DownloadFileService.kt

package io.matchx.lpwancontroller.api

import android.app.IntentService
import android.content.Intent
import android.support.v4.content.LocalBroadcastManager
import java.io.DataInputStream
import java.io.File
import java.io.FileOutputStream
import java.net.URL


/**
 * Expects URL:
 * @param URL_PARAM
 * Uses LocalBroadcastManager to communicate download progress in bytes.
 * @see PROGRESS_INTENT_ACTION
 * @see PROGRESS_BYTES_PARAM
 * Uses LocalBroadcastManager to communicate results.
 * @see RESULT_INTENT_ACTION
 * @see RESULT_FILENAME_PARAM all good, temporary filename
 * @see RESULT_ERROR_PARAM something went wrong, exception object
 * */
class DownloadFileService : IntentService("DownloadFileService") {
    val URL_PARAM = "url"
    val PROGRESS_INTENT_ACTION = "DownloadFileService.progress"
    val PROGRESS_BYTES_PARAM = "progress.bytes"
    val RESULT_INTENT_ACTION = "DownloadFileService.result"
    val RESULT_FILENAME_PARAM = "result.filename"
    val RESULT_ERROR_PARAM = "result.error"

    private val BUFFER_SIZE = 1024

    override fun onHandleIntent(intent: Intent?) {
        if (intent == null)
            return postException(Exception("Missing intent"))
        if (!intent.hasExtra(URL_PARAM))
            return postException(Exception("Missing URL parameter"))
        try {
            downloadFile(intent.getStringExtra(URL_PARAM))
        } catch (e: Exception) {
            postException(e)
        }
    }

    private fun downloadFile(url: String) {
        val tmpfile = File.createTempFile("download-", null)
        FileOutputStream(tmpfile).use { ostream ->
            DataInputStream(URL(url).openStream()).use { istream ->
                val buffer = ByteArray(BUFFER_SIZE)
                var bytesRead: Int
                bytesRead = istream.read(buffer)
                while (bytesRead != -1) {
                    ostream.write(buffer, 0, bytesRead)
                    postProgress(bytesRead)
                    bytesRead = istream.read(buffer)
                }
                postDone(tmpfile.canonicalPath)
            }
        }
    }

    private fun postException(e: Exception) {
        val intent = Intent(RESULT_INTENT_ACTION)
        intent.putExtra(RESULT_ERROR_PARAM, e)
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent)
    }

    private fun postProgress(bytes: Int) {
        val intent = Intent(PROGRESS_INTENT_ACTION)
        intent.putExtra(PROGRESS_BYTES_PARAM, bytes)
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent)
    }

    private fun postDone(filename: String) {
        val intent = Intent(RESULT_INTENT_ACTION)
        intent.putExtra(RESULT_FILENAME_PARAM, filename)
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent)
    }
}