/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 * Copyright (C) 2014 Apple Inc. All rights reserved.
 * Copyright (C) 2014 Samsung Electronics. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ATTRIBUTE_COLLECTION_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ATTRIBUTE_COLLECTION_H_

#include "base/compiler_specific.h"
#include "base/containers/span.h"
#include "third_party/blink/renderer/core/dom/attribute.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/text/atomic_string_table.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

template <typename Container, typename ContainerMemberType = Container>
class AttributeCollectionGeneric {
  STACK_ALLOCATED();

 public:
  using iterator = typename Container::pointer;

  AttributeCollectionGeneric(Container& attributes) : attributes_(attributes) {}

  Container::reference operator[](unsigned index) const { return at(index); }
  Container::reference at(unsigned index) const {
    CHECK_LT(index, size());
    // SAFETY: Check above.
    return UNSAFE_BUFFERS(begin()[index]);
  }

  Container::pointer data() { return attributes_.data(); }
  Container::const_pointer data() const { return attributes_.data(); }

  Container::pointer begin() const { return attributes_.data(); }
  Container::pointer end() const {
    // SAFETY: size() describes the number of elements at data().
    // This form is used in place of end() to avoid a conflict
    // between the pointer type used as an iterator for this class,
    // and an iterator type used by containers.
    return UNSAFE_BUFFERS(begin() + size());
  }

  unsigned size() const { return static_cast<unsigned>(attributes_.size()); }
  bool IsEmpty() const { return !size(); }

  // Find() returns nullptr if the specified name is not found.
  iterator Find(const QualifiedName&) const;
  iterator Find(const AtomicString& name) const;
  wtf_size_t FindIndex(const QualifiedName&) const;
  wtf_size_t FindIndex(const AtomicString& name) const;

  // FindHinted() and FindIndexHinted() have subtle semantics.
  //
  // The |hint| is a WeakResult that represents whether or not an AtomicString
  // exists for the AttributeCollectionGeneric version of |name| which has two
  // odd quirks:
  //
  //  1) In an HTML context, the hint will be from a lookup of the ASCII
  //     lowercased version of the attribute |name| as is required by spec.
  //  2) The |hint| is a snapshot of a membership query of the
  //     AtomicStringTable from a specific point in time.
  //
  // For (1), the HTML spec says that attribute names without prefixes should
  // be lowercased before comparison. However, if an attribute is added with
  // a namespace using the *NS() attribute APIs then lookup becomes case
  // sensitive. Therefore the API require both non-lowercased |name| and a
  // lowercased |hint|.
  //
  // For (2), the caller must ensure that its logic is robust to changes in
  // the AtomicStringTable between the creation of the |hint| and its use with
  // this API. In particular, one should not modify |collection| between
  // creation of |hint| and execution of any hinted function.
  //
  // A concrete example of a valid usage pattern is:
  //
  // AtomicStringTable::WeakResult hint =
  //     AtomicStringTable::WeakFindLowercased(name);
  //   .... Mutate |AtomicStringTable| but not |collection| ....
  // collection.FindHinted(name, hint);
  //
  // Because FindHinted() is an existence check, as long as collection is not
  // mutated between the hint creation and the lookup, we know that
  //
  //  (a) If hint.IsNull(), it cannot ever be in |collection| since
  //      then the corresponding AtomicString would be found in
  //      the AtomicStringTable.
  //  (b) If !hint.IsNull() and hint is in |collection| then the table
  //      has a reference to the corresponding AtomicString meaning
  //      it will not be removed from the AtomicString.
  //  (c) If the !hint.IsNull() and it is not in |collection|, then it is
  //      possible that the underlying memory buffer for the AtomicString
  //      corresponding to the him can  be reallocated to a different string
  //      making the |hint| semantically invalid. However, because the
  //      |collection| is not mutated, |hint| will not match anything.
  Container::pointer FindHinted(const StringView& name,
                                AtomicStringTable::WeakResult hint) const;
  wtf_size_t FindIndexHinted(const StringView& name,
                             AtomicStringTable::WeakResult hint) const;

 protected:
  iterator FindWithPrefix(const StringView& name) const;

  ContainerMemberType attributes_;
};

using AttributeArray = base::span<const Attribute>;

class AttributeCollection
    : public AttributeCollectionGeneric<const AttributeArray> {
 public:
  AttributeCollection()
      : AttributeCollectionGeneric<const AttributeArray>(AttributeArray()) {}

  explicit AttributeCollection(base::span<const Attribute> attributes)
      : AttributeCollectionGeneric<const AttributeArray>(attributes) {}
};

using AttributeVector = Vector<Attribute, 4>;
class MutableAttributeCollection
    : public AttributeCollectionGeneric<AttributeVector, AttributeVector&> {
 public:
  explicit MutableAttributeCollection(AttributeVector& attributes)
      : AttributeCollectionGeneric<AttributeVector, AttributeVector&>(
            attributes) {}

  // These functions do no error/duplicate checking.
  void Append(const QualifiedName&, const AtomicString& value);
  void Remove(unsigned index);
};

inline void MutableAttributeCollection::Append(const QualifiedName& name,
                                               const AtomicString& value) {
  attributes_.push_back(Attribute(name, value));
}

inline void MutableAttributeCollection::Remove(unsigned index) {
  attributes_.EraseAt(index);
}

template <typename Container, typename ContainerMemberType>
inline typename AttributeCollectionGeneric<Container,
                                           ContainerMemberType>::iterator
AttributeCollectionGeneric<Container, ContainerMemberType>::Find(
    const AtomicString& name) const {
  return FindHinted(name, AtomicStringTable::WeakResult(name.Impl()));
}

template <typename Container, typename ContainerMemberType>
inline wtf_size_t
AttributeCollectionGeneric<Container, ContainerMemberType>::FindIndexHinted(
    const StringView& name,
    AtomicStringTable::WeakResult hint) const {
  iterator it = FindHinted(name, hint);
  return it ? wtf_size_t(it - begin()) : kNotFound;
}

template <typename Container, typename ContainerMemberType>
inline wtf_size_t
AttributeCollectionGeneric<Container, ContainerMemberType>::FindIndex(
    const QualifiedName& name) const {
  for (wtf_size_t index = 0; index < size(); ++index) {
    if (at(index).GetName().Matches(name)) {
      return index;
    }
  }
  return kNotFound;
}

template <typename Container, typename ContainerMemberType>
inline wtf_size_t
AttributeCollectionGeneric<Container, ContainerMemberType>::FindIndex(
    const AtomicString& name) const {
  return FindIndexHinted(name, AtomicStringTable::WeakResult(name.Impl()));
}

template <typename Container, typename ContainerMemberType>
inline typename AttributeCollectionGeneric<Container,
                                           ContainerMemberType>::iterator
AttributeCollectionGeneric<Container, ContainerMemberType>::FindHinted(
    const StringView& name,
    AtomicStringTable::WeakResult hint) const {
  // A slow check is required if there are any attributes with prefixes
  // and no unprefixed name matches.
  bool has_attributes_with_prefixes = false;

  // Optimize for the case where the attribute exists and its name exactly
  // matches.
  for (unsigned index = 0; index < size(); ++index) {
    // FIXME: Why check the prefix? Namespaces should be all that matter.
    // Most attributes (all of HTML and CSS) have no namespace.
    auto& item = at(index);
    if (!item.GetName().HasPrefix()) {
      if (hint == item.LocalName()) {
        return &item;
      }
    } else {
      has_attributes_with_prefixes = true;
    }
  }

  // Note that if the attribute has a prefix, the match has to be case
  // sensitive therefore |name| must be used.
  if (has_attributes_with_prefixes)
    return FindWithPrefix(name);
  return nullptr;
}

template <typename Container, typename ContainerMemberType>
inline typename AttributeCollectionGeneric<Container,
                                           ContainerMemberType>::iterator
AttributeCollectionGeneric<Container, ContainerMemberType>::Find(
    const QualifiedName& name) const {
  for (unsigned index = 0; index < size(); ++index) {
    auto& item = at(index);
    if (item.GetName().Matches(name)) {
      return &item;
    }
  }
  return nullptr;
}

template <typename Container, typename ContainerMemberType>
typename AttributeCollectionGeneric<Container, ContainerMemberType>::iterator
AttributeCollectionGeneric<Container, ContainerMemberType>::FindWithPrefix(
    const StringView& name) const {
  // Check all attributes with prefixes. This is a case sensitive check.
  // Attributes with empty prefixes are expected to be handled outside this
  // function.
  for (unsigned index = 0; index < size(); ++index) {
    auto& item = at(index);
    if (!item.GetName().HasPrefix()) {
      // Skip attributes with no prefixes because they must be checked in
      // FindIndex(const AtomicString&).
      DCHECK(!(name == item.LocalName()));
    } else {
      // `name` equals "prefix:localName"; compare it piece by piece instead of
      // building that temporary string via QualifiedName::ToString().
      const AtomicString& prefix = item.Prefix();
      const AtomicString& local_name = item.LocalName();
      if (name.length() == prefix.length() + 1 + local_name.length() &&
          name.substr(0, prefix.length()) == prefix &&
          name.substr(prefix.length()).starts_with(':') &&
          name.substr(prefix.length() + 1) == local_name) {
        return &item;
      }
    }
  }
  return nullptr;
}

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ATTRIBUTE_COLLECTION_H_