1 files changed, 92 insertions, 0 deletions
diff --git a/src/tui.rs b/src/tui.rs
new file mode 100644
index 0000000..8d84a7f
--- /dev/null
+++ b/src/tui.rs
@@ -0,0 +1,92 @@
+use futures::future::{Future as _, IntoFuture as _};
+use futures::stream::Stream as _;
+use std::io::Write as _;
+
+#[derive(Debug, snafu::Snafu)]
+pub enum Error {
+    #[snafu(display("error during read: {}", source))]
+    Read { source: crate::readline::Error },
+
+    #[snafu(display("error during eval: {}", source))]
+    Eval { source: crate::eval::Error },
+
+    #[snafu(display("error during print: {}", source))]
+    Print { source: crate::state::Error },
+}
+
+pub fn tui() {
+    tokio::run(futures::lazy(|| {
+        let (w, r) = futures::sync::mpsc::channel(0);
+
+        tokio::spawn(crate::state::State::new(r).map_err(|e| {
+            error(&Error::Print { source: e });
+        }));
+
+        futures::future::loop_fn(0, move |idx| {
+            let w = w.clone();
+            read()
+                .and_then(move |line| {
+                    let w = w.clone();
+                    eval(&line).for_each(move |event| {
+                        let w = w.clone();
+                        print(w, idx, &event)
+                    })
+                })
+                .then(move |res| match res {
+                    // successful run or empty input means prompt again
+                    Ok(_)
+                    | Err(Error::Eval {
+                        source:
+                            crate::eval::Error::Parser {
+                                source: crate::parser::Error::CommandRequired,
+                                ..
+                            },
+                    }) => Ok(futures::future::Loop::Continue(idx + 1)),
+                    // eof means we're done
+                    Err(Error::Read {
+                        source: crate::readline::Error::EOF,
+                    }) => Ok(futures::future::Loop::Break(())),
+                    // any other errors should be displayed, then we
+                    // prompt again
+                    Err(e) => {
+                        error(&e);
+                        Ok(futures::future::Loop::Continue(idx + 1))
+                    }
+                })
+        })
+    }));
+}
+
+fn read() -> impl futures::future::Future<Item = String, Error = Error> {
+    crate::readline::readline("$ ", true)
+        .into_future()
+        .flatten()
+        .map_err(|e| Error::Read { source: e })
+}
+
+fn eval(
+    line: &str,
+) -> impl futures::stream::Stream<Item = crate::eval::CommandEvent, Error = Error>
+{
+    crate::eval::eval(line)
+        .into_future()
+        .flatten_stream()
+        .map_err(|e| Error::Eval { source: e })
+}
+
+fn print(
+    w: futures::sync::mpsc::Sender<crate::state::StateEvent>,
+    idx: usize,
+    event: &crate::eval::CommandEvent,
+) -> impl futures::future::Future<Item = (), Error = Error> {
+    crate::state::update(w, idx, event)
+        .map_err(|e| Error::Print { source: e })
+}
+
+fn error(e: &Error) {
+    let stderr = std::io::stderr();
+    let mut stderr = stderr.lock();
+    // panics seem fine for errors during error handling
+    write!(stderr, "{}\r\n", e).unwrap();
+    stderr.flush().unwrap();
+}