#include "core/chain.hpp"

namespace effector {

Image renderChain(const std::vector<ChainStage>& stages, const std::vector<Image>& sources,
                  int width, int height, Rng& rng) {
    if (stages.empty()) throw EffectError("The effect chain is empty.");

    Image image;
    for (std::size_t i = 0; i < stages.size(); ++i) {
        const auto& stage = stages[i];
        if (!stage.effect) throw EffectError("The effect chain has an empty stage.");

        auto values = stage.effect->defaults();
        for (const auto& [key, value] : stage.values) values[key] = value;

        if (i == 0) {
            image = stage.effect->render(sources, width, height, rng, values);
        } else {
            // Feeding the previous result back in as the only source is what
            // cascading means here; effects need to know nothing about it.
            const std::vector<Image> previous = {std::move(image)};
            image = stage.effect->render(previous, width, height, rng, values);
        }
    }
    return image;
}

bool chainNeedsSources(const std::vector<ChainStage>& stages) {
    if (stages.empty() || !stages.front().effect) return false;
    return stages.front().effect->needsSources();
}

std::string chainTitle(const std::vector<ChainStage>& stages) {
    std::string text;
    for (const auto& stage : stages) {
        if (!stage.effect) continue;
        if (!text.empty()) text += " → ";
        text += stage.effect->title();
    }
    return text;
}

std::string chainSlug(const std::vector<ChainStage>& stages) {
    std::string text;
    for (const auto& stage : stages) {
        if (!stage.effect) continue;
        if (!text.empty()) text += "-";
        text += stage.effect->name();
    }
    return text;
}

}  // namespace effector