using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Framework.Validation;

namespace GB5Shared.ValidationCriteria
{
    public class ValidationCriteriaEvaluator : IValidationCriteriaEvaluator
    {
        private const byte VALIDATIONTYPE_SKILL = 1;
        private const byte VALIDATIONTYPE_QUIZ = 2;
        private const byte VALIDATIONTYPE_PROGRAMME_ASSESSMENT = 3;
        private const byte VALIDATIONTYPE_CERTIFICATION = 4;

        private readonly IValidationAssignmentDAL _ValidationAssignmentDAL;

        public ValidationCriteriaEvaluator(IValidationAssignmentDAL validationAssignmentDAL)
        {
            _ValidationAssignmentDAL = validationAssignmentDAL;
        }

        public async Task<List<ValidationCriteriaResultDTO>> GetUnmetValidationCriteriaAsync(
            short entityType, int entityId, int entityStepId, int employeeId, LoginDTO login, CancellationToken ct)
        {
            var assignments = await _ValidationAssignmentDAL.GetAssignmentsWithCriteriaForEntity(entityType, entityId, entityStepId, login)
                .ConfigureAwait(false);

            var unmet = new List<ValidationCriteriaResultDTO>();

            foreach (var a in assignments)
            {
                var status = await EvaluateOneAsync(a, employeeId, login).ConfigureAwait(false);
                if (status == ValidationCriteriaStatus.Met) continue;

                unmet.Add(new ValidationCriteriaResultDTO
                {
                    ValidationAssignmentId = a.ValidationAssignmentId,
                    ValidationCriteriaId = a.ValidationCriteriaId,
                    ValidationType = a.ValidationType,
                    Description = a.Description,
                    Enforcement = a.Enforcement,
                    IsMandatory = a.IsMandatory,
                    Status = status
                });
            }

            return unmet;
        }

        private async Task<ValidationCriteriaStatus> EvaluateOneAsync(
            ValidationAssignmentWithCriteriaDTO a, int employeeId, LoginDTO login)
        {
            switch (a.ValidationType)
            {
                case VALIDATIONTYPE_SKILL:
                    {
                        var level = await _ValidationAssignmentDAL.GetEmployeeSkillLevel(employeeId, a.TargetId, login).ConfigureAwait(false);
                        return (level.HasValue && level.Value >= a.MinLevel) ? ValidationCriteriaStatus.Met : ValidationCriteriaStatus.NotMet;
                    }

                case VALIDATIONTYPE_QUIZ:
                    {
                        var completedOn = await _ValidationAssignmentDAL.GetLatestPassingQuizAttemptCompletedOn(a.TargetId, employeeId, login).ConfigureAwait(false);
                        return IsWithinValidity(completedOn, a.ValidityDays) ? ValidationCriteriaStatus.Met : ValidationCriteriaStatus.NotMet;
                    }

                case VALIDATIONTYPE_PROGRAMME_ASSESSMENT:
                    {
                        var completedOn = await _ValidationAssignmentDAL.GetLatestPassingAssessmentAttemptCompletedOn(a.TargetId, employeeId, login).ConfigureAwait(false);
                        return IsWithinValidity(completedOn, a.ValidityDays) ? ValidationCriteriaStatus.Met : ValidationCriteriaStatus.NotMet;
                    }

                case VALIDATIONTYPE_CERTIFICATION:
                default:
                    // No universal certification/data-record table exists in this repo today — not
                    // implemented generically. Report Unverifiable rather than silently claiming Met.
                    return ValidationCriteriaStatus.Unverifiable;
            }
        }

        private static bool IsWithinValidity(DateTime? completedOn, int validityDays)
        {
            if (!completedOn.HasValue) return false;
            if (validityDays < 0) return true; // -1 = never expires
            return completedOn.Value >= DateTime.UtcNow.AddDays(-validityDays);
        }
    }
}