(Swift 3,4,5...) PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

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Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

Note: This functionality was introduced in Chilkat v9.5.0.87.

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let scard = CkoSCard()!

    // First establish a context to the PC/SC Resource Manager
    var success: Bool = scard.establishContext("user")
    if success == false {
        print("\(scard.lastErrorText!)")
        return
    }

    // First we'll examine the state of all connected readers to see which have smartcards already inserted..
    // Get JSON containing information about the smartcards currently inserted into readers.
    // This also includes information about USB security tokens.
    let json = CkoJsonObject()!
    success = scard.findSmartcards(json)
    if success == false {
        print("\(scard.lastErrorText!)")
        return
    }

    // When writing this example, I have 3 smart card readers plugged into my system.
    // One of them has a smart card inserted.
    // Here's the JSON returned by FindSmartcards...

    // {
    //   "reader": [
    //     {
    //       "name": "Alcor Micro USB Smart Card Reader 0",
    //       "state": "empty"
    //     },
    //     {
    //       "name": "Generic Smart Card Reader Interface 0",
    //       "state": "present",
    //       "vendorName": "Generic",
    //       "serialNumber": "3230303730383138303030303030303030",
    //       "systemName": "Generic Smart Card Reader Interface 0",
    //       "card": {
    //         "atr": "3BFC180000813180459067464A00641606F2727E00E0",
    //         "windows": {
    //           "miniDriver": "tagliov70px.dll",
    //           "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
    //           "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
    //         }
    //       }
    //     },
    //     {
    //       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
    //       "state": "empty"
    //     }
    //   ]
    // }

    json.emitCompact = false
    print("\(json.emit()!)")
    print(" ")

    // We can iterate over the JSON to find the readers with a smart card already inserted..
    var name: String?
    let sbState = CkoStringBuilder()!

    var i: Int = 0
    var count_i: Int = json.size(ofArray: "reader").intValue
    while i < count_i {
        json.i = i
        name = json.string(of: "reader[i].name")

        sbState.clear()
        json.string(ofSb: "reader[i].state", sb: sbState)

        if sbState.contains("present", caseSensitive: true) == true {
            print("\(name!) has a smart card inserted.")
        }
        else {
            print("\(name!) does not have a smart card inserted.")
        }

        i = i + 1
    }

    print(" ")

    // Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

    // Get the list of all readers.
    let stReaders = CkoStringTable()!
    success = scard.listReaders(stReaders)
    if success == false {
        print("\(scard.lastErrorText!)")
        return
    }

    // Show the reader names..
    var numReaders: Int = stReaders.count.intValue
    i = 0
    while i < numReaders {
        print("\(i): \(stReaders.string(at: i)!)")
        i = i + 1
    }

    // Sample output from the above loop.
    // 0: Alcor Micro USB Smart Card Reader 0
    // 1: Generic Smart Card Reader Interface 0
    // 2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
    // 

    // Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
    let json2 = CkoJsonObject()!
    success = scard.getStatusChange(30000, stReaderNames: stReaders, json: json2)
    if success == false {
        print("\(scard.lastErrorText!)")
        return
    }

    print(" ")

    // Let's see what happened...
    json2.emitCompact = false
    print("\(json2.emit()!)")
    print(" ")

    // This is what json2 contains.
    // A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
    // The "numChanged" indicates that one reader's status changed.  
    // The "changed":true indicates the reader that changed.   The state is now "present".

    // {
    //   "numChanged": 1,
    //   "reader": [
    //     {
    //       "name": "Alcor Micro USB Smart Card Reader 0",
    //       "changed": false,
    //       "state": "empty"
    //     },
    //     {
    //       "name": "Generic Smart Card Reader Interface 0",
    //       "changed": false,
    //       "state": "present",
    //       "atr": "3BFC180000813180459067464A00641606F2727E00E0"
    //     },
    //     {
    //       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
    //       "changed": true,
    //       "state": "present",
    //       "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
    //     }
    //   ]
    // }

    // Find the reader that changed...
    var changed: Bool
    var state: String?
    var atr: String?

    var numChanged: Int = json2.int(of: "numChanged").intValue
    print("number of readers with a changed state: \(numChanged)")

    i = 0
    count_i = json2.size(ofArray: "reader").intValue
    while i < count_i {
        json2.i = i
        changed = json2.bool(of: "reader[i].changed")
        if changed == true {
            name = json2.string(of: "reader[i].name")
            state = json2.string(of: "reader[i].state")

            print("Changed: ")
            print("    reader name: \(name!)")
            print("    new state: \(state!)")

            // If a card is now in this reader, we should have the ATR of the card..
            if json2.hasMember("reader[i].atr") == true {
                atr = json2.string(of: "reader[i].atr")
                print("    ATR of card inserted into this reader: \(atr!)")
            }

        }

        i = i + 1
    }

    // The output from the above loop:

    // number of readers with a changed state: 1
    // Changed: 
    //     reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
    //     new state: present
    //     ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

    // Applications should always release the context when finished.
    success = scard.releaseContext()
    if success == false {
        print("\(scard.lastErrorText!)")
    }


}