using System;
using UnitTestSharp;

namespace Amphora.UnitTests
{
    public class ChunkedTextTests : TestFixture
    {
        public class ShortChunks : IChunkedText
        {
            private readonly string text;
            private readonly int size;

            public ShortChunks(string text, int size)
            {
                this.text = text;
                this.size = size;
            }

            public int Length => text.Length;

            public StringView GetChunk(int start)
            {
                return new StringView(text, start, Math.Min(start + size, text.Length));
            }
        }

        public class StringChunksTests : TestFixture
        {
            public void CtorThrowsOnNull()
            {
                CheckThrow(typeof(ArgumentNullException));
                new StringChunks(null);
            }

            public void LengthIsTheStringsLength()
            {
                CheckEqual(5, new StringChunks("hello").Length);
            }

            public void LengthOfAnEmptyStringIsZero()
            {
                CheckEqual(0, new StringChunks("").Length);
            }

            public void TheChunkAtZeroIsTheWholeString()
            {
                CheckEqual("hello", new StringChunks("hello").GetChunk(0).ToString());
            }

            public void TheChunkAtAnIndexRunsToTheEnd()
            {
                CheckEqual("llo", new StringChunks("hello").GetChunk(2).ToString());
            }

            public void TheChunkAtTheLastIndexIsTheLastCharacter()
            {
                CheckEqual("o", new StringChunks("hello").GetChunk(4).ToString());
            }

            public void AStartAtTheLengthThrows()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new StringChunks("hello").GetChunk(5);
            }

            public void ANegativeStartThrows()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new StringChunks("hello").GetChunk(-1);
            }

            public void AnyStartOnAnEmptyStringThrows()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new StringChunks("").GetChunk(0);
            }
        }

        public class ToTextTests : TestFixture
        {
            public void OneChunk_ReturnsTheText()
            {
                CheckEqual("hello", new StringChunks("hello").ToText());
            }

            public void ManyChunks_ReturnsTheTextInOrderWithNoGapOrOverlap()
            {
                CheckEqual("hello, world", new ShortChunks("hello, world", size: 5).ToText());
            }

            public void AChunkSizeThatDividesTheLength_ReturnsTheText()
            {
                CheckEqual("abcdef", new ShortChunks("abcdef", size: 3).ToText());
            }

            public void AChunkOfOneCharacter_ReturnsTheText()
            {
                CheckEqual("abc", new ShortChunks("abc", size: 1).ToText());
            }

            public void AnEmptyText_ReturnsAnEmptyString()
            {
                CheckEqual("", new ShortChunks("", size: 4).ToText());
            }
        }
    }
}