Add FileSelection dialog type

This patch adds the FileSelection struct representing a file selection
dialog.  It can be displayed using the backend’s show_file_selection
function.

Currently, we only support file open dialogs (i. e.  choosing an
existing file).  Support for save dialogs should be added in the future.

1 files changed, 14 insertions, 1 deletions

diff --git a/src/backends/stdio.rs b/src/backends/stdio.rs
index 9a153df..627714a 100644
--- a/src/backends/stdio.rs
+++ b/src/backends/stdio.rs
@@ -3,7 +3,7 @@
 
 use std::io::{self, Write};
 
-use crate::{Choice, Input, Message, Password, Question, Result};
+use crate::{Choice, FileSelection, Input, Message, Password, Question, Result};
 
 /// The fallback backend using standard input and output.
 ///
@@ -86,4 +86,17 @@ impl super::Backend for Stdio {
         io::stdout().flush()?;
         Ok(parse_choice(&read_input()?))
     }
+
+    fn show_file_selection(&self, file_selection: &FileSelection) -> Result<Option<String>> {
+        let dir = file_selection.path_to_string().ok_or("path not valid")?;
+        print_title(&file_selection.title);
+        print!("{} [{}]: ", file_selection.text, dir);
+        io::stdout().flush()?;
+        let result = read_input()?;
+        if result.starts_with('/') {
+            Ok(Some(result))
+        } else {
+            Ok(Some(dir + &result))
+        }
+    }
 }