// Copyright 2021 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "dawn/native/Limits.h"

#include <array>

#include "dawn/common/Assert.h"
#include "dawn/common/Math.h"

// clang-format off
// TODO(crbug.com/dawn/685):
// For now, only expose these tiers until metrics can determine better ones.
#define LIMITS_WORKGROUP_STORAGE_SIZE(X)                                  \
    X(Maximum, maxComputeWorkgroupStorageSize, 16384, 32768, 49152, 65536)

#define LIMITS_STORAGE_BUFFER_BINDING_SIZE(X)                                             \
    X(Maximum, maxStorageBufferBindingSize, 134217728, 1073741824, 2147483647, 4294967295)

// TODO(crbug.com/dawn/685):
// These limits don't have tiers yet. Define two tiers with the same values since the macros
// in this file expect more than one tier.
#define LIMITS_OTHER(X)                                                   \
    X(Maximum,                       maxTextureDimension1D,  8192,  8192) \
    X(Maximum,                       maxTextureDimension2D,  8192,  8192) \
    X(Maximum,                       maxTextureDimension3D,  2048,  2048) \
    X(Maximum,                       maxTextureArrayLayers,   256,   256) \
    X(Maximum,                               maxBindGroups,     4,     4) \
    X(Maximum,   maxDynamicUniformBuffersPerPipelineLayout,     8,     8) \
    X(Maximum,   maxDynamicStorageBuffersPerPipelineLayout,     4,     4) \
    X(Maximum,            maxSampledTexturesPerShaderStage,    16,    16) \
    X(Maximum,                   maxSamplersPerShaderStage,    16,    16) \
    X(Maximum,             maxStorageBuffersPerShaderStage,     8,     8) \
    X(Maximum,            maxStorageTexturesPerShaderStage,     4,     4) \
    X(Maximum,             maxUniformBuffersPerShaderStage,    12,    12) \
    X(Maximum,                 maxUniformBufferBindingSize, 65536, 65536) \
    X(Alignment,           minUniformBufferOffsetAlignment,   256,   256) \
    X(Alignment,           minStorageBufferOffsetAlignment,   256,   256) \
    X(Maximum,                            maxVertexBuffers,     8,     8) \
    X(Maximum,                         maxVertexAttributes,    16,    16) \
    X(Maximum,                  maxVertexBufferArrayStride,  2048,  2048) \
    X(Maximum,               maxInterStageShaderComponents,    60,    60) \
    X(Maximum,                         maxColorAttachments,     8,     8) \
    X(Maximum,           maxComputeInvocationsPerWorkgroup,   256,   256) \
    X(Maximum,                    maxComputeWorkgroupSizeX,   256,   256) \
    X(Maximum,                    maxComputeWorkgroupSizeY,   256,   256) \
    X(Maximum,                    maxComputeWorkgroupSizeZ,    64,    64) \
    X(Maximum,            maxComputeWorkgroupsPerDimension, 65535, 65535)
// clang-format on

#define LIMITS_EACH_GROUP(X)              \
    X(LIMITS_WORKGROUP_STORAGE_SIZE)      \
    X(LIMITS_STORAGE_BUFFER_BINDING_SIZE) \
    X(LIMITS_OTHER)

#define LIMITS(X)                         \
    LIMITS_WORKGROUP_STORAGE_SIZE(X)      \
    LIMITS_STORAGE_BUFFER_BINDING_SIZE(X) \
    LIMITS_OTHER(X)

namespace dawn::native {
namespace {
template <uint32_t A, uint32_t B>
constexpr void StaticAssertSame() {
    static_assert(A == B, "Mismatching tier count in limit group.");
}

template <uint32_t I, uint32_t... Is>
constexpr uint32_t ReduceSameValue(std::integer_sequence<uint32_t, I, Is...>) {
    int unused[] = {0, (StaticAssertSame<I, Is>(), 0)...};
    DAWN_UNUSED(unused);
    return I;
}

enum class LimitClass {
    Alignment,
    Maximum,
};

template <LimitClass C>
struct CheckLimit;

template <>
struct CheckLimit<LimitClass::Alignment> {
    template <typename T>
    static bool IsBetter(T lhs, T rhs) {
        return lhs < rhs;
    }

    template <typename T>
    static MaybeError Validate(T supported, T required) {
        DAWN_INVALID_IF(IsBetter(required, supported),
                        "Required limit (%u) is lower than the supported limit (%u).", required,
                        supported);
        DAWN_INVALID_IF(!IsPowerOfTwo(required), "Required limit (%u) is not a power of two.",
                        required);
        return {};
    }
};

template <>
struct CheckLimit<LimitClass::Maximum> {
    template <typename T>
    static bool IsBetter(T lhs, T rhs) {
        return lhs > rhs;
    }

    template <typename T>
    static MaybeError Validate(T supported, T required) {
        DAWN_INVALID_IF(IsBetter(required, supported),
                        "Required limit (%u) is greater than the supported limit (%u).", required,
                        supported);
        return {};
    }
};

template <typename T>
bool IsLimitUndefined(T value) {
    static_assert(sizeof(T) != sizeof(T), "IsLimitUndefined not implemented for this type");
    return false;
}

template <>
bool IsLimitUndefined<uint32_t>(uint32_t value) {
    return value == wgpu::kLimitU32Undefined;
}

template <>
bool IsLimitUndefined<uint64_t>(uint64_t value) {
    return value == wgpu::kLimitU64Undefined;
}

}  // namespace

void GetDefaultLimits(Limits* limits) {
    ASSERT(limits != nullptr);
#define X(Better, limitName, base, ...) limits->limitName = base;
    LIMITS(X)
#undef X
}

Limits ReifyDefaultLimits(const Limits& limits) {
    Limits out;
#define X(Class, limitName, base, ...)                                                         \
    if (IsLimitUndefined(limits.limitName) ||                                                  \
        CheckLimit<LimitClass::Class>::IsBetter(static_cast<decltype(limits.limitName)>(base), \
                                                limits.limitName)) {                           \
        /* If the limit is undefined or the default is better, use the default */              \
        out.limitName = base;                                                                  \
    } else {                                                                                   \
        out.limitName = limits.limitName;                                                      \
    }
    LIMITS(X)
#undef X
    return out;
}

MaybeError ValidateLimits(const Limits& supportedLimits, const Limits& requiredLimits) {
#define X(Class, limitName, ...)                                                            \
    if (!IsLimitUndefined(requiredLimits.limitName)) {                                      \
        DAWN_TRY_CONTEXT(CheckLimit<LimitClass::Class>::Validate(supportedLimits.limitName, \
                                                                 requiredLimits.limitName), \
                         "validating " #limitName);                                         \
    }
    LIMITS(X)
#undef X
    return {};
}

Limits ApplyLimitTiers(Limits limits) {
#define X_TIER_COUNT(Better, limitName, ...) , std::integer_sequence<uint64_t, __VA_ARGS__>{}.size()
#define GET_TIER_COUNT(LIMIT_GROUP) \
    ReduceSameValue(std::integer_sequence<uint32_t LIMIT_GROUP(X_TIER_COUNT)>{})

#define X_EACH_GROUP(LIMIT_GROUP)                                    \
    {                                                                \
        constexpr uint32_t kTierCount = GET_TIER_COUNT(LIMIT_GROUP); \
        for (uint32_t i = kTierCount; i != 0; --i) {                 \
            LIMIT_GROUP(X_CHECK_BETTER_AND_CLAMP)                    \
            /* Limits fit in tier and have been clamped. Break. */   \
            break;                                                   \
        }                                                            \
    }

#define X_CHECK_BETTER_AND_CLAMP(Class, limitName, ...)                                   \
    {                                                                                     \
        constexpr std::array<decltype(Limits::limitName), kTierCount> tiers{__VA_ARGS__}; \
        decltype(Limits::limitName) tierValue = tiers[i - 1];                             \
        if (CheckLimit<LimitClass::Class>::IsBetter(tierValue, limits.limitName)) {       \
            /* The tier is better. Go to the next tier. */                                \
            continue;                                                                     \
        } else if (tierValue != limits.limitName) {                                       \
            /* Better than the tier. Degrade |limits| to the tier. */                     \
            limits.limitName = tiers[i - 1];                                              \
        }                                                                                 \
    }

    LIMITS_EACH_GROUP(X_EACH_GROUP)
#undef X_CHECK_BETTER
#undef X_EACH_GROUP
#undef GET_TIER_COUNT
#undef X_TIER_COUNT
    return limits;
}

}  // namespace dawn::native