// Core of an Android agent app (API 26+; permissions CALL_PHONE, READ_PHONE_STATE, foreground service).
// Loop: GET /api/device/jobs/next?wait=20 -> run(steps) -> POST /api/device/jobs/{order_id}/result.
// Keep SIM_PIN in EncryptedSharedPreferences on the phone; substitute {pin} locally.
import android.content.Context
import android.os.Handler
import android.os.Looper
import android.telephony.TelephonyManager

class UssdRunner(ctx: Context) {
    private val tm = ctx.getSystemService(Context.TELEPHONY_SERVICE) as TelephonyManager
    private val main = Handler(Looper.getMainLooper())

    /** outcome: "success" | "failed" | "notsent" (safe to retry on another SIM) */
    fun run(code: String, done: (outcome: String, text: String) -> Unit) {
        tm.sendUssdRequest(code, object : TelephonyManager.UssdResponseCallback() {
            override fun onReceiveUssdResponse(t: TelephonyManager, req: String, resp: CharSequence) {
                val s = resp.toString().lowercase()
                val ok = listOf("success", "recharged", "completed").any { s.contains(it) } &&
                         listOf("fail", "insufficient", "invalid", "error").none { s.contains(it) }
                done(if (ok) "success" else "failed", resp.toString())
            }
            override fun onReceiveUssdResponseFailed(t: TelephonyManager, req: String, failureCode: Int) {
                // FAILURE_CODE_UNAVAILABLE = nothing was sent -> report failed with retryable=true.
                // Anything else is an unknown outcome: report nothing, the server escalates to manual review.
                done(if (failureCode == TelephonyManager.USSD_ERROR_SERVICE_UNAVAIL) "notsent" else "unknown", "USSD failure $failureCode")
            }
        }, main)
    }
}
// Multi-step menus (reply with 1, number, amount, PIN...) need an AccessibilityService that reads and fills the USSD dialog.