Invoice chaser

nika: v1
workflow:
  id: invoice-chaser
  description: "chase unpaid invoices · ledger CSV → overdue filter → drafted reminder emails → human gate → drafts file"

model: ollama/qwen3.5:4b   # local · zero key · swap for groq/llama-3.3-70b (drafting is a fast-model job)

const:
  ledger_csv: "examples/fixtures/invoices.csv"
permits:
  tools: ["nika:convert", "nika:jq", "nika:prompt", "nika:read", "nika:write"]
  fs:
    # Two files, both spelled out — `const.ledger_csv` in, the drafts file
    # out. A const is baked in and a run cannot move it, so the boundary is
    # exact: no glob, and nothing else on disk is reachable either way.
    read: ["examples/fixtures/invoices.csv"]
    write: ["out/reminders-to-send.md"]

tasks:
  ledger:
    invoke:
      tool: "nika:read"
      args: { path: "${{ const.ledger_csv }}" }

  rows:
    with:
      csv: ${{ tasks.ledger.output }}
    invoke:
      tool: "nika:convert"
      args:
        input: "${{ with.csv }}"
        from: csv
        to: json
        has_header: true

  overdue:
    with:
      rows: ${{ tasks.rows.output }}
    invoke:
      tool: "nika:jq"
      args:
        input: "${{ with.rows }}"
        expression: 'map(select(.status == "overdue"))'

  drafts:
    with:
      overdue: ${{ tasks.overdue.output }}
    when: ${{ size(with.overdue) > 0 }}
    infer:
      max_tokens: 900       # a ceiling makes the cost report a number, not UNBOUNDED
      prompt: |
        Draft one short, polite payment reminder email per overdue invoice ·
        ${{ with.overdue }}
        Markdown · one section per client · firm but warm.

  approve:
    with:
      drafts: ${{ tasks.drafts.output }}
    when: ${{ with.drafts != null && size(with.drafts) > 0 }}   # nothing drafted — OR an empty answer (a thinking seat can spend the budget in its think block) · nothing to approve
    invoke:
      tool: "nika:prompt"
      args:
        message: "Save the reminder drafts for sending?"
        default: false

  save:
    with:
      drafts: ${{ tasks.drafts.output }}
      approved: ${{ tasks.approve.output }}
    when: ${{ with.drafts != null && size(with.drafts) > 0 && with.approved == true }}   # skipped (null) OR empty drafts → never write a 0-byte deliverable under a green run
    invoke:
      tool: "nika:write"
      args:
        path: out/reminders-to-send.md
        create_dirs: true
        content: "${{ with.drafts }}"

outputs:
  overdue:
    value: ${{ tasks.overdue.output }}
    description: "The overdue rows the reminders were drafted for"