using System;
using System.Collections.Generic;
using Glass.Typesetting;
using UnitTestSharp;
using GlyphDefinition = Glass.SpriteFontDefinition.GlyphDefinition;

namespace Glass.UnitTests.Typesetting
{
    public class TextWidthTests : TestFixture
    {
        public class IsSurrogateTests : TestFixture
        {
            public void ActualSurrogates_AreAllTrue()
            {
                for (int character = 0xD800; character <= 0xDFFF; ++character)
                {
                    CheckTrue(TextWidth.IsSurrogate(character));
                }
            }

            public void FarFromTheSurrogateBits_IsFalse()
            {
                CheckFalse(TextWidth.IsSurrogate(0x0041));
            }

            public void CjkIdeograph_IsNotASurrogate()
            {
                CheckFalse(TextWidth.IsSurrogate(0x4E00));
            }

            public void JustAboveTheSurrogateRange_IsFalse()
            {
                // 0xF800-0xFFFF sets every bit a narrower 4-bit mask (15, 14, 12, 11) would have tested, which is
                // exactly why that narrower mask would false-positive here; this 5-bit mask also pins bit 13,
                // which 0xF800 has set and a real surrogate never does, so it correctly reads as false.
                CheckFalse(TextWidth.IsSurrogate(0xF800));
            }
        }

        public class CalculateTests : TestFixture
        {
            public void NullFont_Throws()
            {
                CheckThrow(typeof(ArgumentNullException));
                TextWidth.Calculate(null, "ab");
            }

            public void EmptyText_IsZero()
            {
                CheckEqual(0, TextWidth.Calculate(WordMeasurerTests.TestFont(), ""));
            }

            public void OneWord_KernsItsInterior()
            {
                CheckEqual(19, TextWidth.Calculate(WordMeasurerTests.TestFont(), "ab"));
            }

            public void KerningFlowsThroughSpaces_UnlikeAWordBoundary()
            {
                CheckEqual(28, TextWidth.Calculate(WordMeasurerTests.TestFont(), "ab c"));
            }

            public void MatchesTheOldEngineOnPlainText()
            {
                SpriteFontDefinition font = WordMeasurerTests.TestFont();
                string text = "ab c ab";

                CheckEqual(Convert.ToInt32(TextLayout.CalculateTextWidth(font, text)),
                    TextWidth.Calculate(font, text));
            }

            public void SoftHyphen_TakesNoWidthAndKerningCarriesAcross()
            {
                CheckEqual(15,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), $"a{LineBreakIterator.SoftHyphen}c"));
            }

            public void AstralCharacter_MeasuresAsOneInvalidGlyph()
            {
                CheckEqual(WordMeasurerTests.InvalidGlyphWidth,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), WordMeasurerTests.Emoji));
            }

            public void AstralDefaultIgnorable_TakesNoWidthAndKerningCarriesAcross()
            {
                CheckEqual(15,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), $"a{WordMeasurerTests.LanguageTag}c"));
            }

            public void LoneSurrogate_MeasuresAsTheInvalidGlyph()
            {
                CheckEqual(WordMeasurerTests.InvalidGlyphWidth,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), WordMeasurer.LoneSurrogate.ToString()));
            }

            public void NonAsciiBmpCharacter_MeasuresItsOwnGlyph()
            {
                var glyphs = new Dictionary<char, GlyphDefinition> { ['é'] = new GlyphDefinition { Width = 12 } };
                SpriteFontDefinition font = WordMeasurerTests.TestFont(glyphs);

                CheckEqual(12, TextWidth.Calculate(font, "é"));
            }

            public void LongAsciiRun_BatchesInPairsWithoutMiscounting()
            {
                CheckEqual(100, TextWidth.Calculate(WordMeasurerTests.TestFont(), new string('a', 10)));
            }

            public void OddLengthAsciiRun_HandlesTheLeftoverCharacter()
            {
                CheckEqual(90, TextWidth.Calculate(WordMeasurerTests.TestFont(), new string('a', 9)));
            }

            public void View_PositionsAreRelativeToItsStart()
            {
                CheckEqual(19, TextWidth.Calculate(WordMeasurerTests.TestFont(), ((StringView)"xxabxx")[2, 4]));
            }

            public void TwoAstralCharacters_EachPairIsWithinItsOwnWindow()
            {
                string text = WordMeasurerTests.Emoji + WordMeasurerTests.Emoji;

                CheckEqual(2 * WordMeasurerTests.InvalidGlyphWidth,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), text));
            }

            public void AstralCharacterAfterAnOddNumberOfCharacters_StraddlesTwoWindowsButStillCombines()
            {
                CheckEqual(10 + WordMeasurerTests.InvalidGlyphWidth + 10,
                    TextWidth.Calculate(WordMeasurerTests.TestFont(), $"a{WordMeasurerTests.Emoji}a"));
            }

            public void TwoNonAsciiBmpCharacters_TakeTheGeneralPairPath()
            {
                var glyphs = new Dictionary<char, GlyphDefinition> { ['é'] = new GlyphDefinition { Width = 12 } };
                SpriteFontDefinition font = WordMeasurerTests.TestFont(glyphs);

                CheckEqual(24, TextWidth.Calculate(font, "éé"));
            }

            // U+3000 ORed with a genuine high surrogate reads as 0xF800 rather than 0xD800: a mask-based check
            // would miss the surrogate here and later throw in ConvertToUtf32 for want of a high half. U+3000 is
            // default-ignorable in this font (width 0), so only the astral pair's own width should show.
            public void BmpCharacterThatHidesAHighSurrogateWhenOred_StillCombinesTheAstralPair()
            {
                string text = $"　{WordMeasurerTests.Emoji}　";

                CheckEqual(WordMeasurerTests.InvalidGlyphWidth, TextWidth.Calculate(WordMeasurerTests.TestFont(),
                    text));
            }
        }
    }
}