using System;
using Amphora;
using Glass.Typesetting;
using UnitTestSharp;

namespace Glass.UnitTests.Typesetting
{
    public class CaretLocatorTests : TestFixture
    {
        public const int Roomy = GlyphPlacerTests.Roomy;

        /// <summary>
        /// Letters 10 wide, a space 4, and lines 10 apart.
        /// </summary>
        public static readonly SpriteFontDefinition Font = GlyphPlacerTests.Font;

        public static CaretPosition Locate(StringView text, int index, int containerWidth = Roomy,
            IFontMetrics font = null, Alignment.Horizontal alignment = Alignment.Horizontal.Left,
            TextOverflow overflow = TextOverflow.Clip, int? maxLines = null,
            TrailingSpaceMode trailingSpaces = TrailingSpaceMode.Hang, bool atLineEnd = false)
        {
            return CaretLocator.Locate(font ?? Font, text, index, containerWidth, alignment, maxHeight: null, overflow,
                maxLines, trailingSpaces, atLineEnd);
        }

        public static int IndexAt(StringView text, int x, int y, int containerWidth = Roomy,
            IFontMetrics font = null, Alignment.Horizontal alignment = Alignment.Horizontal.Left,
            TextOverflow overflow = TextOverflow.Clip, int? maxLines = null)
        {
            return IndexAtWithSide(text, x, y, containerWidth, font, alignment, overflow, maxLines).index;
        }

        public static (int index, bool atLineEnd) IndexAtWithSide(StringView text, int x, int y,
            int containerWidth = Roomy, IFontMetrics font = null,
            Alignment.Horizontal alignment = Alignment.Horizontal.Left, TextOverflow overflow = TextOverflow.Clip,
            int? maxLines = null)
        {
            int index = CaretLocator.IndexAt(font ?? Font, text, x, y, containerWidth, alignment, out bool atLineEnd,
                maxHeight: null, overflow, maxLines);

            return (index, atLineEnd);
        }

        public class LocateTests : TestFixture
        {
            public void EmptyText_IsAtTheStartOfTheFirstLine()
            {
                CheckEqual(new CaretPosition(0, 0, 0), Locate("", 0));
            }

            public void EmptyText_FollowsTheAlignment()
            {
                CheckEqual(new CaretPosition(0, 100, 0), Locate("", 0, 100, alignment: Alignment.Horizontal.Right));
                CheckEqual(new CaretPosition(0, 50, 0), Locate("", 0, 100, alignment: Alignment.Horizontal.Center));
            }

            public void EachIndex_IsWhereTheNextGlyphStarts()
            {
                CheckEqual(new CaretPosition(0, 0, 0), Locate("abc", 0));
                CheckEqual(new CaretPosition(0, 10, 0), Locate("abc", 1));
                CheckEqual(new CaretPosition(0, 20, 0), Locate("abc", 2));
            }

            public void TheEndOfTheText_IsAfterTheLastGlyph()
            {
                CheckEqual(new CaretPosition(0, 30, 0), Locate("abc", 3));
            }

            public void Kerning_MovesTheStopWithTheGlyph()
            {
                CheckEqual(new CaretPosition(0, 9, 0), Locate("ab", 1, font: WordMeasurerTests.SharedFont));
            }

            public void AWrappedLine_StartsWhereItsFirstGlyphIs()
            {
                CheckEqual(new CaretPosition(1, 0, 10), Locate("ab cd", 3, 25));
                CheckEqual(new CaretPosition(1, 10, 10), Locate("ab cd", 4, 25));
            }

            public void TheEndOfAWrappedLine_IsOnTheNextLine()
            {
                CheckEqual(new CaretPosition(0, 20, 0), Locate("ab cd", 2, 25));
                CheckEqual(new CaretPosition(1, 0, 10), Locate("ab cd", 3, 25));
            }

            public void AtLineEnd_DrawsTheStartOfAWrappedLineAtTheEndOfTheOneBefore()
            {
                CheckEqual(new CaretPosition(0, 24, 0), Locate("ab cd", 3, 25, atLineEnd: true));
            }

            public void AtLineEnd_FollowsTheAlignment()
            {
                CheckEqual(new CaretPosition(0, 29, 0),
                    Locate("ab cd", 3, 25, alignment: Alignment.Horizontal.Right, atLineEnd: true));
            }

            public void AtLineEnd_AfterASoftHyphen_IsAfterTheHyphen()
            {
                string text = "b" + LineBreakIterator.SoftHyphen + "c";

                CheckEqual(new CaretPosition(0, 17, 0), Locate(text, 2, 18, atLineEnd: true));
            }

            public void AtLineEnd_DoesNothingToOtherIndices()
            {
                CheckEqual(new CaretPosition(0, 0, 0), Locate("ab cd", 0, 25, atLineEnd: true));
                CheckEqual(new CaretPosition(0, 20, 0), Locate("ab cd", 2, 25, atLineEnd: true));
                CheckEqual(new CaretPosition(1, 20, 10), Locate("ab cd", 5, 25, atLineEnd: true));
            }

            public void AtLineEnd_DoesNothingAfterAHardBreak()
            {
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\nb", 2, atLineEnd: true));
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\r\nb", 3, atLineEnd: true));
            }

            public void AtLineEnd_DoesNothingOnAnEmptyLineAfterAHardBreak()
            {
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\n", 2, atLineEnd: true));
            }

            public void TheEndOfTheLastLine_IsAfterItsLastGlyph()
            {
                CheckEqual(new CaretPosition(1, 20, 10), Locate("ab cd", 5, 25));
            }

            public void HangingSpaces_AreStopsPastTheLinesVisibleEdge()
            {
                CheckEqual(new CaretPosition(0, 100, 0), Locate("a ", 1, 100, alignment: Alignment.Horizontal.Right));
                CheckEqual(new CaretPosition(0, 104, 0), Locate("a ", 2, 100, alignment: Alignment.Horizontal.Right));
            }

            public void BeforeAHardBreak_IsTheEndOfItsLine()
            {
                CheckEqual(new CaretPosition(0, 10, 0), Locate("a\nb", 1));
            }

            public void AfterAHardBreak_IsTheStartOfTheNextLine()
            {
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\nb", 2));
            }

            public void CarriageReturnLineFeed_IsOneBreak()
            {
                CheckEqual(new CaretPosition(0, 10, 0), Locate("a\r\nb", 1));
                CheckEqual(new CaretPosition(0, 10, 0), Locate("a\r\nb", 2));
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\r\nb", 3));
            }

            public void AnEmptyLine_IsAtItsOwnStart()
            {
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\n\nb", 2));
                CheckEqual(new CaretPosition(2, 0, 20), Locate("a\n\nb", 3));
            }

            public void AnEmptyLine_FollowsTheAlignment()
            {
                CheckEqual(new CaretPosition(1, 100, 10),
                    Locate("a\n\nb", 2, 100, alignment: Alignment.Horizontal.Right));
            }

            public void TextEndingInAHardBreak_HasAnEmptyLineAfterIt()
            {
                CheckEqual(new CaretPosition(0, 10, 0), Locate("a\n", 1));
                CheckEqual(new CaretPosition(1, 0, 10), Locate("a\n", 2));
            }

            public void TextEndingInOnlyAHardBreak_HasAnEmptyLineAfterIt()
            {
                CheckEqual(new CaretPosition(0, 0, 0), Locate("\n", 0));
                CheckEqual(new CaretPosition(1, 0, 10), Locate("\n", 1));
            }

            public void CutShortText_HasNoEmptyLineAfterTheKeptLine()
            {
                CheckEqual(new CaretPosition(0, 20, 0), Locate("ab\ncd", 3, maxLines: 1));
                CheckEqual(new CaretPosition(0, 20, 0), Locate("ab\ncd", 5, maxLines: 1));
            }

            public void RightAligned_EachLineAlignsByItsOwnWidth()
            {
                const string text = "a\nbbb";

                CheckEqual(new CaretPosition(0, 100, 0), Locate(text, 1, 100, alignment: Alignment.Horizontal.Right));
                CheckEqual(new CaretPosition(1, 70, 10), Locate(text, 2, 100, alignment: Alignment.Horizontal.Right));
                CheckEqual(new CaretPosition(1, 100, 10), Locate(text, 5, 100, alignment: Alignment.Horizontal.Right));
            }

            public void Centered_RoundsDownToAWholePixel()
            {
                CheckEqual(new CaretPosition(0, 45, 0), Locate("a", 0, 101, alignment: Alignment.Horizontal.Center));
                CheckEqual(new CaretPosition(0, 55, 0), Locate("a", 1, 101, alignment: Alignment.Horizontal.Center));
            }

            public void SoftHyphenTaken_PutsTheCaretBeforeTheHyphen()
            {
                string text = "b" + LineBreakIterator.SoftHyphen + "c";

                CheckEqual(new CaretPosition(0, 10, 0), Locate(text, 1, 18));
                CheckEqual(new CaretPosition(1, 0, 10), Locate(text, 2, 18));
            }

            public void Ellipsis_PutsTheCaretBeforeTheMarker()
            {
                CheckEqual(new CaretPosition(0, 10, 0),
                    Locate("aaa bbb", 1, 34, overflow: TextOverflow.Ellipsis, maxLines: 1));
                CheckEqual(new CaretPosition(0, 20, 0),
                    Locate("aaa bbb", 2, 34, overflow: TextOverflow.Ellipsis, maxLines: 1));
            }

            public void CutOffText_WaitsWhereTheKeptTextEnds()
            {
                CheckEqual(new CaretPosition(0, 20, 0),
                    Locate("aaa bbb", 5, 34, overflow: TextOverflow.Ellipsis, maxLines: 1));
                CheckEqual(new CaretPosition(0, 20, 0),
                    Locate("aaa bbb", 7, 34, overflow: TextOverflow.Ellipsis, maxLines: 1));
            }

            public void ASurrogatePair_IsOneGlyph()
            {
                string text = "a" + WordMeasurerTests.Emoji + "b";

                CheckEqual(new CaretPosition(0, 10, 0), Locate(text, 1));
                CheckEqual(new CaretPosition(0, 17, 0), Locate(text, 3));
            }

            public void InsideASurrogatePair_IsAfterIt()
            {
                CheckEqual(new CaretPosition(0, 17, 0), Locate("a" + WordMeasurerTests.Emoji + "b", 2));
            }

            public void AnInvisibleCharacter_TakesNoRoom()
            {
                string text = "a" + WordMeasurerTests.LanguageTag + "b";

                CheckEqual(new CaretPosition(0, 10, 0), Locate(text, 1));
                CheckEqual(new CaretPosition(0, 10, 0), Locate(text, 3));
            }

            public void AViewIntoALongerString_IsLikeTheStandaloneString()
            {
                var view = new StringView("xab cdy", 1, 6);
                for (int index = 0; index <= view.Length; ++index)
                {
                    CheckEqual(Locate("ab cd", index, 25), Locate(view, index, 25));
                }
            }

            public void AViewThatStartsOnALineFeed_CountsOnlyTheLineFeed()
            {
                var view = new StringView("a\r\nb", 2, 4);

                CheckEqual(new CaretPosition(0, 0, 0), Locate(view, 0));
                CheckEqual(new CaretPosition(1, 0, 10), Locate(view, 1));
            }

            public void NegativeIndex_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                Locate("abc", -1);
            }

            public void IndexPastTheEnd_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                Locate("abc", 4);
            }
        }

        public class IndexAtTests : TestFixture
        {
            public void EmptyText_IsZero()
            {
                CheckEqual(0, IndexAt("", 50, 50));
            }

            public void APointOnAGlyph_TakesTheNearerStop()
            {
                CheckEqual(0, IndexAt("abc", 4, 0));
                CheckEqual(1, IndexAt("abc", 6, 0));
                CheckEqual(1, IndexAt("abc", 14, 0));
                CheckEqual(2, IndexAt("abc", 16, 0));
            }

            public void AMidwayPoint_TakesTheEarlierStop()
            {
                CheckEqual(0, IndexAt("abc", 5, 0));
            }

            public void LeftOfTheText_IsTheFirstStop()
            {
                CheckEqual(0, IndexAt("abc", -50, 0));
            }

            public void RightOfTheText_IsTheEnd()
            {
                CheckEqual(3, IndexAt("abc", 26, 0));
                CheckEqual(3, IndexAt("abc", 1000, 0));
            }

            public void AbovAndBelowTheText_GoToTheFirstAndLastLines()
            {
                CheckEqual(1, IndexAt("abc\ndef", 10, -50));
                CheckEqual(5, IndexAt("abc\ndef", 10, 500));
            }

            public void ALaterLine_IsFoundByItsRow()
            {
                CheckEqual(3, IndexAt("ab cd", 0, 12, 25));
                CheckEqual(5, IndexAt("ab cd", 1000, 12, 25));
            }

            public void EachLine_OwnsTheRowsFromItsTopToTheNextLinesTop()
            {
                CheckEqual(0, IndexAt("a\nb\nc", 0, 9));
                CheckEqual(2, IndexAt("a\nb\nc", 0, 10));
                CheckEqual(4, IndexAt("a\nb\nc", 0, 20));
            }

            public void PastTheEndOfAWrappedLine_IsItsEnd()
            {
                CheckEqual((3, true), IndexAtWithSide("ab cd", 1000, 0, 25));
                CheckEqual((2, true), IndexAtWithSide("abcd", 1000, 0, 25));
            }

            public void TheStartOfAWrappedLine_IsNotItsEnd()
            {
                CheckEqual((3, false), IndexAtWithSide("ab cd", 0, 12, 25));
            }

            public void TheEndOfALineThatDoesNotWrapOn_IsNotALineEnd()
            {
                CheckEqual((5, false), IndexAtWithSide("ab cd", 1000, 12, 25));
                CheckEqual((1, false), IndexAtWithSide("a\nb", 100, 5));
                CheckEqual((3, false), IndexAtWithSide("abc", 1000, 0));
            }

            public void TheEndOfAWrappedLine_IsAtItsHangingSpaces()
            {
                CheckEqual((2, false), IndexAtWithSide("ab cd", 21, 0, 25));
                CheckEqual((3, true), IndexAtWithSide("ab cd", 23, 0, 25));
            }

            public void PastTheEndOfAHardBrokenLine_IsBeforeTheBreak()
            {
                CheckEqual(1, IndexAt("a\nb", 100, 5));
                CheckEqual(1, IndexAt("a\r\nb", 100, 5));
            }

            public void AfterAHardBreak_IsTheStartOfTheNextLine()
            {
                CheckEqual(2, IndexAt("a\nb", 0, 15));
                CheckEqual(3, IndexAt("a\r\nb", 0, 15));
            }

            public void AnEmptyLine_IsItsOwnStart()
            {
                CheckEqual(2, IndexAt("a\n\nb", 100, 15));
            }

            public void BelowTextEndingInAHardBreak_IsTheEmptyLineAfterIt()
            {
                CheckEqual(2, IndexAt("a\n", 0, 15));
                CheckEqual(2, IndexAt("a\n", 0, 500));
            }

            public void RightAligned_UsesWhereTheLineSits()
            {
                const string text = "a\nbbb";
                var right = Alignment.Horizontal.Right;

                CheckEqual(2, IndexAt(text, 0, 15, 100, alignment: right));
                CheckEqual(3, IndexAt(text, 78, 15, 100, alignment: right));
                CheckEqual(5, IndexAt(text, 1000, 15, 100, alignment: right));
            }

            public void SoftHyphen_HasAStopBeforeTheHyphen()
            {
                string text = "b" + LineBreakIterator.SoftHyphen + "c";

                CheckEqual(1, IndexAt(text, 7, 0, 18));
                CheckEqual((2, true), IndexAtWithSide(text, 100, 0, 18));
                CheckEqual(2, IndexAt(text, 0, 12, 18));
            }

            public void Ellipsis_EndsAtTheKeptText()
            {
                CheckEqual(2, IndexAt("aaa bbb", 1000, 0, 34, overflow: TextOverflow.Ellipsis, maxLines: 1));
            }

            public void AMarkerOfSeveralGlyphs_IsOneStop()
            {
                SpriteFontDefinition font = LineWrapperTests.FontWithLineHeight(ascent: 8, descent: 2,
                    withEllipsis: false);

                CheckEqual(2, IndexAt("ab\ncd", 1000, 0, Roomy, font, overflow: TextOverflow.Ellipsis, maxLines: 1));
                CheckEqual(2, IndexAt("ab\ncd", 22, 0, Roomy, font, overflow: TextOverflow.Ellipsis, maxLines: 1));
            }

            public void AViewThatStartsOnALineFeed_IsRelativeToTheView()
            {
                var view = new StringView("a\r\nb", 2, 4);

                CheckEqual(0, IndexAt(view, 100, 5));
                CheckEqual(1, IndexAt(view, 0, 15));
            }

            public void AViewIntoALongerString_IsLikeTheStandaloneString()
            {
                var view = new StringView("xab cdy", 1, 6);

                CheckEqual(IndexAt("ab cd", 1000, 12, 25), IndexAt(view, 1000, 12, 25));
            }

            public void LocatingAnyIndex_AndFindingThatPoint_ReturnsTheIndex()
            {
                const string text = "ab cd\nef gh\n\nij";

                foreach (var alignment in new[] { Alignment.Horizontal.Left, Alignment.Horizontal.Center,
                    Alignment.Horizontal.Right })
                {
                    for (int index = 0; index <= text.Length; ++index)
                    {
                        CaretPosition start = Locate(text, index, 25, alignment: alignment);
                        CaretPosition end = Locate(text, index, 25, alignment: alignment, atLineEnd: true);

                        CheckEqual((index, false), IndexAtWithSide(text, start.X, start.Y, 25, alignment: alignment));
                        CheckEqual((index, end != start),
                            IndexAtWithSide(text, end.X, end.Y, 25, alignment: alignment));
                    }
                }
            }
        }
    }
}