// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "toolchain/lower/function_context.h"
#include "toolchain/sem_ir/expr_info.h"
#include "toolchain/sem_ir/file.h"

namespace Carbon::Lower {

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::BindValue inst) -> void {
  auto inst_type = context.GetTypeIdOfInst(inst_id);
  switch (context.GetValueRepr(inst_type).repr.kind) {
    case SemIR::ValueRepr::Unknown:
      CARBON_FATAL(
          "Value acquisition for type with incomplete value representation");
    case SemIR::ValueRepr::Dependent:
      CARBON_FATAL(
          "Value acquisition for type with dependent value representation");
    case SemIR::ValueRepr::None:
      // Nothing should use this value, but StubRef needs a value to
      // propagate.
      // TODO: Remove this now the StubRefs are gone.
      context.SetLocal(inst_id,
                       llvm::PoisonValue::get(context.GetType(inst_type)));
      break;
    case SemIR::ValueRepr::Copy:
      context.SetLocal(
          inst_id,
          context.LoadObject(inst_type, context.GetValue(inst.value_id)));
      break;
    case SemIR::ValueRepr::Pointer:
      context.SetLocal(inst_id, context.GetValue(inst.value_id));
      break;
    case SemIR::ValueRepr::Custom:
      CARBON_FATAL("TODO: Add support for BindValue with custom value rep");
  }
}

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::InPlaceInit inst) -> void {
  auto type = context.GetTypeIdOfInst(inst_id);
  auto* value = context.GetValue(inst.dest_id);

  // If the initializing representation is by-value, and the value
  // representation is by-copy, then we need to load from the storage. Otherwise
  // we want a pointer to the result.
  switch (context.GetInitRepr(type).kind) {
    case SemIR::InitRepr::None:
    case SemIR::InitRepr::InPlace:
      break;
    case SemIR::InitRepr::ByCopy:
      switch (context.GetValueRepr(type).repr.kind) {
        case SemIR::ValueRepr::Unknown:
          CARBON_FATAL("Unexpected incomplete type");
        case SemIR::ValueRepr::Dependent:
          CARBON_FATAL("Unexpected dependent type");
        case SemIR::ValueRepr::None:
        case SemIR::ValueRepr::Pointer:
          break;
        case SemIR::ValueRepr::Copy:
          value = context.builder().CreateLoad(context.GetType(type), value);
          break;
        case SemIR::ValueRepr::Custom:
          CARBON_FATAL(
              "TODO: Add support for InPlaceInit with custom value rep");
      }
      break;
    case SemIR::InitRepr::Incomplete:
      CARBON_FATAL("Unexpected incomplete type");
    case SemIR::InitRepr::Dependent:
      CARBON_FATAL("Unexpected dependent type");
  }

  context.SetLocal(inst_id, value);
}

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::Temporary inst) -> void {
  context.FinishInit(context.GetTypeIdOfInst(inst_id), inst.storage_id,
                     inst.init_id);
  context.SetLocal(inst_id, context.GetValue(inst.storage_id));
}

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::TemporaryStorage /*inst*/) -> void {
  context.SetLocal(
      inst_id, context.CreateAlloca(context.GetTypeOfInst(inst_id), "temp"));
}

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::ValueAsRef inst) -> void {
  CARBON_CHECK(SemIR::GetExprCategory(context.sem_ir(), inst.value_id) ==
               SemIR::ExprCategory::Value);
  auto inst_type = context.GetTypeIdOfInst(inst_id);
  auto value_repr = context.GetValueRepr(inst_type);
  CARBON_CHECK(value_repr.repr.kind == SemIR::ValueRepr::Pointer);
  context.SetLocal(inst_id, context.GetValue(inst.value_id));
}

auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                SemIR::ValueOfInitializer inst) -> void {
  CARBON_CHECK(SemIR::GetExprCategory(context.sem_ir(), inst.init_id) ==
               SemIR::ExprCategory::Initializing);
  auto inst_type = context.GetTypeIdOfInst(inst_id);
  auto value_repr = context.GetValueRepr(inst_type);
  auto init_repr = context.GetInitRepr(inst_type);
  CARBON_CHECK(value_repr.repr.kind == SemIR::ValueRepr::Copy);
  CARBON_CHECK(init_repr.kind == SemIR::InitRepr::ByCopy);
  context.SetLocal(inst_id, context.GetValue(inst.init_id));
}

}  // namespace Carbon::Lower