/*

 * Copyright 2020 Google LLC

 *

 * Use of this source code is governed by a BSD-style license that can be

 * found in the LICENSE file.

 */

#ifndef SkSLSampleUsage_DEFINED

#define SkSLSampleUsage_DEFINED

#include "include/core/SkTypes.h"

#include <string>

namespace SkSL {

/**

 * Represents all of the ways that a fragment processor is sampled by its parent.

 */

class SampleUsage {

public:

    enum class Kind {

        // Child is never sampled

        kNone,

        // Child is only sampled at the same coordinates as the parent

        kPassThrough,

        // Child is sampled with a matrix whose value is uniform

        kUniformMatrix,

        // Child is sampled with sk_FragCoord.xy

        kFragCoord,

        // Child is sampled using explicit coordinates

        kExplicit,

    };

    // Make a SampleUsage that corresponds to no sampling of the child at all

    SampleUsage() = default;

    SampleUsage(Kind kind, bool hasPerspective) : fKind(kind), fHasPerspective(hasPerspective) {

        if (kind != Kind::kUniformMatrix) {

            SkASSERT(!fHasPerspective);

        }

    }

    // Child is sampled with a matrix whose value is uniform. The name is fixed.

    static SampleUsage UniformMatrix(bool hasPerspective) {

        return SampleUsage(Kind::kUniformMatrix, hasPerspective);

    }

    static SampleUsage Explicit() {

        return SampleUsage(Kind::kExplicit, false);

    }

    static SampleUsage PassThrough() {

        return SampleUsage(Kind::kPassThrough, false);

    }

    static SampleUsage FragCoord() { return SampleUsage(Kind::kFragCoord, false); }

    bool operator==(const SampleUsage& that) const {

        return fKind == that.fKind && fHasPerspective == that.fHasPerspective;

    }

    bool operator!=(const SampleUsage& that) const { return !(*this == that); }

    // Arbitrary name used by all uniform sampling matrices

    static const char* MatrixUniformName() { return "matrix"; }

    SampleUsage merge(const SampleUsage& other);

    Kind kind() const { return fKind; }

    bool hasPerspective() const { return fHasPerspective; }

    bool isSampled()       const { return fKind != Kind::kNone; }

    bool isPassThrough()   const { return fKind == Kind::kPassThrough; }

    bool isExplicit()      const { return fKind == Kind::kExplicit; }

    bool isUniformMatrix() const { return fKind == Kind::kUniformMatrix; }

    bool isFragCoord()     const { return fKind == Kind::kFragCoord; }

    std::string constructor() const;

private:

    Kind fKind = Kind::kNone;

    bool fHasPerspective = false;  // Only valid if fKind is kUniformMatrix

};

}  // namespace SkSL

#endif