SteelWheel sequence diagram

diagram.md

sequenceDiagram
    participant Controller
    participant Handler
    participant URLParams as URL Params<br/>(SteelWheel::Params)
    participant FormParams as Form Params<br/>(EasyParams)
    participant Form as ActionForm
    participant BusinessLogic

    Note over Controller,BusinessLogic: Initialization Phase
    Controller->>Handler: Handler.handle(params)
    Handler->>Handler: initialize(params)
    Handler->>Handler: prepare_params(params)
    Note right of Handler: Separates URL params<br/>from form params<br/>Sets @form_scope

    Note over Controller,BusinessLogic: Parameter Creation (Lazy)
    Controller->>Handler: handler.url_params
    Handler->>URLParams: new(input)
    URLParams-->>Handler: url_params instance
    Note right of URLParams: Type coercion<br/>Validation ready

    Controller->>Handler: handler.form_params
    Handler->>FormParams: new(form_input)
    FormParams-->>Handler: form_params instance
    Note right of FormParams: Type coercion<br/>Validation ready

    Note over Controller,BusinessLogic: Validation Phase
    Handler->>Handler: validate_preconditions()
    
    alt URL Params Invalid
        Handler->>URLParams: invalid?
        URLParams-->>Handler: true (errors present)
        Handler->>Handler: failure_params()
        Handler->>Handler: http_status = :bad_request
        Handler->>Handler: errors.merge!(url_params.errors)
        Handler->>Handler: failure_callback()
        Note right of Handler: Stop execution
    else Form Params Invalid
        Handler->>FormParams: invalid?
        FormParams-->>Handler: true (errors present)
        Handler->>Handler: failure_form()
        Handler->>Handler: http_status = :unprocessable_entity
        Handler->>FormParams: create_form(owner, method, action)
        FormParams->>Form: new(owner, params, errors)
        Form-->>Handler: form with errors
        Handler->>Handler: @form = form
        Handler->>Handler: failure_callback()
        Note right of Handler: Stop execution
    else Handler Validation Invalid
        Handler->>Handler: invalid? (ActiveModel validations)
        Handler-->>Handler: true (errors present)
        Handler->>Handler: failure_self()
        Handler->>Handler: http_status = status
        Handler->>Handler: errors.delete(@form_scope)
        Handler->>Handler: failure_callback()
        Note right of Handler: Stop execution
    end

    Note over Controller,BusinessLogic: Execution Phase (if validation passes)
    Handler->>Handler: success? == true
    Handler->>Handler: on_validation_success()
    Handler->>BusinessLogic: call()
    BusinessLogic-->>Handler: result

    Note over Controller,BusinessLogic: Form Creation (if needed)
    alt Form Requested (GET/new/edit)
        Controller->>Handler: handler.form
        Handler->>Handler: form_attributes
        Handler->>Form: new(owner, **form_attributes)
        Form-->>Handler: form instance
    else Form Requested (POST/PATCH with errors)
        Controller->>Handler: handler.form
        Handler->>FormParams: create_form(owner, method, action)
        FormParams->>Form: new(owner, params, errors)
        Form-->>Handler: form with errors
    end

    Note over Controller,BusinessLogic: Callback Phase
    alt Success
        Handler->>Handler: errors.empty?
        Handler->>Handler: success_callback()
        Handler->>Controller: Execute success block
    else Failure
        Handler->>Handler: failure_callback()
        Handler->>Controller: Execute failure block (by status)
    end
    

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