// Copyright 2024 The Dawn & Tint Authors
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#include "src/tint/lang/glsl/writer/raise/builtin_polyfill.h"

#include <string>
#include <tuple>

#include "src/tint/lang/core/fluent_types.h"  // IWYU pragma: export
#include "src/tint/lang/core/ir/builder.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/glsl/builtin_fn.h"
#include "src/tint/lang/glsl/ir/builtin_call.h"
#include "src/tint/lang/glsl/ir/ternary.h"

namespace tint::glsl::writer::raise {
namespace {

using namespace tint::core::fluent_types;     // NOLINT
using namespace tint::core::number_suffixes;  // NOLINT

/// PIMPL state for the transform.
struct State {
    /// The IR module.
    core::ir::Module& ir;

    /// The IR builder.
    core::ir::Builder b{ir};

    /// The type manager.
    core::type::Manager& ty{ir.Types()};

    // Polyfill functions for bitcast expression, BitcastType indicates the source type and the
    // destination type.
    using BitcastType =
        tint::UnorderedKeyWrapper<std::tuple<const core::type::Type*, const core::type::Type*>>;
    Hashmap<BitcastType, core::ir::Function*, 4> bitcast_funcs_{};

    // The bitcast worklist is a member because some polyfills add bitcast calls. When they do, they
    // can add the bitcast to the worklist to be fixed up as needed.
    Vector<core::ir::Bitcast*, 4> bitcast_worklist{};

    /// Process the module.
    void Process() {
        Vector<core::ir::CoreBuiltinCall*, 4> call_worklist;
        for (auto* inst : ir.Instructions()) {
            if (auto* bitcast = inst->As<core::ir::Bitcast>()) {
                bitcast_worklist.Push(bitcast);
                continue;
            }

            if (auto* call = inst->As<core::ir::CoreBuiltinCall>()) {
                switch (call->Func()) {
                    case core::BuiltinFn::kAtomicCompareExchangeWeak:
                    case core::BuiltinFn::kAtomicSub:
                    case core::BuiltinFn::kAtomicLoad:
                    case core::BuiltinFn::kSelect:
                    case core::BuiltinFn::kStorageBarrier:
                    case core::BuiltinFn::kTextureBarrier:
                    case core::BuiltinFn::kWorkgroupBarrier:
                        call_worklist.Push(call);
                        break;
                    default:
                        break;
                }
                continue;
            }
        }

        // Replace the builtin calls that we found
        for (auto* call : call_worklist) {
            switch (call->Func()) {
                case core::BuiltinFn::kAtomicCompareExchangeWeak:
                    AtomicCompareExchangeWeak(call);
                    break;
                case core::BuiltinFn::kAtomicSub:
                    AtomicSub(call);
                    break;
                case core::BuiltinFn::kAtomicLoad:
                    AtomicLoad(call);
                    break;
                case core::BuiltinFn::kSelect:
                    Select(call);
                    break;
                case core::BuiltinFn::kStorageBarrier:
                case core::BuiltinFn::kTextureBarrier:
                case core::BuiltinFn::kWorkgroupBarrier:
                    Barrier(call);
                    break;
                default:
                    TINT_UNREACHABLE();
            }
        }

        // Replace the bitcasts that we found. These are done after the other builtins as some of
        // them also create bitcasts which will need to be updated.
        for (auto* bitcast : bitcast_worklist) {
            auto* src_type = bitcast->Val()->Type();
            auto* dst_type = bitcast->Result(0)->Type();
            auto* dst_deepest = dst_type->DeepestElement();

            if (src_type == dst_type) {
                ReplaceBitcastWithValue(bitcast);
            } else if (src_type->DeepestElement()->Is<core::type::F16>()) {
                // TODO(dsinclair): Polyfill from f16
                TINT_UNREACHABLE();
            } else if (dst_deepest->Is<core::type::F16>()) {
                // TODO(dsinclair): Polyfill to f16
                TINT_UNREACHABLE();
            } else if (src_type->DeepestElement()->Is<core::type::F32>()) {
                ReplaceBitcastFromF32(bitcast);
            } else if (dst_type->DeepestElement()->Is<core::type::F32>()) {
                ReplaceBitcastToF32(bitcast);
            } else {
                ReplaceBitcast(bitcast);
            }
        }
    }

    void ReplaceBitcastWithValue(core::ir::Bitcast* bitcast) {
        bitcast->Result(0)->ReplaceAllUsesWith(bitcast->Val());
        bitcast->Destroy();
    }

    void ReplaceBitcastFromF32(core::ir::Bitcast* bitcast) {
        auto* dst_type = bitcast->Result(0)->Type();
        auto* dst_deepest = dst_type->DeepestElement();

        BuiltinFn fn = BuiltinFn::kNone;
        tint::Switch(
            dst_deepest,                                                        //
            [&](const core::type::I32*) { fn = BuiltinFn::kFloatBitsToInt; },   //
            [&](const core::type::U32*) { fn = BuiltinFn::kFloatBitsToUint; },  //
            TINT_ICE_ON_NO_MATCH);

        b.InsertBefore(bitcast, [&] {
            b.CallWithResult<glsl::ir::BuiltinCall>(bitcast->DetachResult(), fn, bitcast->Val());
        });
        bitcast->Destroy();
    }

    void ReplaceBitcastToF32(core::ir::Bitcast* bitcast) {
        auto* src_type = bitcast->Val()->Type();
        auto* src_deepest = src_type->DeepestElement();

        BuiltinFn fn = BuiltinFn::kNone;
        tint::Switch(
            src_deepest,                                                        //
            [&](const core::type::I32*) { fn = BuiltinFn::kIntBitsToFloat; },   //
            [&](const core::type::U32*) { fn = BuiltinFn::kUintBitsToFloat; },  //
            TINT_ICE_ON_NO_MATCH);

        b.InsertBefore(bitcast, [&] {
            b.CallWithResult<glsl::ir::BuiltinCall>(bitcast->DetachResult(), fn, bitcast->Val());
        });
        bitcast->Destroy();
    }

    void ReplaceBitcast(core::ir::Bitcast* bitcast) {
        b.InsertBefore(bitcast,
                       [&] { b.ConvertWithResult(bitcast->DetachResult(), bitcast->Val()); });
        bitcast->Destroy();
    }

    void AtomicCompareExchangeWeak(core::ir::BuiltinCall* call) {
        auto args = call->Args();
        auto* type = args[1]->Type();

        auto* dest = args[0];
        auto* compare_value = args[1];
        auto* value = args[2];

        auto* result_type = call->Result(0)->Type();

        b.InsertBefore(call, [&] {
            auto* bitcast_cmp_value = b.Bitcast(type, compare_value);
            auto* bitcast_value = b.Bitcast(type, value);

            bitcast_worklist.Push(bitcast_cmp_value);
            bitcast_worklist.Push(bitcast_value);

            auto* swap = b.Call<glsl::ir::BuiltinCall>(
                type, glsl::BuiltinFn::kAtomicCompSwap,
                Vector<core::ir::Value*, 3>{dest, bitcast_cmp_value->Result(0),
                                            bitcast_value->Result(0)});

            auto* exchanged = b.Equal(ty.bool_(), swap, compare_value);

            auto* result = b.Construct(result_type, swap, exchanged)->Result(0);
            call->Result(0)->ReplaceAllUsesWith(result);
        });
        call->Destroy();
    }

    void AtomicSub(core::ir::BuiltinCall* call) {
        b.InsertBefore(call, [&] {
            auto args = call->Args();

            if (args[1]->Type()->Is<core::type::I32>()) {
                b.CallWithResult(call->DetachResult(), core::BuiltinFn::kAtomicAdd, args[0],
                                 b.Negation(args[1]->Type(), args[1]));
            } else {
                // Negating a u32 isn't possible in the IR, so pass a fake GLSL function and handle
                // in the printer.
                b.CallWithResult<glsl::ir::BuiltinCall>(
                    call->DetachResult(), glsl::BuiltinFn::kAtomicSub,
                    Vector<core::ir::Value*, 2>{args[0], args[1]});
            }
        });
        call->Destroy();
    }

    void AtomicLoad(core::ir::CoreBuiltinCall* call) {
        // GLSL does not have an atomicLoad, so we emulate it with atomicOr using 0 as the OR value
        b.InsertBefore(call, [&] {
            auto args = call->Args();
            b.CallWithResult(
                call->DetachResult(), core::BuiltinFn::kAtomicOr, args[0],
                b.Zero(args[0]->Type()->UnwrapPtr()->As<core::type::Atomic>()->Type()));
        });
        call->Destroy();
    }

    void Barrier(core::ir::CoreBuiltinCall* call) {
        b.InsertBefore(call, [&] {
            b.Call<glsl::ir::BuiltinCall>(ty.void_(), glsl::BuiltinFn::kBarrier);

            switch (call->Func()) {
                case core::BuiltinFn::kStorageBarrier:
                    b.Call<glsl::ir::BuiltinCall>(ty.void_(),
                                                  glsl::BuiltinFn::kMemoryBarrierBuffer);
                    break;
                case core::BuiltinFn::kTextureBarrier:
                    b.Call<glsl::ir::BuiltinCall>(ty.void_(), glsl::BuiltinFn::kMemoryBarrierImage);
                    break;
                default:
                    break;
            }
        });

        call->Destroy();
    }

    void Select(core::ir::CoreBuiltinCall* call) {
        Vector<core::ir::Value*, 4> args = call->Args();

        // GLSL does not support ternary expressions with a bool vector conditional,
        // so polyfill by manually creating a vector with each of the
        // individual scalar ternaries.
        if (auto* vec = call->Result(0)->Type()->As<core::type::Vector>()) {
            Vector<core::ir::Value*, 4> construct_args;

            b.InsertBefore(call, [&] {
                auto* elm_ty = vec->Type();
                for (uint32_t i = 0; i < vec->Width(); i++) {
                    auto* false_ = b.Swizzle(elm_ty, args[0], {i})->Result(0);
                    auto* true_ = b.Swizzle(elm_ty, args[1], {i})->Result(0);
                    auto* cond = b.Swizzle(elm_ty, args[2], {i})->Result(0);

                    auto* ternary = b.ir.CreateInstruction<glsl::ir::Ternary>(
                        b.InstructionResult(elm_ty),
                        Vector<core::ir::Value*, 3>{false_, true_, cond});
                    ternary->InsertBefore(call);

                    construct_args.Push(ternary->Result(0));
                }

                b.ConstructWithResult(call->DetachResult(), construct_args);
            });

        } else {
            auto* ternary = b.ir.CreateInstruction<glsl::ir::Ternary>(call->DetachResult(), args);
            ternary->InsertBefore(call);
        }
        call->Destroy();
    }
};

}  // namespace

Result<SuccessType> BuiltinPolyfill(core::ir::Module& ir) {
    auto result = ValidateAndDumpIfNeeded(ir, "BuiltinPolyfill transform");
    if (result != Success) {
        return result.Failure();
    }

    State{ir}.Process();

    return Success;
}

}  // namespace tint::glsl::writer::raise