Refactor sort/filter code once again

Now we handle sorting on the bot side, but still filter in the database

PluralKit.Core/Database/Views/DatabaseViewsExt.cs

@@ -0,0 +1,34 @@
+#nullable enable
+using System.Collections.Generic;
+using System.Text;
+using System.Threading.Tasks;
+
+using Dapper;
+
+namespace PluralKit.Core
+{
+    public static class DatabaseViewsExt
+    {
+        public static Task<IEnumerable<SystemFronter>> QueryCurrentFronters(this IPKConnection conn, int system) =>
+            conn.QueryAsync<SystemFronter>("select * from system_fronters where system = @system", new {system});
+
+        public static Task<IEnumerable<ListedMember>> QueryMemberList(this IPKConnection conn, int system, PrivacyLevel? privacyFilter = null, string? filter = null, bool includeDescriptionInNameFilter = false)
+        {
+            StringBuilder query = new StringBuilder("select * from member_list where system = @system");
+
+            if (privacyFilter != null)
+                query.Append($" and member_privacy = {(int) privacyFilter}");
+
+            if (filter != null)
+            {
+                static string Filter(string column) => $"position(lower(@filter) in lower(coalesce({column}, ''))) > 0"; 
+
+                query.Append($" and ({Filter("name")} or {Filter("display_name")}");
+                if (includeDescriptionInNameFilter) query.Append($" or {Filter("description")}");
+                query.Append(")");
+            }
+            
+            return conn.QueryAsync<ListedMember>(query.ToString(), new {system, filter});
+        }
+    }
+}

PluralKit.Core/Database/Views/ListedMember.cs

@@ -0,0 +1,17 @@
+#nullable enable
+using NodaTime;
+
+namespace PluralKit.Core
+{
+    // TODO: is inheritance here correct?
+    public class ListedMember: PKMember
+    {
+        public ulong? LastMessage { get; }
+        public Instant? LastSwitchTime { get; }
+
+        public AnnualDate? AnnualBirthday =>
+            Birthday != null
+                ? new AnnualDate(Birthday.Value.Month, Birthday.Value.Day)
+                : (AnnualDate?) null;
+    }
+}

PluralKit.Core/Database/Views/SystemFronter.cs

@@ -0,0 +1,14 @@
+using NodaTime;
+
+namespace PluralKit.Core
+{
+    public class SystemFronter
+    {
+        public int SystemId { get; }
+        public int SwitchId { get; }
+        public Instant SwitchTimestamp { get; }
+        public int MemberId { get; }
+        public string MemberHid { get; }
+        public string MemberName { get; }
+    }
+}

PluralKit.Core/Database/Views/views.sql

@@ -0,0 +1,50 @@
+-- Returns one row per system, containing info about latest switch + array of member IDs (for future joins)
+create view system_last_switch as
+select systems.id as system,
+       last_switch.id as switch,
+       last_switch.timestamp as timestamp,
+       array(select member from switch_members where switch_members.switch = last_switch.id) as members
+from systems
+    inner join lateral (select * from switches where switches.system = systems.id order by timestamp desc limit 1) as last_switch on true;
+
+-- Returns one row for every current fronter in a system, w/ some member info
+create view system_fronters as
+select
+    systems.id as system_id,
+    last_switch.id as switch_id,
+    last_switch.timestamp as switch_timestamp,
+    members.id as member_id,
+    members.hid as member_hid,
+    members.name as member_name
+from systems
+    -- TODO: is there a more efficient way of doing this search? might need to index on timestamp if we haven't in prod
+    inner join lateral (select * from switches where switches.system = systems.id order by timestamp desc limit 1) as last_switch on true
+        
+    -- change to left join to handle memberless switches?
+    inner join switch_members on switch_members.switch = last_switch.system
+    inner join members on members.id = switch_members.member
+-- return them in order of the switch itself
+order by switch_members.id;
+
+create view member_list as
+select members.*,
+       -- Find last message ID
+       -- max(mid) does full table scan, order by/limit uses index (dunno why, but it works!)
+       (select mid from messages where messages.member = members.id order by mid desc nulls last limit 1) as last_message,
+       
+       -- Find last switch timestamp
+       (
+           select max(switches.timestamp)
+           from switch_members
+                    inner join switches on switches.id = switch_members.switch
+           where switch_members.member = members.id
+       ) as last_switch_time,
+       
+       -- Extract month/day from birthday and "force" the year identical (just using 4) -> month/day only sorting! 
+       case when members.birthday is not null then
+           make_date(
+               4,
+               extract(month from members.birthday)::integer,
+               extract(day from members.birthday)::integer
+           ) end as birthday_md
+from members;