#include "core/rendering/pixel_reveal.hpp"

#include <algorithm>  // Para min
#include <numeric>    // Para iota
#include <random>     // Para mt19937, shuffle

#include "core/rendering/surface.hpp"  // Para Surface
#include "utils/utils.hpp"             // Para PaletteColor

// Constructor
PixelReveal::PixelReveal(int width, int height, float pixels_per_second, float step_duration, int num_steps)
    : cover_surface_(std::make_shared<Surface>(width, height)),
      reveal_order_(height),
      row_step_(height, 0),
      width_(width),
      height_(height),
      pixels_per_second_(pixels_per_second),
      step_duration_(step_duration),
      num_steps_(num_steps) {
    // Rellena la máscara con negro sólido
    cover_surface_->clear(static_cast<Uint8>(PaletteColor::BLACK));

    // Genera el orden aleatorio de columnas por fila usando la fila como semilla (reproducible)
    for (int r = 0; r < height_; r++) {
        reveal_order_[r].resize(width_);
        std::iota(reveal_order_[r].begin(), reveal_order_[r].end(), 0);
        std::mt19937 rng(static_cast<unsigned int>(r));
        std::shuffle(reveal_order_[r].begin(), reveal_order_[r].end(), rng);
    }
}

// Destructor
PixelReveal::~PixelReveal() = default;

// Actualiza el estado del revelado
void PixelReveal::update(float time_active) {
    const auto TRANSPARENT = static_cast<Uint8>(PaletteColor::TRANSPARENT);

    for (int r = 0; r < height_; r++) {
        const float T_START = static_cast<float>(r) / pixels_per_second_;
        const float TIME_IN_ROW = time_active - T_START;

        if (TIME_IN_ROW < 0.0F) {
            continue;  // Esta fila aún no ha empezado
        }

        const int STEPS = std::min(num_steps_, static_cast<int>(TIME_IN_ROW / step_duration_));

        if (STEPS > row_step_[r]) {
            // Revela los píxeles de los pasos pendientes
            for (int step = row_step_[r]; step < STEPS; step++) {
                const int START_IDX = step * width_ / num_steps_;
                const int END_IDX = (step == num_steps_ - 1) ? width_ : (step + 1) * width_ / num_steps_;

                for (int idx = START_IDX; idx < END_IDX; idx++) {
                    const int COL = reveal_order_[r][idx];
                    cover_surface_->putPixel(COL, r, TRANSPARENT);
                }
            }
            row_step_[r] = STEPS;
        }
    }
}

// Dibuja la máscara en la posición indicada
void PixelReveal::render(int dst_x, int dst_y) const {
    cover_surface_->render(dst_x, dst_y);
}

// Indica si el revelado ha completado todas las filas
bool PixelReveal::isComplete() const {
    for (const int step : row_step_) {
        if (step < num_steps_) {
            return false;
        }
    }
    return true;
}