using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using DramaLing.Api.Data;
using DramaLing.Api.Models.Entities;
using Microsoft.AspNetCore.Authorization;
using System.Security.Claims;

namespace DramaLing.Api.Controllers;

[ApiController]
[Route("api/[controller]")]
[Authorize]
public class FlashcardsController : ControllerBase
{
    private readonly DramaLingDbContext _context;

    public FlashcardsController(DramaLingDbContext context)
    {
        _context = context;
    }

    private Guid GetUserId()
    {
        var userIdString = User.FindFirst(ClaimTypes.NameIdentifier)?.Value ??
                          User.FindFirst("sub")?.Value;

        if (Guid.TryParse(userIdString, out var userId))
            return userId;

        throw new UnauthorizedAccessException("Invalid user ID");
    }

    [HttpGet]
    public async Task<ActionResult> GetFlashcards(
        [FromQuery] Guid? setId,
        [FromQuery] string? search,
        [FromQuery] bool favoritesOnly = false,
        [FromQuery] int limit = 50,
        [FromQuery] int offset = 0)
    {
        try
        {
            var userId = GetUserId();

            var query = _context.Flashcards
                .Include(f => f.CardSet)
                .Where(f => f.UserId == userId);

            if (setId.HasValue)
                query = query.Where(f => f.CardSetId == setId);

            if (!string.IsNullOrEmpty(search))
                query = query.Where(f => f.Word.Contains(search) || f.Translation.Contains(search));

            if (favoritesOnly)
                query = query.Where(f => f.IsFavorite);

            var total = await query.CountAsync();
            var flashcards = await query
                .OrderByDescending(f => f.CreatedAt)
                .Skip(offset)
                .Take(Math.Min(limit, 100))
                .Select(f => new
                {
                    f.Id,
                    f.Word,
                    f.Translation,
                    f.Definition,
                    f.PartOfSpeech,
                    f.Pronunciation,
                    f.Example,
                    f.ExampleTranslation,
                    f.MasteryLevel,
                    f.TimesReviewed,
                    f.IsFavorite,
                    f.NextReviewDate,
                    f.CreatedAt,
                    CardSet = new
                    {
                        f.CardSet.Name,
                        f.CardSet.Color
                    }
                })
                .ToListAsync();

            return Ok(new
            {
                Success = true,
                Data = new
                {
                    Flashcards = flashcards,
                    Total = total,
                    HasMore = offset + limit < total
                }
            });
        }
        catch (UnauthorizedAccessException)
        {
            return Unauthorized(new { Success = false, Error = "Unauthorized" });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new
            {
                Success = false,
                Error = "Failed to fetch flashcards",
                Timestamp = DateTime.UtcNow
            });
        }
    }

    [HttpPost]
    public async Task<ActionResult> CreateFlashcard([FromBody] CreateFlashcardRequest request)
    {
        try
        {
            var userId = GetUserId();

            // 驗證卡組是否屬於用戶
            var cardSet = await _context.CardSets
                .FirstOrDefaultAsync(cs => cs.Id == request.CardSetId && cs.UserId == userId);

            if (cardSet == null)
                return NotFound(new { Success = false, Error = "Card set not found" });

            var flashcard = new Flashcard
            {
                Id = Guid.NewGuid(),
                UserId = userId,
                CardSetId = request.CardSetId,
                Word = request.Word.Trim(),
                Translation = request.Translation.Trim(),
                Definition = request.Definition.Trim(),
                PartOfSpeech = request.PartOfSpeech?.Trim(),
                Pronunciation = request.Pronunciation?.Trim(),
                Example = request.Example?.Trim(),
                ExampleTranslation = request.ExampleTranslation?.Trim()
            };

            _context.Flashcards.Add(flashcard);
            await _context.SaveChangesAsync();

            return Ok(new
            {
                Success = true,
                Data = flashcard,
                Message = "Flashcard created successfully"
            });
        }
        catch (UnauthorizedAccessException)
        {
            return Unauthorized(new { Success = false, Error = "Unauthorized" });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new
            {
                Success = false,
                Error = "Failed to create flashcard",
                Timestamp = DateTime.UtcNow
            });
        }
    }

    [HttpGet("{id}")]
    public async Task<ActionResult> GetFlashcard(Guid id)
    {
        try
        {
            var userId = GetUserId();

            var flashcard = await _context.Flashcards
                .Include(f => f.CardSet)
                .FirstOrDefaultAsync(f => f.Id == id && f.UserId == userId);

            if (flashcard == null)
                return NotFound(new { Success = false, Error = "Flashcard not found" });

            return Ok(new { Success = true, Data = flashcard });
        }
        catch (UnauthorizedAccessException)
        {
            return Unauthorized(new { Success = false, Error = "Unauthorized" });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new
            {
                Success = false,
                Error = "Failed to fetch flashcard",
                Timestamp = DateTime.UtcNow
            });
        }
    }

    [HttpPut("{id}")]
    public async Task<ActionResult> UpdateFlashcard(Guid id, [FromBody] UpdateFlashcardRequest request)
    {
        try
        {
            var userId = GetUserId();

            var flashcard = await _context.Flashcards
                .FirstOrDefaultAsync(f => f.Id == id && f.UserId == userId);

            if (flashcard == null)
                return NotFound(new { Success = false, Error = "Flashcard not found" });

            // 更新欄位
            if (!string.IsNullOrEmpty(request.Word))
                flashcard.Word = request.Word.Trim();
            if (!string.IsNullOrEmpty(request.Translation))
                flashcard.Translation = request.Translation.Trim();
            if (!string.IsNullOrEmpty(request.Definition))
                flashcard.Definition = request.Definition.Trim();
            if (request.PartOfSpeech != null)
                flashcard.PartOfSpeech = request.PartOfSpeech?.Trim();
            if (request.Pronunciation != null)
                flashcard.Pronunciation = request.Pronunciation?.Trim();
            if (request.Example != null)
                flashcard.Example = request.Example?.Trim();
            if (request.ExampleTranslation != null)
                flashcard.ExampleTranslation = request.ExampleTranslation?.Trim();
            if (request.IsFavorite.HasValue)
                flashcard.IsFavorite = request.IsFavorite.Value;

            flashcard.UpdatedAt = DateTime.UtcNow;
            await _context.SaveChangesAsync();

            return Ok(new
            {
                Success = true,
                Data = flashcard,
                Message = "Flashcard updated successfully"
            });
        }
        catch (UnauthorizedAccessException)
        {
            return Unauthorized(new { Success = false, Error = "Unauthorized" });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new
            {
                Success = false,
                Error = "Failed to update flashcard",
                Timestamp = DateTime.UtcNow
            });
        }
    }

    [HttpDelete("{id}")]
    public async Task<ActionResult> DeleteFlashcard(Guid id)
    {
        try
        {
            var userId = GetUserId();

            var flashcard = await _context.Flashcards
                .FirstOrDefaultAsync(f => f.Id == id && f.UserId == userId);

            if (flashcard == null)
                return NotFound(new { Success = false, Error = "Flashcard not found" });

            _context.Flashcards.Remove(flashcard);
            await _context.SaveChangesAsync();

            return Ok(new
            {
                Success = true,
                Message = "Flashcard deleted successfully"
            });
        }
        catch (UnauthorizedAccessException)
        {
            return Unauthorized(new { Success = false, Error = "Unauthorized" });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new
            {
                Success = false,
                Error = "Failed to delete flashcard",
                Timestamp = DateTime.UtcNow
            });
        }
    }
}

// DTOs
public class CreateFlashcardRequest
{
    public Guid CardSetId { get; set; }
    public string Word { get; set; } = string.Empty;
    public string Translation { get; set; } = string.Empty;
    public string Definition { get; set; } = string.Empty;
    public string? PartOfSpeech { get; set; }
    public string? Pronunciation { get; set; }
    public string? Example { get; set; }
    public string? ExampleTranslation { get; set; }
}

public class UpdateFlashcardRequest
{
    public string? Word { get; set; }
    public string? Translation { get; set; }
    public string? Definition { get; set; }
    public string? PartOfSpeech { get; set; }
    public string? Pronunciation { get; set; }
    public string? Example { get; set; }
    public string? ExampleTranslation { get; set; }
    public bool? IsFavorite { get; set; }
}