using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Text.RegularExpressions;
using System.Threading.Channels;
using ErsatzTV.Application;
using ErsatzTV.Application.MediaCollections;
using ErsatzTV.Controllers.Api.Requests;
using ErsatzTV.Core;
using ErsatzTV.Core.Api.Trakt;
using ErsatzTV.Core.Interfaces.Locking;
using ErsatzTV.Extensions;
using MediatR;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace ErsatzTV.Controllers.Api;

[ApiController]
public partial class TraktController(
    IMediator mediator,
    ChannelWriter<IBackgroundServiceRequest> workerChannel,
    IEntityLocker entityLocker) : ControllerBase
{
    private const int MaxPageSize = 100;

    [HttpGet("/api/v1/trakt/lists", Name = "GetTraktLists")]
    [Tags("Trakt")]
    [EndpointSummary("Get paged Trakt lists")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(PagedTraktListsResponseModel), StatusCodes.Status200OK)]
    public async Task<PagedTraktListsResponseModel> GetAll(
        [FromQuery]
        [Description("0-based page index: the first page is 0, not 1. A negative value is clamped to 0.")]
        int pageNum = 0,
        [FromQuery]
        [Description("Rows per page (default 100); capped at 100 for this endpoint. The page offset is derived from the effective (capped) size, so a larger value narrows the page instead of widening the offset.")]
        int pageSize = 100,
        CancellationToken cancellationToken = default)
    {
        int clampedPageNum = Math.Max(0, pageNum);
        int clampedPageSize = Math.Clamp(pageSize, 1, MaxPageSize);

        PagedTraktListsViewModel result = await mediator.Send(
            new GetPagedTraktLists(clampedPageNum, clampedPageSize),
            cancellationToken);

        return new PagedTraktListsResponseModel(
            result.TotalCount,
            result.Page.Map(ProjectToResponseModel).ToList());
    }

    [HttpGet("/api/v1/trakt/lists/{id:int}", Name = "GetTraktListById")]
    [Tags("Trakt")]
    [EndpointSummary("Get a Trakt list by id")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TraktListResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> GetById(int id, CancellationToken cancellationToken)
    {
        Option<TraktListViewModel> result = await mediator.Send(new GetTraktListById(id), cancellationToken);
        return result.Map(ProjectToResponseModel).ToGetResult();
    }

    [HttpPost("/api/v1/trakt/lists")]
    [Tags("Trakt")]
    [EndpointSummary("Add a Trakt list by URL")]
    [EndpointDescription(
        "Dispatches to the same background worker channel used by the classic UI's \"Add Trakt List\" dialog; " +
        "the list is fetched, saved, and matched asynchronously. Poll GET /api/v1/trakt/status while busy.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(StatusCodes.Status202Accepted)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    public async Task<IActionResult> Add(
        [Required][FromBody] AddTraktListRequest request,
        CancellationToken cancellationToken)
    {
        if (!IsValidTraktListUrl(request.Url))
        {
            return new UnprocessableEntityObjectResult(
                CreateProblemDetails(422, "Validation failed", "Invalid Trakt list url"));
        }

        return await EnqueueWithTraktLock(AddTraktList.FromUrl(request.Url), cancellationToken);
    }

    [HttpPost("/api/v1/trakt/lists/{id:int}/match")]
    [Tags("Trakt")]
    [EndpointSummary("Match a Trakt list's items")]
    [EndpointGroupName("general")]
    [ProducesResponseType(StatusCodes.Status202Accepted)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    public async Task<IActionResult> Match(int id, CancellationToken cancellationToken)
    {
        Option<TraktListViewModel> existing = await mediator.Send(new GetTraktListById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        return await EnqueueWithTraktLock(new MatchTraktListItems(id), cancellationToken);
    }

    [HttpDelete("/api/v1/trakt/lists/{id:int}")]
    [Tags("Trakt")]
    [EndpointSummary("Delete a Trakt list")]
    [EndpointGroupName("general")]
    [ProducesResponseType(StatusCodes.Status202Accepted)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    public async Task<IActionResult> Delete(int id, CancellationToken cancellationToken)
    {
        Option<TraktListViewModel> existing = await mediator.Send(new GetTraktListById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        return await EnqueueWithTraktLock(new DeleteTraktList(id), cancellationToken);
    }

    [HttpPut("/api/v1/trakt/lists/{id:int}")]
    [Tags("Trakt")]
    [EndpointSummary("Update a Trakt list's settings")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TraktListResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Update(
        int id,
        [Required][FromBody] UpdateTraktListRequest request,
        CancellationToken cancellationToken)
    {
        Option<TraktListViewModel> existing = await mediator.Send(new GetTraktListById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        Option<BaseError> maybeError = await mediator.Send(
            new UpdateTraktList(id, request.AutoRefresh, request.GeneratePlaylist),
            cancellationToken);

        foreach (BaseError error in maybeError)
        {
            return error.ToErrorResult();
        }

        Option<TraktListViewModel> updated = await mediator.Send(new GetTraktListById(id), cancellationToken);
        return updated.Map(ProjectToResponseModel).ToGetResult();
    }

    [HttpGet("/api/v1/trakt/status", Name = "GetTraktStatus")]
    [Tags("Trakt")]
    [EndpointSummary("Get Trakt background operation status")]
    [EndpointDescription(
        "Wraps IEntityLocker.IsTraktLocked() — the HTTP-observable substitute for the Blazor page's live lock " +
        "event. The SPA polls this while add/match/delete are in flight.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TraktStatusResponseModel), StatusCodes.Status200OK)]
    public TraktStatusResponseModel GetStatus() => new(entityLocker.IsTraktLocked());

    private static TraktListResponseModel ProjectToResponseModel(TraktListViewModel viewModel) =>
        new(
            viewModel.Id,
            viewModel.TraktId,
            viewModel.Slug,
            viewModel.Name,
            viewModel.ItemCount,
            viewModel.MatchCount,
            viewModel.AutoRefresh,
            viewModel.GeneratePlaylist);

    private async Task<IActionResult> EnqueueWithTraktLock(
        IBackgroundServiceRequest request,
        CancellationToken cancellationToken)
    {
        if (!entityLocker.LockTrakt())
        {
            return ConflictProblem();
        }

        try
        {
            await workerChannel.WriteAsync(request, cancellationToken);
        }
        catch
        {
            // the background handler only unlocks when it receives the message;
            // if enqueueing fails (e.g. request aborted), release the lock here or it is held forever
            entityLocker.UnlockTrakt();
            throw;
        }

        return new AcceptedResult();
    }

    private static ConflictObjectResult ConflictProblem() =>
        new ConflictObjectResult(
            CreateProblemDetails(
                409,
                "Trakt operation in progress",
                "A Trakt background operation is already in progress"));

    private static ProblemDetails CreateProblemDetails(int status, string title, string detail) =>
        new()
        {
            Status = status,
            Title = title,
            Detail = detail
        };

    // The following mirrors AddTraktListHandler.ValidateUrl (ErsatzTV.Application/MediaCollections/Commands/
    // AddTraktListHandler.cs). That method is private to the handler, operates on the handler's own request type,
    // and returns a handler-private record, so it can't be called from here directly — replicated minimally so the
    // controller can reject an obviously-invalid URL with a synchronous 422 before dispatching to the background
    // worker (which otherwise would silently no-op on a bad URL, since AddTraktListHandler's own ValidateUrl runs
    // fire-and-forget on the worker channel).
    [GeneratedRegex(@"https:\/\/(?:app\.)?trakt\.tv\/users\/([\w\-_]+)\/(?:lists\/)?([\w\-_]+)")]
    private static partial Regex UriTraktListRegex();

    [GeneratedRegex(@"https:\/\/(?:app\.)?trakt\.tv\/lists\/([\w\-_]+)\/([\w\-_]+)")]
    private static partial Regex UriTraktListRegex2();

    [GeneratedRegex(@"([\w\-_]+)\/(?:lists\/)?([\w\-_]+)")]
    private static partial Regex ShorthandTraktListRegex();

    private static bool IsValidTraktListUrl(string url)
    {
        if (string.IsNullOrWhiteSpace(url))
        {
            return false;
        }

        Match match = Uri.IsWellFormedUriString(url, UriKind.Absolute)
            ? MatchTraktListUrl(url)
            : ShorthandTraktListRegex().Match(url);

        return match.Success;
    }

    private static Match MatchTraktListUrl(string url)
    {
        Match match = UriTraktListRegex().Match(url);
        if (!match.Success)
        {
            match = UriTraktListRegex2().Match(url);
        }

        return match;
    }
}