// Copyright (C) 2012-2013 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 LEASE_MGR_H
#define LEASE_MGR_H

#include <asiolink/io_address.h>
#include <dhcp/duid.h>
#include <dhcp/option.h>
#include <dhcp/hwaddr.h>
#include <dhcpsrv/lease.h>
#include <dhcpsrv/subnet.h>
#include <exceptions/exceptions.h>

#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>

#include <fstream>
#include <iostream>
#include <map>
#include <string>
#include <utility>
#include <vector>

/// @file lease_mgr.h
/// @brief An abstract API for lease database
///
/// This file contains declarations of Lease4, Lease6 and LeaseMgr classes.
/// They are essential components of the interface to any database backend.
/// Each concrete database backend (e.g. MySQL) will define a class derived
/// from LeaseMgr class.
///
/// Failover considerations:
/// There are no intermediate plans to implement DHCPv4 failover
/// (draft-ietf-dhc-failover-12.txt). Currently (Oct. 2012) the DHCPv6 failover
/// is being defined in DHC WG in IETF (draft-ietf-dhcpv6-failover-requirements,
/// draft-ietf-dhcpv6-failover-design), but the work is not advanced enough
/// for implementation plans yet. v4 failover requires additional parameters
/// to be kept with a lease. It is likely that v6 failover will require similar
/// fields. Such implementation will require database schema extension.
/// We have designed a way to expand/upgrade schemas during upgrades: a database
/// schema is versioned and sanity checks about required version will be done
/// upon start and/or upgrade. With this mechanism in place, we can add new
/// fields to the database. In particular we can use that capability to
/// introduce failover related fields.
///
/// However, there is another approach that can be reliably used to provide
/// failover, even without the actual failover protocol implemented. As the
/// first backend will use MySQL, we will be able to use Multi-Master capability
/// offered by MySQL and use two separatate Kea instances connecting to the
/// same database.
///
/// Nevertheless, we hope to have failover protocol eventually implemented in
/// the Kea.

namespace isc {
namespace dhcp {

/// @brief Exception thrown if name of database is not specified
class NoDatabaseName : public Exception {
public:
    NoDatabaseName(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};

/// @brief Exception thrown on failure to open database
class DbOpenError : public Exception {
public:
    DbOpenError(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};

/// @brief Exception thrown on failure to execute a database function
class DbOperationError : public Exception {
public:
    DbOperationError(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};

/// @brief Multiple lease records found where one expected
class MultipleRecords : public Exception {
public:
    MultipleRecords(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};

/// @brief Attempt to update lease that was not there
class NoSuchLease : public Exception {
public:
    NoSuchLease(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};

/// @brief Data is truncated
class DataTruncated : public Exception {
public:
    DataTruncated(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) {}
};


/// @brief Abstract Lease Manager
///
/// This is an abstract API for lease database backends. It provides unified
/// interface to all backends. As this is an abstract class, it should not
/// be used directly, but rather specialized derived class should be used
/// instead.
///
/// As all methods are virtual, this class throws no exceptions.  However,
/// methods in concrete implementations of this class may throw exceptions:
/// see the documentation of those classes for details.
class LeaseMgr {
public:
    /// @brief Defines maximum value for time that can be reliably stored.
    // If I'm still alive I'll be too old to care. You fix it.
    static const time_t MAX_DB_TIME;

    /// Database configuration parameter map
    typedef std::map<std::string, std::string> ParameterMap;

    /// @brief Constructor
    ///
    /// @param parameters A data structure relating keywords and values
    ///        concerned with the database.
    LeaseMgr(const ParameterMap& parameters) : parameters_(parameters)
    {}

    /// @brief Destructor
    virtual ~LeaseMgr()
    {}

    /// @brief Adds an IPv4 lease.
    ///
    /// @param lease lease to be added
    ///
    /// @result true if the lease was added, false if not (because a lease
    ///         with the same address was already there).
    virtual bool addLease(const isc::dhcp::Lease4Ptr& lease) = 0;

    /// @brief Adds an IPv6 lease.
    ///
    /// @param lease lease to be added
    ///
    /// @result true if the lease was added, false if not (because a lease
    ///         with the same address was already there).
    virtual bool addLease(const Lease6Ptr& lease) = 0;

    /// @brief Returns an IPv4 lease for specified IPv4 address
    ///
    /// This method return a lease that is associated with a given address.
    /// For other query types (by hardware addr, by client-id) there can be
    /// several leases in different subnets (e.g. for mobile clients that
    /// got address in different subnets). However, for a single address
    /// there can be only one lease, so this method returns a pointer to
    /// a single lease, not a container of leases.
    ///
    /// @param addr address of the searched lease
    ///
    /// @return smart pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(const isc::asiolink::IOAddress& addr) const = 0;

    /// @brief Returns existing IPv4 leases for specified hardware address.
    ///
    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
    ///
    /// @param hwaddr hardware address of the client
    ///
    /// @return lease collection
    virtual Lease4Collection getLease4(const isc::dhcp::HWAddr& hwaddr) const = 0;

    /// @brief Returns existing IPv4 leases for specified hardware address
    ///        and a subnet
    ///
    /// There can be at most one lease for a given HW address in a single
    /// pool, so this method with either return a single lease or NULL.
    ///
    /// @param hwaddr hardware address of the client
    /// @param subnet_id identifier of the subnet that lease must belong to
    ///
    /// @return a pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(const isc::dhcp::HWAddr& hwaddr,
                                SubnetID subnet_id) const = 0;

    /// @brief Returns existing IPv4 lease for specified client-id
    ///
    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
    ///
    /// @param clientid client identifier
    ///
    /// @return lease collection
    virtual Lease4Collection getLease4(const ClientId& clientid) const = 0;

    /// @brief Returns existing IPv4 lease for a given client identifier,
    /// HW address and subnet identifier.
    ///
    /// @todo Consider whether this function is needed or not. In the basic
    /// DHCPv4 server implementation it is not used by the allocation engine.
    ///
    /// @param client_id A client identifier.
    /// @param hwaddr Hardware address.
    /// @param subnet_id A subnet identifier.
    ///
    /// @return A pointer to the lease or NULL if the lease is not found.
    virtual Lease4Ptr getLease4(const ClientId& client_id, const HWAddr& hwaddr,
                                SubnetID subnet_id) const = 0;

    /// @brief Returns existing IPv4 lease for specified client-id
    ///
    /// There can be at most one lease for a given HW address in a single
    /// pool, so this method with either return a single lease or NULL.
    ///
    /// @param clientid client identifier
    /// @param subnet_id identifier of the subnet that lease must belong to
    ///
    /// @return a pointer to the lease (or NULL if a lease is not found)
    virtual Lease4Ptr getLease4(const ClientId& clientid,
                                SubnetID subnet_id) const = 0;

    /// @brief Returns existing IPv6 lease for a given IPv6 address.
    ///
    /// For a given address, we assume that there will be only one lease.
    /// The assumption here is that there will not be site or link-local
    /// addresses used, so there is no way of having address duplication.
    ///
    /// @param type specifies lease type: (NA, TA or PD)
    /// @param addr address of the searched lease
    ///
    /// @return smart pointer to the lease (or NULL if a lease is not found)
    virtual Lease6Ptr getLease6(Lease::Type type,
                                const isc::asiolink::IOAddress& addr) const = 0;

    /// @brief Returns existing IPv6 leases for a given DUID+IA combination
    ///
    /// Although in the usual case there will be only one lease, for mobile
    /// clients or clients with multiple static/fixed/reserved leases there
    /// can be more than one. Thus return type is a container, not a single
    /// pointer.
    ///
    /// @param type specifies lease type: (NA, TA or PD)
    /// @param duid client DUID
    /// @param iaid IA identifier
    ///
    /// @return Lease collection (may be empty if no lease is found)
    virtual Lease6Collection getLeases6(Lease::Type type, const DUID& duid,
                                        uint32_t iaid) const = 0;

    /// @brief Returns existing IPv6 lease for a given DUID+IA combination
    ///
    /// There may be more than one address, temp. address or prefix
    /// for specified duid/iaid/subnet-id tuple.
    ///
    /// @param type specifies lease type: (NA, TA or PD)
    /// @param duid client DUID
    /// @param iaid IA identifier
    /// @param subnet_id subnet id of the subnet the lease belongs to
    ///
    /// @return Lease collection (may be empty if no lease is found)
    virtual Lease6Collection getLeases6(Lease::Type type, const DUID& duid,
                                        uint32_t iaid, SubnetID subnet_id) const = 0;


    /// @brief returns zero or one IPv6 lease for a given duid+iaid+subnet_id
    ///
    /// This function is mostly intended to be used in unit-tests during the
    /// transition from single to multi address per IA. It may also be used
    /// in other cases where at most one lease is expected in the database.
    ///
    /// It is a wrapper around getLease6(), which returns a collection of
    /// leases. That collection can be converted into a single pointer if
    /// there are no leases (NULL pointer) or one lease (use that single lease).
    /// If there are more leases in the collection, the function will
    /// throw MultipleRecords exception.
    ///
    /// Note: This method is not virtual on purpose. It is common for all
    /// backends.
    ///
    /// @param type specifies lease type: (NA, TA or PD)
    /// @param duid client DUID
    /// @param iaid IA identifier
    /// @param subnet_id subnet id of the subnet the lease belongs to
    ///
    /// @throw MultipleRecords if there is more than one lease matching
    ///
    /// @return Lease pointer (or NULL if none is found)
    Lease6Ptr getLease6(Lease::Type type, const DUID& duid,
                        uint32_t iaid, SubnetID subnet_id) const;

    /// @brief Updates IPv4 lease.
    ///
    /// @param lease4 The lease to be updated.
    ///
    /// If no such lease is present, an exception will be thrown.
    virtual void updateLease4(const Lease4Ptr& lease4) = 0;

    /// @brief Updates IPv6 lease.
    ///
    /// @param lease6 The lease to be updated.
    virtual void updateLease6(const Lease6Ptr& lease6) = 0;

    /// @brief Deletes a lease.
    ///
    /// @param addr Address of the lease to be deleted. (This can be IPv4 or
    ///        IPv6.)
    ///
    /// @return true if deletion was successful, false if no such lease exists
    virtual bool deleteLease(const isc::asiolink::IOAddress& addr) = 0;

    /// @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 = 0;

    /// @brief Returns backend name.
    ///
    /// If the backend is a database, this is the name of the database or the
    /// file.  Otherwise it is just the same as the type.
    ///
    /// @return Name of the backend.
    virtual std::string getName() const = 0;

    /// @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 = 0;

    /// @brief Returns backend version.
    ///
    /// @return Version number as a pair of unsigned integers.  "first" is the
    ///         major version number, "second" the minor number.
    ///
    /// @todo: We will need to implement 3 version functions eventually:
    /// A. abstract API version
    /// B. backend version
    /// C. database version (stored in the database scheme)
    ///
    /// and then check that:
    /// B>=A and B=C (it is ok to have newer backend, as it should be backward
    /// compatible)
    /// Also if B>C, some database upgrade procedure may be triggered
    virtual std::pair<uint32_t, uint32_t> getVersion() const = 0;

    /// @brief Commit Transactions
    ///
    /// Commits all pending database operations.  On databases that don't
    /// support transactions, this is a no-op.
    virtual void commit() = 0;

    /// @brief Rollback Transactions
    ///
    /// Rolls back all pending database operations.  On databases that don't
    /// support transactions, this is a no-op.
    virtual void rollback() = 0;

    /// @todo: Add host management here
    /// As host reservation is outside of scope for 2012, support for hosts
    /// is currently postponed.

    /// @brief returns value of the parameter
    virtual std::string getParameter(const std::string& name) const;

private:
    /// @brief list of parameters passed in dbconfig
    ///
    /// That will be mostly used for storing database name, username,
    /// password and other parameters required for DB access. It is not
    /// intended to keep any DHCP-related parameters.
    ParameterMap parameters_;
};

}; // end of isc::dhcp namespace
}; // end of isc namespace

#endif // LEASE_MGR_H