[5] Write what's happening in pictures in engineering design.

[JStonham]

The object is to persist the list of transactions between different instances of the application.

• Application:
  • validate
  • convert to transaction
  • pass transaction to TransactionAppender
• TransactionAppender:
  • Call the TransactionRepository to get a String of JSON.
  • Convert the String into a List<Transaction> by calling JsonInterpreter.
  • Add the new transaction to this List<Transaction>.
  • Give this List<Transaction> to Application to print.
  • Convert the appended List<Transaction> to a String of JSON again by calling JsonInterpreter.
  • Give this String to the TransactionRepository again to write to disk.
• JsonInterpreter:
  • String transactionsToString(List<Transaction). Get JSON String from TransactionRepository. Acceptance test is a String in the correct JSON format below.
  • List<Transaction> stringToTransactions(String). Get List<Transaction> from TransactionAppender. Acceptance test is list of transactions with correct components. JSON String example format:

{
  "transactions": [
    {
      "type":"DEBIT",
      "description":"Plastic Surgery",
      "money":-2500000,
      "date":"2018-06-13"
    },
    {
      "type":"CREDIT",
      "description":"Let Flat",
      "money":420000,
      "date":"2018-06-08"
    }
  ]
}

• TransactionRepository:
  • String findStoredJson() if not found create new JSON file {}, if not valid JSON throw new RuntimeException("Contact the developer at example.com").
  • void storeJson(String json). Save to ~/.config//budjen/transactions.json. If file not found throw new RuntimeException("Contact the developer at example.com").

Acceptance Criteria

1. Given I have not yet used the application, when I run budjen print then I expect no transactions.
2. Given I have not yet used the application and I provide a transaction, when I run budjen add then I expect transaction to be saved.
3. Given I have previously used the application, when I run budjen print then I expect a list of transactions.
4. Given I changed the JSON file to be rubbish, when I run budjen print then I only expect a message telling me to contact the developer.

[kinbiko]

• [x] Doesn't matter much, but the task says to use the description to detail the design, not a new comment :).
• [x] Add the pictures to make the reading easier (but don't rely on the pictures to convey information accurately - the text alone should be enough, although it may take longer to read)
• [x] Let's give names to things at this stage so it's easier to talk about. E.g. instead of 'a JSON Interpreter class' say 'JsonInterpreter (actual naming is up to you). Similarly for methods, but here you should also add the method signature, i.e. what does it return, what does it take as arguments, does it throw any exceptions?
• [x] Should the JSON Interpreter read a java.io.File or a String? I think perhaps one class for converting (and reading) java.io.File <-> String(JSON) and another for converting String(JSON) <-> List<Transaction> will make testing easier. Especially since the latter one is already done, iirc.
• [x] Repositories are generally the thing that talks to the file system (i.e. uses java.io.File or connects to a database. Maybe a TransactionAppender makes more sense?
• [x] What does the JSON in the file look like?
• [x] Where is the file stored?
• [ ] What should the system do if the file doesn't exist when attempting to read the file?
• [ ] What are criteria for saying that this work has been completed? (I.e. what are the acceptance tests?)

My current thinking (taking into account the code we wrote last time) is something like this. Hopefully you can fill a bit more detail?

• Application:
  • validate
  • convert to transaction
  • pass transaction to TransactionAppender
• TransactionAppender:
  • Call the TransactionRepository to get a String of JSON
  • Convert the String into a List<Transaction> by calling JsonInterpreter
  • Add the new transaction to this list
  • Convert the appended List<Transaction> to a String of JSON again
  • Give this String to the TransactionRepository again to write to disk.
• JsonInterpreter:
  • String transactionsToString(List<Transaction)
  • List<Transaction> stringToTransactions(String)
• TransactionRepository:
  • String findStoredJson()
  • void storeJson(String json)