model_language

# model_language (Elixir)

Elixir bindings for [model-language](https://github.com/wexiohub/model-language) —
a typed, safe template language for AI-agent prompts. Runs the exact same engine
as the JavaScript/TypeScript package via an **embedded** WebAssembly module:
byte-for-byte identical output, guaranteed by a shared conformance suite.

**▶ [Live demo](https://ml.wexio.io)** — try the language in a Tiptap editor
(live validation, autocomplete, real-time render), powered by the same engine.

Filters format values — dates, numbers, text:

```text
{{ user.created_at | date: "MMM D, YYYY" }}            →  Jul 5, 2026
{{ user.created_at | date: "h:mm A", "Europe/Kyiv" }}  →  5:37 PM
{{ user.last_seen  | time_ago }}                       →  3 days ago
```

```elixir
# mix.exs
def deps, do: [{:model_language, "~> 1.0"}]
```

```elixir
ModelLanguage.render(
  "Hi {{ user.name | default: 'there' }}!",
  data: %{"user" => %{"name" => "Vasyl"}}
)["text"]
# => "Hi Vasyl!"
```

Directives embed machine-readable constraints in a prompt. They are stripped from
the rendered text and returned in `directives`:

```elixir
src = """
Help with billing.
{{verify_before: payments}}
{{identity: contact.email == payment.email}}
Greet {{contact.first_name | default: "there"}}.
"""

out = ModelLanguage.render(
  src,
  data: %{"contact" => %{"first_name" => "Vasyl"}},
  schema: [
    %{"path" => "contact.email",      "type" => "string"},
    %{"path" => "contact.first_name", "type" => "string"},
  ]
)

out["text"]
# => "Help with billing.\n\nGreet Vasyl."

Enum.map(out["directives"], & &1["name"])
# => ["verify_before", "identity"]
```

- `render(template, data:, schema:, options:)` → `%{"text", "warnings", "resolvedBranches", "directives", "tokenEstimate"}`
- `validate(template, schema:, options:)` → `%{"diagnostics", "maxTokenEstimate"}`
- `parse(template)` → `%{"ast", "diagnostics"}`

Never raises for template problems — they degrade to empty output plus a warning.
Pass `options: %{"now" => epoch_ms}` for datetime filters.