using System.Collections.Generic;
using System.Linq;
using Questionable.Model;
using Questionable.Model.Questing;

namespace Questionable.Validation.Validators;

internal sealed class UniqueStartStopValidator : IQuestValidator
{
	public IEnumerable<ValidationIssue> Validate(Quest quest)
	{
		bool skipMissingStartStop = !(quest.Id is QuestId);
		List<(QuestSequence Sequence, int StepId, QuestStep Step)> questAccepts = (from x in FindQuestStepsWithInteractionType(quest, new List<EInteractionType> { EInteractionType.AcceptQuest })
			where x.Step.PickUpQuestId == null
			select x).ToList();
		foreach (var item in questAccepts)
		{
			if (item.Sequence.Sequence != 0 || item.StepId != quest.FindSequence(0).Steps.Count - 1)
			{
				yield return new ValidationIssue
				{
					PathType = EPathType.Quest,
					Id = quest.Id.ToString(),
					Location = SchemaValidationHelper.FormatQuestLocation(item.Sequence.Sequence, item.StepId),
					Type = EIssueType.UnexpectedAcceptQuestStep,
					Severity = EIssueSeverity.Error,
					Description = "Unexpected AcceptQuest step"
				};
			}
		}
		if (!skipMissingStartStop && quest.FindSequence(0) != null && questAccepts.Count == 0)
		{
			yield return new ValidationIssue
			{
				PathType = EPathType.Quest,
				Id = quest.Id.ToString(),
				Location = SchemaValidationHelper.FormatQuestLocation(0, null),
				Type = EIssueType.MissingQuestAccept,
				Severity = EIssueSeverity.Error,
				Description = "No AcceptQuest step"
			};
		}
		List<(QuestSequence Sequence, int StepId, QuestStep Step)> questCompletes = (from x in FindQuestStepsWithInteractionType(quest, new List<EInteractionType> { EInteractionType.CompleteQuest })
			where x.Step.TurnInQuestId == null
			select x).ToList();
		foreach (var item2 in questCompletes)
		{
			if (item2.Sequence.Sequence != byte.MaxValue || item2.StepId != quest.FindSequence(byte.MaxValue).Steps.Count - 1)
			{
				yield return new ValidationIssue
				{
					PathType = EPathType.Quest,
					Id = quest.Id.ToString(),
					Location = SchemaValidationHelper.FormatQuestLocation(item2.Sequence.Sequence, item2.StepId),
					Type = EIssueType.UnexpectedCompleteQuestStep,
					Severity = EIssueSeverity.Error,
					Description = "Unexpected CompleteQuest step"
				};
			}
		}
		if (!skipMissingStartStop && quest.FindSequence(byte.MaxValue) != null && questCompletes.Count == 0)
		{
			yield return new ValidationIssue
			{
				PathType = EPathType.Quest,
				Id = quest.Id.ToString(),
				Location = SchemaValidationHelper.FormatQuestLocation((byte)byte.MaxValue, null),
				Type = EIssueType.MissingQuestComplete,
				Severity = EIssueSeverity.Error,
				Description = "No CompleteQuest step"
			};
		}
	}

	private static IEnumerable<(QuestSequence Sequence, int StepId, QuestStep Step)> FindQuestStepsWithInteractionType(Quest quest, List<EInteractionType> interactionType)
	{
		return from x in quest.AllSteps()
			where interactionType.Contains(x.Step.InteractionType)
			select x;
	}
}