[taler-merchant-terminal-android] 09/19: Factor out NFC code from MainActivity

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torsten-grote pushed a commit to branch master
in repository merchant-terminal-android.

commit f5740d3c47993577796c43fac068fff9141af3a2
Author: Torsten Grote <address@hidden>
AuthorDate: Mon Feb 3 10:23:50 2020 -0300

    Factor out NFC code from MainActivity
---
 .../java/net/taler/merchantpos/MainActivity.kt     | 283 +++------------------
 .../main/java/net/taler/merchantpos/NfcManager.kt  | 189 ++++++++++++++
 app/src/main/java/net/taler/merchantpos/Utils.kt   |  36 +++
 3 files changed, 262 insertions(+), 246 deletions(-)

diff --git a/app/src/main/java/net/taler/merchantpos/MainActivity.kt 
b/app/src/main/java/net/taler/merchantpos/MainActivity.kt
index 57968c3..9841339 100644
--- a/app/src/main/java/net/taler/merchantpos/MainActivity.kt
+++ b/app/src/main/java/net/taler/merchantpos/MainActivity.kt
@@ -1,285 +1,68 @@
 package net.taler.merchantpos
 
 import android.nfc.NfcAdapter
-import android.nfc.Tag
-import android.nfc.tech.IsoDep
 import android.os.Bundle
-import android.util.Log
 import android.view.MenuItem
 import androidx.activity.viewModels
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
-import androidx.core.view.GravityCompat
+import androidx.core.view.GravityCompat.START
 import androidx.drawerlayout.widget.DrawerLayout
+import androidx.lifecycle.Observer
 import androidx.navigation.NavController
 import androidx.navigation.findNavController
 import androidx.navigation.ui.AppBarConfiguration
 import androidx.navigation.ui.setupWithNavController
 import com.google.android.material.navigation.NavigationView
-import net.taler.merchantpos.Utils.Companion.hexStringToByteArray
-import org.json.JSONObject
-import java.io.ByteArrayOutputStream
-import java.net.URL
-import javax.net.ssl.HttpsURLConnection
+import 
com.google.android.material.navigation.NavigationView.OnNavigationItemSelectedListener
 
-
-class Utils {
-    companion object {
-        private val HEX_CHARS = "0123456789ABCDEF"
-        fun hexStringToByteArray(data: String): ByteArray {
-
-            val result = ByteArray(data.length / 2)
-
-            for (i in 0 until data.length step 2) {
-                val firstIndex = HEX_CHARS.indexOf(data[i]);
-                val secondIndex = HEX_CHARS.indexOf(data[i + 1]);
-
-                val octet = firstIndex.shl(4).or(secondIndex)
-                result.set(i.shr(1), octet.toByte())
-            }
-
-            return result
-        }
-
-        private val HEX_CHARS_ARRAY = "0123456789ABCDEF".toCharArray()
-        fun toHex(byteArray: ByteArray): String {
-            val result = StringBuffer()
-
-            byteArray.forEach {
-                val octet = it.toInt()
-                val firstIndex = (octet and 0xF0).ushr(4)
-                val secondIndex = octet and 0x0F
-                result.append(HEX_CHARS_ARRAY[firstIndex])
-                result.append(HEX_CHARS_ARRAY[secondIndex])
-            }
-
-            return result.toString()
-        }
-    }
-}
-
-val TALER_AID = "A0000002471001"
-
-
-fun writeApduLength(stream: ByteArrayOutputStream, size: Int) {
-    when {
-        size == 0 -> {
-            // No size field needed!
-        }
-        size <= 255 -> // One byte size field
-            stream.write(size)
-        size <= 65535 -> {
-            stream.write(0)
-            // FIXME: is this supposed to be little or big endian?
-            stream.write(size and 0xFF)
-            stream.write((size ushr 8) and 0xFF)
-        }
-        else -> throw Error("payload too big")
-    }
-}
-
-fun apduSelectFile(): ByteArray {
-    return hexStringToByteArray("00A4040007A0000002471001")
-}
-
-
-fun apduPutData(payload: ByteArray): ByteArray {
-    val stream = ByteArrayOutputStream()
-
-    // Class
-    stream.write(0x00)
-
-    // Instruction 0xDA = put data
-    stream.write(0xDA)
-
-    // Instruction parameters
-    // (proprietary encoding)
-    stream.write(0x01)
-    stream.write(0x00)
-
-    writeApduLength(stream, payload.size)
-
-    stream.write(payload)
-
-    return stream.toByteArray()
-}
-
-fun apduPutTalerData(talerInst: Int, payload: ByteArray): ByteArray {
-    val realPayload = ByteArrayOutputStream()
-    realPayload.write(talerInst)
-    realPayload.write(payload)
-    return apduPutData(realPayload.toByteArray())
-}
-
-fun apduGetData(): ByteArray {
-    val stream = ByteArrayOutputStream()
-
-    // Class
-    stream.write(0x00)
-
-    // Instruction 0xCA = get data
-    stream.write(0xCA)
-
-    // Instruction parameters
-    // (proprietary encoding)
-    stream.write(0x01)
-    stream.write(0x00)
-
-    // Max expected response size, two
-    // zero bytes denotes 65536
-    stream.write(0x0)
-    stream.write(0x0)
-
-    return stream.toByteArray()
-}
-
-
-class MainActivity : AppCompatActivity(), 
NavigationView.OnNavigationItemSelectedListener,
-    NfcAdapter.ReaderCallback {
-
-    companion object {
-        const val TAG = "taler-merchant"
-    }
+class MainActivity : AppCompatActivity(), OnNavigationItemSelectedListener {
 
     private val model: MainViewModel by viewModels()
+    private val nfcManager = NfcManager()
     private var nfcAdapter: NfcAdapter? = null
 
-    private var currentTag: IsoDep? = null
-
-    override fun onTagDiscovered(tag: Tag?) {
-
-        Log.v(TAG, "tag discovered")
-
-        val isoDep = IsoDep.get(tag)
-        isoDep.connect()
-
-        currentTag = isoDep
-
-        isoDep.transceive(apduSelectFile())
-
-        val contractUri: String? = 
model.paymentManager.payment.value?.talerPayUri
-
-        if (contractUri != null) {
-            isoDep.transceive(apduPutTalerData(1, contractUri.toByteArray()))
-        }
-
-        // FIXME: use better pattern for sleeps in between requests
-        // -> start with fast polling, poll more slowly if no requests are 
coming
-
-        while (true) {
-            try {
-                val reqFrame = isoDep.transceive(apduGetData())
-                if (reqFrame.size < 2) {
-                    Log.v(TAG, "request frame too small")
-                    break
-                }
-                val req = ByteArray(reqFrame.size - 2)
-                if (req.isEmpty()) {
-                    continue
-                }
-                reqFrame.copyInto(req, 0, 0, reqFrame.size - 2)
-                val jsonReq = JSONObject(req.toString(Charsets.UTF_8))
-                val reqId = jsonReq.getInt("id")
-                Log.v(TAG, "got request $jsonReq")
-                val jsonInnerReq = jsonReq.getJSONObject("request")
-                val method = jsonInnerReq.getString("method")
-                val urlStr = jsonInnerReq.getString("url")
-                Log.v(TAG, "url '$urlStr'")
-                Log.v(TAG, "method '$method'")
-                val url = URL(urlStr)
-                val conn: HttpsURLConnection = url.openConnection() as 
HttpsURLConnection
-                conn.setRequestProperty("Accept", "application/json")
-                conn.connectTimeout = 5000
-                conn.doInput = true
-                when (method)  {
-                    "get" -> {
-                        conn.requestMethod = "GET"
-                    }
-                    "postJson" -> {
-                        conn.requestMethod = "POST"
-                        conn.doOutput = true
-                        conn.setRequestProperty("Content-Type", 
"application/json; utf-8")
-                        val body =  jsonInnerReq.getString("body")
-                        
conn.outputStream.write(body.toByteArray(Charsets.UTF_8))
-                    }
-                    else -> {
-                        throw Exception("method not supported")
-                    }
-                }
-                Log.v(TAG, "connecting")
-                conn.connect()
-                Log.v(TAG, "connected")
-
-                val statusCode = conn.responseCode
-                val tunnelResp = JSONObject()
-                tunnelResp.put("id", reqId)
-                tunnelResp.put("status", conn.responseCode)
-
-                if (statusCode == 200) {
-                    val stream = conn.inputStream
-                    val httpResp = stream.buffered().readBytes()
-                    tunnelResp.put("responseJson", 
JSONObject(httpResp.toString(Charsets.UTF_8)))
-                }
-
-                Log.v(TAG, "sending: $tunnelResp")
-
-                isoDep.transceive(apduPutTalerData(2, 
tunnelResp.toString().toByteArray()))
-            } catch (e: Exception) {
-                Log.v(TAG, "exception during NFC loop: ${e}")
-                break
-            }
-        }
-
-        isoDep.close()
-    }
-
-    public override fun onResume() {
-        super.onResume()
-        nfcAdapter?.enableReaderMode(
-            this, this,
-            NfcAdapter.FLAG_READER_NFC_A or
-                    NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK,
-            null
-        )
-    }
-
-    public override fun onPause() {
-        super.onPause()
-        nfcAdapter?.disableReaderMode(this)
-    }
+    private lateinit var drawerLayout: DrawerLayout
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
 
         nfcAdapter = NfcAdapter.getDefaultAdapter(this)
+        model.paymentManager.payment.observe(this, Observer { payment ->
+            payment?.talerPayUri?.let {
+                nfcManager.setContractUri(it)
+            }
+        })
 
-        setContentView(R.layout.activity_main)
         val toolbar: Toolbar = findViewById(R.id.toolbar)
         setSupportActionBar(toolbar)
 
-        val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
+        drawerLayout = findViewById(R.id.drawer_layout)
         val navView: NavigationView = findViewById(R.id.nav_view)
 
         navView.setNavigationItemSelectedListener(this)
 
         val navController = findNavController(R.id.nav_host_fragment)
         val appBarConfiguration = AppBarConfiguration(
-                setOf(
-                    R.id.order,
-                    R.id.merchantSettings,
-                    R.id.merchantHistory
-                ), drawerLayout
-            )
+            setOf(
+                R.id.order,
+                R.id.merchantSettings,
+                R.id.merchantHistory
+            ), drawerLayout
+        )
         toolbar.setupWithNavController(navController, appBarConfiguration)
     }
 
-    override fun onBackPressed() {
-        val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
-        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
-            drawerLayout.closeDrawer(GravityCompat.START)
-        } else {
-            super.onBackPressed()
-        }
+    public override fun onResume() {
+        super.onResume()
+        // TODO should we only read tags when a payment is to be made?
+        nfcAdapter?.enableReaderMode(this, nfcManager, nfcManager.flags, null)
+    }
+
+    public override fun onPause() {
+        super.onPause()
+        nfcAdapter?.disableReaderMode(this)
     }
 
     override fun onNavigationItemSelected(item: MenuItem): Boolean {
@@ -291,8 +74,16 @@ class MainActivity : AppCompatActivity(), 
NavigationView.OnNavigationItemSelecte
             R.id.nav_settings -> 
nav.navigate(R.id.action_global_merchantSettings)
         }
         val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
-        drawerLayout.closeDrawer(GravityCompat.START)
+        drawerLayout.closeDrawer(START)
         return true
     }
 
+    override fun onBackPressed() {
+        if (drawerLayout.isDrawerOpen(START)) {
+            drawerLayout.closeDrawer(START)
+        } else {
+            super.onBackPressed()
+        }
+    }
+
 }
diff --git a/app/src/main/java/net/taler/merchantpos/NfcManager.kt 
b/app/src/main/java/net/taler/merchantpos/NfcManager.kt
new file mode 100644
index 0000000..083586f
--- /dev/null
+++ b/app/src/main/java/net/taler/merchantpos/NfcManager.kt
@@ -0,0 +1,189 @@
+package net.taler.merchantpos
+
+import android.nfc.NfcAdapter
+import android.nfc.NfcAdapter.FLAG_READER_NFC_A
+import android.nfc.NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK
+import android.nfc.Tag
+import android.nfc.tech.IsoDep
+import android.util.Log
+import net.taler.merchantpos.Utils.hexStringToByteArray
+import org.json.JSONObject
+import java.io.ByteArrayOutputStream
+import java.net.URL
+import javax.net.ssl.HttpsURLConnection
+
+class NfcManager : NfcAdapter.ReaderCallback {
+
+    companion object {
+        const val TAG = "taler-merchant"
+    }
+
+    val TALER_AID = "A0000002471001"
+    val flags = FLAG_READER_NFC_A or FLAG_READER_SKIP_NDEF_CHECK
+
+    private var contractUri: String? = null
+    private var currentTag: IsoDep? = null
+
+    fun setContractUri(contractUri: String) {
+        this.contractUri = contractUri
+    }
+
+    override fun onTagDiscovered(tag: Tag?) {
+
+        Log.v(TAG, "tag discovered")
+
+        val isoDep = IsoDep.get(tag)
+        isoDep.connect()
+
+        currentTag = isoDep
+
+        isoDep.transceive(apduSelectFile())
+
+        val contractUri: String? = contractUri
+
+        if (contractUri != null) {
+            isoDep.transceive(apduPutTalerData(1, contractUri.toByteArray()))
+        }
+
+        // FIXME: use better pattern for sleeps in between requests
+        // -> start with fast polling, poll more slowly if no requests are 
coming
+
+        while (true) {
+            try {
+                val reqFrame = isoDep.transceive(apduGetData())
+                if (reqFrame.size < 2) {
+                    Log.v(TAG, "request frame too small")
+                    break
+                }
+                val req = ByteArray(reqFrame.size - 2)
+                if (req.isEmpty()) {
+                    continue
+                }
+                reqFrame.copyInto(req, 0, 0, reqFrame.size - 2)
+                val jsonReq = JSONObject(req.toString(Charsets.UTF_8))
+                val reqId = jsonReq.getInt("id")
+                Log.v(TAG, "got request $jsonReq")
+                val jsonInnerReq = jsonReq.getJSONObject("request")
+                val method = jsonInnerReq.getString("method")
+                val urlStr = jsonInnerReq.getString("url")
+                Log.v(TAG, "url '$urlStr'")
+                Log.v(TAG, "method '$method'")
+                val url = URL(urlStr)
+                val conn: HttpsURLConnection = url.openConnection() as 
HttpsURLConnection
+                conn.setRequestProperty("Accept", "application/json")
+                conn.connectTimeout = 5000
+                conn.doInput = true
+                when (method) {
+                    "get" -> {
+                        conn.requestMethod = "GET"
+                    }
+                    "postJson" -> {
+                        conn.requestMethod = "POST"
+                        conn.doOutput = true
+                        conn.setRequestProperty("Content-Type", 
"application/json; utf-8")
+                        val body = jsonInnerReq.getString("body")
+                        
conn.outputStream.write(body.toByteArray(Charsets.UTF_8))
+                    }
+                    else -> {
+                        throw Exception("method not supported")
+                    }
+                }
+                Log.v(TAG, "connecting")
+                conn.connect()
+                Log.v(TAG, "connected")
+
+                val statusCode = conn.responseCode
+                val tunnelResp = JSONObject()
+                tunnelResp.put("id", reqId)
+                tunnelResp.put("status", conn.responseCode)
+
+                if (statusCode == 200) {
+                    val stream = conn.inputStream
+                    val httpResp = stream.buffered().readBytes()
+                    tunnelResp.put("responseJson", 
JSONObject(httpResp.toString(Charsets.UTF_8)))
+                }
+
+                Log.v(TAG, "sending: $tunnelResp")
+
+                isoDep.transceive(apduPutTalerData(2, 
tunnelResp.toString().toByteArray()))
+            } catch (e: Exception) {
+                Log.v(TAG, "exception during NFC loop: $e")
+                break
+            }
+        }
+
+        isoDep.close()
+    }
+
+    private fun writeApduLength(stream: ByteArrayOutputStream, size: Int) {
+        when {
+            size == 0 -> {
+                // No size field needed!
+            }
+            size <= 255 -> // One byte size field
+                stream.write(size)
+            size <= 65535 -> {
+                stream.write(0)
+                // FIXME: is this supposed to be little or big endian?
+                stream.write(size and 0xFF)
+                stream.write((size ushr 8) and 0xFF)
+            }
+            else -> throw Error("payload too big")
+        }
+    }
+
+    private fun apduSelectFile(): ByteArray {
+        return hexStringToByteArray("00A4040007A0000002471001")
+    }
+
+    private fun apduPutData(payload: ByteArray): ByteArray {
+        val stream = ByteArrayOutputStream()
+
+        // Class
+        stream.write(0x00)
+
+        // Instruction 0xDA = put data
+        stream.write(0xDA)
+
+        // Instruction parameters
+        // (proprietary encoding)
+        stream.write(0x01)
+        stream.write(0x00)
+
+        writeApduLength(stream, payload.size)
+
+        stream.write(payload)
+
+        return stream.toByteArray()
+    }
+
+    private fun apduPutTalerData(talerInst: Int, payload: ByteArray): 
ByteArray {
+        val realPayload = ByteArrayOutputStream()
+        realPayload.write(talerInst)
+        realPayload.write(payload)
+        return apduPutData(realPayload.toByteArray())
+    }
+
+    private fun apduGetData(): ByteArray {
+        val stream = ByteArrayOutputStream()
+
+        // Class
+        stream.write(0x00)
+
+        // Instruction 0xCA = get data
+        stream.write(0xCA)
+
+        // Instruction parameters
+        // (proprietary encoding)
+        stream.write(0x01)
+        stream.write(0x00)
+
+        // Max expected response size, two
+        // zero bytes denotes 65536
+        stream.write(0x0)
+        stream.write(0x0)
+
+        return stream.toByteArray()
+    }
+
+}
\ No newline at end of file
diff --git a/app/src/main/java/net/taler/merchantpos/Utils.kt 
b/app/src/main/java/net/taler/merchantpos/Utils.kt
new file mode 100644
index 0000000..b43bc25
--- /dev/null
+++ b/app/src/main/java/net/taler/merchantpos/Utils.kt
@@ -0,0 +1,36 @@
+package net.taler.merchantpos
+
+object Utils {
+
+    private const val HEX_CHARS = "0123456789ABCDEF"
+
+    fun hexStringToByteArray(data: String): ByteArray {
+        val result = ByteArray(data.length / 2)
+
+        for (i in data.indices step 2) {
+            val firstIndex = HEX_CHARS.indexOf(data[i])
+            val secondIndex = HEX_CHARS.indexOf(data[i + 1])
+
+            val octet = firstIndex.shl(4).or(secondIndex)
+            result[i.shr(1)] = octet.toByte()
+        }
+        return result
+    }
+
+
+    private val HEX_CHARS_ARRAY = "0123456789ABCDEF".toCharArray()
+
+    fun toHex(byteArray: ByteArray): String {
+        val result = StringBuffer()
+
+        byteArray.forEach {
+            val octet = it.toInt()
+            val firstIndex = (octet and 0xF0).ushr(4)
+            val secondIndex = octet and 0x0F
+            result.append(HEX_CHARS_ARRAY[firstIndex])
+            result.append(HEX_CHARS_ARRAY[secondIndex])
+        }
+        return result.toString()
+    }
+
+}

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