/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkGlyphCache_DEFINED
#define SkGlyphCache_DEFINED

#include "SkBitmap.h"
#include "SkChecksum.h"
#include "SkChunkAlloc.h"
#include "SkDescriptor.h"
#include "SkGlyph.h"
#include "SkScalerContext.h"
#include "SkTemplates.h"
#include "SkTDArray.h"

struct SkDeviceProperties;
class SkPaint;

class SkGlyphCache_Globals;

// Enable this locally to add stats for hash-table hit rates. It also extends the dump()
// output to show those stats.
//#define SK_GLYPHCACHE_TRACK_HASH_STATS

/** \class SkGlyphCache

    This class represents a strike: a specific combination of typeface, size,
    matrix, etc., and holds the glyphs for that strike. Calling any of the
    getUnichar.../getGlyphID... methods will return the requested glyph,
    either instantly if it is already cached, or by first generating it and then
    adding it to the strike.

    The strikes are held in a global list, available to all threads. To interact
    with one, call either VisitCache() or DetachCache().
*/
class SkGlyphCache {
public:
    /** Returns a glyph with valid fAdvance and fDevKern fields.
        The remaining fields may be valid, but that is not guaranteed. If you
        require those, call getUnicharMetrics or getGlyphIDMetrics instead.
    */
    const SkGlyph& getUnicharAdvance(SkUnichar);
    const SkGlyph& getGlyphIDAdvance(uint16_t);

    /** Returns a glyph with all fields valid except fImage and fPath, which
        may be null. If they are null, call findImage or findPath for those.
        If they are not null, then they are valid.

        This call is potentially slower than the matching ...Advance call. If
        you only need the fAdvance/fDevKern fields, call those instead.
    */
    const SkGlyph& getUnicharMetrics(SkUnichar);
    const SkGlyph& getGlyphIDMetrics(uint16_t);

    /** These are variants that take the device position of the glyph. Call
        these only if you are drawing in subpixel mode. Passing 0, 0 is
        effectively the same as calling the variants w/o the extra params, tho
        a tiny bit slower.
    */
    const SkGlyph& getUnicharMetrics(SkUnichar, SkFixed x, SkFixed y);
    const SkGlyph& getGlyphIDMetrics(uint16_t, SkFixed x, SkFixed y);

    /** Return the glyphID for the specified Unichar. If the char has already
        been seen, use the existing cache entry. If not, ask the scalercontext
        to compute it for us.
    */
    uint16_t unicharToGlyph(SkUnichar);

    /** Map the glyph to its Unicode equivalent. Unmappable glyphs map to
        a character code of zero.
    */
    SkUnichar glyphToUnichar(uint16_t);

    /** Returns the number of glyphs for this strike.
    */
    unsigned getGlyphCount();

    /** Return the image associated with the glyph. If it has not been generated
        this will trigger that.
    */
    const void* findImage(const SkGlyph&);
    /** Return the Path associated with the glyph. If it has not been generated
        this will trigger that.
    */
    const SkPath* findPath(const SkGlyph&);

    /** Return the vertical metrics for this strike.
    */
    const SkPaint::FontMetrics& getFontMetrics() const {
        return fFontMetrics;
    }

    const SkDescriptor& getDescriptor() const { return *fDesc; }

    SkMask::Format getMaskFormat() const {
        return fScalerContext->getMaskFormat();
    }

    bool isSubpixel() const {
        return fScalerContext->isSubpixel();
    }

    void dump() const;

    /*  AuxProc/Data allow a client to associate data with this cache entry.
        Multiple clients can use this, as their data is keyed with a function
        pointer. In addition to serving as a key, the function pointer is called
        with the data when the glyphcache object is deleted, so the client can
        cleanup their data as well. NOTE: the auxProc must not try to access
        this glyphcache in any way, since it may be in the process of being
        deleted.
    */

    //! If the proc is found, return true and set *dataPtr to its data
    bool getAuxProcData(void (*auxProc)(void*), void** dataPtr) const;
    //! Add a proc/data pair to the glyphcache. proc should be non-null
    void setAuxProc(void (*auxProc)(void*), void* auxData);

    SkScalerContext* getScalerContext() const { return fScalerContext; }

    /** Find a matching cache entry, and call proc() with it. If none is found
        create a new one. If the proc() returns true, detach the cache and
        return it, otherwise leave it and return NULL.
    */
    static SkGlyphCache* VisitCache(SkTypeface*, const SkDescriptor* desc,
                                    bool (*proc)(const SkGlyphCache*, void*),
                                    void* context);

    /** Given a strike that was returned by either VisitCache() or DetachCache()
        add it back into the global cache list (after which the caller should
        not reference it anymore.
    */
    static void AttachCache(SkGlyphCache*);

    /** Detach a strike from the global cache matching the specified descriptor.
        Once detached, it can be queried/modified by the current thread, and
        when finished, be reattached to the global cache with AttachCache().
        While detached, if another request is made with the same descriptor,
        a different strike will be generated. This is fine. It does mean we
        can have more than 1 strike for the same descriptor, but that will
        eventually get purged, and the win is that different thread will never
        block each other while a strike is being used.
    */
    static SkGlyphCache* DetachCache(SkTypeface* typeface,
                                     const SkDescriptor* desc) {
        return VisitCache(typeface, desc, DetachProc, NULL);
    }

    static void Dump();

#ifdef SK_DEBUG
    void validate() const;
#else
    void validate() const {}
#endif

    class AutoValidate : SkNoncopyable {
    public:
        AutoValidate(const SkGlyphCache* cache) : fCache(cache) {
            if (fCache) {
                fCache->validate();
            }
        }
        ~AutoValidate() {
            if (fCache) {
                fCache->validate();
            }
        }
        void forget() {
            fCache = NULL;
        }
    private:
        const SkGlyphCache* fCache;
    };

private:
    // we take ownership of the scalercontext
    SkGlyphCache(SkTypeface*, const SkDescriptor*, SkScalerContext*);
    ~SkGlyphCache();

    enum MetricsType {
        kJustAdvance_MetricsType,
        kFull_MetricsType
    };

    // Return the SkGlyph* associated with MakeID. The id parameter is the combined glyph/x/y
    // id generated by MakeID. If it is just a glyph id then x and y are assuemd to be zero.
    SkGlyph* lookupByCombinedID(uint32_t id, MetricsType type);

    // Return a SkGlyph* associated with unicode id and position x and y.
    SkGlyph* lookupByChar(SkUnichar id, MetricsType type, SkFixed x = 0, SkFixed y = 0);

    // Return the index of id in the fGlyphArray. If it does
    // not exist, create a new one using MetricsType.
    uint16_t lookupMetrics(uint32_t id, MetricsType type);
    static bool DetachProc(const SkGlyphCache*, void*) { return true; }

    SkGlyphCache*        fNext, *fPrev;
    SkDescriptor*        fDesc;
    SkScalerContext*     fScalerContext;
    SkPaint::FontMetrics fFontMetrics;

    enum {
        kHashBits           = 8,
        kHashCount          = 1 << kHashBits,
        kHashMask           = kHashCount - 1
    };

    // A quick lookup to avoid the binary search looking for glyphs in fGlyphArray.
    uint16_t             fGlyphHash[kHashCount];
    // Contains the SkGlyphs that are used by fGlyphHash and fCharToGlyphHash. The zero element
    // is reserved for a sentinel SkGlyph that reduces the logic to check for collisions in the
    // hash arrays. The zero element has an fID of SkGlyph::kImpossibleID which never matches
    // any combined id generated for a char or a glyph.
    SkTDArray<SkGlyph>   fGlyphArray;
    SkChunkAlloc         fGlyphAlloc;

    struct CharGlyphRec {
        uint32_t    fID;    // unichar + subpixel
        uint16_t    fGlyphIndex;
    };

    // no reason to use the same kHashCount as fGlyphHash, but we do for now
    // Dynamically allocated when chars are encountered.
    SkAutoTArray<CharGlyphRec> fCharToGlyphHash;

    // The id arg is a combined id generated by MakeID.
    CharGlyphRec* getCharGlyphRec(uint32_t id);
    void adjustCaches(int insertion_index);

    static inline unsigned ID2HashIndex(uint32_t h) {
        return SkChecksum::CheapMix(h) & kHashMask;
    }

    // used to track (approx) how much ram is tied-up in this cache
    size_t  fMemoryUsed;

#ifdef SK_GLYPHCACHE_TRACK_HASH_STATS
    int fHashHitCount;
    int fHashMissCount;
#endif

    struct AuxProcRec {
        AuxProcRec* fNext;
        void (*fProc)(void*);
        void* fData;
    };
    AuxProcRec* fAuxProcList;
    void invokeAndRemoveAuxProcs();

    inline static SkGlyphCache* FindTail(SkGlyphCache* head);

    friend class SkGlyphCache_Globals;
};

class SkAutoGlyphCacheBase {
public:
    SkGlyphCache* getCache() const { return fCache; }

    void release() {
        if (fCache) {
            SkGlyphCache::AttachCache(fCache);
            fCache = NULL;
        }
    }

protected:
    // Hide the constructors so we can't create one of these directly.
    // Create SkAutoGlyphCache or SkAutoGlyphCacheNoCache instead.
    SkAutoGlyphCacheBase(SkGlyphCache* cache) : fCache(cache) {}
    SkAutoGlyphCacheBase(SkTypeface* typeface, const SkDescriptor* desc) {
        fCache = SkGlyphCache::DetachCache(typeface, desc);
    }
    SkAutoGlyphCacheBase(const SkPaint& /*paint*/,
                         const SkDeviceProperties* /*deviceProperties*/,
                         const SkMatrix* /*matrix*/) {
        fCache = NULL;
    }
    SkAutoGlyphCacheBase() {
        fCache = NULL;
    }
    ~SkAutoGlyphCacheBase() {
        if (fCache) {
            SkGlyphCache::AttachCache(fCache);
        }
    }

    SkGlyphCache*   fCache;

private:
    static bool DetachProc(const SkGlyphCache*, void*);
};

class SkAutoGlyphCache : public SkAutoGlyphCacheBase {
public:
    SkAutoGlyphCache(SkGlyphCache* cache) : SkAutoGlyphCacheBase(cache) {}
    SkAutoGlyphCache(SkTypeface* typeface, const SkDescriptor* desc) :
        SkAutoGlyphCacheBase(typeface, desc) {}
    SkAutoGlyphCache(const SkPaint& paint,
                     const SkDeviceProperties* deviceProperties,
                     const SkMatrix* matrix) {
        fCache = paint.detachCache(deviceProperties, matrix, false);
    }

private:
    SkAutoGlyphCache() : SkAutoGlyphCacheBase() {}
};
#define SkAutoGlyphCache(...) SK_REQUIRE_LOCAL_VAR(SkAutoGlyphCache)

class SkAutoGlyphCacheNoGamma : public SkAutoGlyphCacheBase {
public:
    SkAutoGlyphCacheNoGamma(SkGlyphCache* cache) : SkAutoGlyphCacheBase(cache) {}
    SkAutoGlyphCacheNoGamma(SkTypeface* typeface, const SkDescriptor* desc) :
        SkAutoGlyphCacheBase(typeface, desc) {}
    SkAutoGlyphCacheNoGamma(const SkPaint& paint,
                            const SkDeviceProperties* deviceProperties,
                            const SkMatrix* matrix) {
        fCache = paint.detachCache(deviceProperties, matrix, true);
    }

private:
    SkAutoGlyphCacheNoGamma() : SkAutoGlyphCacheBase() {}
};
#define SkAutoGlyphCacheNoGamma(...) SK_REQUIRE_LOCAL_VAR(SkAutoGlyphCacheNoGamma)

#endif