using Microsoft.Data.SqlClient;
using Shouldly;
using Xunit;

namespace ZB.MOM.WW.OtOpcUa.Configuration.Tests;

/// <summary>
///     Introspects the applied schema via <c>sys.*</c> / <c>INFORMATION_SCHEMA.*</c> to confirm that
///     the Fluent-API DbContext produces the exact structure specified in
///     <c>docs/v2/config-db-schema.md</c>. Any change here is a deliberate decision — update the
///     schema doc first, then these tests.
/// </summary>
[Trait("Category", "SchemaCompliance")]
[Collection(nameof(SchemaComplianceCollection))]
public sealed class SchemaComplianceTests
{
    private readonly SchemaComplianceFixture _fixture;

    public SchemaComplianceTests(SchemaComplianceFixture fixture) => _fixture = fixture;

    [Fact]
    public void All_expected_tables_exist()
    {
        var expected = new[]
        {
            "ServerCluster", "ClusterNode", "ClusterNodeCredential", "ClusterNodeGenerationState",
            "ConfigGeneration", "ConfigAuditLog",
            "Namespace", "UnsArea", "UnsLine",
            "DriverInstance", "Device", "Equipment", "Tag", "PollGroup",
            "NodeAcl", "ExternalIdReservation",
            "DriverHostStatus",
        };

        var actual = QueryStrings(@"
SELECT name FROM sys.tables WHERE name <> '__EFMigrationsHistory' ORDER BY name;").ToHashSet();

        foreach (var table in expected)
            actual.ShouldContain(table, $"missing table: {table}");

        actual.Count.ShouldBe(expected.Length);
    }

    [Fact]
    public void Filtered_unique_indexes_match_schema_spec()
    {
        // (IndexName, Filter, Uniqueness) tuples — from OtOpcUaConfigDbContext Fluent config.
        // Kept here as a spec-level source of truth; the test ensures EF generated them verbatim.
        var expected = new[]
        {
            ("UX_ClusterNode_Primary_Per_Cluster", "([RedundancyRole]='Primary')"),
            ("UX_ClusterNodeCredential_Value", "([Enabled]=(1))"),
            ("UX_ConfigGeneration_Draft_Per_Cluster", "([Status]='Draft')"),
            ("UX_ExternalIdReservation_KindValue_Active", "([ReleasedAt] IS NULL)"),
        };

        var rows = QueryRows(@"
SELECT i.name AS IndexName, i.filter_definition
FROM   sys.indexes i
WHERE  i.is_unique = 1 AND i.has_filter = 1;",
            r => (Name: r.GetString(0), Filter: r.IsDBNull(1) ? null : r.GetString(1)));

        foreach (var (name, filter) in expected)
        {
            var match = rows.FirstOrDefault(x => x.Name == name);
            match.Name.ShouldBe(name, $"missing filtered unique index: {name}");
            NormalizeFilter(match.Filter).ShouldBe(NormalizeFilter(filter),
                $"filter predicate for {name} drifted");
        }
    }

    [Fact]
    public void Check_constraints_match_schema_spec()
    {
        var expected = new[]
        {
            "CK_ServerCluster_RedundancyMode_NodeCount",
            "CK_Device_DeviceConfig_IsJson",
            "CK_DriverInstance_DriverConfig_IsJson",
            "CK_PollGroup_IntervalMs_Min",
            "CK_Tag_TagConfig_IsJson",
            "CK_ConfigAuditLog_DetailsJson_IsJson",
        };

        var actual = QueryStrings("SELECT name FROM sys.check_constraints ORDER BY name;").ToHashSet();

        foreach (var ck in expected)
            actual.ShouldContain(ck, $"missing CHECK constraint: {ck}");
    }

    [Fact]
    public void Json_check_constraints_use_IsJson_function()
    {
        var rows = QueryRows(@"
SELECT cc.name, cc.definition
FROM   sys.check_constraints cc
WHERE  cc.name LIKE 'CK_%_IsJson';",
            r => (Name: r.GetString(0), Definition: r.GetString(1)));

        rows.Count.ShouldBeGreaterThanOrEqualTo(4);

        foreach (var (name, definition) in rows)
            definition.ShouldContain("isjson(", Case.Insensitive,
                $"{name} definition does not call ISJSON: {definition}");
    }

    [Fact]
    public void ConfigGeneration_Status_uses_nvarchar_enum_storage()
    {
        var rows = QueryRows(@"
SELECT c.COLUMN_NAME, c.DATA_TYPE, c.CHARACTER_MAXIMUM_LENGTH
FROM   INFORMATION_SCHEMA.COLUMNS c
WHERE  c.TABLE_NAME = 'ConfigGeneration' AND c.COLUMN_NAME = 'Status';",
            r => (Column: r.GetString(0), Type: r.GetString(1), Length: r.IsDBNull(2) ? (int?)null : r.GetInt32(2)));

        rows.Count.ShouldBe(1);
        rows[0].Type.ShouldBe("nvarchar");
        rows[0].Length.ShouldNotBeNull();
    }

    [Fact]
    public void Equipment_carries_Opc40010_identity_fields()
    {
        var columns = QueryStrings(@"
SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'Equipment';")
            .ToHashSet(StringComparer.OrdinalIgnoreCase);

        foreach (var col in new[]
                 {
                     "EquipmentUuid", "EquipmentId", "MachineCode", "ZTag", "SAPID",
                     "Manufacturer", "Model", "SerialNumber",
                 })
            columns.ShouldContain(col, $"Equipment missing expected column: {col}");
    }

    [Fact]
    public void Namespace_has_same_cluster_invariant_index()
    {
        // Decision #122: namespace logical IDs unique within a cluster + generation. The composite
        // unique index enforces that trust boundary.
        var indexes = QueryStrings(@"
SELECT i.name
FROM   sys.indexes i
JOIN   sys.tables  t ON i.object_id = t.object_id
WHERE  t.name = 'Namespace' AND i.is_unique = 1;").ToList();

        indexes.ShouldContain("UX_Namespace_Generation_LogicalId_Cluster");
    }

    private List<string> QueryStrings(string sql)
    {
        using var conn = _fixture.OpenConnection();
        using var cmd = new SqlCommand(sql, conn);
        using var reader = cmd.ExecuteReader();
        var result = new List<string>();
        while (reader.Read())
            result.Add(reader.GetString(0));
        return result;
    }

    private List<T> QueryRows<T>(string sql, Func<SqlDataReader, T> project)
    {
        using var conn = _fixture.OpenConnection();
        using var cmd = new SqlCommand(sql, conn);
        using var reader = cmd.ExecuteReader();
        var result = new List<T>();
        while (reader.Read())
            result.Add(project(reader));
        return result;
    }

    private static string? NormalizeFilter(string? filter) =>
        filter?.Replace(" ", string.Empty).Replace("(", string.Empty).Replace(")", string.Empty).ToLowerInvariant();
}