Export to file: add a pretty CSV mode

End-users sometimes want to show their sleep log to other people, but
the data exported to a file, but that is not human-readable.

The default export format is a CSV that is meant to be easy to import
back, i.e. a machine-readable file format.

Fix the problem by adding a setting (defaults to false): if enabled, the
export result will have formatted timestamps and also the sleep length
will be written there, if if that's redundant for a machine reader.

Fixes <#515>.

app/src/main/java/hu/vmiklos/plees_tracker/DataModel.kt

@@ -303,6 +303,7 @@ object DataModel {
         uri: Uri,
         showToast: Boolean
     ) {
+        val prettyBackup = preferences.getBoolean("pretty_backup", false)
         val sleeps = database.sleepDao().getAll()
 
         try {
@@ -321,9 +322,32 @@ object DataModel {
                 return
             }
             val writer = CSVPrinter(OutputStreamWriter(os, "UTF-8"), CSVFormat.DEFAULT)
-            writer.printRecord("sid", "start", "stop", "rating", "comment")
+            if (prettyBackup) {
+                writer.printRecord("sid", "start", "stop", "length", "rating", "comment")
+            } else {
+                writer.printRecord("sid", "start", "stop", "rating", "comment")
+            }
             for (sleep in sleeps) {
-                writer.printRecord(sleep.sid, sleep.start, sleep.stop, sleep.rating, sleep.comment)
+                if (prettyBackup) {
+                    val durationMS = sleep.stop - sleep.start
+
+                    writer.printRecord(
+                        sleep.sid,
+                        DataModel.formatTimestamp(Date(sleep.start), DataModel.getCompactView()),
+                        DataModel.formatTimestamp(Date(sleep.stop), DataModel.getCompactView()),
+                        DataModel.formatDuration(durationMS / 1000, DataModel.getCompactView()),
+                        sleep.rating,
+                        sleep.comment
+                    )
+                } else {
+                    writer.printRecord(
+                        sleep.sid,
+                        sleep.start,
+                        sleep.stop,
+                        sleep.rating,
+                        sleep.comment
+                    )
+                }
             }
             writer.close()
         } catch (e: Exception) {

app/src/main/res/values/strings.xml

@@ -58,6 +58,7 @@
     </plurals>
     <string name="settings_category_backup">Backup</string>
     <string name="settings_automatic_backup">Automatic backup</string>
+    <string name="settings_pretty_backup">Pretty backup: human-readable, but can\'t be imported</string>
     <string name="settings_compact_view">Compact view: no seconds and timezone</string>
     <string name="settings_backup_path">Backup path</string>
     <string name="widget_start_stop">Toggle tracking</string>

app/src/main/res/xml/preferences.xml

@@ -22,6 +22,10 @@
         <Preference
             android:key="auto_backup_path"
             android:title="@string/settings_backup_path" />
+        <SwitchPreference
+            android:defaultValue="false"
+            android:key="pretty_backup"
+            android:title="@string/settings_pretty_backup" />
     </PreferenceCategory>
 
     <PreferenceCategory android:title="@string/settings_category_dashboard">

guide/src/usage.md

@@ -61,6 +61,9 @@ Backup settings allow you to automatically back up your sleeps after a tracking
 useful in case you selected a path which is then implicitly synchronized to some external server,
 e.g. Nextcloud.
 
+Pretty backup allows you to create a CSV file which has human-readable start, stop and length values
+during exporting to a file. This pretty output can't be imported back, though.
+
 ### Dashboard
 
 You can also customize the dashboard duration, which limits the sleeps and sleep statistics on the