// playfield.cpp - Implementació del fons del playfield
// © 2026 JailDesigner

#include "core/graphics/playfield.hpp"

#include <algorithm>
#include <cmath>
#include <cstdlib>

#include "core/defaults.hpp"
#include "core/rendering/line_renderer.hpp"

namespace Graphics {

    namespace {

        // Easing cubic-out: t → 1 - (1-t)^3. Decelera prop del final.
        auto easeOutCubic(float t) -> float {
            const float INV = 1.0F - t;
            return 1.0F - (INV * INV * INV);
        }

    }  // namespace

    Playfield::Playfield(Rendering::Renderer* renderer)
        : renderer_(renderer) {
        buildLines();
    }

    void Playfield::update(float delta_time) {
        elapsed_s_ += delta_time;
    }

    void Playfield::buildLines() {
        const SDL_FRect& zona = Defaults::Zones::PLAYAREA;
        const float CELL_W = zona.w / static_cast<float>(Defaults::Playfield::COLUMNS);
        const float CELL_H = zona.h / static_cast<float>(Defaults::Playfield::ROWS);
        const float SUB_W = CELL_W / static_cast<float>(Defaults::Playfield::SUBDIVISIONS);
        const float SUB_H = CELL_H / static_cast<float>(Defaults::Playfield::SUBDIVISIONS);
        const int SUB_VERTS = Defaults::Playfield::COLUMNS * Defaults::Playfield::SUBDIVISIONS;
        const int SUB_HORIZ = Defaults::Playfield::ROWS * Defaults::Playfield::SUBDIVISIONS;

        std::vector<Line> verticals;
        std::vector<Line> horizontals;

        // Verticals: posicions i ∈ [1, SUB_VERTS-1].
        for (int i = 1; i < SUB_VERTS; i++) {
            const float X = zona.x + (static_cast<float>(i) * SUB_W);
            const bool IS_MAIN = (i % Defaults::Playfield::SUBDIVISIONS) == 0;
            const float BRIGHTNESS = IS_MAIN
                ? Defaults::Playfield::GRID_BRIGHTNESS
                : Defaults::Playfield::SUBGRID_BRIGHTNESS;
            verticals.push_back(Line{
                .start = {.x = X, .y = zona.y},
                .end = {.x = X, .y = zona.y + zona.h},
                .brightness = BRIGHTNESS,
                .spawn_time_s = 0.0F});
        }

        // Horitzontals: posicions j ∈ [1, SUB_HORIZ-1].
        for (int j = 1; j < SUB_HORIZ; j++) {
            const float Y = zona.y + (static_cast<float>(j) * SUB_H);
            const bool IS_MAIN = (j % Defaults::Playfield::SUBDIVISIONS) == 0;
            const float BRIGHTNESS = IS_MAIN
                ? Defaults::Playfield::GRID_BRIGHTNESS
                : Defaults::Playfield::SUBGRID_BRIGHTNESS;
            horizontals.push_back(Line{
                .start = {.x = zona.x, .y = Y},
                .end = {.x = zona.x + zona.w, .y = Y},
                .brightness = BRIGHTNESS,
                .spawn_time_s = 0.0F});
        }

        // Ona diagonal: la línia esquerra/superior naix a t=0 i les següents
        // propaguen cap a la dreta/inferior, en paral·lel. Verticals i
        // horitzontals comparteixen la finestra temporal així el front arriba
        // a la cantonada inferior-dreta alhora.
        const float SPAWN_WINDOW =
            Defaults::Playfield::TOTAL_ANIMATION_DURATION_S - Defaults::Playfield::LINE_GROWTH_DURATION_S;
        const int NUM_V = static_cast<int>(verticals.size());
        const int NUM_H = static_cast<int>(horizontals.size());
        const float INTERVAL_V = (NUM_V > 1) ? SPAWN_WINDOW / static_cast<float>(NUM_V - 1) : 0.0F;
        const float INTERVAL_H = (NUM_H > 1) ? SPAWN_WINDOW / static_cast<float>(NUM_H - 1) : 0.0F;

        lines_.clear();
        lines_.reserve(verticals.size() + horizontals.size());

        for (int i = 0; i < NUM_V; i++) {
            verticals[i].spawn_time_s = static_cast<float>(i) * INTERVAL_V;
            lines_.push_back(verticals[i]);
        }
        for (int i = 0; i < NUM_H; i++) {
            horizontals[i].spawn_time_s = static_cast<float>(i) * INTERVAL_H;
            lines_.push_back(horizontals[i]);
        }
    }

    auto Playfield::computeLineProgress(const Line& line) const -> float {
        const float LINE_ELAPSED = elapsed_s_ - line.spawn_time_s;
        return std::clamp(LINE_ELAPSED / Defaults::Playfield::LINE_GROWTH_DURATION_S, 0.0F, 1.0F);
    }

    void Playfield::draw() const {
        for (const auto& line : lines_) {
            const float RAW_P = computeLineProgress(line);
            if (RAW_P <= 0.0F) {
                continue;
            }
            const float P = easeOutCubic(RAW_P);

            const float DX = line.end.x - line.start.x;
            const float DY = line.end.y - line.start.y;
            const float CURRENT_X = line.start.x + (DX * P);
            const float CURRENT_Y = line.start.y + (DY * P);

            // Tram base (brillo de la línia).
            Rendering::linea(
                renderer_,
                static_cast<int>(line.start.x),
                static_cast<int>(line.start.y),
                static_cast<int>(CURRENT_X),
                static_cast<int>(CURRENT_Y),
                line.brightness);

            // Cap brillant mentre creix: l'últim tram de la línia es repinta més brillant.
            if (P < 1.0F) {
                const float LENGTH = std::sqrt((DX * DX) + (DY * DY));
                if (LENGTH > 0.0F) {
                    const float HEAD_T = std::max(0.0F, P - (Defaults::Playfield::HEAD_LENGTH_PX / LENGTH));
                    const float HEAD_X = line.start.x + (DX * HEAD_T);
                    const float HEAD_Y = line.start.y + (DY * HEAD_T);
                    Rendering::linea(
                        renderer_,
                        static_cast<int>(HEAD_X),
                        static_cast<int>(HEAD_Y),
                        static_cast<int>(CURRENT_X),
                        static_cast<int>(CURRENT_Y),
                        Defaults::Playfield::HEAD_BRIGHTNESS);
                }
            }
        }
    }

}  // namespace Graphics