// SPDX-License-Identifier: Apache-2.0

// SPDX-FileCopyrightText: Copyright The WasmEdge Authors

//===-- wasmedge/runtime/instance/function.h - Function Instance definition ==//

//

// Part of the WasmEdge Project.

//

//===----------------------------------------------------------------------===//

///

/// \file

/// This file contains the function instance definition in store manager.

///

//===----------------------------------------------------------------------===//

#pragma once

#include "ast/instruction.h"

#include "common/symbol.h"

#include "runtime/hostfunc.h"

#include "runtime/instance/composite.h"

#include <memory>

#include <numeric>

#include <string>

#include <vector>

namespace WasmEdge {

namespace Runtime {

namespace Instance {

class ModuleInstance;

class FunctionInstance : public CompositeBase {

public:

  using CompiledFunction = void;

  FunctionInstance() = delete;

  /// Move constructor.

  FunctionInstance(FunctionInstance &&Inst) noexcept

      : CompositeBase(Inst.ModInst, Inst.TypeIdx), FuncType(Inst.FuncType),

        Data(std::move(Inst.Data)) {

    assuming(ModInst);

  }

  /// Constructor for native function.

  FunctionInstance(const ModuleInstance *Mod, const uint32_t TIdx,

                   const AST::FunctionType &Type,

                   Span<const std::pair<uint32_t, ValType>> Locs,

                   AST::InstrView Expr) noexcept

      : CompositeBase(Mod, TIdx), FuncType(Type),

        Data(std::in_place_type_t<WasmFunction>(), Locs, Expr) {

    assuming(ModInst);

  }

  /// Constructor for compiled function.

  FunctionInstance(const ModuleInstance *Mod, const uint32_t TIdx,

                   const AST::FunctionType &Type,

                   Symbol<CompiledFunction> S) noexcept

      : CompositeBase(Mod, TIdx), FuncType(Type),

        Data(std::in_place_type_t<Symbol<CompiledFunction>>(), std::move(S)) {

    assuming(ModInst);

  }

  /// Constructors for host function.

  FunctionInstance(const ModuleInstance *Mod, const uint32_t TIdx,

                   std::unique_ptr<HostFunctionBase> &&Func) noexcept

      : CompositeBase(Mod, TIdx), FuncType(Func->getFuncType()),

        Data(std::in_place_type_t<std::unique_ptr<HostFunctionBase>>(),

             std::move(Func)) {

    assuming(ModInst);

  }

  FunctionInstance(std::unique_ptr<HostFunctionBase> &&Func) noexcept

      : CompositeBase(), FuncType(Func->getFuncType()),

        Data(std::in_place_type_t<std::unique_ptr<HostFunctionBase>>(),

             std::move(Func)) {}

  /// Check whether this is a native wasm function.

  bool isWasmFunction() const noexcept {

    return std::holds_alternative<WasmFunction>(Data);

  }

  /// Check whether this is a compiled function.

  bool isCompiledFunction() const noexcept {

    return std::holds_alternative<Symbol<CompiledFunction>>(Data);

  }

  /// Check whether this is a host function.

  bool isHostFunction() const noexcept {

    return std::holds_alternative<std::unique_ptr<HostFunctionBase>>(Data);

  }

  /// Getter for function type.

  const AST::FunctionType &getFuncType() const noexcept { return FuncType; }

  /// Getter for function local variables.

  Span<const std::pair<uint32_t, ValType>> getLocals() const noexcept {

    return std::get_if<WasmFunction>(&Data)->Locals;

  }

  /// Getter for function local number.

  uint32_t getLocalNum() const noexcept {

    return std::get_if<WasmFunction>(&Data)->LocalNum;

  }

  /// Getter for function body instrs.

  AST::InstrView getInstrs() const noexcept {

    if (std::holds_alternative<WasmFunction>(Data)) {

      return std::get<WasmFunction>(Data).Instrs;

    } else {

      return {};

    }

  }

  /// Getter for symbol.

  auto &getSymbol() const noexcept {

    return *std::get_if<Symbol<CompiledFunction>>(&Data);

  }

  /// Getter for host function.

  HostFunctionBase &getHostFunc() const noexcept {

    return *std::get_if<std::unique_ptr<HostFunctionBase>>(&Data)->get();

  }

  /// Upgrade from WasmFunction to CompiledFunction.

  /// Must be called under synchronization that

  /// prevents concurrent access to this function's body.

  bool unsafeUpgradeToCompiled(Symbol<CompiledFunction> Sym) noexcept {

    if (!isWasmFunction()) {

      return false;

    }

    Data = std::move(Sym);

    return true;

  }

private:

  struct WasmFunction {

    const std::vector<std::pair<uint32_t, ValType>> Locals;

    const uint32_t LocalNum;

    AST::InstrVec Instrs;

    WasmFunction(Span<const std::pair<uint32_t, ValType>> Locs,

                 AST::InstrView Expr) noexcept

        : Locals(Locs.begin(), Locs.end()),

          LocalNum(

              std::accumulate(Locals.begin(), Locals.end(), UINT32_C(0),

                              [](uint32_t N, const auto &Pair) -> uint32_t {

                                return N + Pair.first;

                              })) {

      // FIXME: Modify the capacity to prevent connecting 2 vectors.

      Instrs.reserve(Expr.size() + 1);

      Instrs.assign(Expr.begin(), Expr.end());

    }

  };

  /// \name Data of function instance.

  /// @{

  const AST::FunctionType &FuncType;

  std::variant<WasmFunction, Symbol<CompiledFunction>,

               std::unique_ptr<HostFunctionBase>>

      Data;

  /// @}

};

} // namespace Instance

} // namespace Runtime

} // namespace WasmEdge