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/*
 * Copyright (C) 2018 Square, Inc.
 *
 * 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.
 */
package com.squareup.sqldelight

import com.squareup.sqldelight.db.SqlCursor
import com.squareup.sqldelight.db.SqlDriver
import com.squareup.sqldelight.db.use
import com.squareup.sqldelight.internal.QueryLock
import com.squareup.sqldelight.internal.copyOnWriteList
import com.squareup.sqldelight.internal.withLock

/**
 * A listenable, typed query generated by SQLDelight.
 *
 * @param RowType the type that this query can map its result set to.
 */
@Suppress("FunctionName") // Emulating a constructor.
fun  Query(
  identifier: Int,
  queries: MutableList>,
  driver: SqlDriver,
  query: String,
  mapper: (SqlCursor) -> RowType
): Query {
  return Query(identifier, queries, driver, "unknown", "unknown", query, mapper)
}

/**
 * A listenable, typed query generated by SQLDelight.
 *
 * @param RowType the type that this query can map its result set to.
 */
@Suppress("FunctionName") // Emulating a constructor.
fun  Query(
  identifier: Int,
  queries: MutableList>,
  driver: SqlDriver,
  fileName: String,
  label: String,
  query: String,
  mapper: (SqlCursor) -> RowType
): Query {
  return SimpleQuery(identifier, queries, driver, fileName, label, query, mapper)
}

private class SimpleQuery(
  private val identifier: Int,
  queries: MutableList>,
  private val driver: SqlDriver,
  private val fileName: String,
  private val label: String,
  private val query: String,
  mapper: (SqlCursor) -> RowType
) : Query(queries, mapper) {
  override fun execute(): SqlCursor {
    return driver.executeQuery(identifier, query, 0)
  }

  override fun toString() = "$fileName:$label"
}

/**
 * A listenable, typed query generated by SQLDelight.
 *
 * @param RowType the type that this query can map its result set to.
 *
 * @property mapper The mapper this [Query] was created with, which can convert a row in the SQL
 *   cursor returned by [execute] to [RowType].
 */
abstract class Query(
  private val queries: MutableList>,
  val mapper: (SqlCursor) -> RowType
) {
  private val listenerLock = QueryLock()
  private val listeners = copyOnWriteList()

  /**
   * Notify listeners that their current result set is staled.
   *
   * Called internally by SQLDelight when it detects a possible staling of the result set. Emits
   * some false positives but never misses a true positive.
   */
  fun notifyDataChanged() {
    listenerLock.withLock {
      listeners.forEach(Listener::queryResultsChanged)
    }
  }

  /**
   * Register a listener to be notified of future changes in the result set.
   */
  fun addListener(listener: Listener) {
    listenerLock.withLock {
      if (listeners.isEmpty()) queries.add(this)
      listeners.add(listener)
    }
  }

  /**
   * Remove a listener to no longer be notified of future changes in the result set.
   */
  fun removeListener(listener: Listener) {
    listenerLock.withLock {
      listeners.remove(listener)
      if (listeners.isEmpty()) queries.remove(this)
    }
  }

  /**
   * Execute the underlying statement.
   *
   * @return the cursor for the statement's result set.
   */
  abstract fun execute(): SqlCursor

  /**
   * @return The result set of the underlying SQL statement as a list of [RowType].
   */
  fun executeAsList(): List {
    val result = mutableListOf()
    execute().use {
      while (it.next()) result.add(mapper(it))
    }
    return result
  }

  /**
   * @return The only row of the result set for the underlying SQL statement as a non null
   *   [RowType].
   *
   * @throws NullPointerException if when executed this query has no rows in its result set.
   * @throws IllegalStateException if when executed this query has multiple rows in its result set.
   */
  fun executeAsOne(): RowType {
    return executeAsOneOrNull()
      ?: throw NullPointerException("ResultSet returned null for $this")
  }

  /**
   * @return The first row of the result set for the underlying SQL statement as a non null
   *   [RowType] or null if the result set has no rows.
   *
   * @throws IllegalStateException if when executed this query has multiple rows in its result set.
   */
  fun executeAsOneOrNull(): RowType? {
    execute().use {
      if (!it.next()) return null
      val item = mapper(it)
      check(!it.next()) { "ResultSet returned more than 1 row for $this" }
      return item
    }
  }

  /**
   * An interface for listening to changes in the result set of a query.
   */
  interface Listener {
    /**
     * Called whenever the query this listener was attached to is dirtied.
     *
     * Calls are made synchronously on the thread where the updated occurred, after the update applied successfully.
     */
    fun queryResultsChanged()
  }
}