// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_RANGE_RANGE_H_
#define UI_GFX_RANGE_RANGE_H_

#include <stddef.h>
#include <stdint.h>

#include <algorithm>
#include <iosfwd>
#include <limits>
#include <string>
#include <vector>

#include "base/numerics/safe_conversions.h"
#include "build/build_config.h"
#include "ui/gfx/range/gfx_range_export.h"

#if BUILDFLAG(IS_APPLE)
#if __OBJC__
#import <Foundation/Foundation.h>
#else
typedef struct _NSRange NSRange;
#endif
#endif  // BUILDFLAG(IS_APPLE)

namespace gfx {

// This class represents either a forward range [min, max) or a reverse range
// (max, min]. |start_| is always the first of these and |end_| the second; as a
// result, the range is forward if (start_ <= end_).  The zero-width range
// [val, val) is legal, contains and intersects itself, and is contained by and
// intersects any nonempty range [min, max) where min <= val < max.
class GFX_RANGE_EXPORT Range {
 public:
  // Creates an empty range {0,0}.
  constexpr Range() : Range(0) {}

  // Initializes the range with a start and end.
  constexpr Range(size_t start, size_t end)
      : start_(base::checked_cast<uint32_t>(start)),
        end_(base::checked_cast<uint32_t>(end)) {}

  // Initializes the range with the same start and end positions.
  constexpr explicit Range(size_t position) : Range(position, position) {}

  // Platform constructors.
#if BUILDFLAG(IS_APPLE)
  // Constructs a Range from a NSRange.
  // CHECKs if NSRange is out of the maximum bound of Range.
  explicit Range(const NSRange& range);
  // Constructs a Range from a NSRange.
  // Returns InvalidRange() if NSRange is out of the maximum bound of Range.
  static Range FromPossiblyInvalidNSRange(const NSRange& range);
#endif

  // Returns a range that is invalid, which is {UINT32_MAX,UINT32_MAX}.
  static constexpr Range InvalidRange() {
    return Range(std::numeric_limits<uint32_t>::max());
  }

  // Checks if the range is valid through comparison to InvalidRange().  If this
  // is not valid, you must not call start()/end().
  constexpr bool IsValid() const { return *this != InvalidRange(); }

  // Ensures that the direction of this range matches the direction of the
  // provided range, reversing this range if necessary. Returns a reference to
  // `this` to allow method chaining.
  Range& MatchDirection(const Range& other) {
    if (is_reversed() != other.is_reversed()) {
      std::swap(start_, end_);
    }
    return *this;
  }

  // Getters and setters.
  constexpr size_t start() const { return start_; }
  void set_start(size_t start) { start_ = base::checked_cast<uint32_t>(start); }

  constexpr size_t end() const { return end_; }
  void set_end(size_t end) { end_ = base::checked_cast<uint32_t>(end); }

  // Returns the absolute value of the length.
  constexpr size_t length() const { return GetMax() - GetMin(); }

  constexpr bool is_reversed() const { return start() > end(); }
  constexpr bool is_empty() const { return start() == end(); }

  // Returns the minimum and maximum values.
  constexpr size_t GetMin() const {
    return start() < end() ? start() : end();
  }
  constexpr size_t GetMax() const {
    return start() > end() ? start() : end();
  }

  constexpr bool operator==(const Range& other) const = default;
  constexpr auto operator<=>(const Range& other) const = default;
  constexpr bool EqualsIgnoringDirection(const Range& other) const {
    return GetMin() == other.GetMin() && GetMax() == other.GetMax();
  }

  // Returns true if this range intersects the specified |range|.
  constexpr bool Intersects(const Range& range) const {
    return Intersect(range).IsValid();
  }

  // Returns true if this range contains the specified |range|.
  constexpr bool Contains(const Range& range) const {
    return range.IsBoundedBy(*this) &&
           // A non-empty range doesn't contain the range [max, max).
           (range.GetMax() != GetMax() || range.is_empty() == is_empty());
  }

  // Returns true if this range is contained by the specified |range| or it is
  // an empty range and ending the range |range|.
  constexpr bool IsBoundedBy(const Range& range) const {
    return IsValid() && range.IsValid() && GetMin() >= range.GetMin() &&
           GetMax() <= range.GetMax();
  }

  // Computes the intersection of this range with the given |range|.
  // If they don't intersect, it returns an InvalidRange().
  // The returned range is always empty or forward (never reversed).
  constexpr Range Intersect(const Range& range) const {
    const size_t min = std::max(GetMin(), range.GetMin());
    const size_t max = std::min(GetMax(), range.GetMax());
    return (min < max || Contains(range) || range.Contains(*this))
               ? Range(min, max)
               : InvalidRange();
  }

#if BUILDFLAG(IS_APPLE)
  // Constructs a Range from a NSRange.
  // CHECKs if NSRange is out of the maximum bound of Range.
  Range& operator=(const NSRange& range);

  // NSRange does not store the directionality of a range, so if this
  // is_reversed(), the range will get flipped when converted to an NSRange.
  NSRange ToNSRange() const;
#endif
  // GTK+ has no concept of a range.

  std::string ToString() const;

  // In many cases we use gfx::Range to represent a contiguous range of int
  // indices. However, the underlying type stored in a range is uint32_t, which
  // may exceed the size of int. This function CHECKs that the range does not
  // exceed int limits before doing the conversion.
  std::vector<int> ToIntVector() const;

 private:
  // Note: we use uint32_t instead of size_t because this struct is sent over
  // IPC which could span 32 & 64 bit processes.
  uint32_t start_;
  uint32_t end_;
};

GFX_RANGE_EXPORT std::ostream& operator<<(std::ostream& os, const Range& range);

}  // namespace gfx

#endif  // UI_GFX_RANGE_RANGE_H_