "pacemaker-attrd.h"
	
	static char *peer_writer = NULL;
	
	static void
	attrd_election_cb(pcmk_cluster_t *cluster)
	{
	    attrd_declare_winner();
	
	    /* Update the peers after an election */
	    attrd_peer_sync(NULL);
	
	    attrd_erase_removed_peer_attributes();
	
	    /* After winning an election, update the CIB with the values of all
	     * attributes as the winner knows them.
	     */
	    attrd_write_attributes(attrd_write_all);
	}
	
	void
	attrd_election_init(void)
	{
	    election_init(attrd_cluster, attrd_election_cb);
	}
	
	void
	attrd_start_election_if_needed(void)
	{
	    if ((peer_writer == NULL)
	        && (election_state(attrd_cluster) != election_in_progress)
	        && !attrd_shutting_down()) {
	
	        pcmk__info("Starting an election to determine the writer");
	        election_vote(attrd_cluster);
	    }
	}
	
	bool
	attrd_election_won(void)
	{
	    return (election_state(attrd_cluster) == election_won);
	}
	
	void
	attrd_handle_election_op(const pcmk__node_status_t *peer, xmlNode *xml)
	{
	    enum election_result rc = 0;
	    enum election_result previous = election_state(attrd_cluster);
	
	    pcmk__xe_set(xml, PCMK__XA_SRC, peer->name);
	
	    // Don't become writer if we're shutting down
	    rc = election_count_vote(attrd_cluster, xml, !attrd_shutting_down());
	
	    switch(rc) {
	        case election_start:
	            pcmk__debug("Unsetting writer (was %s) and starting new election",
	                        pcmk__s(peer_writer, "unset"));
	            g_clear_pointer(&peer_writer, free);
	            election_vote(attrd_cluster);
	            break;
	
	        case election_lost:
	            /* The election API should really distinguish between "we just lost
	             * to this peer" and "we already lost previously, and we are
	             * discarding this vote for some reason", but it doesn't.
	             *
	             * In the first case, we want to tentatively set the peer writer to
	             * this peer, even though another peer may eventually win (which we
	             * will learn via attrd_check_for_new_writer()), so
	             * attrd_start_election_if_needed() doesn't start a new election.
	             *
	             * Approximate a test for that case as best as possible.
	             */
	            if ((peer_writer == NULL) || (previous != election_lost)) {
	                pcmk__str_update(&peer_writer, peer->name);
	                pcmk__debug("Election lost, presuming %s is writer for now",
	                            peer_writer);
	            }
	            break;
	
	        case election_in_progress:
	            election_check(attrd_cluster);
	            break;
	
	        default:
	            pcmk__info("Ignoring election op from %s due to error", peer->name);
	            break;
	    }
	}
	
	bool
	attrd_check_for_new_writer(const pcmk__node_status_t *peer, const xmlNode *xml)
	{
	    int peer_state = 0;
	
	    pcmk__xe_get_int(xml, PCMK__XA_ATTR_WRITER, &peer_state);
	    if (peer_state == election_won) {
	        if ((election_state(attrd_cluster) == election_won)
	            && !pcmk__str_eq(peer->name, attrd_cluster->priv->node_name,
	                             pcmk__str_casei)) {
	            pcmk__notice("Detected another attribute writer (%s), starting new "
	                         "election",
	                         peer->name);
	            election_vote(attrd_cluster);
	
	        } else if (!pcmk__str_eq(peer->name, peer_writer, pcmk__str_casei)) {
	            pcmk__notice("Recorded new attribute writer: %s (was %s)",
	                         peer->name, pcmk__s(peer_writer, "unset"));
	            pcmk__str_update(&peer_writer, peer->name);
	        }
	    }
	    return (peer_state == election_won);
	}
	
	void
	attrd_declare_winner(void)
	{
	    pcmk__notice("Recorded local node as attribute writer (was %s)",
	                 pcmk__s(peer_writer, "unset"));
	    pcmk__str_update(&peer_writer, attrd_cluster->priv->node_name);
	}
	
	void
	attrd_remove_voter(const pcmk__node_status_t *peer)
	{
	    election_remove(attrd_cluster, peer->name);

	    if ((peer_writer != NULL)
	        && pcmk__str_eq(peer->name, peer_writer, pcmk__str_casei)) {
	

	        g_clear_pointer(&peer_writer, free);
	        pcmk__notice("Lost attribute writer %s", peer->name);
	
	        /* Clear any election dampening in effect. Otherwise, if the lost writer
	         * had just won, the election could fizzle out with no new writer.
	         */
	        election_clear_dampening(attrd_cluster);
	
	        /* If the writer received attribute updates during its shutdown, it will
	         * not have written them to the CIB. Ensure we get a new writer so they
	         * are written out. This means that every node that sees the writer
	         * leave will start a new election, but that's better than losing
	         * attributes.
	         */
	        attrd_start_election_if_needed();
	
	    /* If an election is in progress, we need to call election_check(), in case
	     * this lost peer is the only one that hasn't voted, otherwise the election
	     * would be pending until it's timed out.
	     */
	    } else if (election_state(attrd_cluster) == election_in_progress) {
	       pcmk__debug("Checking election status upon loss of voter %s",
	                   peer->name);
	       election_check(attrd_cluster);
	    }
	}
	
	void
	attrd_xml_add_writer(xmlNode *xml)
	{
	    pcmk__xe_set_int(xml, PCMK__XA_ATTR_WRITER, election_state(attrd_cluster));
	}