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

namespace Glass.UnitTests.Typesetting
{
    public class LineWrapperTests : TestFixture
    {
        /// <summary>
        /// Letters and a space, all with zero line height, so height/maxLines cutoffs never trigger unless a test
        /// opts into <see cref="FontWithLineHeight"/> instead.
        /// </summary>
        public static SpriteFontDefinition Font() => WordMeasurerTests.TestFont();

        /// <summary>
        /// A font with a real line height, for tests of the maxHeight cutoff, which <see cref="Font"/> can't reach
        /// since SpriteFontDefinition reports zero ascent/descent unless Data sets them.
        /// </summary>
        public static SpriteFontDefinition FontWithLineHeight(int ascent, int descent)
        {
            var glyphs = new Dictionary<char, GlyphDefinition>();
            for (char letter = 'a'; letter <= 'z'; ++letter)
            {
                glyphs[letter] = new GlyphDefinition { Width = WordMeasurerTests.LetterWidth };
            }

            return new SpriteFontDefinition(new SpriteFontDefinition.Data
            {
                GlyphDefinitions = glyphs,
                InvalidGlyph = new GlyphDefinition { Width = WordMeasurerTests.InvalidGlyphWidth },
                Kernings = new Dictionary<(short, short), short>(),
                Baseline = (ushort)ascent,
                LineHeight = (ushort)(ascent + descent),
            });
        }

        // Line carries no Start of its own (like MeasuredWord), so the caller tracks it: it's wherever the line
        // before it ended.
        public static string Describe(int start, in Line line)
        {
            string flags = line.Flags == LineFlags.None ? "" : $" {line.Flags}";
            return $"{start}..{line.End} width {line.VisibleWidth}{flags}";
        }

        public static LineWrapper Wrap(StringView text, int maxWidth, IFontMetrics font = null,
            int? maxHeight = null, TextOverflow overflow = TextOverflow.Clip, int? maxLines = null)
        {
            var words = new WordMeasurer(font ?? Font(), new LineBreakIterator(text));
            return new LineWrapper(words, maxWidth, maxHeight, overflow, maxLines);
        }

        public static List<string> Lines(StringView text, int maxWidth, IFontMetrics font = null,
            int? maxHeight = null, TextOverflow overflow = TextOverflow.Clip, int? maxLines = null)
        {
            LineWrapper wrapper = Wrap(text, maxWidth, font, maxHeight, overflow, maxLines);
            var returnMe = new List<string>();
            int start = 0;
            while (wrapper.MoveNext())
            {
                returnMe.Add(Describe(start, wrapper.Current));
                start = wrapper.Current.End;
            }

            return returnMe;
        }

        public static TextOverflow? TruncationOf(StringView text, int maxWidth, IFontMetrics font = null,
            int? maxHeight = null, TextOverflow overflow = TextOverflow.Clip, int? maxLines = null)
        {
            LineWrapper wrapper = Wrap(text, maxWidth, font, maxHeight, overflow, maxLines);
            while (wrapper.MoveNext())
            {
            }

            return wrapper.Truncation;
        }

        public class CtorTests : TestFixture
        {
            public void MaxLinesLessThanOne_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new LineWrapper(new WordMeasurer(Font(), new LineBreakIterator("a")), maxWidth: 100, maxLines: 0);
            }
        }

        public class MoveNextTests : TestFixture
        {
            public void EmptyText_HasNoLines()
            {
                CheckEqual(new string[0], Lines("", maxWidth: 100));
            }

            public void WordsThatFitTogether_StayOnOneLine()
            {
                CheckEqual(new[] { "0..5 width 38" }, Lines("ab cd", maxWidth: 1000));
            }

            public void WordsThatDoNotFitTogether_WrapToANewLine_AndTheSpaceHangs()
            {
                CheckEqual(new[] { "0..3 width 19", "3..5 width 20" }, Lines("ab cd", maxWidth: 25));
            }

            public void MandatoryBreak_EndsTheLineEvenWithRoomToSpare()
            {
                CheckEqual(new[] { "0..2 width 10", "2..4 width 20" }, Lines("a\nbb", maxWidth: 1000));
            }

            public void SoftHyphenNotTaken_ShowsNoHyphenAndKerningCarriesAcross()
            {
                CheckEqual(new[] { "0..3 width 15" }, Lines($"a{LineBreakIterator.SoftHyphen}c", maxWidth: 1000));
            }

            public void SoftHyphenTaken_ShowsTheHyphenAndItsWidth()
            {
                string text = $"a{LineBreakIterator.SoftHyphen}c";

                CheckEqual(new[] { "0..2 width 13 EndsWithHyphen", "2..3 width 10" }, Lines(text, maxWidth: 12));
            }

            public void WordWiderThanMaxWidth_SplitsIntoCharacterFitChunks()
            {
                CheckEqual(new[] { "0..2 width 20", "2..4 width 20", "4..6 width 20" },
                    Lines("aaaaaa", maxWidth: 25));
            }

            public void SplitWordFollowedByMoreWords_TheLastChunkStaysOpenForThem()
            {
                CheckEqual(new[] { "0..2 width 20", "2..5 width 24" }, Lines("aaa a", maxWidth: 25));
            }

            public void OversizedWordAfterAnotherWord_ClosesTheLineBeforeSplitting()
            {
                CheckEqual(new[] { "0..2 width 10", "2..4 width 20", "4..6 width 20", "6..8 width 20" },
                    Lines("a aaaaaa", maxWidth: 25));
            }

            public void SoftHyphenEndingTheText_NeedsNoHyphen()
            {
                CheckEqual(new[] { "0..3 width 19" }, Lines($"ab{LineBreakIterator.SoftHyphen}", maxWidth: 1000));
            }

            public void SingleCharacterWiderThanMaxWidth_OverflowsSidewaysAndIsClipped()
            {
                CheckEqual(new[] { "0..1 width 10" }, Lines("a", maxWidth: 5));
                CheckEqual(TextOverflow.Clip, TruncationOf("a", maxWidth: 5));
            }

            public void MaxLinesReached_StopsEmittingAndMarksClipped()
            {
                CheckEqual(new[] { "0..2 width 20", "2..4 width 20" },
                    Lines("aaaaaa", maxWidth: 25, maxLines: 2));
                CheckEqual(TextOverflow.Clip, TruncationOf("aaaaaa", maxWidth: 25, maxLines: 2));
            }

            public void FirstLine_AlwaysShowsEvenWithNoHeightBudget()
            {
                SpriteFontDefinition font = FontWithLineHeight(ascent: 8, descent: 2);

                CheckEqual(new[] { "0..1 width 10" }, Lines("a", maxWidth: 1000, font, maxHeight: 0));
                CheckNull(TruncationOf("a", maxWidth: 1000, font, maxHeight: 0));
            }

            public void ClipOverflow_AllowsAPartlyVisibleLineButNotOneEntirelyOutOfBounds()
            {
                SpriteFontDefinition font = FontWithLineHeight(ascent: 8, descent: 2);

                CheckEqual(new[] { "0..2 width 10", "2..4 width 10" },
                    Lines("a\nb\nc", maxWidth: 1000, font, maxHeight: 15, TextOverflow.Clip));
                CheckEqual(TextOverflow.Clip,
                    TruncationOf("a\nb\nc", maxWidth: 1000, font, maxHeight: 15, TextOverflow.Clip));
            }

            public void EllipsisOverflow_NeedsTheWholeNextLineInsideTheBudget()
            {
                SpriteFontDefinition font = FontWithLineHeight(ascent: 8, descent: 2);

                CheckEqual(new[] { "0..2 width 10" },
                    Lines("a\nb\nc", maxWidth: 1000, font, maxHeight: 15, TextOverflow.Ellipsis));
            }

            public void EllipsisOverflow_AllowsALineThatFitsEntirely()
            {
                SpriteFontDefinition font = FontWithLineHeight(ascent: 8, descent: 2);

                CheckEqual(new[] { "0..2 width 10", "2..4 width 10" },
                    Lines("a\nb\nc", maxWidth: 1000, font, maxHeight: 20, TextOverflow.Ellipsis));
            }

            public void HeightBudget_CanRunOutMidSplit()
            {
                SpriteFontDefinition font = FontWithLineHeight(ascent: 8, descent: 2);

                CheckEqual(new[] { "0..2 width 20", "2..4 width 20", "4..6 width 20" },
                    Lines("aaaaaaaa", maxWidth: 25, font, maxHeight: 25));
                CheckEqual(TextOverflow.Clip, TruncationOf("aaaaaaaa", maxWidth: 25, font, maxHeight: 25));
            }
        }
    }
}