add: communities list page

TODO(ui): implement community creation, community viewing, community posting
TODO(ui): implement profile following, followers, and posts feed

crates/core/src/model/communities_permissions.rs

@@ -0,0 +1,112 @@
+use bitflags::bitflags;
+use serde::{
+    Deserialize, Deserializer, Serialize,
+    de::{Error as DeError, Visitor},
+};
+
+bitflags! {
+    /// Fine-grained journal permissions built using bitwise operations.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    pub struct CommunityPermission: u32 {
+        const DEFAULT = 1 << 0;
+        const ADMINISTRATOR = 1 << 1;
+        const MEMBER = 1 << 2;
+        const MANAGE_POSTS = 1 << 3;
+        const MANAGE_ROLES = 1 << 4;
+
+        const _ = !0;
+    }
+}
+
+impl Serialize for CommunityPermission {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_u32(self.bits())
+    }
+}
+
+struct JournalPermissionVisitor;
+impl<'de> Visitor<'de> for JournalPermissionVisitor {
+    type Value = CommunityPermission;
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        formatter.write_str("u32")
+    }
+
+    fn visit_u32<E>(self, value: u32) -> Result<Self::Value, E>
+    where
+        E: DeError,
+    {
+        if let Some(permission) = CommunityPermission::from_bits(value) {
+            Ok(permission)
+        } else {
+            Ok(CommunityPermission::from_bits_retain(value))
+        }
+    }
+
+    fn visit_i32<E>(self, value: i32) -> Result<Self::Value, E>
+    where
+        E: DeError,
+    {
+        if let Some(permission) = CommunityPermission::from_bits(value as u32) {
+            Ok(permission)
+        } else {
+            Ok(CommunityPermission::from_bits_retain(value as u32))
+        }
+    }
+
+    fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
+    where
+        E: DeError,
+    {
+        if let Some(permission) = CommunityPermission::from_bits(value as u32) {
+            Ok(permission)
+        } else {
+            Ok(CommunityPermission::from_bits_retain(value as u32))
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for CommunityPermission {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_any(JournalPermissionVisitor)
+    }
+}
+
+impl CommunityPermission {
+    /// Join two [`JournalPermission`]s into a single `u32`.
+    pub fn join(lhs: CommunityPermission, rhs: CommunityPermission) -> CommunityPermission {
+        lhs | rhs
+    }
+
+    /// Check if the given `input` contains the given [`JournalPermission`].
+    pub fn check(self, permission: CommunityPermission) -> bool {
+        if (self & CommunityPermission::ADMINISTRATOR) == CommunityPermission::ADMINISTRATOR {
+            // has administrator permission, meaning everything else is automatically true
+            return true;
+        }
+
+        (self & permission) == permission
+    }
+
+    /// Check if the given [`JournalPermission`] qualifies as "Member" status.
+    pub fn check_member(self) -> bool {
+        self.check(CommunityPermission::MEMBER)
+    }
+
+    /// Check if the given [`JournalPermission`] qualifies as "Moderator" status.
+    pub fn check_moderator(self) -> bool {
+        self.check(CommunityPermission::MANAGE_POSTS)
+    }
+}
+
+impl Default for CommunityPermission {
+    fn default() -> Self {
+        Self::DEFAULT
+    }
+}