ExchangeRate-API Quota Guarded Rates

arazzo: 1.0.1
info:
  title: ExchangeRate-API Quota Guarded Rates
  summary: Check remaining quota, then use the keyed endpoint or fall back to open access.
  description: >-
    A quota-aware rate retrieval flow that protects a limited request budget. It
    inspects the API key's remaining request quota and branches: when requests
    remain it pulls the latest rates from the authenticated keyed endpoint, and
    when the quota is exhausted it falls back to the no-key Open Access endpoint
    (which updates once daily and requires attribution). Each step inlines its
    full request, including the API key path parameter where applicable.
  version: 1.0.0
sourceDescriptions:
- name: exchangeRateApi
  url: ../openapi/exchangerate-api-openapi.yml
  type: openapi
workflows:
- workflowId: quota-guarded-rates
  summary: Branch on remaining quota between the keyed and Open Access rate endpoints.
  description: >-
    Reads the current request quota for the API key, then either fetches the
    latest rates via the authenticated endpoint when requests remain, or falls
    back to the Open Access endpoint when the quota has been exhausted.
  inputs:
    type: object
    required:
    - apiKey
    - baseCode
    properties:
      apiKey:
        type: string
        description: Your ExchangeRate-API dashboard API key.
      baseCode:
        type: string
        description: ISO 4217 three-letter base currency code (e.g. USD).
  steps:
  - stepId: checkQuota
    description: >-
      Read the plan quota and number of requests remaining for the API key
      before deciding which rate endpoint to use.
    operationId: getQuota
    parameters:
    - name: api_key
      in: path
      value: $inputs.apiKey
    successCriteria:
    - condition: $statusCode == 200
    - condition: $response.body#/result == "success"
    outputs:
      requestsRemaining: $response.body#/requests_remaining
      planQuota: $response.body#/plan_quota
    onSuccess:
    - name: quotaAvailable
      type: goto
      stepId: getKeyedLatest
      criteria:
      - context: $response.body
        condition: $.requests_remaining > 0
        type: jsonpath
    - name: quotaExhausted
      type: goto
      stepId: getOpenAccessLatest
      criteria:
      - context: $response.body
        condition: $.requests_remaining == 0
        type: jsonpath
  - stepId: getKeyedLatest
    description: >-
      Fetch the latest exchange rates through the authenticated keyed endpoint
      because quota is still available.
    operationId: getLatestRates
    parameters:
    - name: api_key
      in: path
      value: $inputs.apiKey
    - name: base_code
      in: path
      value: $inputs.baseCode
    successCriteria:
    - condition: $statusCode == 200
    - condition: $response.body#/result == "success"
    outputs:
      conversionRates: $response.body#/conversion_rates
      lastUpdate: $response.body#/time_last_update_utc
    onSuccess:
    - name: done
      type: end
  - stepId: getOpenAccessLatest
    description: >-
      Fall back to the no-key Open Access endpoint for once-daily rates because
      the keyed quota has been exhausted.
    operationId: getOpenAccessLatest
    parameters:
    - name: base_code
      in: path
      value: $inputs.baseCode
    successCriteria:
    - condition: $statusCode == 200
    - condition: $response.body#/result == "success"
    outputs:
      openAccessRates: $response.body#/rates
      provider: $response.body#/provider
      lastUpdate: $response.body#/time_last_update_utc
  outputs:
    requestsRemaining: $steps.checkQuota.outputs.requestsRemaining
    conversionRates: $steps.getKeyedLatest.outputs.conversionRates
    openAccessRates: $steps.getOpenAccessLatest.outputs.openAccessRates