# 1. Goal
An exam office checks if a student may register for an exam. A registration
program calls the check before it books the seat. The check reports each
rejection as a class-based exception.

# 2. Open questions
None.

# 3. Context
- The interface {{P}}IF_EXAM_REQUEST exists in package $TMP. It is active.
- The interface has the public type TY_REQUEST. The components are:
  STUDENT_ID (STRING), ENROLLED (ABAP_BOOL), PREREQ_PASSED (ABAP_BOOL),
  PREREQ_ID (STRING), ATTEMPTS (I), REG_DATE (D).
- An exam has a maximum number of attempts and a registration deadline. The
  caller reads both values from the exam master data.
- A prerequisite is another exam. PREREQ_ID is the id of that exam.

# 4. Contract
Create these classes in package $TMP.

{{P}}EXAM_CHECK
- The class is public and final. It has a public constructor.
- Constructor: IMPORTING iv_max_attempts TYPE i, iv_deadline TYPE d.
- Method CHECK: IMPORTING is_request TYPE {{P}}IF_EXAM_REQUEST=>TY_REQUEST
  RAISING {{P}}CX_NOT_ENROLLED, {{P}}CX_PREREQ_MISSING,
  {{P}}CX_NO_ATTEMPT_LEFT, {{P}}CX_DEADLINE_PASSED.
- Do not add other public methods.

{{P}}CX_EXAM_ERROR
- The class is public and abstract. It inherits from CX_STATIC_CHECK.
- Public read-only attribute MV_STUDENT_ID TYPE string.
- Public read-only attribute MV_TEXT TYPE string.

{{P}}CX_NOT_ENROLLED
- The class is public and final. It inherits from {{P}}CX_EXAM_ERROR.
- MV_TEXT contains the text 'The student is not enrolled.'

{{P}}CX_PREREQ_MISSING
- The class is public and final. It inherits from {{P}}CX_EXAM_ERROR.
- Public read-only attribute MV_PREREQ TYPE string.
- MV_TEXT contains the text 'The prerequisite exam is not passed.'

{{P}}CX_NO_ATTEMPT_LEFT
- The class is public and final. It inherits from {{P}}CX_EXAM_ERROR.
- Public read-only attribute MV_ATTEMPTS TYPE i.
- MV_TEXT contains the text 'No attempt is left.'

{{P}}CX_DEADLINE_PASSED
- The class is public and final. It inherits from {{P}}CX_EXAM_ERROR.
- Public read-only attribute MV_REG_DATE TYPE d.
- MV_TEXT contains the text 'The registration deadline has passed.'

# 5. Business rules
The method CHECK applies the rules in this sequence. It raises the exception
of the first rule that fails.
1. If IS_REQUEST-ENROLLED is abap_false, raise {{P}}CX_NOT_ENROLLED.
   MV_STUDENT_ID contains IS_REQUEST-STUDENT_ID.
2. If IS_REQUEST-PREREQ_PASSED is abap_false, raise {{P}}CX_PREREQ_MISSING.
   MV_STUDENT_ID contains IS_REQUEST-STUDENT_ID. MV_PREREQ contains
   IS_REQUEST-PREREQ_ID.
3. If IS_REQUEST-ATTEMPTS is greater than or equal to the maximum number of
   attempts, raise {{P}}CX_NO_ATTEMPT_LEFT. MV_STUDENT_ID contains
   IS_REQUEST-STUDENT_ID. MV_ATTEMPTS contains IS_REQUEST-ATTEMPTS.
4. If IS_REQUEST-REG_DATE is later than the registration deadline, raise
   {{P}}CX_DEADLINE_PASSED. MV_STUDENT_ID contains IS_REQUEST-STUDENT_ID.
   MV_REG_DATE contains IS_REQUEST-REG_DATE.
5. Else the registration is allowed. The method returns without an exception.

# 6. Constraints
- Release target: 8.16.
- Coding standards: Clean ABAP. Method length below 40 statements. No global
  variables. No comment that restates the code.
- Out of scope: do not change {{P}}IF_EXAM_REQUEST.

# 7. Acceptance
- All classes are active and have no syntax error.
- The hidden tests pass.
- The code has no ATC finding of priority 1 or 2.
- Write your own ABAP Unit tests for the class {{P}}EXAM_CHECK.