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

// clang-format off
#include <Weave/DeviceLayer/internal/WeaveDeviceLayerInternal.h>
#include <Weave/DeviceLayer/ConnectivityManager.h>
#include <Weave/DeviceLayer/ThreadStackManager.h>
#include <Warm/Warm.h>
// clang-format on

#include <fuchsia/net/cpp/fidl.h>
#include <fuchsia/net/interfaces/cpp/fidl.h>
#include <fuchsia/netstack/cpp/fidl.h>
#include <lib/syslog/cpp/macros.h>
#include <netinet/ip6.h>

#include <optional>

// ==================== WARM Platform Functions ====================

namespace nl {
namespace Weave {
namespace Warm {
namespace Platform {

namespace {
using DeviceLayer::ConnectivityMgrImpl;
using DeviceLayer::ThreadStackMgrImpl;

// Fixed name for tunnel interface.
constexpr char kTunInterfaceName[] = "weav-tun0";

// Prefix length for Thread addresses.
constexpr uint8_t kThreadPrefixLength = 64;

// Route metric values for primary and backup tunnels. Higher priority tunnels
// have lower metric values so that they are prioritized in the routing table.
constexpr uint32_t kRouteMetric_HighPriority = 0;
constexpr uint32_t kRouteMetric_MediumPriority = 99;
constexpr uint32_t kRouteMetric_LowPriority = 999;

// Returns the interface name associated with the given interface type.
// Unsupported interface types will not populate the optional.
std::optional<std::string> GetInterfaceName(InterfaceType interface_type) {
  switch (interface_type) {
    case kInterfaceTypeThread:
      return ThreadStackMgrImpl().GetInterfaceName();
    case kInterfaceTypeTunnel:
      return kTunInterfaceName;
    case kInterfaceTypeWiFi:
      return ConnectivityMgrImpl().GetWiFiInterfaceName();
    default:
      FX_LOGS(ERROR) << "Unknown interface type: " << interface_type;
      return std::nullopt;
  }
}

// Returns whether IPv6 forwarding is allowed for the given interface type.
bool ShouldEnableV6Forwarding(InterfaceType interface_type) {
  return (interface_type == kInterfaceTypeThread) || (interface_type == kInterfaceTypeTunnel);
}

// Returns the interface id associated with the given interface name. On
// failures to fetch the list, no value will be returned. When the interface
// does not exist, the interface ID '0' will be returned (it is guaranteed by
// the networking stack that all valid interface IDs are positive).
std::optional<uint64_t> GetInterfaceId(std::string interface_name) {
  fuchsia::net::interfaces::StateSyncPtr state_sync_ptr;
  fuchsia::net::interfaces::WatcherOptions options;
  fuchsia::net::interfaces::WatcherSyncPtr watcher_sync_ptr;

  auto svc = nl::Weave::DeviceLayer::PlatformMgrImpl().GetComponentContextForProcess()->svc();
  zx_status_t status = svc->Connect(state_sync_ptr.NewRequest());
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to bind state protocol: " << zx_status_get_string(status);
    return std::nullopt;
  }

  state_sync_ptr->GetWatcher(std::move(options), watcher_sync_ptr.NewRequest());
  if (!watcher_sync_ptr.is_bound()) {
    FX_LOGS(ERROR) << "Failed to bind watcher.";
    return std::nullopt;
  }

  fuchsia::net::interfaces::Event event;
  do {
    status = watcher_sync_ptr->Watch(&event);
    if (status != ZX_OK) {
      FX_LOGS(ERROR) << "Failed to watch for interface event: " << zx_status_get_string(status);
      return std::nullopt;
    }
    // If the entry is not of type `existing`, it is not part of the initial
    // list of interfaces that was present when the channel was initialized.
    if (!event.is_existing()) {
      continue;
    }
    // Check if the event matches the provided interface name and if so, return
    // the interface ID.
    if (event.existing().name() == interface_name) {
      return event.existing().id();
    }
  } while (!event.is_idle());
  return 0;
}

// Add or remove an address attached to the Thread or WLAN interfaces.
PlatformResult AddRemoveAddressInternal(InterfaceType interface_type,
                                        const Inet::IPAddress &address, uint8_t prefix_length,
                                        bool add) {
  auto svc = nl::Weave::DeviceLayer::PlatformMgrImpl().GetComponentContextForProcess()->svc();

  // Determine interface name to add/remove from.
  std::optional<std::string> interface_name = GetInterfaceName(interface_type);
  if (!interface_name) {
    return kPlatformResultFailure;
  }

  fuchsia::netstack::NetstackSyncPtr stack_sync_ptr;
  zx_status_t status = svc->Connect(stack_sync_ptr.NewRequest());
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to connect to netstack: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  }

  // Determine the interface ID to add/remove from.
  std::optional<uint64_t> interface_id = GetInterfaceId(interface_name.value());
  if (!add && interface_id && interface_id.value() == 0) {
    // When removing, don't report an error if the interface wasn't found. The
    // interface may already have been removed at this point.
    FX_LOGS(INFO) << "Interface " << interface_name.value() << " has already been removed.";
    return kPlatformResultSuccess;
  } else if (!interface_id) {
    return kPlatformResultFailure;
  }

  // Construct the IP address for the interface.
  fuchsia::net::IpAddress ip_addr;
  fuchsia::net::Ipv6Address ipv6_addr;

  std::memcpy(ipv6_addr.addr.data(), (uint8_t *)(address.Addr), ipv6_addr.addr.size());
  ip_addr.set_ipv6(ipv6_addr);

  // Add or remove the address from the interface.
  fuchsia::netstack::NetErr result;
  status = add ? stack_sync_ptr->SetInterfaceAddress(interface_id.value(), std::move(ip_addr),
                                                     prefix_length, &result)
               : stack_sync_ptr->RemoveInterfaceAddress(interface_id.value(), std::move(ip_addr),
                                                        prefix_length, &result);
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to configure interface address to interface id "
                   << interface_id.value() << ": " << zx_status_get_string(status);
    return kPlatformResultFailure;
  } else if (result.status == fuchsia::netstack::Status::UNKNOWN_ERROR) {
    FX_LOGS(INFO) << "Interface address already configured on interface id "
                  << interface_id.value();
    return kPlatformResultSuccess;
  } else if (result.status != fuchsia::netstack::Status::OK) {
    FX_LOGS(ERROR) << "Unable to configure interface address to interface id "
                   << interface_id.value() << ": " << result.message;
    return kPlatformResultFailure;
  }

  FX_LOGS(INFO) << (add ? "Added" : "Removed") << " address from interface id "
                << interface_id.value();

  // If this is not a Thread interface, adding the host address is sufficient.
  // Otherwise, move onto register the on-mesh prefix.
  if (interface_type != InterfaceType::kInterfaceTypeThread) {
    return kPlatformResultSuccess;
  }

  fuchsia::lowpan::device::LookupSyncPtr device_lookup;
  fuchsia::lowpan::device::Lookup_LookupDevice_Result device_lookup_result;
  fuchsia::lowpan::device::Protocols device_protocols;
  fuchsia::lowpan::device::DeviceRouteSyncPtr route_sync_ptr;

  status = svc->Connect(device_lookup.NewRequest());
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to connect to lowpan service: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  }

  device_protocols.set_device_route(route_sync_ptr.NewRequest());
  status = device_lookup->LookupDevice(interface_name.value(), std::move(device_protocols),
                                       &device_lookup_result);
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to lookup device: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  } else if (device_lookup_result.is_err()) {
    FX_LOGS(ERROR) << "Failed during lookup: " << static_cast<uint32_t>(device_lookup_result.err());
    return kPlatformResultFailure;
  }

  fuchsia::lowpan::Ipv6Subnet mesh_prefix_subnet;
  std::memcpy(mesh_prefix_subnet.addr.addr.data(), (uint8_t *)(address.Addr),
              mesh_prefix_subnet.addr.addr.size());
  mesh_prefix_subnet.prefix_len = prefix_length;

  fuchsia::lowpan::device::OnMeshPrefix mesh_prefix;
  mesh_prefix.set_subnet(mesh_prefix_subnet);
  mesh_prefix.set_default_route_preference(fuchsia::lowpan::device::RoutePreference::MEDIUM);
  mesh_prefix.set_stable(true);
  mesh_prefix.set_slaac_preferred(true);
  mesh_prefix.set_slaac_valid(true);

  status = add ? route_sync_ptr->RegisterOnMeshPrefix(std::move(mesh_prefix))
               : route_sync_ptr->UnregisterOnMeshPrefix(mesh_prefix.subnet());
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to " << (add ? "register" : "unregister") << " on-mesh prefix.";
    return kPlatformResultFailure;
  }

  FX_LOGS(INFO) << (add ? "Registered" : "Unregistered") << " on-mesh prefix for Thread.";
  return kPlatformResultSuccess;
}

// Add or remove route to/from forwarding table.
PlatformResult AddRemoveRouteInternal(InterfaceType interface_type, const Inet::IPPrefix &prefix,
                                      RoutePriority priority, bool add) {
  auto svc = nl::Weave::DeviceLayer::PlatformMgrImpl().GetComponentContextForProcess()->svc();

  // Determine interface name to add to/remove from.
  std::optional<std::string> interface_name = GetInterfaceName(interface_type);
  if (!interface_name) {
    return kPlatformResultFailure;
  }

  fuchsia::netstack::NetstackSyncPtr stack_sync_ptr;
  zx_status_t status = svc->Connect(stack_sync_ptr.NewRequest());
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to connect to netstack: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  }

  // Determine the interface ID to add/remove from.
  std::optional<uint64_t> interface_id = GetInterfaceId(interface_name.value());
  if (!add && interface_id && interface_id.value() == 0) {
    // When removing, don't report an error if the interface wasn't found. The
    // interface may already have been removed at this point.
    FX_LOGS(INFO) << "Interface " << interface_name.value() << " has already been removed.";
    return kPlatformResultSuccess;
  } else if (!interface_id) {
    return kPlatformResultFailure;
  }

  // Begin route table transaction to add or remove forwarding entries.
  fuchsia::netstack::RouteTableTransactionSyncPtr route_table_sync_ptr;
  zx_status_t transaction_status;
  status = stack_sync_ptr->StartRouteTableTransaction(route_table_sync_ptr.NewRequest(),
                                                      &transaction_status);
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to start route table transaction: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  } else if (transaction_status != ZX_OK) {
    FX_LOGS(ERROR) << "Unable to start route table transaction: "
                   << zx_status_get_string(transaction_status);
    return kPlatformResultFailure;
  }

  // Construct route table entry to add or remove.
  fuchsia::netstack::RouteTableEntry route_table_entry;
  fuchsia::net::Subnet destination;

  fuchsia::net::Ipv6Address ipv6_addr;
  std::memcpy(ipv6_addr.addr.data(), (uint8_t *)(prefix.IPAddr.Addr), ipv6_addr.addr.size());
  destination.addr.set_ipv6(ipv6_addr);
  destination.prefix_len = prefix.Length;

  route_table_entry.destination = std::move(destination);
  route_table_entry.nicid = interface_id.value();
  switch (priority) {
    case RoutePriority::kRoutePriorityHigh:
      route_table_entry.metric = kRouteMetric_HighPriority;
      break;
    case RoutePriority::kRoutePriorityMedium:
      route_table_entry.metric = kRouteMetric_MediumPriority;
      break;
    case RoutePriority::kRoutePriorityLow:
      route_table_entry.metric = kRouteMetric_LowPriority;
      break;
    default:
      FX_LOGS(WARNING) << "Unhandled route priority type, using lowest priority.";
      route_table_entry.metric = kRouteMetric_LowPriority;
  }

  // Start route table transaction.
  status = add ? route_table_sync_ptr->AddRoute(std::move(route_table_entry), &transaction_status)
               : route_table_sync_ptr->DelRoute(std::move(route_table_entry), &transaction_status);
  if (status != ZX_OK) {
    FX_LOGS(ERROR) << "Failed to modify route: " << zx_status_get_string(status);
    return kPlatformResultFailure;
  } else if (transaction_status != ZX_OK) {
    FX_LOGS(ERROR) << "Unable to modify route: " << zx_status_get_string(transaction_status);
    return kPlatformResultFailure;
  }

  FX_LOGS(INFO) << (add ? "Added" : "Removed") << " route to/from interface id "
                << interface_id.value();

#if WARM_CONFIG_SUPPORT_BORDER_ROUTING
  // Set IPv6 forwarding on interface. Note that IPv6 forwarding is only ever
  // enabled and never disabled. Once an interface is being managed, routes may
  // be added and removed over time, so do not thrash the forwarding state
  // during these transitions.
  //
  // TODO(https://fxbug.dev/78254): Enabling V6 forwarding should ideally happen
  // elsewhere, as this function's contract does not make any specific mention about
  // forwarding. However, implementations must enable forwarding when border routing
  // is enabled, signaled by ThreadThreadRouteAction and ThreadThreadPriorityAction
  // in WARM. As we defer those route changes to this function, this is done here for
  // now. Long term, this bug tracks proposing upstream changes that would create a
  // targeted action to enable forwarding / border-routing to clarify this contract.
  if (add && ShouldEnableV6Forwarding(interface_type)) {
    fuchsia::net::stack::StackSyncPtr net_stack_sync_ptr;
    status = svc->Connect(net_stack_sync_ptr.NewRequest());
    if (status != ZX_OK) {
      FX_LOGS(ERROR) << "Failed to connect to netstack: " << zx_status_get_string(status);
      return kPlatformResultFailure;
    }

    fuchsia::net::stack::Stack_SetInterfaceIpForwarding_Result forwarding_result;
    status = net_stack_sync_ptr->SetInterfaceIpForwarding(
        interface_id.value(), fuchsia::net::IpVersion::V6, true /* enable */, &forwarding_result);
    if (status != ZX_OK) {
      FX_LOGS(ERROR) << "Failed to enable IPv6 forwarding on interface id " << interface_id.value()
                     << ": " << zx_status_get_string(status);
      return kPlatformResultFailure;
    } else if (forwarding_result.is_err()) {
      FX_LOGS(ERROR) << "Unable to enable IPv6 forwarding on interface id " << interface_id.value()
                     << ": " << static_cast<uint32_t>(forwarding_result.err());
      return kPlatformResultFailure;
    }
  }
#endif  // WARM_CONFIG_SUPPORT_BORDER_ROUTING

  return kPlatformResultSuccess;
}

}  // namespace

WEAVE_ERROR Init(WarmFabricStateDelegate *inFabricStateDelegate) { return WEAVE_NO_ERROR; }

NL_DLL_EXPORT
void CriticalSectionEnter(void) {}

NL_DLL_EXPORT
void CriticalSectionExit(void) {}

// Add or remove a host address attached to the Thread or WLAN interfaces.
PlatformResult AddRemoveHostAddress(InterfaceType interface_type, const Inet::IPAddress &address,
                                    uint8_t prefix_length, bool add) {
  return AddRemoveAddressInternal(interface_type, address, prefix_length, add);
}

// Add or remove a host route attached to the Thread or WLAN interfaces.
PlatformResult AddRemoveHostRoute(InterfaceType interface_type, const Inet::IPPrefix &prefix,
                                  RoutePriority priority, bool add) {
  return AddRemoveRouteInternal(interface_type, prefix, priority, add);
}

NL_DLL_EXPORT
void RequestInvokeActions(void) { ::nl::Weave::Warm::InvokeActions(); }

#if WARM_CONFIG_SUPPORT_THREAD
PlatformResult AddRemoveThreadAddress(InterfaceType interface_type, const Inet::IPAddress &address,
                                      bool add) {
  return AddRemoveAddressInternal(interface_type, address, kThreadPrefixLength, add);
}
#endif  // WARM_CONFIG_SUPPORT_THREAD

#if WARM_CONFIG_SUPPORT_THREAD_ROUTING
PlatformResult StartStopThreadAdvertisement(InterfaceType interface_type,
                                            const Inet::IPPrefix &prefix, bool start) {
  // This is handled by the LoWPAN service, nothing to do here.
  return kPlatformResultSuccess;
}
#endif  // WARM_CONFIG_SUPPORT_THREAD_ROUTING

#if WARM_CONFIG_SUPPORT_BORDER_ROUTING
PlatformResult AddRemoveThreadRoute(InterfaceType interface_type, const Inet::IPPrefix &prefix,
                                    RoutePriority priority, bool add) {
  return AddRemoveRouteInternal(interface_type, prefix, priority, add);
}

PlatformResult SetThreadRoutePriority(InterfaceType interface_type, const Inet::IPPrefix &prefix,
                                      RoutePriority priority) {
  // This will be handled during the AddRemoveThreadRoute from WARM.
  return kPlatformResultSuccess;
}
#endif  // WARM_CONFIG_SUPPORT_BORDER_ROUTING

}  // namespace Platform
}  // namespace Warm
}  // namespace Weave
}  // namespace nl