using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

namespace ScrumTaskboard.Controllers
{
    /// <summary>
    /// This is a controller of Tasks class includes all API's related to the Tasks.
    /// </summary>
    [Route("[controller]")]
    [ApiController]
    public class TasksController : ControllerBase
    {
        private readonly TaskContext _context;

        /// <summary>
        /// Initializes a new instance of the class.
        /// </summary>
        /// <param name="context"></param>
        public TasksController(TaskContext context)
        {
            _context = context;
        }

        // GET: api/tasks
        /// <summary>
        /// Retrieve all Tasks in DB.
        /// Result can be filtered using the Params.
        /// </summary>
        /// <param name="title">string value</param>
        /// <param name="userstoryid">ID of created Userstory</param>
        /// <param name="statusid">ID of created Status</param>
        /// <param name="assignedtoid">ID of the Assignedto</param>
        /// <param name="projectid">ID of created Project</param>
        /// <param name="priority">enum value</param>
        /// <returns>JSON list of all matching Tasks</returns>
#nullable enable
        [HttpGet]
        public async Task<ActionResult<IEnumerable<ScrumTask>>> GetTasks([FromQuery]string? title, [FromQuery]int? userstoryid, [FromQuery]int? statusid, [FromQuery]int? assignedtoid, [FromQuery]int? projectid, [FromQuery]ScrumPrio? priority)
        {
            var filtered = _context.Tasks.AsQueryable();

            if (title != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.Title.Contains(title));
            }
            if (userstoryid != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.UserstoryId == userstoryid);
            }
            if (statusid != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.StatusId == statusid);
            }
            if (assignedtoid != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.AssignedToId == assignedtoid);
            }
            if (projectid != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.ProjectId == projectid);
            }
            if (priority != null)
            {
                filtered = filtered.Where<ScrumTask>(t => t.Priority == priority);
            }


            return await filtered.ToListAsync();
        }
#nullable disable

        // GET: api/tasks/5
        /// <summary>
        /// Retrieve the Task by it's ID.
        /// </summary>
        /// <param name="id">ID of searched Task</param>
        /// <returns>JSON object</returns>
        [HttpGet("{id}")]
        public async Task<ActionResult<ScrumTask>> GetTask(int id)
        {
            var task = await _context.Tasks.FindAsync(id);

            if (task == null)
            {
                return NotFound();
            }

            return task;
        }

        // PUT: api/tasks/5
        /// <summary>
        /// Update the Task identified by it's ID.
        /// </summary>
        /// <param name="id">to edit Task's ID</param>
        /// <param name="task">modified Task</param>
        /// <returns>the proper status code</returns>
        [HttpPut("{id}")]
        public async Task<IActionResult> PutTask(int id, ScrumTask task)
        {
            // The task's ID must not be changed
            if (id != task.Id)
            {
                return BadRequest();
            }

            // Save the changed task in the context
            _context.Entry(task).State = EntityState.Modified;

            try
            {
                // Apply the changes to the database
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                // If the task does not exist, return status code 404
                if (!TaskExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return NoContent();
        }

        // POST: api/tasks
        /// <summary>
        /// Create a new Task.
        /// </summary>
        /// <param name="task">new Task</param>
        /// <returns>the proper status code</returns>
        [HttpPost]
        public async Task<ActionResult<ScrumTask>> PostTask(ScrumTask task)
        {
            _context.Tasks.Add(task);
            await _context.SaveChangesAsync();

            // The new task has been created and can be called up using the GetTask method
            return CreatedAtAction("GetTask", new { id = task.Id }, task);
        }

        // DELETE: api/tasks/5
        /// <summary>
        /// Delete a Task identified by it's ID.
        /// </summary>
        /// <param name="id">to delete Task's ID</param>
        /// <returns>the proper status code</returns>
        [HttpDelete("{id}")]
        public async Task<ActionResult<ScrumTask>> DeleteTask(int id)
        {
            var scrumTask = await _context.Tasks.FindAsync(id);
            if (scrumTask == null)
            {
                return NotFound();
            }

            // Remove the task from the context
            _context.Tasks.Remove(scrumTask);
            // Save the changes in the database
            await _context.SaveChangesAsync();

            return scrumTask;
        }

        /// <summary>
        /// Checks whether a task with the specified ID already exists.
        /// </summary>
        private bool TaskExists(int id)
        {
            return _context.Tasks.Any(e => e.Id == id);
        }
    }
}