using System.ComponentModel.DataAnnotations;
using System.IO.Abstractions;
using ErsatzTV.Application.Libraries;
using ErsatzTV.Controllers.Api.Requests;
using ErsatzTV.Core;
using ErsatzTV.Core.Api.MediaSources;
using ErsatzTV.Core.Interfaces.Locking;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Extensions;
using ErsatzTV.Filters;
using MediatR;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace ErsatzTV.Controllers.Api;

// Local library CRUD (design #202 §A.1, endpoints L1-L7). Every id-keyed mutation (L4/L5/L6) gets
// its real 404 from a controller pre-check, NOT from the wrapped handler: `.Apply`/`ToEitherAsync`
// both `.Join()` a `NotFoundError` into a plain `BaseError`, which maps to 422
// (see `ErsatzTV.Core.LanguageExtensions`) — so relying on the handler for 404 here would be dead
// code (design #202 §A.1 finding 9). This is check-then-act: a delete racing the pre-check falls
// through to the handler's own 422, which is accepted and documented, not silently hidden.
[ApiController]
[EndpointGroupName("general")]
public class LocalLibrariesController(
    IMediator mediator,
    IEntityLocker entityLocker,
    IFileSystem fileSystem,
    ILibraryRepository libraryRepository) : ControllerBase
{
    [HttpGet("/api/v1/libraries/local", Name = "GetLocalLibraries")]
    [Tags("Libraries")]
    [EndpointSummary("Get all local libraries")]
    [ProducesResponseType(typeof(List<LocalLibraryResponseModel>), StatusCodes.Status200OK)]
    public async Task<List<LocalLibraryResponseModel>> GetAll(CancellationToken cancellationToken)
    {
        List<LocalLibraryViewModel> libraries = await mediator.Send(new GetAllLocalLibraries(), cancellationToken);
        return libraries.Map(ProjectToResponseModel).ToList();
    }

    [HttpGet("/api/v1/libraries/local/{id:int}", Name = "GetLocalLibrary")]
    [Tags("Libraries")]
    [EndpointSummary("Get a local library by id")]
    [RequiresAuthentication]
    [ProducesResponseType(typeof(LocalLibraryDetailResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> GetById(int id, CancellationToken cancellationToken)
    {
        Option<LocalLibraryViewModel> maybeLibrary = await mediator.Send(new GetLocalLibraryById(id), cancellationToken);
        return await maybeLibrary.Match(
            Some: async vm => (IActionResult)new OkObjectResult(await ProjectToDetailResponseModel(vm, cancellationToken)),
            None: () => Task.FromResult(ApiResults.NotFoundProblem($"Local library {id} does not exist.")));
    }

    [HttpPost("/api/v1/libraries/local")]
    [Tags("Libraries")]
    [EndpointSummary("Create a local library")]
    [EndpointDescription(
        "The shared LibraryMediaKind enum includes Mixed, but it is rejected here with 422. Mixed exists "
        + "only for Jellyfin libraries, where the media server classifies each item; no local folder "
        + "scanner handles it.")]
    [ProducesResponseType(typeof(LocalLibraryResponseModel), StatusCodes.Status201Created)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Create(
        [Required][FromBody] CreateLocalLibraryRequest request,
        CancellationToken cancellationToken)
    {
        Either<BaseError, LocalLibraryViewModel> result = await mediator.Send(request.ToCommand(), cancellationToken);
        return result.ToCreatedResult(
            vm => $"/api/v1/libraries/local/{vm.Id}",
            ProjectToResponseModel);
    }

    [HttpPut("/api/v1/libraries/local/{id:int}")]
    [Tags("Libraries")]
    [EndpointSummary("Update a local library")]
    [EndpointDescription(
        "Replaces the library's name and full path list. MediaKind is immutable after create and is not " +
        "part of this request. Paths are identified by normalized path string, not id — a renamed path is a " +
        "delete-old + add-new (its id changes).")]
    [ProducesResponseType(typeof(LocalLibraryDetailResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Update(
        int id,
        [Required][FromBody] UpdateLocalLibraryRequest request,
        CancellationToken cancellationToken)
    {
        Option<LocalLibraryViewModel> existing = await mediator.Send(new GetLocalLibraryById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem($"Local library {id} does not exist.");
        }

        if (entityLocker.IsLibraryLocked(id))
        {
            return ApiResults.ConflictProblem(
                "Library scan in progress",
                $"Local library {id} is locked by an in-progress scan.");
        }

        Either<BaseError, LocalLibraryViewModel> result =
            await mediator.Send(request.ToCommand(id), cancellationToken);

        return await result.Match(
            Left: error => Task.FromResult(error.ToErrorResult()),
            Right: async _ =>
            {
                // reload via the same query GetById uses (api-conventions §7 write-path projection);
                // paths.Id may have changed for renamed/added paths.
                Option<LocalLibraryViewModel> refreshed =
                    await mediator.Send(new GetLocalLibraryById(id), cancellationToken);
                return await refreshed.Match(
                    Some: async vm => (IActionResult)new OkObjectResult(
                        await ProjectToDetailResponseModel(vm, cancellationToken)),
                    None: () => Task.FromResult(ApiResults.NotFoundProblem($"Local library {id} does not exist.")));
            });
    }

    [HttpDelete("/api/v1/libraries/local/{id:int}")]
    [Tags("Libraries")]
    [EndpointSummary("Delete a local library")]
    [ProducesResponseType(StatusCodes.Status204NoContent)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    public async Task<IActionResult> Delete(int id, CancellationToken cancellationToken)
    {
        Option<LocalLibraryViewModel> existing = await mediator.Send(new GetLocalLibraryById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem($"Local library {id} does not exist.");
        }

        if (entityLocker.IsLibraryLocked(id))
        {
            return ApiResults.ConflictProblem(
                "Library scan in progress",
                $"Local library {id} is locked by an in-progress scan.");
        }

        Either<BaseError, Unit> result = await mediator.Send(new DeleteLocalLibrary(id), cancellationToken);
        return result.ToDeletedResult();
    }

    [HttpPost("/api/v1/libraries/local/paths/{pathId:int}/move")]
    [Tags("Libraries")]
    [EndpointSummary("Move a local library path to another local library")]
    [EndpointDescription(
        "Moves a path (and its scanned media) from its current library to a different local library of the " +
        "same media kind. Blazor's move dialog enforces same-kind/different-library only client-side; this " +
        "endpoint enforces both server-side so API/MCP clients cannot bypass them.")]
    [ProducesResponseType(StatusCodes.Status204NoContent)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status409Conflict)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> MovePath(
        int pathId,
        [Required][FromBody] MoveLocalLibraryPathRequest request,
        CancellationToken cancellationToken)
    {
        Option<int> maybeSourceLibraryId = await libraryRepository.GetLibraryIdForPath(pathId);
        if (maybeSourceLibraryId.IsNone)
        {
            return ApiResults.NotFoundProblem($"Library path {pathId} does not exist.");
        }

        int sourceLibraryId = maybeSourceLibraryId.IfNone(0);
        if (entityLocker.IsLibraryLocked(sourceLibraryId))
        {
            return ApiResults.ConflictProblem(
                "Library scan in progress",
                $"Local library {sourceLibraryId} is locked by an in-progress scan.");
        }

        // residual check-then-act race (design #202 §C5): a concurrent delete of this path between
        // the pre-check above and this Send falls through to the handler's own 422, not a 404.
        Either<BaseError, Unit> result = await mediator.Send(request.ToCommand(pathId), cancellationToken);
        return result.ToDeletedResult();
    }

    [HttpPost("/api/v1/libraries/local/path-exists")]
    [Tags("Libraries")]
    [EndpointSummary("Check whether a filesystem path exists")]
    [EndpointDescription(
        "Server-side existence check for the SPA's add-path UX (a browser cannot call Directory.Exists). " +
        "This is a check-then-act convenience only — Create/Update still validate new paths at save time " +
        "(design #202 §C2).")]
    [ProducesResponseType(typeof(LocalPathCheckResponseModel), StatusCodes.Status200OK)]
    public IActionResult CheckPathExists([Required][FromBody] LocalPathCheckRequest request)
    {
        bool exists = !string.IsNullOrWhiteSpace(request.Path) && fileSystem.Directory.Exists(request.Path);
        return new OkObjectResult(new LocalPathCheckResponseModel(exists));
    }

    private LocalLibraryResponseModel ProjectToResponseModel(LocalLibraryViewModel vm) =>
        new(vm.Id, vm.Name, vm.MediaKind, entityLocker.IsLibraryLocked(vm.Id));

    private async Task<LocalLibraryDetailResponseModel> ProjectToDetailResponseModel(
        LocalLibraryViewModel vm,
        CancellationToken cancellationToken)
    {
        List<LocalLibraryPathViewModel> paths =
            await mediator.Send(new GetLocalLibraryPaths(vm.Id), cancellationToken);
        int mediaItemCount = await mediator.Send(new CountMediaItemsByLibrary(vm.Id), cancellationToken);

        var pathModels = new List<LocalLibraryPathResponseModel>();
        foreach (LocalLibraryPathViewModel path in paths)
        {
            int pathCount = await mediator.Send(new CountMediaItemsByLibraryPath(path.Id), cancellationToken);
            pathModels.Add(new LocalLibraryPathResponseModel(path.Id, path.Path, pathCount));
        }

        return new LocalLibraryDetailResponseModel(
            vm.Id,
            vm.Name,
            vm.MediaKind,
            entityLocker.IsLibraryLocked(vm.Id),
            mediaItemCount,
            pathModels);
    }
}