# `Orchid.Scheduler.Context`
[🔗](https://github.com/SynapticStrings/Orchid/blob/main/lib/orchid/scheduler.ex#L7)

The state machine for workflow execution.

It tracks the progress of a Recipe, including which steps are pending, running,
or completed, and holds the data (params) produced so far.

## Data Structure Decisions

You might notice a mix of Lists and MapSets. This is intentional to balance
**deterministic execution** with **scheduling efficiency**:

* `:pending_steps` (List) - Kept as a list to preserve the **definition order**
    from the Recipe. When multiple steps are ready simultaneously, Orchid prefers
    to execute them in the order they were written. This ensures predictable behavior,
    especially for the `Serial` executor.
* `:running_steps` (MapSet) - Used for **O(1) lookups**. The scheduler frequently
    checks `member?/2` inside loops; a MapSet prevents this from becoming a performance bottleneck.
* `:available_keys` (MapSet) - Optimized for **Set Algebra**. Dependency resolution
    relies heavily on subset checks (`subset?/2`), which MapSets handle efficiently.
* `:recipe` (Struct) - The Recipe being executed.
* `:params` (Map) - A map of parameters available in the current context.
* `:history` (List) - A list of tuples recording the execution history of steps, including their indices and output keys.
* `:workflow_ctx` (Struct) - The `Orchid.WorkflowCtx` struct associated with the execution.
* `:assigns` (Map) - A map for storing additional context-specific data.

# `param_map`
[🔗](https://github.com/SynapticStrings/Orchid/blob/main/lib/orchid/scheduler.ex#L35)

```elixir
@type param_map() :: %{optional(atom() | binary()) => Orchid.Param.t()}
```

# `step_index`
[🔗](https://github.com/SynapticStrings/Orchid/blob/main/lib/orchid/scheduler.ex#L36)

```elixir
@type step_index() :: non_neg_integer()
```

# `t`
[🔗](https://github.com/SynapticStrings/Orchid/blob/main/lib/orchid/scheduler.ex#L37)

```elixir
@type t() :: %Orchid.Scheduler.Context{
  assigns: %{required(any()) => any()},
  available_keys: MapSet.t(Orchid.Step.io_key()),
  history: [{Orchid.Step.t(), MapSet.t(Orchid.Step.output_keys())}],
  params: param_map(),
  pending_steps: [{Orchid.Step.t(), step_index()}],
  recipe: Orchid.Recipe.t(),
  running_steps: MapSet.t(step_index()),
  workflow_ctx: Orchid.WorkflowCtx.t()
}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*