Add tags_of_file() to extract tags from a File

src/module/bm/header.rs

@@ -1,5 +1,6 @@
 use storage::file::FileHeaderSpec as FHS;
 use storage::file::FileHeaderData as FHD;
+use std::ops::Deref;
 
 pub fn get_spec() -> FHS {
     FHS::Map { keys: vec![ url_key(), tags_key() ] }
@@ -38,3 +39,41 @@ fn build_tag_array(tags: &Vec<String>) -> FHD {
     FHD::Array { values: Box::new(texttags) }
 }
 
+pub fn get_tags_from_header(header: &FHD) -> Vec<String> {
+    let mut tags : Vec<String> = vec![];
+
+    fn match_array(a: &Box<FHD>) -> Vec<String> {
+        let mut tags : Vec<String> = vec![];
+
+        match a.deref() {
+            &FHD::Array{values: ref vs} => {
+                let values : Vec<FHD> = vs.deref().clone();
+                for value in values {
+                    match value {
+                        FHD::Text(t) => tags.push(t),
+                        _ => warn!("Malformed Header Data: Expected Text, found non-Text"),
+                    }
+                }
+            }
+            _ => warn!("Malformed Header Data: Expected Array, found non-Array"),
+        }
+
+        tags
+    }
+
+    match header {
+        &FHD::Map{keys: ref ks} => {
+            let keys : Vec<FHD> = ks.clone();
+            for key in keys {
+                match key {
+                    FHD::Key{name: _, value: ref v} => return match_array(v),
+                    _ => warn!("Malformed Header Data: Expected Key, found non-Key"),
+                }
+            }
+        },
+        _ => warn!("Malformed Header Data: Expected Map, found non-Map"),
+    }
+
+    tags
+}
+