using GermanApp.Application.DTOs;
using GermanApp.Application.Interfaces;
using GermanApp.Application.DTOs.Auth;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Net;
using System.Threading;
using System.Threading.Tasks;

namespace GermanApp.Presentation.Controllers;

/// <summary>
/// API controller for admin operations.
/// All endpoints require Admin role.
/// This is part of the Presentation layer.
/// </summary>
[ApiController]
[Route("api/[controller]")]
[Authorize(Roles = "Admin")]
public class AdminController : ControllerBase
{
    private readonly IAdminService _adminService;
    private readonly IUserReportService _reportService;

    public AdminController(IAdminService adminService, IUserReportService reportService)
    {
        _adminService = adminService;
        _reportService = reportService;
    }

    // ============================================
    // USER MANAGEMENT ENDPOINTS
    // ============================================

    /// <summary>
    /// Gets all users (Admin only).
    /// </summary>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>List of all users</returns>
    [HttpGet("users")]
    [ProducesResponseType(typeof(IReadOnlyList<AdminUserListItemDto>), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetAllUsersAsync(CancellationToken cancellationToken = default)
    {
        var users = await _adminService.GetAllUsersAsync(cancellationToken);
        return Ok(users);
    }

    /// <summary>
    /// Gets a specific user by ID (Admin only).
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>The user DTO</returns>
    [HttpGet("users/{userId}")]
    [ProducesResponseType(typeof(AdminUserDto), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetUserByIdAsync(int userId, CancellationToken cancellationToken = default)
    {
        var user = await _adminService.GetUserByIdAsync(userId, cancellationToken);
        
        if (user == null)
            return NotFound();

        return Ok(user);
    }

    /// <summary>
    /// Updates a user's role (Admin only).
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="dto">The role update data</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>The updated user DTO</returns>
    [HttpPut("users/{userId}/role")]
    [ProducesResponseType(typeof(AdminUserDto), (int)HttpStatusCode.OK)]
    [ProducesResponseType(typeof(string), (int)HttpStatusCode.BadRequest)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> UpdateUserRoleAsync(
        int userId,
        [FromBody] UpdateUserRoleDto dto,
        CancellationToken cancellationToken = default)
    {
        try
        {
            var user = await _adminService.UpdateUserRoleAsync(userId, dto.Role, cancellationToken);
            
            if (user == null)
                return NotFound();

            return Ok(user);
        }
        catch (ArgumentException ex)
        {
            return BadRequest(ex.Message);
        }
    }

    /// <summary>
    /// Deletes a user (Admin only, cannot delete self).
    /// </summary>
    /// <param name="userId">The user ID to delete</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Success or error</returns>
    [HttpDelete("users/{userId}")]
    [ProducesResponseType((int)HttpStatusCode.NoContent)]
    [ProducesResponseType(typeof(string), (int)HttpStatusCode.BadRequest)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> DeleteUserAsync(int userId, CancellationToken cancellationToken = default)
    {
        try
        {
            var adminUserId = int.Parse(User.FindFirst("nameid")?.Value ?? "0");
            var result = await _adminService.DeleteUserAsync(userId, adminUserId, cancellationToken);
            
            if (!result)
                return NotFound();

            return NoContent();
        }
        catch (InvalidOperationException ex)
        {
            return BadRequest(ex.Message);
        }
    }

    // ============================================
    // DASHBOARD ENDPOINTS
    // ============================================

    /// <summary>
    /// Gets admin dashboard statistics.
    /// </summary>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Dashboard statistics</returns>
    [HttpGet("dashboard/stats")]
    [ProducesResponseType(typeof(AdminDashboardStatsDto), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetDashboardStatsAsync(CancellationToken cancellationToken = default)
    {
        var stats = await _adminService.GetDashboardStatsAsync(cancellationToken);
        return Ok(stats);
    }

    // ============================================
    // REPORT ENDPOINTS
    // ============================================

    /// <summary>
    /// Generates a progress report for a specific user.
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>User progress report</returns>
    [HttpGet("reports/users/{userId}")]
    [ProducesResponseType(typeof(UserProgressReportDto), (int)HttpStatusCode.OK)]
    [ProducesResponseType(typeof(string), (int)HttpStatusCode.BadRequest)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetUserReportAsync(int userId, CancellationToken cancellationToken = default)
    {
        try
        {
            var report = await _reportService.GenerateUserReportAsync(userId, cancellationToken);
            return Ok(report);
        }
        catch (ArgumentException ex)
        {
            return BadRequest(ex.Message);
        }
    }

    /// <summary>
    /// Generates progress reports for all users.
    /// </summary>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>List of all user progress reports</returns>
    [HttpGet("reports/all-users")]
    [ProducesResponseType(typeof(IReadOnlyList<UserProgressReportDto>), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetAllUserReportsAsync(CancellationToken cancellationToken = default)
    {
        var reports = await _reportService.GenerateAllUserReportsAsync(cancellationToken);
        return Ok(reports);
    }

    /// <summary>
    /// Gets lesson completion data for a user.
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>List of lesson completion data</returns>
    [HttpGet("reports/users/{userId}/lessons")]
    [ProducesResponseType(typeof(IReadOnlyList<LessonCompletionDto>), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetUserLessonProgressAsync(int userId, CancellationToken cancellationToken = default)
    {
        var progress = await _reportService.GetUserLessonProgressAsync(userId, cancellationToken);
        return Ok(progress);
    }

    /// <summary>
    /// Gets quiz results for a user.
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>List of quiz results</returns>
    [HttpGet("reports/users/{userId}/quizzes")]
    [ProducesResponseType(typeof(IReadOnlyList<UserQuizResultDto>), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetUserQuizResultsAsync(int userId, CancellationToken cancellationToken = default)
    {
        var results = await _reportService.GetUserQuizResultsAsync(userId, cancellationToken);
        return Ok(results);
    }

    /// <summary>
    /// Exports all user reports as CSV.
    /// </summary>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>CSV content</returns>
    [HttpGet("reports/export/csv")]
    [ProducesResponseType(typeof(string), (int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> ExportReportsAsCsvAsync(CancellationToken cancellationToken = default)
    {
        var csv = await _reportService.ExportReportsAsCsvAsync(cancellationToken);
        return Ok(new { CsvContent = csv });
    }

    /// <summary>
    /// Gets a specific user's full report (combined data).
    /// </summary>
    /// <param name="userId">The user ID</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Combined user report data</returns>
    [HttpGet("reports/users/{userId}/full")]
    [ProducesResponseType((int)HttpStatusCode.OK)]
    [ProducesResponseType((int)HttpStatusCode.NotFound)]
    [ProducesResponseType((int)HttpStatusCode.Unauthorized)]
    public async Task<IActionResult> GetUserFullReportAsync(int userId, CancellationToken cancellationToken = default)
    {
        try
        {
            var progressReportTask = _reportService.GenerateUserReportAsync(userId, cancellationToken);
            var lessonProgressTask = _reportService.GetUserLessonProgressAsync(userId, cancellationToken);
            var quizResultsTask = _reportService.GetUserQuizResultsAsync(userId, cancellationToken);

            await Task.WhenAll(progressReportTask, lessonProgressTask, quizResultsTask);

            return Ok(new
            {
                ProgressReport = await progressReportTask,
                LessonProgress = await lessonProgressTask,
                QuizResults = await quizResultsTask
            });
        }
        catch (ArgumentException ex)
        {
            return BadRequest(ex.Message);
        }
    }
}