008 complex flow test

// Test: Complex flow with chained events and mocks
//
// This is the REAL test of the testing framework:
// - Real program events defined outside tests
// - Subflow chains multiple events together
// - Tests mock impure events, call real flows
// - Pure events called directly (no mock needed)

~import "$std/testing"

// ============================================
// THE ACTUAL PROGRAM
// ============================================

// Database layer (impure - external DB)
~event db.get_user { id: u32 }
| found { id: u32, balance: u32 }
| not_found

// Payment service (impure - external API)
~event payment.charge { user_id: u32, amount: u32 }
| success { transaction_id: []const u8 }
| failed { reason: []const u8 }

// Pure validation (no side effects)
~event validate.amount { amount: u32, balance: u32 }
| valid
| insufficient

~[pure] proc validate.amount {
    if (amount <= balance) {
        return .{ .valid = .{} };
    } else {
        return .{ .insufficient = .{} };
    }
}

// The main flow - chains everything together
~event process_payment { user_id: u32, amount: u32 }
| success { transaction_id: []const u8 }
| user_not_found
| insufficient_funds

~process_payment = db.get_user(id: user_id)
| found u |> validate.amount(amount: amount, balance: u.balance)
    | valid |> payment.charge(user_id: u.id, amount: amount)
        | success tx |> success { transaction_id: tx.transaction_id }
        | failed _ |> insufficient_funds
    | insufficient |> insufficient_funds
| not_found |> user_not_found

// ============================================
// THE TESTS
// ============================================

~test(Successful payment) {
    ~db.get_user = found { id: 42, balance: 100 }
    ~payment.charge = success { transaction_id: "tx123" }

    ~process_payment(user_id: 42, amount: 50)
    | success s |> assert(s.transaction_id.len == 5)  // "tx123" has 5 chars
}

~test(Insufficient funds rejected) {
    ~db.get_user = found { id: 42, balance: 30 }

    ~process_payment(user_id: 42, amount: 50)
    | insufficient_funds |> assert.ok()
}

~test(User not found) {
    ~db.get_user = not_found

    ~process_payment(user_id: 999, amount: 50)
    | user_not_found |> assert.ok()
}