using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Migrations;
using Hua.Todo.Core.Entities;
using Xunit;
using System.Data.Common;
using Hua.Todo.Application.Repositories;

namespace Hua.Todo.Maui.Tests;

/// <summary>
/// 数据库初始化集成测试，覆盖 MauiProgram.InitializeDatabase 的 Migrate → EnsureCreated 回退链路。
/// 对应日志中 "no such table: T_Tasks" 错误场景，验证迁移链完整性与恢复能力。
/// </summary>
public class DatabaseInitializationTests : IDisposable
{
    private readonly SqliteConnection _connection;
    private readonly DbContextOptions<TodoDbContext> _options;

    public DatabaseInitializationTests()
    {
        _connection = new SqliteConnection("Data Source=:memory:");
        _connection.Open();

        _options = new DbContextOptionsBuilder<TodoDbContext>()
            .UseSqlite(_connection)
            .Options;
    }

    public void Dispose()
    {
        _connection.Dispose();
    }

    private TodoDbContext CreateContext()
    {
        return new TodoDbContext(_options);
    }

    /// <summary>
    /// 模拟 MauiProgram.InitializeDatabase 的 Migrate() 路径：
    /// 从零开始执行全部迁移，验证 T_Tasks 表存在。
    /// 对应日志第 1-21 行：Migrate() 失败场景。
    /// </summary>
    [Fact]
    public void InitializeDatabase_Migrate_FromScratch_CreatesTTasksTable()
    {
        // Arrange - 模拟 MauiProgram.InitializeDatabase 中的 Migrate() 调用
        using var context = CreateContext();

        // Act: 执行迁移（等同于 Migrate()）
        context.Database.Migrate();

        // Assert: T_Tasks 表存在
        var tables = GetTableNames(context);
        Assert.Contains("T_Tasks", tables);
    }

    /// <summary>
    /// 验证迁移后所有核心表存在。
    /// 对应日志第 23-27 行：查询 T_Tasks 失败场景。
    /// </summary>
    [Fact]
    public void InitializeDatabase_Migrate_AllCoreTablesExist()
    {
        using var context = CreateContext();
        context.Database.Migrate();

        var tables = GetTableNames(context);
        Assert.Contains("T_Tasks", tables);
        Assert.Contains("Attachments", tables);
        Assert.Contains("Users", tables);
        Assert.Contains("UserSessions", tables);
        Assert.Contains("SecurityPolicies", tables);
        Assert.Contains("AuditLogs", tables);
    }

    /// <summary>
    /// 验证 T_Tasks 表包含日志中查询的所有列。
    /// 对应日志第 24-26 行 SELECT 查询中引用的所有字段。
    /// </summary>
    [Fact]
    public void InitializeDatabase_TTasks_HasAllColumnsFromQuery()
    {
        using var context = CreateContext();
        context.Database.Migrate();

        var columns = GetColumnNames(context, "T_Tasks");

        // 日志第 24 行 SELECT 查询中引用的字段，必须全部存在
        Assert.Contains("Id", columns);
        Assert.Contains("AudioDuration", columns);
        Assert.Contains("Code", columns);
        Assert.Contains("ConcurrencyStamp", columns);
        Assert.Contains("CreationTime", columns);
        Assert.Contains("CreatorId", columns);
        Assert.Contains("DeleterId", columns);
        Assert.Contains("DeletionTime", columns);
        Assert.Contains("Description", columns);
        Assert.Contains("ExtraProperties", columns);
        Assert.Contains("IsCompleted", columns);
        Assert.Contains("IsDeleted", columns);
        Assert.Contains("LastModificationTime", columns);
        Assert.Contains("LastModifierId", columns);
        Assert.Contains("MeetingNotes", columns);
        Assert.Contains("ParentTaskId", columns);
        Assert.Contains("Priority", columns);
        Assert.Contains("TaskType", columns);
        Assert.Contains("Title", columns);
        Assert.Contains("UserId", columns);
    }

    /// <summary>
    /// 模拟 MauiProgram.InitializeDatabase 的 fallback 路径：
    /// Migrate 失败 → 删除数据库 → EnsureCreated 重建。
    /// 对应日志第 1 行 "Database initialization failed" 后的恢复流程。
    /// </summary>
    [Fact]
    public void InitializeDatabase_Fallback_EnsureCreated_AfterFailure()
    {
        // 使用文件数据库模拟 fallback 中的文件删除操作
        var tempDbPath = Path.Combine(Path.GetTempPath(), $"hua_todo_test_{Guid.NewGuid()}.db");
        try
        {
            var connectionString = $"Data Source={tempDbPath}";

            // 先创建一个损坏的数据库（有迁移历史但表被删除）
            SqliteConnection? conn1 = null;
            try
            {
                conn1 = new SqliteConnection(connectionString);
                conn1.Open();
                var options1 = new DbContextOptionsBuilder<TodoDbContext>()
                    .UseSqlite(conn1)
                    .Options;
                using var context1 = new TodoDbContext(options1);
                context1.Database.Migrate();
                // 手动删除 T_Tasks 模拟损坏
                context1.Database.ExecuteSqlRaw("DROP TABLE IF EXISTS T_Tasks;");
            }
            finally
            {
                // 显式关闭连接并清空连接池，确保文件句柄释放
                conn1?.Close();
                conn1?.Dispose();
                SqliteConnection.ClearAllPools();
            }

            // 模拟 InitializeDatabase fallback: 删除 DB 文件，重新创建
            if (File.Exists(tempDbPath))
            {
                File.Delete(tempDbPath);
                var walPath = tempDbPath + "-wal";
                var shmPath = tempDbPath + "-shm";
                if (File.Exists(walPath)) File.Delete(walPath);
                if (File.Exists(shmPath)) File.Delete(shmPath);
            }

            // EnsureCreated: 从当前模型创建 schema
            SqliteConnection? conn2 = null;
            try
            {
                conn2 = new SqliteConnection(connectionString);
                conn2.Open();
                var options2 = new DbContextOptionsBuilder<TodoDbContext>()
                    .UseSqlite(conn2)
                    .Options;
                using var context2 = new TodoDbContext(options2);

                // Act: EnsureCreated（fallback 路径）
                context2.Database.EnsureCreated();

                // Assert: T_Tasks 已重建
                var tables = GetTableNames(context2);
                Assert.Contains("T_Tasks", tables);
                Assert.Contains("Attachments", tables);
            }
            finally
            {
                conn2?.Close();
                conn2?.Dispose();
                SqliteConnection.ClearAllPools();
            }
        }
        finally
        {
            // 清理：确保所有连接池已释放
            SqliteConnection.ClearAllPools();
            GC.Collect();
            GC.WaitForPendingFinalizers();

            if (File.Exists(tempDbPath)) File.Delete(tempDbPath);
            var w = tempDbPath + "-wal";
            var s = tempDbPath + "-shm";
            if (File.Exists(w)) File.Delete(w);
            if (File.Exists(s)) File.Delete(s);
        }
    }

    /// <summary>
    /// 验证 Migrate 是幂等的：第二次调用不会报错。
    /// 模拟多次启动 MauiProgram 的场景。
    /// </summary>
    [Fact]
    public void InitializeDatabase_Migrate_Idempotent()
    {
        using var context = CreateContext();
        context.Database.Migrate();

        // 第二次 Migrate 不应抛出异常
        var exception = Record.Exception(() => context.Database.Migrate());
        Assert.Null(exception);
    }

    /// <summary>
    /// 验证迁移后可以执行日志中失败的查询。
    /// 对应日志第 23-27 行 SELECT 查询。
    /// </summary>
    [Fact]
    public void InitializeDatabase_CanExecuteQueryFromLog()
    {
        using var context = CreateContext();
        context.Database.Migrate();

        // 创建测试用户
        var userId = Guid.NewGuid();
        context.Users.Add(new UserEntity
        {
            Id = userId,
            UserName = "test",
            PasswordHash = "hash",
            PasswordSalt = "salt",
            Role = "User"
        });
        context.SaveChanges();

        // 插入测试任务
        var taskId = Guid.NewGuid();
        context.Tasks.Add(new TaskEntity
        {
            Id = taskId,
            UserId = userId,
            Title = "测试",
            Priority = TaskPriority.Medium,
            Code = "T001",
            CreationTime = DateTime.UtcNow,
            CreatorId = userId
        });
        context.SaveChanges();

        // 执行日志中的查询：LEFT JOIN T_Tasks ON ParentTaskId
        var tasks = context.Tasks
            .Include(t => t.ParentTask)
            .OrderBy(t => t.Id)
            .ToList();

        // 验证查询不抛异常且返回结果
        Assert.NotNull(tasks);
        Assert.NotEmpty(tasks);
        Assert.Contains(tasks, t => t.Title == "测试");
    }

    /// <summary>
    /// 验证迁移顺序正确：MakeTaskEntityAbpCompatible 在 AddMeetingAndDescriptionFields 之前执行。
    /// 这是日志中 "no such table: T_Tasks" 错误的根因验证。
    /// </summary>
    [Fact]
    public void InitializeDatabase_MigrationOrder_Correct()
    {
        using var context = CreateContext();
        context.Database.Migrate();

        var history = context.GetService<IHistoryRepository>();
        var appliedMigrations = history.GetAppliedMigrations()
            .Select(m => m.MigrationId)
            .ToList();

        // 找到两个迁移的索引位置
        var abpCompatIndex = appliedMigrations.FindIndex(m => m.Contains("MakeTaskEntityAbpCompatible"));
        var meetingFieldsIndex = appliedMigrations.FindIndex(m => m.Contains("AddMeetingAndDescriptionFields"));

        Assert.True(abpCompatIndex >= 0, "MakeTaskEntityAbpCompatible should be applied");
        Assert.True(meetingFieldsIndex >= 0, "AddMeetingAndDescriptionFields should be applied");
        // MakeTaskEntityAbpCompatible 必须在 AddMeetingAndDescriptionFields 之前
        Assert.True(abpCompatIndex < meetingFieldsIndex,
            $"MakeTaskEntityAbpCompatible (index {abpCompatIndex}) must be before AddMeetingAndDescriptionFields (index {meetingFieldsIndex})");
    }

    // ========== 辅助方法 ==========

    private static List<string> GetTableNames(TodoDbContext context)
    {
        return context.Database.SqlQueryRaw<string>(
            "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' AND name NOT LIKE '__EF%' ORDER BY name"
        ).ToList();
    }

    private static List<string> GetColumnNames(TodoDbContext context, string tableName)
    {
        var columns = new List<string>();
        var connection = context.Database.GetDbConnection();
        if (connection.State != System.Data.ConnectionState.Open)
            connection.Open();

        using var command = connection.CreateCommand();
        command.CommandText = $"PRAGMA table_info('{tableName}')";
        using var reader = command.ExecuteReader();
        while (reader.Read())
        {
            columns.Add(reader.GetString(1)); // name 列是第 2 列 (index 1)
        }
        return columns;
    }
}