// Copyright (C) 2015 Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

#ifndef MYSQL_HOST_DATA_SOURCE_H
#define MYSQL_HOST_DATA_SOURCE_H

#include <dhcp/hwaddr.h>
#include <dhcpsrv/base_host_data_source.h>
#include <dhcpsrv/mysql_connection.h>

#include <boost/scoped_ptr.hpp>
#include <boost/utility.hpp>
#include <mysql.h>

namespace isc {
namespace dhcp {

// Forward declaration of the Host exchange objects.  These classes are defined
// in the .cc file.
class MySqlHostReservationExchange;
class MySqlIPv6ReservationExchange;

/// @brief MySQL Host Data Source
///
/// This class provides the @ref isc::dhcp::BaseHostDataSource interface to the MySQL
/// database.  Use of this backend presupposes that a MySQL database is
/// available and that the Kea schema has been created within it.
class MySqlHostDataSource: 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 SQL 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.
    MySqlHostDataSource(const DatabaseConnection::ParameterMap& parameters);

    /// @brief Destructor (closes database)
    virtual ~MySqlHostDataSource();

    /// @brief Return all hosts for the specified HW address or DUID.
    ///
    /// This method returns all @c 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 hardware address and DUID is allowed for this method
    /// and results in returning all objects that are associated with hardware
    /// address OR duid. For example: if one host is associated with the
    /// specified hardware address and another host is associated with the
    /// specified 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 @c Host objects.
    virtual ConstHostCollection
    getAll(const HWAddrPtr& hwaddr, const DuidPtr& duid = DuidPtr()) const;

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

    /// @brief Returns a host connected to the IPv4 subnet.
    ///
    /// Implementations of this method should guard against the case when
    /// mutliple instances of the @c Host are present, e.g. when two
    /// @c Host objects are found, one for the DUID, another one for the
    /// HW address. In such case, an implementation of this method
    /// should throw an MultipleRecords exception.
    ///
    /// @param subnet_id Subnet identifier.
    /// @param hwaddr HW address of the client or NULL if no HW address
    /// available.
    /// @param duid client id or NULL if not available.
    ///
    /// @return Const @c Host object using a specified HW address or DUID.
    virtual ConstHostPtr
    get4(const SubnetID& subnet_id, const HWAddrPtr& hwaddr,
            const DuidPtr& duid = DuidPtr()) const;

    /// @brief Returns a host connected to the IPv4 subnet and having
    /// a reservation for a specified IPv4 address.
    ///
    /// One of the use cases for this method is to detect collisions between
    /// dynamically allocated addresses and reserved addresses. When the new
    /// address is assigned to a client, the allocation mechanism should check
    /// if this address is not reserved for some other host and do not allocate
    /// this address if reservation is present.
    ///
    /// Implementations of this method should guard against invalid addresses,
    /// such as IPv6 address.
    ///
    /// @param subnet_id Subnet identifier.
    /// @param address reserved IPv4 address.
    ///
    /// @return Const @c Host object using a specified IPv4 address.
    virtual ConstHostPtr
    get4(const SubnetID& subnet_id, const asiolink::IOAddress& address) const;

    /// @brief Returns a host connected to the IPv6 subnet.
    ///
    /// Implementations of this method should guard against the case when
    /// mutliple instances of the @c Host are present, e.g. when two
    /// @c Host objects are found, one for the DUID, another one for the
    /// HW address. In such case, an implementation of this method
    /// should throw an MultipleRecords exception.
    ///
    /// @param subnet_id Subnet identifier.
    /// @param hwaddr HW address of the client or NULL if no HW address
    /// available.
    /// @param duid DUID or NULL if not available.
    ///
    /// @return Const @c Host object using a specified HW address or DUID.
    virtual ConstHostPtr
    get6(const SubnetID& subnet_id, const DuidPtr& duid,
            const HWAddrPtr& hwaddr = HWAddrPtr()) const;

    /// @brief Returns a host using the specified IPv6 prefix.
    ///
    /// @param prefix IPv6 prefix for which the @c Host object is searched.
    /// @param prefix_len IPv6 prefix length.
    ///
    /// @return Const @c Host object using a specified HW address or DUID.
    virtual ConstHostPtr
    get6(const asiolink::IOAddress& prefix, const uint8_t prefix_len) const;

    /// @brief Adds a new host to the collection.
    ///
    /// The implementations of this method should guard against duplicate
    /// reservations for the same host, where possible. For example, when the
    /// reservation for the same HW address and subnet id is added twice, the
    /// addHost method should throw an DuplicateEntry exception. Note, that
    /// usually it is impossible to guard against adding duplicated host, where
    /// one instance is identified by HW address, another one by DUID.
    ///
    /// @param host Pointer to the new @c Host object being added.
    virtual void add(const HostPtr& host);

    /// @brief Return backend type
    ///
    /// Returns the type of the backend (e.g. "mysql", "memfile" etc.)
    ///
    /// @return Type of the backend.
    virtual std::string getType() const {
        return (std::string("mysql"));
    }

    /// @brief Returns backend name.
    ///
    /// Each backend have specific name, e.g. "mysql" or "sqlite".
    ///
    /// @return Name of the backend.
    virtual std::string getName() 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 backend version.
    ///
    /// @return Version number stored in the database, as a pair of unsigned
    ///         integers. "first" is the major version number, "second" the
    ///         minor 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.  On databases that don't
    /// support transactions, this is a no-op.
    virtual void commit();

    /// @brief Rollback Transactions
    ///
    /// Rolls back all pending database operations.  On databases that don't
    /// support transactions, this is a no-op.
    virtual void rollback();

    MySqlConnection* getDatabaseConnection() {
        return &conn_;
    }

    /// @brief Statement Tags
    ///
    /// The contents of the enum are indexes into the list of SQL statements
    enum StatementIndex {
        INSERT_HOST,		// Insert new host to collection
        INSERT_V6_RESRV,        // Insert v6 reservation
        GET_HOST_HWADDR_DUID,   // Gets hosts by DUID and/or HW address
        GET_HOST_ADDR,		// Gets hosts by IPv4 address
        GET_HOST_SUBID4_DHCPID,	// Gets host by IPv4 SubnetID, HW address/DUID
        GET_HOST_SUBID6_DHCPID,	// Gets host by IPv6 SubnetID, HW address/DUID
        GET_HOST_SUBID_ADDR,    // Gets host by IPv4 SubnetID and IPv4 address
        GET_HOST_PREFIX,	// Gets host by IPv6 prefix
        GET_VERSION,            // Obtain version number
        NUM_STATEMENTS          // Number of statements
    };

private:
    /// @brief Add Host or IPv6 reservation Code
    ///
    /// This method performs adding a host or IPv6 reservation operation.
    ///	It binds the contents of the host object to
    /// the prepared statement and adds it to the database.
    ///
    /// @param stindex Index of statemnent being executed
    /// @param bind MYSQL_BIND array that has been created for the host
    ///
    /// @htrow isc::dhcp::DuplicateEntry Database throws duplicate entry error
    void addQuery(StatementIndex stindex, std::vector<MYSQL_BIND>& bind);

    /// @brief Get Host Collection Code
    ///
    /// This method obtains multiple hosts from the database.
    ///
    /// @param stindex Index of statement being executed
    /// @param bind MYSQL_BIND array for input parameters
    /// @param exchange Exchange object to use
    /// @param result ConstHostCollection object returned.  Note that any hosts
    ///        in the collection when this method is called are not erased: the
    ///        new data is appended to the end.
    /// @param single If true, only a single data item is to be retrieved.
    ///        If more than one is present, a MultipleRecords exception will
    ///        be thrown.
    ///
    /// @throw isc::dhcp::BadValue Data retrieved from the database was invalid.
    /// @throw isc::dhcp::DbOperationError An operation on the open database has
    ///        failed.
    /// @throw isc::dhcp::MultipleRecords Multiple records were retrieved
    ///        from the database where only one was expected.
    void getHostCollection(StatementIndex stindex, MYSQL_BIND* bind,
            boost::shared_ptr<MySqlHostReservationExchange> exchange,
            ConstHostCollection& result, bool single = false) const;

    /// @brief Get IPv6 Reservation Collection
    ///
    /// This method obtains multiple IPv6 reservations from the database.
    ///
    /// @param stindex Index of statement being executed
    /// @param bind MYSQL_BIND array for input parameters
    /// @param exchange Exchange object to use
    /// @param result IPv6ResrvCollection object returned.  Note that any
    ///        reservations in the collection when this method is called
    ///        are not erased: the new data is appended to the end.
    ///
    /// @throw isc::dhcp::BadValue Data retrieved from the database was invalid.
    /// @throw isc::dhcp::DbOperationError An operation on the open database has
    ///        failed.
    void getIPv6ReservationCollection(StatementIndex stindex, MYSQL_BIND* bind,
            boost::shared_ptr<MySqlIPv6ReservationExchange> exchange,
            IPv6ResrvCollection& result) const;

    /// @brief Check Error and Throw Exception
    ///
    /// Virtually all MySQL functions return a status which, if non-zero,
    /// indicates an error.  This inline function conceals a lot of error
    /// checking/exception-throwing code.
    ///
    /// @param status Status code: non-zero implies an error
    /// @param index Index of statement that caused the error
    /// @param what High-level description of the error
    ///
    /// @throw isc::dhcp::DbOperationError An operation on the open database
    ///        has failed.
    inline void checkError(int status, StatementIndex index,
            const char* what) const {
        if (status != 0) {
            isc_throw(DbOperationError, what << " for <"
                    << conn_.text_statements_[index] << ">, reason: "
                    << mysql_error(conn_.mysql_) << " (error code "
                    << mysql_errno(conn_.mysql_) << ")");
        }
    }

    /// @brief Checks if Host with same parameters already been added.
    ///
    /// @param host Pointer to the new @c Host object being added.
    bool checkIfExists(const HostPtr& host);

    /// @brief Adds IPv6 Reservation
    ///
    /// @param resv IPv6 Reservation to be added
    /// @param id ID of a host owning this reservation
    void addResv(const IPv6Resrv& resv, HostID id);
    
    // Members

    /// The exchange objects are used for transfer of data to/from the database.
    /// They are pointed-to objects as the contents may change in "const" calls,
    /// while the rest of this object does not.  (At alternative would be to
    /// declare them as "mutable".)

    /// @brief MySQL Host Reservation Exchange object
    boost::shared_ptr<MySqlHostReservationExchange> host_exchange_;

    /// @brief MySQL IPv6 Reservation Exchange object
    boost::shared_ptr<MySqlIPv6ReservationExchange> resv_exchange_;

    /// @brief MySQL connection
    MySqlConnection conn_;

};

}
}

#endif // MYSQL_HOST_DATA_SOURCE_H