diff --git a/example.today b/example.today
new file mode 100644
index 0000000..f098ab8
--- /dev/null
+++ b/example.today
@@ -0,0 +1,44 @@
+TASK foo
+
+NOTE Spielerunde
+DATE sun 22:00 -- 24:00
+DATE sun 22:00 -- 00:00
+DATE sun 22:00 -- +2h
+DATE (wd = sun) 22:00 -- 24:00
+DATE 2021-11-07 22:00 -- 24:00; +w
+DATE 2021-11-07 22:00 -- +2h; +w
+
+NOTE daily
+DATE *
+DATE (true)
+DATE 2021-11-07; +d
+
+NOTE on weekends
+DATE (wd = sat | wd = sun)
+
+NOTE weekends
+DATE sat -- sun
+DATE 2021-11-06 -- 2021-11-07; +w
+DATE 2021-11-06 -- +d; +w
+DATE (wd = sat) -- +d
+
+NOTE last of each month
+DATE (m = 1) -d
+
+BIRTHDAY Max
+BDATE 1987-05-14
+
+BIRTHDAY Martha
+BDATE ?-09-21
+
+NOTE Physics lecture
+DATE wed 14:00 -- 15:30
+DATE 2021-05-07 14:00 -- 15:30
+FROM 2021-04-14
+UNTIL 2021-07-28
+EXCEPT 2021-05-06
+	This is a description of the event. It might mention further information
+	that doesn't fit into the title.
+
+	It may even contain multiple paragraphs, separated by an arbitrary amount
+	of empty lines, as long as every non-empty line is indented.
diff --git a/src/main.rs b/src/main.rs
index 48a0c19..9143364 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,11 @@
 use std::path::PathBuf;
+use std::process;
 
 use structopt::StructOpt;
 
+use crate::parser::Parser;
+use crate::source::SourceFiles;
+
 mod commands;
 mod parser;
 mod source;
@@ -14,5 +18,26 @@ pub struct Opt {
 
 fn main() {
     let opt = Opt::from_args();
-    println!("{:#?}", opt);
+
+    let mut files = SourceFiles::new();
+
+    let (file, content) = match files.load(&opt.file) {
+        Ok(result) => result,
+        Err(e) => {
+            eprintln!("Failed to load file: {}", e);
+            process::exit(1);
+        }
+    };
+
+    let mut parser = Parser::new(file, content);
+
+    let commands = match parser.parse() {
+        Ok(result) => result,
+        Err(es) => {
+            files.emit_all(&es);
+            process::exit(1);
+        }
+    };
+
+    println!("{:#?}", commands);
 }
diff --git a/src/parser.rs b/src/parser.rs
index f3da2ce..0fc1366 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,11 +1,23 @@
 use std::cmp::min;
 use std::process::Command;
 
+use codespan_reporting::diagnostic::{Diagnostic, Label};
+
 use crate::source::{SourceFile, SourceSpan};
 
+// TODO Add warnings for things like trailing whitespace
+
 #[derive(Debug)]
 pub struct ParseError(SourceSpan, String);
 
+impl From<&ParseError> for Diagnostic<usize> {
+    fn from(e: &ParseError) -> Self {
+        Self::error()
+            .with_message(&e.1)
+            .with_labels(vec![Label::primary(e.0.file_id(), e.0.range())])
+    }
+}
+
 type ParseResult<T> = Result<T, ParseError>;
 
 #[derive(Debug)]
@@ -102,6 +114,7 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_command(&mut self) -> ParseResult<Command> {
+        self.critical(self.offset, "idk, ded")?;
         todo!()
     }
 }
diff --git a/src/source.rs b/src/source.rs
index c7fbc6c..4674a9b 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -3,16 +3,12 @@ use std::ops::Range;
 use std::path::{Path, PathBuf};
 use std::{fs, io};
 
+use codespan_reporting::diagnostic::Diagnostic;
 use codespan_reporting::files::SimpleFiles;
+use codespan_reporting::term;
+use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
 
-#[derive(Debug, thiserror::Error)]
-pub enum LoadFileError {
-    #[error("file already loaded")]
-    FileAlreadyLoaded,
-    #[error("error loading file: {0}")]
-    IoError(#[from] io::Error),
-}
-
+#[derive(Debug)]
 pub struct SourceFiles {
     files: SimpleFiles<String, String>,
     files_by_path: HashMap<PathBuf, usize>,
@@ -26,20 +22,31 @@ impl SourceFiles {
         }
     }
 
-    pub fn load(&mut self, path: &Path) -> Result<SourceFile, LoadFileError> {
+    pub fn load(&mut self, path: &Path) -> io::Result<(SourceFile, &str)> {
         let canonical_path = path.canonicalize()?;
-        if self.files_by_path.contains_key(&canonical_path) {
-            return Err(LoadFileError::FileAlreadyLoaded);
-        }
+        let file_id = if let Some(&file_id) = self.files_by_path.get(&canonical_path) {
+            file_id
+        } else {
+            let name = path.as_os_str().to_string_lossy().into_owned();
+            let content = fs::read_to_string(path)?;
+            self.files.add(name, content)
+        };
 
-        let name = path.as_os_str().to_string_lossy().into_owned();
-        let content = fs::read_to_string(path)?;
-        let file_id = self.files.add(name, content);
-        Ok(SourceFile(file_id))
+        let content = self.files.get(file_id).unwrap().source() as &str;
+        Ok((SourceFile(file_id), content))
     }
 
-    pub fn content_of(&self, file: SourceFile) -> Option<&str> {
-        self.files.get(file.0).ok().map(|sf| sf.source() as &str)
+    pub fn emit_all<'a, T>(&self, diagnostics: &'a [T])
+    where
+        &'a T: Into<Diagnostic<usize>>,
+    {
+        let stderr = StandardStream::stderr(ColorChoice::Auto);
+        let config = term::Config::default();
+
+        for diagnostic in diagnostics {
+            let diagnostic: Diagnostic<usize> = diagnostic.into();
+            term::emit(&mut stderr.lock(), &config, &self.files, &diagnostic);
+        }
     }
 }
 
@@ -49,7 +56,7 @@ pub struct SourceFile(usize);
 impl SourceFile {
     pub fn span(&self, range: Range<usize>) -> SourceSpan {
         SourceSpan {
-            file: self.0,
+            file_id: self.0,
             start: range.start,
             end: range.end,
         }
@@ -58,7 +65,17 @@ impl SourceFile {
 
 #[derive(Clone, Copy, Debug)]
 pub struct SourceSpan {
-    file: usize,
+    file_id: usize,
     start: usize,
     end: usize,
 }
+
+impl SourceSpan {
+    pub fn file_id(&self) -> usize {
+        self.file_id
+    }
+
+    pub fn range(&self) -> Range<usize> {
+        self.start..self.end
+    }
+}