//
// Created by natty on 15.7.23.
//

#include "renderwindow.h"

#include <iostream>
#include <QPushButton>
#include <random>
#include <QComboBox>
#include <QLabel>
#include <QTimer>


std::unique_ptr<Strategy> strategyFromName(const std::string& name) {
    if (name == "Anna") {
        return std::make_unique<AnnaStrategy>();
    } else {
        throw std::runtime_error("Unknown strategy");
    }
}

RenderWindow::RenderWindow() : window(nullptr), renderer(nullptr) {
    this->mainWindowWidget = new QWidget();
    this->layout = new QVBoxLayout(this->mainWindowWidget);
    this->renderArea = new QWidget();
    this->layout->addWidget(this->renderArea);
    this->controlsLayout = new QHBoxLayout();
    this->layout->addLayout(this->controlsLayout);

    auto* strategyLabel = new QLabel("Strategy:");
    this->controlsLayout->addWidget(strategyLabel);

    this->strategySelector = new QComboBox();
    this->strategySelector->addItem("Anna");
    QObject::connect(this->strategySelector, &QComboBox::currentIndexChanged, this, &RenderWindow::resetState);
    this->controlsLayout->addWidget(this->strategySelector);

    this->controlsLayout->addStretch();

    this->distanceLabel = new QLabel("Distance: 0");
    this->controlsLayout->addWidget(this->distanceLabel);

    this->controlsLayout->addStretch();

    auto *resetButton = new QPushButton("Reset");
    QObject::connect(resetButton, &QPushButton::clicked, this, &RenderWindow::resetState);
    this->controlsLayout->addWidget(resetButton);

    auto *hardResetButton = new QPushButton("Reset (new vertices)");
    QObject::connect(hardResetButton, &QPushButton::clicked, this, &RenderWindow::hardResetState);
    this->controlsLayout->addWidget(hardResetButton);

    auto* solveButton = new QPushButton("Solve");
    QObject::connect(solveButton, &QPushButton::clicked, this, &RenderWindow::solve);
    this->controlsLayout->addWidget(solveButton);

    this->playButton = new QPushButton("Play");
    this->playButton->setCheckable(true);
    QObject::connect(this->playButton, &QPushButton::toggled, this, &RenderWindow::togglePlay);
    this->controlsLayout->addWidget(this->playButton);

    auto* stepButton = new QPushButton("Step");
    QObject::connect(stepButton, &QPushButton::clicked, this, &RenderWindow::step);
    this->controlsLayout->addWidget(stepButton);

    this->setCentralWidget(this->mainWindowWidget);

    this->animTimer = new QTimer(this);
    QObject::connect(this->animTimer, &QTimer::timeout, this, &RenderWindow::step);

    this->renderArea->setUpdatesEnabled(false);
    this->renderArea->setFixedSize(800, 800);

    SDL_SetHint(SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT, "1");

    this->window = SDL_CreateWindowFrom(reinterpret_cast<const void*>(this->renderArea->winId()));

    if (this->window == nullptr) {
        std::cerr << "Error creating SDL window: " << SDL_GetError() << std::endl;
        throw std::runtime_error("Error creating SDL window");
    }

    this->renderer = SDL_CreateRenderer(this->window, -1, SDL_RENDERER_ACCELERATED);

    if (this->renderer == nullptr) {
        std::cerr << "Error creating SDL renderer: " << SDL_GetError() << std::endl;
        throw std::runtime_error("Error creating SDL renderer");
    }

    this->hardResetState();
}

void RenderWindow::hardResetState()
{
    this->state.vertices = {};

    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_real_distribution<double> dist(100.0, 700.0);

    for (size_t i = 0; i < 100; i++) {
        this->state.vertices.push_back({
            .x = dist(gen),
            .y = dist(gen)
        });
    }

    this->resetState();
}

void RenderWindow::resetState() {
    this->animTimer->stop();

    this->strategy = strategyFromName(this->strategySelector->currentText().toStdString());

    this->state.edges = {};

    this->render();
}

void RenderWindow::paintEvent(QPaintEvent* event)
{
    QMainWindow::paintEvent(event);
    this->render();
}

void RenderWindow::render() {
    SDL_SetRenderDrawColor(this->renderer, 0, 0, 0, 255);
    SDL_RenderClear(this->renderer);

    SDL_SetRenderDrawColor(this->renderer, 255, 255, 255, 255);

    for (auto& vertex : this->state.vertices) {
        SDL_Rect rect = {
            static_cast<int>(vertex.x - 3),
            static_cast<int>(vertex.y - 3),
            6,
            6
        };

        SDL_RenderFillRect(this->renderer, &rect);
    }

    double dist = 0.0;

    for (auto& edge : this->state.edges) {
        SDL_SetRenderDrawColor(this->renderer, 255, 255, 0, 255);

        dist += std::hypot(
            this->state.vertices[edge.from].x - this->state.vertices[edge.to].x,
            this->state.vertices[edge.from].y - this->state.vertices[edge.to].y
        );

        SDL_RenderDrawLine(
            this->renderer,
            static_cast<int>(this->state.vertices[edge.from].x),
            static_cast<int>(this->state.vertices[edge.from].y),
            static_cast<int>(this->state.vertices[edge.to].x),
            static_cast<int>(this->state.vertices[edge.to].y)
        );
    }

    this->distanceLabel->setText(QString("Distance: %1").arg(dist));

    SDL_RenderPresent(this->renderer);
}

void RenderWindow::step() {
    if (this->strategy->step(this->state)) {
        this->animTimer->stop();
        this->playButton->setChecked(false);
    }
    this->render();
}

void RenderWindow::solve() {
    if (this->state.edges.size() == this->state.vertices.size()) {
        this->resetState();
    }

    while (!this->strategy->step(this->state)) {}

    this->render();
}

RenderWindow::~RenderWindow() {
    if (this->renderer != nullptr) {
        SDL_DestroyRenderer(this->renderer);
        this->renderer = nullptr;
    }

    if (this->window != nullptr) {
        SDL_DestroyWindow(this->window);
        this->window = nullptr;
    }
}

void RenderWindow::togglePlay(bool play)
{
    if (play) {
        if (this->state.edges.size() == this->state.vertices.size()) {
            this->resetState();
        }

        this->animTimer->start(50);
    } else {
        this->animTimer->stop();
    }
}

bool AnnaStrategy::step(State& state) {
    if (!this->init) {
        this->init = true;
        this->unvisited = {};
        for (size_t i = 0; i < state.vertices.size(); i++) {
            this->unvisited.push_back(i);
        }
        std::shuffle(this->unvisited.begin(), this->unvisited.end(), std::mt19937(std::random_device()()));
    }

    if (state.vertices.size() < 2) {
        return true;
    }

    if (state.vertices.size() == 2) {
        state.edges = {{
           .from = 0,
           .to = 1
        }};
        return true;
    }

    if (this->unvisited.empty())
        return true;

    if (state.vertices.size() - this->unvisited.size() == 0) {
        size_t a, b, c;
        a = this->unvisited.back();
        this->unvisited.pop_back();
        b = this->unvisited.back();
        this->unvisited.pop_back();
        c = this->unvisited.back();
        this->unvisited.pop_back();

        state.edges = {{
            .from = a,
            .to = b
        }, {
            .from = b,
            .to = c
        }, {
            .from = c,
            .to = a
        }};

        return false;
    }

    size_t i = this->unvisited.back();
    this->unvisited.pop_back();

    const auto& vertex = state.vertices[i];

    auto& closest_edge = *std::min_element(state.edges.begin(), state.edges.end(), [&state, &vertex](const Edge& a, const Edge& b) {
        return a.distanceOf(state, vertex) < b.distanceOf(state, vertex);
    });

    size_t old_to = closest_edge.to;
    closest_edge.to = i;
    state.edges.push_back({
        .from = i,
        .to = old_to
    });

    return false;
}

double Edge::distanceOf(const State& state, const Vertex& vertex) const {
    // Adapted from https://stackoverflow.com/a/1501725
    auto x1 = state.vertices[this->from].x;
    auto y1 = state.vertices[this->from].y;
    auto x2 = state.vertices[this->to].x;
    auto y2 = state.vertices[this->to].y;

    auto dx = x2 - x1;
    auto dy = y2 - y1;

    auto l2 = dx * dx + dy * dy;

    constexpr auto epsilon = 0.0001;

    if (l2 < epsilon)
        return std::hypot(vertex.x - x1, vertex.y - y1);

    const double t = std::max(0.0, std::min(1.0, ((vertex.x - x1) * dx + (vertex.y - y1) * dy) / l2));

    const double projection_x = x1 + t * dx;
    const double projection_y = y1 + t * dy;

    return std::hypot(vertex.x - projection_x, vertex.y - projection_y);
}