// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SERVICES_NETWORK_PUBLIC_CPP_IP_ADDRESS_SPACE_UTIL_H_
#define SERVICES_NETWORK_PUBLIC_CPP_IP_ADDRESS_SPACE_UTIL_H_

#include <optional>
#include <string_view>
#include <vector>

#include "base/component_export.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/stack_allocated.h"
#include "base/no_destructor.h"
#include "base/synchronization/lock.h"
#include "net/base/ip_address.h"
#include "net/base/ip_endpoint.h"
#include "services/network/public/mojom/ip_address_space.mojom-forward.h"
#include "services/network/public/mojom/parsed_headers.mojom-forward.h"
#include "services/network/public/mojom/url_loader_network_service_observer.mojom-forward.h"

class GURL;

namespace net {

struct TransportInfo;

}  // namespace net

namespace network {

// Returns true if `str` represents a valid IP address space override, as
// described in services/network/public/cpp/network_switches.cc
bool COMPONENT_EXPORT(NETWORK_CPP)
    IsAddressSpaceOverrideValid(std::string_view str);

// Returns a human-readable string representing `result`, suitable for logging.
std::string_view COMPONENT_EXPORT(NETWORK_CPP)
    LocalNetworkAccessResultToStringPiece(
        mojom::LocalNetworkAccessResult result);

// Returns a human-readable string representing `transport_type`, suitable for
// logging.
std::string_view COMPONENT_EXPORT(NETWORK_CPP)
    TransportTypeToStringPiece(mojom::TransportType transport_type);

// Returns a human-readable string representing `space`, suitable for logging.
std::string_view COMPONENT_EXPORT(NETWORK_CPP)
    IPAddressSpaceToStringPiece(mojom::IPAddressSpace space);

// Returns the `IPAddressSpace` to which `address` belongs.
// Returns `kUnknown` for invalid IP addresses.
//
// WARNING: Most callers will want to use `TransportInfoToIPAddressSpace()`
// below instead, as this does not properly account for proxies nor for
// command-line overrides.
mojom::IPAddressSpace COMPONENT_EXPORT(NETWORK_CPP)
    IPAddressToIPAddressSpace(const net::IPAddress& address);

// Returns the `IPAddressSpace` to which `endpoint` belongs.
// Returns `kUnknown` for invalid IP addresses.
//
// WARNING: Most callers will want to use `TransportInfoToIPAddressSpace()`
// below instead, as this does not properly account for proxies. It does account
// for command-line overrides though.
mojom::IPAddressSpace COMPONENT_EXPORT(NETWORK_CPP)
    IPEndPointToIPAddressSpace(const net::IPEndPoint& endpoint);

// Returns the `IPAddressSpace` to which the endpoint of `transport` belongs.
//
// When the transport is a proxied connection, returns `kUnknown`. See
// https://github.com/WICG/private-network-access/issues/62 for more details on
// the reasoning there.
//
// When the transport is a direct connection, returns the IP address space of
// `info.endpoint`. This returns `kUnknown` for invalid IP addresses. Otherwise,
// takes into account the `--ip-address-space-overrides` command-line switch. If
// no override applies, then follows this algorithm:
// https://wicg.github.io/local-network-access/#determine-the-ip-address-space
//
// `info.endpoint`'s port is only used for matching to command-line overrides.
// It is ignored otherwise. In particular, if no overrides are specified on the
// command-line, then this function ignores the port entirely.
//
// WARNING: This can only be used as-is for subresource requests loaded over the
// network. Special URL schemes and resource headers must also be taken into
// account at higher layers.
mojom::IPAddressSpace COMPONENT_EXPORT(NETWORK_CPP)
    TransportInfoToIPAddressSpace(const net::TransportInfo& info);

// Returns whether `lhs` is less public than `rhs`.
//
// This comparator is compatible with std::less.
//
// Address spaces go from most public to least public in the following order:
//
//  - public and unknown (equivalent)
//  - local
//  - loopback
//
bool COMPONENT_EXPORT(NETWORK_CPP)
    IsLessPublicAddressSpace(mojom::IPAddressSpace lhs,
                             mojom::IPAddressSpace rhs);

// Returns whether `lhs` is less public than `rhs`, but collapses the local
// and loopback address spaces into the same bucket.
//
// This comparator is compatible with std::less.
//
// Address spaces go from most public to least public in the following order:
//
//  - public and unknown (equivalent)
//  - local and loopback (equivalent)
//
bool COMPONENT_EXPORT(NETWORK_CPP)
    IsLessPublicAddressSpaceLNA(mojom::IPAddressSpace lhs,
                                mojom::IPAddressSpace rhs);

// Represents optional parameters of CalculateClientAddressSpace().
// This is effectively a subset of network::mojom::URLResponseHead.
// WARNING: This struct just keeps references to parameters and does not own
// them nor make copy of them. Parameters must outlive this struct. For example,
// passing net::IPEndPoint() as `remote_endpoint` is invalid.
struct COMPONENT_EXPORT(NETWORK_CPP) CalculateClientAddressSpaceParams {
  STACK_ALLOCATED();

 public:
  ~CalculateClientAddressSpaceParams();

  const std::optional<mojom::IPAddressSpace>
      client_address_space_inherited_from_service_worker;
  const raw_ptr<const mojom::ParsedHeadersPtr> parsed_headers;
  const raw_ptr<const net::IPEndPoint> remote_endpoint;
};

// Given a request URL and `params`, this function calculates the
// IPAddressSpace which should be associated with documents or worker global
// scopes (collectively: request clients) instantiated from this resource.
//
// `params` is optional. If `params` contain values, values must be valid and
// `params.value().parsed_headers` must be populated with the result of
// parsing the corresponding response headers.
//
// WARNING: This function is defined here for proximity with related code and
// the data structures involved. However since it deals with higher-level
// concepts too (documents and worker global scopes), it should probably only be
// used at the content/ layer or above.
//
// See: https://wicg.github.io/local-network-access/#ip-address-space-section
mojom::IPAddressSpace COMPONENT_EXPORT(NETWORK_CPP) CalculateClientAddressSpace(
    const GURL& url,
    std::optional<CalculateClientAddressSpaceParams> params);

// Given a response URL and the IP endpoint the requested resource was fetched
// from, this function calculates the IPAddressSpace of the requested resource.
//
// As opposed to CalculateClientAddressSpace(), this function is used to
// determine the address space of the *target* of a fetch, for comparison with
// that of the client of the fetch.
//
// See: https://wicg.github.io/local-network-access/#integration-with-fetch
mojom::IPAddressSpace COMPONENT_EXPORT(NETWORK_CPP)
    CalculateResourceAddressSpace(const GURL& url,
                                  const net::IPEndPoint& endpoint);


// Return the IP address space of the host if we can determine it from the URL,
// otherwise returns std::nullopt.
//
// Cases in which we can determine the IP address space:
//
// * host is an IP address literal
// * host is a .local domain (e.g. RFC6762), or 'local'/'local.'
// * host is 'localhost', 'localhost.' (or a .localhost domain).
//
// This function will apply IP address space overrides.
std::optional<mojom::IPAddressSpace> COMPONENT_EXPORT(NETWORK_CPP)
    GetAddressSpaceFromUrl(const GURL& url);

class COMPONENT_EXPORT(NETWORK_CPP) IPAddressSpaceOverrides {
 public:
  static IPAddressSpaceOverrides& GetInstance();

  ~IPAddressSpaceOverrides() = delete;
  IPAddressSpaceOverrides(const IPAddressSpaceOverrides&) = delete;
  IPAddressSpaceOverrides& operator=(const IPAddressSpaceOverrides&) = delete;

  struct CIDR {
    net::IPAddress ip_address;
    size_t mask_bits;
  };

  // Represents a single command-line-specified override. Exactly one of
  // endpoint or cidr should be specified.
  struct AddressSpaceOverride {
    AddressSpaceOverride();
    ~AddressSpaceOverride();
    AddressSpaceOverride(const AddressSpaceOverride&);
    AddressSpaceOverride& operator=(const AddressSpaceOverride& other);
    AddressSpaceOverride(AddressSpaceOverride&&);
    AddressSpaceOverride& operator=(AddressSpaceOverride&& other);

    // The IP endpoint to override the address space for, if present.
    std::optional<net::IPEndPoint> endpoint;
    // The CIDR range to override the address space for, if present.
    std::optional<CIDR> cidr;

    // The IP address space to which `endpoint` should be mapped.
    mojom::IPAddressSpace space;
  };

  // Checks to see if there is an IP Address Space override for the given
  // endpoint, and if so, returns it. Returns std::nullopt if there is no
  // override. Overrides are checked in-order (with command-line overrides
  // being checked first), first override that matches wins.
  //
  // This method is safe to be called from any thread.
  std::optional<mojom::IPAddressSpace> HasOverride(
      const net::IPEndPoint& endpoint);

  // Returns the current overrides, combining 1) the
  // --ip-address-space-overrides command-line parameter, 2) the
  // argument passed to SetAuxiliaryOverrides (which is generally the value
  // taken from the enterprise policy).
  //
  // This method is safe to be called from any thread.
  std::vector<std::string> GetCurrentOverrides();

  // Allows setting overrides from an additional source (e.g. from an enterprise
  // policy).
  //
  // Overrides will be parsed, and any overrides that fail validation will be
  // appended to the optional |rejected_overrides| output parameter.
  //
  // This method is safe to be called from any thread.
  void SetAuxiliaryOverrides(const std::string& auxiliary_overrides,
                             std::vector<std::string>* rejected_overrides);

  // Empties the overrides list.
  //
  // This function is safe to be called from any thread.
  void ResetForTesting();

 private:
  friend class base::NoDestructor<IPAddressSpaceOverrides>;
  IPAddressSpaceOverrides();

  void ParseCmdlineIfNeeded() EXCLUSIVE_LOCKS_REQUIRED(lock_);

  base::Lock lock_;

  bool has_cmdline_been_parsed_ GUARDED_BY(lock_) = false;
  std::vector<std::string> cmdline_overrides_ GUARDED_BY(lock_);
  std::vector<AddressSpaceOverride> parsed_cmdline_overrides_ GUARDED_BY(lock_);

  std::vector<std::string> auxiliary_overrides_ GUARDED_BY(lock_);
  std::vector<AddressSpaceOverride> parsed_auxiliary_overrides_
      GUARDED_BY(lock_);
};

}  // namespace network

#endif  // SERVICES_NETWORK_PUBLIC_CPP_IP_ADDRESS_SPACE_UTIL_H_