WIP: app: add GET /api/model

This will be used by the UI to get the available wakenet models, in
preparation of dynamically updating the supported wake words on Willow.

For development I'm testing with a local JSON file and manually
generated tarballs. JSON content:

[
  {
    "model_friendly_name": "Alexa",
    "model_name": "wn9_alexa",
    "url": "http://was.dev.willow/wn9_alexa.tar.gz"
  },
  {
    "model_friendly_name": "Computer",
    "model_name": "wn9_computer_tts",
    "url": "http://was.dev.willow/wn9_computer_tts.tar.gz"
  }
]

Example content of a tarball:

drwxr-xr-x stijn/users       0 2023-05-10 05:06 wn9_alexa/
-rw-r--r-- stijn/users     168 2023-05-10 05:06 wn9_alexa/_MODEL_INFO_
-rw-r--r-- stijn/users  289638 2023-05-10 05:06 wn9_alexa/wn9_data
-rw-r--r-- stijn/users    1200 2023-05-10 05:06 wn9_alexa/wn9_index
-rw-r--r-- stijn/users       6 2023-12-15 23:23 wn9_alexa.txt

The txt file contains the friendly form of the wake word, for the
example above that would be "Alexa". We need this for the Willow help
text: "Say 'Alexa' to start!". We currently hardcode this full text in
the Willow C code, but only for 3 wake words. This will break once we
flash a wake word that is not included in the model partition during
build/flash.

We should also keep this friendly name in the JSON so that the UI can
just read that property to fill the dropdown.

TODO:
* implement getting JSON and tarball in CF worker
* add version in JSON - we can parse this from _MODEL_INFO_ but can we
  get the version of the models using an ESP-SR API?

app/const.py

@@ -2,6 +2,7 @@
 DB_URL = 'sqlite:////app/storage/was.db'
 DIR_ASSET = '/app/storage/asset'
 DIR_OTA = '/app/storage/ota'
+URL_WILLOW_MODELS = 'http://was.dev.willow/willow-srmodels.json'
 URL_WILLOW_RELEASES = 'https://worker.heywillow.io/api/release?format=was'
 URL_WILLOW_CONFIG = 'https://worker.heywillow.io/api/config'
 URL_WILLOW_TZ = 'https://worker.heywillow.io/api/asset?type=tz'

app/main.py

@@ -50,6 +50,7 @@
 from .routers import asset
 from .routers import client
 from .routers import config
+from .routers import model
 from .routers import ota
 from .routers import release
 from .routers import status
@@ -171,6 +172,7 @@ def api_redirect_admin():
 app.include_router(asset.router)
 app.include_router(client.router)
 app.include_router(config.router)
+app.include_router(model.router)
 app.include_router(ota.router)
 app.include_router(release.router)
 app.include_router(status.router)

app/routers/model.py

@@ -0,0 +1,42 @@
+from logging import getLogger
+from typing import Literal
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel, Field
+from requests import get
+
+from ..const import URL_WILLOW_MODELS
+
+
+log = getLogger("WAS")
+router = APIRouter(
+    prefix="/api",
+)
+
+
+def get_models():
+    models = []
+
+    try:
+        models = get(URL_WILLOW_MODELS)
+        models = models.json()
+    except Exception:
+        raise HTTPException(status_code=500, detail="failed to get models")
+
+    return models
+
+
+class GetModel(BaseModel):
+    type: Literal["wakenet"] = Field(
+        Query(..., description="Model type")
+    )
+
+
+@router.get("/model")
+async def api_get_model(asset: GetModel = Depends()):
+    log.debug("API GET MODEL: Request")
+
+    models = get_models()
+
+    return JSONResponse(content=models)