    {- |
       Module     : Database.HDBC.Types
       Copyright  : Copyright (C) 2005-2011 John Goerzen
       License    : BSD3

       Maintainer : John Goerzen <jgoerzen@complete.org>
       Stability  : provisional
       Portability: portable

    Types for HDBC.

    Please note: this module is intended for authors of database driver libraries
    only.  Authors of applications using HDBC should use 'Database.HDBC'
    exclusively.

    Written by John Goerzen, jgoerzen\@complete.org
    -}

    module Database.HDBC.Types
        (IConnection(..),
        Statement(..),
        SqlError(..),
        nToSql, iToSql, posixToSql, fromSql, safeFromSql, toSql,
        SqlValue(..),
        ConnWrapper(..),
        withWConn
        )

    where
    import Database.HDBC.Statement
    import Database.HDBC.ColTypes
    import Control.Exception ( finally )

    {- | Main database handle object.

    An 'IConnection' object is created by specific functions in the module for an
    individual database.  That is, the connect function -- which creates
    this object -- is not standardized through the HDBC interface.

    A connection is closed by a call to 'disconnect'.

    A call to 'commit' is required to make sure that your changes get committed
    to the database.  In other words, HDBC has /no support for autocommit/, which
    we consider an outdated notion.
    -}
    class IConnection conn where
                    {- | Disconnect from the remote database.

    You do not need to explicitly close an IConnection object, but you may do so if
    you so desire.  If you don't, the object will disconnect from the database
    in a sane way when it is garbage-collected.  However, a disconnection may
    raise an error, so you are encouraged to explicitly call 'disconnect'.  Also,
    garbage collection may not run when the program terminates, and some databases
    really like an explicit disconnect.

    So, bottom line is, you're best off calling 'disconnect' directly, but the
    world won't end if you forget.

    This function discards any data not committed already.  Database driver
    implementators should explicitly call 'rollback' if their databases don't
    do this automatically on disconnect.

    Bad Things (TM) could happen if you call this while you have 'Statement's
    active.  In more precise language, the results in such situations are undefined
    and vary by database.  So don't do it.

    -}
                    disconnect :: conn -> IO ()
                    {- | Commit any pending data to the database.

                       Required to make any changes take effect. -}
                    commit :: conn -> IO ()
                    {- | Roll back to the state the database was in prior to the
                       last 'commit' or 'rollback'. -}
                    rollback :: conn -> IO ()
                    {- | Execute an SQL string, which may contain multiple
                       queries. This is intended for situations where you
                       need to run DML or DDL queries and aren't
                       interested in results. -}
                    runRaw :: conn -> String -> IO ()
                    runRaw conn
    conn String
    sql = do
                      sth <- conn -> String -> IO Statement
    forall conn. IConnection conn => conn -> String -> IO Statement
    prepare conn
    conn String
    sql
                      _ <- execute sth [] `finally` finish sth
                      return ()
                    {- | Execute a single SQL query.  Returns the number
                       of rows modified (see 'execute' for details).
                       The second parameter is a list
                       of replacement values, if any. -}
                    run :: conn -> String -> [SqlValue] -> IO Integer
                    {- | Prepares a statement for execution.

                       Question marks in the statement will be replaced by
                       positional parameters in a later call to 'execute'.

                       Please note that, depending on the database
                       and the driver, errors in your SQL may be raised
                       either here or by 'execute'.  Make sure you
                       handle exceptions both places if necessary. -}
                    prepare :: conn -> String -> IO Statement
                    {- | Create a new 'Connection' object, pointed at the same
                       server as this object is.  This will generally establish
                       a separate physical connection.

                       When you wish to establish multiple connections to a single
                       server, the correct way to do so is to establish the
                       first connection with the driver-specific connection
                       function, and then clone it for each additional connection.

                       This can be important when a database doesn't provide
                       much thread support itself, and the HDBC driver module
                       must serialize access to a particular database.

                       This can also be a handy utility function whenever you
                       need a separate connection to whatever database you are
                       connected to already. -}
                    clone :: conn -> IO conn

                    {- | The name of the HDBC driver module for this connection.
                       Ideally would be the same as the database name portion
                       of the Cabal package name.  For instance, \"sqlite3\"
                       or \"odbc\".  This is the layer that is bound most
                       tightly to HDBC. -}
                    hdbcDriverName :: conn -> String
                    {- | The version of the C (or whatever) client library
                       that the HDBC driver module is bound to.  The meaning
                       of this is driver-specific.  For an ODBC or similar
                       proxying driver, this should be the version of the
                       ODBC library, not the eventual DB client driver. -}
                    hdbcClientVer :: conn -> String
                    {- | In the case of a system such as ODBC, the name of
                       the database client\/server in use, if available.
                       For others,
                       identical to 'hdbcDriverName'. -}
                    proxiedClientName :: conn -> String
                    {- | In the case of a system such as ODBC, the version of
                       the database client in use, if available.  For others,
                       identical to 'hdbcClientVer'. This is the next layer
                       out past the HDBC driver. -}
                    proxiedClientVer :: conn -> String
                    {- | The version of the database server, if available. -}
                    dbServerVer :: conn -> String
                    {- | Whether or not the current database supports transactions.
                       If False, then 'commit' and 'rollback' should be expected
                       to raise errors.

                       MySQL is the only commonly-used database that is known
                       to not support transactions entirely.  Please see
                       the MySQL notes in the ODBC driver for more information. -}
                    dbTransactionSupport :: conn -> Bool

                    {- | The names of all tables accessible by the current
                       connection, excluding special meta-tables (system tables).

                       You should expect this to be returned in the same manner
                       as a result from 'Database.HDBC.fetchAllRows''.

                       All results should be converted to lowercase for you
                       before you see them.
                         -}
                    getTables :: conn -> IO [String]

                    {- | Obtain information about the columns in a specific
                       table.  The String in the result
                       set is the column name.

                       You should expect this to be returned in the same manner
                       as a result from 'Database.HDBC.fetchAllRows''.

                       All results should be converted to lowercase for you
                       before you see them.
                       -}
                    describeTable :: conn -> String -> IO [(String, SqlColDesc)]

    {- | Sometimes, it is annoying to use typeclasses with Haskell's type system.
    In those situations, you can use a ConnWrapper.  You can create one with:

    >let wrapped = ConnWrapper iconn

    You can then use this directly, since a ConnWrapper is also an
    'IConnection'.  However, you will not be able to use private database
    functions on it.

    Or, you can use 'withWConn'.
    -}
    data ConnWrapper = forall conn. IConnection conn => ConnWrapper conn

    {- | Unwrap a 'ConnWrapper' and pass the embedded 'IConnection' to
    a function.  Example:

    >withWConn wrapped run $ "SELECT * from foo where bar = 1" []
    -}
    withWConn :: forall b. ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn :: forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    conn forall conn. IConnection conn => conn -> b
    f =
        case ConnWrapper
    conn of
             ConnWrapper conn
    x -> conn -> b
    forall conn. IConnection conn => conn -> b
    f conn
    x

    instance IConnection ConnWrapper where
        disconnect :: ConnWrapper -> IO ()
    disconnect ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> IO ()) -> IO ()
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> IO ()
    forall conn. IConnection conn => conn -> IO ()
    disconnect
        commit :: ConnWrapper -> IO ()
    commit ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> IO ()) -> IO ()
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> IO ()
    forall conn. IConnection conn => conn -> IO ()
    commit
        rollback :: ConnWrapper -> IO ()
    rollback ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> IO ()) -> IO ()
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> IO ()
    forall conn. IConnection conn => conn -> IO ()
    rollback
        runRaw :: ConnWrapper -> String -> IO ()
    runRaw ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String -> IO ())
    -> String
    -> IO ()
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String -> IO ()
    forall conn. IConnection conn => conn -> String -> IO ()
    runRaw
        run :: ConnWrapper -> String -> [SqlValue] -> IO Integer
    run ConnWrapper
    w = ConnWrapper
    -> (forall conn.
        IConnection conn =>
        conn -> String -> [SqlValue] -> IO Integer)
    -> String
    -> [SqlValue]
    -> IO Integer
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String -> [SqlValue] -> IO Integer
    forall conn.
    IConnection conn =>
    conn -> String -> [SqlValue] -> IO Integer
    run
        prepare :: ConnWrapper -> String -> IO Statement
    prepare ConnWrapper
    w = ConnWrapper
    -> (forall conn.
        IConnection conn =>
        conn -> String -> IO Statement)
    -> String
    -> IO Statement
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String -> IO Statement
    forall conn. IConnection conn => conn -> String -> IO Statement
    prepare
        clone :: ConnWrapper -> IO ConnWrapper
    clone ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> IO ConnWrapper)
    -> IO ConnWrapper
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w (\conn
    dbh -> conn -> IO conn
    forall conn. IConnection conn => conn -> IO conn
    clone conn
    dbh IO conn -> (conn -> IO ConnWrapper) -> IO ConnWrapper
    forall a b. IO a -> (a -> IO b) -> IO b
    forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
    >>= ConnWrapper -> IO ConnWrapper
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (ConnWrapper -> IO ConnWrapper)
    -> (conn -> ConnWrapper) -> conn -> IO ConnWrapper
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . conn -> ConnWrapper
    forall conn. IConnection conn => conn -> ConnWrapper
    ConnWrapper)
        hdbcDriverName :: ConnWrapper -> String
    hdbcDriverName ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String) -> String
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String
    forall conn. IConnection conn => conn -> String
    hdbcDriverName
        hdbcClientVer :: ConnWrapper -> String
    hdbcClientVer ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String) -> String
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String
    forall conn. IConnection conn => conn -> String
    hdbcClientVer
        proxiedClientName :: ConnWrapper -> String
    proxiedClientName ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String) -> String
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String
    forall conn. IConnection conn => conn -> String
    proxiedClientName
        proxiedClientVer :: ConnWrapper -> String
    proxiedClientVer ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String) -> String
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String
    forall conn. IConnection conn => conn -> String
    proxiedClientVer
        dbServerVer :: ConnWrapper -> String
    dbServerVer ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> String) -> String
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String
    forall conn. IConnection conn => conn -> String
    dbServerVer
        dbTransactionSupport :: ConnWrapper -> Bool
    dbTransactionSupport ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> Bool) -> Bool
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> Bool
    forall conn. IConnection conn => conn -> Bool
    dbTransactionSupport
        getTables :: ConnWrapper -> IO [String]
    getTables ConnWrapper
    w = ConnWrapper
    -> (forall conn. IConnection conn => conn -> IO [String])
    -> IO [String]
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> IO [String]
    forall conn. IConnection conn => conn -> IO [String]
    getTables
        describeTable :: ConnWrapper -> String -> IO [(String, SqlColDesc)]
    describeTable ConnWrapper
    w = ConnWrapper
    -> (forall conn.
        IConnection conn =>
        conn -> String -> IO [(String, SqlColDesc)])
    -> String
    -> IO [(String, SqlColDesc)]
    forall b.
    ConnWrapper -> (forall conn. IConnection conn => conn -> b) -> b
    withWConn ConnWrapper
    w conn -> String -> IO [(String, SqlColDesc)]
    forall conn.
    IConnection conn =>
    conn -> String -> IO [(String, SqlColDesc)]
    describeTable