using System.Reflection;
using Data.SeaHavenIndustries;
using Data.SeaHavenIndustries.Migrations;
using Microsoft.Data.SqlClient;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Migrations;

namespace SeaHavenIndustries.Tests;

public class SH138SiteContactsSqlServerTests
{
    private const string LocalDbMaster =
        @"Server=(localdb)\MSSQLLocalDB;Database=master;Trusted_Connection=True;TrustServerCertificate=True;Connect Timeout=3";

    [Fact]
    public async Task SH138_SiteContacts_MigrationAddsNullableIntOrderColumn_WhenLocalDbAvailable()
    {
        var masterConnectionString = await ResolveMasterConnectionStringAsync();
        if (masterConnectionString == null)
            return;

        var dbName = $"SH138Migration_{Guid.NewGuid():N}";
        var connectionString = WithDatabase(masterConnectionString, dbName);

        try
        {
            await CreateDatabaseAsync(masterConnectionString, dbName);

            await using var connection = new SqlConnection(connectionString);
            await connection.OpenAsync();

            await using (var createTables = connection.CreateCommand())
            {
                createTables.CommandText =
                    """
                    CREATE TABLE Contacts (
                        Id int NOT NULL IDENTITY PRIMARY KEY,
                        FirstName nvarchar(max) NULL,
                        PhoneNumber nvarchar(max) NULL
                    );
                    """;
                await createTables.ExecuteNonQueryAsync();
            }

            var options = new DbContextOptionsBuilder<ApplicationDbContext>()
                .UseSqlServer(connection)
                .Options;

            await using var context = new ApplicationDbContext(options);
            await ApplyMigrationUpAsync(context, new SH138_SiteContacts());

            await using (var columnCmd = connection.CreateCommand())
            {
                columnCmd.CommandText =
                    """
                    SELECT t.name
                    FROM sys.columns c
                    JOIN sys.types t ON c.user_type_id = t.user_type_id
                    WHERE c.object_id = OBJECT_ID(N'Contacts')
                      AND c.name = N'SiteContactOrder';
                    """;
                var columnType = await columnCmd.ExecuteScalarAsync();
                Assert.Equal("int", columnType);
            }

            await using (var nullableCmd = connection.CreateCommand())
            {
                nullableCmd.CommandText =
                    """
                    SELECT c.is_nullable
                    FROM sys.columns c
                    WHERE c.object_id = OBJECT_ID(N'Contacts')
                      AND c.name = N'SiteContactOrder';
                    """;
                var isNullable = await nullableCmd.ExecuteScalarAsync();
                Assert.Equal(true, isNullable);
            }
        }
        finally
        {
            await DropDatabaseAsync(masterConnectionString, dbName);
        }
    }

    private static async Task ApplyMigrationUpAsync(ApplicationDbContext context, Migration migration)
    {
        var builder = new MigrationBuilder(context.Database.ProviderName!);
        var up = typeof(Migration).GetMethod("Up", BindingFlags.Instance | BindingFlags.NonPublic)
                 ?? throw new InvalidOperationException("Migration.Up not found.");
        up.Invoke(migration, [builder]);

        var sqlGenerator = context.GetService<IMigrationsSqlGenerator>();
        var commands = sqlGenerator.Generate(builder.Operations, model: null);
        foreach (var command in commands)
            await context.Database.ExecuteSqlRawAsync(command.CommandText);
    }

    private static async Task<string?> ResolveMasterConnectionStringAsync()
    {
        var configured = Environment.GetEnvironmentVariable("SH138_SQLSERVER_MASTER");
        var candidate = !string.IsNullOrWhiteSpace(configured)
            ? WithDatabase(configured, "master")
            : OperatingSystem.IsWindows() ? LocalDbMaster : null;

        if (candidate == null)
            return null;

        try
        {
            await using var connection = new SqlConnection(candidate);
            await connection.OpenAsync();
            return candidate;
        }
        catch (SqlException)
        {
            return null;
        }
        catch (InvalidOperationException)
        {
            return null;
        }
    }

    private static async Task CreateDatabaseAsync(string masterConnectionString, string dbName)
    {
        var quoted = QuoteSqlServerIdentifier(dbName);
        await using var connection = new SqlConnection(masterConnectionString);
        await connection.OpenAsync();
        await using var command = connection.CreateCommand();
        command.CommandText = $"CREATE DATABASE {quoted};";
        await command.ExecuteNonQueryAsync();
    }

    private static async Task DropDatabaseAsync(string masterConnectionString, string dbName)
    {
        try
        {
            var quoted = QuoteSqlServerIdentifier(dbName);
            await using var connection = new SqlConnection(masterConnectionString);
            await connection.OpenAsync();
            await using var command = connection.CreateCommand();
            command.CommandText =
                $"""
                 IF DB_ID(@dbName) IS NOT NULL
                 BEGIN
                     ALTER DATABASE {quoted} SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
                     DROP DATABASE {quoted};
                 END
                 """;
            command.Parameters.AddWithValue("@dbName", dbName);
            await command.ExecuteNonQueryAsync();
        }
        catch
        {
            // Best-effort cleanup for ephemeral LocalDB databases.
        }
    }

    private static string QuoteSqlServerIdentifier(string name) =>
        "[" + name.Replace("]", "]]", StringComparison.Ordinal) + "]";

    private static string WithDatabase(string connectionString, string database)
    {
        var builder = new SqlConnectionStringBuilder(connectionString)
        {
            InitialCatalog = database
        };
        return builder.ConnectionString;
    }
}