# Operation Contracts: Study Flash Cards

## Metadata
| Key | Value |
| --- | --- |
| ID | OC-001 |
| CrossReference | [SSD-001], [DM-001], [DICT-001] |

## Version History
| Date | Status | Author | Reviewer | Change | Commit |
| --- | --- | --- | --- | --- | --- |
| 2026-10-14 | Deprecated | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [c3fbcbc] |
| 2026-10-14 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Added chooseLevel; startStudySession returns the levels | [0b983b7] |

---

The turn-over of the card after 3000 ms is started by the system's own timer, not by a message from the Learner, so it has no contract; it is realized in [SD-001].

## Contract: startStudySession

| Item | Value |
| --- | --- |
| Operation | `startStudySession(): tuple[Level, ...]` |
| Traces to | `startStudySession` in [SSD-001] |
| Domain Model concepts | Level ([DM-001]); IT term `Level` ([DICT-001]) |

**Preconditions**

- The program was started without a level.

**Postconditions**

- The levels 100 words, 1000 words and all words are returned, in that order.
- No `StudySession` or `Deck` was created and no file was read.

**Exceptions**

| Condition (failing precondition) | Outcome |
| --- | --- |
| The program was started with a level | The operation is not sent; `chooseLevel` is the first operation |

## Contract: chooseLevel

| Item | Value |
| --- | --- |
| Operation | `chooseLevel(level: Level): CardDto \| None` |
| Traces to | `chooseLevel` in [SSD-001] |
| Domain Model concepts | Study Session, Words To Learn, Word List, Level, Flash Card ([DM-001]); IT terms `StudySession`, `Deck`, `Vocabulary`, `Level`, `Card` ([DICT-001]) |

**Preconditions**

- A `Vocabulary` exists in the word list file.
- `level` is one of the levels returned by `startStudySession`, or was given at start.

**Postconditions**

- A `StudySession` instance was created and associated with `level`.
- A `Deck` instance was created and associated with the `StudySession`.
- The `Deck` holds the cards of the progress file when it exists, otherwise a copy of the cards of the `Vocabulary`; cards outside the level are kept in it.
- The level's cards are the first `level.limit` cards of the `Vocabulary` (all of them when the limit is none or larger than the list).
- When the `Deck` holds a card of the level, `StudySession.current_card` was set to such a card and a `CardDto` of it is returned; otherwise `current_card` is `None` and `None` is returned.
- The Malay word of the card was passed to the `SpeechPort`.

**Exceptions**

| Condition (failing precondition) | Outcome |
| --- | --- |
| The word list file does not exist | `VocabularyNotFoundError` is raised; no session is created |
| The word list or progress file has no header of two cells, or a row with other than two cells | `VocabularyFormatError` is raised; no session is created and no file is changed |
| No card of the level is left in the `Deck` | `None` is returned; nothing is spoken |

## Contract: markKnown

| Item | Value |
| --- | --- |
| Operation | `markKnown(): None` |
| Traces to | `markKnown` in [SSD-001] |
| Domain Model concepts | Study Session, Words To Learn, Flash Card ([DM-001]); IT terms `StudySession`, `Deck`, `Card` ([DICT-001]) |

**Preconditions**

- A `StudySession` exists and its `current_card` is not `None`.

**Postconditions**

- The `Card` of `current_card` was removed from the `Deck` (the association was destroyed); cards outside the level are not touched.
- The whole `Deck` was stored in the progress file.
- `StudySession.current_card` was set to `None`.

**Exceptions**

| Condition (failing precondition) | Outcome |
| --- | --- |
| `current_card` is `None` (no card is shown) | Nothing is changed and nothing is stored |

## Contract: markUnknown

| Item | Value |
| --- | --- |
| Operation | `markUnknown(): CardDto \| None` |
| Traces to | `markUnknown` in [SSD-001] |
| Domain Model concepts | Study Session, Words To Learn, Flash Card ([DM-001]); IT terms `StudySession`, `Deck`, `Card` ([DICT-001]) |

**Preconditions**

- A `StudySession` exists.

**Postconditions**

- `StudySession.current_card` was set to a card of the level that differs from the previous `current_card` when the level holds two or more cards still to learn, and a `CardDto` of it is returned.
- When no card of the level is left, `current_card` is `None` and `None` is returned.
- The `Deck` and the progress file are unchanged.
- The Malay word of the new `current_card` was passed to the `SpeechPort`.

**Exceptions**

| Condition (failing precondition) | Outcome |
| --- | --- |
| No card of the level is left | `None` is returned; nothing is spoken |

---

[SSD-001]: ./ssd.md
[DM-001]: ../domain-model.md
[DICT-001]: ../dictionary.md
[SD-001]: ./sd.md
[c3fbcbc]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/031-flash-card/commit/c3fbcbcfaf799e0ae34aed7e14d3bc8a62f03db3
[0b983b7]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/031-flash-card/commit/0b983b7fdadf6958717c1d0227d0f2ebe037f7b1