#nullable enable

using System;
using Avalonia.Headless;
using Avalonia.Media;
using Avalonia.Media.TextFormatting;
using Avalonia.UnitTests;
using Xunit;

namespace Avalonia.Skia.UnitTests.Media.TextFormatting
{
    public class TextRunCacheTests
    {
        [Fact]
        public void Cache_Hit_Produces_Identical_Layout()
        {
            using (Start())
            {
                var text = "Hello World";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // First call: cache miss, populates cache.
                var line1 = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(line1);

                // Second call: cache hit, different paragraph width.
                var line2 = formatter.FormatLine(textSource, 0, 200.0,
                    paragraphProperties, null, cache);

                Assert.NotNull(line2);

                // Both lines should have the same text length.
                Assert.Equal(line1!.Length, line2!.Length);

                // Both lines should have the same number of text runs.
                Assert.Equal(line1.TextRuns.Count, line2.TextRuns.Count);
            }
        }

        [Fact]
        public void Full_Invalidation_Clears_Cache()
        {
            using (Start())
            {
                var text = "Hello World";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // Populate cache.
                formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                // Invalidate.
                cache.Invalidate();

                // Verify cache miss: should not throw and should produce a valid line.
                var line = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(line);
                Assert.Equal(text.Length, line!.Length);
            }
        }

        [Fact]
        public void Partial_Invalidation_Preserves_Earlier_Entries()
        {
            using (Start())
            {
                var text = "First paragraph\nSecond paragraph";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // Format first paragraph (populates cache at index 0).
                var line1 = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(line1);

                var firstLineLength = line1!.Length;

                // Format second paragraph (populates cache at firstLineLength).
                var line2 = formatter.FormatLine(textSource, firstLineLength, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(line2);

                // Invalidate from the second paragraph index.
                cache.InvalidateFrom(firstLineLength);

                // First paragraph should still be cached (cache hit).
                var line1Again = formatter.FormatLine(textSource, 0, 200.0,
                    paragraphProperties, null, cache);

                Assert.NotNull(line1Again);
                Assert.Equal(line1.Length, line1Again!.Length);

                // Second paragraph should be re-shaped (cache miss then re-populated).
                var line2Again = formatter.FormatLine(textSource, firstLineLength, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(line2Again);
                Assert.Equal(line2!.Length, line2Again!.Length);
            }
        }

        [Fact]
        public void Text_Wrapping_With_Cache_Produces_Correct_Lines()
        {
            using (Start())
            {
                var text = "The quick brown fox jumps over the lazy dog";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var wrappingProperties = new GenericTextParagraphProperties(
                    FlowDirection.LeftToRight, TextAlignment.Left, true, false,
                    defaultProperties, TextWrapping.Wrap, 0, 0, 0);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                // Format without cache.
                var linesWithout = FormatAllLines(formatter, textSource, 100.0, wrappingProperties, null);

                // Format with cache (first pass: cache miss).
                using var cache = new TextRunCache();
                var linesWith = FormatAllLines(formatter, textSource, 100.0, wrappingProperties, cache);

                Assert.Equal(linesWithout.Length, linesWith.Length);

                for (int i = 0; i < linesWithout.Length; i++)
                {
                    Assert.Equal(linesWithout[i].Length, linesWith[i].Length);
                }

                // Format with cache again (second pass: cache hit).
                var linesCacheHit = FormatAllLines(formatter, textSource, 100.0, wrappingProperties, cache);

                Assert.Equal(linesWithout.Length, linesCacheHit.Length);

                for (int i = 0; i < linesWithout.Length; i++)
                {
                    Assert.Equal(linesWithout[i].Length, linesCacheHit[i].Length);
                }
            }
        }

        [Fact]
        public void Wrapping_With_Different_Width_From_Cache()
        {
            using (Start())
            {
                var text = "The quick brown fox jumps over the lazy dog";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var wrappingProperties = new GenericTextParagraphProperties(
                    FlowDirection.LeftToRight, TextAlignment.Left, true, false,
                    defaultProperties, TextWrapping.Wrap, 0, 0, 0);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // First format: wide (cache miss, populates).
                var wideLines = FormatAllLines(formatter, textSource, 500.0, wrappingProperties, cache);

                // Second format: narrow (cache hit, different wrapping).
                var narrowLines = FormatAllLines(formatter, textSource, 80.0, wrappingProperties, cache);

                // Narrow should produce more lines.
                Assert.True(narrowLines.Length >= wideLines.Length);

                // Total characters should be the same.
                int wideTotal = 0, narrowTotal = 0;
                foreach (var l in wideLines) wideTotal += l.Length;
                foreach (var l in narrowLines) narrowTotal += l.Length;

                Assert.Equal(wideTotal, narrowTotal);
            }
        }

        [Fact]
        public void Bidi_Text_With_Cache_Produces_Correct_Results()
        {
            using (Start())
            {
                // Mixed LTR/RTL text.
                var text = "Hello \u0627\u0644\u0639\u0631\u0628\u064A\u0629 World";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                // Without cache.
                var lineWithout = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, null);

                // With cache.
                using var cache = new TextRunCache();
                var lineWith = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(lineWithout);
                Assert.NotNull(lineWith);

                Assert.Equal(lineWithout!.Length, lineWith!.Length);
                Assert.Equal(lineWithout.TextRuns.Count, lineWith.TextRuns.Count);

                // Cache hit should also produce correct results.
                var lineCacheHit = formatter.FormatLine(textSource, 0, 200.0,
                    paragraphProperties, null, cache);

                Assert.NotNull(lineCacheHit);
                Assert.Equal(lineWithout.Length, lineCacheHit!.Length);
            }
        }

        // Regression tests for the double-reorder bug (commit 2837a287):
        // When shaped runs with shared ShapedBuffer backing arrays were cached, the old
        // BidiReorderer.Reverse() call on a non-owning copy mutated the same backing array
        // that the cached run referenced.  On the next layout the cache returned the already-
        // reversed buffer but with IsReversed=false, causing BidiReorderer to reverse it a
        // second time – putting glyphs back in logical (wrong visual) order for RTL runs.

        [Fact]
        public void Bidi_Cache_Hit_Does_Not_Double_Reorder_RTL_Glyph_Clusters()
        {
            using (Start())
            {
                // LTR paragraph containing an Arabic RTL island followed by Latin text.
                // "Hello مرحبا World" – the Arabic word is at source indices 6-10.
                var text = "Hello \u0645\u0631\u062D\u0628\u0627 World";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // Cache miss: shapes and caches.
                var lineMiss = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(lineMiss);

                // Cache hit: must not double-reverse the RTL run's glyph buffer.
                var lineHit = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(lineHit);
                Assert.Equal(lineMiss!.TextRuns.Count, lineHit!.TextRuns.Count);

                for (var i = 0; i < lineMiss.TextRuns.Count; i++)
                {
                    var missRun = lineMiss.TextRuns[i] as ShapedTextRun;
                    var hitRun  = lineHit.TextRuns[i] as ShapedTextRun;

                    if (missRun == null || hitRun == null)
                        continue;

                    Assert.Equal(missRun.BidiLevel, hitRun.BidiLevel);
                    Assert.Equal(missRun.ShapedBuffer.IsLeftToRight, hitRun.ShapedBuffer.IsLeftToRight);
                    Assert.Equal(missRun.ShapedBuffer.Length, hitRun.ShapedBuffer.Length);

                    // For RTL runs the shaper produces glyphs in descending cluster order
                    // (visual right-to-left).  Double-reversal would flip them back to
                    // ascending order (logical), causing wrong rendering.
                    if (!missRun.ShapedBuffer.IsLeftToRight && missRun.ShapedBuffer.Length > 1)
                    {
                        var missFirst = missRun.ShapedBuffer[0].GlyphCluster;
                        var missLast  = missRun.ShapedBuffer[missRun.ShapedBuffer.Length - 1].GlyphCluster;
                        Assert.True(missFirst >= missLast,
                            $"Cache-miss RTL run: expected descending clusters but got first={missFirst} last={missLast}");

                        var hitFirst = hitRun.ShapedBuffer[0].GlyphCluster;
                        var hitLast  = hitRun.ShapedBuffer[hitRun.ShapedBuffer.Length - 1].GlyphCluster;
                        Assert.True(hitFirst >= hitLast,
                            $"Cache-hit RTL run: expected descending clusters but got first={hitFirst} last={hitLast}");

                        // The individual cluster values must be identical between miss and hit.
                        Assert.Equal(missFirst, hitFirst);
                        Assert.Equal(missLast,  hitLast);
                    }
                }
            }
        }

        [Fact]
        public void Bidi_Cache_Hit_Matches_No_Cache_For_Pure_RTL_Paragraph()
        {
            using (Start())
            {
                // Paragraph-level RTL: all text is Arabic so the resolved flow direction is RTL.
                // "مرحبا بالعالم" (Hello World in Arabic)
                var text = "\u0645\u0631\u062D\u0628\u0627 \u0628\u0627\u0644\u0639\u0627\u0644\u0645";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                // Reference: formatted without any cache.
                var lineNoCache = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, null);

                Assert.NotNull(lineNoCache);

                using var cache = new TextRunCache();

                var lineMiss = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                var lineHit = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                Assert.NotNull(lineMiss);
                Assert.NotNull(lineHit);
                Assert.Equal(lineNoCache!.Length, lineHit!.Length);
                Assert.Equal(lineNoCache.TextRuns.Count, lineHit.TextRuns.Count);

                for (var i = 0; i < lineNoCache.TextRuns.Count; i++)
                {
                    var refRun = lineNoCache.TextRuns[i] as ShapedTextRun;
                    var hitRun = lineHit.TextRuns[i] as ShapedTextRun;

                    if (refRun == null || hitRun == null)
                        continue;

                    Assert.Equal(refRun.BidiLevel, hitRun.BidiLevel);
                    Assert.Equal(refRun.ShapedBuffer.IsLeftToRight, hitRun.ShapedBuffer.IsLeftToRight);
                    Assert.Equal(refRun.ShapedBuffer.Length, hitRun.ShapedBuffer.Length);

                    // Glyph cluster values must be identical: no double-reversal allowed.
                    for (var j = 0; j < refRun.ShapedBuffer.Length; j++)
                    {
                        Assert.Equal(refRun.ShapedBuffer[j].GlyphCluster,
                                     hitRun.ShapedBuffer[j].GlyphCluster);
                    }
                }
            }
        }

        [Fact]
        public void TextLayout_Recreated_From_Cache_With_Bidi_Has_Same_Glyph_Order()
        {
            using (Start())
            {
                // Mixed LTR/RTL text used for two successive TextLayout instances that share a cache.
                // Before the fix, the second instance would double-reverse RTL glyph buffers.
                var text = "Hello \u0645\u0631\u062D\u0628\u0627 World";

                using var cache = new TextRunCache();

                using var layout1 = new TextLayout(text, Typeface.Default, 12,
                    textRunCache: cache);

                // Second layout: triggers cache-hit path – previously double-reordered RTL runs.
                using var layout2 = new TextLayout(text, Typeface.Default, 12,
                    textRunCache: cache);

                Assert.Equal(layout1.TextLines.Count, layout2.TextLines.Count);

                for (var lineIdx = 0; lineIdx < layout1.TextLines.Count; lineIdx++)
                {
                    var line1 = layout1.TextLines[lineIdx];
                    var line2 = layout2.TextLines[lineIdx];

                    Assert.Equal(line1.Length, line2.Length);
                    Assert.Equal(line1.TextRuns.Count, line2.TextRuns.Count);

                    for (var i = 0; i < line1.TextRuns.Count; i++)
                    {
                        var run1 = line1.TextRuns[i] as ShapedTextRun;
                        var run2 = line2.TextRuns[i] as ShapedTextRun;

                        if (run1 == null || run2 == null)
                            continue;

                        Assert.Equal(run1.BidiLevel, run2.BidiLevel);
                        Assert.Equal(run1.ShapedBuffer.IsLeftToRight, run2.ShapedBuffer.IsLeftToRight);
                        Assert.Equal(run1.ShapedBuffer.Length, run2.ShapedBuffer.Length);

                        for (var j = 0; j < run1.ShapedBuffer.Length; j++)
                        {
                            Assert.Equal(run1.ShapedBuffer[j].GlyphCluster,
                                         run2.ShapedBuffer[j].GlyphCluster);
                        }
                    }
                }
            }
        }

        [Fact]
        public void Bidi_Cache_Hit_With_Wrapping_Does_Not_Double_Reorder()
        {
            using (Start())
            {
                // Wrapped bidi text so the Wrap path through FormatLineFromCache is exercised.
                var text = "Hello \u0645\u0631\u062D\u0628\u0627 World and more text to force wrapping";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var wrappingProperties = new GenericTextParagraphProperties(
                    FlowDirection.LeftToRight, TextAlignment.Left, true, false,
                    defaultProperties, TextWrapping.Wrap, 0, 0, 0);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // Cache miss pass.
                var misLines = FormatAllLines(formatter, textSource, 80.0, wrappingProperties, cache);

                // Cache hit pass.
                var hitLines = FormatAllLines(formatter, textSource, 80.0, wrappingProperties, cache);

                Assert.Equal(misLines.Length, hitLines.Length);

                for (var lineIdx = 0; lineIdx < misLines.Length; lineIdx++)
                {
                    var missLine = misLines[lineIdx];
                    var hitLine  = hitLines[lineIdx];

                    Assert.Equal(missLine.Length, hitLine.Length);
                    Assert.Equal(missLine.TextRuns.Count, hitLine.TextRuns.Count);

                    for (var i = 0; i < missLine.TextRuns.Count; i++)
                    {
                        var missRun = missLine.TextRuns[i] as ShapedTextRun;
                        var hitRun  = hitLine.TextRuns[i] as ShapedTextRun;

                        if (missRun == null || hitRun == null)
                            continue;

                        Assert.Equal(missRun.BidiLevel, hitRun.BidiLevel);
                        Assert.Equal(missRun.ShapedBuffer.IsLeftToRight, hitRun.ShapedBuffer.IsLeftToRight);
                        Assert.Equal(missRun.ShapedBuffer.Length, hitRun.ShapedBuffer.Length);

                        for (var j = 0; j < missRun.ShapedBuffer.Length; j++)
                        {
                            Assert.Equal(missRun.ShapedBuffer[j].GlyphCluster,
                                         hitRun.ShapedBuffer[j].GlyphCluster);
                        }
                    }
                }
            }
        }

        [Fact]
        public void Dispose_Releases_Cache_Entries()
        {
            using (Start())
            {
                var text = "Hello World";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                var cache = new TextRunCache();

                // Populate cache.
                formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache);

                // Dispose should not throw.
                cache.Dispose();

                // After dispose, using the cache should still work (re-creates entries).
                using var cache2 = new TextRunCache();

                var line = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
                    paragraphProperties, null, cache2);

                Assert.NotNull(line);
            }
        }

        [Fact]
        public void Cache_With_Multiple_Paragraphs()
        {
            using (Start())
            {
                var text = "First line\nSecond line\nThird line";
                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
                var paragraphProperties = new GenericTextParagraphProperties(defaultProperties);
                var textSource = new SingleBufferTextSource(text, defaultProperties);
                var formatter = new TextFormatterImpl();

                using var cache = new TextRunCache();

                // Format all paragraphs.
                var lines = FormatAllLines(formatter, textSource, double.PositiveInfinity,
                    paragraphProperties, cache);

                Assert.True(lines.Length >= 3);

                // Format again from cache with different width.
                var lines2 = FormatAllLines(formatter, textSource, double.PositiveInfinity,
                    paragraphProperties, cache);

                Assert.Equal(lines.Length, lines2.Length);

                for (int i = 0; i < lines.Length; i++)
                {
                    Assert.Equal(lines[i].Length, lines2[i].Length);
                }
            }
        }

        [Fact]
        public void TextLayout_With_Cache_Matches_Without()
        {
            using (Start())
            {
                var text = "The quick brown fox jumps over the lazy dog";

                // Layout without cache.
                var layout1 = new TextLayout(text, Typeface.Default, 12,
                    textWrapping: TextWrapping.Wrap, maxWidth: 100);

                // Layout with cache.
                using var cache = new TextRunCache();
                var layout2 = new TextLayout(text, Typeface.Default, 12,
                    textWrapping: TextWrapping.Wrap, maxWidth: 100, textRunCache: cache);

                Assert.Equal(layout1.TextLines.Count, layout2.TextLines.Count);
                Assert.Equal(layout1.Height, layout2.Height);
                Assert.Equal(layout1.WidthIncludingTrailingWhitespace,
                    layout2.WidthIncludingTrailingWhitespace);

                // Second layout from cache with different width.
                var layout3 = new TextLayout(text, Typeface.Default, 12,
                    textWrapping: TextWrapping.Wrap, maxWidth: 80, textRunCache: cache);

                // Should still be valid (more lines due to narrower width).
                Assert.True(layout3.TextLines.Count >= layout2.TextLines.Count);
                Assert.True(layout3.Height > 0);

                layout1.Dispose();
                layout2.Dispose();
                layout3.Dispose();
            }
        }

        private static TextLine[] FormatAllLines(TextFormatterImpl formatter, ITextSource textSource,
            double paragraphWidth, TextParagraphProperties paragraphProperties, TextRunCache? cache)
        {
            var lines = new System.Collections.Generic.List<TextLine>();
            var currentIndex = 0;
            TextLine? previousLine = null;

            while (true)
            {
                var line = formatter.FormatLine(textSource, currentIndex, paragraphWidth,
                    paragraphProperties, previousLine?.TextLineBreak, cache);

                if (line == null)
                {
                    break;
                }

                lines.Add(line);
                currentIndex += line.Length;
                previousLine = line;

                if (line.TextLineBreak?.TextEndOfLine is TextEndOfParagraph)
                {
                    break;
                }
            }

            return lines.ToArray();
        }

        private static IDisposable Start()
        {
            return UnitTestApplication.Start(TestServices.MockPlatformRenderInterface
                .With(renderInterface: new PlatformRenderInterface(null),
                    fontManagerImpl: new CustomFontManagerImpl()));
        }
    }
}