using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using DotnetStandardStreams;
using DotnetStandardStreamsTests.Testables;

namespace DotnetStandardStreamsTests;

public class StdInTextSourceTests
{
	private static TextReader CreateStdIn() => new ListTextReader(["1", "2", "", "3"]);

	private static TextReader CreateEmptyStdIn() => new ListTextReader([]);

	private static void WrapStdInTest(Action<ITextSource> testCode, TextReader? explicitStdIn = null)
	{
		explicitStdIn ??= CreateStdIn();

		TextReader oldInputReader = System.Console.In;
		try
		{
			System.Console.SetIn(explicitStdIn);

			ITextSource stdin = new StdInTextSource();
			stdin.Open();
			try
			{
				testCode.Invoke(stdin);
			}
			finally
			{
				stdin.Close();
			}
		}
		finally
		{
			System.Console.SetIn(oldInputReader);
		}
	}

	[Fact]
	public void CanReadAllFromStandardIn()
	{
		WrapStdInTest(static stdin =>
		{
			List<string> actual = stdin.ReadAll().ToList();
			actual.Count.ShouldBe(4);
			actual[0].ShouldBe("1");
			actual[1].ShouldBe("2");
			actual[2].ShouldBe(string.Empty);
			actual[3].ShouldBe("3");
		});
	}

	[Fact]
	public void CanReadIndividualLinesFromStandardIn()
	{
		WrapStdInTest(static stdin =>
		{
			string s;
			s = stdin.Read();
			stdin.Eof().ShouldBe(false);
			s.ShouldBe("1");

			s = stdin.Read();
			stdin.Eof().ShouldBe(false);
			s.ShouldBe("2");

			s = stdin.Read();
			stdin.Eof().ShouldBe(false);
			s.ShouldBe(string.Empty);

			s = stdin.Read();
			stdin.Eof().ShouldBe(false);
			s.ShouldBe("3");

			_ = stdin.Read();
			stdin.Eof().ShouldBe(true);
		});
	}

	[Fact]
	public void CanWhileLoopThroughStdInNormally()
	{
		WrapStdInTest(static stdin =>
		{
			int lineCount = 0;
			_ = stdin.Read();

			while (!stdin.Eof())
			{
				lineCount++;
				_ = stdin.Read();
			}

			lineCount.ShouldBe(4);
		});
	}

	[Fact]
	public void CanReadAllThroughStdInNormally()
	{
		WrapStdInTest(static stdin =>
		{
			List<string> lines = stdin.ReadAll().ToList();
			int lineCount = lines.Count;
			lineCount.ShouldBe(4);
			lines.ShouldBe(["1", "2", "", "3"]);
		});
	}

	[Fact]
	public void CanWhileLoopThroughStdInEmpty()
	{
		WrapStdInTest(
			static stdin =>
			{
				int lineCount = 0;
				_ = stdin.Read();

				while (!stdin.Eof())
				{
					lineCount++;
					_ = stdin.Read();
				}

				lineCount.ShouldBe(0);
			},
			CreateEmptyStdIn());
	}

	[Fact]
	public void CanReadAllThroughStdInEmpty()
	{
		WrapStdInTest(static stdin =>
			{
				List<string> lines = stdin.ReadAll().ToList();
				int lineCount = lines.Count;
				lineCount.ShouldBe(0);
			},
			CreateEmptyStdIn());
	}
}