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

namespace Questionable.Validation.Validators;

internal sealed class BasicSequenceValidator : IQuestValidator
{
	public IEnumerable<ValidationIssue> Validate(Quest quest)
	{
		List<QuestSequence> sequences = quest.Root.QuestSequence;
		QuestSequence foundStart = sequences.FirstOrDefault((QuestSequence x) => x.Sequence == 0);
		if (foundStart == null)
		{
			yield return new ValidationIssue
			{
				ElementId = quest.Id,
				Sequence = 0,
				Step = null,
				Type = EIssueType.MissingSequence0,
				Severity = EIssueSeverity.Error,
				Description = "Missing quest start"
			};
		}
		else if (quest.Info is QuestInfo { CompletesInstantly: not false })
		{
			foreach (QuestSequence item in sequences)
			{
				if (item != foundStart)
				{
					yield return new ValidationIssue
					{
						ElementId = quest.Id,
						Sequence = item.Sequence,
						Step = null,
						Type = EIssueType.InstantQuestWithMultipleSteps,
						Severity = EIssueSeverity.Error,
						Description = "Instant quest should not have any sequences after the start"
					};
				}
			}
		}
		else
		{
			if (!(quest.Info is QuestInfo))
			{
				yield break;
			}
			int maxSequence = (from x in sequences
				select x.Sequence into x
				where x != byte.MaxValue
				select x).Max();
			int i;
			for (i = 0; i < maxSequence; i++)
			{
				List<QuestSequence> foundSequences = sequences.Where((QuestSequence x) => x.Sequence == i).ToList();
				ValidationIssue validationIssue = ValidateSequences(quest, i, foundSequences);
				if (validationIssue != null)
				{
					yield return validationIssue;
				}
			}
			List<QuestSequence> foundSequences2 = sequences.Where((QuestSequence x) => x.Sequence == byte.MaxValue).ToList();
			ValidationIssue validationIssue2 = ValidateSequences(quest, 255, foundSequences2);
			if (validationIssue2 != null)
			{
				yield return validationIssue2;
			}
		}
	}

	private static ValidationIssue? ValidateSequences(Quest quest, int sequenceNo, List<QuestSequence> foundSequences)
	{
		if (foundSequences.Count == 0)
		{
			return new ValidationIssue
			{
				ElementId = quest.Id,
				Sequence = (byte)sequenceNo,
				Step = null,
				Type = EIssueType.MissingSequence,
				Severity = EIssueSeverity.Error,
				Description = "Missing sequence"
			};
		}
		if (foundSequences.Count == 2)
		{
			return new ValidationIssue
			{
				ElementId = quest.Id,
				Sequence = (byte)sequenceNo,
				Step = null,
				Type = EIssueType.DuplicateSequence,
				Severity = EIssueSeverity.Error,
				Description = "Duplicate sequence"
			};
		}
		return null;
	}
}