using FluentResults;
using Microsoft.EntityFrameworkCore;
using Tnsu.ApprovalRoute.Application.Common.Errors;
using Tnsu.ApprovalRoute.Domain.Entities;
using Tnsu.ApprovalRoute.Domain.Enums;
using Tnsu.ApprovalRoute.Infrastructure.Persistence;

namespace Tnsu.ApprovalRoute.Application.TemplateRouteSteps;

public sealed class TemplateRouteStepService(ApprovalRouteDbContext db)
{
    public async Task<Result<IReadOnlyList<TemplateRouteStepDto>>> ListAsync(Guid routeId, CancellationToken cancellationToken)
    {
        var items = await db.TemplateRouteSteps.AsNoTracking()
            .Where(x => x.RouteId == routeId)
            .OrderBy(x => x.OrderNo)
            .Select(x => new TemplateRouteStepDto(
                x.Id, x.OrderNo, x.ExecutorEmail, x.Position, x.ProjectRole, x.HeadType, x.Status, x.RouteId, x.AllowReassignToOtherApprovers))
            .ToListAsync(cancellationToken);

        return Result.Ok<IReadOnlyList<TemplateRouteStepDto>>(items);
    }

    public async Task<Result<TemplateRouteStepDto>> GetAsync(Guid routeId, Guid id, CancellationToken cancellationToken)
    {
        var entity = await db.TemplateRouteSteps.AsNoTracking()
            .FirstOrDefaultAsync(x => x.Id == id && x.RouteId == routeId, cancellationToken);

        return entity is null
            ? Result.Fail<TemplateRouteStepDto>(new NotFoundError("Шаг маршрута", id))
            : Result.Ok(ToDto(entity));
    }

    public async Task<Result<TemplateRouteStepDto>> CreateAsync(Guid routeId, CreateTemplateRouteStepRequest r, CancellationToken cancellationToken)
    {
        var route = await db.TemplateRoutes.FirstOrDefaultAsync(x => x.Id == routeId, cancellationToken);
        if (route is null)
            return Result.Fail<TemplateRouteStepDto>(new NotFoundError("Маршрут", routeId));

        var fieldsError = ValidateFields(r.ExecutorEmail, r.Position, r.ProjectRole, route.ByProject);
        if (fieldsError is not null)
            return Result.Fail<TemplateRouteStepDto>(fieldsError);

        var entity = new TemplateRouteStep
        {
            RouteId = route.Id,
            OrderNo = r.OrderNo,
            ExecutorEmail = r.ExecutorEmail,
            Position = r.Position,
            ProjectRole = r.ProjectRole,
            HeadType = r.HeadType,
            Status = r.Status,
            AllowReassignToOtherApprovers = r.AllowReassignToOtherApprovers
        };
        db.TemplateRouteSteps.Add(entity);
        await db.SaveChangesAsync(cancellationToken);

        var result = Result.Ok(ToDto(entity));
        return await AppendMissingProjectRoleWarningAsync(route, result, cancellationToken);
    }

    public async Task<Result<TemplateRouteStepDto>> UpdateAsync(
        Guid routeId, Guid id, UpdateTemplateRouteStepRequest r, CancellationToken cancellationToken)
    {
        var route = await db.TemplateRoutes.FirstOrDefaultAsync(x => x.Id == routeId, cancellationToken);
        if (route is null)
            return Result.Fail<TemplateRouteStepDto>(new NotFoundError("Маршрут", routeId));

        var entity = await db.TemplateRouteSteps.FirstOrDefaultAsync(x => x.Id == id && x.RouteId == routeId, cancellationToken);
        if (entity is null)
            return Result.Fail<TemplateRouteStepDto>(new NotFoundError("Шаг маршрута", id));

        var fieldsError = ValidateFields(r.ExecutorEmail, r.Position, r.ProjectRole, route.ByProject);
        if (fieldsError is not null)
            return Result.Fail<TemplateRouteStepDto>(fieldsError);

        entity.OrderNo = r.OrderNo;
        entity.ExecutorEmail = r.ExecutorEmail;
        entity.Position = r.Position;
        entity.ProjectRole = r.ProjectRole;
        entity.HeadType = r.HeadType;
        entity.Status = r.Status;
        entity.AllowReassignToOtherApprovers = r.AllowReassignToOtherApprovers;
        await db.SaveChangesAsync(cancellationToken);

        var result = Result.Ok(ToDto(entity));
        return await AppendMissingProjectRoleWarningAsync(route, result, cancellationToken);
    }

    public async Task<Result> DeleteAsync(Guid routeId, Guid id, CancellationToken cancellationToken)
    {
        var entity = await db.TemplateRouteSteps.FirstOrDefaultAsync(x => x.Id == id && x.RouteId == routeId, cancellationToken);
        if (entity is null)
            return Result.Fail(new NotFoundError("Шаг маршрута", id));

        db.TemplateRouteSteps.Remove(entity);
        await db.SaveChangesAsync(cancellationToken);

        return Result.Ok();
    }

    private static IError? ValidateFields(string executorEmail, string position, ProjectRole projectRole, bool routeByProject)
    {
        if (string.IsNullOrWhiteSpace(executorEmail) && string.IsNullOrWhiteSpace(position) && projectRole == ProjectRole.None)
            return new ValidationError("Исполнитель, должность и роль в проекте не могут быть пустыми одновременно.");

        if (!routeByProject && projectRole != ProjectRole.None)
            return new ValidationError("Роль в проекте недопустима для шага маршрута, который не учитывает проект (by_project = false).");

        return null;
    }

    private async Task<Result<TemplateRouteStepDto>> AppendMissingProjectRoleWarningAsync(
        TemplateRoute route, Result<TemplateRouteStepDto> result, CancellationToken cancellationToken)
    {
        if (!route.ByProject)
            return result;

        var hasProjectRoleStep = await db.TemplateRouteSteps
            .AnyAsync(x => x.RouteId == route.Id && x.ProjectRole != ProjectRole.None, cancellationToken);

        return hasProjectRoleStep
            ? result
            : result.WithReason(new Warning("Должен быть хотя бы один шаг с ролью в проекте."));
    }

    private static TemplateRouteStepDto ToDto(TemplateRouteStep e) => new(
        e.Id, e.OrderNo, e.ExecutorEmail, e.Position, e.ProjectRole, e.HeadType, e.Status, e.RouteId, e.AllowReassignToOtherApprovers);
}