feat: add Now Playing Logger plugin to showcase calling host functions from Python plugins

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/examples/Makefile

@@ -2,8 +2,12 @@
 # Auto-discover all plugin folders (folders containing go.mod)
 PLUGINS := $(patsubst %/go.mod,%,$(wildcard */go.mod))
 
+# Auto-discover Python plugins (folders containing plugin/__init__.py)
+PYTHON_PLUGINS := $(patsubst %/plugin/__init__.py,%,$(wildcard */plugin/__init__.py))
+
 # Prefer tinygo if available, it produces smaller wasm binaries.
 TINYGO := $(shell command -v tinygo 2> /dev/null)
+EXTISM_PY := $(shell command -v extism-py 2> /dev/null)
 
 # Default target: show available plugins
 .DEFAULT_GOAL := help
@@ -12,15 +16,24 @@ help:
 	@echo "Available Go plugins:"
 	@$(foreach p,$(PLUGINS),echo "  $(p)";)
 	@echo ""
+	@echo "Available Python plugins:"
+	@$(foreach p,$(PYTHON_PLUGINS),echo "  $(p)";)
+	@echo ""
 	@echo "Usage:"
 	@echo "  make <plugin>.wasm    Build a specific plugin (e.g., make $(firstword $(PLUGINS)).wasm)"
-	@echo "  make all         Build all Go plugins"
+	@echo "  make all              Build all plugins"
-	@echo "  make clean       Remove all built plugins"
+	@echo "  make all-go           Build all Go plugins"
+	@echo "  make all-python       Build all Python plugins (requires extism-py)"
+	@echo "  make clean            Remove all built plugins"
 
-all: $(PLUGINS:%=%.wasm)
+all: all-go all-python
+
+all-go: $(PLUGINS:%=%.wasm)
+
+all-python: $(PYTHON_PLUGINS:%=%.wasm)
 
 clean:
-	rm -f $(PLUGINS:%=%.wasm)
+	rm -f $(PLUGINS:%=%.wasm) $(PYTHON_PLUGINS:%=%.wasm)
 
 %.wasm: %/*.go %/go.mod
 ifdef TINYGO
@@ -28,3 +41,10 @@ ifdef TINYGO
 else
 	cd $* && GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared -o ../$@ .
 endif
+
+# Python plugin builds (generic rule for any folder with plugin/__init__.py)
+$(PYTHON_PLUGINS:%=%.wasm): %.wasm: %/plugin/__init__.py
+ifndef EXTISM_PY
+	$(error extism-py is not installed. Install from https://github.com/extism/python-pdk)
+endif
+	cd $* && extism-py plugin/__init__.py -o ../$@

plugins/examples/README.md

@@ -40,6 +40,7 @@ make clean
 | [crypto-ticker](crypto-ticker/)                 | Go       | Real-time cryptocurrency prices from Coinbase using WebSocket           |
 | [discord-rich-presence](discord-rich-presence/) | Go       | Discord Rich Presence integration using Scrobbler, WebSocket, Scheduler |
 | [coverartarchive-py](coverartarchive-py/)       | Python   | Album cover art from Cover Art Archive (Python example)                 |
+| [nowplaying-py](nowplaying-py/)                 | Python   | Logs currently playing tracks using Scheduler and SubsonicAPI           |
 
 ## Testing with Extism CLI
 

plugins/examples/coverartarchive-py/README.md

@@ -1,50 +1,54 @@
 # Cover Art Archive Plugin (Python)
 
-This plugin provides album cover images for Navidrome by querying the [Cover Art Archive](https://coverartarchive.org/) API using the MusicBrainz Release MBID.
+A Python example plugin that fetches album cover images from the [Cover Art Archive](https://coverartarchive.org/) API using the MusicBrainz Release MBID.
-
-**This is a Python example** demonstrating that Navidrome's plugin system supports multiple programming languages.
 
 ## Features
 
 - Implements the `nd_get_album_images` method of the MetadataAgent plugin interface
 - Returns front cover images for a given release MBID
 - Returns `not found` if no MBID is provided or no images are found
+- Demonstrates Python plugin development for Navidrome
 
 ## Prerequisites
 
-1. **extism-py** - Python to WASM compiler
+- [extism-py](https://github.com/extism/python-pdk) - Python PDK compiler
+  ```bash
+  curl -Ls https://raw.githubusercontent.com/extism/python-pdk/main/install.sh | bash
+  ```
 
-   Install using the official script:
+> **Note:** `extism-py` requires [Binaryen](https://github.com/WebAssembly/binaryen/) (`wasm-merge`, `wasm-opt`) to be installed.
-   ```bash
-   curl -Ls https://raw.githubusercontent.com/extism/python-pdk/main/install.sh | bash
-   ```
 
-   Or download from [extism/python-pdk releases](https://github.com/extism/python-pdk/releases).
+## Building
 
-2. **Extism CLI** (optional, for testing)
+From the `plugins/examples` directory:
-
-   ```bash
-   # macOS
-   brew install extism/tap/extism
-
-   # Or see https://extism.org/docs/install
-   ```
-
-## How to Build
 
 ```bash
-make build
+make coverartarchive-py.wasm
 ```
 
-Or manually:
+Or directly:
 
 ```bash
 extism-py plugin/__init__.py -o coverartarchive-py.wasm
 ```
 
-This produces `coverartarchive-py.wasm` in this directory.
+## Installation
 
-## Testing with Extism CLI
+1. Copy `coverartarchive-py.wasm` to your Navidrome plugins folder
+
+2. Enable plugins in `navidrome.toml`:
+   ```toml
+   [Plugins]
+   Enabled = true
+   Folder = "/path/to/plugins"
+   ```
+
+3. Add to your agents list:
+   ```toml
+   Agents = "coverartarchive-py,spotify,lastfm"
+   ```
+
+## Testing
 
 Test the manifest:
 
@@ -60,37 +64,14 @@ extism call coverartarchive-py.wasm nd_get_album_images --wasi \
   --allow-host "coverartarchive.org" --allow-host "archive.org"
 ```
 
-Run all tests:
+## How It Works
 
-```bash
+1. **Album Image Request (`nd_get_album_images`)**: Receives album metadata including the MusicBrainz Release MBID.
-make test
-```
 
-## Installation in Navidrome
+2. **API Query**: Fetches cover art metadata from `https://coverartarchive.org/release/{mbid}`.
 
-1. Build the plugin:
+3. **Response**: Returns the front cover image URL if found.
-   ```bash
-   make build
-   ```
-
-2. Copy to your Navidrome plugins folder:
-   ```bash
-   cp coverartarchive-py.wasm /path/to/navidrome/plugins/
-   ```
-
-3. Enable plugins in `navidrome.toml`:
-   ```toml
-   [Plugins]
-   Enabled = true
-   Folder = "/path/to/navidrome/plugins"
-   ```
-
-4. Add to your agents list:
-   ```toml
-   Agents = "coverartarchive-py,spotify,lastfm"
-   ```
 
 ## API Reference
 
 - [Cover Art Archive API](https://musicbrainz.org/doc/Cover_Art_Archive/API)
-- Endpoint used: `https://coverartarchive.org/release/{mbid}`

plugins/examples/nowplaying-py/Makefile

@@ -0,0 +1,12 @@
+# Build the Now Playing Logger Python plugin
+.PHONY: build test clean
+
+WASM_FILE = nowplaying-py.wasm
+
+build: $(WASM_FILE)
+
+$(WASM_FILE): plugin/__init__.py
+	extism-py plugin/__init__.py -o $(WASM_FILE)
+
+clean:
+	rm -f $(WASM_FILE)

plugins/examples/nowplaying-py/README.md

@@ -0,0 +1,116 @@
+# Now Playing Logger Plugin (Python)
+
+A Python example plugin that demonstrates the **Scheduler** and **SubsonicAPI** host services by periodically logging what is currently playing in Navidrome.
+
+## Features
+
+- Uses `scheduler_schedulerecurring` host function to set up a recurring task
+- Uses `subsonicapi_call` host function to query the `getNowPlaying` API
+- Configurable cron expression and user via plugin config
+- Demonstrates Python host function imports using `@extism.import_fn`
+
+## Prerequisites
+
+- [extism-py](https://github.com/extism/python-pdk) - Python PDK compiler
+  ```bash
+  curl -Ls https://raw.githubusercontent.com/extism/python-pdk/main/install.sh | bash
+  ```
+
+> **Note:** `extism-py` requires [Binaryen](https://github.com/WebAssembly/binaryen/) (`wasm-merge`, `wasm-opt`) to be installed.
+
+## Building
+
+From the `plugins/examples` directory:
+
+```bash
+make nowplaying-py.wasm
+```
+
+Or directly:
+
+```bash
+extism-py plugin/__init__.py -o nowplaying-py.wasm
+```
+
+## Installation
+
+1. Copy `nowplaying-py.wasm` to your Navidrome plugins folder
+
+2. Enable plugins in `navidrome.toml`:
+   ```toml
+   [Plugins]
+   Enabled = true
+   Folder = "/path/to/plugins"
+   ```
+
+3. Configure the plugin (optional):
+   ```toml
+   [PluginConfig.nowplaying-py]
+   cron = "*/1 * * * *"  # Check every minute (default)
+   user = "admin"        # Navidrome user for API calls (default)
+   ```
+
+### Configuration Options
+
+| Key    | Description                         | Default                      |
+|--------|-------------------------------------|------------------------------|
+| `cron` | Cron expression for check frequency | `*/1 * * * *` (every minute) |
+| `user` | Navidrome user for SubsonicAPI      | `admin`                      |
+
+## Testing
+
+Test the manifest:
+
+```bash
+extism call nowplaying-py.wasm nd_manifest --wasi
+```
+
+## Output
+
+When running, the plugin logs messages like:
+
+```
+🎵 john is playing: Pink Floyd - Comfortably Numb (The Wall)
+🎵 jane is playing: Radiohead - Paranoid Android (OK Computer)
+```
+
+Or when no one is playing:
+
+```
+🎵 No users currently playing music
+```
+
+## How It Works
+
+1. **Initialization (`nd_on_init`)**: Reads the cron expression from config and schedules a recurring task using the Scheduler host service.
+
+2. **Callback (`nd_scheduler_callback`)**: When the scheduled task fires, calls the SubsonicAPI `getNowPlaying` endpoint and logs the results.
+
+## Host Function Usage (Python)
+
+This plugin demonstrates how to call Navidrome host functions from Python:
+
+```python
+import extism
+import json
+
+# Import the host function
+@extism.import_fn("extism:host/user", "subsonicapi_call")
+def _subsonicapi_call(offset: int) -> int:
+    """Raw host function - returns memory offset."""
+    ...
+
+# Wrapper for JSON marshalling
+def subsonicapi_call(uri: str) -> dict:
+    request = {"uri": uri}
+    request_bytes = json.dumps(request).encode('utf-8')
+    request_mem = extism.memory.alloc(request_bytes)
+    response_offset = _subsonicapi_call(request_mem.offset)
+    response_mem = extism.memory.find(response_offset)
+    response = json.loads(extism.memory.string(response_mem))
+    
+    if response.get("error"):
+        raise Exception(response["error"])
+    
+    return json.loads(response.get("responseJSON", "{}"))
+```

plugins/examples/nowplaying-py/plugin/__init__.py

@@ -0,0 +1,197 @@
+# Now Playing Logger Plugin for Navidrome
+#
+# This plugin demonstrates the Scheduler and SubsonicAPI host services by
+# periodically logging what is currently playing in Navidrome.
+#
+# Build with:
+#   extism-py plugin/__init__.py -o nowplaying-py.wasm
+#
+# Test manifest with:
+#   extism call nowplaying-py.wasm nd_manifest --wasi
+#
+# Configuration:
+#   [PluginConfig.nowplaying-py]
+#   cron = "*/1 * * * *"  # Every minute (default)
+#   user = "admin"     # User to query getNowPlaying (default)
+
+import extism
+import json
+
+# Schedule ID for our recurring task
+SCHEDULE_ID = "nowplaying-check"
+
+
+# =============================================================================
+# Host Function Imports
+# =============================================================================
+# These are custom host functions provided by Navidrome.
+# We import them using the extism:host/user namespace.
+
+
+@extism.import_fn("extism:host/user", "scheduler_schedulerecurring")
+def _scheduler_schedulerecurring(offset: int) -> int:
+    """Raw host function - do not call directly."""
+    ...
+
+
+@extism.import_fn("extism:host/user", "subsonicapi_call")
+def _subsonicapi_call(offset: int) -> int:
+    """Raw host function - do not call directly."""
+    ...
+
+
+# =============================================================================
+# Host Function Wrappers
+# =============================================================================
+# These wrappers handle JSON marshalling/unmarshalling and memory management.
+
+
+def scheduler_schedule_recurring(cron_expression: str, payload: str, schedule_id: str) -> str:
+    """Schedule a recurring task using a cron expression.
+    
+    Args:
+        cron_expression: Cron format (e.g., "*/1 * * * *" for every minute)
+        payload: Data to pass to the callback
+        schedule_id: Unique identifier for the schedule
+        
+    Returns:
+        The schedule ID (same as input or auto-generated)
+    """
+    request = {
+        "cronExpression": cron_expression,
+        "payload": payload,
+        "scheduleID": schedule_id
+    }
+    request_bytes = json.dumps(request).encode('utf-8')
+    request_mem = extism.memory.alloc(request_bytes)
+    response_offset = _scheduler_schedulerecurring(request_mem.offset)
+    response_mem = extism.memory.find(response_offset)
+    response = json.loads(extism.memory.string(response_mem))
+    
+    if response.get("error"):
+        raise Exception(response["error"])
+    
+    return response.get("newScheduleID", schedule_id)
+
+
+def subsonicapi_call(uri: str) -> dict:
+    """Call a Subsonic API endpoint.
+    
+    Args:
+        uri: API path (e.g., "getNowPlaying")
+        
+    Returns:
+        Parsed JSON response from the API
+    """
+    request = {"uri": uri}
+    request_bytes = json.dumps(request).encode('utf-8')
+    request_mem = extism.memory.alloc(request_bytes)
+    response_offset = _subsonicapi_call(request_mem.offset)
+    response_mem = extism.memory.find(response_offset)
+    response = json.loads(extism.memory.string(response_mem))
+    
+    if response.get("error"):
+        raise Exception(response["error"])
+    
+    # Parse the nested JSON response
+    response_json = response.get("responseJSON", "{}")
+    return json.loads(response_json)
+
+
+# =============================================================================
+# Plugin Exports
+# =============================================================================
+
+
+@extism.plugin_fn
+def nd_manifest():
+    """Return the plugin manifest with metadata and permissions."""
+    manifest = {
+        "name": "Now Playing Logger (Python)",
+        "author": "Navidrome",
+        "version": "1.0.0",
+        "description": "Periodically logs currently playing tracks - Python example demonstrating Scheduler and SubsonicAPI host services",
+        "website": "https://github.com/navidrome/navidrome/tree/master/plugins/examples/nowplaying-py",
+        "permissions": {
+            "scheduler": {
+                "reason": "Schedule periodic checks for now playing status"
+            },
+            "subsonicapi": {
+                "reason": "Query the getNowPlaying API endpoint",
+                "allowAdmins": True
+            }
+        }
+    }
+    extism.output_str(json.dumps(manifest))
+
+
+@extism.plugin_fn
+def nd_on_init():
+    """Initialize the plugin by scheduling the recurring task."""
+    # Read cron expression from config, default to every minute
+    cron = extism.Config.get_str("cron")
+    if not cron:
+        cron = "*/1 * * * *"
+    
+    extism.log(extism.LogLevel.Info, f"Now Playing Logger initializing with cron: {cron}")
+    
+    try:
+        schedule_id = scheduler_schedule_recurring(cron, "check", SCHEDULE_ID)
+        extism.log(extism.LogLevel.Info, f"Scheduled recurring task with ID: {schedule_id}")
+    except Exception as e:
+        extism.log(extism.LogLevel.Error, f"Failed to schedule task: {e}")
+        raise
+    
+    # Return empty success response
+    extism.output_str(json.dumps({}))
+
+
+@extism.plugin_fn
+def nd_scheduler_callback():
+    """Handle scheduler callback - check and log now playing tracks."""
+    input_data = extism.input_json()
+    schedule_id = input_data.get("schedule_id", "")
+    
+    # Only handle our schedule
+    if schedule_id != SCHEDULE_ID:
+        extism.output_str(json.dumps({}))
+        return
+    
+    try:
+        # Read user from config, default to admin
+        user = extism.Config.get_str("user")
+        if not user:
+            user = "admin"
+        
+        # Call the getNowPlaying API
+        response = subsonicapi_call(f"getNowPlaying?u={user}")
+        
+        # Extract the subsonic-response
+        subsonic_response = response.get("subsonic-response", {})
+        now_playing = subsonic_response.get("nowPlaying", {})
+        entries = now_playing.get("entry", [])
+        
+        if not entries:
+            extism.log(extism.LogLevel.Info, "🎵 No users currently playing music")
+        else:
+            # Handle both single entry and list of entries
+            if isinstance(entries, dict):
+                entries = [entries]
+            
+            for entry in entries:
+                artist = entry.get("artist", "Unknown Artist")
+                title = entry.get("title", "Unknown Title")
+                album = entry.get("album", "Unknown Album")
+                username = entry.get("username", "Unknown User")
+                
+                extism.log(
+                    extism.LogLevel.Info,
+                    f"🎵 {username} is playing: {artist} - {title} ({album})"
+                )
+        
+        extism.output_str(json.dumps({}))
+        
+    except Exception as e:
+        error_msg = str(e)
+        extism.log(extism.LogLevel.Error, f"Failed to get now playing: {error_msg}")
+        extism.output_str(json.dumps({"error": error_msg}))

plugins/examples/wikimedia/README.md

@@ -150,7 +150,3 @@ wikimedia/
 | `nd_get_artist_url`       | Returns Wikipedia URL for an artist           |
 | `nd_get_artist_biography` | Returns artist biography from Wikipedia       |
 | `nd_get_artist_images`    | Returns artist image URLs from Wikidata       |
-
-## License
-
-Same as Navidrome - GPL-3.0