using System.Text.Json;

namespace Workflow.Domain.Expressions.Comparators;

/// <summary>
/// 数值对比器。处理 ==, !=, >, <, >=, <= 操作符。
/// 仅当两个值都能解析为 decimal 时才进行比较，否则返回 false。
/// </summary>
public class NumericComparator : IValueComparator
{
    private static readonly IReadOnlySet<string> _supportedOperators = new HashSet<string>
    {
        "==", "!=", ">", "<", ">=", "<="
    };

    public IReadOnlySet<string> SupportedOperators => _supportedOperators;

    public bool Compare(object? fieldValue, string operatorName, object? conditionValue)
    {
        if (fieldValue is null || !_supportedOperators.Contains(operatorName))
            return false;

        if (!ValueComparatorHelper.TryGetDecimal(fieldValue, out var fieldNum))
            return false;

        if (!ValueComparatorHelper.TryGetDecimalFromCondition(conditionValue, out var condNum))
            return false;

        return operatorName switch
        {
            "==" => fieldNum == condNum,
            "!=" => fieldNum != condNum,
            ">" => fieldNum > condNum,
            "<" => fieldNum < condNum,
            ">=" => fieldNum >= condNum,
            "<=" => fieldNum <= condNum,
            _ => false
        };
    }
}