Add interactive mode

Calling psdk without arguments will now trigger the interactive mode.

There are a few pre-conditions:
 - empty disk available: asks if the user wants to initialize the disk
   and configure the SDK to use it.
 - persistent disk available, but not in use: asks if the user wants to
   configure the SDK to use the persistent disk.
 - persistent disk in use: no actions allowed

This patch also includes the file data/psdk.desktop which creates a
desktop icon when copied to ~/Desktop.

Signed-off-by: Peter Senna Tschudin <peter.senna@collabora.com>

data/psdk.desktop

+[Desktop Entry]
+Version=1.0
+Name=Persistent Disk Setup
+Exec=/usr/bin/psdk
+Icon=drive-harddisk
+Terminal=true
+Type=Application
+Categories=System
+StartupNotify=false

tools/psdk

@@ -27,6 +27,8 @@ import errno
 
 BKP_EXTENSION = ".PSDK"
 DISK_LABEL = "sdk-persistent"
+DISK_MIN_SIZE = 17 # 20 - 20*10% - 1
+HELP_LINK = "https://developer.apertis.org/latest/sdk-usage.html"
 MOUNT_POINT = "/run/media/persistent"
 PERSISTENT_ETC_PREFIX = "/home"
 
@@ -443,6 +445,57 @@ def scan_persistent_etc():
     for line in result.stdout.decode().splitlines():
         persistent_to_conf(line)
 
+def menu(empty_disk_found=False, pdisk_found=False, pdisk_in_use=False):
+    """Menu for user interaction"""
+
+    print("Persistent disk setup")
+    print("\nFor help visit:\n\t" + HELP_LINK)
+    print("\nStatus:")
+
+    if pdisk_in_use:
+        print("\tPersistent disk in use: {}".format(str(pdisk_in_use)))
+        print("\nThis SDK is currently using the persistent disk. No further action required.")
+        input("\nPress enter to exit")
+        return False
+
+    if (not pdisk_found) and (not empty_disk_found):
+        print("\nNo disk found to use as persistent storage.")
+        input("\nPress enter to exit")
+        return False
+
+    if empty_disk_found:
+        print("\tEmpty disk found: {}".format(str(empty_disk_found)))
+        answer = input("\nDo you want to initialize the empty disk {} ".format(empty_disk_found) +
+                       "and configure the SDK to use it as persistent disk?\n" +
+                       "(yes and press enter): ")
+
+        if answer == "yes":
+            disk = Disk(empty_disk_found, DISK_LABEL)
+            disk.initialize()
+            configure_sdk()
+
+            input("Disk initialization completed. Press enter to reboot the SDK.")
+            command = ["sudo", "reboot"]
+            _run(command)
+
+            return True
+
+    if pdisk_found:
+        print("\tPersistent disk in use: {}".format(str(pdisk_in_use)))
+        print("\tPersistent disk found: {}".format(str(pdisk_found)))
+        answer = input("\nDo you want to configure the SDK to use the persistent " +
+                       "disk {}?\n".format(pdisk_found) +
+                       "(yes and press enter): ")
+
+        if answer == "yes":
+            configure_sdk()
+
+            input("SDK configuration completed. Press enter to reboot the SDK.")
+            command = ["sudo", "reboot"]
+            _run(command)
+
+            return True
+
 def persistent_disk_in_use():
     """Is the persistent disk in use?"""
 
@@ -461,9 +514,50 @@ def persistent_disk_in_use():
 
     return persistent_disk
 
+
+def empty_disk(min_size=DISK_MIN_SIZE):
+    """Find an empty disk with at least min_size"""
+
+    command = ["sudo", "fdisk", "-l"]
+    result = _run(command)
+
+    for line in result.stdout.decode().splitlines():
+        if "Disk /dev" in line:
+            disk = "/dev/" + re.findall(r"Disk /dev/([A-Za-z]+)", line)[0]
+            size = re.findall(r"Disk /dev/[A-Za-z]+\: ([0-9\.]+)", line)[0]
+            if disk_valid(disk) and disk_empty(disk):
+                size = int(float(size))
+                if size >= min_size:
+                    return disk
+
+    return False
+
+def probe_disks():
+    """Look for disks that are currently available to check for empty_disk_found,
+    pdisk_found, and pdisk_in_use"""
+
+    empty_disk_found = empty_disk()
+    pdisk_in_use = persistent_disk_in_use()
+
+    # Persistent disk found?
+    pdisk_found = False
+    persistent_disk_link = "/dev/disk/by-label/" + DISK_LABEL
+    if os.path.islink(persistent_disk_link):
+        pdisk_found = os.readlink(persistent_disk_link)
+        pdisk_found = "/dev/" + os.path.split(pdisk_found)[1]
+
+    return empty_disk_found, pdisk_found, pdisk_in_use
+
 def main():
     """good old main"""
 
+    if len(sys.argv) == 1:
+        # Interactive mode
+
+        empty_disk_found, pdisk_found, pdisk_in_use = probe_disks()
+        menu(empty_disk_found, pdisk_found, pdisk_in_use)
+        sys.exit()
+
     parser = argparse.ArgumentParser()
     etc_group = parser.add_argument_group("Configuration files management")
     disk_group = parser.add_argument_group("Persistent disk management")