using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using QuotifyBE.Data;
using QuotifyBE.Entities;
using QuotifyBE.DTOs;
using System.Threading.Tasks;
using QuotifyBE.Mapping;
using Microsoft.AspNetCore.Cors;
using Microsoft.EntityFrameworkCore;

namespace QuotifyBE.Controllers;


[ApiController]
[EnableCors]
[Route("api/v1/categories")]
[Produces("application/json")]
public class CategoryController : ControllerBase
{

    private readonly ApplicationDbContext _db;
    private readonly GeneralUseHelpers guhf;

    public CategoryController(ApplicationDbContext db, GeneralUseHelpers GUHF)
    {
        _db = db;
        guhf = GUHF;
    }

    // GET /api/v1/categories
    /// <summary>
    /// Get a category page
    /// </summary>
    /// <remarks>
    /// Can (and will) return an empty list if no categories are found in DB. <br/>
    /// Has CORS set.
    /// </remarks>
    /// <param name="page_no">The page number</param>
    /// <response code="200">Returned on valid request</response>
    /// <response code="404">Returned when requested page is invalid (page_no &lt;= 0)</response>
    [HttpGet("page/{page_no}")]
    [EnableCors]
    [ProducesResponseType(typeof(CategoryShortDTO), 200)]
    [ProducesResponseType(typeof(ErrorDTO), 404)]
    public async Task<IActionResult> GetCategoryPage(int page_no = 1)
    {
        // The following seems to be a bad idea, so I leave it as is. ~eee4
        // 
        // int totalCategories = await _db.Categories.CountAsync();
        // 
        // if (totalCategories <= 0)
        // {
        //     return NoContent(new ErrorDTO { Status = "error", Error_msg = "No categories to list" });
        // }

        const int PageSize = 10;

        if (page_no <= 0)
        {
            return NotFound(new ErrorDTO { Status = "error", Error_msg = "Numer strony musi być większy niż 0" });
        }

        // Get all the categories
        //List<Category> categories = await _db.Categories
        //                                    .ToListAsync();
        List<Category> categories = await _db.Categories
                                .Skip((page_no - 1) * PageSize)
                                .Take(PageSize)
                                .ToListAsync();

        // Convert them to a list of DTO
        List<CategoryShortDTO> result = categories
                                            .Select(c => c.ToCategoryShortDTO())
                                            .ToList();

        // Return to user
        return Ok(result);

    }

    // POST /api/v1/categories
    /// <summary>
    /// [AUTHED] Create a new category
    /// </summary>
    /// <remarks>
    /// Allows authorized users to create categories.
    /// <br/><br/>
    /// <b>Important!</b> 
    /// Category names are case insensitive. <br/>
    /// Has CORS set.
    /// </remarks>
    /// <response code="200">Returned on valid request</response>
    /// <response code="406">Returned when such category already exists (case insensitive)</response>
    [HttpPost]
    [Authorize]
    [EnableCors]
    [ProducesResponseType(typeof(CategoryShortDTO), 200)]
    [ProducesResponseType(typeof(ErrorDTO), 406)]
    public async Task<IActionResult> PostNewCategory([FromBody] NewCategoryDTO formCategory)
    {
        // Check if such category doesn't already exist
        Category? cat = await _db.Categories.FirstOrDefaultAsync(c => c.Name.ToLower() == formCategory.Name.ToLower());
        if (cat != null)
        {
            return StatusCode(406, new ErrorDTO { Status = "error", Error_msg = "This category already exists" });
        }

        // Create new category
        cat = new Category
        {
            Name = formCategory.Name,
            Description = formCategory.Description,
            CreatedAt = DateTime.UtcNow
        };

        // Add to DB
        await _db.Categories.AddAsync(cat);
        await _db.SaveChangesAsync();

        // And send back to the user as DTO
        return Ok(cat.ToCategoryShortDTO());

    }

    // DELETE /api/v1/categories
    /// <summary>
    /// [AUTHED] Delete a category
    /// </summary>
    /// <remarks>
    /// Allows authorized users to delete categories.
    /// <br/><br/>
    /// Has CORS set.
    /// </remarks>
    /// <param name="id">Id of the category which shall be deleted</param>
    /// <response code="200">Returned on valid request</response>
    /// <response code="404">Returned when no such category exists</response>
    [HttpDelete("{id}")]
    [Authorize]
    [EnableCors]
    [ProducesResponseType(200)]
    [ProducesResponseType(typeof(ErrorDTO), 404)]
    public async Task<IActionResult> DeleteCategory(int id)
    {
        // (Attempt to) find the category
        Category? cat = await _db.Categories
                            .FirstOrDefaultAsync(c => c.Id == id);
        // Failed?
        if (cat == null)
            return NotFound(new { status = "error", error_msg = "Category not found" });

        // Find all the QuoteId <-> CategoryId pairs for provided id
        List<QuoteCategory> quoteLinks = await _db.QuoteCategories
                                                .Where(qc => qc.CategoryId == id)
                                                .ToListAsync();

        // For each of the dependent quotes
        foreach (var link in quoteLinks) {
            // Remove all the associative pairs
            _db.QuoteCategories.Remove(link);
        }

        // Finally, remove the category
        _db.Categories.Remove(cat);
        await _db.SaveChangesAsync();

        // Return ok
        return Ok(new { Status = "ok" });
    }

    // PATCH /api/v1/categories/1
    /// <summary>
    /// [AUTHED] Modify an existing category
    /// </summary>
    /// <remarks>
    /// Allows authorized users to modify categories.
    /// <br/><br/>
    /// Has CORS set.
    /// </remarks>
    /// <param name="id">Id of the category which shall be modified</param>
    /// <param name="updatedCategory">DTO with new name and description. Id and creation date are ignored.</param>
    /// <response code="200">Returned on valid request</response>
    /// <response code="400">Returned when category name is empty or null</response>
    /// <response code="404">Returned when no such category exists</response>
    [HttpPatch("{id}")]
    [Authorize]
    [EnableCors]
    [ProducesResponseType(typeof(CategoryShortDTO), 200)]
    [ProducesResponseType(typeof(ErrorDTO), 400)]
    [ProducesResponseType(typeof(ErrorDTO), 404)]
    public async Task<IActionResult> EditCategory(int id, [FromBody] CategoryShortDTO updatedCategory)
    {
        // Find the category to modify
        Category? cat = await _db.Categories.FirstOrDefaultAsync(c => c.Id == id);

        // Failed?
        if (cat == null)
            return NotFound(new { status = "error", error_msg = "Category not found" });

        // Otherwise, ensure the category name is not empty or null
        if (string.IsNullOrWhiteSpace(updatedCategory.Name))
            return BadRequest(new ErrorDTO { Status = "error", Error_msg = "Category name cannot be empty." });

        // Update the fields
        cat.Name = updatedCategory.Name;
        cat.Description = updatedCategory.Description;
        // Note the user cannot modify the createdAt field,
        // and we do not store last modification date.
        await _db.SaveChangesAsync();

        // Return the modified category to user
        return Ok(cat.ToCategoryShortDTO());
    }

}