// 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/sem_ir/function.h"

#include <optional>

#include "toolchain/sem_ir/file.h"
#include "toolchain/sem_ir/generic.h"
#include "toolchain/sem_ir/ids.h"

namespace Carbon::SemIR {

auto GetCalleeFunction(const File& sem_ir, InstId callee_id,
                       SpecificId specific_id) -> CalleeFunction {
  CalleeFunction result = {.function_id = FunctionId::None,
                           .enclosing_specific_id = SpecificId::None,
                           .resolved_specific_id = SpecificId::None,
                           .self_type_id = InstId::None,
                           .self_id = InstId::None,
                           .is_error = false};
  if (auto bound_method = sem_ir.insts().TryGetAs<BoundMethod>(callee_id)) {
    result.self_id = bound_method->object_id;
    callee_id = bound_method->function_decl_id;
  }

  if (specific_id.has_value()) {
    callee_id = sem_ir.constant_values().GetInstIdIfValid(
        GetConstantValueInSpecific(sem_ir, specific_id, callee_id));
    CARBON_CHECK(callee_id.has_value(),
                 "Invalid callee id in a specific context");
  }

  if (auto specific_function =
          sem_ir.insts().TryGetAs<SpecificFunction>(callee_id)) {
    result.resolved_specific_id = specific_function->specific_id;
    callee_id = specific_function->callee_id;
  }

  // Identify the function we're calling by its type.
  auto val_id = sem_ir.constant_values().GetConstantInstId(callee_id);
  if (!val_id.has_value()) {
    return result;
  }
  auto fn_type_inst =
      sem_ir.types().GetAsInst(sem_ir.insts().Get(val_id).type_id());

  if (auto impl_fn_type = fn_type_inst.TryAs<FunctionTypeWithSelfType>()) {
    // Combine the associated function's `Self` with the interface function
    // data.
    result.self_type_id = impl_fn_type->self_id;
    fn_type_inst = sem_ir.insts().Get(impl_fn_type->interface_function_type_id);
  }

  auto fn_type = fn_type_inst.TryAs<FunctionType>();
  if (!fn_type) {
    result.is_error = fn_type_inst.Is<ErrorInst>();
    return result;
  }

  result.function_id = fn_type->function_id;
  result.enclosing_specific_id = fn_type->specific_id;
  return result;
}

auto Function::GetParamPatternInfoFromPatternId(const File& sem_ir,
                                                InstId pattern_id)
    -> std::optional<ParamPatternInfo> {
  auto inst_id = pattern_id;
  auto inst = sem_ir.insts().Get(inst_id);

  if (auto addr_pattern = inst.TryAs<AddrPattern>()) {
    inst_id = addr_pattern->inner_id;
    inst = sem_ir.insts().Get(inst_id);
  }

  auto param_pattern_inst = inst.TryAs<AnyParamPattern>();
  if (!param_pattern_inst) {
    return std::nullopt;
  }
  auto param_pattern_id = inst_id;

  inst_id = param_pattern_inst->subpattern_id;
  inst = sem_ir.insts().Get(inst_id);

  auto binding_pattern = inst.As<AnyBindingPattern>();
  return {{.inst_id = param_pattern_id,
           .inst = *param_pattern_inst,
           .entity_name_id = binding_pattern.entity_name_id}};
}

auto Function::GetDeclaredReturnType(const File& file,
                                     SpecificId specific_id) const -> TypeId {
  if (!return_slot_pattern_id.has_value()) {
    return TypeId::None;
  }
  return GetTypeOfInstInSpecific(file, specific_id, return_slot_pattern_id);
}

}  // namespace Carbon::SemIR