# `ExGram.BotInit`
[🔗](https://github.com/rockneurotiko/ex_gram/blob/0.64.0/lib/ex_gram/bot_init.ex#L1)

Behaviour for library-level bot initialization hooks.

Modules implementing this behaviour are called once during bot startup,
before the user's `c:ExGram.Handler.init/1` callback. Use this to set up
storage tables, register processes, or inject data into every context.

## Return values

- `:ok` - hook succeeded, no extra data
- `{:ok, map()}` - hook succeeded, merge map into `extra_info`
  (which flows into every `ExGram.Cnt.extra`)
- `{:error, reason}` - hook failed, **the bot will not start**

## Registration

Register hooks in your bot module using the `on_bot_init/1-2` macro
(available via `use ExGram.Bot`):

    defmodule MyBot do
      use ExGram.Bot, name: :my_bot

      on_bot_init(MyLibrary.Initializer, some_opt: :value)
      # ...
    end

Libraries that provide a `use` macro should emit `on_bot_init/1-2` calls
automatically, so end-users don't need to wire anything manually.

## Execution order

Hooks run in declaration order, before the user's `c:ExGram.Handler.init/1`
callback. Each hook receives the accumulated `extra_info` from all previous
hooks via the `extra_info:` key in `init_opts`.

# `init_opts`

```elixir
@type init_opts() :: [bot: atom() | String.t(), token: String.t(), extra_info: map()]
```

# `on_bot_init`

```elixir
@callback on_bot_init(init_opts()) :: :ok | {:ok, map()} | {:error, any()}
```

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