// Copyright (c) 2012 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.

#ifndef NET_DNS_DNS_UTIL_H_
#define NET_DNS_DNS_UTIL_H_

#include <string>
#include <vector>

#include "base/strings/string_piece.h"
#include "base/time/time.h"
#include "net/base/address_family.h"
#include "net/base/ip_endpoint.h"
#include "net/base/net_export.h"
#include "net/base/network_change_notifier.h"
#include "net/dns/dns_config.h"
#include "net/dns/public/dns_over_https_server_config.h"
#include "net/dns/public/dns_query_type.h"

namespace net {

class AddressList;

// DNSDomainFromDot - convert a domain string to DNS format. From DJB's
// public domain DNS library. |dotted| may include only characters a-z, A-Z,
// 0-9, -, and _.
//
//   dotted: a string in dotted form: "www.google.com"
//   out: a result in DNS form: "\x03www\x06google\x03com\x00"
NET_EXPORT bool DNSDomainFromDot(const base::StringPiece& dotted,
                                 std::string* out);

// DNSDomainFromUnrestrictedDot - convert a domain string to DNS format. Adapted
// from DJB's public domain DNS library. No validation of the characters in
// |dotted| is performed.
//
//   dotted: a string in dotted form: "Foo Printer._tcp.local"
//   out: a result in DNS form: "\x0bFoo Printer\x04_tcp\x05local\x00"
NET_EXPORT bool DNSDomainFromUnrestrictedDot(const base::StringPiece& dotted,
                                             std::string* out);

// Checks that a hostname is valid. Simple wrapper around DNSDomainFromDot.
NET_EXPORT_PRIVATE bool IsValidDNSDomain(const base::StringPiece& dotted);

// Checks that a hostname is valid. Simple wrapper around
// DNSDomainFromUnrestrictedDot.
NET_EXPORT_PRIVATE bool IsValidUnrestrictedDNSDomain(
    const base::StringPiece& dotted);

// Returns true if the character is valid in a DNS hostname label, whether in
// the first position or later in the label.
//
// This function asserts a looser form of the restrictions in RFC 7719 (section
// 2; https://tools.ietf.org/html/rfc7719#section-2): hostnames can include
// characters a-z, A-Z, 0-9, -, and _, and any of those characters (except -)
// are legal in the first position. The looser rules are necessary to support
// service records (initial _), and non-compliant but attested hostnames that
// include _. These looser rules also allow Punycode and hence IDN.
//
// TODO(palmer): In the future, when we can remove support for invalid names,
// this can be a private implementation detail of |DNSDomainFromDot|, and need
// not be NET_EXPORT_PRIVATE.
NET_EXPORT_PRIVATE bool IsValidHostLabelCharacter(char c, bool is_first_char);

// DNSDomainToString converts a domain in DNS format to a dotted string.
// Excludes the dot at the end.
NET_EXPORT std::string DNSDomainToString(const base::StringPiece& domain);

// Return the expanded template when no variables have corresponding values.
NET_EXPORT_PRIVATE std::string GetURLFromTemplateWithoutParameters(
    const std::string& server_template);

#if !defined(OS_NACL)
NET_EXPORT_PRIVATE
base::TimeDelta GetTimeDeltaForConnectionTypeFromFieldTrialOrDefault(
    const char* field_trial_name,
    base::TimeDelta default_delta,
    NetworkChangeNotifier::ConnectionType connection_type);
#endif  // !defined(OS_NACL)

// How similar or different two AddressLists are (see values for details).
// Used in histograms; do not modify existing values.
enum AddressListDeltaType {
  // Both lists contain the same addresses in the same order.
  DELTA_IDENTICAL = 0,
  // Both lists contain the same addresses in a different order.
  DELTA_REORDERED = 1,
  // The two lists have at least one address in common, but not all of them.
  DELTA_OVERLAP = 2,
  // The two lists have no addresses in common.
  DELTA_DISJOINT = 3,
  MAX_DELTA_TYPE
};

// Compares two AddressLists to see how similar or different their addresses
// are. (See |AddressListDeltaType| for details of exactly what's checked.)
NET_EXPORT
AddressListDeltaType FindAddressListDeltaType(const AddressList& a,
                                              const AddressList& b);

// Creates a 2-byte string that represents the name pointer defined in Section
// 4.1.1 of RFC 1035 for the given offset. The first two bits in the first byte
// of the name pointer are ones, and the rest 14 bits are given to |offset|,
// which specifies an offset from the start of the message for the pointed name.
// Note that |offset| must be less than 2^14 - 1 by definition.
NET_EXPORT std::string CreateNamePointer(uint16_t offset);

// Convert a DnsQueryType enum to the wire format integer representation.
NET_EXPORT_PRIVATE uint16_t DnsQueryTypeToQtype(DnsQueryType dns_query_type);

NET_EXPORT DnsQueryType
AddressFamilyToDnsQueryType(AddressFamily address_family);

// Uses the hardcoded upgrade mapping to discover DoH service(s) associated
// with a DoT hostname. Providers listed in |excluded_providers| are not
// eligible for upgrade.
NET_EXPORT_PRIVATE std::vector<DnsOverHttpsServerConfig>
GetDohUpgradeServersFromDotHostname(
    const std::string& dot_server,
    const std::vector<std::string>& excluded_providers);

// Uses the hardcoded upgrade mapping to discover DoH service(s) associated
// with a list of insecure DNS servers. Server ordering is preserved across
// the mapping. Providers listed in |excluded_providers| are not
// eligible for upgrade.
NET_EXPORT_PRIVATE std::vector<DnsOverHttpsServerConfig>
GetDohUpgradeServersFromNameservers(
    const std::vector<IPEndPoint>& dns_servers,
    const std::vector<std::string>& excluded_providers);

// Returns the provider id to use in UMA histogram names. If there is no
// provider id that matches |doh_server|, returns "Other".
NET_EXPORT_PRIVATE std::string GetDohProviderIdForHistogramFromDohConfig(
    const DnsOverHttpsServerConfig& doh_server);

// Returns the provider id to use in UMA histogram names. If there is no
// provider id that matches |nameserver|, returns "Other".
NET_EXPORT_PRIVATE std::string GetDohProviderIdForHistogramFromNameserver(
    const IPEndPoint& nameserver);

NET_EXPORT_PRIVATE std::string SecureDnsModeToString(
    const DnsConfig::SecureDnsMode secure_dns_mode);

}  // namespace net

#endif  // NET_DNS_DNS_UTIL_H_