using System.Data.Common;
using System.Globalization;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;

namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Tests;

/// <summary>
///     Pins the bind-parameter ceiling (Driver.Sql-002 / Driver.Sql.Dialect-002): a key-value group holding
///     more distinct <c>keyValue</c>s than the dialect's <see cref="ISqlDialect.MaxBindParameters"/> is split
///     into several plans over the <b>same</b> group key, rather than emitting one statement the provider
///     rejects.
///     <para><b>Why this is a correctness test and not a tuning one.</b> Over the ceiling the provider refuses
///     the statement <em>after</em> the connection opened, so every tag in the group publishes
///     <c>BadCommunicationError</c> on every poll, permanently — and a key-value (EAV) staging table is
///     precisely the shape that attracts thousands of tags on one table, which the group-key rule folds into
///     one group.</para>
///     <para>A single group emitting several plans needs <b>no reader change</b>: <c>SqlPollReader</c> runs
///     one command per plan and slices each plan's own <c>Members</c> back, so the last test here drives the
///     whole read path over a real database to prove exactly that.</para>
/// </summary>
public sealed class SqlGroupPlannerChunkingTests
{
    private static SqlTagDefinition KvTag(string name, string keyValue, string table = "dbo.TagValues")
        => new(name, SqlTagModel.KeyValue, table,
            KeyColumn: "tag_name", KeyValue: keyValue, ValueColumn: "num_value");

    // ---- the shipped ceilings ----

    /// <summary>
    ///     Oracle's real ceiling, on the real dialect: an <c>IN</c> expression list may hold 1000 entries, so
    ///     1001 distinct keys cannot be one statement. This is the shape the finding describes — no test-only
    ///     dialect involved.
    /// </summary>
    [Fact]
    public void AGroupBeyondTheOracleInListLimit_isSplit_ratherThanEmittedAsOneRejectedStatement()
    {
        var dialect = new OracleDialect();
        var tags = Enumerable.Range(0, 1001)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, dialect);

        plans.Count.ShouldBe(2);
        plans.ShouldAllBe(p => p.Parameters.Count <= 1000);
        plans.Sum(p => p.Parameters.Count).ShouldBe(1001);
    }

    /// <summary>
    ///     The same for SQL Server, whose 2100-parameter command cap is the other limit the finding names.
    /// </summary>
    [Fact]
    public void AGroupBeyondTheSqlServerParameterCap_isSplit()
    {
        var dialect = new SqlServerDialect();
        var tags = Enumerable.Range(0, dialect.MaxBindParameters + 1)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, dialect);

        plans.Count.ShouldBe(2);
        plans.ShouldAllBe(p => p.Parameters.Count <= dialect.MaxBindParameters);
    }

    // ---- how a split group is shaped ----

    [Fact]
    public void EachChunkBindsAtMostTheCeiling_andTheChunksCoverEveryKeyExactlyOnce()
    {
        var tags = Enumerable.Range(0, 7)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(3));

        plans.Count.ShouldBe(3);
        plans.Select(p => p.Parameters.Count).ShouldBe(new[] { 3, 3, 1 });
        plans.SelectMany(p => p.Parameters)
            .ShouldBe(Enumerable.Range(0, 7).Select(i => (object?)("Key" + i.ToString(CultureInfo.InvariantCulture))));
    }

    /// <summary>
    ///     Every member must land in the chunk that binds <em>its own</em> key — a member whose key is bound
    ///     by a different plan reads a result set that cannot contain its row and publishes
    ///     <c>BadNoData</c> forever, which is the quiet way to get this wrong.
    /// </summary>
    [Fact]
    public void EveryMemberLandsInTheChunkThatBindsItsOwnKey()
    {
        var tags = Enumerable.Range(0, 7)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(3));

        foreach (var plan in plans)
            foreach (var member in plan.Members)
                plan.Parameters.ShouldContain(member.KeyValue);

        // …and no member is dropped or duplicated across the split.
        plans.SelectMany(p => p.Members).Select(m => m.Name)
            .ShouldBe(tags.Select(t => t.Name), ignoreOrder: true);
        plans.Sum(p => p.Members.Count).ShouldBe(tags.Length);
    }

    /// <summary>
    ///     Two tags on one <c>keyValue</c> bind one parameter and must stay in one chunk — splitting them
    ///     would bind the same key twice and cost a whole extra round-trip for a row already fetched.
    /// </summary>
    [Fact]
    public void MembersSharingAKeyValue_stayInTheSameChunk()
    {
        var plans = SqlGroupPlanner.Plan(
        [
            KvTag("A", "K1"), KvTag("B", "K2"), KvTag("C", "K1"), KvTag("D", "K3"),
        ], new BindCeilingDialect(2));

        plans.Count.ShouldBe(2);
        plans[0].Parameters.ShouldBe(new object[] { "K1", "K2" });
        plans[0].Members.Select(m => m.Name).ShouldBe(new[] { "A", "B", "C" });
        plans[1].Parameters.ShouldBe(new object[] { "K3" });
        plans[1].Members.Select(m => m.Name).ShouldBe(new[] { "D" });
    }

    /// <summary>
    ///     Each chunk is its own command, so its markers restart at <c>k0</c> — carrying the global index
    ///     forward would emit <c>IN (@k3, @k4, @k5)</c> against a three-parameter command, which is legal but
    ///     makes a plan's SQL unreadable next to its own parameter list.
    /// </summary>
    [Fact]
    public void EachChunkNumbersItsMarkersFromZero_andTheSqlMatchesItsOwnParameters()
    {
        var tags = Enumerable.Range(0, 5)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(2));

        foreach (var plan in plans)
        {
            plan.ParameterNames.ShouldBe(
                Enumerable.Range(0, plan.Parameters.Count)
                    .Select(i => "@k" + i.ToString(CultureInfo.InvariantCulture)));
            plan.SqlText.ShouldEndWith("IN (" + string.Join(", ", plan.ParameterNames) + ")");
        }
    }

    /// <summary>All chunks of one group carry that group's key — the split is an execution detail, not a regrouping.</summary>
    [Fact]
    public void EveryChunkOfOneGroupCarriesTheSameGroupKey()
    {
        var tags = Enumerable.Range(0, 5)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(2));

        plans.Count.ShouldBeGreaterThan(1);
        plans.Select(p => p.GroupKey).Distinct().Count().ShouldBe(1);
    }

    /// <summary>
    ///     The falsifiability control. Chunking must not fragment an ordinary group: a planner that split
    ///     eagerly (or off a stale count) would pass every test above and quietly turn one round-trip per
    ///     source into N.
    /// </summary>
    [Theory]
    [InlineData(1)]
    [InlineData(2)]
    [InlineData(3)]
    public void AGroupAtOrUnderTheCeiling_stillEmitsExactlyOnePlan(int distinctKeys)
    {
        var tags = Enumerable.Range(0, distinctKeys)
            .Select(i => KvTag("T" + i.ToString(CultureInfo.InvariantCulture),
                "Key" + i.ToString(CultureInfo.InvariantCulture)))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(3));

        plans.Count.ShouldBe(1);
        plans[0].Members.Count.ShouldBe(distinctKeys);
    }

    /// <summary>
    ///     Two groups that each need splitting stay separate, and the chunks of one never mix with the other's
    ///     — the split happens inside a group, after grouping.
    /// </summary>
    [Fact]
    public void TwoOversizedGroups_areSplitIndependently()
    {
        var tags = Enumerable.Range(0, 3).Select(i => KvTag("A" + i, "K" + i, "dbo.First"))
            .Concat(Enumerable.Range(0, 3).Select(i => KvTag("B" + i, "K" + i, "dbo.Second")))
            .ToArray();

        var plans = SqlGroupPlanner.Plan(tags, new BindCeilingDialect(2));

        plans.Count.ShouldBe(4);
        // Group order still follows the input order of each group's first member (dbo.First, then dbo.Second),
        // and a group's own chunks stay adjacent and in key order.
        plans.Select(p => p.Members[0].Table).ShouldBe(["dbo.First", "dbo.First", "dbo.Second", "dbo.Second"]);
    }

    /// <summary>A wide-row plan binds at most one value, so a ceiling of 1 must not disturb it.</summary>
    [Fact]
    public void AWideRowPlan_isUnaffectedByTheCeiling()
    {
        var tag = new SqlTagDefinition("A", SqlTagModel.WideRow, "dbo.LatestStatus",
            ColumnName: "oven_temp", RowSelectorColumn: "station_id", RowSelectorValue: "7");

        var plans = SqlGroupPlanner.Plan([tag], new BindCeilingDialect(1));

        plans.Count.ShouldBe(1);
        plans[0].Parameters.Count.ShouldBe(1);
    }

    /// <summary>
    ///     A dialect reporting a ceiling below 1 cannot be chunked to — it must fail loudly rather than loop
    ///     forever or emit an empty <c>IN ()</c> list, which is a syntax error on every backend.
    /// </summary>
    [Theory]
    [InlineData(0)]
    [InlineData(-1)]
    public void ADialectReportingANonPositiveCeiling_isRejected(int ceiling)
        => Should.Throw<ArgumentException>(
            () => SqlGroupPlanner.Plan([KvTag("A", "K1")], new BindCeilingDialect(ceiling)));

    // ---- the whole read path, over a real database ----

    /// <summary>
    ///     Drives <see cref="SqlPollReader"/> over the SQLite fixture with a ceiling of 1, so three keys become
    ///     three plans, and asserts every tag still reads its own value. This is what proves several plans per
    ///     group need <b>no reader change</b> — the claim the chunking design rests on.
    /// </summary>
    [Fact]
    public async Task ThePollReader_readsEveryTagCorrectly_whenOneGroupIsSplitAcrossSeveralPlans()
    {
        using var fixture = new SqlitePollFixture();
        SqlTagDefinition[] tags =
        [
            Fixture("Speed", SqlitePollFixture.PresentKey),
            Fixture("Pressure", SqlitePollFixture.SecondPresentKey),
            Fixture("Missing", SqlitePollFixture.AbsentKey),
        ];

        var reader = new SqlPollReader(
            fixture.Factory, fixture.ConnectionString, new BindCeilingDialect(1),
            commandTimeout: TimeSpan.FromSeconds(10), operationTimeout: TimeSpan.FromSeconds(15),
            maxConcurrentGroups: 4, nullIsBad: false,
            resolve: reference => tags.FirstOrDefault(t => t.Name == reference));

        var snapshots = await reader.ReadAsync(["Speed", "Pressure", "Missing"], CancellationToken.None);

        snapshots[0].Value.ShouldBe(SqlitePollFixture.PresentValue);
        snapshots[0].StatusCode.ShouldBe(SqlStatusCodes.Good);
        snapshots[1].Value.ShouldBe(SqlitePollFixture.SecondPresentValue);
        snapshots[1].StatusCode.ShouldBe(SqlStatusCodes.Good);
        snapshots[2].StatusCode.ShouldBe(SqlStatusCodes.BadNoData);
    }

    private static SqlTagDefinition Fixture(string name, string keyValue)
        => new(name, SqlTagModel.KeyValue, SqlitePollFixture.KeyValueTable,
            KeyColumn: SqlitePollFixture.KeyColumn, KeyValue: keyValue,
            ValueColumn: SqlitePollFixture.ValueColumn,
            TimestampColumn: SqlitePollFixture.TimestampColumn);

    /// <summary>
    ///     A <b>test-only</b> dialect that reports a caller-chosen <see cref="ISqlDialect.MaxBindParameters"/>
    ///     and delegates everything else to <see cref="SqliteDialect"/> — so a chunked plan can be asserted on
    ///     at a readable size <em>and</em> actually executed against the fixture database.
    ///     <para>A decorator rather than a subclass, for the reason the other fakes here give:
    ///     <see cref="SqliteDialect"/> is sealed, and <c>new</c>-hiding a member would leave interface dispatch
    ///     calling the original, so the substitution would silently not happen.</para>
    /// </summary>
    private sealed class BindCeilingDialect(int maxBindParameters) : ISqlDialect
    {
        private static readonly SqliteDialect Inner = new();

        public int MaxBindParameters { get; } = maxBindParameters;

        public SqlProvider Provider => Inner.Provider;

        public DbProviderFactory Factory => Inner.Factory;

        public string LivenessSql => Inner.LivenessSql;

        public string SingleRowLimitPrefix => Inner.SingleRowLimitPrefix;

        public string SingleRowLimitSuffix => Inner.SingleRowLimitSuffix;

        public string ListSchemasSql => Inner.ListSchemasSql;

        public string DefaultSchemaSql => Inner.DefaultSchemaSql;

        public string ListTablesSql => Inner.ListTablesSql;

        public string ListColumnsSql => Inner.ListColumnsSql;

        public string ParameterMarker(string baseName) => Inner.ParameterMarker(baseName);

        public string ParameterBindName(string baseName) => Inner.ParameterBindName(baseName);

        public void ConfigureCommand(DbCommand command) => Inner.ConfigureCommand(command);

        public string QuoteIdentifier(string ident) => Inner.QuoteIdentifier(ident);

        public DriverDataType MapColumnType(string sqlDataType) => Inner.MapColumnType(sqlDataType);
    }
}