Add check for dependecies

src/main.rs

@@ -1,5 +1,6 @@
 use chrono::prelude::*;
 use chrono::Duration;
+use std::io::Error;
 use std::io::{stdout, Result, StdoutLock, Write};
 use std::process::{Command, Output};
 use std::thread::sleep;
@@ -10,10 +11,28 @@ fn main() {
     run().unwrap();
 }
 
+/// Check if kdialog exists. If not, print message and return Err()
+fn check_deps() -> Result<()> {
+    let cmd = Command::new("sh").arg("-c").arg("kdialog").status()?;
+    if !cmd.success() {
+        println!("Could not find command 'kdialog'. Please install first, then start again");
+        return Err(Error::new(
+            std::io::ErrorKind::Other,
+            "Could not find kdialog",
+        ));
+    }
+    return Ok(());
+}
+
 /// Runs the application
 ///
 /// Default time settings are 25 minutes for a working block and 5 minutes for a break.
 fn run() -> Result<()> {
+    if check_deps().is_err() {
+        // terminate gracefully
+        return Ok(());
+    }
+
     let work_duration = Duration::seconds(if cfg!(debug_assertions) { 75 } else { 25 * 60 });
     let break_duration = Duration::seconds(if cfg!(debug_assertions) { 5 } else { 5 * 60 });