using DynamicExpresso;
using System.Linq;

namespace IStation.DynamicExpresso
{
    /// <summary>
    /// 验证器
    /// </summary>
    public class Validator
    {
        /// <summary>
        /// 验证（最多包含一个变量）
        /// </summary>
        /// <param name="expression">计算表达式</param>
        /// <param name="arg">变量</param>
        /// <returns></returns>
        public static bool Verify(string expression, string arg)
        {
            if (string.IsNullOrEmpty(expression))
                return false;

            var interpreter = new Interpreter();
            if (!string.IsNullOrEmpty(arg))
                interpreter.SetVariable(arg, 1);
            try
            {
                _ = interpreter.Eval<double>(expression);
                return true;
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 验证 (规定变量数量)
        /// </summary>
        /// <param name="expression">计算表达式</param>
        /// <param name="count">变量数量</param>
        /// <returns></returns>
        public static bool Verify(string expression, int count = 1)
        {
            if (string.IsNullOrEmpty(expression))
                return false;
            var interpreter = new Interpreter();
            var args = interpreter.DetectIdentifiers(expression).UnknownIdentifiers.ToList();
            if (args.Count != count)
                return false;
            args.ForEach(x => interpreter.SetVariable(x, 1));
            try
            {
                _ = interpreter.Eval<double>(expression);
                return true;
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 验证 (规定最多变量数量)
        /// </summary>
        /// <param name="expression">计算表达式</param>
        /// <param name="maxCount">最多变量数量</param>
        /// <returns></returns>
        public static bool VerifyMax(string expression, int maxCount = 1)
        {
            if (string.IsNullOrEmpty(expression))
                return false;
            var interpreter = new Interpreter();
            var args = interpreter.DetectIdentifiers(expression).UnknownIdentifiers.ToList();
            if (args.Count > maxCount)
                return false;
            args.ForEach(x => interpreter.SetVariable(x, 1));
            try
            {
                _ = interpreter.Eval<double>(expression);
                return true;
            }
            catch
            {
                return false;
            }
        }

    }
}