ML-197: add Elm-style Presto application

backlog/tasks/ml-197 - Provide-Elm-style-Presto-Music-Library-application.md

@@ -1,11 +1,11 @@
 ---
 id: ML-197
 title: Provide Elm-style Presto Music Library application
-status: In Progress
+status: Done
 assignee:
   - Codex
 created_date: "2026-05-26 05:39"
-updated_date: "2026-05-26 05:43"
+updated_date: "2026-05-26 05:56"
 labels:
   - presto
 dependencies: []
@@ -16,6 +16,13 @@ documentation:
   - presto/main.py
   - presto/tests/test_screens.py
   - presto/mise.toml
+modified_files:
+  - presto/music_library.py
+  - presto/tests/conftest.py
+  - presto/tests/test_screens.py
+  - presto/tests/test_music_library_architecture.py
+  - presto/mise.toml
+  - presto/README.md
 priority: medium
 ordinal: 30000
 ---
@@ -32,10 +39,10 @@ Add an alternative Presto Music Library application organized around the message
 
 <!-- AC:BEGIN -->
 
-- [ ] #1 A `music_library.py` application exposes the existing Home, calendar/day browsing, search, record detail, scrobble, network error, and display sleep interactions through the Elm-style runtime.
+- [x] #1 A `music_library.py` application exposes the existing Home, calendar/day browsing, search, record detail, scrobble, network error, and display sleep interactions through the Elm-style runtime.
-- [ ] #2 Scrolling, cover loading, wake handling, and API request behavior remain consistent with the current Presto app constraints.
+- [x] #2 Scrolling, cover loading, wake handling, and API request behavior remain consistent with the current Presto app constraints.
-- [ ] #3 Headless verification covers the new application screens and prevents accidental network access during render tests.
+- [x] #3 Headless verification covers the new application screens and prevents accidental network access during render tests.
-- [ ] #4 User-facing or deployment documentation is updated if introducing the alternative application changes available usage or verification instructions.
+- [x] #4 User-facing or deployment documentation is updated if introducing the alternative application changes available usage or verification instructions.
 <!-- AC:END -->
 
 ## Implementation Plan
@@ -60,4 +67,32 @@ Inspected `presto/poc.py`, `presto/main.py`, test harness, and `presto/mise.toml
 
 User approved the implementation plan on 2026-05-26 and requested that this task record be committed before application work begins.
 
+Implemented the standalone architecture-based entrypoint with `Model`/`Runtime`, message-driven transitions, command dispatch/effects, centralized rendering, prepared detail-cover effects, nonblocking drag messages, display sleep/wake consumption, API loading/reconnect effects, and scrobble feedback effects.
+
+Extended the emulator screen contract suite to cover both `main.py` and `music_library.py`, and added focused tests for the status state, render-without-cover-fetch, detail preparation messages, wake consumption, WiFi reconnect before search, and throttled drag updates.
+
+Added optional deployment documentation and a `music_library` mise deploy task. A compatible concurrent change switching the emulator task target to `music_library.py` was present in `presto/mise.toml`; it is not part of the agent-authored deploy-task hunk and will be left unstaged.
+
+Verified `main.py` and `music_library.py` with `py_compile` output directed to `/tmp`; verified the headless suite with `mise run test` (36 passed). Physical Presto hardware was not tested.
+
 <!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+
+## Summary
+
+- Added `presto/music_library.py`, a standalone Music Library entrypoint organized around the Elm-style `Model` / `Runtime` / message / effect / render architecture while preserving the current UI and API interactions.
+- Routed blocking requests and detail-cover preparation through effects, retaining cached or placeholder-only redraw behavior during scroll interactions and wake/sleep handling.
+- Added deployment/documentation support and expanded emulator coverage to exercise both entrypoints plus the architecture-specific event/effect behavior.
+
+## Verification
+
+- `python3 -c "import py_compile; py_compile.compile('main.py', cfile='/tmp/main.pyc', doraise=True); py_compile.compile('music_library.py', cfile='/tmp/music_library.pyc', doraise=True)"`
+- `mise run test` (36 passed)
+
+## Remaining Validation
+
+- The architecture-based entrypoint has not been exercised on a physical Pimoroni Presto device.
+<!-- SECTION:FINAL_SUMMARY:END -->

presto/README.md

@@ -56,6 +56,17 @@ That task copies `main.py` to `:main.py` and resets the Presto. It does not copy
 
 The Presto runs `main.py` on boot, connects to WiFi, syncs time, then opens the home screen.
 
+An equivalent Elm-style implementation is available in `music_library.py`. It
+uses messages, model updates, and effects for the application runtime while
+providing the same Music Library screens and API interactions. Deploy it as
+the device entrypoint with:
+
+```bash
+mise run music_library
+```
+
+This task copies `music_library.py` to `:main.py` on the device and resets it.
+
 ## Usage
 
 **Home:** tap **Search Collection** to search by text, or **Today's Records** to open the current month with today highlighted.
@@ -78,24 +89,29 @@ Run the headless smoke tests from this directory:
 mise run test
 ```
 
-The tests use `pimoroni-emulator` mock MicroPython modules, import `main.py` without starting the event loop, and block accidental network calls. They render all screen states and save screenshots to `tests/fixtures/` for manual inspection.
+The tests use `pimoroni-emulator` mock MicroPython modules, import both
+`main.py` and `music_library.py` without starting their event loops, and block
+accidental network calls. They render all screen states and save screenshots
+to `tests/fixtures/` for manual inspection. Additional runtime tests cover the
+message/effect boundary in `music_library.py`.
 
 For a syntax-only check without creating `__pycache__`:
 
 ```bash
 python3 -c "import py_compile; py_compile.compile('main.py', cfile='/tmp/main.pyc', doraise=True)"
+python3 -c "import py_compile; py_compile.compile('music_library.py', cfile='/tmp/music_library.pyc', doraise=True)"
 ```
 
 ## Troubleshooting
 
-| Symptom | Likely cause | Fix |
+| Symptom                                    | Likely cause                                    | Fix                                  |
-| --- | --- | --- |
+| ------------------------------------------ | ----------------------------------------------- | ------------------------------------ |
-| `secrets.py not found` | Credentials are missing on the device | Copy `secrets.py` to the Presto root |
+| `secrets.py not found`                     | Credentials are missing on the device           | Copy `secrets.py` to the Presto root |
-| `WIFI_SSID not set` or `API_TOKEN not set` | Required value is blank | Check `secrets.py` |
+| `WIFI_SSID not set` or `API_TOKEN not set` | Required value is blank                         | Check `secrets.py`                   |
-| `WiFi connection failed` | Wrong credentials or network unavailable | Verify SSID, password, and network |
+| `WiFi connection failed`                   | Wrong credentials or network unavailable        | Verify SSID, password, and network   |
-| `Could not reach server` | API token invalid, server down, or network lost | Check `API_TOKEN` and server status |
+| `Could not reach server`                   | API token invalid, server down, or network lost | Check `API_TOKEN` and server status  |
-| Grey cover placeholders | JPEG decoder unavailable or image URL failed | Check firmware and internet access |
+| Grey cover placeholders                    | JPEG decoder unavailable or image URL failed    | Check firmware and internet access   |
-| Black display after idle | Display sleep is active | Touch once to wake |
+| Black display after idle                   | Display sleep is active                         | Touch once to wake                   |
 
 ## API Contract
 

presto/mise.toml

@@ -10,6 +10,12 @@ mpremote fs cp main.py :main.py
 mpremote reset
 '''
 
+[tasks.music_library]
+run = '''
+mpremote fs cp music_library.py :main.py
+mpremote reset
+'''
+
 [tasks.poc]
 run = '''
 mpremote fs cp poc.py :main.py

presto/tests/conftest.py

@@ -1,11 +1,11 @@
 """Presto smoke test configuration and helpers.
 
-Uses the pimoroni-emulator's mock system so ``main.py`` can be imported
+Uses the pimoroni-emulator's mock system so the Presto entrypoints can be
-on CPython without real MicroPython hardware.  The emulator's headless
+imported on CPython without real MicroPython hardware. The emulator's
-display is set up as a session-scoped fixture; ``main`` is imported once
+headless display is set up as a session-scoped fixture.
-after the mocks are in place.
 """
 
+import importlib
 import sys
 from pathlib import Path
 
@@ -50,25 +50,31 @@ def _emulator():
 
 
 # ---------------------------------------------------------------------------
-# Module fixture — import main once
+# Module fixture - render both complete entrypoints
 # ---------------------------------------------------------------------------
 
-@pytest.fixture(scope="session")
+@pytest.fixture(scope="session", params=("main", "music_library"))
-def main_module(_emulator):
+def main_module(_emulator, request):
-    """Import ``main.py`` after the emulator mocks are installed.
+    """Import each application after emulator mocks are installed.
 
-    The ``__name__ == "__main__"`` guard ensures ``main()`` does not run.
+    The ``__name__ == "__main__"`` guards ensure ``main()`` does not run.
     ``fetch_thumbnail`` is monkey-patched to raise on any network call.
     """
-    import main
+    module = importlib.import_module(request.param)
 
     # Guard against accidental network access in smoke tests.
     def _raise_on_network(*_args, **_kwargs):
-        raise RuntimeError("Network call in smoke test — use mock data")
+        raise RuntimeError("Network call in smoke test - use mock data")
 
-    main.fetch_thumbnail = _raise_on_network
+    module.fetch_thumbnail = _raise_on_network
 
-    return main
+    return module
+
+
+@pytest.fixture(scope="session")
+def music_library_module(_emulator):
+    """Import the architecture-based application for transition tests."""
+    return importlib.import_module("music_library")
 
 
 # ---------------------------------------------------------------------------

presto/tests/test_music_library_architecture.py

@@ -0,0 +1,143 @@
+"""Behavioral checks for the Elm-style Presto application runtime."""
+
+import pytest
+
+from tests.conftest import make_mock_record
+
+
+@pytest.fixture(autouse=True)
+def _init_display(music_library_module):
+    music_library_module.init_display()
+
+
+def test_status_screen_renders(music_library_module):
+    from emulator.testing import screenshot
+
+    app = music_library_module.Model()
+    app.screen = music_library_module.STATE_STATUS
+    app.status_message = "Loading records..."
+
+    music_library_module.render(app)
+    screenshot("tests/fixtures/status-music-library.png")
+
+
+def test_detail_render_does_not_fetch_cover(music_library_module, monkeypatch):
+    app = music_library_module.Model()
+    app.screen = music_library_module.STATE_RECORD
+    app.detail.selected_index = 0
+    app.detail.source_screen = music_library_module.STATE_DAY
+
+    rec = make_mock_record()
+    rec["_detail_thumb_failed"] = False
+    app.day.records = [rec]
+
+    def _raise_on_fetch(*_args):
+        raise RuntimeError("render attempted network work")
+
+    monkeypatch.setattr(music_library_module, "fetch_thumbnail", _raise_on_fetch)
+
+    music_library_module.draw_record_detail(app)
+
+
+def test_detail_cover_is_prepared_by_effect_message(music_library_module, monkeypatch):
+    app = music_library_module.Model()
+    rec = make_mock_record()
+    rec["_detail_thumb_failed"] = False
+    app.day.records = [rec]
+
+    monkeypatch.setattr(
+        music_library_module,
+        "fetch_thumbnail",
+        lambda *_args: b"prepared-jpeg",
+    )
+
+    commands = music_library_module.open_record_update(
+        app, music_library_module.STATE_DAY, 0
+    )
+    assert commands == [
+        (music_library_module.FX_RENDER,),
+        (music_library_module.FX_PREPARE_DETAIL,),
+    ]
+    assert app.screen == music_library_module.STATE_STATUS
+
+    msg = music_library_module.run_effect(
+        app, (music_library_module.FX_PREPARE_DETAIL,)
+    )
+    assert app.day.records[0]["_detail_thumb_data"] is None
+
+    render_commands = music_library_module.update(app, msg)
+
+    assert app.screen == music_library_module.STATE_RECORD
+    assert app.day.records[0]["_detail_thumb_data"] == b"prepared-jpeg"
+    assert render_commands == [(music_library_module.FX_RENDER,)]
+
+
+def test_wake_touch_is_consumed(music_library_module):
+    app = music_library_module.Model()
+    app.screen = music_library_module.STATE_HOME
+    app.touch.display_awake = False
+
+    commands = music_library_module.update(
+        app,
+        (
+            music_library_module.MSG_TOUCH_DOWN,
+            music_library_module.HOME_BUTTON_X + 1,
+            music_library_module.HOME_BUTTON2_Y + 1,
+            1_000,
+        ),
+    )
+
+    assert commands == [(music_library_module.FX_WAKE_DISPLAY,)]
+    assert app.touch.consume_until_release is True
+    assert music_library_module.update(app, (music_library_module.MSG_TOUCH_UP,)) == []
+    assert app.screen == music_library_module.STATE_HOME
+
+
+def test_search_effect_reconnects_before_request(music_library_module, monkeypatch):
+    app = music_library_module.Model()
+    calls = []
+
+    monkeypatch.setattr(music_library_module, "wifi_connected", lambda: False)
+    monkeypatch.setattr(
+        music_library_module,
+        "connect_wifi_effect",
+        lambda _app: (calls.append("connect") or True, "127.0.0.1", "token"),
+    )
+    monkeypatch.setattr(
+        music_library_module,
+        "fetch_search_results",
+        lambda _app, _query: (calls.append("fetch") or [], False),
+    )
+
+    msg = music_library_module.load_search_effect(app, "blue")
+
+    assert calls == ["connect", "fetch"]
+    assert msg == (music_library_module.MSG_SEARCH_LOADED, [], False, 0)
+
+
+def test_drag_updates_are_throttled_through_messages(music_library_module):
+    app = music_library_module.Model()
+    app.screen = music_library_module.STATE_DAY
+    app.day.content_height = 1_000
+    app.touch.last_touch = 0
+
+    assert music_library_module.update(
+        app, (music_library_module.MSG_TOUCH_DOWN, 100, 250, 1_000)
+    ) == []
+
+    commands = music_library_module.update(
+        app,
+        (
+            music_library_module.MSG_TOUCH_MOVE,
+            150,
+            1_000 + music_library_module.DRAG_REDRAW_MS,
+        ),
+    )
+
+    assert commands == [(music_library_module.FX_RENDER_PARTIAL,)]
+    assert app.day.scroll_offset == 100
+    assert app.touch.dragging is True
+    assert music_library_module.update(
+        app, (music_library_module.MSG_TOUCH_UP,)
+    ) == [(music_library_module.FX_RENDER_PARTIAL,)]
+    assert app.touch.dragging is False

presto/tests/test_screens.py

@@ -1,4 +1,4 @@
-"""Smoke tests — verify every Presto screen renders without crashing.
+"""Smoke tests - verify every complete Presto entrypoint renders its screens.
 
 Each test:
 1. Creates an ``AppState`` (requires ``init_display`` fixture).
@@ -7,7 +7,7 @@ Each test:
 4. Asserts no exception occurred.
 5. Saves a screenshot to ``presto/tests/fixtures/`` for manual inspection.
 
-No network calls are made — ``fetch_thumbnail`` is monkey-patched to raise,
+No network calls are made - ``fetch_thumbnail`` is monkey-patched to raise,
 and mock records have ``_thumb_failed=True`` / ``_thumb_data=None``.
 """
 
@@ -18,7 +18,7 @@ from tests.conftest import make_mock_record
 
 @pytest.mark.usefixtures("init_display")
 class TestSmokeScreens:
-    """Smoke tests for all 7 Presto screens."""
+    """Smoke tests for all visible screens in both complete applications."""
 
     # ------------------------------------------------------------------
     # Helpers
@@ -251,7 +251,9 @@ class TestSmokeScreens:
         app.day.records = [rec]
         app.detail.selected_index = 0
         app.detail.source_screen = main_module.STATE_DAY
-        main_module._measure_detail_content(app, rec)
+        detail_height = main_module._measure_detail_content(app, rec)
+        if detail_height is not None:
+            app.detail.content_height = detail_height
         app.detail.scroll_offset = main_module._max_detail_scroll_offset(app)
 
         calls = []