//===--- SymbolDocumentation.cpp ==-------------------------------*- C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "SymbolDocumentation.h"

#include "support/Markup.h"
#include "clang/AST/Comment.h"
#include "clang/AST/CommentCommandTraits.h"
#include "clang/AST/CommentVisitor.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"

namespace clang {
namespace clangd {
namespace {

std::string commandMarkerAsString(comments::CommandMarkerKind CommandMarker) {
  switch (CommandMarker) {
  case comments::CommandMarkerKind::CMK_At:
    return "@";
  case comments::CommandMarkerKind::CMK_Backslash:
    return "\\";
  }
  llvm_unreachable("Unknown command marker kind");
}

void commandToMarkup(markup::Paragraph &Out, StringRef Command,
                     comments::CommandMarkerKind CommandMarker,
                     StringRef Args) {
  Out.appendBoldText(commandMarkerAsString(CommandMarker) + Command.str());
  Out.appendSpace();
  if (!Args.empty())
    Out.appendCode(Args.str());
}

template <typename T> std::string getArgText(const T *Command) {
  std::string ArgText;
  for (unsigned I = 0; I < Command->getNumArgs(); ++I) {
    if (!ArgText.empty())
      ArgText += " ";
    ArgText += Command->getArgText(I);
  }
  return ArgText;
}

} // namespace

class ParagraphToMarkupDocument
    : public comments::ConstCommentVisitor<ParagraphToMarkupDocument> {
public:
  ParagraphToMarkupDocument(markup::Paragraph &Out,
                            const comments::CommandTraits &Traits)
      : Out(Out), Traits(Traits) {}

  void visitParagraphComment(const comments::ParagraphComment *C) {
    if (!C)
      return;

    for (const auto *Child = C->child_begin(); Child != C->child_end();
         ++Child) {
      visit(*Child);
    }
  }

  void visitTextComment(const comments::TextComment *C) {
    // Always trim leading space after a newline.
    StringRef Text = C->getText();
    if (LastChunkEndsWithNewline && C->getText().starts_with(' '))
      Text = Text.drop_front();

    LastChunkEndsWithNewline = C->hasTrailingNewline();
    Out.appendText(Text.str() + (LastChunkEndsWithNewline ? "\n" : ""));
  }

  void visitInlineCommandComment(const comments::InlineCommandComment *C) {

    if (C->getNumArgs() > 0) {
      std::string ArgText = getArgText(C);

      switch (C->getRenderKind()) {
      case comments::InlineCommandRenderKind::Monospaced:
        Out.appendCode(ArgText);
        break;
      case comments::InlineCommandRenderKind::Bold:
        Out.appendBoldText(ArgText);
        break;
      case comments::InlineCommandRenderKind::Emphasized:
        Out.appendEmphasizedText(ArgText);
        break;
      default:
        commandToMarkup(Out, C->getCommandName(Traits), C->getCommandMarker(),
                        ArgText);
        break;
      }
    } else {
      if (C->getCommandName(Traits) == "n") {
        // \n is a special case, it is used to create a new line.
        Out.appendText("  \n");
        LastChunkEndsWithNewline = true;
        return;
      }

      commandToMarkup(Out, C->getCommandName(Traits), C->getCommandMarker(),
                      "");
    }
  }

  void visitHTMLStartTagComment(const comments::HTMLStartTagComment *STC) {
    std::string TagText = "<" + STC->getTagName().str();

    for (unsigned I = 0; I < STC->getNumAttrs(); ++I) {
      const comments::HTMLStartTagComment::Attribute &Attr = STC->getAttr(I);
      TagText += " " + Attr.Name.str() + "=\"" + Attr.Value.str() + "\"";
    }

    if (STC->isSelfClosing())
      TagText += " /";
    TagText += ">";

    LastChunkEndsWithNewline = STC->hasTrailingNewline();
    Out.appendText(TagText + (LastChunkEndsWithNewline ? "\n" : ""));
  }

  void visitHTMLEndTagComment(const comments::HTMLEndTagComment *ETC) {
    LastChunkEndsWithNewline = ETC->hasTrailingNewline();
    Out.appendText("</" + ETC->getTagName().str() + ">" +
                   (LastChunkEndsWithNewline ? "\n" : ""));
  }

private:
  markup::Paragraph &Out;
  const comments::CommandTraits &Traits;

  /// If true, the next leading space after a new line is trimmed.
  /// Initially set it to true, to always trim the first text line.
  bool LastChunkEndsWithNewline = true;
};

class ParagraphToString
    : public comments::ConstCommentVisitor<ParagraphToString> {
public:
  ParagraphToString(llvm::raw_string_ostream &Out,
                    const comments::CommandTraits &Traits)
      : Out(Out), Traits(Traits) {}

  void visitParagraphComment(const comments::ParagraphComment *C) {
    if (!C)
      return;

    for (const auto *Child = C->child_begin(); Child != C->child_end();
         ++Child) {
      visit(*Child);
    }
  }

  void visitTextComment(const comments::TextComment *C) { Out << C->getText(); }

  void visitInlineCommandComment(const comments::InlineCommandComment *C) {
    Out << commandMarkerAsString(C->getCommandMarker());
    Out << C->getCommandName(Traits);
    std::string ArgText = getArgText(C);
    if (!ArgText.empty())
      Out << " " << ArgText;
    Out << " ";
  }

  void visitHTMLStartTagComment(const comments::HTMLStartTagComment *STC) {
    Out << "<" << STC->getTagName().str();

    for (unsigned I = 0; I < STC->getNumAttrs(); ++I) {
      const comments::HTMLStartTagComment::Attribute &Attr = STC->getAttr(I);
      Out << " " << Attr.Name.str();
      if (!Attr.Value.str().empty())
        Out << "=\"" << Attr.Value.str() << "\"";
    }

    if (STC->isSelfClosing())
      Out << " /";
    Out << ">";

    Out << (STC->hasTrailingNewline() ? "\n" : "");
  }

  void visitHTMLEndTagComment(const comments::HTMLEndTagComment *ETC) {
    Out << "</" << ETC->getTagName().str() << ">"
        << (ETC->hasTrailingNewline() ? "\n" : "");
  }

private:
  llvm::raw_string_ostream &Out;
  const comments::CommandTraits &Traits;
};

class BlockCommentToMarkupDocument
    : public comments::ConstCommentVisitor<BlockCommentToMarkupDocument> {
public:
  BlockCommentToMarkupDocument(markup::Document &Out,
                               const comments::CommandTraits &Traits)
      : Out(Out), Traits(Traits) {}

  void visitBlockCommandComment(const comments::BlockCommandComment *B) {

    switch (B->getCommandID()) {
    case comments::CommandTraits::KCI_arg:
    case comments::CommandTraits::KCI_li:
      // \li and \arg are special cases, they are used to create a list item.
      // In markdown it is a bullet list.
      ParagraphToMarkupDocument(Out.addBulletList().addItem().addParagraph(),
                                Traits)
          .visit(B->getParagraph());
      break;
    case comments::CommandTraits::KCI_note:
    case comments::CommandTraits::KCI_warning:
      commandToHeadedParagraph(B);
      break;
    case comments::CommandTraits::KCI_retval: {
      // The \retval command describes the return value given as its single
      // argument in the corresponding paragraph.
      // Note: We know that we have exactly one argument but not if it has an
      // associated paragraph.
      auto &P = Out.addParagraph().appendCode(getArgText(B));
      if (B->getParagraph() && !B->getParagraph()->isWhitespace()) {
        P.appendText(" - ");
        ParagraphToMarkupDocument(P, Traits).visit(B->getParagraph());
      }
      return;
    }
    case comments::CommandTraits::KCI_details: {
      // The \details command is just used to separate the brief from the
      // detailed description. This separation is already done in the
      // SymbolDocCommentVisitor. Therefore we can omit the command itself
      // here and just process the paragraph.
      if (B->getParagraph() && !B->getParagraph()->isWhitespace()) {
        ParagraphToMarkupDocument(Out.addParagraph(), Traits)
            .visit(B->getParagraph());
      }
      return;
    }
    default: {
      // Some commands have arguments, like \throws.
      // The arguments are not part of the paragraph.
      // We need reconstruct them here.
      std::string ArgText = getArgText(B);
      auto &P = Out.addParagraph();
      commandToMarkup(P, B->getCommandName(Traits), B->getCommandMarker(),
                      ArgText);
      if (B->getParagraph() && !B->getParagraph()->isWhitespace()) {
        // For commands with arguments, the paragraph starts after the first
        // space. Therefore we need to append a space manually in this case.
        if (!ArgText.empty())
          P.appendSpace();
        ParagraphToMarkupDocument(P, Traits).visit(B->getParagraph());
      }
    }
    }
  }

  void visitCodeCommand(const comments::VerbatimBlockComment *VB) {
    std::string CodeLang = "";
    auto *FirstLine = VB->child_begin();
    // The \\code command has an optional language argument.
    // This argument is currently not parsed by the clang doxygen parser.
    // Therefore we try to extract it from the first line of the verbatim
    // block.
    if (VB->getNumLines() > 0) {
      if (const auto *Line =
              cast<comments::VerbatimBlockLineComment>(*FirstLine)) {
        llvm::StringRef Text = Line->getText();
        // Language is a single word enclosed in {}.
        if (llvm::none_of(Text, llvm::isSpace) && Text.consume_front("{") &&
            Text.consume_back("}")) {
          // drop a potential . since this is not supported in Markdown
          // fenced code blocks.
          Text.consume_front(".");
          // Language is alphanumeric or '+'.
          CodeLang = Text.take_while([](char C) {
                           return llvm::isAlnum(C) || C == '+';
                         })
                         .str();
          // Skip the first line for the verbatim text.
          ++FirstLine;
        }
      }
    }

    std::string CodeBlockText;

    for (const auto *LI = FirstLine; LI != VB->child_end(); ++LI) {
      if (const auto *Line = cast<comments::VerbatimBlockLineComment>(*LI)) {
        CodeBlockText += Line->getText().str() + "\n";
      }
    }

    Out.addCodeBlock(CodeBlockText, CodeLang);
  }

  void visitVerbatimBlockComment(const comments::VerbatimBlockComment *VB) {
    // The \\code command is a special verbatim block command which we handle
    // separately.
    if (VB->getCommandID() == comments::CommandTraits::KCI_code) {
      visitCodeCommand(VB);
      return;
    }

    commandToMarkup(Out.addParagraph(), VB->getCommandName(Traits),
                    VB->getCommandMarker(), "");

    std::string VerbatimText;

    for (const auto *LI = VB->child_begin(); LI != VB->child_end(); ++LI) {
      if (const auto *Line = cast<comments::VerbatimBlockLineComment>(*LI)) {
        VerbatimText += Line->getText().str() + "\n";
      }
    }

    Out.addCodeBlock(VerbatimText, "");

    commandToMarkup(Out.addParagraph(), VB->getCloseName(),
                    VB->getCommandMarker(), "");
  }

  void visitVerbatimLineComment(const comments::VerbatimLineComment *VL) {
    auto &P = Out.addParagraph();
    commandToMarkup(P, VL->getCommandName(Traits), VL->getCommandMarker(), "");
    P.appendSpace().appendCode(VL->getText().str(), true).appendSpace();
  }

private:
  markup::Document &Out;
  const comments::CommandTraits &Traits;
  StringRef CommentEscapeMarker;

  /// Emphasize the given command in a paragraph.
  /// Uses the command name with the first letter capitalized as the heading.
  void commandToHeadedParagraph(const comments::BlockCommandComment *B) {
    auto &P = Out.addParagraph();
    std::string Heading = B->getCommandName(Traits).slice(0, 1).upper() +
                          B->getCommandName(Traits).drop_front().str();
    P.appendBoldText(Heading + ":");
    P.appendText("  \n");
    ParagraphToMarkupDocument(P, Traits).visit(B->getParagraph());
  }
};

void SymbolDocCommentVisitor::preprocessDocumentation(StringRef Doc) {
  enum State {
    Normal,
    FencedCodeblock,
  } State = Normal;
  std::string CodeFence;

  llvm::raw_string_ostream OS(CommentWithMarkers);

  // The documentation string is processed line by line.
  // The raw documentation string does not contain the comment markers
  // (e.g. /// or /** */).
  // But the comment lexer expects doxygen markers, so add them back.
  // We need to use the /// style doxygen markers because the comment could
  // contain the closing tag "*/" of a C Style "/** */" comment
  // which would break the parsing if we would just enclose the comment text
  // with "/** */".

  // Escape doxygen commands inside markdown inline code spans.
  // This is required to not let the doxygen parser interpret them as
  // commands.
  // Note: This is a heuristic which may fail in some cases.
  bool InCodeSpan = false;

  llvm::StringRef Line, Rest;
  for (std::tie(Line, Rest) = Doc.split('\n'); !(Line.empty() && Rest.empty());
       std::tie(Line, Rest) = Rest.split('\n')) {

    // Detect code fence (``` or ~~~)
    if (State == Normal) {
      llvm::StringRef Trimmed = Line.ltrim();
      if (Trimmed.starts_with("```") || Trimmed.starts_with("~~~")) {
        // https://www.doxygen.nl/manual/markdown.html#md_fenced
        CodeFence =
            Trimmed.take_while([](char C) { return C == '`' || C == '~'; })
                .str();
        // Try to detect language: first word after fence. Could also be
        // enclosed in {}
        llvm::StringRef AfterFence =
            Trimmed.drop_front(CodeFence.size()).ltrim();
        // ignore '{' at the beginning of the language name to not duplicate it
        // for the doxygen command
        AfterFence.consume_front("{");
        // The name is alphanumeric or '.' or '+'
        StringRef CodeLang = AfterFence.take_while(
            [](char C) { return llvm::isAlnum(C) || C == '.' || C == '+'; });

        OS << "///@code";

        if (!CodeLang.empty())
          OS << "{" << CodeLang.str() << "}";

        OS << "\n";

        State = FencedCodeblock;
        continue;
      }

      // FIXME: handle indented code blocks too?
      // In doxygen, the indentation which triggers a code block depends on the
      // indentation of the previous paragraph.
      // https://www.doxygen.nl/manual/markdown.html#mddox_code_blocks
    } else if (State == FencedCodeblock) {
      // End of code fence
      if (Line.ltrim().starts_with(CodeFence)) {
        OS << "///@endcode\n";
        State = Normal;
        continue;
      }
      OS << "///" << Line << "\n";
      continue;
    }

    // Normal line preprocessing (add doxygen markers, handle escaping)
    OS << "///";

    if (Line.empty() || Line.trim().empty()) {
      OS << "\n";
      // Empty lines reset the InCodeSpan state.
      InCodeSpan = false;
      continue;
    }

    if (Line.starts_with("<"))
      // A comment line starting with '///<' is treated as a doxygen
      // command. To avoid this, we add a space before the '<'.
      OS << ' ';

    for (char C : Line) {
      if (C == '`')
        InCodeSpan = !InCodeSpan;
      else if (InCodeSpan && (C == '@' || C == '\\'))
        OS << '\\';
      OS << C;
    }

    OS << "\n";
  }

  // Close any unclosed code block
  if (State == FencedCodeblock)
    OS << "///@endcode\n";
}

void SymbolDocCommentVisitor::visitBlockCommandComment(
    const comments::BlockCommandComment *B) {
  switch (B->getCommandID()) {
  case comments::CommandTraits::KCI_brief: {
    if (!BriefParagraph) {
      BriefParagraph = B->getParagraph();
      return;
    }
    break;
  }
  case comments::CommandTraits::KCI_return:
  case comments::CommandTraits::KCI_returns:
    if (!ReturnParagraph) {
      ReturnParagraph = B->getParagraph();
      return;
    }
    break;
  case comments::CommandTraits::KCI_retval:
    // Only consider retval commands having an argument.
    // The argument contains the described return value which is needed to
    // convert it to markup.
    if (B->getNumArgs() == 1)
      RetvalCommands.push_back(B);
    return;
  default:
    break;
  }

  // For all other commands, we store them in the BlockCommands map.
  // This allows us to keep the order of the comments.
  BlockCommands[CommentPartIndex] = B;
  CommentPartIndex++;
}

void SymbolDocCommentVisitor::briefToMarkup(markup::Paragraph &Out) const {
  if (!BriefParagraph)
    return;
  ParagraphToMarkupDocument(Out, Traits).visit(BriefParagraph);
}

void SymbolDocCommentVisitor::returnToMarkup(markup::Paragraph &Out) const {
  if (!ReturnParagraph)
    return;
  ParagraphToMarkupDocument(Out, Traits).visit(ReturnParagraph);
}

void SymbolDocCommentVisitor::parameterDocToMarkup(
    StringRef ParamName, markup::Paragraph &Out) const {
  if (ParamName.empty())
    return;

  if (const auto *P = Parameters.lookup(ParamName)) {
    ParagraphToMarkupDocument(Out, Traits).visit(P->getParagraph());
  }
}

void SymbolDocCommentVisitor::parameterDocToString(
    StringRef ParamName, llvm::raw_string_ostream &Out) const {
  if (ParamName.empty())
    return;

  if (const auto *P = Parameters.lookup(ParamName)) {
    ParagraphToString(Out, Traits).visit(P->getParagraph());
  }
}

void SymbolDocCommentVisitor::detailedDocToMarkup(markup::Document &Out) const {
  for (unsigned I = 0; I < CommentPartIndex; ++I) {
    if (const auto *BC = BlockCommands.lookup(I)) {
      BlockCommentToMarkupDocument(Out, Traits).visit(BC);
    } else if (const auto *P = FreeParagraphs.lookup(I)) {
      ParagraphToMarkupDocument(Out.addParagraph(), Traits).visit(P);
    }
  }
}

void SymbolDocCommentVisitor::templateTypeParmDocToMarkup(
    StringRef TemplateParamName, markup::Paragraph &Out) const {
  if (TemplateParamName.empty())
    return;

  if (const auto *TP = TemplateParameters.lookup(TemplateParamName)) {
    ParagraphToMarkupDocument(Out, Traits).visit(TP->getParagraph());
  }
}

void SymbolDocCommentVisitor::templateTypeParmDocToString(
    StringRef TemplateParamName, llvm::raw_string_ostream &Out) const {
  if (TemplateParamName.empty())
    return;

  if (const auto *P = TemplateParameters.lookup(TemplateParamName)) {
    ParagraphToString(Out, Traits).visit(P->getParagraph());
  }
}

void SymbolDocCommentVisitor::retvalsToMarkup(markup::Document &Out) const {
  if (RetvalCommands.empty())
    return;
  markup::BulletList &BL = Out.addBulletList();
  for (const auto *P : RetvalCommands) {
    BlockCommentToMarkupDocument(BL.addItem(), Traits).visit(P);
  }
}

} // namespace clangd
} // namespace clang