/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrProgramStageFactory_DEFINED
#define GrProgramStageFactory_DEFINED

#include "GrTypes.h"
#include "SkTemplates.h"
#include "GrNoncopyable.h"

/** Given a GrCustomStage of a particular type, creates the corresponding
    graphics-backend-specific GrProgramStage. Also tracks equivalence
    of shaders generated via a key.
 */

class GrCustomStage;
class GrGLProgramStage;

class GrProgramStageFactory : public GrNoncopyable {
public:
    typedef uint16_t StageKey;
    enum {
        kProgramStageKeyBits = 10,
    };

    virtual StageKey glStageKey(const GrCustomStage& stage) const = 0;
    virtual GrGLProgramStage* createGLInstance(
        const GrCustomStage& stage) const = 0;

    bool operator ==(const GrProgramStageFactory& b) const {
        return fStageClassID == b.fStageClassID;
    }
    bool operator !=(const GrProgramStageFactory& b) const {
        return !(*this == b);
    }

    virtual const char* name() const = 0;

protected:
    enum {
        kIllegalStageClassID = 0,
    };

    GrProgramStageFactory() {
        fStageClassID = kIllegalStageClassID;
    }

    static StageKey GenID() {
        // fCurrStageClassID has been initialized to kIllegalStageClassID. The
        // atomic inc returns the old value not the incremented value. So we add
        // 1 to the returned value.
        int32_t id = sk_atomic_inc(&fCurrStageClassID) + 1;
        GrAssert(id < (1 << (8 * sizeof(StageKey) - kProgramStageKeyBits)));
        return id;
    }

    StageKey fStageClassID;

private:
    static int32_t fCurrStageClassID;
};

template <typename StageClass>
class GrTProgramStageFactory : public GrProgramStageFactory {

public:
    typedef typename StageClass::GLProgramStage GLProgramStage; 

    /** Returns a human-readable name that is accessible via GrCustomStage or
        GrGLProgramStage and is consistent between the two of them.
     */
    virtual const char* name() const SK_OVERRIDE { return StageClass::Name(); }

    /** Returns a value that idenitifes the GLSL shader code generated by
        a GrCustomStage. This enables caching of generated shaders. Part of the
        id identifies the GrCustomShader subclass. The remainder is based
        on the aspects of the GrCustomStage object's configuration that affect
        GLSL code generation. */
    virtual StageKey glStageKey(const GrCustomStage& stage) const SK_OVERRIDE {
        GrAssert(kIllegalStageClassID != fStageClassID);
        StageKey stageID = GLProgramStage::GenKey(stage);
#if GR_DEBUG
        static const StageKey kIllegalIDMask =
            (uint16_t) (~((1U << kProgramStageKeyBits) - 1));
        GrAssert(!(kIllegalIDMask & stageID));
#endif
        return fStageClassID | stageID;
    }

    /** Returns a new instance of the appropriate *GL* implementation class
     for the given GrCustomStage; caller is responsible for deleting
     the object. */
    virtual GLProgramStage* createGLInstance(
                        const GrCustomStage& stage) const SK_OVERRIDE {
        return SkNEW_ARGS(GLProgramStage, (*this, stage));
    }

    /** This class is a singleton. This function returns the single instance.
     */
    static const GrProgramStageFactory& getInstance() {
        static SkAlignedSTStorage<1, GrTProgramStageFactory> gInstanceMem;
        static const GrTProgramStageFactory* gInstance;
        if (!gInstance) {
            gInstance = SkNEW_PLACEMENT(gInstanceMem.get(),
                                        GrTProgramStageFactory);
        }
        return *gInstance;
    }

protected:
    GrTProgramStageFactory() {
        fStageClassID = GenID() << kProgramStageKeyBits;
    }
};

#endif