fix permission issues with listing channels/sending messages

lib/util.go

@@ -0,0 +1,79 @@
+package lib
+
+import "github.com/diamondburned/arikawa/v3/discord"
+
+func GuildPermissionsOf(guild discord.Guild, member discord.Member) discord.Permissions {
+  if guild.OwnerID == member.User.ID {
+    return discord.PermissionAll
+  }
+
+  var perm discord.Permissions
+
+  for _, role := range guild.Roles {
+    if role.ID == discord.RoleID(guild.ID) {
+      perm |= role.Permissions
+      break
+    }
+  }
+
+  if perm.Has(discord.PermissionAdministrator) {
+    return discord.PermissionAll
+  }
+
+  for _, role := range guild.Roles {
+    for _, id := range member.RoleIDs {
+      if id == role.ID {
+        perm |= role.Permissions
+      }
+    }
+  }
+
+  if perm.Has(discord.PermissionAdministrator) {
+    return discord.PermissionAll
+  }
+
+  return perm
+}
+
+func ChannelPermissionsOf(guild discord.Guild, channel discord.Channel, member discord.Member) discord.Permissions {
+  perm := GuildPermissionsOf(guild, member)
+
+  if perm.Has(discord.PermissionAdministrator) {
+    return discord.PermissionAll
+  }
+
+  for _, overwrite := range channel.Overwrites {
+    if discord.GuildID(overwrite.ID) == guild.ID {
+      perm &= ^overwrite.Deny
+      perm |= overwrite.Allow
+      break
+    }
+  }
+
+  var deny, allow discord.Permissions
+
+  for _, overwrite := range channel.Overwrites {
+    for _, id := range member.RoleIDs {
+      if id == discord.RoleID(overwrite.ID) && overwrite.Type == discord.OverwriteRole {
+        deny |= overwrite.Deny
+        allow |= overwrite.Allow
+      }
+    }
+  }
+
+  perm &= ^deny
+  perm |= allow
+
+  for _, overwrite := range channel.Overwrites {
+    if discord.UserID(overwrite.ID) == member.User.ID && overwrite.Type == discord.OverwriteMember {
+      perm &= ^overwrite.Deny
+      perm |= overwrite.Allow
+    }
+  }
+
+  if perm.Has(discord.PermissionAdministrator) {
+    return discord.PermissionAll
+  }
+
+  return perm
+}