// Copyright 2020 The Tint 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 "src/reader/spirv/function.h"

#include <utility>

#include "source/opt/basic_block.h"
#include "source/opt/function.h"
#include "source/opt/instruction.h"
#include "source/opt/module.h"
#include "src/ast/assignment_statement.h"
#include "src/ast/identifier_expression.h"
#include "src/ast/scalar_constructor_expression.h"
#include "src/ast/storage_class.h"
#include "src/ast/uint_literal.h"
#include "src/ast/variable.h"
#include "src/ast/variable_decl_statement.h"
#include "src/reader/spirv/fail_stream.h"
#include "src/reader/spirv/parser_impl.h"

namespace tint {
namespace reader {
namespace spirv {

FunctionEmitter::FunctionEmitter(ParserImpl* pi,
                                 const spvtools::opt::Function& function)
    : parser_impl_(*pi),
      ast_module_(pi->get_module()),
      ir_context_(*(pi->ir_context())),
      def_use_mgr_(ir_context_.get_def_use_mgr()),
      constant_mgr_(ir_context_.get_constant_mgr()),
      type_mgr_(ir_context_.get_type_mgr()),
      fail_stream_(pi->fail_stream()),
      namer_(pi->namer()),
      function_(function) {}

FunctionEmitter::~FunctionEmitter() = default;

bool FunctionEmitter::Emit() {
  if (failed()) {
    return false;
  }
  // We only care about functions with bodies.
  if (function_.cbegin() == function_.cend()) {
    return true;
  }

  if (!EmitFunctionDeclaration()) {
    return false;
  }

  if (!EmitBody()) {
    return false;
  }

  // Set the body of the AST function node.
  parser_impl_.get_module().functions().back()->set_body(std::move(ast_body_));

  return success();
}

bool FunctionEmitter::EmitFunctionDeclaration() {
  if (failed()) {
    return false;
  }

  const auto name = namer_.Name(function_.result_id());
  // Surprisingly, the "type id" on an OpFunction is the result type of the
  // function, not the type of the function.  This is the one exceptional case
  // in SPIR-V where the type ID is not the type of the result ID.
  auto* ret_ty = parser_impl_.ConvertType(function_.type_id());
  if (failed()) {
    return false;
  }
  if (ret_ty == nullptr) {
    return Fail()
           << "internal error: unregistered return type for function with ID "
           << function_.result_id();
  }

  ast::VariableList ast_params;
  function_.ForEachParam(
      [this, &ast_params](const spvtools::opt::Instruction* param) {
        auto* ast_type = parser_impl_.ConvertType(param->type_id());
        if (ast_type != nullptr) {
          ast_params.emplace_back(parser_impl_.MakeVariable(
              param->result_id(), ast::StorageClass::kNone, ast_type));
        } else {
          // We've already logged an error and emitted a diagnostic. Do nothing
          // here.
        }
      });
  if (failed()) {
    return false;
  }

  auto ast_fn =
      std::make_unique<ast::Function>(name, std::move(ast_params), ret_ty);
  ast_module_.AddFunction(std::move(ast_fn));

  return success();
}

ast::type::Type* FunctionEmitter::GetVariableStoreType(
    const spvtools::opt::Instruction& var_decl_inst) {
  const auto type_id = var_decl_inst.type_id();
  auto* var_ref_type = type_mgr_->GetType(type_id);
  if (!var_ref_type) {
    Fail() << "internal error: variable type id " << type_id
           << " has no registered type";
    return nullptr;
  }
  auto* var_ref_ptr_type = var_ref_type->AsPointer();
  if (!var_ref_ptr_type) {
    Fail() << "internal error: variable type id " << type_id
           << " is not a pointer type";
    return nullptr;
  }
  auto var_store_type_id = type_mgr_->GetId(var_ref_ptr_type->pointee_type());
  return parser_impl_.ConvertType(var_store_type_id);
}

bool FunctionEmitter::EmitBody() {
  if (!EmitFunctionVariables()) {
    return false;
  }
  if (!EmitFunctionBodyStatements()) {
    return false;
  }
  return success();
}

bool FunctionEmitter::EmitFunctionVariables() {
  if (failed()) {
    return false;
  }
  for (auto& inst : *function_.entry()) {
    if (inst.opcode() != SpvOpVariable) {
      continue;
    }
    auto* var_store_type = GetVariableStoreType(inst);
    if (failed()) {
      return false;
    }
    auto var = parser_impl_.MakeVariable(
        inst.result_id(), ast::StorageClass::kFunction, var_store_type);
    if (inst.NumInOperands() > 1) {
      // SPIR-V initializers are always constants.
      // (OpenCL also allows the ID of an OpVariable, but we don't handle that
      // here.)
      var->set_constructor(
          parser_impl_.MakeConstantExpression(inst.GetSingleWordInOperand(1)));
    }
    // TODO(dneto): Add the initializer via Variable::set_constructor.
    auto var_decl_stmt =
        std::make_unique<ast::VariableDeclStatement>(std::move(var));
    ast_body_.emplace_back(std::move(var_decl_stmt));
    // Save this as an already-named value.
    identifier_values_.insert(inst.result_id());
  }
  return success();
}

std::unique_ptr<ast::Expression> FunctionEmitter::MakeExpression(uint32_t id) {
  if (failed()) {
    return nullptr;
  }
  if (identifier_values_.count(id)) {
    return std::make_unique<ast::IdentifierExpression>(namer_.Name(id));
  }
  const auto* spirv_constant = constant_mgr_->FindDeclaredConstant(id);
  if (spirv_constant) {
    return parser_impl_.MakeConstantExpression(id);
  }
  const auto* inst = def_use_mgr_->GetDef(id);
  if (inst == nullptr) {
    Fail() << "ID " << id << " does not have a defining SPIR-V instruction";
    return nullptr;
  }
  switch (inst->opcode()) {
    default:
      break;
  }
  Fail() << "unhandled expression for ID " << id << "\n" << inst->PrettyPrint();
  return nullptr;
}

bool FunctionEmitter::EmitFunctionBodyStatements() {
  // TODO(dneto): For now, emit only regular statements in the entry block.
  // We'll use assignments as markers in the tests, to be able to tell where
  // code is placed in control flow. First prove that we can emit assignments.
  return EmitStatementsInBasicBlock(*function_.entry());
}

bool FunctionEmitter::EmitStatementsInBasicBlock(
    const spvtools::opt::BasicBlock& bb) {
  const auto* terminator = bb.terminator();
  const auto* merge = bb.GetMergeInst();  // Might be nullptr
  // Emit regular statements.
  for (auto& inst : bb) {
    if (&inst == terminator || &inst == merge || inst.opcode() == SpvOpLabel ||
        inst.opcode() == SpvOpVariable) {
      continue;
    }
    if (!EmitStatement(inst)) {
      return false;
    }
  }
  // TODO(dneto): Handle the terminator
  return true;
}

bool FunctionEmitter::EmitStatement(const spvtools::opt::Instruction& inst) {
  switch (inst.opcode()) {
    case SpvOpStore: {
      // TODO(dneto): Order of evaluation?
      auto lhs = MakeExpression(inst.GetSingleWordInOperand(0));
      auto rhs = MakeExpression(inst.GetSingleWordInOperand(1));
      ast_body_.emplace_back(std::make_unique<ast::AssignmentStatement>(
          std::move(lhs), std::move(rhs)));
      return success();
    }
    case SpvOpLoad: {
      // Memory accesses must be issued in SPIR-V program order.
      // So represent a load by a new const definition.
      auto ast_initializer = MakeExpression(inst.GetSingleWordInOperand(0));
      if (!ast_initializer) {
        return false;
      }
      auto ast_const =
          parser_impl_.MakeVariable(inst.result_id(), ast::StorageClass::kNone,
                                    parser_impl_.ConvertType(inst.type_id()));
      if (!ast_const) {
        return false;
      }
      ast_const->set_constructor(std::move(ast_initializer));
      ast_const->set_is_const(true);
      ast_body_.emplace_back(
          std::make_unique<ast::VariableDeclStatement>(std::move(ast_const)));
      // Save this as an already-named value.
      identifier_values_.insert(inst.result_id());
      return success();
    }
    case SpvOpFunctionCall:
      // TODO(dneto): Fill this out.  Make this pass, for existing tests
      return success();
    default:
      break;
  }
  return Fail() << "unhandled instruction with opcode " << inst.opcode();
}

}  // namespace spirv
}  // namespace reader
}  // namespace tint