1 files changed, 69 insertions, 0 deletions
diff --git a/src/fence_wrapper.rs b/src/fence_wrapper.rs
new file mode 100644
index 0000000..a218088
--- /dev/null
+++ b/src/fence_wrapper.rs
@@ -0,0 +1,69 @@
+use std::io::{Read, Write};
+
+use crate::util::fence::generate_outer_backticks;
+
+pub fn wrap_in_fence<R: Read, W: Write>(
+    mut input: R,
+    mut output: W,
+    lang: &str,
+) -> std::io::Result<()> {
+    let mut contents = Vec::new();
+    input.read_to_end(&mut contents)?;
+    let fence = generate_outer_backticks(&contents);
+    writeln!(output, "{}{}", fence, lang)?;
+    output.write_all(&contents)?;
+    writeln!(output, "\n{}", fence)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::io::Cursor;
+
+    use super::wrap_in_fence;
+
+    #[test]
+    fn wraps_input_in_fence_with_language() {
+        let input = Cursor::new("fn main() {}\n");
+        let mut output = Vec::new();
+
+        wrap_in_fence(input, &mut output, "rust").unwrap();
+
+        assert_eq!(
+            String::from_utf8(output).unwrap(),
+            "```rust\nfn main() {}\n\n```\n"
+        );
+    }
+
+    #[test]
+    fn puts_closing_fence_on_new_line_when_input_has_no_trailing_newline() {
+        let input = Cursor::new("hello");
+        let mut output = Vec::new();
+
+        wrap_in_fence(input, &mut output, "text").unwrap();
+
+        assert_eq!(String::from_utf8(output).unwrap(), "```text\nhello\n```\n");
+    }
+
+    #[test]
+    fn uses_longer_fence_when_input_contains_backticks() {
+        let input = Cursor::new("contains ``` inside\n");
+        let mut output = Vec::new();
+
+        wrap_in_fence(input, &mut output, "markdown").unwrap();
+
+        assert_eq!(
+            String::from_utf8(output).unwrap(),
+            "````markdown\ncontains ``` inside\n\n````\n"
+        );
+    }
+
+    #[test]
+    fn wraps_empty_input() {
+        let input = Cursor::new("");
+        let mut output = Vec::new();
+
+        wrap_in_fence(input, &mut output, "text").unwrap();
+
+        assert_eq!(String::from_utf8(output).unwrap(), "```text\n\n```\n");
+    }
+}