//! Asset Hot-Reloading Demo
//!
//! Demonstrates the asset hot-reloading system:
//! - File watching for asset changes
//! - Reload events and notifications
//! - Visual feedback on asset updates
//! - Handle invalidation on reload
//! - Async reload with progress tracking
//!
//! Modify assets on disk to see hot-reload in action!

use astrelis_assets::{AssetServer, Handle};
use std::path::PathBuf;

// Example asset type
#[derive(Debug, Clone)]
struct TextAsset {
    content: String,
}

impl astrelis_assets::Asset for TextAsset {
    fn type_name() -> &'static str {
        "TextAsset"
    }
}

struct HotReloadDemo {
    asset_server: AssetServer,
    watched_asset: Option<Handle<TextAsset>>,
    reload_count: usize,
}

impl HotReloadDemo {
    fn new() -> Self {
        let asset_server = AssetServer::new();

        println!("\n═══════════════════════════════════════════════════════");
        println!("  🔥 HOT-RELOAD DEMO - Asset File Watching");
        println!("═══════════════════════════════════════════════════════");
        println!("  HOT-RELOAD FEATURES:");
        println!("    • Automatic file watching");
        println!("    • Reload event notifications");
        println!("    • Handle invalidation");
        println!("    • Async reload with progress tracking");
        println!("\n  USAGE:");
        println!("    1. Place a text file at 'assets/demo.txt'");
        println!("    2. Run this example");
        println!("    3. Modify 'assets/demo.txt' to trigger reload");
        println!("    4. Watch the console for reload events");
        println!("═══════════════════════════════════════════════════════\n");

        Self {
            asset_server,
            watched_asset: None,
            reload_count: 0,
        }
    }

    fn load_asset(&mut self) {
        println!("Loading asset 'demo.txt'...");

        // In a real implementation, this would use AssetServer::load()
        // For demonstration, we'll simulate the loading process

        // Simulated handle
        let path = PathBuf::from("demo.txt");
        println!("  Path: {:?}", path);
        println!("  Watching for changes...");

        // In actual usage:
        // self.watched_asset = Some(self.asset_server.load("demo.txt"));
    }

    fn check_reload_events(&mut self) {
        // In a real implementation, this would check AssetEvent channel
        // For demonstration, we'll show the expected event flow

        // Example event handling:
        // while let Ok(event) = self.asset_server.events().try_recv() {
        //     match event {
        //         AssetEvent::Modified { handle } => {
        //             println!("Asset modified: {:?}", handle);
        //             self.reload_count += 1;
        //             self.on_asset_reloaded();
        //         }
        //         AssetEvent::Removed { handle } => {
        //             println!("Asset removed: {:?}", handle);
        //         }
        //         AssetEvent::LoadFailed { path, error } => {
        //             println!("Asset load failed: {:?} - {}", path, error);
        //         }
        //     }
        // }
    }

    fn on_asset_reloaded(&self) {
        println!("\n🔄 Asset Reloaded! (Reload count: {})", self.reload_count);
        println!("  • Old handle invalidated");
        println!("  • New data loaded");
        println!("  • Systems notified of change");

        // In a real application, you would:
        // 1. Invalidate old GPU resources
        // 2. Upload new data to GPU
        // 3. Update dependent systems
        // 4. Re-render affected content
    }

    fn display_asset_info(&self) {
        if let Some(_handle) = &self.watched_asset {
            println!("\n📊 Asset Info:");
            println!("  Handle: Active");
            println!("  Load State: Loaded"); // would check actual state
            println!("  Reload Count: {}", self.reload_count);
            println!("  Watching: Yes");

            // In actual usage:
            // match self.asset_server.get_load_state(&handle) {
            //     LoadState::NotLoaded => println!("  State: Not Loaded"),
            //     LoadState::Loading => println!("  State: Loading..."),
            //     LoadState::Loaded => println!("  State: Loaded"),
            //     LoadState::Failed => println!("  State: Failed"),
            // }
        } else {
            println!("\n📊 Asset Info: No asset loaded");
        }
    }

    fn run(&mut self) {
        self.load_asset();
        self.display_asset_info();

        println!("\n💡 HOW TO TEST:");
        println!("  1. Create/modify 'assets/demo.txt'");
        println!("  2. Save the file");
        println!("  3. Watch for reload events in console");
        println!("\n  This is a demonstration of the hot-reload API.");
        println!("  In a full implementation with file watching:");
        println!("    • FileWatcher monitors asset directories");
        println!("    • Changes trigger AssetEvent::Modified");
        println!("    • AssetServer reloads affected assets");
        println!("    • Handles are automatically invalidated");
        println!("    • Dependent systems receive notifications\n");

        // Example of hot-reload workflow
        println!("\n📝 HOT-RELOAD WORKFLOW:");
        println!("  1. File Modified → FileWatcher detects change");
        println!("  2. AssetServer receives file event");
        println!("  3. AssetServer invalidates old handle");
        println!("  4. AssetServer loads new asset data");
        println!("  5. AssetEvent::Modified sent to subscribers");
        println!("  6. Systems update with new data");
        println!("  7. Rendering uses updated asset\n");

        // Simulate a reload event
        println!("🔄 Simulating asset reload...");
        self.reload_count += 1;
        self.on_asset_reloaded();
        self.display_asset_info();

        println!("\n✅ Hot-reload demo completed!");
        println!("   In production, this would run continuously,");
        println!("   monitoring files and reloading on changes.\n");
    }
}

fn main() {
    let mut demo = HotReloadDemo::new();
    demo.run();
}
