when guards

// Test 918g: Optional Branches - when Guards + |? Interaction
//
// This test demonstrates:
// 1. Using when guards for partial matching on optional branches
// 2. |? catch-all handles unguarded cases
// 3. Elegant pattern: fine-grained control without exhaustive guards

const std = @import("std");

// Event with required + optional branches
~event process { value: u32 }
| success { result: u32 }                    // REQUIRED
| ?warning { msg: []const u8, level: u32 }   // OPTIONAL with payload

~proc process {
    const doubled = value * 2;

    // Return warning with different levels based on value
    if (value > 100) {
        return .{ .warning = .{ .msg = "Very large", .level = 10 } };
    }

    if (value > 50) {
        return .{ .warning = .{ .msg = "Moderately large", .level = 4 } };
    }

    if (value > 20) {
        return .{ .warning = .{ .msg = "Slightly large", .level = 1 } };
    }

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

// Handler with when guards + |? catch-all
// - success: always handled (required)
// - warning with level > 5: critical handling
// - warning with level > 2: moderate handling
// - warning with level <= 2: caught by |? (not critical enough to care)

~process(value: 10)
| success { result } |> std.debug.print("Success: {}\n", .{result})
| warning { msg, level } when (level > 5) |> std.debug.print("CRITICAL: {s}\n", .{msg})
| warning { msg, level } when (level > 2) |> std.debug.print("Moderate: {s}\n", .{msg})
|? |> std.debug.print("Optional (ignored)\n", .{})

~process(value: 150)  // Returns warning level 10 → matches first when guard
| success { result } |> std.debug.print("Success: {}\n", .{result})
| warning { msg, level } when (level > 5) |> std.debug.print("CRITICAL: {s}\n", .{msg})
| warning { msg, level } when (level > 2) |> std.debug.print("Moderate: {s}\n", .{msg})
|? |> std.debug.print("Optional (ignored)\n", .{})

~process(value: 60)  // Returns warning level 4 → matches second when guard
| success { result } |> std.debug.print("Success: {}\n", .{result})
| warning { msg, level } when (level > 5) |> std.debug.print("CRITICAL: {s}\n", .{msg})
| warning { msg, level } when (level > 2) |> std.debug.print("Moderate: {s}\n", .{msg})
|? |> std.debug.print("Optional (ignored)\n", .{})

~process(value: 25)  // Returns warning level 1 → no guards match → caught by |?
| success { result } |> std.debug.print("Success: {}\n", .{result})
| warning { msg, level } when (level > 5) |> std.debug.print("CRITICAL: {s}\n", .{msg})
| warning { msg, level } when (level > 2) |> std.debug.print("Moderate: {s}\n", .{msg})
|? |> std.debug.print("Optional (ignored)\n", .{})