// Copyright (C) 2016 Deutsche Telekom AG.
//
// Author: Andrei Pavel <andrei.pavel@qualitance.com>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//           http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef CQL_HOST_DATA_SOURCE_H
#define CQL_HOST_DATA_SOURCE_H

#include <dhcpsrv/base_host_data_source.h>
#include <dhcpsrv/cql_connection.h>

#include <stdint.h>

#include <string>
#include <utility>

namespace isc {
namespace dhcp {

/// Forward declaration to the implementation of @ref CqlHostDataSource.
class CqlHostDataSourceImpl;

/// @brief Cassandra host data source
///
/// Implements @ref isc::dhcp::BaseHostDataSource interface customized to
/// Cassandra. Use of this backend implies that a Cassandra database is
/// available and that the Kea schema has been created within it.
class CqlHostDataSource : public BaseHostDataSource {
public:
    /// @brief Constructor
    ///
    /// Uses the following keywords in the parameters passed to it to connect
    /// to the database:
    /// - name - Name of the database to which to connect (mandatory)
    /// - host - Host to which to connect (optional, defaults to "localhost")
    /// - user - Username under which to connect (optional)
    /// - password - Password for "user" on the database (optional)
    ///
    /// If the database is successfully opened, the version number in the
    /// schema_version table will be checked against hard-coded value in the
    /// implementation file.
    ///
    /// Finally, all the CQL commands are pre-compiled.
    ///
    /// @param parameters A data structure relating keywords and values
    ///        concerned with the database.
    ///
    /// @throw isc::dhcp::NoDatabaseName Mandatory database name not given
    /// @throw isc::dhcp::DbOpenError Error opening the database
    /// @throw isc::dhcp::DbOperationError An operation on the open database has
    ///        failed.
    explicit CqlHostDataSource(
        const DatabaseConnection::ParameterMap& parameters);

    /// @brief Virtual destructor.
    ///
    /// Releases prepared CQL statements used by the backend.
    virtual ~CqlHostDataSource();

    /// @brief Adds a new @ref Host to the Cassandra database along with it's
    ///     reservations and options.
    ///
    /// The implementations of this method should guard against duplicate
    /// reservations for the same @ref Host, where possible. For example, when
    /// the reservation for the same @ref HWAddr and @ref SubnetID is added
    /// twice, @ref add() should throw a @ref DuplicateEntry exception. Note,
    /// that usually it is impossible to guard against adding duplicated @ref
    /// Host, where one instance is identified by @ref HWAddr, another one by
    /// @ref DUID.
    ///
    /// @param host pointer to the new @ref Host being added.
    virtual void add(const HostPtr& host);

    /// @brief Retrieves a single @ref Host connected to an IPv4 subnet.
    ///
    /// Implementations of this method should guard against the case when
    /// multiple instances of the @ref Host are present, e.g. when two @ref
    /// Host objects are found, one for the @ref DUID, another one for the @ref
    /// HWAddr. In such case, throw a @ref MultipleRecords exception.
    ///
    /// @param subnet_id subnet identifier to filter by
    /// @param hwaddr hardware address of the client to filter by or NULL if not
    ///     available
    /// @param duid client identifier to filter by or NULL if not available
    ///
    /// @return @ref ConstHostPtr to a @ref Host object using a specified @ref
    ///     HWAddr or @ref DUID
    ///
    /// @throw BadValue if both or neither of subnet_id and duid are specified
    virtual ConstHostPtr get4(const SubnetID& subnet_id,
                              const HWAddrPtr& hwaddr,
                              const DuidPtr& duid = DuidPtr()) const;

    /// @brief Retrieves a @ref Host connected to an IPv4 subnet.
    ///
    /// @param subnet_id subnet identifier to filter by
    /// @param identifier_type identifier type to filter by
    /// @param identifier_begin pointer to the beginning of a buffer containing a
    ///     host identifier to filter by
    /// @param identifier_len length of the host identifier buffer
    ///
    /// @return @ref Host object for which a reservation has been made using the
    ///     specified identifier
    virtual ConstHostPtr get4(const SubnetID& subnet_id,
                              const Host::IdentifierType& identifier_type,
                              const uint8_t* identifier_begin,
                              const size_t identifier_len) const;

    /// @brief Retrieves a @ref Host connected to an IPv4 subnet.
    ///
    /// Note that dynamically allocated addresses and reserved addresses can
    /// come into conflict. When the new address is assigned to a client, the
    /// allocation mechanism should check if this address is not reserved for
    /// some other @ref Host and not allocate it if a reservation is present.
    ///
    /// @param subnet_id Subnet identifier.
    /// @param address reserved IPv4 address.
    ///
    /// @return Const @ref Host object
    ///
    /// @throw BadValue if address in not a valid IPv4address
    virtual ConstHostPtr get4(const SubnetID& subnet_id,
                              const asiolink::IOAddress& address) const;

    /// @brief Retrieves a @ref Host connected to an IPv6 subnet.
    ///
    /// Implementations of this method should guard against the case when
    /// multiple instances of the @ref Host are present, e.g. when two
    /// @ref Host objects are found, one for the @ref DUID, another one for the
    /// @ref HWAddr. In such case, throw a @ref MultipleRecords exception.
    ///
    /// @param subnet_id subnet identifier to filter by
    /// @param hwaddr hardware address of the client to filter by or NULL if not
    ///     available
    /// @param duid client identifier to filter by or NULL if not available
    ///
    /// @return @ref Host object using a specified @ref HWAddr or @ref DUID
    ///
    /// @throw BadValue if both or neither of subnet_id and duid are specified
    virtual ConstHostPtr get6(const SubnetID& subnet_id,
                              const DuidPtr& duid,
                              const HWAddrPtr& hwaddr = HWAddrPtr()) const;

    /// @brief Returns a @ref Host connected to an IPv6 subnet.
    ///
    /// @param subnet_id subnet identifier to filter by
    /// @param identifier_type identifier type to filter by
    /// @param identifier_begin pointer to the beginning of a buffer containing a
    ///     host identifier to filter by
    /// @param identifier_len length of the host identifier buffer
    ///
    /// @return Const @ref Host object for which reservation has been made using
    /// the specified identifier.
    virtual ConstHostPtr get6(const SubnetID& subnet_id,
                              const Host::IdentifierType& identifier_type,
                              const uint8_t* identifier_begin,
                              const size_t identifier_len) const;

    /// @brief Returns a @ref Host with the specified reservation prefix.
    ///
    /// @param prefix IPv6 prefix for which the @ref Host object is searched.
    /// @param prefix_len IPv6 prefix length.
    ///
    /// @return Const @ref Host object using a specified HW address or DUID.
    ///
    /// @throw MultipleRecords if two or more rows are returned from the
    ///     Cassandra database
    virtual ConstHostPtr get6(const asiolink::IOAddress& prefix,
                              const uint8_t prefix_len) const;

    /// @brief Returns a host connected to the IPv6 subnet and having
    /// a reservation for a specified IPv6 address or prefix.
    ///
    /// @param subnet_id Subnet identifier.
    /// @param address reserved IPv6 address/prefix.
    ///
    /// @return Const @c Host object using a specified IPv6 address/prefix.
    virtual ConstHostPtr get6(const SubnetID& subnet_id,
                              const asiolink::IOAddress& address) const;

    /// @brief Return all @ref Host objects for the specified @ref HWAddr or
    /// @ref DUID.
    ///
    /// Returns all @ref Host objects which represent reservations
    /// for the specified HW address or DUID. Note, that this method may
    /// return multiple reservations because a particular client may have
    /// reservations in multiple subnets and the same client may be identified
    /// by HW address or DUID. The server is unable to verify that the specific
    /// DUID and HW address belong to the same client, until the client sends
    /// a DHCP message.
    ///
    /// Specifying both @ref HWAddr and @ref DUID is allowed for this method
    /// and results in returning all objects that are associated with hardware
    /// address OR duid. For example: if one @ref Host is associated with the
    /// specified @ref HWAddr and another @ref Host is associated with the
    /// specified @ref DUID, two hosts will be returned.
    ///
    /// @param hwaddr HW address of the client or NULL if no HW address
    /// available.
    /// @param duid client id or NULL if not available, e.g. DHCPv4 client case.
    ///
    /// @return collection of const @ref Host objects.
    virtual ConstHostCollection getAll(const HWAddrPtr& hwaddr,
                                       const DuidPtr& duid = DuidPtr()) const;

    /// @brief Return all hosts connected to any subnet for which reservations
    /// have been made using a specified identifier.
    ///
    /// This method returns all @ref Host objects which represent reservations
    /// for a specified identifier. This method may return multiple hosts
    /// because a particular client may have reservations in multiple subnets.
    ///
    /// @param identifier_type Identifier type.
    /// @param identifier_begin Pointer to a beginning of a buffer containing
    /// an identifier.
    /// @param identifier_len Identifier length.
    ///
    /// @return Collection of const @ref Host objects.
    virtual ConstHostCollection
    getAll(const Host::IdentifierType& identifier_type,
           const uint8_t* identifier_begin,
           const size_t identifier_len) const;

    /// @brief Returns a collection of hosts using the specified IPv4 address.
    ///
    /// This method may return multiple @ref Host objects if they are connected
    /// to different subnets.
    ///
    /// @param address IPv4 address for which the @ref Host object is searched.
    ///
    /// @return Collection of const @ref Host objects.
    virtual ConstHostCollection
    getAll4(const asiolink::IOAddress& address) const;

    /// @brief Returns description of the backend.
    ///
    /// This description may be multiline text that describes the backend.
    ///
    /// @return Description of the backend.
    virtual std::string getDescription() const;

    /// @brief Returns the name of the database.
    ///
    /// @return database name
    virtual std::string getName() const;

    /// @brief Return backend type
    ///
    /// @return backend type "cql"
    virtual std::string getType() const;

    /// @brief Retrieves schema version.
    ///
    /// @return Version number stored in the database, as a pair of unsigned
    ///         integers. "first" is the major version number, "second" is the
    ///         minor version number.
    ///
    /// @throw isc::dhcp::DbOperationError An operation on the open database
    ///        has failed.
    virtual std::pair<uint32_t, uint32_t> getVersion() const;

    /// @brief Commit Transactions
    ///
    /// Commits all pending database operations.
    virtual void commit();

    /// @brief Rollback Transactions
    ///
    /// Rolls back all pending database operations.
    virtual void rollback();

private:
    /// @brief Pointer to the implementation of the @ref CqlHostDataSource.
    CqlHostDataSourceImpl* impl_;
};  // class CqlHostDataSource

};  // namespace dhcp
};  // namespace isc

#endif  // CQL_HOST_DATA_SOURCE_H