/*

   igraph library.

   Copyright (C) 2024  The igraph development team

   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 2 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, write to the Free Software

   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

   02110-1301 USA

*/

#include <igraph.h>

#include <cstdlib>

// Verify that all communities are connected subgraphs

void check_communities_are_connected(const igraph_t *graph, const igraph_vector_int_t *membership) {

    igraph_vector_int_t memb, comp, map;

    igraph_int_t vcount = igraph_vcount(graph);

    igraph_int_t no;

    igraph_vector_int_init_copy(&memb, membership);

    igraph_reindex_membership(&memb, NULL, &no);

    igraph_vector_int_init(&map, no);

    igraph_vector_int_fill(&map, -1);

    igraph_vector_int_init(&comp, 0);

    igraph_connected_components(graph, &comp, NULL, NULL, IGRAPH_WEAK);

    for (igraph_int_t v=0; v < vcount; v++) {

        if (VECTOR(map)[ VECTOR(memb)[v] ] == -1) {

            VECTOR(map)[ VECTOR(memb)[v] ] = VECTOR(comp)[v];

        } else {

            IGRAPH_ASSERT(VECTOR(map)[ VECTOR(memb)[v] ] == VECTOR(comp)[v]);

        }

    }

    igraph_vector_int_destroy(&comp);

    igraph_vector_int_destroy(&map);

    igraph_vector_int_destroy(&memb);

}

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {

    igraph_t graph;

    igraph_vector_int_t edges;

    igraph_set_warning_handler(igraph_warning_handler_ignore);

    if (Size % 2 == 0 || Size > 512+1 || Size < 1) {

        return 0;

    }

    igraph_vector_int_init(&edges, Size-1);

    for (size_t i=0; i < Size-1; ++i) {

        VECTOR(edges)[i] = Data[i+1];

    }

    igraph_rng_seed(igraph_rng_default(), 42);

    if (igraph_create(&graph, &edges, Data[0], IGRAPH_DIRECTED) == IGRAPH_SUCCESS) {

        igraph_matrix_int_t merges, im;

        igraph_matrix_t mat;

        igraph_vector_int_t membership, membership2, iv, iv2;

        igraph_vector_t mv, v;

        igraph_real_t m, r;

        igraph_int_t i;

        igraph_bool_t b;

        /* Limit graph size for the sake of performance. */

        if (igraph_vcount(&graph) <= 64) {

            igraph_matrix_int_init(&merges, 0, 0);

            igraph_matrix_int_init(&im, 0, 0);

            igraph_matrix_init(&mat, 0, 0);

            igraph_vector_int_init(&membership, 0);

            igraph_vector_int_init(&membership2, 0);

            igraph_vector_int_init(&iv, 0);

            igraph_vector_int_init(&iv2, 0);

            igraph_vector_init(&mv, 0);

            igraph_vector_init(&v, 0);

            // The IGRAPH_LPA_FAST version is temporarily switched to undirected until

            // the reason for the bad performance / infinite loop in the directed version

            // is debugged. See https://github.com/igraph/igraph/issues/2608

            igraph_community_label_propagation(&graph, &membership, IGRAPH_ALL, NULL, NULL, NULL, IGRAPH_LPA_FAST);

            igraph_community_label_propagation(&graph, &membership, IGRAPH_OUT, NULL, NULL, NULL, IGRAPH_LPA_RETENTION);

            igraph_community_label_propagation(&graph, &membership, IGRAPH_OUT, NULL, NULL, NULL, IGRAPH_LPA_DOMINANCE);

            igraph_community_walktrap(&graph, NULL, 3, &merges, &mv, &membership);

            igraph_community_edge_betweenness(&graph, &iv, &v, &merges, &iv2, &mv, &membership2, IGRAPH_DIRECTED, NULL, NULL);

            igraph_community_leiden(&graph, NULL, NULL, NULL, 1.5, 0.01, false, 2, &membership, &i, &r);

            check_communities_are_connected(&graph, &membership);

            // Take the opportunity to run functions that can use the output of community detection.

            {

                igraph_community_comparison_t method[] = {

                    IGRAPH_COMMCMP_VI,

                    IGRAPH_COMMCMP_NMI,

                    IGRAPH_COMMCMP_SPLIT_JOIN,

                    IGRAPH_COMMCMP_RAND,

                    IGRAPH_COMMCMP_ADJUSTED_RAND

                };

                for (size_t i=0; i < sizeof(method) / sizeof(method[0]); i++) {

                    if ((method[i] == IGRAPH_COMMCMP_RAND ||

                         method[i] == IGRAPH_COMMCMP_ADJUSTED_RAND) &&

                        igraph_vcount(&graph) < 2) {

                        continue;

                    }

                    igraph_compare_communities(&membership, &membership2, &r, method[i]);

                }

            }

            {

                igraph_t graph2;

                igraph_copy(&graph2, &graph);

                igraph_contract_vertices(&graph2, &membership, NULL);

                igraph_destroy(&graph2);

            }

            igraph_modularity(&graph, &membership, NULL, 1.5, IGRAPH_UNDIRECTED, &m);

            igraph_modularity_matrix(&graph, NULL, 0.75, &mat, IGRAPH_DIRECTED);

            igraph_assortativity_nominal(&graph, NULL, &membership, &r, IGRAPH_DIRECTED, true);

            igraph_simplify(&graph, true, true, NULL);

            igraph_community_voronoi(&graph, &membership, &iv, &m, NULL, NULL, IGRAPH_OUT, 1.0);

            igraph_to_undirected(&graph, IGRAPH_TO_UNDIRECTED_COLLAPSE, NULL);

            igraph_community_fastgreedy(&graph, NULL, &merges, &mv, &membership);

            igraph_community_leiden(&graph, NULL, NULL, NULL, 1.5, 0.01, false, 2, &membership, &i, &r);

            check_communities_are_connected(&graph, &membership);

            igraph_community_multilevel(&graph, NULL, 0.8, &membership, &im, &mv);

            igraph_is_connected(&graph, &b, IGRAPH_WEAK);

            if (b) {

                igraph_int_t no_comm = 4;

                if (no_comm > igraph_vcount(&graph)) {

                    no_comm = igraph_vcount(&graph);

                }

                igraph_community_fluid_communities(&graph, no_comm, &membership);

            }

            igraph_vector_destroy(&v);

            igraph_vector_destroy(&mv);

            igraph_vector_int_destroy(&iv2);

            igraph_vector_int_destroy(&iv);

            igraph_vector_int_destroy(&membership2);

            igraph_vector_int_destroy(&membership);

            igraph_matrix_destroy(&mat);

            igraph_matrix_int_destroy(&im);

            igraph_matrix_int_destroy(&merges);

        }

        igraph_destroy(&graph);

    }

    igraph_vector_int_destroy(&edges);

    IGRAPH_ASSERT(IGRAPH_FINALLY_STACK_EMPTY);

    return 0;  // Non-zero return values are reserved for future use.

}