RFC: Proposed new features for the next version of EML (0.2-alpha)

[robertreppel]

Proposed new features:

• Preconditions for commands, e.g. TimesheetCreated MustHaveHappened or TimesheetDeleted MustNotHaveHappened DONE
• Selecting individual event properties in Readmodel SubscribesTo
• Spreadsheet-like functionality for Readmodels, e.g. @SUM(TimesheetHoursLogged.hours).totalHours

Example:

Solution: Timesheets & Billing
EmlVersion: 0.2-alpha
Contexts:
- Name: Timesheets & Billing
  Streams:
  - Stream: User
    Commands:
    - Command:
        ID: RegisterUser
        Name: Register User
        Parameters:
        - Name: email
          Type: string
          Rules: []
        - Name: password
          Type: string
          Rules: []
        - Name: userId
          Type: string
          Rules:
          - IsRequired
        Postconditions:
        - UserRegistered
    Events:
    - Event:
        ID: UserRegistered
        Name: User Registered
        Properties:
        - Name: email
          Type: string
          IsHashed: false
        - Name: password
          Type: string
          IsHashed: true
        - Name: userId
          Type: string
          IsHashed: false
        Type: ""
  - Stream: Timesheet
    Commands:
    - Command:
        ID: CreateTimesheet
        Name: Create Timesheet
        Parameters:
        - Name: userId
          Type: string
          Rules:
          - MustExistIn UserLookup
        - Name: description
          Type: string
          Rules: []
        - Name: timesheetId
          Type: string
          Rules:
          - IsRequired
        Preconditions:
        - Not TimesheetCreated
        - LastEventIs Not TimesheetSubmitted
        Postconditions:
        - TimesheetCreated
    - Command:
        ID: SubmitTimesheet
        Name: Submit Timesheet
        Parameters:
        - Name: submissionDate
          Type: string
          Rules: []
        - Name: userId
          Type: string
          Rules:
          - MustExistIn UserLookup
        - Name: timesheetId
          Type: string
          Rules:
          - IsRequired
        Preconditioins:
        - Has TimesheetCreated
        - Not Has TimesheetSubmitted
        Postconditions:
        - TimesheetSubmitted
    Events:
    - Event:
        ID: TimesheetCreated
        Name: Timesheet Created
        Properties:
        - Name: userId
          Type: string
          IsHashed: false
        - Name: description
          Type: string
          IsHashed: false
        - Name: timesheetId
          Type: string
          IsHashed: false
        Type: ""
    - Event:
        ID: TimesheetSubmitted
        Name: Timesheet Submitted
        Properties:
        - Name: timesheetId
          Type: string
          IsHashed: false
        - Name: submissionDate
          Type: string
          IsHashed: false
        - Name: userId
          Type: string
          IsHashed: false
        Type: ""
  - Stream: TimesheetHours
    Commands:
    - Command:
        ID: LogHours
        Name: Log Hours
        Parameters:
        - Name: timesheethoursId
          Type: string
          Rules:
          - IsRequired
        - Name: timesheetId
          Type: string
          Rules:
          - MustExistIn TimesheetLookup
        - Name: date
          Type: string
          Rules: []
        - Name: hours
          Type: string
          Rules: []
        Postconditions:
        - TimesheetHoursLogged
    Events:
    - Event:
        ID: TimesheetHoursLogged
        Name: TimesheetHours Logged
        Properties:
        - Name: timesheethoursId
          Type: string
          IsHashed: false
        - Name: timesheetId
          Type: string
          IsHashed: false
        - Name: date
          Type: string
          IsHashed: false
        - Name: hours
          Type: string
          IsHashed: false
        Type: ""
  Readmodels:
  - Readmodel:
      ID: UserLookup
      Name: UserLookup
      Key: userId
      Columns:
      - UserRegistered.*
  - Readmodel:
      ID: TimesheetLookup
      Name: TimesheetLookup
      Key: timesheetId
      SubscribesTo:
      - TimesheetCreated.*
      - TimesheetSubmitted.submissionDate
      - @SUM(TimesheetHoursLogged.hours).totalHours
      - @MIN(TimesheetHoursLogged.date).fromDate
      - @MAX(TimesheetHoursLogged.date).toDate
      - @IF(@ISBLANK(TimesheetSubmitted.submissionDate),"","submitted on {{TimesheetSubmitted.submissionDate}}")
  - Readmodel:
      ID: TimesheetHoursLookup
      Name: TimesheetHoursLookup
      Key: timesheethoursId
      Columns:
      - TimesheetHoursLogged.*
Errors: []