// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <algorithm>

#include "base/format_macros.h"
#include "base/logging.h"
#include "base/strings/stringprintf.h"
#include "net/http/http_byte_range.h"

namespace {

const int64 kPositionNotSpecified = -1;

}  // namespace

namespace net {

HttpByteRange::HttpByteRange()
    : first_byte_position_(kPositionNotSpecified),
      last_byte_position_(kPositionNotSpecified),
      suffix_length_(kPositionNotSpecified),
      has_computed_bounds_(false) {
}

// static
HttpByteRange HttpByteRange::Bounded(int64 first_byte_position,
                                     int64 last_byte_position) {
  HttpByteRange range;
  range.set_first_byte_position(first_byte_position);
  range.set_last_byte_position(last_byte_position);
  return range;
}

// static
HttpByteRange HttpByteRange::RightUnbounded(int64 first_byte_position) {
  HttpByteRange range;
  range.set_first_byte_position(first_byte_position);
  return range;
}

// static
HttpByteRange HttpByteRange::Suffix(int64 suffix_length) {
  HttpByteRange range;
  range.set_suffix_length(suffix_length);
  return range;
}

bool HttpByteRange::IsSuffixByteRange() const {
  return suffix_length_ != kPositionNotSpecified;
}

bool HttpByteRange::HasFirstBytePosition() const {
  return first_byte_position_ != kPositionNotSpecified;
}

bool HttpByteRange::HasLastBytePosition() const {
  return last_byte_position_ != kPositionNotSpecified;
}

bool HttpByteRange::IsValid() const {
  if (suffix_length_ > 0)
    return true;
  return (first_byte_position_ >= 0 &&
          (last_byte_position_ == kPositionNotSpecified ||
           last_byte_position_ >= first_byte_position_));
}

std::string HttpByteRange::GetHeaderValue() const {
  DCHECK(IsValid());

  if (IsSuffixByteRange())
    return base::StringPrintf("bytes=-%" PRId64, suffix_length());

  DCHECK(HasFirstBytePosition());

  if (!HasLastBytePosition())
    return base::StringPrintf("bytes=%" PRId64 "-", first_byte_position());

  return base::StringPrintf("bytes=%" PRId64 "-%" PRId64,
                            first_byte_position(), last_byte_position());
}

bool HttpByteRange::ComputeBounds(int64 size) {
  if (size < 0)
    return false;
  if (has_computed_bounds_)
    return false;
  has_computed_bounds_ = true;

  // Empty values.
  if (!HasFirstBytePosition() &&
      !HasLastBytePosition() &&
      !IsSuffixByteRange()) {
    first_byte_position_ = 0;
    last_byte_position_ = size - 1;
    return true;
  }
  if (!IsValid())
    return false;
  if (IsSuffixByteRange()) {
    first_byte_position_ = size - std::min(size, suffix_length_);
    last_byte_position_ = size - 1;
    return true;
  }
  if (first_byte_position_ < size) {
    if (HasLastBytePosition())
      last_byte_position_ = std::min(size - 1, last_byte_position_);
    else
      last_byte_position_ = size - 1;
    return true;
  }
  return false;
}

}  // namespace net