using Glass.Typesetting;
using UnitTestSharp;

namespace Glass.UnitTests.Typesetting
{
    public class FacedPenTests : TestFixture
    {
        private static FaceRuns Runs(params (int start, int end, IFontMetrics font)[] runs)
        {
            return FacedMeasuringTests.Runs(FacedMeasuringTests.Kerned, runs);
        }

        public class StepTests : TestFixture
        {
            public void FirstGlyph_HasNothingToKernAgainst()
            {
                var pen = new FacedPen(Runs());
                int position = 0;

                CheckTrue(pen.Step("ab", ref position, 2, out int kerning, out int width));

                CheckEqual(0, kerning);
                CheckEqual(10, width);
                CheckEqual(1, position);
            }

            public void GlyphAfterOneInTheSameFont_KernsAgainstIt()
            {
                var pen = new FacedPen(Runs());
                int position = 0;
                pen.Step("ab", ref position, 2, out _, out _);

                pen.Step("ab", ref position, 2, out int kerning, out int width);

                CheckEqual(-1, kerning);
                CheckEqual(10, width);
            }

            public void GlyphInAnotherFont_KernsAsAtTheStartOfALine()
            {
                var pen = new FacedPen(Runs((1, 2, FacedMeasuringTests.KernedWide)));
                int position = 0;
                pen.Step("ab", ref position, 2, out _, out _);

                pen.Step("ab", ref position, 2, out int kerning, out int width);

                CheckEqual(0, kerning);
                CheckEqual(14, width);
            }

            public void GlyphAfterOneInTheSameOtherFont_KernsWithThatFontsTable()
            {
                var pen = new FacedPen(Runs((0, 2, FacedMeasuringTests.KernedWide)));
                int position = 0;
                pen.Step("ab", ref position, 2, out _, out _);

                pen.Step("ab", ref position, 2, out int kerning, out int width);

                CheckEqual(-3, kerning);
                CheckEqual(14, width);
            }

            public void GlyphBackInTheBaseFont_KernsAsAtTheStartOfALine()
            {
                var pen = new FacedPen(Runs((0, 1, FacedMeasuringTests.KernedWide)));
                int position = 0;
                pen.Step("ab", ref position, 2, out _, out _);

                pen.Step("ab", ref position, 2, out int kerning, out _);

                CheckEqual(0, kerning);
            }

            public void CodePointThatDrawsNothing_ReturnsFalseAndStepsOverIt()
            {
                var pen = new FacedPen(Runs());
                string text = "­a";
                int position = 0;

                CheckFalse(pen.Step(text, ref position, 2, out int kerning, out int width));

                CheckEqual(1, position);
                CheckEqual(0, kerning);
                CheckEqual(0, width);
            }

            public void CodePointThatDrawsNothing_LeavesTheKerningAlone()
            {
                var pen = new FacedPen(Runs((1, 2, FacedMeasuringTests.KernedWide)));
                string text = "a­b";
                int position = 0;
                pen.Step(text, ref position, 3, out _, out _);
                pen.Step(text, ref position, 3, out _, out _);

                pen.Step(text, ref position, 3, out int kerning, out _);

                CheckEqual(-1, kerning);
            }

            public void SurrogatePair_IsOneGlyphOfTheInvalidGlyphsWidth()
            {
                var pen = new FacedPen(Runs());
                string text = WordMeasurerTests.Emoji;
                int position = 0;

                CheckTrue(pen.Step(text, ref position, 2, out _, out int width));

                CheckEqual(2, position);
                CheckEqual(WordMeasurerTests.InvalidGlyphWidth, width);
            }

            public void GlyphIsMeasuredInTheFontAtItsFirstCodeUnit()
            {
                var pen = new FacedPen(Runs((1, 2, FacedMeasuringTests.KernedWide)));
                string text = "a" + WordMeasurerTests.Emoji;
                int position = 1;

                pen.Step(text, ref position, 3, out _, out int width);

                CheckEqual(3, position);
                CheckEqual(9, width);
            }

            public void End_StopsASurrogatePairThatWouldStraddleIt()
            {
                var pen = new FacedPen(Runs());
                string text = WordMeasurerTests.Emoji;
                int position = 0;

                CheckTrue(pen.Step(text, ref position, 1, out _, out int width));

                CheckEqual(1, position);
                CheckEqual(WordMeasurerTests.InvalidGlyphWidth, width);
            }
        }

        public class StepOverTests : TestFixture
        {
            public void ReturnsTheKerningAgainstTheGlyphBefore()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                var pen = new FacedPen(Runs());
                pen.StepOver(narrow, narrow.MetricsTable['a']);

                CheckEqual(-1, pen.StepOver(narrow, narrow.MetricsTable['b']));
            }

            public void InAnotherFont_ReturnsNoKerning()
            {
                var pen = new FacedPen(Runs());
                pen.StepOver(FacedMeasuringTests.Kerned, FacedMeasuringTests.Kerned.MetricsTable['a']);

                CheckEqual(0, pen.StepOver(FacedMeasuringTests.KernedWide,
                    FacedMeasuringTests.KernedWide.MetricsTable['b']));
            }

            public void RemembersTheGlyphForTheNextOne()
            {
                IFontMetrics wide = FacedMeasuringTests.KernedWide;
                var pen = new FacedPen(Runs());
                pen.StepOver(wide, wide.MetricsTable['a']);

                CheckEqual(-3, pen.StepOver(wide, wide.MetricsTable['b']));
            }
        }

        public class KerningIntoTests : TestFixture
        {
            public void ReturnsTheKerningWithoutSteppingOver()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                var pen = new FacedPen(Runs());
                pen.StepOver(narrow, narrow.MetricsTable['a']);

                CheckEqual(-1, pen.KerningInto(narrow, narrow.MetricsTable['b']));
                CheckEqual(-1, pen.KerningInto(narrow, narrow.MetricsTable['b']));
            }

            public void InAnotherFont_IsNone()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                IFontMetrics wide = FacedMeasuringTests.KernedWide;
                var pen = new FacedPen(Runs());
                pen.StepOver(narrow, narrow.MetricsTable['a']);

                CheckEqual(0, pen.KerningInto(wide, wide.MetricsTable['b']));
            }
        }

        public class RestartTests : TestFixture
        {
            public void ForgetsTheGlyphBefore()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                var pen = new FacedPen(Runs());
                pen.StepOver(narrow, narrow.MetricsTable['a']);

                pen.Restart();

                CheckEqual(0, pen.StepOver(narrow, narrow.MetricsTable['b']));
            }
        }

        public class RowTests : TestFixture
        {
            public void StartsAtTheStartOfALine()
            {
                CheckEqual(0, new FacedPen(Runs()).Row);
            }

            public void IsTheLastGlyphsKerningRow()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                var pen = new FacedPen(Runs());

                pen.StepOver(narrow, narrow.MetricsTable['b']);

                CheckEqual(narrow.MetricsTable['b'].LeftKerningRow, pen.Row);
            }

            public void AfterRestarting_IsTheStartOfALine()
            {
                IFontMetrics narrow = FacedMeasuringTests.Kerned;
                var pen = new FacedPen(Runs());
                pen.StepOver(narrow, narrow.MetricsTable['b']);

                pen.Restart();

                CheckEqual(0, pen.Row);
            }
        }

        public class FaceAtTests : TestFixture
        {
            public void IsTheFontTheRunsSetTheCharacterIn()
            {
                var pen = new FacedPen(Runs((2, 4, FacedMeasuringTests.KernedWide)));

                CheckTrue(ReferenceEquals(FacedMeasuringTests.Kerned, pen.FaceAt(1)));
                CheckTrue(ReferenceEquals(FacedMeasuringTests.KernedWide, pen.FaceAt(3)));
                CheckTrue(ReferenceEquals(FacedMeasuringTests.Kerned, pen.FaceAt(0)));
            }
        }
    }
}