#5: Traits to support status_code reaction

core/src/main/scala/za/co/absa/fadb/DBFunction.scala

@@ -29,7 +29,7 @@ import scala.concurrent.Future
   * @tparam T                   - the type covering the input fields of the database function
   * @tparam R                   - the type covering the returned fields from the database function
   */
-abstract class DBFunction[E, T, R](schema: DBSchema[E], functionNameOverride: Option[String] = None) {
+abstract class DBFunction[E, T, R](schema: DBSchema[E], functionNameOverride: Option[String] = None)  extends DBFunctionFabric {
   val functionName: String = {
     val fn = functionNameOverride.getOrElse(schema.objectNameFromClassName(getClass))
     if (schema.schemaName.isEmpty) {
@@ -39,6 +39,13 @@ abstract class DBFunction[E, T, R](schema: DBSchema[E], functionNameOverride: Op
     }
   }
 
+  /**
+    * For the given output it returns a function to execute the SQL query and interpret the results.
+    * Basically it should create a function which contains a query to be executable and executed on on the [[DBExecutor]]
+    * and transforming the result of that query to result type.
+    * @param values - the input values of the DB function (stored procedure)
+    * @return       - the query function that when provided an executor will return the result of the DB function call
+    */
   protected def queryFunction(values: T): QueryFunction[E, R]
 }
 

core/src/main/scala/za/co/absa/fadb/DBFunctionFabric.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2022 ABSA Group Limited
+ *
+ * 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 za.co.absa.fadb
+
+/**
+  * This trait serves the purpose of introducing functions that are common to all DB Function objects and mix-in traits
+  * that offer certain implementations. This trait should help with the inheritance of all of these
+  */
+trait DBFunctionFabric {
+  def functionName: String
+
+  protected def fieldsToSelect: Seq[String] = Seq.empty
+}

core/src/main/scala/za/co/absa/fadb/exceptions/DBFailException.scala

@@ -16,4 +16,12 @@
 
 package za.co.absa.fadb.exceptions
 
-case class DBFailException(status: Int, message: String) extends Exception(message)
+/**
+  * General Fa-DB exception class
+  * @param message  - the message describing the reason of exception
+  */
+class DBFailException(message: String) extends Exception(message)
+
+object DBFailException {
+  def apply(message: String): DBFailException = new DBFailException(message)
+}

core/src/main/scala/za/co/absa/fadb/package.scala

@@ -19,5 +19,11 @@ package za.co.absa
 import scala.concurrent.Future
 
 package object fadb {
+  /**
+    * Represents a database query call (in the model of Fa-Db a call to a DB stored procedure). When provided a DB
+    * connection (of type [[DBExecutor]]) it executes the query and transforms it to the desired result type sequence.
+    * @tparam E - the type of the DB connection to execute on
+    * @tparam R - the type of result
+    */
   type QueryFunction[E, R] = E => Future[Seq[R]]
 }

core/src/main/scala/za/co/absa/fadb/statushandling/StatusException.scala

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2022 ABSA Group Limited
+ *
+ * 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 za.co.absa.fadb.statushandling
+
+import za.co.absa.fadb.exceptions.DBFailException
+
+/**
+  * Exception caused by status signaling a failure in DB function execution
+  * @param status     - the status that caused the error
+  * @param statusText - the status text explaining the status code
+  */
+class StatusException(val status: Int, statusText: String) extends DBFailException(statusText) {
+  def statusText: String = getMessage
+}
+
+object StatusException {
+  class ServerMisconfigurationException(status: Int, statusText: String) extends StatusException(status, statusText)
+
+  class DataConflictException(status: Int, statusText: String) extends StatusException(status, statusText)
+
+  class DataNotFoundException(status: Int, statusText: String) extends StatusException(status, statusText)
+
+  class ErrorInDataException(status: Int, statusText: String) extends StatusException(status, statusText)
+
+  class OtherStatusException(status: Int, statusText: String) extends StatusException(status, statusText)
+
+}

core/src/main/scala/za/co/absa/fadb/statushandling/StatusHandling.scala

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2022 ABSA Group Limited
+ *
+ * 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 za.co.absa.fadb.statushandling
+
+import za.co.absa.fadb.DBFunctionFabric
+import za.co.absa.fadb.statushandling.StatusHandling.{defaultStatusFieldName, defaultStatusTextFieldName}
+
+import scala.util.Try
+
+/**
+  * A basis for mix-in traits for [[DBFunction]] that support `status` and `status_text` for easier handling
+  */
+trait StatusHandling extends DBFunctionFabric{
+
+  def statusFieldName: String = defaultStatusFieldName
+  def statusTextFieldName: String = defaultStatusTextFieldName
+
+  override protected def fieldsToSelect: Seq[String] = {
+    Seq(statusFieldName, statusTextFieldName) ++ super.fieldsToSelect
+  }
+
+  protected def checkStatus(status: Integer, statusTex: String): Try[Unit]
+}
+
+object StatusHandling {
+  val defaultStatusFieldName = "status"
+  val defaultStatusTextFieldName = "status_test"
+}

core/src/main/scala/za/co/absa/fadb/statushandling/fadbstandard/README.md

@@ -0,0 +1,79 @@
+# Intro
+
+This is a list of convention status codes to return from functions - the primary usage intention is in Postgres DB 
+functions, particularly in combination with fa-db library.
+
+The expected usage is that each function returns at least two values - `status` and `status_text`.
+
+Status is one of the values below. Status text is a human readable explanation of what happened. Status text should not 
+have a syntactical meaning.
+
+Exceptions from the rule above:
+* Immutable functions returning simple value
+* Function returning a (large) set of values, basically a query, where the obvious result would be no records for _“not found”_, otherwise a general ok `status` and `status_text`  on each line, just increasing the size of returned data.
+* _“Private”_ functions (not callable from outside of DB (no grants), name starting with underscore), if it’s more convenient for the usage of the function. It’s still recommended to use the `status` and `status_text` even there.
+
+General principle of status (code):
+* The codes are two digit
+* They are divided into sections
+* There are fixed values with a preferred meaning, try to keep to it
+* In each range there are “open” values to use in other or sub-cases of the general range meaning. Their meaning is specific the each function and depends on the contract between the function and the app calling it
+* Function should list all the possible returned statuses in it’s header/inline documentation together with their used meaning
+* When a status code suggests a not-OK state (values 20-99) the eventual other returned field values beyond `status` and `status_text` are undefined (probably will be NULL, but it should not be taken as a fact)
+* The possible returned status codes and their meaning should be described in the function comments
+
+# Codes
+
+The codes to be double digit
+
+## OK/Correct outcome
+
+### 10-19
+
+| 10 | general ok   |
+| 11 | data created |
+| 12 | data updated |
+| 14 | no op needed |
+| 15 | data deleted |
+
+Rest unspecified OK status, to be agreed in contract between DB and app
+
+## Server misconfiguration
+
+### 20-29
+
+Specific to the database application, should be shared over all functions in that DB.
+
+## Data conflict
+
+### 30-39
+
+| 30 | general data conflict |
+| 31 | referenced data does not allow execution of the request |
+
+Rest of the codes meaning depends on agreement in contact between DB and app
+
+## Data not found
+
+### 40-49
+
+| 40 | requested data not found |
+| 41 | master record not found  |
+| 42 | detail record not found  |
+
+Rest of the codes meaning depends on agreement in contact between DB and app
+
+## Error in data
+
+### 50-89
+
+| 50-59 | generally incorrect data (when obvious from context)                                     |
+| 60-69 | missing value (usually NULL)                                                             |
+| 70-79 | value out of range                                                                       |
+| 80-89 | wrong content of complex types (json, xml, hstore), like missing key, undesired key etc. |
+
+## Free range for other errors
+
+### 90-99
+
+Rest of the codes meaning depends on agreement in contact between DB and app

core/src/main/scala/za/co/absa/fadb/statushandling/fadbstandard/StandardStatusHandling.scala

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2022 ABSA Group Limited
+ *
+ * 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 za.co.absa.fadb.statushandling.fadbstandard
+
+import za.co.absa.fadb.exceptions.DBFailException
+import za.co.absa.fadb.statushandling.StatusHandling
+import za.co.absa.fadb.statushandling.StatusException._
+
+import scala.util.{Failure, Success, Try}
+
+/**
+  * A mix in trait for [[DBFunction]] for standard handling of `status` and `status_text` fields.
+  */
+trait StandardStatusHandling extends StatusHandling {
+  override protected def checkStatus(status: Integer, statusText: String): Try[Unit] = {
+    status / 10 match {
+      case 1              => Success(Unit)
+      case 2              => Failure(new ServerMisconfigurationException(status, statusText))
+      case 3              => Failure(new DataConflictException(status, statusText))
+      case 4              => Failure(new DataNotFoundException(status, statusText))
+      case 5 | 6 | 7 | 8  => Failure(new ErrorInDataException(status, statusText))
+      case 9              => Failure(new OtherStatusException(status, statusText))
+      case _              => Failure(DBFailException(s"Status out of range - with status: $status and status text: '$statusText'"))
+    }
+  }
+}

core/src/test/scala/za/co/absa/fadb/statushandling/fadbstandard/StandardStatusHandlingTest.scala

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2022 ABSA Group Limited
+ *
+ * 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 za.co.absa.fadb.statushandling.fadbstandard
+
+import org.scalatest.funsuite.AnyFunSuite
+import za.co.absa.fadb.statushandling.StatusException
+import za.co.absa.fadb.statushandling.StatusException._
+
+import scala.reflect.ClassTag
+import scala.util.{Failure, Try}
+
+class StandardStatusHandlingTest extends AnyFunSuite {
+  test("Verify checkStatus error mapping") {
+    class StandardStatusHandlingForTest extends StandardStatusHandling {
+      override def checkStatus(status: Integer, statusText: String): Try[Unit] = super.checkStatus(status, statusText)
+      override def functionName: String = "Never needed"
+    }
+
+    def assertCheckStatusFailure[F <: StatusException](status: Int, statusText: String)
+                                                      (implicit classTag: ClassTag[F], checker: StandardStatusHandlingForTest): Unit = {
+      val failure = intercept[F] {
+        checker.checkStatus(status, statusText).get
+      }
+      assert(failure.status == status)
+      assert(failure.statusText == statusText)
+    }
+    implicit val standardStatusHandling: StandardStatusHandlingForTest = new StandardStatusHandlingForTest
+
+    assert(standardStatusHandling.checkStatus(10, "OK").isSuccess)
+    assertCheckStatusFailure[ServerMisconfigurationException](21, "Server is wrongly set up")
+    assertCheckStatusFailure[DataConflictException](31, "Referenced data does not allow execution of the request")
+    assertCheckStatusFailure[DataNotFoundException](42, "Detail record not found")
+    assertCheckStatusFailure[ErrorInDataException](58, "Some incorrect data")
+    assertCheckStatusFailure[ErrorInDataException](69, "Missing value for field XYZ")
+    assertCheckStatusFailure[ErrorInDataException](73, "Value ABC is out of range")
+    assertCheckStatusFailure[ErrorInDataException](84, "Json value of field FF is missing property PPP")
+    assertCheckStatusFailure[OtherStatusException](95, "This is a special error")
+    assert(standardStatusHandling.checkStatus(101, "Server is wrongly set up").isFailure)
+  }
+}