using System.ComponentModel.DataAnnotations;
using ErsatzTV.Application.Scheduling;
using ErsatzTV.Controllers.Api.Requests;
using ErsatzTV.Core;
using ErsatzTV.Core.Api.Scheduling;
using ErsatzTV.Extensions;
using MediatR;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace ErsatzTV.Controllers.Api;

[ApiController]
public class TemplateController(IMediator mediator) : ControllerBase
{
    [HttpGet("/api/v1/templates/groups", Name = "GetTemplateGroups")]
    [Tags("Templates")]
    [EndpointSummary("Get all template groups")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(List<TemplateGroupResponseModel>), StatusCodes.Status200OK)]
    public async Task<List<TemplateGroupResponseModel>> GetGroups(CancellationToken cancellationToken)
    {
        List<TemplateGroupViewModel> groups = await mediator.Send(new GetAllTemplateGroups(), cancellationToken);
        return groups.Map(ProjectToResponseModel).ToList();
    }

    [HttpPost("/api/v1/templates/groups")]
    [Tags("Templates")]
    [EndpointSummary("Create a template group")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TemplateGroupResponseModel), StatusCodes.Status201Created)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> CreateGroup(
        [Required][FromBody] CreateTemplateGroupRequest request,
        CancellationToken cancellationToken)
    {
        Either<BaseError, TemplateGroupViewModel> result =
            await mediator.Send(request.ToCommand(), cancellationToken);
        return result.ToCreatedResult(
            vm => $"/api/v1/templates/groups/{vm.Id}",
            vm => ProjectToResponseModel(vm));
    }

    [HttpDelete("/api/v1/templates/groups/{id:int}")]
    [Tags("Templates")]
    [EndpointSummary("Delete a template group")]
    [EndpointDescription(
        "Deletes the template group. The database cascade removes every template (and its items) in the group.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(StatusCodes.Status204NoContent)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> DeleteGroup(int id, CancellationToken cancellationToken)
    {
        List<TemplateGroupViewModel> groups = await mediator.Send(new GetAllTemplateGroups(), cancellationToken);
        if (groups.All(g => g.Id != id))
        {
            return ApiResults.NotFoundProblem();
        }

        Option<BaseError> result = await mediator.Send(new DeleteTemplateGroup(id), cancellationToken);
        return result.Match<IActionResult>(
            Some: error => error.ToErrorResult(),
            None: () => new NoContentResult());
    }

    [HttpGet("/api/v1/templates")]
    [Tags("Templates")]
    [EndpointSummary("Get all templates")]
    [EndpointDescription(
        "Returns every template. Pass templateGroupId to filter to the templates in a single template group.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(List<TemplateResponseModel>), StatusCodes.Status200OK)]
    public async Task<List<TemplateResponseModel>> GetAll(
        [FromQuery] int? templateGroupId,
        CancellationToken cancellationToken)
    {
        List<TemplateViewModel> templates = templateGroupId is { } groupId
            ? await mediator.Send(new GetTemplatesByTemplateGroupId(groupId), cancellationToken)
            : await mediator.Send(new GetAllTemplates(), cancellationToken);
        return templates.Map(ProjectToResponseModel).ToList();
    }

    [HttpGet("/api/v1/templates/{id:int}", Name = "GetTemplateById")]
    [Tags("Templates")]
    [EndpointSummary("Get a template by id")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TemplateResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> GetById(int id, CancellationToken cancellationToken)
    {
        Option<TemplateViewModel> result = await mediator.Send(new GetTemplateById(id), cancellationToken);
        return result.Map(ProjectToResponseModel).ToGetResult();
    }

    [HttpPost("/api/v1/templates")]
    [Tags("Templates")]
    [EndpointSummary("Create a template")]
    [EndpointDescription("Creates an empty template in the given template group.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TemplateResponseModel), StatusCodes.Status201Created)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Create(
        [Required][FromBody] CreateTemplateRequest request,
        CancellationToken cancellationToken)
    {
        Either<BaseError, TemplateViewModel> result = await mediator.Send(request.ToCommand(), cancellationToken);
        return result.ToCreatedResult(
            vm => $"/api/v1/templates/{vm.Id}",
            vm => ProjectToResponseModel(vm));
    }

    [HttpDelete("/api/v1/templates/{id:int}")]
    [Tags("Templates")]
    [EndpointSummary("Delete a template")]
    [EndpointGroupName("general")]
    [ProducesResponseType(StatusCodes.Status204NoContent)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> Delete(int id, CancellationToken cancellationToken)
    {
        Option<TemplateViewModel> existing = await mediator.Send(new GetTemplateById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        Option<BaseError> result = await mediator.Send(new DeleteTemplate(id), cancellationToken);
        return result.Match<IActionResult>(
            Some: error => error.ToErrorResult(),
            None: () => new NoContentResult());
    }

    [HttpGet("/api/v1/templates/{id:int}/items")]
    [Tags("Templates")]
    [EndpointSummary("Get template items")]
    [EndpointDescription(
        "Returns the template's items and a strong ETag of the template's version. Pass that ETag back as " +
        "If-Match on the replace (PUT) to detect a concurrent edit (issue #253).")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(List<TemplateItemResponseModel>), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    public async Task<IActionResult> GetItems(int id, CancellationToken cancellationToken)
    {
        Option<TemplateViewModel> template = await mediator.Send(new GetTemplateById(id), cancellationToken);
        if (template.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        // The items GET returns children, not the root, so read the template's version for the ETag.
        ConcurrencyHeaders.SetETag(Response, template.Map(t => t.Version).IfNone(0));

        List<TemplateItemViewModel> items = await mediator.Send(new GetTemplateItems(id), cancellationToken);
        return new OkObjectResult(
            items.OrderBy(i => i.StartTime.TimeOfDay).Map(ProjectToResponseModel).ToList());
    }

    [HttpPut("/api/v1/templates/{id:int}")]
    [Tags("Templates")]
    [EndpointSummary("Replace a template and its items")]
    [EndpointDescription(
        "Replaces the template's name and its full item list. Each item assigns a block to a start time of day; " +
        "items must not overlap (an item's end time is its start time plus the assigned block's duration). " +
        "Send the ETag from the items GET as If-Match to reject a stale overwrite with 412 (issue #253); " +
        "a successful response carries the new ETag.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TemplateWithItemsResponseModel), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status412PreconditionFailed)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Replace(
        int id,
        [Required][FromBody] ReplaceTemplateRequest request,
        CancellationToken cancellationToken)
    {
        IfMatchCondition ifMatch = ConcurrencyHeaders.ParseIfMatch(Request);
        if (ifMatch.Kind is IfMatchKind.Malformed)
        {
            return new BadRequestObjectResult(
                new ProblemDetails
                {
                    Status = StatusCodes.Status400BadRequest,
                    Title = "Invalid If-Match header",
                    Detail = "If-Match must be a strong ETag of the resource version (e.g. \"3\") or \"*\"."
                });
        }

        Option<TemplateViewModel> maybeTemplate = await mediator.Send(new GetTemplateById(id), cancellationToken);
        if (maybeTemplate.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        int templateGroupId = maybeTemplate.Map(t => t.TemplateGroupId).IfNone(0);

        Either<BaseError, List<TemplateItemViewModel>> result =
            await mediator.Send(request.ToCommand(templateGroupId, id, ifMatch.ExpectedVersions), cancellationToken);

        return await result.Match(
            Left: error => Task.FromResult(error.ToErrorResult()),
            Right: async _ =>
            {
                // Reload the root (version) FIRST, then the items, so the emitted ETag is never newer than
                // the returned items (issue #253 fail-safe ordering; matches BlockController). Returning the
                // handler's item snapshot alongside a separately re-queried version could pair stale items
                // with a newer ETag — a client would then silently overwrite the interleaving write.
                Option<TemplateViewModel> refreshed = await mediator.Send(new GetTemplateById(id), cancellationToken);
                List<TemplateItemViewModel> items = await mediator.Send(new GetTemplateItems(id), cancellationToken);
                return refreshed.Match(
                    Some: vm =>
                    {
                        // Return the new ETag so a same-tab second save doesn't 412 against its own write.
                        ConcurrencyHeaders.SetETag(Response, vm.Version);
                        return (IActionResult)new OkObjectResult(ProjectToWithItemsResponseModel(vm, items));
                    },
                    None: () => ApiResults.NotFoundProblem());
            });
    }

    [HttpPost("/api/v1/templates/{id:int}/copy")]
    [Tags("Templates")]
    [EndpointSummary("Copy a template")]
    [EndpointDescription("Copies the template and its items into another (or the same) template group under a new name.")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(TemplateResponseModel), StatusCodes.Status201Created)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status422UnprocessableEntity)]
    public async Task<IActionResult> Copy(
        int id,
        [Required][FromBody] CopyTemplateRequest request,
        CancellationToken cancellationToken)
    {
        Option<TemplateViewModel> existing = await mediator.Send(new GetTemplateById(id), cancellationToken);
        if (existing.IsNone)
        {
            return ApiResults.NotFoundProblem();
        }

        Either<BaseError, TemplateViewModel> result =
            await mediator.Send(request.ToCommand(id), cancellationToken);
        return result.ToCreatedResult(
            vm => $"/api/v1/templates/{vm.Id}",
            vm => ProjectToResponseModel(vm));
    }

    private static TemplateGroupResponseModel ProjectToResponseModel(TemplateGroupViewModel vm) =>
        new(vm.Id, vm.Name, vm.TemplateCount);

    private static TemplateResponseModel ProjectToResponseModel(TemplateViewModel vm) =>
        new(vm.Id, vm.TemplateGroupId, vm.GroupName, vm.Name);

    private static TemplateWithItemsResponseModel ProjectToWithItemsResponseModel(
        TemplateViewModel vm,
        List<TemplateItemViewModel> items) =>
        new(
            vm.Id,
            vm.TemplateGroupId,
            vm.GroupName,
            vm.Name,
            items.OrderBy(i => i.StartTime.TimeOfDay).Map(ProjectToResponseModel).ToList());

    private static TemplateItemResponseModel ProjectToResponseModel(TemplateItemViewModel vm) =>
        new(vm.BlockId, vm.BlockName, (int)(vm.EndTime - vm.StartTime).TotalMinutes, vm.StartTime.TimeOfDay);
}