Re-structure Permissions; add perm to view users from mutual groups.

src/database/permissions/mod.rs

@@ -1,4 +1,38 @@
+pub use crate::database::*;
+
 pub mod channel;
 pub mod user;
 
 pub use user::get_relationship;
+
+pub struct PermissionCalculator<'a> {
+    perspective: &'a User,
+
+    user: Option<&'a User>,
+    channel: Option<&'a Channel>,
+}
+
+impl<'a> PermissionCalculator<'a> {
+    pub fn new(perspective: &'a User) -> PermissionCalculator {
+        PermissionCalculator {
+            perspective,
+
+            user: None,
+            channel: None
+        }
+    }
+
+    pub fn with_user(self, user: &'a User) -> PermissionCalculator {
+        PermissionCalculator {
+            user: Some(&user),
+            ..self
+        }
+    }
+
+    pub fn with_channel(self, channel: &'a Channel) -> PermissionCalculator {
+        PermissionCalculator {
+            channel: Some(&channel),
+            ..self
+        }
+    }
+}