inversion/examples/ScopeRegistrationDemo.vala

using Inversion;

/**
 * Example demonstrating scope-local registrations.
 * 
 * This shows how to register items directly on a scope,
 * which is useful for per-request context in web applications.
 */
public class RequestContext : Object, IRequestContext {
    public string request_id { get; set; }
    public string path { get; set; }
    
    public RequestContext(string request_id, string path) {
        this.request_id = request_id;
        this.path = path;
    }
}

public interface IRequestContext : Object {
    public abstract string request_id { get; set; }
    public abstract string path { get; set; }
}

public class RequestLogger : Object {
    private RequestContext _context;
    
    public RequestLogger(RequestContext context) {
        this._context = context;
    }
    
    public void log(string message) {
        stdout.printf("[%s] %s\n", this._context.request_id, message);
    }
}

public class RequestHandler : Object {
    private RequestContext _context;
    private RequestLogger _logger;
    
    public RequestHandler(RequestContext context, RequestLogger logger) {
        this._context = context;
        this._logger = logger;
    }
    
    public void handle() {
        this._logger.log(@"Handling request for path: $(this._context.path)");
        this._logger.log("Request completed successfully");
    }
}

public class ApplicationService : Object {
    public void do_something() {
        stdout.printf("ApplicationService doing something...\n");
    }
}

void main() {
    // Create the main container with application-wide services
    var container = new Container();
    
    // Register application-wide singleton service
    container.register_singleton<ApplicationService>((scope) => {
        return new ApplicationService();
    });
    
    // Register handler as transient - it will receive scope-local dependencies
    container.register_transient<RequestHandler>((scope) => {
        var context = scope.resolve<RequestContext>();
        var logger = scope.resolve<RequestLogger>();
        return new RequestHandler(context, logger);
    });
    
    // Register logger as transient - it will receive scope-local context
    container.register_transient<RequestLogger>((scope) => {
        var context = scope.resolve<RequestContext>();
        return new RequestLogger(context);
    });
    
    stdout.printf("=== Simulating Web Request 1 ===\n\n");
    
    // Create a scope for the first request
    var scope1 = container.create_scope();
    
    // Register request-specific context in the scope using register_local_scoped
    var context1 = new RequestContext("req-001", "/api/users");
    scope1.register_local_scoped<RequestContext>((s) => context1);
    
    // Resolve and use the handler - it gets the request-specific context
    var handler1 = scope1.resolve<RequestHandler>();
    handler1.handle();
    
    // Also resolve the application service - comes from container
    var app_service1 = scope1.resolve<ApplicationService>();
    app_service1.do_something();
    
    stdout.printf("\n=== Simulating Web Request 2 ===\n\n");
    
    // Create a separate scope for the second request
    var scope2 = container.create_scope();
    
    // Register a different context for this request
    var context2 = new RequestContext("req-002", "/api/products");
    scope2.register_local_scoped<RequestContext>((s) => context2);
    
    // This handler gets the second request's context
    var handler2 = scope2.resolve<RequestHandler>();
    handler2.handle();
    
    stdout.printf("\n=== Demonstrating Fluent API with as_type ===\n\n");
    
    // Create a scope with an instance registered against an interface
    var scope3 = container.create_scope();
    var context3 = new RequestContext("req-003", "/api/fluent");
    
    // Use fluent API to register against multiple types
    scope3.register_local_scoped<RequestContext>((s) => context3)
        .as_type(typeof(IRequestContext));  // Also register as interface
    
    // Can now resolve by either the concrete type or interface
    var by_concrete = scope3.resolve<RequestContext>();
    var by_interface = scope3.resolve<IRequestContext>();
    stdout.printf("Resolved by concrete type: %s\n", by_concrete.request_id);
    stdout.printf("Resolved by interface: %s\n", by_interface.request_id);
    // Verify they're the same underlying object
    stdout.printf("Same instance: %s\n", ((Object)by_concrete) == ((Object)by_interface) ? "yes" : "no");
    
    stdout.printf("\n=== Demonstrating Scope Isolation ===\n\n");
    
    // Create a new scope - it does NOT inherit the other scope's local registrations
    var isolated_scope = container.create_scope();
    
    // This would throw because RequestContext is not registered in isolated scope
    try {
        var handler_isolated = isolated_scope.resolve<RequestHandler>();
    } catch (Error e) {
        stdout.printf("Expected error in isolated scope: %s\n", e.message);
    }
    
    stdout.printf("\n=== Demonstrating resolve_all with Both Sources ===\n\n");
    
    // Register an additional RequestContext in scope2 using transient
    scope2.register_local_transient<RequestContext>((s) => {
        return new RequestContext("req-002-secondary", "/api/products/secondary");
    });
    
    // resolve_all returns both scope-local and container registrations
    var all_contexts = scope2.resolve_all<RequestContext>();
    stdout.printf("All RequestContext instances:\n");
    foreach (var obj in all_contexts.to_immutable_buffer()) {
        if (obj != null) {
            var ctx = (RequestContext) obj;
            stdout.printf("  - %s: %s\n", ctx.request_id, ctx.path);
        }
    }
    
    stdout.printf("\n=== Scope-Local Scoped Factory Demo ===\n\n");
    
    var scope4 = container.create_scope();
    
    // Register a scoped factory - same instance returned within the scope
    scope4.register_local_scoped<RequestContext>((s) => {
        stdout.printf("Creating scoped RequestContext...\n");
        return new RequestContext("req-004", "/api/scoped");
    });
    
    // First resolution creates the instance
    var ctx4a = scope4.resolve<RequestContext>();
    stdout.printf("First resolution: %s\n", ctx4a.request_id);
    
    // Second resolution returns the cached instance
    var ctx4b = scope4.resolve<RequestContext>();
    stdout.printf("Second resolution: %s\n", ctx4b.request_id);
    
    // Verify they're the same instance
    stdout.printf("Same instance: %s\n", ctx4a == ctx4b ? "yes" : "no");
    
    stdout.printf("\nDone!\n");
}