1. Refactor Effects and Transformations into Separate Modules

Current State: Right now, drawVideos() performs various tasks like scaling, positioning, blending, and text overlay, all within the same function.

Suggested Refactor: Break out each effect or transformation (e.g., scaleVideo(), applyBlendMode(), applyFilter(), addDebugText()) into standalone functions or classes. A module-based approach allows each effect to be applied conditionally, stacked, or even reused across different video instances. For example:

javascript
function applyTransformations(video, ctx, params) {
    // Transformation logic based on params (scale, position, etc.)
}
function applyBlend(video, ctx, params) {
    // Blending logic here
}
2. Event-Based State Management

Current State: You use key events and parameter toggles to control playback and load video elements.

Suggested Refactor: Introduce an event system where modules communicate changes (e.g., “video loaded,” “blend mode changed”) through custom events. This approach decouples each part of the visualizer, so new effects or controls can easily subscribe to or emit events without direct dependencies on other modules. This can be done with a simple pub/sub pattern.
3. Preset Loader and Storage

Current State: Presets are hardcoded in parameterStore.

Suggested Refactor: Implement a preset loader that pulls settings from JSON files, enabling user-configurable effects without code changes. This also simplifies future changes to the preset structure, as they’re centralized in external files. You could load presets on-demand and allow users to save new presets in JSON format.

javascript
function loadPresetsFromFile(filePath) {
    fetch(filePath)
        .then(res => res.json())
        .then(data => parameterStore.presets = data)
        .catch(console.error);
}
4. Optimize Video Loading with Lazy Loading or Pooled Videos

Current State: loadVideos() loads all videos up to maxVideosToLoad.

Suggested Refactor: Implement lazy loading or pooling to load only the required videos, and recycle elements instead of creating/destroying them each time. This reduces memory usage and loading times, especially for high numbers of videos. For example, maintain a pool of video elements and reuse them as needed, updating only the source URL.
Another approach is to pre-cache metadata (like dimensions and duration) when a video is first loaded, avoiding redundant network calls.
5. Asynchronous Asset Preloading

Current State: Video sources are fetched synchronously in getSourceFiles().

Suggested Refactor: Use asynchronous preloading with a Promise.all() to wait until all videos are cached before starting playback. This approach can reduce playback delays and ensure smoother transitions between videos:

javascript
async function preloadVideos() {
    const videoFiles = await getSourceFiles();
    await Promise.all(videoFiles.map(file => new Promise(resolve => {
        const video = document.createElement("video");
        video.src = file.src;
        video.onloadeddata = () => resolve(video);
    })));
    // Videos are now preloaded
}
6. Configuration-Driven Design

Current State: Parameters and configurations are hardcoded.

Suggested Refactor: Move configurable parameters (like videosToLoad, blend modes, etc.) to a centralized configuration file (e.g., config.json). This allows you to modify settings without touching code and opens up the possibility for user-customized configurations down the line.
7. Separate Rendering Logic into a Renderer Class

Current State: The rendering logic in drawVideos() mixes canvas drawing with UI and blending logic.

Suggested Refactor: Create a dedicated Renderer class that handles rendering tasks, such as updating the canvas size, drawing each video, and applying effects. This keeps rendering independent of state changes, making the code more modular and allowing the Renderer to be swapped out or modified independently of other systems.
8. Implement Dependency Injection for Testing

Current State: Dependencies like parameterStore and ctx are used directly.

Suggested Refactor: Use dependency injection to pass in these dependencies, enabling isolated testing of each module. For example, applyBlendMode(video, ctx, params) could take ctx and params as arguments, making it easier to test blending logic independently.
9. Use requestIdleCallback for Non-Urgent Tasks

Current State: Some tasks, like updating debug text or checking video state, run continuously.

Suggested Refactor: For tasks that don’t need to run every frame, consider requestIdleCallback, which allows the browser to perform non-urgent tasks during idle time. This approach optimizes CPU usage and can improve frame rates.
These adjustments will simplify future expansion, reduce memory and CPU usage, and improve readability and maintainability, making the project easier to evolve over time.