/******************************************************************************
 * kway_graph_refinement_core.cpp
 * *
 * Source of KaHIP -- Karlsruhe High Quality Partitioning.
 * Christian Schulz <christian.schulz.phone@gmail.com>
 *****************************************************************************/

#include <algorithm>

#include "data_structure/priority_queues/bucket_pq.h"
#include "data_structure/priority_queues/maxNodeHeap.h"
#include "kway_graph_refinement_core.h"
#include "kway_stop_rule.h"
#include "quality_metrics.h"
#include "random_functions.h"

kway_graph_refinement_core::kway_graph_refinement_core() {
}

kway_graph_refinement_core::~kway_graph_refinement_core() {

}
EdgeWeight kway_graph_refinement_core::single_kway_refinement_round(PartitionConfig & config, 
                                                                    graph_access & G, 
                                                                    complete_boundary & boundary, 
                                                                    boundary_starting_nodes & start_nodes, 
                                                                    int step_limit, 
                                                                    vertex_moved_hashtable & moved_idx) {
        std::unordered_map<PartitionID, PartitionID> touched_blocks;
        return single_kway_refinement_round_internal(config, G, boundary, start_nodes, 
                                                     step_limit, moved_idx, false, touched_blocks);
}

EdgeWeight kway_graph_refinement_core::single_kway_refinement_round(PartitionConfig & config, 
                                                                    graph_access & G, 
                                                                    complete_boundary & boundary, 
                                                                    boundary_starting_nodes & start_nodes, 
                                                                    int step_limit, 
                                                                    vertex_moved_hashtable & moved_idx,
                                                                    std::unordered_map<PartitionID, PartitionID> & touched_blocks) {

        return single_kway_refinement_round_internal(config, G, boundary, start_nodes, 
                                                     step_limit, moved_idx, true, touched_blocks);
}


EdgeWeight kway_graph_refinement_core::single_kway_refinement_round_internal(PartitionConfig & config, 
                                                                    graph_access & G, 
                                                                    complete_boundary & boundary, 
                                                                    boundary_starting_nodes & start_nodes, 
                                                                    int step_limit,
                                                                    vertex_moved_hashtable & moved_idx,
                                                                    bool compute_touched_partitions,
                                                                    std::unordered_map<PartitionID, PartitionID> &  touched_blocks) {

        commons = kway_graph_refinement_commons::getInstance(config);
        refinement_pq* queue = NULL;
        if(config.use_bucket_queues) {
                EdgeWeight max_degree = G.getMaxDegree();
                queue                 = new bucket_pq(max_degree);
        } else {
                queue                 = new maxNodeHeap(); 
        }

        init_queue_with_boundary(config, G, start_nodes, queue, moved_idx);  
        
        if(queue->empty()) {delete queue; return 0;}

        std::vector<NodeID> transpositions;
        std::vector<PartitionID> from_partitions;
        std::vector<PartitionID> to_partitions;

        int max_number_of_swaps = (int)(G.number_of_nodes());
        int min_cut_index       = -1;

        EdgeWeight cut         = std::numeric_limits<int>::max()/2; // so we dont need to compute the edge cut
        EdgeWeight initial_cut = cut;

        //roll forwards
        EdgeWeight best_cut = cut;
        int number_of_swaps = 0;
        int movements       = 0;

        kway_stop_rule* stopping_rule = NULL;
        switch(config.kway_stop_rule) {
                case KWAY_SIMPLE_STOP_RULE: 
                        stopping_rule = new kway_simple_stop_rule(config);
                        break;
                case KWAY_ADAPTIVE_STOP_RULE: 
                        stopping_rule = new kway_adaptive_stop_rule(config);
                        break;

        }

        for(number_of_swaps = 0, movements = 0; movements < max_number_of_swaps; movements++, number_of_swaps++) {
                if( queue->empty() ) break;
                if( stopping_rule->search_should_stop(min_cut_index, number_of_swaps, step_limit) ) break;

                Gain gain = queue->maxValue();
                NodeID node = queue->deleteMax();

#ifndef NDEBUG
                PartitionID maxgainer;
                EdgeWeight ext_degree;
                ASSERT_TRUE(moved_idx[node].index == NOT_MOVED);
                ASSERT_EQ(gain, commons->compute_gain(G, node, maxgainer, ext_degree));
                ASSERT_TRUE(ext_degree > 0);
#endif

                PartitionID from = G.getPartitionIndex(node); 
                bool successfull = move_node(config, G, node, moved_idx, queue, boundary);

                if(successfull) {
                        cut -= gain;
                        stopping_rule->push_statistics(gain);

                        bool accept_equal = random_functions::nextBool();
                        if( cut < best_cut || ( cut == best_cut && accept_equal )) {
                                best_cut = cut;
                                min_cut_index = number_of_swaps;
                                if(cut < best_cut)
                                        stopping_rule->reset_statistics();
                        }

                        from_partitions.push_back(from);
                        to_partitions.push_back(G.getPartitionIndex(node));
                        transpositions.push_back(node);
                } else {
                        number_of_swaps--; //because it wasnt swaps
                }
                moved_idx[node].index = MOVED;
                ASSERT_TRUE(boundary.assert_bnodes_in_boundaries());
                ASSERT_TRUE(boundary.assert_boundaries_are_bnodes());

        } 

        ASSERT_TRUE(boundary.assert_bnodes_in_boundaries());
        ASSERT_TRUE(boundary.assert_boundaries_are_bnodes());

        //roll backwards
        for(number_of_swaps--; number_of_swaps>min_cut_index; number_of_swaps--) {
                ASSERT_TRUE(transpositions.size() > 0);

                NodeID node = transpositions.back();
                transpositions.pop_back();

                PartitionID to = from_partitions.back();
                from_partitions.pop_back();
                to_partitions.pop_back();

                move_node_back(config, G, node, to,  moved_idx, queue, boundary);
        }

       
        //reconstruct the touched partitions
        if(compute_touched_partitions) {
                ASSERT_EQ(from_partitions.size(), to_partitions.size());
                for(unsigned i = 0; i < from_partitions.size(); i++) {
                        touched_blocks[from_partitions[i]] = from_partitions[i];
                        touched_blocks[to_partitions[i]]   = to_partitions[i];
                }
        }

        ASSERT_TRUE(boundary.assert_bnodes_in_boundaries());
        ASSERT_TRUE(boundary.assert_boundaries_are_bnodes());

        delete queue;
        delete stopping_rule;
        return initial_cut - best_cut; 
}

void kway_graph_refinement_core::init_queue_with_boundary(const PartitionConfig & config,
                graph_access & G,
                std::vector<NodeID> & bnd_nodes,
                refinement_pq * queue, vertex_moved_hashtable & moved_idx) {

        if(config.permutation_during_refinement == PERMUTATION_QUALITY_FAST) {
                random_functions::permutate_vector_fast(bnd_nodes, false);
        } else if(config.permutation_during_refinement == PERMUTATION_QUALITY_GOOD) {
                random_functions::permutate_vector_good(bnd_nodes, false);
        }

        for( unsigned int i = 0; i < bnd_nodes.size(); i++) {
                NodeID node = bnd_nodes[i];

                if( moved_idx.find(node) == moved_idx.end() ) {
                        PartitionID max_gainer;
                        EdgeWeight ext_degree;
                        //compute gain
                        Gain gain = commons->compute_gain(G, node, max_gainer, ext_degree);
                        queue->insert(node, gain);
                        moved_idx[node].index = NOT_MOVED;
                }
        }
}


void kway_graph_refinement_core::move_node_back(PartitionConfig & config, 
                graph_access & G, 
                NodeID & node,
                PartitionID & to, 
                vertex_moved_hashtable & moved_idx, 
                refinement_pq * queue, 
                complete_boundary & boundary) {

        PartitionID from = G.getPartitionIndex(node);
        G.setPartitionIndex(node, to);        

        boundary_pair pair;
        pair.k   = config.k;
        pair.lhs = from;
        pair.rhs = to;

        //update all boundaries
        boundary.postMovedBoundaryNodeUpdates(node, &pair, true, true);

        NodeWeight this_nodes_weight = G.getNodeWeight(node);
        boundary.setBlockNoNodes(from, boundary.getBlockNoNodes(from)-1);
        boundary.setBlockNoNodes(to,   boundary.getBlockNoNodes(to)+1);
        boundary.setBlockWeight( from, boundary.getBlockWeight(from)-this_nodes_weight);
        boundary.setBlockWeight( to,   boundary.getBlockWeight(to)+this_nodes_weight);
}

