003 pattern dispatch

// Test: Pattern branch dispatch
//
// Pattern branches should dispatch based on matching the pattern against
// the event's return value. This test uses actual pattern branch syntax.
//
// The transform should:
// 1. Detect pattern branches (branch name starts with '[')
// 2. Parse the pattern to extract method + path template
// 3. Generate dispatch code that matches against the payload
// 4. Extract path params into the binding

~import "$std/io"

const std = @import("std");

// Request type - the payload we're matching against
pub const Request = struct {
    method: []const u8,
    path: []const u8,
};

// Params extracted from path
pub const Params = struct {
    id: ?[]const u8 = null,
};

// Event that returns a request
~pub event incoming {}
| request Request

~proc incoming {
    return .{ .request = .{ .method = "GET", .path = "/users/42" } };
}

// This is what we WANT to work:
// Pattern branches dispatch based on matching method + path
~incoming()
| [GET /users/:id] p |> std.io:print.ln("user id: {{ p.id:s }}")
| [GET /health] _ |> std.io:print.ln("health check")
| [POST /users] _ |> std.io:print.ln("create user")
| [*] _ |> std.io:print.ln("not found")