// Copyright 2019 Google LLC.
#include "include/core/SkBlurTypes.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkFont.h"
#include "include/core/SkFontMetrics.h"
#include "include/core/SkMaskFilter.h"
#include "include/core/SkPaint.h"
#include "include/core/SkSpan.h"
#include "include/core/SkString.h"
#include "include/core/SkTextBlob.h"
#include "include/core/SkTypes.h"
#include "include/private/SkTemplates.h"
#include "include/private/SkTo.h"
#include "modules/skparagraph/include/DartTypes.h"
#include "modules/skparagraph/include/Metrics.h"
#include "modules/skparagraph/include/ParagraphStyle.h"
#include "modules/skparagraph/include/TextShadow.h"
#include "modules/skparagraph/include/TextStyle.h"
#include "modules/skparagraph/src/Decorations.h"
#include "modules/skparagraph/src/ParagraphImpl.h"
#include "modules/skparagraph/src/TextLine.h"
#include "modules/skshaper/include/SkShaper.h"

#include <algorithm>
#include <iterator>
#include <limits>
#include <map>
#include <memory>
#include <tuple>
#include <type_traits>
#include <utility>

namespace skia {
namespace textlayout {

namespace {

// TODO: deal with all the intersection functionality
TextRange intersected(const TextRange& a, const TextRange& b) {
    if (a.start == b.start && a.end == b.end) return a;
    auto begin = std::max(a.start, b.start);
    auto end = std::min(a.end, b.end);
    return end >= begin ? TextRange(begin, end) : EMPTY_TEXT;
}

SkScalar littleRound(SkScalar a) {
    // This rounding is done to match Flutter tests. Must be removed..
  return SkScalarRoundToScalar(a * 100.0)/100.0;
}

TextRange operator*(const TextRange& a, const TextRange& b) {
    if (a.start == b.start && a.end == b.end) return a;
    auto begin = std::max(a.start, b.start);
    auto end = std::min(a.end, b.end);
    return end > begin ? TextRange(begin, end) : EMPTY_TEXT;
}

int compareRound(SkScalar a, SkScalar b) {
    // There is a rounding error that gets bigger when maxWidth gets bigger
    // VERY long zalgo text (> 100000) on a VERY long line (> 10000)
    // Canvas scaling affects it
    // Letter spacing affects it
    // It has to be relative to be useful
    auto base = std::max(SkScalarAbs(a), SkScalarAbs(b));
    auto diff = SkScalarAbs(a - b);
    if (nearlyZero(base) || diff / base < 0.001f) {
        return 0;
    }

    auto ra = littleRound(a);
    auto rb = littleRound(b);
    if (ra < rb) {
        return -1;
    } else {
        return 1;
    }
}

}  // namespace

TextLine::TextLine(ParagraphImpl* owner,
                   SkVector offset,
                   SkVector advance,
                   BlockRange blocks,
                   TextRange textExcludingSpaces,
                   TextRange text,
                   TextRange textIncludingNewlines,
                   ClusterRange clusters,
                   ClusterRange clustersWithGhosts,
                   SkScalar widthWithSpaces,
                   InternalLineMetrics sizes)
        : fOwner(owner)
        , fBlockRange(blocks)
        , fTextExcludingSpaces(textExcludingSpaces)
        , fText(text)
        , fTextIncludingNewlines(textIncludingNewlines)
        , fClusterRange(clusters)
        , fGhostClusterRange(clustersWithGhosts)
        , fRunsInVisualOrder()
        , fAdvance(advance)
        , fOffset(offset)
        , fShift(0.0)
        , fWidthWithSpaces(widthWithSpaces)
        , fEllipsis(nullptr)
        , fSizes(sizes)
        , fHasBackground(false)
        , fHasShadows(false)
        , fHasDecorations(false)
        , fAscentStyle(LineMetricStyle::CSS)
        , fDescentStyle(LineMetricStyle::CSS)
        , fTextBlobCachePopulated(false) {
    // Reorder visual runs
    auto& start = owner->cluster(fGhostClusterRange.start);
    auto& end = owner->cluster(fGhostClusterRange.end - 1);
    size_t numRuns = end.runIndex() - start.runIndex() + 1;

    for (BlockIndex index = fBlockRange.start; index < fBlockRange.end; ++index) {
        auto b = fOwner->styles().begin() + index;
        if (b->fStyle.isPlaceholder()) {
            continue;
        }
        if (b->fStyle.hasBackground()) {
            fHasBackground = true;
        }
        if (b->fStyle.getDecorationType() != TextDecoration::kNoDecoration) {
            fHasDecorations = true;
        }
        if (b->fStyle.getShadowNumber() > 0) {
            fHasShadows = true;
        }
    }

    // Get the logical order

    // This is just chosen to catch the common/fast cases. Feel free to tweak.
    constexpr int kPreallocCount = 4;
    SkAutoSTArray<kPreallocCount, SkUnicode::BidiLevel> runLevels(numRuns);
    size_t runLevelsIndex = 0;
    for (auto runIndex = start.runIndex(); runIndex <= end.runIndex(); ++runIndex) {
        auto& run = fOwner->run(runIndex);
        runLevels[runLevelsIndex++] = run.fBidiLevel;
        fMaxRunMetrics.add(
            InternalLineMetrics(run.fFontMetrics.fAscent, run.fFontMetrics.fDescent, run.fFontMetrics.fLeading));
    }
    SkASSERT(runLevelsIndex == numRuns);

    SkAutoSTArray<kPreallocCount, int32_t> logicalOrder(numRuns);

    // TODO: hide all these logic in SkUnicode?
  fOwner->getUnicode()->reorderVisual(runLevels.data(), numRuns, logicalOrder.data());
    auto firstRunIndex = start.runIndex();
    for (auto index : logicalOrder) {
        fRunsInVisualOrder.push_back(firstRunIndex + index);
    }

    // TODO: This is the fix for flutter. Must be removed...
    for (auto cluster = &start; cluster != &end; ++cluster) {
        if (!cluster->run().isPlaceholder()) {
            fShift += cluster->getHalfLetterSpacing();
            break;
        }
    }
}

SkRect TextLine::paint(SkCanvas* textCanvas, SkScalar x, SkScalar y) {
    auto bounds = SkRect::MakeEmpty();
    if (this->empty()) {
        return bounds;
    }

    if (fHasBackground) {
        this->iterateThroughVisualRuns(false,
            [textCanvas, x, y, this]
            (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
                *runWidthInLine = this->iterateThroughSingleRunByStyles(
                run, runOffsetInLine, textRange, StyleType::kBackground,
                [textCanvas, x, y, this](TextRange textRange, const TextStyle& style, const ClipContext& context) {
                    this->paintBackground(textCanvas, x, y, textRange, style, context);
                });
            return true;
            });
    }

    if (fHasShadows) {
        this->iterateThroughVisualRuns(false,
            [textCanvas, x, y, &bounds, this]
            (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
            *runWidthInLine = this->iterateThroughSingleRunByStyles(
                run, runOffsetInLine, textRange, StyleType::kShadow,
                [textCanvas, x, y, &bounds, this](TextRange textRange, const TextStyle& style, const ClipContext& context) {
                    auto shadowBounds = this->paintShadow(textCanvas, x, y, textRange, style, context);
                    bounds.joinPossiblyEmptyRect(shadowBounds);
                });
            return true;
            });
    }

    ensureTextBlobCachePopulated();

    for (auto& record : fTextBlobCache) {
        record.paint(textCanvas, x, y);
        SkRect recordBounds = record.fBounds;
        recordBounds.offset(x + this->offset().fX, y + this->offset().fY);
        bounds.joinPossiblyEmptyRect(recordBounds);
    }

    if (fHasDecorations) {
        this->iterateThroughVisualRuns(false,
            [textCanvas, x, y, this]
            (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
                *runWidthInLine = this->iterateThroughSingleRunByStyles(
                run, runOffsetInLine, textRange, StyleType::kDecorations,
                [textCanvas, x, y, this](TextRange textRange, const TextStyle& style, const ClipContext& context) {
                    this->paintDecorations(textCanvas, x, y, textRange, style, context);
                });
                return true;
        });
    }

    return bounds;
}

void TextLine::ensureTextBlobCachePopulated() {
    if (fTextBlobCachePopulated) {
        return;
    }
    this->iterateThroughVisualRuns(false,
            [this]
            (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
            if (run->placeholderStyle() != nullptr) {
                *runWidthInLine = run->advance().fX;
                return true;
            }
            *runWidthInLine = this->iterateThroughSingleRunByStyles(
            run, runOffsetInLine, textRange, StyleType::kForeground,
            [this](TextRange textRange, const TextStyle& style, const ClipContext& context) {
                this->buildTextBlob(textRange, style, context);
            });
            return true;
        });
    fTextBlobCachePopulated = true;
}

void TextLine::format(TextAlign align, SkScalar maxWidth) {
    SkScalar delta = maxWidth - this->width();
    if (delta <= 0) {
        return;
    }

    // We do nothing for left align
    if (align == TextAlign::kJustify) {
        if (!this->endsWithHardLineBreak()) {
            this->justify(maxWidth);
        } else if (fOwner->paragraphStyle().getTextDirection() == TextDirection::kRtl) {
            // Justify -> Right align
            fShift = delta;
        }
    } else if (align == TextAlign::kRight) {
        fShift = delta;
    } else if (align == TextAlign::kCenter) {
        fShift = delta / 2;
    }
}

void TextLine::scanStyles(StyleType styleType, const RunStyleVisitor& visitor) {
    if (this->empty()) {
        return;
    }

    this->iterateThroughVisualRuns(false,
        [this, visitor, styleType](const Run* run, SkScalar runOffset, TextRange textRange, SkScalar* width) {
            *width = this->iterateThroughSingleRunByStyles(
                run, runOffset, textRange, styleType,
                [visitor](TextRange textRange, const TextStyle& style, const ClipContext& context) {
                    visitor(textRange, style, context);
                });
            return true;
        });
}

SkRect TextLine::extendHeight(const ClipContext& context) const {
    SkRect result = context.clip;
    result.fBottom += std::max(this->fMaxRunMetrics.height() - this->height(), 0.0f);
    return result;
}

SkScalar TextLine::metricsWithoutMultiplier(TextHeightBehavior correction) {

    if (this->fSizes.getForceStrut()) {
        return 0;
    }

    InternalLineMetrics result;
    this->iterateThroughVisualRuns(true,
        [&result](const Run* run, SkScalar runOffset, TextRange textRange, SkScalar* width) {
        InternalLineMetrics runMetrics(run->ascent(), run->descent(), run->leading());
        result.add(runMetrics);
        return true;
    });
    SkScalar delta = 0;
    if (correction  == TextHeightBehavior::kDisableFirstAscent) {
        delta += (this->fSizes.fAscent - result.fAscent);
        this->fSizes.fAscent = result.fAscent;
        this->fAscentStyle = LineMetricStyle::Typographic;
    } else if (correction  == TextHeightBehavior::kDisableLastDescent) {
        delta -= (this->fSizes.fDescent - result.fDescent);
        this->fSizes.fDescent = result.fDescent;
        this->fDescentStyle = LineMetricStyle::Typographic;
    }
    fAdvance.fY += delta;
    return delta;
}

void TextLine::buildTextBlob(TextRange textRange, const TextStyle& style, const ClipContext& context) {
    if (context.run->placeholderStyle() != nullptr) {
        return;
    }

    fTextBlobCache.emplace_back();
    TextBlobRecord& record = fTextBlobCache.back();

    if (style.hasForeground()) {
        record.fPaint = style.getForeground();
    } else {
        record.fPaint.setColor(style.getColor());
    }
    record.fVisitor_Run = context.run;
    record.fVisitor_Pos = context.pos;

    // TODO: This is the change for flutter, must be removed later
    SkTextBlobBuilder builder;
    context.run->copyTo(builder, SkToU32(context.pos), context.size);
    record.fClippingNeeded = context.clippingNeeded;
    if (context.clippingNeeded) {
        record.fClipRect = extendHeight(context).makeOffset(this->offset());
    } else {
        record.fClipRect = context.clip.makeOffset(this->offset());
    }

    SkScalar correctedBaseline = SkScalarFloorToScalar(this->baseline() + 0.5);
    record.fBlob = builder.make();
    if (record.fBlob != nullptr) {
        record.fBounds.joinPossiblyEmptyRect(record.fBlob->bounds());
    }

    record.fOffset = SkPoint::Make(this->offset().fX + context.fTextShift,
                                   this->offset().fY + correctedBaseline);
}

void TextLine::TextBlobRecord::paint(SkCanvas* canvas, SkScalar x, SkScalar y) {
    if (fClippingNeeded) {
        canvas->save();
        canvas->clipRect(fClipRect.makeOffset(x, y));
    }
    canvas->drawTextBlob(fBlob, x + fOffset.x(), y + fOffset.y(), fPaint);
    if (fClippingNeeded) {
        canvas->restore();
    }
}

void TextLine::paintBackground(SkCanvas* canvas, SkScalar x, SkScalar y, TextRange textRange, const TextStyle& style, const ClipContext& context) const {
    if (style.hasBackground()) {
        canvas->drawRect(context.clip.makeOffset(this->offset() + SkPoint::Make(x, y)), style.getBackground());
    }
}

SkRect TextLine::paintShadow(SkCanvas* canvas, SkScalar x, SkScalar y, TextRange textRange, const TextStyle& style, const ClipContext& context) const {

    SkScalar correctedBaseline = SkScalarFloorToScalar(this->baseline() + 0.5);
    SkRect shadowBounds = SkRect::MakeEmpty();

    for (TextShadow shadow : style.getShadows()) {
        if (!shadow.hasShadow()) continue;

        SkPaint paint;
        paint.setColor(shadow.fColor);
        if (shadow.fBlurSigma != 0.0) {
            auto filter = SkMaskFilter::MakeBlur(kNormal_SkBlurStyle,
                                                 SkDoubleToScalar(shadow.fBlurSigma), false);
            paint.setMaskFilter(filter);
        }

        SkTextBlobBuilder builder;
        context.run->copyTo(builder, context.pos, context.size);

        if (context.clippingNeeded) {
            canvas->save();
            SkRect clip = extendHeight(context);
            clip.offset(this->offset());
            canvas->clipRect(clip);
        }
        auto blob = builder.make();
        if (blob != nullptr) {
            auto bounds = blob->bounds();
            bounds.offset(
                   x + this->offset().fX + shadow.fOffset.x(),
                   y + this->offset().fY + shadow.fOffset.y()
                );
            shadowBounds.joinPossiblyEmptyRect(bounds);
        }
        canvas->drawTextBlob(blob,
            x + this->offset().fX + shadow.fOffset.x() + context.fTextShift,
            y + this->offset().fY + shadow.fOffset.y() + correctedBaseline,
            paint);
        if (context.clippingNeeded) {
            canvas->restore();
        }
    }

    return shadowBounds;
}

void TextLine::paintDecorations(SkCanvas* canvas, SkScalar x, SkScalar y, TextRange textRange, const TextStyle& style, const ClipContext& context) const {

    SkAutoCanvasRestore acr(canvas, true);
    canvas->translate(x + this->offset().fX, y + this->offset().fY);
    Decorations decorations;
    SkScalar correctedBaseline = SkScalarFloorToScalar(this->baseline() + 0.5);
    decorations.paint(canvas, style, context, correctedBaseline);
}

void TextLine::justify(SkScalar maxWidth) {
    // Count words and the extra spaces to spread across the line
    // TODO: do it at the line breaking?..
    size_t whitespacePatches = 0;
    SkScalar textLen = 0;
    bool whitespacePatch = false;
    this->iterateThroughClustersInGlyphsOrder(false, false,
        [&whitespacePatches, &textLen, &whitespacePatch](const Cluster* cluster, bool ghost) {
            if (cluster->isWhitespaceBreak()) {
                if (!whitespacePatch) {
                    whitespacePatch = true;
                    ++whitespacePatches;
                }
            } else {
                whitespacePatch = false;
            }
            textLen += cluster->width();
            return true;
        });

    if (whitespacePatches == 0) {
        return;
    }

    SkScalar step = (maxWidth - textLen) / whitespacePatches;
    SkScalar shift = 0;

    // Deal with the ghost spaces
    auto ghostShift = maxWidth - this->fAdvance.fX;
    // Spread the extra whitespaces
    whitespacePatch = false;
    this->iterateThroughClustersInGlyphsOrder(false, true, [&](const Cluster* cluster, bool ghost) {

        if (ghost) {
            if (cluster->run().leftToRight()) {
                shiftCluster(cluster, ghostShift, ghostShift);
            }
            return true;
        }

        auto prevShift = shift;
        if (cluster->isWhitespaceBreak()) {
            if (!whitespacePatch) {
                shift += step;
                whitespacePatch = true;
                --whitespacePatches;
            }
        } else {
            whitespacePatch = false;
        }
        shiftCluster(cluster, shift, prevShift);
        return true;
    });

    SkAssertResult(nearlyEqual(shift, maxWidth - textLen));
    SkASSERT(whitespacePatches == 0);

    this->fWidthWithSpaces += ghostShift;
    this->fAdvance.fX = maxWidth;
}

void TextLine::shiftCluster(const Cluster* cluster, SkScalar shift, SkScalar prevShift) {

    auto& run = cluster->run();
    auto start = cluster->startPos();
    auto end = cluster->endPos();

    if (end == run.size()) {
        // Set the same shift for the fake last glyph (to avoid all extra checks)
        ++end;
    }

    if (run.fJustificationShifts.empty()) {
        // Do not fill this array until needed
        run.fJustificationShifts.push_back_n(run.size() + 1, { 0, 0 });
    }

    for (size_t pos = start; pos < end; ++pos) {
        run.fJustificationShifts[pos] = { shift, prevShift };
    }
}

void TextLine::createEllipsis(SkScalar maxWidth, const SkString& ellipsis, bool) {
    // Replace some clusters with the ellipsis
    // Go through the clusters in the reverse logical order
    // taking off cluster by cluster until the ellipsis fits
    SkScalar width = fAdvance.fX;

    auto attachEllipsis = [&](const Cluster* cluster){
        // Shape the ellipsis
        std::unique_ptr<Run> run = shapeEllipsis(ellipsis, cluster->run());
        run->fClusterStart = cluster->textRange().start;
      run->setOwner(fOwner);

        // See if it fits
        if (width + run->advance().fX > maxWidth) {
            width -= cluster->width();
            // Continue if it's not
            return false;
        }

        fEllipsis = std::move(run);
        fEllipsis->shift(width, 0);
        fAdvance.fX = width;
        return true;
    };

    iterateThroughClustersInGlyphsOrder(
        true, false, [&](const Cluster* cluster, bool ghost) {
            return !attachEllipsis(cluster);
        });

    if (!fEllipsis) {
        // Weird situation: just the ellipsis on the line (if it fits)
        attachEllipsis(&fOwner->cluster(clusters().start));
    }
}

std::unique_ptr<Run> TextLine::shapeEllipsis(const SkString& ellipsis, const Run& run) {

    class ShapeHandler final : public SkShaper::RunHandler {
    public:
        ShapeHandler(SkScalar lineHeight, bool useHalfLeading, const SkString& ellipsis)
            : fRun(nullptr), fLineHeight(lineHeight), fUseHalfLeading(useHalfLeading), fEllipsis(ellipsis) {}
        Run* run() & { return fRun.get(); }
        std::unique_ptr<Run> run() && { return std::move(fRun); }

    private:
        void beginLine() override {}

        void runInfo(const RunInfo&) override {}

        void commitRunInfo() override {}

        Buffer runBuffer(const RunInfo& info) override {
            SkASSERT(!fRun);
            fRun = std::make_unique<Run>(nullptr, info, 0, fLineHeight, fUseHalfLeading, 0, 0);
            return fRun->newRunBuffer();
        }

        void commitRunBuffer(const RunInfo& info) override {
            fRun->fAdvance.fX = info.fAdvance.fX;
            fRun->fAdvance.fY = fRun->advance().fY;
            fRun->fPlaceholderIndex = std::numeric_limits<size_t>::max();
            fRun->fEllipsis = true;
        }

        void commitLine() override {}

        std::unique_ptr<Run> fRun;
        SkScalar fLineHeight;
        bool fUseHalfLeading;
        SkString fEllipsis;
    };

    ShapeHandler handler(run.heightMultiplier(), run.useHalfLeading(), ellipsis);
    std::unique_ptr<SkShaper> shaper = SkShaper::MakeShapeDontWrapOrReorder();
    SkASSERT_RELEASE(shaper != nullptr);
    shaper->shape(ellipsis.c_str(), ellipsis.size(), run.font(), true,
                  std::numeric_limits<SkScalar>::max(), &handler);
    handler.run()->fTextRange = TextRange(0, ellipsis.size());
    handler.run()->fOwner = fOwner;
    return std::move(handler).run();
}

TextLine::ClipContext TextLine::measureTextInsideOneRun(TextRange textRange,
                                                        const Run* run,
                                                        SkScalar runOffsetInLine,
                                                        SkScalar textOffsetInRunInLine,
                                                        bool includeGhostSpaces,
                                                        bool limitToGraphemes) const {
    ClipContext result = { run, 0, run->size(), 0, SkRect::MakeEmpty(), 0, false };

    if (run->fEllipsis) {
        // Both ellipsis and placeholders can only be measured as one glyph
        SkASSERT(textRange == run->textRange());
        result.fTextShift = runOffsetInLine;
        result.clip = SkRect::MakeXYWH(runOffsetInLine,
                                       sizes().runTop(run, this->fAscentStyle),
                                       run->advance().fX,
                                       run->calculateHeight(this->fAscentStyle,this->fDescentStyle));
        return result;
    } else if (run->isPlaceholder()) {
        if (SkScalarIsFinite(run->fFontMetrics.fAscent)) {
          result.clip = SkRect::MakeXYWH(runOffsetInLine,
                                         sizes().runTop(run, this->fAscentStyle),
                                         run->advance().fX,
                                         run->calculateHeight(this->fAscentStyle,this->fDescentStyle));
        } else {
            result.clip = SkRect::MakeXYWH(runOffsetInLine, run->fFontMetrics.fAscent, run->advance().fX, 0);
        }
        return result;
    }
    // Find [start:end] clusters for the text
    Cluster* start = nullptr;
    Cluster* end = nullptr;
    do {
        bool found;
        ClusterIndex startIndex;
        ClusterIndex endIndex;
        std::tie(found, startIndex, endIndex) = run->findLimitingClusters(textRange);
        if (!found) {
            return result;
        }
        start = &fOwner->cluster(startIndex);
        end = &fOwner->cluster(endIndex);

        if (!limitToGraphemes) {
            break;
        }

        // Update textRange by cluster edges
        if (run->leftToRight()) {
            if (textRange.start != start->textRange().start) {
                textRange.start = start->textRange().end;
            }
            textRange.end = end->textRange().end;
        } else {
            if (textRange.start != end->textRange().start) {
                textRange.start = end->textRange().end;
            }
            textRange.end = start->textRange().end;
        }

        std::tie(found, startIndex, endIndex) = run->findLimitingGraphemes(textRange);
        if (startIndex == textRange.start && endIndex == textRange.end) {
            break;
        }

        // Some clusters are inside graphemes and we need to adjust them
        //SkDebugf("Correct range: [%d:%d) -> [%d:%d)\n", textRange.start, textRange.end, startIndex, endIndex);
        textRange.start = startIndex;
        textRange.end = endIndex;

        // Move the start until it's on the grapheme edge (and glypheme, too)
    } while (true);

    result.pos = start->startPos();
    result.size = (end->isHardBreak() ? end->startPos() : end->endPos()) - start->startPos();

    auto textStartInRun = run->positionX(start->startPos());
    auto textStartInLine = runOffsetInLine + textOffsetInRunInLine;
/*
    if (!run->fJustificationShifts.empty()) {
        SkDebugf("Justification for [%d:%d)\n", textRange.start, textRange.end);
        for (auto i = result.pos; i < result.pos + result.size; ++i) {
            auto j = run->fJustificationShifts[i];
            SkDebugf("[%d] = %f %f\n", i, j.fX, j.fY);
        }
    }
*/
    // Calculate the clipping rectangle for the text with cluster edges
    // There are 2 cases:
    // EOL (when we expect the last cluster clipped without any spaces)
    // Anything else (when we want the cluster width contain all the spaces -
    // coming from letter spacing or word spacing or justification)
    result.clip =
            SkRect::MakeXYWH(0,
                             sizes().runTop(run, this->fAscentStyle),
                             run->calculateWidth(result.pos, result.pos + result.size, false),
                             run->calculateHeight(this->fAscentStyle,this->fDescentStyle));

    // Correct the width in case the text edges don't match clusters
    // TODO: This is where we get smart about selecting a part of a cluster
    //  by shaping each grapheme separately and then use the result sizes
    //  to calculate the proportions
    auto leftCorrection = start->sizeToChar(textRange.start);
    auto rightCorrection = end->sizeFromChar(textRange.end - 1);
    result.clip.fLeft += leftCorrection;
    result.clip.fRight -= rightCorrection;
    result.clippingNeeded = leftCorrection != 0 || rightCorrection != 0;

    textStartInLine -= leftCorrection;
    result.clip.offset(textStartInLine, 0);

    if (compareRound(result.clip.fRight, fAdvance.fX) > 0 && !includeGhostSpaces) {
        // There are few cases when we need it.
        // The most important one: we measure the text with spaces at the end (or at the beginning in RTL)
        // and we should ignore these spaces
        if (run->leftToRight()) {
            // We only use this member for LTR
            result.fExcludedTrailingSpaces = std::max(result.clip.fRight - fAdvance.fX, 0.0f);
        }
        result.clippingNeeded = true;
        result.clip.fRight = fAdvance.fX;
    }

    if (result.clip.width() < 0) {
        // Weird situation when glyph offsets move the glyph to the left
        // (happens with zalgo texts, for instance)
        result.clip.fRight = result.clip.fLeft;
    }

    // The text must be aligned with the lineOffset
    result.fTextShift = textStartInLine - textStartInRun;

    return result;
}

void TextLine::iterateThroughClustersInGlyphsOrder(bool reversed,
                                                   bool includeGhosts,
                                                   const ClustersVisitor& visitor) const {
    // Walk through the clusters in the logical order (or reverse)
    SkSpan<const size_t> runs(fRunsInVisualOrder.data(), fRunsInVisualOrder.size());
    bool ignore = false;
    directional_for_each(runs, !reversed, [&](decltype(runs[0]) r) {
        if (ignore) return;
        auto run = this->fOwner->run(r);
        auto trimmedRange = fClusterRange.intersection(run.clusterRange());
        auto trailedRange = fGhostClusterRange.intersection(run.clusterRange());
        SkASSERT(trimmedRange.start == trailedRange.start);

        auto trailed = fOwner->clusters(trailedRange);
        auto trimmed = fOwner->clusters(trimmedRange);
        directional_for_each(trailed, reversed != run.leftToRight(), [&](Cluster& cluster) {
            if (ignore) return;
            bool ghost =  &cluster >= trimmed.end();
            if (!includeGhosts && ghost) {
                return;
            }
            if (!visitor(&cluster, ghost)) {
                ignore = true;
                return;
            }
        });
    });
}

SkScalar TextLine::iterateThroughSingleRunByStyles(const Run* run,
                                                   SkScalar runOffset,
                                                   TextRange textRange,
                                                   StyleType styleType,
                                                   const RunStyleVisitor& visitor) const {

    if (run->fEllipsis) {
        // Extra efforts to get the ellipsis text style
        ClipContext clipContext = this->measureTextInsideOneRun(run->textRange(), run, runOffset,
                                                                0, false, true);
        TextRange testRange(run->fClusterStart, run->fClusterStart + 1);
        for (BlockIndex index = fBlockRange.start; index < fBlockRange.end; ++index) {
           auto block = fOwner->styles().begin() + index;
           auto intersect = intersected(block->fRange, testRange);
           if (intersect.width() > 0) {
               visitor(textRange, block->fStyle, clipContext);
               return run->advance().fX;
           }
        }
        SkASSERT(false);
    }

    if (styleType == StyleType::kNone) {
        ClipContext clipContext = this->measureTextInsideOneRun(textRange, run, runOffset,
                                                                0, false, true);
        if (clipContext.clip.height() > 0) {
            visitor(textRange, TextStyle(), clipContext);
            return clipContext.clip.width();
        } else {
            return 0;
        }
    }

    TextIndex start = EMPTY_INDEX;
    size_t size = 0;
    const TextStyle* prevStyle = nullptr;
    SkScalar textOffsetInRun = 0;

    const BlockIndex blockRangeSize = fBlockRange.end - fBlockRange.start;
    for (BlockIndex index = 0; index <= blockRangeSize; ++index) {

        TextRange intersect;
        TextStyle* style = nullptr;
        if (index < blockRangeSize) {
            auto block = fOwner->styles().begin() +
                 (run->leftToRight() ? fBlockRange.start + index : fBlockRange.end - index - 1);

            // Get the text
            intersect = intersected(block->fRange, textRange);
            if (intersect.width() == 0) {
                if (start == EMPTY_INDEX) {
                    // This style is not applicable to the text yet
                    continue;
                } else {
                    // We have found all the good styles already
                    // but we need to process the last one of them
                    intersect = TextRange(start, start + size);
                    index = fBlockRange.end;
                }
            } else {
                // Get the style
                style = &block->fStyle;
                if (start != EMPTY_INDEX && style->matchOneAttribute(styleType, *prevStyle)) {
                    size += intersect.width();
                    // RTL text intervals move backward
                    start = std::min(intersect.start, start);
                    continue;
                } else if (start == EMPTY_INDEX ) {
                    // First time only
                    prevStyle = style;
                    size = intersect.width();
                    start = intersect.start;
                    continue;
                }
            }
        } else if (prevStyle != nullptr) {
            // This is the last style
        } else {
            break;
        }

        // We have the style and the text
        auto runStyleTextRange = TextRange(start, start + size);
        // Measure the text
        ClipContext clipContext = this->measureTextInsideOneRun(runStyleTextRange, run, runOffset,
                                                                textOffsetInRun, false, true);
        if (clipContext.clip.height() == 0) {
            continue;
        }
        visitor(runStyleTextRange, *prevStyle, clipContext);
        textOffsetInRun += clipContext.clip.width();

        // Start all over again
        prevStyle = style;
        start = intersect.start;
        size = intersect.width();
    }
    return textOffsetInRun;
}

void TextLine::iterateThroughVisualRuns(bool includingGhostSpaces, const RunVisitor& visitor) const {

    // Walk through all the runs that intersect with the line in visual order
    SkScalar width = 0;
    SkScalar runOffset = 0;
    SkScalar totalWidth = 0;
    auto textRange = includingGhostSpaces ? this->textWithNewlines() : this->trimmedText();
    for (auto& runIndex : fRunsInVisualOrder) {

        const auto run = &this->fOwner->run(runIndex);
        auto lineIntersection = intersected(run->textRange(), textRange);
        if (lineIntersection.width() == 0 && this->width() != 0) {
            // TODO: deal with empty runs in a better way
            continue;
        }
        if (!run->leftToRight() && runOffset == 0 && includingGhostSpaces) {
            // runOffset does not take in account a possibility
            // that RTL run could start before the line (trailing spaces)
            // so we need to do runOffset -= "trailing whitespaces length"
            TextRange whitespaces = intersected(
                    TextRange(fTextExcludingSpaces.end, fTextIncludingNewlines.end), run->fTextRange);
            if (whitespaces.width() > 0) {
                auto whitespacesLen = measureTextInsideOneRun(whitespaces, run, runOffset, 0, true, false).clip.width();
                runOffset -= whitespacesLen;
            }
        }
        runOffset += width;
        totalWidth += width;
        if (!visitor(run, runOffset, lineIntersection, &width)) {
            return;
        }
    }

    runOffset += width;
    totalWidth += width;

    if (this->ellipsis() != nullptr) {
        if (visitor(ellipsis(), runOffset, ellipsis()->textRange(), &width)) {
            totalWidth += width;
        }
    }

    // This is a very important assert!
    // It asserts that 2 different ways of calculation come with the same results
    if (!includingGhostSpaces && compareRound(totalWidth, this->width()) != 0) {
        SkDebugf("ASSERT: %f != %f\n", totalWidth, this->width());
        SkASSERT(false);
    }
}

SkVector TextLine::offset() const {
    return fOffset + SkVector::Make(fShift, 0);
}

LineMetrics TextLine::getMetrics() const {
    LineMetrics result;

    // Fill out the metrics
    result.fStartIndex = fTextExcludingSpaces.start;
    result.fEndExcludingWhitespaces = fTextExcludingSpaces.end;
    result.fEndIndex = fText.end;
    result.fEndIncludingNewline = fTextIncludingNewlines.end;
    result.fHardBreak = endsWithHardLineBreak();
    result.fAscent = - fMaxRunMetrics.ascent();
    result.fDescent = fMaxRunMetrics.descent();
    result.fUnscaledAscent = - fMaxRunMetrics.ascent(); // TODO: implement
    result.fHeight = littleRound(fAdvance.fY);
    result.fWidth = littleRound(fAdvance.fX);
    result.fLeft = this->offset().fX;
    // This is Flutter definition of a baseline
    result.fBaseline = this->offset().fY + this->height() - this->sizes().descent();
    result.fLineNumber = this - fOwner->lines().begin();

    // Fill out the style parts
    this->iterateThroughVisualRuns(false,
        [this, &result]
        (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
        if (run->placeholderStyle() != nullptr) {
            *runWidthInLine = run->advance().fX;
            return true;
        }
        *runWidthInLine = this->iterateThroughSingleRunByStyles(
        run, runOffsetInLine, textRange, StyleType::kForeground,
        [&result, &run](TextRange textRange, const TextStyle& style, const ClipContext& context) {
            SkFontMetrics fontMetrics;
            run->fFont.getMetrics(&fontMetrics);
            StyleMetrics styleMetrics(&style, fontMetrics);
            result.fLineMetrics.emplace(textRange.start, styleMetrics);
        });
        return true;
    });

    return result;
}

bool TextLine::isFirstLine() {
    return this == &fOwner->lines().front();
}

bool TextLine::isLastLine() {
    return this == &fOwner->lines().back();
}

bool TextLine::endsWithHardLineBreak() const {
    // TODO: For some reason Flutter imagines a hard line break at the end of the last line.
    //  To be removed...
    return fOwner->cluster(fGhostClusterRange.end - 1).isHardBreak() ||
           fEllipsis != nullptr ||
           fGhostClusterRange.end == fOwner->clusters().size() - 1;
}

void TextLine::getRectsForRange(TextRange textRange0,
                                RectHeightStyle rectHeightStyle,
                                RectWidthStyle rectWidthStyle,
                                std::vector<TextBox>& boxes)
{
    const Run* lastRun = nullptr;
    auto startBox = boxes.size();
    this->iterateThroughVisualRuns(true,
        [textRange0, rectHeightStyle, rectWidthStyle, &boxes, &lastRun, startBox, this]
        (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
        *runWidthInLine = this->iterateThroughSingleRunByStyles(
        run, runOffsetInLine, textRange, StyleType::kNone,
        [run, runOffsetInLine, textRange0, rectHeightStyle, rectWidthStyle, &boxes, &lastRun, startBox, this]
        (TextRange textRange, const TextStyle& style, const TextLine::ClipContext& lineContext) {

            auto intersect = textRange * textRange0;
            if (intersect.empty()) {
                return true;
            }

            auto paragraphStyle = fOwner->paragraphStyle();

            // Found a run that intersects with the text
            auto context = this->measureTextInsideOneRun(intersect, run, runOffsetInLine, 0, true, true);
            SkRect clip = context.clip;
            clip.offset(lineContext.fTextShift - context.fTextShift, 0);

            switch (rectHeightStyle) {
                case RectHeightStyle::kMax:
                    // TODO: Change it once flutter rolls into google3
                    //  (probably will break things if changed before)
                    clip.fBottom = this->height();
                    clip.fTop = this->sizes().delta();
                    break;
                case RectHeightStyle::kIncludeLineSpacingTop: {
                    if (isFirstLine()) {
                        auto verticalShift =  this->sizes().runTop(context.run, LineMetricStyle::Typographic);
                        clip.fTop += verticalShift;
                    }
                    break;
                }
                case RectHeightStyle::kIncludeLineSpacingMiddle: {
                    auto verticalShift =  this->sizes().runTop(context.run, LineMetricStyle::Typographic);
                    clip.fTop += isFirstLine() ? verticalShift : verticalShift / 2;
                    clip.fBottom += isLastLine() ? 0 : verticalShift / 2;
                    break;
                 }
                case RectHeightStyle::kIncludeLineSpacingBottom: {
                    auto verticalShift =  this->sizes().runTop(context.run, LineMetricStyle::Typographic);
                    clip.offset(0, verticalShift);
                    if (isLastLine()) {
                        clip.fBottom -= verticalShift;
                    }
                    break;
                }
                case RectHeightStyle::kStrut: {
                    const auto& strutStyle = paragraphStyle.getStrutStyle();
                    if (strutStyle.getStrutEnabled()
                        && strutStyle.getFontSize() > 0) {
                        auto strutMetrics = fOwner->strutMetrics();
                        auto top = this->baseline();
                        clip.fTop = top + strutMetrics.ascent();
                        clip.fBottom = top + strutMetrics.descent();
                    }
                }
                break;
                case RectHeightStyle::kTight: {
                    if (run->fHeightMultiplier <= 0) {
                        break;
                    }
                    const auto effectiveBaseline = this->baseline() + this->sizes().delta();
                    clip.fTop = effectiveBaseline + run->ascent();
                    clip.fBottom = effectiveBaseline + run->descent();
                }
                break;
                default:
                    SkASSERT(false);
                break;
            }

            // Separate trailing spaces and move them in the default order of the paragraph
            // in case the run order and the paragraph order don't match
            SkRect trailingSpaces = SkRect::MakeEmpty();
            if (this->trimmedText().end <this->textWithNewlines().end && // Line has trailing space
                this->textWithNewlines().end == intersect.end &&         // Range is at the end of the line
                this->trimmedText().end > intersect.start)               // Range has more than just spaces
            {
                auto delta = this->spacesWidth();
                trailingSpaces = SkRect::MakeXYWH(0, 0, 0, 0);
                // There are trailing spaces in this run
                if (paragraphStyle.getTextAlign() == TextAlign::kJustify && isLastLine())
                {
                    // TODO: this is just a patch. Make it right later (when it's clear what and how)
                    trailingSpaces = clip;
                    if(run->leftToRight()) {
                        trailingSpaces.fLeft = this->width();
                        clip.fRight = this->width();
                    } else {
                        trailingSpaces.fRight = 0;
                        clip.fLeft = 0;
                    }
                } else if (paragraphStyle.getTextDirection() == TextDirection::kRtl &&
                    !run->leftToRight())
                {
                    // Split
                    trailingSpaces = clip;
                    trailingSpaces.fLeft = - delta;
                    trailingSpaces.fRight = 0;
                    clip.fLeft += delta;
                } else if (paragraphStyle.getTextDirection() == TextDirection::kLtr &&
                    run->leftToRight())
                {
                    // Split
                    trailingSpaces = clip;
                    trailingSpaces.fLeft = this->width();
                    trailingSpaces.fRight = trailingSpaces.fLeft + delta;
                    clip.fRight -= delta;
                }
            }

            clip.offset(this->offset());
            if (trailingSpaces.width() > 0) {
                trailingSpaces.offset(this->offset());
            }

            // Check if we can merge two boxes instead of adding a new one
            auto merge = [&lastRun, &context, &boxes](SkRect clip) {
                bool mergedBoxes = false;
                if (!boxes.empty() &&
                    lastRun != nullptr &&
                    lastRun->placeholderStyle() == nullptr &&
                    context.run->placeholderStyle() == nullptr &&
                    nearlyEqual(lastRun->heightMultiplier(),
                                context.run->heightMultiplier()) &&
                    lastRun->font() == context.run->font())
                {
                    auto& lastBox = boxes.back();
                    if (nearlyEqual(lastBox.rect.fTop, clip.fTop) &&
                        nearlyEqual(lastBox.rect.fBottom, clip.fBottom) &&
                            (nearlyEqual(lastBox.rect.fLeft, clip.fRight) ||
                             nearlyEqual(lastBox.rect.fRight, clip.fLeft)))
                    {
                        lastBox.rect.fLeft = std::min(lastBox.rect.fLeft, clip.fLeft);
                        lastBox.rect.fRight = std::max(lastBox.rect.fRight, clip.fRight);
                        mergedBoxes = true;
                    }
                }
                lastRun = context.run;
                return mergedBoxes;
            };

            if (!merge(clip)) {
                boxes.emplace_back(clip, context.run->getTextDirection());
            }
            if (!nearlyZero(trailingSpaces.width()) && !merge(trailingSpaces)) {
                boxes.emplace_back(trailingSpaces, paragraphStyle.getTextDirection());
            }

            if (rectWidthStyle == RectWidthStyle::kMax && !isLastLine()) {
                // Align the very left/right box horizontally
                auto lineStart = this->offset().fX;
                auto lineEnd = this->offset().fX + this->width();
                auto left = boxes[startBox];
                auto right = boxes.back();
                if (left.rect.fLeft > lineStart && left.direction == TextDirection::kRtl) {
                    left.rect.fRight = left.rect.fLeft;
                    left.rect.fLeft = 0;
                    boxes.insert(boxes.begin() + startBox + 1, left);
                }
                if (right.direction == TextDirection::kLtr &&
                    right.rect.fRight >= lineEnd &&
                    right.rect.fRight < fOwner->widthWithTrailingSpaces()) {
                    right.rect.fLeft = right.rect.fRight;
                    right.rect.fRight = fOwner->widthWithTrailingSpaces();
                    boxes.emplace_back(right);
                }
            }

            return true;
        });
        return true;
    });
    for (auto& r : boxes) {
        r.rect.fLeft = littleRound(r.rect.fLeft);
        r.rect.fRight = littleRound(r.rect.fRight);
        r.rect.fTop = littleRound(r.rect.fTop);
        r.rect.fBottom = littleRound(r.rect.fBottom);
    }
}

PositionWithAffinity TextLine::getGlyphPositionAtCoordinate(SkScalar dx) {

    if (SkScalarNearlyZero(this->width()) && SkScalarNearlyZero(this->spacesWidth())) {
        // TODO: this is one of the flutter changes that have to go away eventually
        //  Empty line is a special case in txtlib (but only when there are no spaces, too)
        auto utf16Index = fOwner->getUTF16Index(this->fTextExcludingSpaces.end);
        return { SkToS32(utf16Index) , kDownstream };
    }

    PositionWithAffinity result(0, Affinity::kDownstream);
    this->iterateThroughVisualRuns(true,
        [this, dx, &result]
        (const Run* run, SkScalar runOffsetInLine, TextRange textRange, SkScalar* runWidthInLine) {
            bool keepLooking = true;
            *runWidthInLine = this->iterateThroughSingleRunByStyles(
            run, runOffsetInLine, textRange, StyleType::kNone,
            [this, run, dx, &result, &keepLooking]
            (TextRange textRange, const TextStyle& style, const TextLine::ClipContext& context0) {

                SkScalar offsetX = this->offset().fX;
                ClipContext context = context0;

                // Correct the clip size because libtxt counts trailing spaces
                if (run->leftToRight()) {
                    context.clip.fRight += context.fExcludedTrailingSpaces; // extending clip to the right
                } else {
                    // Clip starts from 0; we cannot extend it to the left from that
                }
                // This patch will help us to avoid a floating point error
                if (SkScalarNearlyEqual(context.clip.fRight, dx - offsetX, 0.01f)) {
                    context.clip.fRight = dx - offsetX;
                }

                if (dx < context.clip.fLeft + offsetX) {
                    // All the other runs are placed right of this one
                    auto utf16Index = fOwner->getUTF16Index(context.run->globalClusterIndex(context.pos));
                    if (run->leftToRight()) {
                        result = { SkToS32(utf16Index), kDownstream };
                    } else {
                        result = { SkToS32(utf16Index + 1), kUpstream };
                    }
                    // For RTL we go another way
                    return keepLooking = !run->leftToRight();
                }

                if (dx >= context.clip.fRight + offsetX) {
                    // We have to keep looking ; just in case keep the last one as the closest
                    auto utf16Index = fOwner->getUTF16Index(context.run->globalClusterIndex(context.pos + context.size));
                    if (run->leftToRight()) {
                        result = {SkToS32(utf16Index), kUpstream};
                    } else {
                        result = {SkToS32(utf16Index), kDownstream};
                    }
                    // For RTL we go another way
                    return keepLooking = run->leftToRight();
                }

                // So we found the run that contains our coordinates
                // Find the glyph position in the run that is the closest left of our point
                // TODO: binary search
                size_t found = context.pos;
                for (size_t index = context.pos; index < context.pos + context.size; ++index) {
                    // TODO: this rounding is done to match Flutter tests. Must be removed..
                    auto end = littleRound(context.run->positionX(index) + context.fTextShift + offsetX);
                    if (end > dx) {
                        break;
                    } else if (end == dx && !context.run->leftToRight()) {
                        // When we move RTL variable end points to the beginning of the code point which is included
                        break;
                    }
                    found = index;
                }

                SkScalar glyphemePosLeft = context.run->positionX(found) + context.fTextShift + offsetX;
                SkScalar glyphemePosWidth = context.run->positionX(found + 1) - context.run->positionX(found);

                // Find the grapheme range that contains the point
                auto clusterIndex8 = context.run->globalClusterIndex(found);
                auto clusterEnd8 = context.run->globalClusterIndex(found + 1);
                TextIndex graphemeUtf8Start =
                    fOwner->findPreviousGraphemeBoundary(clusterIndex8);
                TextIndex graphemeUtf8Width =
                    fOwner->findNextGraphemeBoundary(clusterEnd8) - graphemeUtf8Start;
                size_t utf16Index = fOwner->getUTF16Index(clusterIndex8);

                SkScalar center = glyphemePosLeft + glyphemePosWidth / 2;
                bool insideGlypheme = false;
                if (graphemeUtf8Width > 1) {
                    // TODO: the average width of a code unit (especially UTF-8) is meaningless.
                    // Probably want the average width of a grapheme or codepoint?
                    SkScalar averageUtf8Width = glyphemePosWidth / graphemeUtf8Width;
                    SkScalar delta = dx - glyphemePosLeft;
                    int insideUtf8Offset = SkScalarNearlyZero(averageUtf8Width)
                                         ? 0
                                         : SkScalarFloorToInt(delta / averageUtf8Width);
                    insideGlypheme = averageUtf8Width < delta && delta < glyphemePosWidth - averageUtf8Width;
                    center = glyphemePosLeft + averageUtf8Width * insideUtf8Offset + averageUtf8Width / 2;
                    // Keep UTF16 index as is
                }
                if ((dx < center) == context.run->leftToRight() || insideGlypheme) {
                    result = { SkToS32(utf16Index), kDownstream };
                } else {
                    result = { SkToS32(utf16Index + 1), kUpstream };
                }

                return keepLooking = false;

            });
          return keepLooking;
        }
    );
    return result;
}

void TextLine::getRectsForPlaceholders(std::vector<TextBox>& boxes) {
    this->iterateThroughVisualRuns(
        true,
        [&boxes, this](const Run* run, SkScalar runOffset, TextRange textRange,
                        SkScalar* width) {
            auto context = this->measureTextInsideOneRun(textRange, run, runOffset, 0, true, false);
            *width = context.clip.width();

            if (textRange.width() == 0) {
                return true;
            }
            if (!run->isPlaceholder()) {
                return true;
            }

            SkRect clip = context.clip;
            clip.offset(this->offset());

            clip.fLeft = littleRound(clip.fLeft);
            clip.fRight = littleRound(clip.fRight);
            clip.fTop = littleRound(clip.fTop);
            clip.fBottom = littleRound(clip.fBottom);
            boxes.emplace_back(clip, run->getTextDirection());
            return true;
        });
}
}  // namespace textlayout
}  // namespace skia