#include "components/TrailComponent.hpp"

#include "Entity.hpp"
#include "components/TransformComponent.hpp"

#include <algorithm>
#include <cmath>

void TrailComponent::Setup() {
    points.clear();
    elapsed = 0.0f;
    lastSampleAt = 0.0f;

    auto transform = entity->GetComponent<TransformComponent>();
    if (!transform) {
        return;
    }

    points.push_back({transform->get().x, transform->get().y, elapsed});
}

void TrailComponent::Update(float dt) {
    elapsed += dt;

    auto transform = entity->GetComponent<TransformComponent>();
    if (!transform) {
        return;
    }

    while (!points.empty() && (elapsed - points.front().createdAt) > pointLifetime) {
        points.pop_front();
    }

    const float x = transform->get().x;
    const float y = transform->get().y;
    if (points.empty()) {
        points.push_back({x, y, elapsed});
        lastSampleAt = elapsed;
        return;
    }

    const Point &last = points.back();
    const float dx = x - last.x;
    const float dy = y - last.y;

    // check if we've moved far enough from the last point or if enough time has passed to warrant a
    // new sample, for smoother trails when the probe is moving slowly
    const bool movedEnough = (dx * dx + dy * dy) >= (sampleDistance * sampleDistance);
    const bool waitedEnough = (elapsed - lastSampleAt) >= sampleInterval;
    if (movedEnough || waitedEnough) {
        points.push_back({x, y, elapsed});
        lastSampleAt = elapsed;
    } else {
        points.back().x = x;
        points.back().y = y;
        points.back().createdAt = elapsed;
    }

    if (points.size() > maxPoints) {
        while (points.size() > maxPoints) {
            points.pop_front();
        }
    }

    Draw();
}

void TrailComponent::Cleanup() {
    points.clear();
    elapsed = 0.0f;
    lastSampleAt = 0.0f;
}

void TrailComponent::Draw() const {
    if (points.size() < 2 || pointLifetime <= 0.0f) {
        return;
    }

    for (size_t i = 1; i < points.size(); ++i) {
        const Point &a = points[i - 1];
        const Point &b = points[i];

        const float ageA = elapsed - a.createdAt;
        const float ageB = elapsed - b.createdAt;
        const float lifeNormA = std::clamp(1.0f - (ageA / pointLifetime), 0.0f, 1.0f);
        const float lifeNormB = std::clamp(1.0f - (ageB / pointLifetime), 0.0f, 1.0f);
        const float lifeNorm = 0.5f * (lifeNormA + lifeNormB);

        Color c = color;
        c.a = (unsigned char)((float)(color.a) * lifeNorm);

        DrawLineEx({a.x, a.y}, {b.x, b.y}, lineWidth, c);
    }
}