function_sampler.h

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/*
 * Copyright 2026 MusicScience37 (Kenta Kabashima)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once
 
#include <vector>
 
#include "func_sketch/expressions/expression.h"
#include "func_sketch/expressions/expression_evaluator.h"
#include "func_sketch/plotter/plot_config.h"
#include "func_sketch/plotter/plot_range.h"
#include "func_sketch/plotter/point.h"
 
namespace func_sketch::plotter {

class FunctionSampler {
public:
    FunctionSampler(const PlotRange& range, const PlotConfig& config);

    FunctionSampler& range(const PlotRange& value);

    FunctionSampler& config(const PlotConfig& value);

    [[nodiscard]] std::vector<Point> operator()(
        const expressions::Expression& function) const;
 
private:
    [[nodiscard]] std::vector<Point> sample_initial_points(
        const expressions::Expression& function) const;

    [[nodiscard]] std::vector<Point> sample_adaptive_points(
        const expressions::Expression& function,
        const std::vector<Point>& initial_samples) const;

    [[nodiscard]] bool divide_segment_according_to_y_change(
        const expressions::Expression& function, std::vector<Point>& samples,
        std::size_t left_index) const;

    [[nodiscard]] bool divide_segment_according_to_slope_change(
        const expressions::Expression& function, std::vector<Point>& samples,
        std::size_t left_index) const;

    [[nodiscard]] bool divide_segment_when_one_end_is_not_finite(
        const expressions::Expression& function, std::vector<Point>& samples,
        std::size_t left_index) const;

    [[nodiscard]] bool divide_segment(const expressions::Expression& function,
        std::vector<Point>& samples, std::size_t left_index) const;

    [[nodiscard]] Point sample_additional_point(
        const expressions::Expression& function, const Point& left_point,
        const Point& right_point) const;

    [[nodiscard]] bool is_sampling_should_be_skipped(
        const Point& left_point, const Point& right_point) const;

    PlotRange range_;

    PlotConfig config_;

    expressions::ExpressionEvaluator evaluator_;
};
 
}  // namespace func_sketch::plotter