DeviceMemoryModule.swift

import Foundation

/// Exposes the REAL per-process memory budget to JS — not a fraction-of-total-RAM
/// guess. `os_proc_available_memory()` returns how many bytes this process can
/// still allocate before jetsam kills it, and it already reflects the
/// increased-memory + extended-virtual-addressing entitlements. This is the only
/// number that means "the OS will actually give us this much".
@objc(DeviceMemoryModule)
class DeviceMemoryModule: NSObject {

  @objc
  static func requiresMainQueueSetup() -> Bool {
    return false
  }

  @objc
  func getMemoryInfo(_ resolve: @escaping RCTPromiseResolveBlock,
                     rejecter reject: @escaping RCTPromiseRejectBlock) {
    // Live headroom before this process is jetsam-killed (bytes). iOS 13+ only.
    var availableBytes = 0
    #if os(iOS)
    if #available(iOS 13.0, *) {
      availableBytes = os_proc_available_memory()
    }
    #endif

    // Current physical footprint (bytes) — useful for diagnostics / the warning UI.
    var footprintBytes: UInt64 = 0
    var info = task_vm_info_data_t()
    var count = mach_msg_type_number_t(
      MemoryLayout<task_vm_info_data_t>.size / MemoryLayout<integer_t>.size)
    let kr = withUnsafeMutablePointer(to: &info) { ptr -> kern_return_t in
      ptr.withMemoryRebound(to: integer_t.self, capacity: Int(count)) { intPtr in
        task_info(mach_task_self_, task_flavor_t(TASK_VM_INFO), intPtr, &count)
      }
    }
    if kr == KERN_SUCCESS {
      footprintBytes = info.phys_footprint
    }

    resolve([
      // The real budget: what this process may still allocate right now.
      "processAvailableBytes": NSNumber(value: Double(availableBytes)),
      "footprintBytes": NSNumber(value: Double(footprintBytes)),
      // iOS has no system-wide low-memory flag here; the available number is authoritative.
      "lowMemory": false,
    ])
  }
}