Parallel preparation

# title: Parallel preparation
# category: Vibescript Showcase
# difficulty: Showcase
# summary: Start several independent functions in one Tasks.run scope and combine their handle values.
# description: Tasks.run opens a structured scope where tasks.spawn starts named functions and returns handles. Reading handle.value waits for that task. The scope auto-waits at exit, so no task can outlive it.
# tags: concurrency, tasks, structured-concurrency, spawn
# vibe: 0.4

def prepare_user(user)
  {
    id: user[:id],
    greeting: "ready:" + user[:id]
  }
end

def prepare_team(lead, second, third)
  Tasks.run(max: 3) do |tasks|
    a = tasks.spawn(:prepare_user, lead)
    b = tasks.spawn(:prepare_user, second)
    c = tasks.spawn(:prepare_user, third)

    first = a.value
    second_ready = b.value
    third_ready = c.value
    return [first, second_ready, third_ready]
  end
end

def run
  prepared = prepare_team(
    { id: "alice" },
    { id: "bob" },
    { id: "carol" }
  )

  {
    prepared: prepared,
    count: prepared.length
  }
end