// SPDX-License-Identifier: Apache-2.0

// SPDX-FileCopyrightText: 2019-2024 Second State INC

#include "loader/loader.h"

using namespace std::literals;

namespace WasmEdge {

namespace Loader {

Expect<std::pair<std::vector<Byte>, std::vector<Byte>>> Loader::loadPreamble() {

  // component ::= <preamble> s*:<section>* => (component flatten(s*))

  // preamble  ::= <magic> <version> <layer>

  // magic     ::= 0x00 0x61 0x73 0x6D

  // version   ::= 0x0a 0x00

  // layer     ::= 0x01 0x00

  // The combination of version and layer is corresponding to the version of

  // core wasm.

  // The core module has same magic but the different version:

  // 0x01 0x00 0x00 0x00

  auto Magic = FMgr.readBytes(4);

  if (!Magic) {

    return logLoadError(Magic.error(), FMgr.getLastOffset(),

                        ASTNodeAttr::Module);

  }

  std::vector<Byte> WasmMagic = {0x00, 0x61, 0x73, 0x6D};

  if (*Magic != WasmMagic) {

    auto M = *Magic;

    spdlog::error("Might an invalid wasm file, magic expected, but got 0x{:X} "

                  "0x{:X} 0x{:X} 0x{:X}"sv,

                  M[0], M[1], M[2], M[3]);

    return logLoadError(ErrCode::Value::MalformedMagic, FMgr.getLastOffset(),

                        ASTNodeAttr::Module);

  }

  auto Ver = FMgr.readBytes(4);

  if (!Ver) {

    return logLoadError(Ver.error(), FMgr.getLastOffset(), ASTNodeAttr::Module);

  }

  return std::make_pair(*Magic, *Ver);

}

Expect<void> Loader::loadComponent(AST::Component::Component &Comp,

                                   std::optional<uint64_t> Bound) {

  auto ReportError = [](auto E) {

    spdlog::error(ErrInfo::InfoAST(ASTNodeAttr::Component));

    return E;

  };

  // component ::= <preamble> s*:<section>*           => (component flatten(s*))

  // section   ::=    section_0(<core:custom>)        => ϵ

  //             | m: section_1(<core:module>)        => [core-prefix(m)]

  //             | i*:section_2(vec(<core:instance>)) => core-prefix(i)*

  //             | t*:section_3(vec(<core:type>))     => core-prefix(t)*

  //             | c: section_4(<component>)          => [c]

  //             | i*:section_5(vec(<instance>))      => i*

  //             | a*:section_6(vec(<alias>))         => a*

  //             | t*:section_7(vec(<type>))          => t*

  //             | c*:section_8(vec(<canon>))         => c*

  //             | s: section_9(<start>)              => [s]

  //             | i*:section_10(vec(<import>))       => i*

  //             | e*:section_11(vec(<export>))       => e*

  //             | v*:section_12(vec(<value>))        => v* 🪙

  uint64_t StartOffset = FMgr.getOffset();

  uint64_t Offset = FMgr.getOffset();

  Expect<Byte> ResSecId;

  while ((!Bound.has_value() || *Bound > Offset - StartOffset) &&

         (ResSecId = FMgr.readByte())) {

    if (!ResSecId) {

      return logLoadError(ResSecId.error(), FMgr.getLastOffset(),

                          ASTNodeAttr::Component);

    }

    // keep going only if we have new section ID

    uint8_t NewSectionId = *ResSecId;

    Comp.getSections().emplace_back();

    auto &Sec = Comp.getSections().back();

    switch (NewSectionId) {

    case 0x00:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::CustomSection>())

                       .map_error(ReportError));

      break;

    case 0x01:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::CoreModuleSection>())

                       .map_error(ReportError));

      break;

    case 0x02:

      EXPECTED_TRY(

          loadSection(Sec.emplace<AST::Component::CoreInstanceSection>())

              .map_error(ReportError));

      break;

    case 0x03:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::CoreTypeSection>())

                       .map_error(ReportError));

      break;

    case 0x04:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::ComponentSection>())

                       .map_error(ReportError));

      break;

    case 0x05:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::InstanceSection>())

                       .map_error(ReportError));

      break;

    case 0x06:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::AliasSection>())

                       .map_error(ReportError));

      break;

    case 0x07:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::TypeSection>())

                       .map_error(ReportError));

      break;

    case 0x08:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::CanonSection>())

                       .map_error(ReportError));

      break;

    case 0x09:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::StartSection>())

                       .map_error(ReportError));

      break;

    case 0x0A:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::ImportSection>())

                       .map_error(ReportError));

      break;

    case 0x0B:

      EXPECTED_TRY(loadSection(Sec.emplace<AST::Component::ExportSection>())

                       .map_error(ReportError));

      break;

    default:

      return logLoadError(ErrCode::Value::MalformedSection,

                          FMgr.getLastOffset(), ASTNodeAttr::Component);

    }

    Offset = FMgr.getOffset();

  }

  return {};

}

} // namespace Loader

} // namespace WasmEdge