Add MIME support

- Wrap encrypted mails into a mime structure
- Add 'protected headers'

src/types/cheader.rs

@@ -0,0 +1,128 @@
+//! CHeader struct
+//!
+//! This struct is for collecting header lines from the milter.
+
+use std::ffi::CString;
+use std::fmt;
+
+pub struct CHeader {
+    lines: Vec<(CString, CString)>
+}
+
+impl CHeader {
+    pub fn new() -> Self {
+        CHeader {
+            lines: Vec::new()
+        }
+    }
+
+    pub fn add(mut self, key: CString, value: CString) -> Self {
+        self.lines.push((key, value));
+        self
+    }
+
+    pub fn append(&mut self, key: CString, value: CString) {
+        self.lines.push((key, value));
+    }
+
+    pub fn find(&self, key: &str) -> Option<(&str, &str)> {
+        let lower_key = key.to_lowercase();
+        for (line_key, line_value) in self.lines.iter() {
+            if let Ok(line_compare) = line_key.to_str() {
+                if line_compare.to_ascii_lowercase() == lower_key {
+                    if let Ok(line_value_as_str) = line_value.to_str() {
+                        return Some(
+                            (line_compare, line_value_as_str)
+                        );
+                    }
+                }
+            }
+        }
+        None
+    }
+
+    pub fn get_value_or<'ch>(&'ch self, key: &str, default: &'ch str) -> &'ch str {
+        if let Some((_, value)) = self.find(key) {
+            value
+        } else {
+            default
+        }
+    }
+
+    pub fn iter_lines(&self) -> std::slice::Iter<'_, (CString, CString)> {
+        self.lines.iter()
+    }
+}
+
+impl fmt::Display for CHeader {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", [
+            self.iter_lines()
+                .filter_map(|(k, v)| {
+                    match (k.to_str(), v.to_str()) {
+                        (Ok(k), Ok(v)) => Some([k, v].join(": ")),
+                        _ => None,
+                    }
+                })
+                .collect::<Vec<String>>()
+                .join("\r\n"),
+            "\r\n".to_string()]
+            .join("")
+        )
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use std::ffi::CString;
+    use super::CHeader;
+
+
+#[test]
+    pub fn basic_functionality() {
+        let cheader = CHeader::new()
+            .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
+            .add(CString::new("Content-Transfer-Encoding").unwrap(), CString::new("7bit").unwrap());
+
+        assert_eq!("Content-Type: text/plain\r\nContent-Transfer-Encoding: 7bit\r\n", cheader.to_string());
+    }
+
+#[test]
+    pub fn find() {
+        let cheader = CHeader::new()
+            .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
+            .add(CString::new("Content-Transfer-Encoding").unwrap(), CString::new("7bit").unwrap());
+
+        let line = cheader.find("content-type");
+
+        assert!(line.is_some());
+
+        let (key, value) = line.unwrap();
+
+        assert_eq!("Content-Type", key);
+        assert_eq!("text/plain", value);
+    }
+
+#[test]
+    pub fn find_none() {
+        let cheader = CHeader::new()
+            .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
+            .add(CString::new("Content-Transfer-Encoding").unwrap(), CString::new("7bit").unwrap());
+
+        let line = cheader.find("foo-bar");
+
+        assert!(line.is_none());
+    }
+
+#[test]
+    pub fn find_with_default() {
+        let cheader = CHeader::new()
+            .add(CString::new("Content-Type").unwrap(), CString::new("text/plain").unwrap())
+            .add(CString::new("Content-Transfer-Encoding").unwrap(), CString::new("7bit").unwrap());
+
+        let value = cheader.get_value_or("foo-bar", "baaz");
+
+        assert_eq!(value, "baaz");
+    }
+}
+