using Microsoft.Data.Sqlite;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using ZB.MOM.WW.LocalDb;

namespace ZB.MOM.WW.ScadaBridge.Host.Tests;

/// <summary>
/// Deferred-work register row 105 (arch-review 2026-08-19 P4-7 → LocalDb 0.3.3): a replicated
/// table must never be the parent of a foreign key with a row-mutating <c>ON DELETE</c> action
/// (<c>CASCADE</c> / <c>SET NULL</c> / <c>SET DEFAULT</c>). LocalDb's LWW applier upserts with
/// <c>INSERT OR REPLACE</c> under <c>foreign_keys=ON</c>, so the implicit delete would fire the
/// child action while change-capture is suppressed — the child rows change on the applying node
/// only and the pair diverges silently. LocalDb 0.3.3 refuses such a parent at
/// <c>RegisterReplicated</c> time, which on a site node is a BOOT failure of the replicating
/// pair. This test moves that discovery from the first replicated boot to the build: it walks
/// the real site schema (every table <c>SiteLocalDbSetup.OnReady</c> creates) and asserts none
/// of the ten <see cref="SiteLocalDbSetup.ReplicatedTables"/> has such an inbound FK.
/// </summary>
/// <remarks>
/// The schema is built with an UNREPLICATED config on purpose: a replicated one would make
/// 0.3.3's own guard throw first and mask which table/FK is at fault. The checker query mirrors
/// LocalDb's (<c>sqlite_master JOIN pragma_foreign_key_list</c>), and a negative control proves
/// it actually finds an offender.
/// </remarks>
public class SiteLocalDbReplicatedTableFkGuardTests
{
    [Fact]
    public void NoReplicatedTable_IsAParentOfARowMutatingOnDeleteForeignKey()
    {
        var path = TempDbPath();
        try
        {
            var config = ConfigFor(path);
            var services = new ServiceCollection();
            services.AddZbLocalDb(config, db => SiteLocalDbSetup.OnReady(db, config));
            using (var provider = services.BuildServiceProvider())
            using (var scope = provider.CreateScope())
            {
                // Resolving ILocalDb runs SqliteLocalDb's constructor and then OnReady — i.e.
                // creates every table the consolidated site file will ever hold.
                Assert.NotNull(scope.ServiceProvider.GetRequiredService<ILocalDb>());
            }

            var tables = TableNames(path);
            foreach (var table in SiteLocalDbSetup.ReplicatedTables)
            {
                Assert.Contains(table, tables); // the list and the schema must not drift apart

                var offenders = FindRowMutatingFkChildren(path, table);
                Assert.True(offenders.Count == 0,
                    $"Replicated table '{table}' is the parent of a row-mutating ON DELETE foreign key " +
                    $"({string.Join(", ", offenders)}). LocalDb 0.3.3 refuses to register it, so a " +
                    "replicating site pair would fail to boot — model cross-table cleanup as explicit " +
                    "application deletes instead (register row 105).");
            }
        }
        finally
        {
            SqliteConnection.ClearAllPools();
            Cleanup(path);
        }
    }

    [Fact]
    public void NegativeControl_CheckerFindsACascadingChild()
    {
        // The checker must be able to fail, or the test above proves nothing.
        var path = TempDbPath();
        try
        {
            using (var conn = Open(path))
            using (var cmd = conn.CreateCommand())
            {
                cmd.CommandText =
                    "CREATE TABLE parent_t (id TEXT PRIMARY KEY);" +
                    "CREATE TABLE child_cascade (id INTEGER PRIMARY KEY, parent_id TEXT REFERENCES parent_t(id) ON DELETE CASCADE);" +
                    "CREATE TABLE child_restrict (id INTEGER PRIMARY KEY, parent_id TEXT REFERENCES parent_t(id) ON DELETE RESTRICT);";
                cmd.ExecuteNonQuery();
            }

            var offenders = FindRowMutatingFkChildren(path, "parent_t");

            var only = Assert.Single(offenders);
            Assert.Equal("child_cascade.parent_id ON DELETE CASCADE", only);
        }
        finally
        {
            SqliteConnection.ClearAllPools();
            Cleanup(path);
        }
    }

    /// <summary>Same shape as LocalDb 0.3.3's <c>EnsureNoInboundActionOnDelete</c> query.</summary>
    private static List<string> FindRowMutatingFkChildren(string path, string parentTable)
    {
        using var conn = Open(path);
        using var cmd = conn.CreateCommand();
        cmd.CommandText =
            "SELECT m.name, fk.\"from\", fk.\"on_delete\" " +
            "FROM sqlite_master m JOIN pragma_foreign_key_list(m.name) fk " +
            "WHERE m.type = 'table' AND fk.\"table\" = $t COLLATE NOCASE " +
            "AND UPPER(fk.\"on_delete\") IN ('CASCADE', 'SET NULL', 'SET DEFAULT')";
        cmd.Parameters.AddWithValue("$t", parentTable);
        using var reader = cmd.ExecuteReader();
        var result = new List<string>();
        while (reader.Read())
            result.Add($"{reader.GetString(0)}.{reader.GetString(1)} ON DELETE {reader.GetString(2)}");
        return result;
    }

    private static HashSet<string> TableNames(string path)
    {
        using var conn = Open(path);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT name FROM sqlite_master WHERE type = 'table'";
        using var reader = cmd.ExecuteReader();
        var names = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        while (reader.Read()) names.Add(reader.GetString(0));
        return names;
    }

    private static SqliteConnection Open(string path)
    {
        var conn = new SqliteConnection(new SqliteConnectionStringBuilder { DataSource = path }.ToString());
        conn.Open();
        return conn;
    }

    private static string TempDbPath() =>
        Path.Combine(Path.GetTempPath(), $"scadabridge_fkguard_{Guid.NewGuid():N}.db");

    private static IConfiguration ConfigFor(string path) =>
        new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?> { ["LocalDb:Path"] = path })
            .Build();

    private static void Cleanup(string path)
    {
        foreach (var suffix in new[] { "", "-wal", "-shm" })
        {
            try { File.Delete(path + suffix); } catch (IOException) { }
        }
    }
}