Add exists functions

src/main/kotlin/Exists.kt

@@ -0,0 +1,123 @@
+package solutions.bitbadger.documents
+
+import solutions.bitbadger.documents.query.Exists
+import java.sql.Connection
+
+/**
+ * Functions to determine whether documents exist
+ */
+object Exists {
+
+    /**
+     * Determine a document's existence by its ID
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param docId The ID of the document to be checked
+     * @param conn The connection on which the existence check should be executed
+     * @return True if the document exists, false if not
+     */
+    fun <TKey> byId(tableName: String, docId: TKey, conn: Connection) =
+        conn.customScalar(
+            Exists.byId(tableName, docId),
+            Parameters.addFields(listOf(Field.equal(Configuration.idField, docId, ":id"))),
+            Results::toExists
+        )
+
+    /**
+     * Determine a document's existence by its ID
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param docId The ID of the document to be checked
+     * @return True if the document exists, false if not
+     */
+    fun <TKey> byId(tableName: String, docId: TKey) =
+        Configuration.dbConn().use { byId(tableName, docId, it) }
+
+    /**
+     * Determine document existence using a field comparison
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param fields The fields which should be compared
+     * @param howMatched How the fields should be matched
+     * @param conn The connection on which the existence check should be executed
+     * @return True if any matching documents exist, false if not
+     */
+    fun byFields(
+        tableName: String,
+        fields: Collection<Field<*>>,
+        howMatched: FieldMatch? = null,
+        conn: Connection
+    ): Boolean {
+        val named = Parameters.nameFields(fields)
+        return conn.customScalar(
+            Exists.byFields(tableName, named, howMatched),
+            Parameters.addFields(named),
+            Results::toExists
+        )
+    }
+
+    /**
+     * Determine document existence using a field comparison
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param fields The fields which should be compared
+     * @param howMatched How the fields should be matched
+     * @return True if any matching documents exist, false if not
+     */
+    fun byFields(tableName: String, fields: Collection<Field<*>>, howMatched: FieldMatch? = null) =
+        Configuration.dbConn().use { byFields(tableName, fields, howMatched, it) }
+
+    /**
+     * Determine document existence using a JSON containment query (PostgreSQL only)
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param criteria The object for which JSON containment should be checked
+     * @param conn The connection on which the existence check should be executed
+     * @return True if any matching documents exist, false if not
+     * @throws DocumentException If called on a SQLite connection
+     */
+    inline fun <reified T> byContains(tableName: String, criteria: T, conn: Connection) =
+        conn.customScalar(
+            Exists.byContains(tableName),
+            listOf(Parameters.json(":criteria", criteria)),
+            Results::toExists
+        )
+
+    /**
+     * Determine document existence using a JSON containment query (PostgreSQL only)
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param criteria The object for which JSON containment should be checked
+     * @return True if any matching documents exist, false if not
+     * @throws DocumentException If called on a SQLite connection
+     */
+    inline fun <reified T> byContains(tableName: String, criteria: T) =
+        Configuration.dbConn().use { byContains(tableName, criteria, it) }
+
+    /**
+     * Determine document existence using a JSON Path match query (PostgreSQL only)
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param path The JSON path comparison to match
+     * @param conn The connection on which the existence check should be executed
+     * @return True if any matching documents exist, false if not
+     * @throws DocumentException If called on a SQLite connection
+     */
+    fun byJsonPath(tableName: String, path: String, conn: Connection) =
+        conn.customScalar(
+            Exists.byJsonPath(tableName),
+            listOf(Parameter(":path", ParameterType.STRING, path)),
+            Results::toExists
+        )
+
+    /**
+     * Determine document existence using a JSON Path match query (PostgreSQL only)
+     *
+     * @param tableName The name of the table in which document existence should be checked
+     * @param path The JSON path comparison to match
+     * @return True if any matching documents exist, false if not
+     * @throws DocumentException If called on a SQLite connection
+     */
+    fun byJsonPath(tableName: String, path: String) =
+        Configuration.dbConn().use { byJsonPath(tableName, path, it) }
+}