optional branches

// Test 918: Optional Branches - Basic |? Catch-All
//
// This test demonstrates:
// 1. Event with required and optional branches
// 2. Handler uses |? to catch all optional branches generically
// 3. Execution continues when optional branches fire (caught by |?)

const std = @import("std");

// Event with both required and optional branches
~event process { value: u32 }
| success { result: u32 }        // REQUIRED: must be handled explicitly
| ?warning { msg: []const u8 }   // OPTIONAL: can be caught by |?
| ?debug { details: []const u8 } // OPTIONAL: can be caught by |?

~proc process {
    const doubled = value * 2;

    // When value > 100, return optional warning branch
    if (value > 100) {
        return .{ .warning = .{ .msg = "Value is large" } };
    }

    // When value is odd, return optional debug branch
    if (value % 2 == 1) {
        return .{ .debug = .{ .details = "Value is odd" } };
    }

    // Otherwise return required success branch
    std.debug.print("Success: {}\n", .{doubled});
    return .{ .success = .{ .result = doubled } };
}

// Handler with |? catch-all for optional branches
// This allows execution to continue when warning or debug branches fire
~process(value: 10)   // Even value < 100 → success (handled explicitly)
| success { result } |> std.debug.print("Got success: {}\n", .{result})
|? |> std.debug.print("Got optional branch (caught by |?)\n", .{})

~process(value: 150)  // Value > 100 → warning (caught by |?)
| success { result } |> std.debug.print("Got success: {}\n", .{result})
|? |> std.debug.print("Got optional branch (caught by |?)\n", .{})

~process(value: 7)    // Odd value → debug (caught by |?)
| success { result } |> std.debug.print("Got success: {}\n", .{result})
|? |> std.debug.print("Got optional branch (caught by |?)\n", .{})