//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "swift/Parse/Lexer.h"
#include "swift/Refactoring/Refactoring.h"

using namespace swift;
using namespace swift::ide;

namespace {

class RenameRangeDetailCollector {
  const SourceManager &SM;
  const DeclNameViewer Old;
  /// The ranges that have been collect.
  ///
  /// This is the result of the `RenameRangeDetailCollector` and can be
  /// retrieved with `getResult`.
  std::vector<RenameRangeDetail> Ranges;

public:
  RenameRangeDetailCollector(const SourceManager &SM, StringRef OldName)
      : SM(SM), Old(OldName) {}

  virtual ~RenameRangeDetailCollector() {}

  RegionType addSyntacticRenameRanges(const ResolvedLoc &Resolved,
                                      const RenameLoc &Config);

  std::vector<RenameRangeDetail> &&takeResult() { return std::move(Ranges); }

private:
  void addRenameRange(CharSourceRange Label, RefactoringRangeKind RangeKind,
                      std::optional<unsigned> NameIndex);

  /// Adds a replacement to rename the given base name range
  /// \return true if the given range does not match the old name
  bool renameBase(CharSourceRange Range, RefactoringRangeKind RangeKind);

  /// Adds replacements to rename the given label ranges
  /// \return true if the label ranges do not match the old name
  bool renameLabels(ArrayRef<CharSourceRange> LabelRanges,
                    std::optional<unsigned> FirstTrailingLabel,
                    LabelRangeType RangeType, bool isCallSite);

private:
  /// Returns the range of the  (possibly escaped) identifier at the start of
  /// \p Range and updates \p IsEscaped to indicate whether it's escaped or not.
  CharSourceRange getLeadingIdentifierRange(CharSourceRange Range,
                                            bool &IsEscaped);

  CharSourceRange stripBackticks(CharSourceRange Range);

  void splitAndRenameLabel(CharSourceRange Range, LabelRangeType RangeType,
                           size_t NameIndex);

  void splitAndRenameParamLabel(CharSourceRange Range, size_t NameIndex,
                                bool IsCollapsible);

  void splitAndRenameCallArg(CharSourceRange Range, size_t NameIndex);

  bool labelRangeMatches(CharSourceRange Range, LabelRangeType RangeType,
                         StringRef Expected);

  bool renameLabelsLenient(ArrayRef<CharSourceRange> LabelRanges,
                           std::optional<unsigned> FirstTrailingLabel,
                           LabelRangeType RangeType);

  static RegionType getSyntacticRenameRegionType(const ResolvedLoc &Resolved);
};

void RenameRangeDetailCollector::addRenameRange(
    CharSourceRange Label, RefactoringRangeKind RangeKind,
    std::optional<unsigned> NameIndex) {
  Ranges.push_back({Label, RangeKind, NameIndex});
}

bool RenameRangeDetailCollector::renameBase(CharSourceRange Range,
                                            RefactoringRangeKind RangeKind) {
  assert(Range.isValid());

  if (stripBackticks(Range).str() != Old.base())
    return true;
  addRenameRange(Range, RangeKind, std::nullopt);
  return false;
}

bool RenameRangeDetailCollector::renameLabels(
    ArrayRef<CharSourceRange> LabelRanges,
    std::optional<unsigned> FirstTrailingLabel, LabelRangeType RangeType,
    bool isCallSite) {
  if (isCallSite)
    return renameLabelsLenient(LabelRanges, FirstTrailingLabel, RangeType);

  assert(!FirstTrailingLabel);
  ArrayRef<StringRef> OldLabels = Old.args();

  if (OldLabels.size() != LabelRanges.size())
    return true;

  size_t Index = 0;
  for (const auto &LabelRange : LabelRanges) {
    assert(LabelRange.isValid());
    if (!labelRangeMatches(LabelRange, RangeType, OldLabels[Index]))
      return true;
    splitAndRenameLabel(LabelRange, RangeType, Index++);
  }
  return false;
}

CharSourceRange
RenameRangeDetailCollector::getLeadingIdentifierRange(CharSourceRange Range,
                                                      bool &IsEscaped) {
  assert(Range.isValid() && Range.getByteLength());
  IsEscaped = Range.str().front() == '`';
  SourceLoc Start = Range.getStart();
  if (IsEscaped)
    Start = Start.getAdvancedLoc(1);
  return Lexer::getCharSourceRangeFromSourceRange(SM, Start);
}

CharSourceRange
RenameRangeDetailCollector::stripBackticks(CharSourceRange Range) {
  StringRef Content = Range.str();
  if (Content.size() < 3 || Content.front() != '`' || Content.back() != '`') {
    return Range;
  }
  return CharSourceRange(Range.getStart().getAdvancedLoc(1),
                         Range.getByteLength() - 2);
}

void RenameRangeDetailCollector::splitAndRenameLabel(CharSourceRange Range,
                                                     LabelRangeType RangeType,
                                                     size_t NameIndex) {
  switch (RangeType) {
  case LabelRangeType::CallArg:
    return splitAndRenameCallArg(Range, NameIndex);
  case LabelRangeType::Param:
    return splitAndRenameParamLabel(Range, NameIndex, /*IsCollapsible=*/true);
  case LabelRangeType::EnumCaseParam:
    if (Range.getByteLength() == 0) {
      // If the associated value currently doesn't have a label, emit a
      // `CallArgumentCombined` range, which will cause a new label followed by
      // `:` to be inserted in the same fashion that call arguments get inserted
      // to calls
      return addRenameRange(Range, RefactoringRangeKind::CallArgumentCombined, NameIndex);
    } else {
      // If the associated value has a label already, we are in the same case as
      // function parameters.
      return splitAndRenameParamLabel(Range, NameIndex, /*IsCollapsible=*/true);
    }
  case LabelRangeType::NoncollapsibleParam:
    return splitAndRenameParamLabel(Range, NameIndex,
                                    /*IsCollapsible=*/false);
  case LabelRangeType::CompoundName:
    return addRenameRange(Range, RefactoringRangeKind::SelectorArgumentLabel,
                          NameIndex);
  case LabelRangeType::None:
    llvm_unreachable("expected a label range");
  }
}

void RenameRangeDetailCollector::splitAndRenameParamLabel(CharSourceRange Range,
                                                          size_t NameIndex,
                                                          bool IsCollapsible) {
  // Split parameter range foo([a b]: Int) into decl argument label [a] and
  // parameter name [b] or noncollapsible parameter name [b] if IsCollapsible
  // is false (as for subscript decls). If we have only foo([a]: Int), then we
  // add an empty range for the local name, or for the decl argument label if
  // IsCollapsible is false.
  StringRef Content = Range.str();
  size_t ExternalNameEnd = Content.find_first_of(" \t\n\v\f\r/");

  if (ExternalNameEnd == StringRef::npos) { // foo([a]: Int)
    if (IsCollapsible) {
      addRenameRange(Range, RefactoringRangeKind::DeclArgumentLabel, NameIndex);
      addRenameRange(CharSourceRange{Range.getEnd(), 0},
                     RefactoringRangeKind::ParameterName, NameIndex);
    } else {
      addRenameRange(CharSourceRange{Range.getStart(), 0},
                     RefactoringRangeKind::DeclArgumentLabel, NameIndex);
      addRenameRange(Range, RefactoringRangeKind::NoncollapsibleParameterName,
                     NameIndex);
    }
  } else { // foo([a b]: Int)
    CharSourceRange Ext{Range.getStart(), unsigned(ExternalNameEnd)};

    // Note: we consider the leading whitespace part of the parameter name
    // if the parameter is collapsible, since if the parameter is collapsed
    // into a matching argument label, we want to remove the whitespace too.
    // FIXME: handle comments foo(a /*...*/b: Int).
    size_t LocalNameStart = Content.find_last_of(" \t\n\v\f\r/");
    assert(LocalNameStart != StringRef::npos);
    if (!IsCollapsible)
      ++LocalNameStart;
    auto LocalLoc = Range.getStart().getAdvancedLocOrInvalid(LocalNameStart);
    CharSourceRange Local{LocalLoc, unsigned(Content.size() - LocalNameStart)};

    addRenameRange(Ext, RefactoringRangeKind::DeclArgumentLabel, NameIndex);
    if (IsCollapsible) {
      addRenameRange(Local, RefactoringRangeKind::ParameterName, NameIndex);
    } else {
      addRenameRange(Local, RefactoringRangeKind::NoncollapsibleParameterName,
                     NameIndex);
    }
  }
}

void RenameRangeDetailCollector::splitAndRenameCallArg(CharSourceRange Range,
                                                       size_t NameIndex) {
  // Split call argument foo([a: ]1) into argument name [a] and the remainder
  // [: ].
  StringRef Content = Range.str();
  size_t Colon = Content.find(':'); // FIXME: leading whitespace?
  if (Colon == StringRef::npos) {
    assert(Content.empty());
    addRenameRange(Range, RefactoringRangeKind::CallArgumentCombined,
                   NameIndex);
    return;
  }

  // Include any whitespace before the ':'.
  assert(Colon == Content.substr(0, Colon).size());
  Colon = Content.substr(0, Colon).rtrim().size();

  CharSourceRange Arg{Range.getStart(), unsigned(Colon)};
  addRenameRange(Arg, RefactoringRangeKind::CallArgumentLabel, NameIndex);

  auto ColonLoc = Range.getStart().getAdvancedLocOrInvalid(Colon);
  assert(ColonLoc.isValid());
  CharSourceRange Rest{ColonLoc, unsigned(Content.size() - Colon)};
  addRenameRange(Rest, RefactoringRangeKind::CallArgumentColon, NameIndex);
}

bool RenameRangeDetailCollector::labelRangeMatches(CharSourceRange Range,
                                                   LabelRangeType RangeType,
                                                   StringRef Expected) {
  if (Range.getByteLength()) {
    bool IsEscaped = false;
    CharSourceRange ExistingLabelRange =
        getLeadingIdentifierRange(Range, IsEscaped);
    StringRef ExistingLabel = ExistingLabelRange.str();
    bool IsSingleName =
        Range == ExistingLabelRange ||
        (IsEscaped && Range.getByteLength() == ExistingLabel.size() + 2);

    switch (RangeType) {
    case LabelRangeType::NoncollapsibleParam:
      if (IsSingleName && Expected.empty()) // subscript([x]: Int)
        return true;
      LLVM_FALLTHROUGH;
    case LabelRangeType::CallArg:
    case LabelRangeType::Param:
    case LabelRangeType::EnumCaseParam:
    case LabelRangeType::CompoundName:
      return ExistingLabel == (Expected.empty() ? "_" : Expected);
    case LabelRangeType::None:
      llvm_unreachable("Unhandled label range type");
    }
  }
  return Expected.empty();
}

bool RenameRangeDetailCollector::renameLabelsLenient(
    ArrayRef<CharSourceRange> LabelRanges,
    std::optional<unsigned> FirstTrailingLabel, LabelRangeType RangeType) {

  ArrayRef<StringRef> OldNames = Old.args();

  // First, match trailing closure arguments in reverse
  if (FirstTrailingLabel) {
    auto TrailingLabels = LabelRanges.drop_front(*FirstTrailingLabel);
    LabelRanges = LabelRanges.take_front(*FirstTrailingLabel);

    for (auto LabelIndex : llvm::reverse(indices(TrailingLabels))) {
      CharSourceRange Label = TrailingLabels[LabelIndex];

      if (Label.getByteLength()) {
        if (OldNames.empty())
          return true;

        while (!labelRangeMatches(Label, LabelRangeType::CompoundName,
                                  OldNames.back())) {
          if ((OldNames = OldNames.drop_back()).empty())
            return true;
        }
        splitAndRenameLabel(Label, LabelRangeType::CompoundName,
                            OldNames.size() - 1);
        OldNames = OldNames.drop_back();
        continue;
      }

      // empty labelled trailing closure label
      if (LabelIndex) {
        if (OldNames.empty())
          return true;

        while (!OldNames.back().empty()) {
          if ((OldNames = OldNames.drop_back()).empty())
            return true;
        }
        splitAndRenameLabel(Label, LabelRangeType::CompoundName,
                            OldNames.size() - 1);
        OldNames = OldNames.drop_back();
        continue;
      }

      // unlabelled trailing closure label
      OldNames = OldNames.drop_back();
      continue;
    }
  }

  // Next, match the non-trailing arguments.
  size_t NameIndex = 0;

  for (CharSourceRange Label : LabelRanges) {
    // empty label
    if (!Label.getByteLength()) {

      // first name pos
      if (!NameIndex) {
        while (!OldNames[NameIndex].empty()) {
          if (++NameIndex >= OldNames.size())
            return true;
        }
        splitAndRenameLabel(Label, RangeType, NameIndex++);
        continue;
      }

      // other name pos
      if (NameIndex >= OldNames.size() || !OldNames[NameIndex].empty()) {
        // FIXME: only allow one variadic param
        continue; // allow for variadic
      }
      splitAndRenameLabel(Label, RangeType, NameIndex++);
      continue;
    }

    // non-empty label
    if (NameIndex >= OldNames.size())
      return true;

    while (!labelRangeMatches(Label, RangeType, OldNames[NameIndex])) {
      if (++NameIndex >= OldNames.size())
        return true;
    };
    splitAndRenameLabel(Label, RangeType, NameIndex++);
  }
  return false;
}

RegionType RenameRangeDetailCollector::getSyntacticRenameRegionType(
    const ResolvedLoc &Resolved) {
  switch (Resolved.context) {
  case ResolvedLocContext::Default:
    if (Resolved.isActive) {
      return RegionType::ActiveCode;
    } else {
      return RegionType::InactiveCode;
    }
  case ResolvedLocContext::Selector:
    return RegionType::Selector;
  case ResolvedLocContext::Comment:
    return RegionType::Comment;
  case ResolvedLocContext::StringLiteral:
    return RegionType::String;
  }
}

enum class SpecialBaseName {
  /// The function does not have one of the special base names.
  None,
  Subscript,
  Init,
  CallAsFunction
};

static SpecialBaseName specialBaseNameFor(const DeclNameViewer &declName) {
  if (!declName.isFunction()) {
    return SpecialBaseName::None;
  }
  if (declName.base() == "subscript") {
    // FIXME: Don't handle as special name if it is backticked.
    return SpecialBaseName::Subscript;
  } else if (declName.base() == "init") {
    // FIXME: Don't handle as special name if it is backticked.
    return SpecialBaseName::Init;
  } else if (declName.base() == "callAsFunction") {
    // FIXME: this should only be treated specially for instance methods.
    return SpecialBaseName::CallAsFunction;
  } else {
    return SpecialBaseName::None;
  }
}

RegionType RenameRangeDetailCollector::addSyntacticRenameRanges(
    const ResolvedLoc &resolved, const RenameLoc &config) {

  if (!resolved.range.isValid())
    return RegionType::Unmatched;

  RenameLocUsage usage = config.Usage;

  auto regionKind = getSyntacticRenameRegionType(resolved);

  SpecialBaseName specialBaseName = specialBaseNameFor(Old);

  if (usage == RenameLocUsage::Unknown) {
    // Unknown name usage occurs if we don't have an entry in the index that
    // tells us whether the location is a call, reference or a definition. The
    // most common reasons why this happens is if the editor is adding syntactic
    // results to cover comments or string literals.
    //
    // We only want to include these textual matches inside comments and string
    // literals. All other matches inside are likely bogus results.
    if (regionKind != RegionType::Comment && regionKind != RegionType::String) {
      return RegionType::Unmatched;
    }

    if (specialBaseName != SpecialBaseName::None &&
        resolved.labelType == LabelRangeType::None) {
      // Filter out non-semantic special basename locations with no labels.
      // We've already filtered out those in code, so these are
      // any appearance of just 'init', 'subscript', or 'callAsFunction' in
      // strings, comments, and inactive code.
      return RegionType::Unmatched;
    }
  }

  switch (specialBaseName) {
  case SpecialBaseName::None:
    // If we don't have a special base name, we can just rename it.
    if (renameBase(resolved.range, RefactoringRangeKind::BaseName)) {
      return RegionType::Mismatch;
    }
    break;
  case SpecialBaseName::Init:
  case SpecialBaseName::CallAsFunction:
    if (renameBase(resolved.range, RefactoringRangeKind::KeywordBaseName)) {
      // The base name doesn't need to match for calls, for example because
      // an initializer can be called as `MyType()` and `callAsFunction` can
      // be called as `myStruct()`, so even if the base fails to be renamed,
      // continue.
      // But the names do need to match for definitions and references.
      if (usage == RenameLocUsage::Definition ||
          usage == RenameLocUsage::Reference) {
        return RegionType::Mismatch;
      }
    }
    break;
  case SpecialBaseName::Subscript:
    // Only try renaming the base for definitions of the subscript.
    // Accesses to the subscript are modelled as references with `[` as the
    // base name, which does not match. Subscripts are never called in the
    // index.
    if (usage == RenameLocUsage::Definition) {
      if (renameBase(resolved.range, RefactoringRangeKind::KeywordBaseName)) {
        return RegionType::Mismatch;
      }
    }
    break;
  }

  bool handleLabels = false;
  bool isCallSite = false;
  if (Old.isFunction()) {
    switch (usage) {
    case RenameLocUsage::Call:
      // All calls except for operators have argument labels that should be
      // renamed.
      handleLabels = !Lexer::isOperator(Old.base());
      isCallSite = true;
      break;
    case RenameLocUsage::Definition:
      // Don't rename labels of operators. There is a mismatch between the
      // indexer reporting all labels as `_` even if they are spelled as e.g.
      // `x: Int` in the function declaration. Since the labels only appear
      // on the operator declaration and in no calls, just don't rename them for
      // now.
      // For all other (normal) function declarations, always rename the labels.
      handleLabels = !Lexer::isOperator(Old.base());
      isCallSite = false;
      break;
    case RenameLocUsage::Reference:
      if (resolved.labelType == LabelRangeType::CompoundName) {
        // If we have a compound name that specifies argument labels to
        // disambiguate functions with the same base name, we always need to
        // rename the labels.
        handleLabels = true;
        isCallSite = false;
      } else if (specialBaseName == SpecialBaseName::Subscript) {
        // Accesses to a subscript are modeled using a reference to the
        // subscript (with base name `[`). We always need to rename argument
        // labels here.
        handleLabels = true;
        isCallSite = true;
      } else {
        handleLabels = false;
        isCallSite = false;
      }
      break;
    case RenameLocUsage::Unknown:
      // If we don't know where the function is used, fall back to trying to
      // rename labels if there are some.
      handleLabels = resolved.labelType != LabelRangeType::None;
      isCallSite = resolved.labelType == LabelRangeType::CallArg;
      break;
    }
  }

  if (handleLabels) {
    bool renameLabelsFailed =
        renameLabels(resolved.labelRanges, resolved.firstTrailingLabel,
                     resolved.labelType, isCallSite);
    if (renameLabelsFailed) {
      return usage == RenameLocUsage::Unknown ? RegionType::Unmatched
                                              : RegionType::Mismatch;
    }
  }

  return regionKind;
}

} // end anonymous namespace

SyntacticRenameRangeDetails swift::ide::getSyntacticRenameRangeDetails(
    const SourceManager &SM, StringRef OldName, const ResolvedLoc &Resolved,
    const RenameLoc &Config) {
  RenameRangeDetailCollector RangeCollector(SM, OldName);
  RegionType Type = RangeCollector.addSyntacticRenameRanges(Resolved, Config);
  return {Type, RangeCollector.takeResult()};
}