package com.example.checkout

import org.json.JSONObject
import java.text.ParsePosition
import java.text.SimpleDateFormat
import java.util.Locale

// Reject malformed/expired instructions before an SDK launch. No provider signing here.
fun requireUsableInvocation(invocation: JSONObject, kind: String) {
    require(invocation.getString("kind") == kind) { "Unexpected invocation kind" }
    val timestamp = invocation.getString("expires_at")
    val pattern = Regex("^(\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2})(?:\\.\\d+)?(Z|[+-]\\d{2}:\\d{2})$")
    val parts = pattern.matchEntire(timestamp) ?: error("Invalid invocation expiry")
    // Dropping subsecond precision makes this check conservative by less than one second.
    val offset = if (parts.groupValues[2] == "Z") "+0000" else parts.groupValues[2].replace(":", "")
    val normalized = parts.groupValues[1] + offset
    val formatter = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.US).apply { isLenient = false }
    val position = ParsePosition(0)
    val expiry = formatter.parse(normalized, position)
    require(expiry != null && position.index == normalized.length && expiry.time > System.currentTimeMillis()) {
        "Invalid or expired payment instructions; check the original order"
    }
}