/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkPDFDocument.h"
#include "SkPDFDocumentPriv.h"

#include "SkMakeUnique.h"
#include "SkPDFCanon.h"
#include "SkPDFDevice.h"
#include "SkPDFTag.h"
#include "SkPDFUtils.h"
#include "SkStream.h"
#include "SkTo.h"

#include <utility>

// For use in SkCanvas::drawAnnotation
const char* SkPDFGetNodeIdKey() {
    static constexpr char key[] = "PDF_Node_Key";
    return key;
}

SkPDFObjectSerializer::SkPDFObjectSerializer() : fBaseOffset(0), fNextToBeSerialized(0) {}

SkPDFObjectSerializer::~SkPDFObjectSerializer() {
    for (const sk_sp<SkPDFObject>& obj: fObjNumMap.objects()) {
        obj->drop();
    }
}

SkPDFObjectSerializer::SkPDFObjectSerializer(SkPDFObjectSerializer&&) = default;

SkPDFObjectSerializer& SkPDFObjectSerializer::operator=(SkPDFObjectSerializer&&) = default;

void SkPDFObjectSerializer::addObjectRecursively(const sk_sp<SkPDFObject>& object) {
    fObjNumMap.addObjectRecursively(object.get());
}

#define SKPDF_MAGIC "\xD3\xEB\xE9\xE1"
#ifndef SK_BUILD_FOR_WIN
static_assert((SKPDF_MAGIC[0] & 0x7F) == "Skia"[0], "");
static_assert((SKPDF_MAGIC[1] & 0x7F) == "Skia"[1], "");
static_assert((SKPDF_MAGIC[2] & 0x7F) == "Skia"[2], "");
static_assert((SKPDF_MAGIC[3] & 0x7F) == "Skia"[3], "");
#endif
void SkPDFObjectSerializer::serializeHeader(SkWStream* wStream,
                                            const SkPDF::Metadata& md) {
    fBaseOffset = wStream->bytesWritten();
    static const char kHeader[] = "%PDF-1.4\n%" SKPDF_MAGIC "\n";
    wStream->writeText(kHeader);
    // The PDF spec recommends including a comment with four
    // bytes, all with their high bits set.  "\xD3\xEB\xE9\xE1" is
    // "Skia" with the high bits set.
    fInfoDict = SkPDFMetadata::MakeDocumentInformationDict(md);
    this->addObjectRecursively(fInfoDict);
    this->serializeObjects(wStream);
}
#undef SKPDF_MAGIC

// Serialize all objects in the fObjNumMap that have not yet been serialized;
void SkPDFObjectSerializer::serializeObjects(SkWStream* wStream) {
    const std::vector<sk_sp<SkPDFObject>>& objects = fObjNumMap.objects();
    while (fNextToBeSerialized < objects.size()) {
        SkPDFObject* object = objects[fNextToBeSerialized].get();
        // Maximum number of indirect objects is 2^23-1.
        int32_t index = SkToS32(fNextToBeSerialized + 1);  // Skip object 0.
        // "The first entry in the [XREF] table (object number 0) is
        // always free and has a generation number of 65,535; it is
        // the head of the linked list of free objects."
        SkASSERT(fOffsets.size() == fNextToBeSerialized);
        fOffsets.push_back(this->offset(wStream));
        wStream->writeDecAsText(index);
        wStream->writeText(" 0 obj\n");  // Generation number is always 0.
        object->emitObject(wStream, fObjNumMap);
        wStream->writeText("\nendobj\n");
        object->drop();
        ++fNextToBeSerialized;
    }
}

// Xref table and footer
void SkPDFObjectSerializer::serializeFooter(SkWStream* wStream,
                                            const sk_sp<SkPDFObject> docCatalog,
                                            sk_sp<SkPDFObject> id) {
    this->serializeObjects(wStream);
    int32_t xRefFileOffset = this->offset(wStream);
    // Include the special zeroth object in the count.
    int32_t objCount = SkToS32(fOffsets.size() + 1);
    wStream->writeText("xref\n0 ");
    wStream->writeDecAsText(objCount);
    wStream->writeText("\n0000000000 65535 f \n");
    for (size_t i = 0; i < fOffsets.size(); i++) {
        wStream->writeBigDecAsText(fOffsets[i], 10);
        wStream->writeText(" 00000 n \n");
    }
    SkPDFDict trailerDict;
    trailerDict.insertInt("Size", objCount);
    SkASSERT(docCatalog);
    trailerDict.insertObjRef("Root", docCatalog);
    SkASSERT(fInfoDict);
    trailerDict.insertObjRef("Info", std::move(fInfoDict));
    if (id) {
        trailerDict.insertObject("ID", std::move(id));
    }
    wStream->writeText("trailer\n");
    trailerDict.emitObject(wStream, fObjNumMap);
    wStream->writeText("\nstartxref\n");
    wStream->writeBigDecAsText(xRefFileOffset);
    wStream->writeText("\n%%EOF");
}

int32_t SkPDFObjectSerializer::offset(SkWStream* wStream) {
    size_t offset = wStream->bytesWritten();
    SkASSERT(offset > fBaseOffset);
    return SkToS32(offset - fBaseOffset);
}

static sk_sp<SkPDFDict> generate_page_tree(const std::vector<sk_sp<SkPDFDict>>& pages) {
    // PDF wants a tree describing all the pages in the document.  We arbitrary
    // choose 8 (kNodeSize) as the number of allowed children.  The internal
    // nodes have type "Pages" with an array of children, a parent pointer, and
    // the number of leaves below the node as "Count."  The leaves are passed
    // into the method, have type "Page" and need a parent pointer. This method
    // builds the tree bottom up, skipping internal nodes that would have only
    // one child.
    SkASSERT(pages.size() > 0);
    struct PageTreeNode {
        sk_sp<SkPDFDict> fNode;
        int fPageObjectDescendantCount;

        static void Layer(std::vector<PageTreeNode>* vec) {
            std::vector<PageTreeNode> result;
            static constexpr size_t kMaxNodeSize = 8;
            const size_t n = vec->size();
            SkASSERT(n >= 1);
            const size_t result_len = (n - 1) / kMaxNodeSize + 1;
            SkASSERT(result_len >= 1);
            SkASSERT(n == 1 || result_len < n);
            result.reserve(result_len);
            size_t index = 0;
            for (size_t i = 0; i < result_len; ++i) {
                if (n != 1 && index + 1 == n) {  // No need to create a new node.
                    result.push_back(std::move((*vec)[index++]));
                    continue;
                }
                auto next = sk_make_sp<SkPDFDict>("Pages");
                auto kids_list = sk_make_sp<SkPDFArray>();
                int descendantCount = 0;
                for (size_t j = 0; j < kMaxNodeSize && index < n; ++j) {
                    PageTreeNode& node = (*vec)[index++];
                    node.fNode->insertObjRef("Parent", next);
                    kids_list->appendObjRef(std::move(node.fNode));
                    descendantCount += node.fPageObjectDescendantCount;
                }
                next->insertInt("Count", descendantCount);
                next->insertObject("Kids", std::move(kids_list));
                result.push_back(PageTreeNode{std::move(next), descendantCount});
            }
            *vec = result;
        }
    };
    std::vector<PageTreeNode> currentLayer;
    currentLayer.reserve(pages.size());
    for (const sk_sp<SkPDFDict>& page : pages) {
        currentLayer.push_back(PageTreeNode{page, 1});
    }
    PageTreeNode::Layer(&currentLayer);
    while (currentLayer.size() > 1) {
        PageTreeNode::Layer(&currentLayer);
    }
    SkASSERT(currentLayer.size() == 1);
    return std::move(currentLayer[0].fNode);
}

template<typename T, typename... Args>
static void reset_object(T* dst, Args&&... args) {
    dst->~T();
    new (dst) T(std::forward<Args>(args)...);
}

////////////////////////////////////////////////////////////////////////////////

SkPDFDocument::SkPDFDocument(SkWStream* stream,
                             SkPDF::Metadata metadata)
    : SkDocument(stream)
    , fMetadata(std::move(metadata)) {
    constexpr float kDpiForRasterScaleOne = 72.0f;
    if (fMetadata.fRasterDPI != kDpiForRasterScaleOne) {
        fInverseRasterScale = kDpiForRasterScaleOne / fMetadata.fRasterDPI;
        fRasterScale        = fMetadata.fRasterDPI / kDpiForRasterScaleOne;
    }
    if (fMetadata.fStructureElementTreeRoot) {
        fTagRoot = recursiveBuildTagTree(*fMetadata.fStructureElementTreeRoot, nullptr);
    }
}

SkPDFDocument::~SkPDFDocument() {
    // subclasses of SkDocument must call close() in their destructors.
    this->close();
}

void SkPDFDocument::serialize(const sk_sp<SkPDFObject>& object) {
    fObjectSerializer.addObjectRecursively(object);
    fObjectSerializer.serializeObjects(this->getStream());
}

static SkSize operator*(SkISize u, SkScalar s) { return SkSize{u.width() * s, u.height() * s}; }
static SkSize operator*(SkSize u, SkScalar s) { return SkSize{u.width() * s, u.height() * s}; }

SkCanvas* SkPDFDocument::onBeginPage(SkScalar width, SkScalar height) {
    SkASSERT(fCanvas.imageInfo().dimensions().isZero());
    if (fPages.empty()) {
        // if this is the first page if the document.
        fObjectSerializer.serializeHeader(this->getStream(), fMetadata);
        fDests = sk_make_sp<SkPDFDict>();
        if (fMetadata.fPDFA) {
            SkPDFMetadata::UUID uuid = SkPDFMetadata::CreateUUID(fMetadata);
            // We use the same UUID for Document ID and Instance ID since this
            // is the first revision of this document (and Skia does not
            // support revising existing PDF documents).
            // If we are not in PDF/A mode, don't use a UUID since testing
            // works best with reproducible outputs.
            fID = SkPDFMetadata::MakePdfId(uuid, uuid);
            fXMP = SkPDFMetadata::MakeXMPObject(fMetadata, uuid, uuid);
            fObjectSerializer.addObjectRecursively(fXMP);
            fObjectSerializer.serializeObjects(this->getStream());
        }
    }
    // By scaling the page at the device level, we will create bitmap layer
    // devices at the rasterized scale, not the 72dpi scale.  Bitmap layer
    // devices are created when saveLayer is called with an ImageFilter;  see
    // SkPDFDevice::onCreateDevice().
    SkISize pageSize = (SkSize{width, height} * fRasterScale).toRound();
    SkMatrix initialTransform;
    // Skia uses the top left as the origin but PDF natively has the origin at the
    // bottom left. This matrix corrects for that, as well as the raster scale.
    initialTransform.setScaleTranslate(fInverseRasterScale, -fInverseRasterScale,
                                       0, fInverseRasterScale * pageSize.height());
    fPageDevice = sk_make_sp<SkPDFDevice>(pageSize, this, initialTransform);
    reset_object(&fCanvas, fPageDevice);
    fCanvas.scale(fRasterScale, fRasterScale);
    return &fCanvas;
}

void SkPDFDocument::onEndPage() {
    SkASSERT(!fCanvas.imageInfo().dimensions().isZero());
    fCanvas.flush();
    reset_object(&fCanvas);
    SkASSERT(fPageDevice);

    auto page = sk_make_sp<SkPDFDict>("Page");

    SkSize mediaSize = fPageDevice->imageInfo().dimensions() * fInverseRasterScale;
    auto contentObject = sk_make_sp<SkPDFStream>(fPageDevice->content());
    auto resourceDict = fPageDevice->makeResourceDict();
    auto annotations = fPageDevice->getAnnotations();
    fPageDevice->appendDestinations(fDests.get(), page.get());
    fPageDevice = nullptr;

    page->insertObject("Resources", resourceDict);
    page->insertObject("MediaBox", SkPDFUtils::RectToArray(SkRect::MakeSize(mediaSize)));

    if (annotations) {
        page->insertObject("Annots", std::move(annotations));
    }
    this->serialize(contentObject);
    page->insertObjRef("Contents", std::move(contentObject));
    // The StructParents unique identifier for each page is just its
    // 0-based page index.
    page->insertInt("StructParents", static_cast<int>(fPages.size()));
    fPages.emplace_back(std::move(page));
}

void SkPDFDocument::onAbort() {
    this->reset();
}

void SkPDFDocument::reset() {
    fObjectSerializer = SkPDFObjectSerializer();
    fCanon = SkPDFCanon();
    reset_object(&fCanvas);
    fPages = std::vector<sk_sp<SkPDFDict>>();
    fFonts.reset();
    fDests = nullptr;
    fPageDevice = nullptr;
    fID = nullptr;
    fXMP = nullptr;
    fMetadata = SkPDF::Metadata();
    fRasterScale = 1;
    fInverseRasterScale = 1;
}

static sk_sp<SkData> SkSrgbIcm() {
    // Source: http://www.argyllcms.com/icclibsrc.html
    static const char kProfile[] =
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        "\232h\232\325\233B\233\257\234\34\234\211\234\367\235d\235\322\236"
        "@\236\256\237\35\237\213\237\372\240i\240\330\241G\241\266\242&\242"
        "\226\243\6\243v\243\346\244V\244\307\2458\245\251\246\32\246\213\246"
        "\375\247n\247\340\250R\250\304\2517\251\251\252\34\252\217\253\2\253"
        "u\253\351\254\\\254\320\255D\255\270\256-\256\241\257\26\257\213\260"
        "\0\260u\260\352\261`\261\326\262K\262\302\2638\263\256\264%\264\234"
        "\265\23\265\212\266\1\266y\266\360\267h\267\340\270Y\270\321\271J\271"
        "\302\272;\272\265\273.\273\247\274!\274\233\275\25\275\217\276\n\276"
        "\204\276\377\277z\277\365\300p\300\354\301g\301\343\302_\302\333\303"
        "X\303\324\304Q\304\316\305K\305\310\306F\306\303\307A\307\277\310="
        "\310\274\311:\311\271\3128\312\267\3136\313\266\3145\314\265\3155\315"
        "\265\3166\316\266\3177\317\270\3209\320\272\321<\321\276\322?\322\301"
        "\323D\323\306\324I\324\313\325N\325\321\326U\326\330\327\\\327\340"
        "\330d\330\350\331l\331\361\332v\332\373\333\200\334\5\334\212\335\20"
        "\335\226\336\34\336\242\337)\337\257\3406\340\275\341D\341\314\342"
        "S\342\333\343c\343\353\344s\344\374\345\204\346\r\346\226\347\37\347"
        "\251\3502\350\274\351F\351\320\352[\352\345\353p\353\373\354\206\355"
        "\21\355\234\356(\356\264\357@\357\314\360X\360\345\361r\361\377\362"
        "\214\363\31\363\247\3644\364\302\365P\365\336\366m\366\373\367\212"
        "\370\31\370\250\3718\371\307\372W\372\347\373w\374\7\374\230\375)\375"
        "\272\376K\376\334\377m\377\377";
    const size_t kProfileLength = 3212;
    static_assert(kProfileLength == sizeof(kProfile) - 1, "");
    return SkData::MakeWithoutCopy(kProfile, kProfileLength);
}

static sk_sp<SkPDFStream> make_srgb_color_profile() {
    sk_sp<SkPDFStream> stream = sk_make_sp<SkPDFStream>(SkSrgbIcm());
    stream->dict()->insertInt("N", 3);
    stream->dict()->insertObject("Range", SkPDFMakeArray(0, 1, 0, 1, 0, 1));
    return stream;
}

static sk_sp<SkPDFArray> make_srgb_output_intents() {
    // sRGB is specified by HTML, CSS, and SVG.
    auto outputIntent = sk_make_sp<SkPDFDict>("OutputIntent");
    outputIntent->insertName("S", "GTS_PDFA1");
    outputIntent->insertString("RegistryName", "http://www.color.org");
    outputIntent->insertString("OutputConditionIdentifier",
                               "Custom");
    outputIntent->insertString("Info","sRGB IEC61966-2.1");
    outputIntent->insertObjRef("DestOutputProfile",
                               make_srgb_color_profile());
    auto intentArray = sk_make_sp<SkPDFArray>();
    intentArray->appendObject(std::move(outputIntent));
    return intentArray;
}

static sk_sp<SkPDFDict> make_top_resource_dict() {
    sk_sp<SkPDFDict> dict = sk_make_sp<SkPDFDict>();
    sk_sp<SkPDFArray> procSet = sk_make_sp<SkPDFArray>();
    static const char* kProcs[] = {"PDF", "Text", "ImageB", "ImageC", "ImageI"};
    procSet->reserve(SK_ARRAY_COUNT(kProcs));
    for (const char* proc : kProcs) {
        procSet->appendName(proc);
    }
    dict->insertObject("ProcSets", std::move(procSet));
    return dict;
}

sk_sp<SkPDFDict> SkPDFDocument::getPage(int pageIndex) const {
    SkASSERT(pageIndex >= 0 && pageIndex < static_cast<int>(fPages.size()));
    return fPages[pageIndex];
}

int SkPDFDocument::getMarkIdForNodeId(int nodeId) {
    sk_sp<SkPDFTag>* tagPtr = fNodeIdToTag.find(nodeId);
    if (tagPtr == nullptr) {
        return -1;
    }

    sk_sp<SkPDFTag> tag = *tagPtr;
    int pageIndex = static_cast<int>(fPages.size());
    while (fMarksPerPage.count() < pageIndex + 1) {
        fMarksPerPage.push_back();
    }
    int markId = fMarksPerPage[pageIndex].count();
    tag->addMarkedContent(pageIndex, markId);
    fMarksPerPage[pageIndex].push_back(std::move(tag));
    return markId;
}

sk_sp<SkPDFTag> SkPDFDocument::recursiveBuildTagTree(
        const SkPDF::StructureElementNode& node, sk_sp<SkPDFTag> parent) {
    sk_sp<SkPDFTag> tag = sk_make_sp<SkPDFTag>(node.fNodeId, node.fType, parent);
    fNodeIdToTag.set(tag->fNodeId, tag);
    tag->fChildren.reserve(node.fChildCount);
    for (size_t i = 0; i < node.fChildCount; i++) {
        tag->appendChild(recursiveBuildTagTree(node.fChildren[i], tag));
    }
    return tag;
}

void SkPDFDocument::onClose(SkWStream* stream) {
    SkASSERT(fCanvas.imageInfo().dimensions().isZero());
    if (fPages.empty()) {
        this->reset();
        return;
    }
    auto docCatalog = sk_make_sp<SkPDFDict>("Catalog");
    if (fMetadata.fPDFA) {
        SkASSERT(fXMP);
        docCatalog->insertObjRef("Metadata", fXMP);
        // Don't specify OutputIntents if we are not in PDF/A mode since
        // no one has ever asked for this feature.
        docCatalog->insertObject("OutputIntents", make_srgb_output_intents());
    }

    sk_sp<SkPDFDict> pageTree = generate_page_tree(fPages);
    pageTree->insertObject("Resources", make_top_resource_dict());
    docCatalog->insertObjRef("Pages", std::move(pageTree));
    if (fDests->size() > 0) {
        docCatalog->insertObjRef("Dests", std::move(fDests));
    }

    // Handle tagged PDFs.
    if (fTagRoot) {
        // In the document catalog, indicate that this PDF is tagged.
        auto markInfo = sk_make_sp<SkPDFDict>("MarkInfo");
        markInfo->insertBool("Marked", true);
        docCatalog->insertObject("MarkInfo", markInfo);

        // Prepare the tag tree, this automatically skips over any
        // tags that weren't referenced from any marked content.
        bool success = fTagRoot->prepareTagTreeToEmit(*this);
        if (!success) {
            SkDEBUGFAIL("PDF has tag tree but no marked content.");
        }

        // Build the StructTreeRoot.
        auto structTreeRoot = sk_make_sp<SkPDFDict>("StructTreeRoot");
        docCatalog->insertObjRef("StructTreeRoot", structTreeRoot);
        structTreeRoot->insertObjRef("K", fTagRoot);
        int pageCount = static_cast<int>(fPages.size());
        structTreeRoot->insertInt("ParentTreeNextKey", pageCount);

        // The parent of the tag root is the StructTreeRoot.
        fTagRoot->insertObjRef("P", structTreeRoot);

        // Build the parent tree, which is a mapping from the marked
        // content IDs on each page to their corressponding tags.
        auto parentTree = sk_make_sp<SkPDFDict>("ParentTree");
        structTreeRoot->insertObjRef("ParentTree", parentTree);
        structTreeRoot->insertInt("ParentTreeNextKey", pageCount);
        auto parentTreeNums = sk_make_sp<SkPDFArray>();
        parentTree->insertObject("Nums", parentTreeNums);
        for (int pageIndex = 0; pageIndex < pageCount; pageIndex++) {
            // Exit now if there are no more pages with marked content.
            if (fMarksPerPage.count() <= pageIndex) {
                break;
            }

            parentTreeNums->appendInt(pageIndex);
            auto markToTagArray = sk_make_sp<SkPDFArray>();
            parentTreeNums->appendObjRef(markToTagArray);

            for (int i = 0; i < fMarksPerPage[pageIndex].count(); i++) {
                markToTagArray->appendObjRef(fMarksPerPage[pageIndex][i]);
            }
        }
    }

    // Build font subsetting info before calling addObjectRecursively().
    SkPDFCanon* canon = &fCanon;
    fFonts.foreach([canon](SkPDFFont* p){ p->getFontSubset(canon); });
    fObjectSerializer.addObjectRecursively(docCatalog);
    fObjectSerializer.serializeObjects(this->getStream());
    fObjectSerializer.serializeFooter(this->getStream(), docCatalog, fID);
    this->reset();
}

///////////////////////////////////////////////////////////////////////////////

void SkPDF::SetNodeId(SkCanvas* canvas, int nodeID) {
    sk_sp<SkData> payload = SkData::MakeWithCopy(&nodeID, sizeof(nodeID));
    const char* key = SkPDFGetNodeIdKey();
    canvas->drawAnnotation({0, 0, 0, 0}, key, payload.get());
}

sk_sp<SkDocument> SkPDF::MakeDocument(SkWStream* stream, const SkPDF::Metadata& metadata) {
    SkPDF::Metadata meta = metadata;
    if (meta.fRasterDPI <= 0) {
        meta.fRasterDPI = 72.0f;
    }
    if (meta.fEncodingQuality < 0) {
        meta.fEncodingQuality = 0;
    }
    return stream ? sk_make_sp<SkPDFDocument>(stream, std::move(meta)) : nullptr;
}