src/main/kotlin/de/uapcore/lightpit/dao/AbstractDao.kt

/*
 * Copyright 2020 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */

package de.uapcore.lightpit.dao

import java.sql.PreparedStatement
import java.sql.ResultSet
import java.sql.Types

abstract class AbstractDao<T> {

    abstract fun mapResult(rs: ResultSet): T

    protected fun list(stmt: PreparedStatement): List<T> {
        return sequence {
            stmt.executeQuery().use { result ->
                while (result.next()) yield(mapResult(result))
            }
        }.toList()
    }

    protected fun find(stmt: PreparedStatement): T? {
        stmt.executeQuery().use { result ->
            return if (result.next()) {
                mapResult(result)
            } else {
                null
            }
        }
    }

    // TODO: create PreparedStatement abstraction that provides some features

    // TODO: remove the following legacy code helper function
    protected fun <T> setForeignKeyOrNull(stmt: PreparedStatement, index: Int, instance: T?, keyGetter: (obj: T) -> Int) {
        if (instance == null) {
            stmt.setNull(index, Types.INTEGER)
        } else {
            stmt.setInt(index, keyGetter(instance))
        }
    }
}