//===-- ResourceFileWriter.cpp --------------------------------*- C++-*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//
//
// This implements the visitor serializing resources to a .res stream.
//
//===---------------------------------------------------------------------===//

#include "ResourceFileWriter.h"

#include "llvm/Object/WindowsResource.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/EndianStream.h"

using namespace llvm::support;

// Take an expression returning llvm::Error and forward the error if it exists.
#define RETURN_IF_ERROR(Expr)                                                  \
  if (auto Err = (Expr))                                                       \
    return Err;

namespace llvm {
namespace rc {

static Error createError(Twine Message,
                         std::errc Type = std::errc::invalid_argument) {
  return make_error<StringError>(Message, std::make_error_code(Type));
}

static Error checkNumberFits(uint32_t Number, size_t MaxBits, Twine FieldName) {
  assert(1 <= MaxBits && MaxBits <= 32);
  if (!(Number >> MaxBits))
    return Error::success();
  return createError(FieldName + " (" + Twine(Number) + ") does not fit in " +
                         Twine(MaxBits) + " bits.",
                     std::errc::value_too_large);
}

template <typename FitType>
static Error checkNumberFits(uint32_t Number, Twine FieldName) {
  return checkNumberFits(Number, sizeof(FitType) * 8, FieldName);
}

static Error checkIntOrString(IntOrString Value, Twine FieldName) {
  if (!Value.isInt())
    return Error::success();
  return checkNumberFits<uint16_t>(Value.getInt(), FieldName);
}

static bool stripQuotes(StringRef &Str, bool &IsLongString) {
  if (!Str.contains('"'))
    return false;

  // Just take the contents of the string, checking if it's been marked long.
  IsLongString = Str.startswith_lower("L");
  if (IsLongString)
    Str = Str.drop_front();

  bool StripSuccess = Str.consume_front("\"") && Str.consume_back("\"");
  (void)StripSuccess;
  assert(StripSuccess && "Strings should be enclosed in quotes.");
  return true;
}

// Describes a way to handle '\0' characters when processing the string.
// rc.exe tool sometimes behaves in a weird way in postprocessing.
// If the string to be output is equivalent to a C-string (e.g. in MENU
// titles), string is (predictably) truncated after first 0-byte.
// When outputting a string table, the behavior is equivalent to appending
// '\0\0' at the end of the string, and then stripping the string
// before the first '\0\0' occurrence.
// Finally, when handling strings in user-defined resources, 0-bytes
// aren't stripped, nor do they terminate the string.

enum class NullHandlingMethod {
  UserResource,   // Don't terminate string on '\0'.
  CutAtNull,      // Terminate string on '\0'.
  CutAtDoubleNull // Terminate string on '\0\0'; strip final '\0'.
};

// Parses an identifier or string and returns a processed version of it.
// For now, it only strips the string boundaries, but TODO:
//   * Squash "" to a single ".
//   * Replace the escape sequences with their processed version.
// For identifiers, this is no-op.
static Error processString(StringRef Str, NullHandlingMethod NullHandler,
                           bool &IsLongString, SmallVectorImpl<UTF16> &Result) {
  assert(NullHandler == NullHandlingMethod::CutAtNull);

  bool IsString = stripQuotes(Str, IsLongString);
  convertUTF8ToUTF16String(Str, Result);

  if (!IsString) {
    // It's an identifier if it's not a string. Make all characters uppercase.
    for (UTF16 &Ch : Result) {
      assert(Ch <= 0x7F && "We didn't allow identifiers to be non-ASCII");
      Ch = toupper(Ch);
    }
    return Error::success();
  }

  // We don't process the string contents. Only cut at '\0'.

  for (size_t Pos = 0; Pos < Result.size(); ++Pos)
    if (Result[Pos] == '\0')
      Result.resize(Pos);

  return Error::success();
}

uint64_t ResourceFileWriter::writeObject(const ArrayRef<uint8_t> Data) {
  uint64_t Result = tell();
  FS->write((const char *)Data.begin(), Data.size());
  return Result;
}

Error ResourceFileWriter::writeCString(StringRef Str, bool WriteTerminator) {
  SmallVector<UTF16, 128> ProcessedString;
  bool IsLongString;
  RETURN_IF_ERROR(processString(Str, NullHandlingMethod::CutAtNull,
                                IsLongString, ProcessedString));
  for (auto Ch : ProcessedString)
    writeInt<uint16_t>(Ch);
  if (WriteTerminator)
    writeInt<uint16_t>(0);
  return Error::success();
}

Error ResourceFileWriter::writeIdentifier(const IntOrString &Ident) {
  return writeIntOrString(Ident);
}

Error ResourceFileWriter::writeIntOrString(const IntOrString &Value) {
  if (!Value.isInt())
    return writeCString(Value.getString());

  writeInt<uint16_t>(0xFFFF);
  writeInt<uint16_t>(Value.getInt());
  return Error::success();
}

Error ResourceFileWriter::appendFile(StringRef Filename) {
  bool IsLong;
  stripQuotes(Filename, IsLong);

  // Filename path should be relative to the current working directory.
  // FIXME: docs say so, but reality is more complicated, script
  // location and include paths must be taken into account.
  ErrorOr<std::unique_ptr<MemoryBuffer>> File =
      MemoryBuffer::getFile(Filename, -1, false);
  if (!File)
    return make_error<StringError>("Error opening file '" + Filename +
                                       "': " + File.getError().message(),
                                   File.getError());
  *FS << (*File)->getBuffer();
  return Error::success();
}

void ResourceFileWriter::padStream(uint64_t Length) {
  assert(Length > 0);
  uint64_t Location = tell();
  Location %= Length;
  uint64_t Pad = (Length - Location) % Length;
  for (uint64_t i = 0; i < Pad; ++i)
    writeInt<uint8_t>(0);
}

Error ResourceFileWriter::handleError(Error &&Err, const RCResource *Res) {
  if (Err)
    return joinErrors(createError("Error in " + Res->getResourceTypeName() +
                                  " statement (ID " + Twine(Res->ResName) +
                                  "): "),
                      std::move(Err));
  return Error::success();
}

Error ResourceFileWriter::visitNullResource(const RCResource *Res) {
  return writeResource(Res, &ResourceFileWriter::writeNullBody);
}

Error ResourceFileWriter::visitHTMLResource(const RCResource *Res) {
  return writeResource(Res, &ResourceFileWriter::writeHTMLBody);
}

Error ResourceFileWriter::visitLanguageStmt(const LanguageResource *Stmt) {
  RETURN_IF_ERROR(checkNumberFits(Stmt->Lang, 10, "Primary language ID"));
  RETURN_IF_ERROR(checkNumberFits(Stmt->SubLang, 6, "Sublanguage ID"));
  ObjectData.LanguageInfo = Stmt->Lang | (Stmt->SubLang << 10);
  return Error::success();
}

Error ResourceFileWriter::writeResource(
    const RCResource *Res,
    Error (ResourceFileWriter::*BodyWriter)(const RCResource *)) {
  // We don't know the sizes yet.
  object::WinResHeaderPrefix HeaderPrefix{ulittle32_t(0U), ulittle32_t(0U)};
  uint64_t HeaderLoc = writeObject(HeaderPrefix);

  auto ResType = Res->getResourceType();
  RETURN_IF_ERROR(checkIntOrString(ResType, "Resource type"));
  RETURN_IF_ERROR(checkIntOrString(Res->ResName, "Resource ID"));
  RETURN_IF_ERROR(handleError(writeIdentifier(ResType), Res));
  RETURN_IF_ERROR(handleError(writeIdentifier(Res->ResName), Res));

  padStream(sizeof(uint32_t));
  object::WinResHeaderSuffix HeaderSuffix{
      ulittle32_t(0), // DataVersion; seems to always be 0
      ulittle16_t(Res->getMemoryFlags()), ulittle16_t(ObjectData.LanguageInfo),
      ulittle32_t(0),  // VersionInfo
      ulittle32_t(0)}; // Characteristics
  writeObject(HeaderSuffix);

  uint64_t DataLoc = tell();
  RETURN_IF_ERROR(handleError((this->*BodyWriter)(Res), Res));
  // RETURN_IF_ERROR(handleError(dumpResource(Ctx)));

  // Update the sizes.
  HeaderPrefix.DataSize = tell() - DataLoc;
  HeaderPrefix.HeaderSize = DataLoc - HeaderLoc;
  writeObjectAt(HeaderPrefix, HeaderLoc);
  padStream(sizeof(uint32_t));

  return Error::success();
}

Error ResourceFileWriter::writeNullBody(const RCResource *) {
  return Error::success();
}

Error ResourceFileWriter::writeHTMLBody(const RCResource *Base) {
  return appendFile(cast<HTMLResource>(Base)->HTMLLoc);
}

} // namespace rc
} // namespace llvm