/*
 * Copyright 2016 The Cartographer Authors
 *
 * 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.
 */

using System.Text.Json.Serialization;

namespace CartographerSharp.Models.Common;

/// <summary>
/// Protocol buffer representation of Ceres Solver options.
/// Configure the Ceres solver. See the Ceres documentation for more
/// information: https://code.google.com/p/ceres-solver/
/// </summary>
public struct CeresSolverOptions(
    bool useNonmonotonicSteps, 
    int maxNumIterations, 
    int numThreads,
    double? functionTolerance = null,
    double? gradientTolerance = null,
    double? parameterTolerance = null)
{
    /// <summary>
    /// Use non-monotonic steps in the solver.
    /// </summary>
    [JsonPropertyName("use_nonmonotonic_steps")]
    public bool UseNonmonotonicSteps { get; set; } = useNonmonotonicSteps;

    /// <summary>
    /// Maximum number of iterations for the solver.
    /// </summary>
    [JsonPropertyName("max_num_iterations")]
    public int MaxNumIterations { get; set; } = maxNumIterations;

    /// <summary>
    /// Number of threads to use in the solver.
    /// </summary>
    [JsonPropertyName("num_threads")]
    public int NumThreads { get; set; } = numThreads;

    /// <summary>
    /// Function tolerance for convergence check.
    /// Minimizer terminates when (new_cost - old_cost) < function_tolerance * old_cost
    /// </summary>
    [JsonPropertyName("function_tolerance")]
    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
    public double? FunctionTolerance { get; set; } = functionTolerance;

    /// <summary>
    /// Gradient tolerance for convergence check.
    /// Minimizer terminates when max_i |x - Project(Plus(x, -g(x))| < gradient_tolerance
    /// </summary>
    [JsonPropertyName("gradient_tolerance")]
    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
    public double? GradientTolerance { get; set; } = gradientTolerance;

    /// <summary>
    /// Parameter tolerance for convergence check.
    /// Minimizer terminates when |step|_2 <= parameter_tolerance * (|x|_2 + parameter_tolerance)
    /// </summary>
    [JsonPropertyName("parameter_tolerance")]
    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
    public double? ParameterTolerance { get; set; } = parameterTolerance;
}