#include "exports.hpp"
#include "graph.hpp"
#include "powerlaw.hpp"
#include <algorithm>
#include <fstream>
#include <iostream>
#include <numeric>
#include <random>
#include <vector>

// Its assumed that u,v are distinct.
// Check if all four vertices are distinct
bool edgeConflicts(const Edge& e1, const Edge& e2) {
    return (e1.u == e2.u || e1.u == e2.v || e1.v == e2.u || e1.v == e2.v);
}

class SwitchChain {
  public:
    SwitchChain() : mt(std::random_device{}()), permutationDistribution(0, 2) {
        // random_device uses hardware entropy if available
        // std::random_device rd;
        // mt.seed(rd());
    }
    ~SwitchChain() {}

    bool initialize(const Graph& gstart) {
        if (gstart.edgeCount() == 0)
            return false;
        g = gstart;
        edgeDistribution.param(
            std::uniform_int_distribution<>::param_type(0, g.edgeCount() - 1));
        return true;
    }

    bool doMove() {
        Edge e1 = g.getEdge(edgeDistribution(mt));
        Edge e2 = g.getEdge(edgeDistribution(mt));
        // Keep regenerating while conflicting edges
        int timeout = 0;
        while (edgeConflicts(e1, e2)) {
            e1 = g.getEdge(edgeDistribution(mt));
            e2 = g.getEdge(edgeDistribution(mt));
            ++timeout;
            if (timeout % 100 == 0) {
                std::cerr << "Warning: sampled " << timeout
                          << " random edges but they keep conflicting.\n";
            }
        }
        // Consider one of the three possible permutations
        // 1) e1.u - e1.v and e2.u - e2.v (original)
        // 2) e1.u - e2.u and e1.v - e2.v
        // 3) e1.u - e2.v and e1.v - e2.u

        // Note that it might be that these new edges already exist
        // in which case we also reject the move
        // This is checked in exchangeEdges

        int perm = permutationDistribution(mt);
        if (perm == 0) // Original permutation
            return false;
        return g.exchangeEdges(e1, e2, perm == 1);
    }

    Graph g;
    std::mt19937 mt;
    std::uniform_int_distribution<> edgeDistribution;
    std::uniform_int_distribution<> permutationDistribution;
};

int main() {
    // Generate a random degree sequence
    std::mt19937 rng(std::random_device{}());

    // Goal:
    // Degrees follow a power-law distribution with some parameter tau
    // Expect:  #tri = const * n^{ something }
    // The goal is to find the 'something' by finding the number of triangles
    // for different values of n and tau
    float tauValues[] = {2.2f, 2.35f, 2.5f, 2.65f, 2.8f};

    Graph g;

    std::ofstream outfile("graphdata.m");
    outfile << '{';
    bool outputComma = false;

    for (int numVertices = 200; numVertices <= 1000; numVertices += 100) {
        for (float tau : tauValues) {

            DegreeSequence ds(numVertices);
            powerlaw_distribution degDist(tau, 1, numVertices);
            //std::poisson_distribution<> degDist(12);

            // For a single n,tau take samples over several instances of
            // the degree distribution
            for (int degreeSample = 0; degreeSample < 500; ++degreeSample) {
                // Generate a graph
                // might require multiple tries
                for (int i = 1; ; ++i) {
                    std::generate(ds.begin(), ds.end(),
                                  [&degDist, &rng] { return degDist(rng); });
                    if (g.createFromDegreeSequence(ds))
                        break;
                    // When 10 tries have not worked, output a warning
                    if (i % 10 == 0) {
                        std::cerr << "Warning: could not create graph from "
                                     "degree sequence. Trying again...\n";
                    }
                }

                SwitchChain chain;
                if (!chain.initialize(g)) {
                    std::cerr << "Could not initialize Markov chain.\n";
                    return 1;
                }

                std::cout << "Starting switch Markov chain with n = "
                          << numVertices << ", tau = " << tau << ". \t"
                          << std::flush;

                constexpr int mixingTime = 30000;
                constexpr int measureTime = 20000;
                constexpr int measureSkip =
                    200; // Take a sample every ... steps
                constexpr int measurements =
                    (measureTime - 1) / measureSkip + 1;
                int movesDone = 0;

                int triangles[measurements];

                for (int i = 0; i < mixingTime; ++i) {
                    if (chain.doMove())
                        ++movesDone;
                }
                for (int i = 0; i < measureTime; ++i) {
                    if (chain.doMove())
                        ++movesDone;
                    if (i % measureSkip == 0)
                        triangles[i / measureSkip] = chain.g.countTriangles();
                }

                std::cout << movesDone << '/' << mixingTime + measureTime
                          << " moves succeeded." << std::endl;

                if (outputComma)
                    outfile << ',';
                outputComma = true;

                std::sort(ds.begin(), ds.end());
                outfile << '{' << '{' << numVertices << ',' << tau << '}';
                outfile << ',' << triangles << ',' << ds << '}' << std::flush;
            }
        }
    }
    outfile << '}';
    return 0;
}