using Xunit;
using MathEngine.Tokenizer;

using static MathEngine.Tokenizer.Token;
using Xunit.Sdk;
using System;

namespace EngineTests.Tokenizer
{
    /// <summary>
    /// Class for testing the Tokenizer
    /// </summary>
    public class TokenizerTests
    {
        /// <summary>
        /// Test the Tokenizer on an empty string
        /// </summary>
        [Fact]
        public void TestTokenizeEmptystringReturnsEmptyList()
        {
            string testString = "";
            Token one = new("1", TokenType.Numeric);
            List<Token> expectedValue = new()
            {
                one,
                Token.Plus,
                one
            };
            List<Token> returnedValue = ExpressionTokenizer.Tokenize(testString);

            Assert.Empty(returnedValue);
        }


        public static IEnumerable<object[]> TestTokenizeStringsCases
        {
            get
            {
                Token one = new("1", TokenType.Numeric);
                Token decimal_token = new("123.456", TokenType.Numeric);
                Token point_five = new(".5", TokenType.Numeric);
                List<Token> basic_expression = new List<Token> { one, Token.Plus, one };

                return new List<object[]> {
                new object[] { "1+1", basic_expression},
                new object[] { "  1   +   1              ", basic_expression },
                new object[] { "+",  new List<Token> { Token.Plus} },
                new object[] { "-",  new List<Token> { Token.Minus} },
                new object[] { "*",  new List<Token> { Token.Multiply} },
                new object[] { "/",  new List<Token> { Token.Divide} },
                new object[] { "^",  new List<Token> { Token.Exponentiation} },
                new object[] { "(",  new List<Token> { Token.LeftParenthesis} },
                new object[] { ")",  new List<Token> { Token.RightParenthesis} },
                new object[] { "123.456",  new List<Token> { decimal_token } },
                new object[] { ".5",  new List<Token> { point_five } },
            };
            }
        }        
        
        /// <summary>
        /// Test the Tokenizer on strings
        /// </summary>
        [Theory]
        [MemberData(nameof(TestTokenizeStringsCases))]
        public void TestTokenizeStrings(string testString, object expectedResult)
        {
           List<Token> returnedValue = ExpressionTokenizer.Tokenize(testString.AsSpan());

           Assert.Equal(expectedResult, returnedValue);
        }

        /// <summary>
        /// Test the Tokenizer on a basic string, but with significant ammounts of whitespace
        /// </summary>
        [Fact]
        public void TestTokenizeNumberWithMultipleDecimalPointsIsInvalid()
        {
            string test_expression = "123.456.789";

            var ex = Assert.Throws<TokenizerException>(() => ExpressionTokenizer.Tokenize(test_expression.AsSpan()));

            Assert.Equal("Syntax error: The number 123.456.789 has multiple decimal point when at most one is allowed.", ex.Message);

        }


        /// <summary>
        /// Test the Tokenizer with all operators
        /// </summary>
        [Fact]
        public void TestTokenizeStringWithAllOperators()
        {
            //Arrange
            string testString = "1+2-3*4/5";
            Token one = new("1", TokenType.Numeric);
            Token two = new("2", TokenType.Numeric);
            Token three = new("3", TokenType.Numeric);
            Token four = new("4", TokenType.Numeric);
            Token five = new("5", TokenType.Numeric);
            List<Token> expectedValue = new()
            {
                one,
                Token.Plus,
                two,
                Token.Minus,
                three,
                Token.Multiply,
                four,
                Token.Divide,
                five
            };
            List<Token> returnedValue = ExpressionTokenizer.Tokenize(testString);
        }
    }
}