app/src/main/kotlin/de/jotoho/waituntil/start.kt

@@ -1,9 +1,64 @@
 package de.jotoho.waituntil
 
+import java.util.Locale;
+import java.util.Locale.LanguageRange;
+import java.text.DateFormat;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
+import java.util.Date;
+import java.util.TimeZone
+import java.time.Instant;
+import java.time.LocalTime;
+import java.time.LocalDate;
+import java.time.ZonedDateTime;
+import java.time.temporal.ChronoUnit
+
 // This file contains the main function and other utility function necessary for interpreting the terminal arguments.
 // See README.md and LICENSE.md for license information
 // Author: Jonas Tobias Hopusch (@jotoho)
 
+val langGerman: String = Locale.GERMAN.getLanguage();
+val applicationOutputLanguage: String = if (Locale.getDefault().getLanguage().equals(Locale.GERMAN.getLanguage()))
+                                    Locale.GERMAN.getLanguage()
+                                    else Locale.ENGLISH.getLanguage();
+
+fun waitUntilTimeStamp(timestamp: ZonedDateTime) {
+    Thread.sleep(
+        Math.max(Instant.now().until(timestamp, ChronoUnit.MILLIS), 0)
+        );
+
+    val formattedTimeStamp: String = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
+                                        .withZone(TimeZone.getDefault().toZoneId())
+                                        .format(Instant.now());
+
+    when (applicationOutputLanguage) {
+        langGerman -> System.err.println("Erfolgreich bis $formattedTimeStamp gewartet!");
+        else -> {
+            System.err.println("Successfully waited until $formattedTimeStamp");
+        }
+    }
+}
+
+fun calculateAndAnnounceTargetTime(userTimeInputRaw: String): ZonedDateTime {
+    val userTimeInputRelative = LocalTime.parse(userTimeInputRaw);
+    val userTimeInputAbsolute = ZonedDateTime.of(LocalDate.now(), userTimeInputRelative, TimeZone.getDefault().toZoneId());
+
+    val userTimeInputFinal = if (Instant.now().isBefore(userTimeInputAbsolute.toInstant())) userTimeInputAbsolute else userTimeInputAbsolute.plusDays(1);
+
+    val formattedTimeStamp = userTimeInputFinal.format(
+        DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
+    );
+
+    when (applicationOutputLanguage) {
+        langGerman -> System.err.println("Dieses Program wird bis zum $formattedTimeStamp warten.");
+        else -> {
+            println("WaitUntil will suspend until $formattedTimeStamp");
+        }
+    }
+
+    return userTimeInputFinal;
+}
+
 fun main(args: Array<String>) {
     val optionDictionary = mapOf(Pair("-h", "--help"));
 
@@ -25,8 +80,25 @@ fun main(args: Array<String>) {
             words.add(arg);
     }
 
-    println("Content of options:");
+    if (options.contains("help")) {
-    println(options.toString());
+        when (applicationOutputLanguage) {
-    println("Content of words:");
+            langGerman -> println("Hilfe kommt noch. (Nicht implementiert)");
-    println(words.toString());
+            else -> {
+                println("Help is yet to come. (Not implemented)");
+            }
+        }
+    }
+    else if (words.size == 1) {
+        val target = calculateAndAnnounceTargetTime(words.iterator().next());
+        waitUntilTimeStamp(target);
+    }
+    else {
+        when (applicationOutputLanguage) {
+            langGerman -> System.err.println("FATAL: Es wurde exact ein nicht-flag Argument erwartet. (${words.size} erhalten)");
+            else -> {
+                System.err.println("FATAL: Expected one non-flag argument. (Got ${words.size})");
+            }
+        }
+        System.exit(1);
+    }
 }