Switch to Entity Framework

Turned existing database setup into a migration, and all helper methods
were moved to the new class for easy migration to the new system.

Data/BotDatabaseContext.cs

@@ -0,0 +1,115 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace WorldTime.Data;
+public class BotDatabaseContext : DbContext {
+    private static string? _npgsqlConnectionString;
+    internal static string NpgsqlConnectionString {
+#if DEBUG
+        get {
+            if (_npgsqlConnectionString != null) return _npgsqlConnectionString;
+            Program.Log(nameof(BotDatabaseContext), "Using hardcoded connection string!");
+            return _npgsqlConnectionString ?? "Host=localhost;Username=worldtime;Password=wt";
+        }
+#else
+        get => _npgsqlConnectionString!;
+#endif
+        set => _npgsqlConnectionString ??= value;
+    }
+
+    public DbSet<UserEntry> UserEntries { get; set; } = null!;
+
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+         => optionsBuilder
+            .UseNpgsql(NpgsqlConnectionString)
+#if DEBUG
+            .LogTo((string line) => Program.Log("EF", line), Microsoft.Extensions.Logging.LogLevel.Information)
+#endif
+            .UseSnakeCaseNamingConvention();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder) {
+        modelBuilder.Entity<UserEntry>(entity => {
+            entity.HasKey(e => new { e.GuildId, e.UserId }).HasName("userdata_pkey");
+            entity.Property(e => e.LastUpdate).HasDefaultValueSql("now()");
+        });
+    }
+
+    #region Helper methods / abstractions
+    /// <summary>
+    /// Checks if a given guild contains at least one user data entry with recent enough activity.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    internal bool HasAnyUsers(SocketGuild guild) => UserEntries.Where(u => u.GuildId == (long)guild.Id).Any();
+
+    /// <summary>
+    /// Gets the number of unique time zones in the database.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    internal int GetDistinctZoneCount() => UserEntries.Select(u => u.TimeZone).Distinct().Count();
+
+    /// <summary>
+    /// Removes the specified user from the database.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    /// <returns>
+    /// <see langword="true"/> if the removal was successful.
+    /// <see langword="false"/> if the user did not exist.
+    /// </returns>
+    internal bool DeleteUser(SocketGuildUser user) {
+        var tuser = UserEntries.Where(u => u.UserId == (long)user.Id && u.GuildId == (long)user.Guild.Id).SingleOrDefault();
+        if (tuser != null) {
+            Remove(tuser);
+            SaveChanges();
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Inserts/updates the specified user in the database.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    internal void UpdateUser(SocketGuildUser user, string timezone) {
+        var tuser = UserEntries.Where(u => u.UserId == (long)user.Id && u.GuildId == (long)user.Guild.Id).SingleOrDefault();
+        if (tuser != null) {
+            Update(tuser);
+        } else {
+            tuser = new UserEntry() { UserId = (long)user.Id, GuildId = (long)user.Guild.Id };
+            Add(tuser);
+        }
+        tuser.TimeZone = timezone;
+        SaveChanges();
+    }
+
+    /// <summary>
+    /// Retrieves the time zone name of a single user.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    internal string? GetUserZone(SocketGuildUser user) {
+        var tuser = UserEntries.Where(u => u.UserId == (long)user.Id && u.GuildId == (long)user.Guild.Id).SingleOrDefault();
+        return tuser?.TimeZone;
+    }
+
+    /// <summary>
+    /// Retrieves all known user time zones for the given guild.
+    /// <br />To be used within a <see langword="using"/> context.
+    /// </summary>
+    /// <returns>
+    /// An unsorted dictionary. Keys are time zones, values are user IDs representative of those zones.
+    /// </returns>
+    internal Dictionary<string, List<ulong>> GetGuildZones(ulong guildId) {
+        // Implementing the query from the previous iteration, in which further filtering is done by the caller.
+        // TODO consider bringing filtering back to this step, if there may be any advantage
+        var query = from entry in UserEntries
+                    where entry.GuildId == (long)guildId
+                    orderby entry.UserId
+                    select Tuple.Create(entry.TimeZone, (ulong)entry.UserId);
+        var resultSet = new Dictionary<string, List<ulong>>();
+        foreach (var (tz, user) in query) {
+            if (!resultSet.ContainsKey(tz)) resultSet.Add(tz, new List<ulong>());
+            resultSet[tz].Add(user);
+        }
+        return resultSet;
+    }
+    #endregion
+}

Data/Migrations/20220628235704_InitialMigration.Designer.cs

@@ -0,0 +1,56 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+using WorldTime.Data;
+
+#nullable disable
+
+namespace WorldTime.Data.Migrations
+{
+    [DbContext(typeof(BotDatabaseContext))]
+    [Migration("20220628235704_InitialMigration")]
+    partial class InitialMigration
+    {
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "6.0.6")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("WorldTime.Data.UserEntry", b =>
+                {
+                    b.Property<long>("GuildId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("guild_id");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("user_id");
+
+                    b.Property<DateTime>("LastUpdate")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("last_active")
+                        .HasDefaultValueSql("now()");
+
+                    b.Property<string>("TimeZone")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("zone");
+
+                    b.HasKey("GuildId", "UserId")
+                        .HasName("userdata_pkey");
+
+                    b.ToTable("userdata", (string)null);
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

Data/Migrations/20220628235704_InitialMigration.cs

@@ -0,0 +1,33 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace WorldTime.Data.Migrations
+{
+    public partial class InitialMigration : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "userdata",
+                columns: table => new
+                {
+                    guild_id = table.Column<long>(type: "bigint", nullable: false),
+                    user_id = table.Column<long>(type: "bigint", nullable: false),
+                    zone = table.Column<string>(type: "text", nullable: false),
+                    last_active = table.Column<DateTime>(type: "timestamp with time zone", nullable: false, defaultValueSql: "now()")
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("userdata_pkey", x => new { x.guild_id, x.user_id });
+                });
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "userdata");
+        }
+    }
+}

Data/Migrations/BotDatabaseContextModelSnapshot.cs

@@ -0,0 +1,54 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+using WorldTime.Data;
+
+#nullable disable
+
+namespace WorldTime.Data.Migrations
+{
+    [DbContext(typeof(BotDatabaseContext))]
+    partial class BotDatabaseContextModelSnapshot : ModelSnapshot
+    {
+        protected override void BuildModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "6.0.6")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("WorldTime.Data.UserEntry", b =>
+                {
+                    b.Property<long>("GuildId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("guild_id");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("user_id");
+
+                    b.Property<DateTime>("LastUpdate")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("last_active")
+                        .HasDefaultValueSql("now()");
+
+                    b.Property<string>("TimeZone")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("zone");
+
+                    b.HasKey("GuildId", "UserId")
+                        .HasName("userdata_pkey");
+
+                    b.ToTable("userdata", (string)null);
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

Data/UserEntry.cs

@@ -0,0 +1,18 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace WorldTime.Data;
+[Table("userdata")]
+public class UserEntry {
+    [Key]
+    [Column("guild_id")]
+    public long GuildId { get; set; }
+    [Key]
+    [Column("user_id")]
+    public long UserId { get; set; }
+    [Column("zone")]
+    public string TimeZone { get; set; } = null!;
+    [Obsolete("No longer in use and should be removed promptly.")]
+    [Column("last_active")]
+    public DateTime LastUpdate { get; set; }
+}

Database.cs

@@ -1,144 +0,0 @@
-using Npgsql;
-using NpgsqlTypes;
-
-namespace WorldTime;
-
-/// <summary>
-/// Database abstractions
-/// </summary>
-public class Database {
-    private const string UserDatabase = "userdata";
-
-    private readonly string _connectionString;
-
-    internal Database(string connectionString) {
-        _connectionString = connectionString;
-        DoInitialDatabaseSetupAsync().ConfigureAwait(false).GetAwaiter().GetResult();
-    }
-
-    /// <summary>
-    /// Sets up and opens a database connection.
-    /// </summary>
-    private async Task<NpgsqlConnection> OpenConnectionAsync() {
-        var db = new NpgsqlConnection(_connectionString);
-        await db.OpenAsync().ConfigureAwait(false);
-        return db;
-    }
-
-    private async Task DoInitialDatabaseSetupAsync() {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $"create table if not exists {UserDatabase} ("
-            + $"guild_id BIGINT, "
-            + "user_id BIGINT, "
-            + "zone TEXT NOT NULL, "
-            + "last_active TIMESTAMPTZ NOT NULL DEFAULT now(), "
-            + "PRIMARY KEY (guild_id, user_id)" // index automatically created with this
-            + ")";
-        await c.ExecuteNonQueryAsync().ConfigureAwait(false);
-    }
-
-    /// <summary>
-    /// Checks if a given guild contains at least one user data entry with recent enough activity.
-    /// </summary>
-    internal async Task<bool> HasAnyAsync(SocketGuild guild) {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $@"
-SELECT true FROM {UserDatabase}
-WHERE
-    guild_id = @Gid
-LIMIT 1
-";
-        c.Parameters.Add("@Gid", NpgsqlDbType.Bigint).Value = (long)guild.Id;
-        await c.PrepareAsync().ConfigureAwait(false);
-        using var r = await c.ExecuteReaderAsync().ConfigureAwait(false);
-        return await r.ReadAsync().ConfigureAwait(false);
-    }
-
-    /// <summary>
-    /// Gets the number of unique time zones in the database.
-    /// </summary>
-    internal async Task<int> GetDistinctZoneCountAsync() {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $"SELECT COUNT(DISTINCT zone) FROM {UserDatabase}";
-        return (int)((long?)await c.ExecuteScalarAsync() ?? -1); // ExecuteScalarAsync returns a long here
-    }
-
-    /// <summary>
-    /// Removes the specified user from the database.
-    /// </summary>
-    /// <returns>True if the removal was successful. False typically if the user did not exist.</returns>
-    internal async Task<bool> DeleteUserAsync(SocketGuildUser user) {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $"DELETE FROM {UserDatabase} " +
-            "WHERE guild_id = @Gid AND user_id = @Uid";
-        c.Parameters.Add("@Gid", NpgsqlDbType.Bigint).Value = (long)user.Guild.Id;
-        c.Parameters.Add("@Uid", NpgsqlDbType.Bigint).Value = (long)user.Id;
-        await c.PrepareAsync().ConfigureAwait(false);
-        return await c.ExecuteNonQueryAsync().ConfigureAwait(false) > 0;
-    }
-
-    /// <summary>
-    /// Inserts/updates the specified user in the database.
-    /// </summary>
-    internal async Task UpdateUserAsync(SocketGuildUser user, string timezone) {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $"INSERT INTO {UserDatabase} (guild_id, user_id, zone) " +
-            "VALUES (@Gid, @Uid, @Zone) " +
-            "ON CONFLICT (guild_id, user_id) DO " +
-            "UPDATE SET zone = EXCLUDED.zone";
-        c.Parameters.Add("@Gid", NpgsqlDbType.Bigint).Value = (long)user.Guild.Id;
-        c.Parameters.Add("@Uid", NpgsqlDbType.Bigint).Value = (long)user.Id;
-        c.Parameters.Add("@Zone", NpgsqlDbType.Text).Value = timezone;
-        await c.PrepareAsync().ConfigureAwait(false);
-        await c.ExecuteNonQueryAsync().ConfigureAwait(false);
-    }
-
-    /// <summary>
-    /// Retrieves the time zone name of a single user.
-    /// </summary>
-    internal async Task<string?> GetUserZoneAsync(SocketGuildUser user) {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $"SELECT zone FROM {UserDatabase} " +
-            "WHERE guild_id = @Gid AND user_id = @Uid";
-        c.Parameters.Add("@Gid", NpgsqlDbType.Bigint).Value = (long)user.Guild.Id;
-        c.Parameters.Add("@Uid", NpgsqlDbType.Bigint).Value = (long)user.Id;
-        await c.PrepareAsync().ConfigureAwait(false);
-        return (string?)await c.ExecuteScalarAsync();
-    }
-
-    /// <summary>
-    /// Retrieves all known user time zones for the given guild.
-    /// Further filtering should be handled by the consumer.
-    /// </summary>
-    /// <returns>
-    /// An unsorted dictionary. Keys are time zones, values are user IDs representative of those zones.
-    /// </returns>
-    internal async Task<Dictionary<string, List<ulong>>> GetGuildZonesAsync(ulong guildId) {
-        using var db = await OpenConnectionAsync().ConfigureAwait(false);
-        using var c = db.CreateCommand();
-        c.CommandText = $@" -- Simpler query than 1.x; most filtering is now done by caller
-SELECT zone, user_id FROM {UserDatabase}
-WHERE
-    guild_id = @Gid
-ORDER BY RANDOM() -- Randomize results for display purposes";
-        c.Parameters.Add("@Gid", NpgsqlDbType.Bigint).Value = (long)guildId;
-        await c.PrepareAsync().ConfigureAwait(false);
-        var r = await c.ExecuteReaderAsync().ConfigureAwait(false);
-
-        var resultSet = new Dictionary<string, List<ulong>>();
-        while (await r.ReadAsync().ConfigureAwait(false)) {
-            var tz = r.GetString(0);
-            var user = (ulong)r.GetInt64(1);
-
-            if (!resultSet.ContainsKey(tz)) resultSet.Add(tz, new List<ulong>());
-            resultSet[tz].Add(user);
-        }
-        return resultSet;
-    }
-}

WorldTime.csproj

@@ -12,10 +12,18 @@
   <ItemGroup>
     <PackageReference Include="CommandLineParser" Version="2.8.0" />
     <PackageReference Include="Discord.Net" Version="3.5.0" />
+    <PackageReference Include="EFCore.NamingConventions" Version="6.0.0" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="6.0.6" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="6.0.6">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="NodaTime" Version="3.1.0" />
-    <PackageReference Include="Npgsql" Version="6.0.4" />
+    <PackageReference Include="Npgsql" Version="6.0.5" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="6.0.5" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL.Design" Version="1.1.0" />
   </ItemGroup>
 
 </Project>