#ifndef FAST_WFC_WFC_HPP_
#define FAST_WFC_WFC_HPP_

#include <optional>
#include <random>

#include "propagator.h"
#include "array_2d.h"
#include "wave.h"

/**
 * Class containing the generic WFC algorithm.
 */
class WFC {
private:
	/**
	 * The random number generator.
	 */
	std::minstd_rand gen;

	/**
	 * The distribution of the patterns as given in input.
	 */
	const std::vector<double> patterns_frequencies;

	/**
	 * The wave, indicating which patterns can be put in which cell.
	 */
	Wave wave;

	/**
	 * The number of distinct patterns.
	 */
	const size_t nb_patterns;

	/**
	 * The propagator, used to propagate the information in the wave.
	 */
	Propagator propagator;

	/**
	 * Transform the wave to a valid output (a 2d array of patterns that aren't in
	 * contradiction). This function should be used only when all cell of the wave
	 * are defined.
	 */
	Array2D<unsigned> wave_to_output() const noexcept;

public:
	/**
	 * Basic constructor initializing the algorithm.
	 */
	WFC(bool periodic_output, int seed, std::vector<double> patterns_frequencies,
			Propagator::PropagatorState propagator, unsigned wave_height,
			unsigned wave_width)
	noexcept;

	/**
	 * Run the algorithm, and return a result if it succeeded.
	 */
	std::optional<Array2D<unsigned>> run() noexcept;

	/**
	 * Return value of observe.
	 */
	enum ObserveStatus {
		success, // WFC has finished and has succeeded.
		failure, // WFC has finished and failed.
		to_continue // WFC isn't finished.
	};

	/**
	 * Define the value of the cell with lowest entropy.
	 */
	ObserveStatus observe() noexcept;

	/**
	 * Propagate the information of the wave.
	 */
	void propagate() noexcept { propagator.propagate(wave); }

	/**
	 * Remove pattern from cell (i,j).
	 */
	void remove_wave_pattern(unsigned i, unsigned j, unsigned pattern) noexcept {
		if (wave.get(i, j, pattern)) {
			wave.set(i, j, pattern, false);
			propagator.add_to_propagator(i, j, pattern);
		}
	}
};

#endif // FAST_WFC_WFC_HPP_