Add the Tazel plugin catalog of ViGet to the API

ViGet opens in stages: first only Progmasoft publishes Tazel plugins, later
every account. This adds the catalog and the server-side publishing for the
first stage; nothing publishes through the API yet.

- ViGet/: the catalog of Tazel plugins (in memory, or in PostgreSQL beside
  the accounts with its own numbered schema steps), the descriptor read from
  the JAR (META-INF/tazel-plugin.properties, with a reader of the Java
  properties format, and the ProjectPlugin service entry), and publishing:
  the publisher must be in ViGet:TazelPublishers (Progmasoft for now) and an
  existing account of that exact name, a version is never replaced, names
  that differ only in letter case are refused, and ViGet needs a
  description, an author and a license. The JAR is kept at
  dslplugins/tazel/<Publisher>/<Name>/<Version>/<Name>-<Version>.jar below
  ViGet:ArtifactRoot.
- Read endpoints under /api/v1/viget/dslplugins/tazel: the list, a plugin,
  and index.json, the index Tazel reads.
- 'viget publish-tazel-plugin <jar>' and 'viget yank-tazel-plugin' run with
  the configuration of the service instead of the service.
- The account store can find an account by name.

The pages, the Nginx routes and the deployment follow.

15 files changed, 1487 insertions, 1 deletions

diff --git a/apps/api-tests/AccountServiceTests.cs b/apps/api-tests/AccountServiceTests.cs
index 28fd44f..0ff7b33 100644
--- a/apps/api-tests/AccountServiceTests.cs
+++ b/apps/api-tests/AccountServiceTests.cs
@@ -151,6 +151,12 @@ public sealed class AccountServiceTests
         public ValueTask<AccountRecord?> FindByIdAsync(Guid id, CancellationToken cancellationToken) =>
             ValueTask.FromResult<AccountRecord?>(passwordAccount.Id == id ? passwordAccount : null);
 
+        public ValueTask<AccountRecord?> FindByAccountNameAsync(
+            string normalizedAccountName,
+            CancellationToken cancellationToken) =>
+            ValueTask.FromResult<AccountRecord?>(
+                passwordAccount.NormalizedAccountName == normalizedAccountName ? passwordAccount : null);
+
         public ValueTask<AccountRecord?> FindByGoogleSubjectAsync(
             string googleSubject,
             CancellationToken cancellationToken) =>
diff --git a/apps/api-tests/AccountStoreSelectionTests.cs b/apps/api-tests/AccountStoreSelectionTests.cs
index 05ed31b..1087575 100644
--- a/apps/api-tests/AccountStoreSelectionTests.cs
+++ b/apps/api-tests/AccountStoreSelectionTests.cs
@@ -134,6 +134,11 @@ public sealed class ExpiredSessionCleanupTests
         public ValueTask<AccountRecord?> FindByIdAsync(Guid id, CancellationToken cancellationToken) =>
             throw new NotSupportedException();
 
+        public ValueTask<AccountRecord?> FindByAccountNameAsync(
+            string normalizedAccountName,
+            CancellationToken cancellationToken) =>
+            throw new NotSupportedException();
+
         public ValueTask StoreSessionAsync(SessionRecord session, CancellationToken cancellationToken) =>
             throw new NotSupportedException();
 
diff --git a/apps/api-tests/ViGetTests.cs b/apps/api-tests/ViGetTests.cs
new file mode 100644
index 0000000..603ef2f
--- /dev/null
+++ b/apps/api-tests/ViGetTests.cs
@@ -0,0 +1,269 @@
+// SPDX-FileCopyrightText: 2026 Progmasoft <support@progmasoft.com>
+// SPDX-License-Identifier: AGPL-3.0-or-later WITH AdditionRef-Progmasoft-Patent-Grant-1.1
+
+using System.IO.Compression;
+using System.Net;
+using System.Security.Cryptography;
+using System.Text.Json;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using Progmasoft.Progmaweb.Api.Accounts;
+using Progmasoft.Progmaweb.Api.ViGet;
+
+namespace Progmasoft.Progmaweb.Api.Tests;
+
+/// <summary>The Tazel plugin catalog of ViGet: the descriptor, publishing, the endpoints and the command.</summary>
+public sealed class ViGetTests : IDisposable
+{
+    private readonly string artifactRoot = Path.Combine(Path.GetTempPath(), "viget-" + Guid.NewGuid().ToString("N"));
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        if (Directory.Exists(artifactRoot))
+        {
+            Directory.Delete(artifactRoot, recursive: true);
+        }
+    }
+
+    [Fact]
+    public void PropertiesAreReadAsJavaReadsThem()
+    {
+        IReadOnlyDictionary<string, string> properties = JavaProperties.Parse(
+            "# a comment\n" +
+            "! another\n" +
+            "publisher=Progmasoft\n" +
+            "homepage = https\\://example.com/a\n" +
+            "description:Builds C \\u0026 C++,\\\n" +
+            "    on every host.\n" +
+            "key\\ with\\ spaces value\n" +
+            "empty=\n");
+        Assert.Equal("Progmasoft", properties["publisher"]);
+        Assert.Equal("https://example.com/a", properties["homepage"]);
+        Assert.Equal("Builds C & C++,on every host.", properties["description"]);
+        Assert.Equal("value", properties["key with spaces"]);
+        Assert.Equal(string.Empty, properties["empty"]);
+        Assert.Throws<FormatException>(() => JavaProperties.Parse("broken=\\u12"));
+    }
+
+    [Fact]
+    public void TheDescriptorOfAPluginJarIsReadAndChecked()
+    {
+        Assert.Null(TazelPluginDescriptor.TryRead(Jar(), out TazelPluginDescriptor? descriptor));
+        Assert.Equal(
+            new TazelPluginDescriptor(
+                "Progmasoft", "CMake", "0.1.0", 2, "Builds CMake projects.", ["First Author", "Second Author"],
+                "MPL-2.0", "https://example.com/cmake", null),
+            descriptor!,
+            new DescriptorComparer());
+
+        Assert.Equal("The JAR has no META-INF/services/com.progmasoft.api.tazel.dsl.plugin.ProjectPlugin.",
+            TazelPluginDescriptor.TryRead(Jar(service: false), out _));
+        Assert.Equal("The descriptor needs an exact semantic version.",
+            TazelPluginDescriptor.TryRead(Jar(version: "1.0"), out _));
+        Assert.Equal("The descriptor needs a name that is one identifier.",
+            TazelPluginDescriptor.TryRead(Jar(name: "c-make"), out _));
+        Assert.Equal("The homepage of the descriptor is not an https address.",
+            TazelPluginDescriptor.TryRead(Jar(homepage: "http\\://example.com"), out _));
+        Assert.Equal("The file is not a JAR.", TazelPluginDescriptor.TryRead("not a zip"u8.ToArray(), out _));
+    }
+
+    [Fact]
+    public async Task OnlyAnAllowedPublisherWithAnAccountPublishes()
+    {
+        (TazelPluginPublishing publishing, InMemoryAccountStore accounts, ITazelPluginCatalog catalog) = Publishing();
+        CancellationToken cancellationToken = TestContext.Current.CancellationToken;
+
+        PublishResult noAccount = await publishing.PublishAsync(Jar(), cancellationToken);
+        Assert.Equal("No Progmasoft Account is named 'Progmasoft'.", noAccount.Error);
+
+        await AddAccountAsync(accounts, "Progmasoft");
+        await AddAccountAsync(accounts, "Someone");
+        PublishResult notAllowed = await publishing.PublishAsync(Jar(publisher: "Someone"), cancellationToken);
+        Assert.Equal(
+            "Publishing Tazel plugins is open to Progmasoft for now; 'Someone' cannot publish yet.",
+            notAllowed.Error);
+
+        byte[] jar = Jar();
+        PublishResult published = await publishing.PublishAsync(jar, cancellationToken);
+        Assert.True(published.Published, published.Error);
+        string file = Path.Combine(artifactRoot, "dslplugins", "tazel", "Progmasoft", "CMake", "0.1.0", "CMake-0.1.0.jar");
+        Assert.Equal(jar, await File.ReadAllBytesAsync(file, cancellationToken));
+        TazelPlugin plugin = (await catalog.FindAsync("Progmasoft", "CMake", cancellationToken))!;
+        Assert.Equal(Convert.ToHexStringLower(SHA256.HashData(jar)), plugin.Versions.Single().Sha256);
+        Assert.Equal("MPL-2.0", plugin.License);
+
+        PublishResult again = await publishing.PublishAsync(Jar(description: "Another build."), cancellationToken);
+        Assert.Equal("Progmasoft.CMake 0.1.0 is published already.", again.Error);
+        Assert.Equal(jar, await File.ReadAllBytesAsync(file, cancellationToken));
+
+        PublishResult folded = await publishing.PublishAsync(Jar(name: "CMAKE", version: "0.2.0"), cancellationToken);
+        Assert.Equal(
+            "Progmasoft has a plugin whose name differs from 'CMAKE' only in letter case.", folded.Error);
+        Assert.False(File.Exists(Path.Combine(
+            artifactRoot, "dslplugins", "tazel", "Progmasoft", "CMAKE", "0.2.0", "CMAKE-0.2.0.jar")));
+    }
+
+    [Fact]
+    public async Task ViGetNeedsADescriptionAnAuthorAndALicense()
+    {
+        (TazelPluginPublishing publishing, InMemoryAccountStore accounts, _) = Publishing();
+        await AddAccountAsync(accounts, "Progmasoft");
+        PublishResult result = await publishing.PublishAsync(Jar(license: null), TestContext.Current.CancellationToken);
+        Assert.Equal(
+            "ViGet needs a description, at least one author and a license in the descriptor.", result.Error);
+    }
+
+    [Fact]
+    public async Task TheIndexIsWhatTazelReads()
+    {
+        await using AccountApiFactory factory = new();
+        ITazelPluginCatalog catalog = factory.Services.GetRequiredService<ITazelPluginCatalog>();
+        CancellationToken cancellationToken = TestContext.Current.CancellationToken;
+        Assert.Null(TazelPluginDescriptor.TryRead(Jar(), out TazelPluginDescriptor? descriptor));
+        await catalog.AddVersionAsync(descriptor!, new string('a', 64), 10, DateTimeOffset.UnixEpoch, cancellationToken);
+        await catalog.AddVersionAsync(
+            descriptor! with { Version = "0.2.0" }, new string('b', 64), 10, DateTimeOffset.UnixEpoch.AddDays(1),
+            cancellationToken);
+        await catalog.SetYankedAsync("Progmasoft", "CMake", "0.2.0", true, cancellationToken);
+        using HttpClient client = factory.CreateClient();
+
+        using JsonDocument index = JsonDocument.Parse(await client.GetStringAsync(
+            "/api/v1/viget/dslplugins/tazel/Progmasoft/CMake/index.json", cancellationToken));
+        Assert.Equal("Progmasoft", index.RootElement.GetProperty("publisher").GetString());
+        Assert.Equal("CMake", index.RootElement.GetProperty("name").GetString());
+        JsonElement[] versions = [.. index.RootElement.GetProperty("versions").EnumerateArray()];
+        Assert.Equal(["0.2.0", "0.1.0"], versions.Select(version => version.GetProperty("version").GetString()));
+        Assert.True(versions[0].GetProperty("yanked").GetBoolean());
+        Assert.Equal(2, versions[1].GetProperty("apiVersion").GetInt32());
+        Assert.Equal(new string('a', 64), versions[1].GetProperty("sha256").GetString());
+
+        using JsonDocument detail = JsonDocument.Parse(await client.GetStringAsync(
+            "/api/v1/viget/dslplugins/tazel/Progmasoft/CMake", cancellationToken));
+        Assert.Equal("0.1.0", detail.RootElement.GetProperty("latestVersion").GetString());
+        Assert.Equal(
+            "/dslplugins/tazel/Progmasoft/CMake/0.1.0/CMake-0.1.0.jar",
+            detail.RootElement.GetProperty("versions")[1].GetProperty("path").GetString());
+
+        using JsonDocument list = JsonDocument.Parse(
+            await client.GetStringAsync("/api/v1/viget/dslplugins/tazel", cancellationToken));
+        Assert.Equal("CMake", list.RootElement.GetProperty("plugins")[0].GetProperty("name").GetString());
+
+        Assert.Equal(HttpStatusCode.NotFound, (await client.GetAsync(
+            "/api/v1/viget/dslplugins/tazel/Progmasoft/Missing/index.json", cancellationToken)).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await client.GetAsync(
+            "/api/v1/viget/dslplugins/tazel/Progmasoft/not-a-name/index.json", cancellationToken)).StatusCode);
+    }
+
+    [Fact]
+    public async Task TheCommandPublishesAndYanks()
+    {
+        (TazelPluginPublishing publishing, InMemoryAccountStore accounts, ITazelPluginCatalog catalog) = Publishing();
+        await AddAccountAsync(accounts, "Progmasoft");
+        ServiceProvider services = new ServiceCollection()
+            .AddSingleton(publishing)
+            .AddSingleton(catalog)
+            .BuildServiceProvider();
+        string jar = Path.Combine(artifactRoot, "upload.jar");
+        Directory.CreateDirectory(artifactRoot);
+        await File.WriteAllBytesAsync(jar, Jar(), TestContext.Current.CancellationToken);
+        StringWriter output = new();
+        StringWriter errors = new();
+
+        Assert.Equal(0, await ViGetCommand.RunAsync(
+            services, ["publish-tazel-plugin", jar], output, errors, TestContext.Current.CancellationToken));
+        Assert.Contains("Published Progmasoft.CMake 0.1.0", output.ToString(), StringComparison.Ordinal);
+        Assert.Equal(0, await ViGetCommand.RunAsync(
+            services, ["yank-tazel-plugin", "Progmasoft", "CMake", "0.1.0"], output, errors,
+            TestContext.Current.CancellationToken));
+        Assert.True((await catalog.FindAsync("Progmasoft", "CMake", TestContext.Current.CancellationToken))!
+            .Versions.Single().Yanked);
+        Assert.Equal(1, await ViGetCommand.RunAsync(
+            services, ["publish-tazel-plugin", jar], output, errors, TestContext.Current.CancellationToken));
+        Assert.Equal(2, await ViGetCommand.RunAsync(
+            services, ["publish"], output, errors, TestContext.Current.CancellationToken));
+    }
+
+    private (TazelPluginPublishing, InMemoryAccountStore, ITazelPluginCatalog) Publishing()
+    {
+        InMemoryAccountStore accounts = new();
+        InMemoryTazelPluginCatalog catalog = new();
+        TazelPluginPublishing publishing = new(
+            catalog,
+            accounts,
+            Options.Create(new ViGetOptions { ArtifactRoot = artifactRoot }),
+            TimeProvider.System);
+        return (publishing, accounts, catalog);
+    }
+
+    private static async Task AddAccountAsync(InMemoryAccountStore accounts, string name) =>
+        await accounts.CreateAsync(
+            new AccountRecord(
+                Guid.NewGuid(),
+                name,
+                AccountNamePolicy.NormalizeForLookup(name),
+                $"{name}@example.com",
+                $"{name}@example.com".ToUpperInvariant(),
+                null,
+                null,
+                DateTimeOffset.UnixEpoch),
+            TestContext.Current.CancellationToken);
+
+    private static byte[] Jar(
+        string publisher = "Progmasoft",
+        string name = "CMake",
+        string version = "0.1.0",
+        string? description = "Builds CMake projects.",
+        string? license = "MPL-2.0",
+        string homepage = "https\\://example.com/cmake",
+        bool service = true)
+    {
+        using MemoryStream bytes = new();
+        using (ZipArchive archive = new(bytes, ZipArchiveMode.Create, leaveOpen: true))
+        {
+            List<string> lines =
+            [
+                "publisher=" + publisher,
+                "name=" + name,
+                "version=" + version,
+                "apiVersion=2",
+                "author.0=First Author",
+                "author.1=Second Author",
+                "homepage=" + homepage
+            ];
+            if (description is not null)
+            {
+                lines.Add("description=" + description);
+            }
+
+            if (license is not null)
+            {
+                lines.Add("license=" + license);
+            }
+
+            using (StreamWriter writer = new(archive.CreateEntry(TazelPluginDescriptor.DescriptorEntry).Open()))
+            {
+                writer.Write(string.Join('\n', lines) + "\n");
+            }
+
+            if (service)
+            {
+                using StreamWriter writer = new(archive.CreateEntry(TazelPluginDescriptor.ServiceEntry).Open());
+                writer.Write("com.example.CMakePlugin\n");
+            }
+        }
+
+        return bytes.ToArray();
+    }
+
+    /// <summary>Compares descriptors by value, with their authors as sequences.</summary>
+    private sealed class DescriptorComparer : IEqualityComparer<TazelPluginDescriptor>
+    {
+        public bool Equals(TazelPluginDescriptor? left, TazelPluginDescriptor? right) =>
+            left is not null && right is not null &&
+            left with { Authors = [] } == right with { Authors = [] } &&
+            left.Authors.SequenceEqual(right.Authors);
+
+        public int GetHashCode(TazelPluginDescriptor descriptor) => descriptor.Name.GetHashCode(StringComparison.Ordinal);
+    }
+}
diff --git a/apps/api/Accounts/IAccountStore.cs b/apps/api/Accounts/IAccountStore.cs
index efb7c5b..ccb4c02 100644
--- a/apps/api/Accounts/IAccountStore.cs
+++ b/apps/api/Accounts/IAccountStore.cs
@@ -31,6 +31,13 @@ internal interface IAccountStore
     /// <param name="cancellationToken">Cancels the operation.</param>
     /// <returns>The account, or <see langword="null"/> when it does not exist.</returns>
     ValueTask<AccountRecord?> FindByIdAsync(Guid id, CancellationToken cancellationToken);
+    /// <summary>Finds an account by its normalized name.</summary>
+    /// <param name="normalizedAccountName">
+    /// Upper-case account name, as <see cref="AccountNamePolicy.NormalizeForLookup"/> produces it.
+    /// </param>
+    /// <param name="cancellationToken">Cancels the operation.</param>
+    /// <returns>The account, or <see langword="null"/> when no account has this name.</returns>
+    ValueTask<AccountRecord?> FindByAccountNameAsync(string normalizedAccountName, CancellationToken cancellationToken);
     /// <summary>Stores a session, replacing one with the same token digest.</summary>
     /// <param name="session">The session to store.</param>
     /// <param name="cancellationToken">Cancels the operation.</param>
diff --git a/apps/api/Accounts/InMemoryAccountStore.cs b/apps/api/Accounts/InMemoryAccountStore.cs
index 8606443..2f9af9d 100644
--- a/apps/api/Accounts/InMemoryAccountStore.cs
+++ b/apps/api/Accounts/InMemoryAccountStore.cs
@@ -82,6 +82,19 @@ internal sealed class InMemoryAccountStore : IAccountStore
     }
 
     /// <inheritdoc/>
+    public ValueTask<AccountRecord?> FindByAccountNameAsync(
+        string normalizedAccountName,
+        CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        lock (gate)
+        {
+            return ValueTask.FromResult(
+                accountIdsByName.TryGetValue(normalizedAccountName, out Guid id) ? accountsById[id] : null);
+        }
+    }
+
+    /// <inheritdoc/>
     public ValueTask<AccountRecord?> FindByIdAsync(Guid id, CancellationToken cancellationToken)
     {
         cancellationToken.ThrowIfCancellationRequested();
diff --git a/apps/api/Accounts/PostgresAccountStore.cs b/apps/api/Accounts/PostgresAccountStore.cs
index a0e3444..3a3ea82 100644
--- a/apps/api/Accounts/PostgresAccountStore.cs
+++ b/apps/api/Accounts/PostgresAccountStore.cs
@@ -98,6 +98,12 @@ internal sealed class PostgresAccountStore(NpgsqlDataSource dataSource) : IAccou
         FindAccountAsync("google_subject", googleSubject, cancellationToken);
 
     /// <inheritdoc/>
+    public ValueTask<AccountRecord?> FindByAccountNameAsync(
+        string normalizedAccountName,
+        CancellationToken cancellationToken) =>
+        FindAccountAsync("normalized_account_name", normalizedAccountName, cancellationToken);
+
+    /// <inheritdoc/>
     public ValueTask<AccountRecord?> FindByIdAsync(Guid id, CancellationToken cancellationToken) =>
         FindAccountAsync("id", id, cancellationToken);
 
diff --git a/apps/api/Program.cs b/apps/api/Program.cs
index 476cbdb..873c120 100644
--- a/apps/api/Program.cs
+++ b/apps/api/Program.cs
@@ -9,8 +9,12 @@ using Microsoft.AspNetCore.HttpOverrides;
 using Progmasoft.Progmaweb.Api.Accounts;
 using Progmasoft.OAuth;
 using Progmasoft.Progmaweb.Api.Security;
+using Progmasoft.Progmaweb.Api.ViGet;
 
-WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
+// `viget ...` runs a command of ViGet with the configuration of the service instead of the service itself; its
+// arguments are not configuration.
+bool vigetCommand = ViGetCommand.IsCommand(args);
+WebApplicationBuilder builder = WebApplication.CreateBuilder(vigetCommand ? [] : args);
 
 builder.Services.Configure<AccountSessionOptions>(builder.Configuration.GetSection(AccountSessionOptions.SectionName));
 builder.Services.AddSingleton(TimeProvider.System);
@@ -21,6 +25,8 @@ builder.Services.AddSingleton<AccountService>();
 builder.Services.AddSingleton<SessionService>();
 // Progmasoft OAuth, the OAuth 2.1 and OpenID Connect provider on its own host; see OAuth/OAuthRegistration.cs.
 builder.Services.AddProgmasoftOAuth(builder.Configuration, accountStore, builder.Environment.IsProduction());
+// ViGet: the Tazel plugin catalog beside the accounts; see ViGet/ViGetEndpoints.cs.
+builder.Services.AddViGet(builder.Configuration, accountStore);
 builder.Services.AddAuthorization();
 AuthenticationBuilder authentication = builder.Services
     .AddAuthentication()
@@ -103,6 +109,13 @@ builder.WebHost.ConfigureKestrel(options => options.Limits.MaxRequestBodySize =
 
 WebApplication app = builder.Build();
 
+if (vigetCommand)
+{
+    Environment.ExitCode = await ViGetCommand.RunAsync(
+        app.Services, args[1..], Console.Out, Console.Error, CancellationToken.None);
+    return;
+}
+
 if (accountStore is AccountStoreKind.Memory)
 {
     AccountStoreRegistration.WarnThatAccountsAreInMemory(app.Logger);
@@ -134,6 +147,7 @@ app.MapGet("/api/v1/status", () => Results.Ok(new
 }));
 app.MapAccountEndpoints();
 app.MapProgmasoftOAuth();
+app.MapViGetEndpoints();
 
 app.Run();
 
diff --git a/apps/api/ViGet/JavaProperties.cs b/apps/api/ViGet/JavaProperties.cs
new file mode 100644
index 0000000..e55991e
--- /dev/null
+++ b/apps/api/ViGet/JavaProperties.cs
@@ -0,0 +1,149 @@
+// SPDX-FileCopyrightText: 2026 Progmasoft <support@progmasoft.com>
+// SPDX-License-Identifier: AGPL-3.0-or-later WITH AdditionRef-Progmasoft-Patent-Grant-1.1
+
+using System.Globalization;
+using System.Text;
+
+namespace Progmasoft.Progmaweb.Api.ViGet;
+
+/// <summary>Reads the text of a Java <c>.properties</c> file, as <c>java.util.Properties.load</c> does.</summary>
+/// <remarks>
+/// A logical line may continue over several lines with a trailing backslash; <c>#</c> and <c>!</c> start a comment
+/// line; a key ends at the first unescaped <c>=</c>, <c>:</c> or white space; and <c>\t</c>, <c>\n</c>, <c>\r</c>,
+/// <c>\f</c> and <c>\uXXXX</c> are escapes, while a backslash before any other character stands for that character.
+/// A later line with the same key replaces an earlier one.
+/// </remarks>
+internal static class JavaProperties
+{
+    /// <summary>Reads the properties of a text.</summary>
+    /// <param name="text">The text of the file, already decoded.</param>
+    /// <returns>The properties by key.</returns>
+    /// <exception cref="FormatException">A <c>\u</c> escape is not followed by four hexadecimal digits.</exception>
+    public static IReadOnlyDictionary<string, string> Parse(string text)
+    {
+        Dictionary<string, string> properties = new(StringComparer.Ordinal);
+        foreach (string line in LogicalLines(text))
+        {
+            int index = 0;
+            while (index < line.Length && IsBlank(line[index]))
+            {
+                index++;
+            }
+
+            if (index == line.Length || line[index] is '#' or '!')
+            {
+                continue;
+            }
+
+            int keyStart = index;
+            while (index < line.Length && !IsKeyEnd(line[index]))
+            {
+                index += line[index] == '\\' ? 2 : 1;
+            }
+
+            string key = Unescape(line[keyStart..Math.Min(index, line.Length)]);
+            while (index < line.Length && IsBlank(line[index]))
+            {
+                index++;
+            }
+
+            if (index < line.Length && line[index] is '=' or ':')
+            {
+                index++;
+                while (index < line.Length && IsBlank(line[index]))
+                {
+                    index++;
+                }
+            }
+
+            properties[key] = Unescape(line[index..]);
+        }
+
+        return properties;
+    }
+
+    /// <summary>Joins the physical lines that a trailing backslash continues.</summary>
+    private static IEnumerable<string> LogicalLines(string text)
+    {
+        string[] lines = text.Replace("\r\n", "\n", StringComparison.Ordinal).Replace('\r', '\n').Split('\n');
+        StringBuilder current = new();
+        bool continuing = false;
+        foreach (string physical in lines)
+        {
+            // A continued line loses the white space it starts with.
+            string line = continuing ? physical.TrimStart(' ', '\t', '\f') : physical;
+            int backslashes = 0;
+            for (int position = line.Length - 1; position >= 0 && line[position] == '\\'; position--)
+            {
+                backslashes++;
+            }
+
+            continuing = backslashes % 2 == 1;
+            current.Append(continuing ? line[..^1] : line);
+            if (!continuing)
+            {
+                yield return current.ToString();
+                current.Clear();
+            }
+        }
+
+        if (current.Length > 0)
+        {
+            yield return current.ToString();
+        }
+    }
+
+    private static bool IsBlank(char character) => character is ' ' or '\t' or '\f';
+
+    private static bool IsKeyEnd(char character) => character is '=' or ':' || IsBlank(character);
+
+    private static string Unescape(string text)
+    {
+        StringBuilder result = new(text.Length);
+        for (int index = 0; index < text.Length; index++)
+        {
+            char character = text[index];
+            if (character != '\\' || index + 1 == text.Length)
+            {
+                result.Append(character);
+                continue;
+            }
+
+            char escaped = text[++index];
+            switch (escaped)
+            {
+                case 't':
+                    result.Append('\t');
+                    break;
+                case 'n':
+                    result.Append('\n');
+                    break;
+                case 'r':
+                    result.Append('\r');
+                    break;
+                case 'f':
+                    result.Append('\f');
+                    break;
+                case 'u':
+                    if (text.Length - index - 1 < 4 ||
+                        !int.TryParse(
+                            text.AsSpan(index + 1, 4),
+                            NumberStyles.AllowHexSpecifier,
+                            CultureInfo.InvariantCulture,
+                            out int code))
+                    {
+                        throw new FormatException("A \\u escape needs four hexadecimal digits.");
+                    }
+
+                    result.Append((char)code);
+                    index += 4;
+                    break;
+                default:
+                    result.Append(escaped);
+                    break;
+            }
+        }
+
+        return result.ToString();
+    }
+}
diff --git a/apps/api/ViGet/PostgresTazelPluginCatalog.cs b/apps/api/ViGet/PostgresTazelPluginCatalog.cs
new file mode 100644
index 0000000..07fa86f
--- /dev/null
+++ b/apps/api/ViGet/PostgresTazelPluginCatalog.cs
@@ -0,0 +1,309 @@
+// SPDX-FileCopyrightText: 2026 Progmasoft <support@progmasoft.com>
+// SPDX-License-Identifier: AGPL-3.0-or-later WITH AdditionRef-Progmasoft-Patent-Grant-1.1
+
+using Npgsql;
+
+namespace Progmasoft.Progmaweb.Api.ViGet;
+
+/// <summary>The tables of <see cref="PostgresTazelPluginCatalog"/> and the steps that bring a database to them.</summary>
+/// <remarks>
+/// The same numbered steps as the account tables, in a version table of their own, <c>viget_schema_versions</c>.
+/// A step is never edited after it has been released.
+/// </remarks>
+internal static class ViGetSchema
+{
+    /// <summary>Key of the advisory lock that lets one process at a time change these tables.</summary>
+    private const long MigrationLockKey = 0x5669476574;
+
+    private static readonly string[] Steps =
+    [
+        // 1: Tazel plugins and their versions.
+        //
+        // A plugin is named by its publisher and its name as they are spelled; the unique index on their upper
+        // case keeps two plugins from differing only in letter case. A version is never removed, only yanked.
+        """
+        CREATE TABLE viget_tazel_plugins (
+            publisher   text        NOT NULL,
+            name        text        NOT NULL,
+            description text,
+            authors     text[]      NOT NULL,
+            license     text,
+            homepage    text,
+            repository  text,
+            updated_at  timestamptz NOT NULL,
+            PRIMARY KEY (publisher, name)
+        );
+
+        CREATE UNIQUE INDEX viget_tazel_plugins_folded_key ON viget_tazel_plugins (upper(publisher), upper(name));
+
+        CREATE TABLE viget_tazel_plugin_versions (
+            publisher    text        NOT NULL,
+            name         text        NOT NULL,
+            version      text        NOT NULL,
+            sha256       text        NOT NULL,
+            api_version  integer     NOT NULL,
+            size         bigint      NOT NULL,
+            published_at timestamptz NOT NULL,
+            yanked       boolean     NOT NULL DEFAULT false,
+            PRIMARY KEY (publisher, name, version),
+            FOREIGN KEY (publisher, name) REFERENCES viget_tazel_plugins (publisher, name)
+        );
+        """
+    ];
+
+    /// <summary>The version a database has after every step.</summary>
+    public static int CurrentVersion => Steps.Length;
+
+    /// <summary>Takes the steps a database has not taken yet, in one transaction.</summary>
+    /// <returns>The number of steps that were taken.</returns>
+    /// <exception cref="InvalidOperationException">The database has taken steps this program does not know.</exception>
+    public static async Task<int> ApplyAsync(NpgsqlDataSource dataSource, CancellationToken cancellationToken)
+    {
+        await using NpgsqlConnection connection = await dataSource.OpenConnectionAsync(cancellationToken);
+        await using NpgsqlTransaction transaction = await connection.BeginTransactionAsync(cancellationToken);
+        await ExecuteAsync(connection, transaction, $"SELECT pg_advisory_xact_lock({MigrationLockKey})", cancellationToken);
+        await ExecuteAsync(
+            connection,
+            transaction,
+            """
+            CREATE TABLE IF NOT EXISTS viget_schema_versions (
+                version    integer     PRIMARY KEY,
+                applied_at timestamptz NOT NULL DEFAULT now()
+            )
+            """,
+            cancellationToken);
+
+        int version;
+        await using (NpgsqlCommand read = new(
+            "SELECT coalesce(max(version), 0) FROM viget_schema_versions", connection, transaction))
+        {
+            version = (int)(await read.ExecuteScalarAsync(cancellationToken))!;
+        }
+
+        if (version > Steps.Length)
+        {
+            throw new InvalidOperationException(
+                $"The ViGet tables are at schema version {version}, and this program knows version {Steps.Length}.");
+        }
+
+        int taken = 0;
+        for (int step = version; step < Steps.Length; step++)
+        {
+            await ExecuteAsync(connection, transaction, Steps[step], cancellationToken);
+            await using NpgsqlCommand record = new(
+                "INSERT INTO viget_schema_versions (version) VALUES ($1)", connection, transaction);
+            record.Parameters.AddWithValue(step + 1);
+            await record.ExecuteNonQueryAsync(cancellationToken);
+            taken++;
+        }
+
+        await transaction.CommitAsync(cancellationToken);
+        return taken;
+    }
+
+    private static async Task ExecuteAsync(
+        NpgsqlConnection connection,
+        NpgsqlTransaction transaction,
+        string sql,
+        CancellationToken cancellationToken)
+    {
+        await using NpgsqlCommand command = new(sql, connection, transaction);
+        await command.ExecuteNonQueryAsync(cancellationToken);
+    }
+}
+
+/// <summary>The Tazel plugins of ViGet in PostgreSQL, beside the accounts.</summary>
+/// <param name="dataSource">Connections to the database of the accounts.</param>
+internal sealed class PostgresTazelPluginCatalog(NpgsqlDataSource dataSource) : ITazelPluginCatalog
+{