using System.Text.Json;
using PlotLine.Data;
using PlotLine.Models;

namespace PlotLine.Services;

public interface ISceneImportResolver
{
    Task<StoryIntelligenceImportPreview> ResolveAsync(StoryIntelligenceSavedRun run, IReadOnlyList<StoryIntelligenceSavedSceneResult> sceneResults);
}

public sealed class SceneImportResolver(
    ICharacterRepository characters,
    ILocationRepository locations,
    IAssetRepository assets,
    ILogger<SceneImportResolver> logger) : ISceneImportResolver
{
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true
    };

    private static readonly HashSet<string> GenericPeople = CreateSet(
        "the receptionist", "receptionist", "old man", "young woman", "police officer", "doctor", "nurse", "driver",
        "man", "woman", "boy", "girl", "child", "person", "guard", "waiter", "waitress", "clerk", "shopkeeper");

    private static readonly HashSet<string> IgnoredPovNames = CreateSet("narrator", "unknown");

    private static readonly HashSet<string> GenericLocations = CreateSet(
        "car park", "road", "house", "kitchen", "stairwell", "stair", "doorway", "corridor", "street", "room",
        "bedroom", "bathroom", "office", "car", "church", "hall", "table", "chair");

    private static readonly HashSet<string> GenericAssets = CreateSet(
        "the key", "key", "the letter", "letter", "the car", "car", "phone", "table", "chair", "door", "window");

    public async Task<StoryIntelligenceImportPreview> ResolveAsync(StoryIntelligenceSavedRun run, IReadOnlyList<StoryIntelligenceSavedSceneResult> sceneResults)
    {
        if (run.ProjectID is not int projectId)
        {
            return new StoryIntelligenceImportPreview
            {
                Warnings = ["Import Preview requires a project id to resolve existing PlotDirector entities."]
            };
        }

        var scenes = sceneResults
            .Where(scene => scene.ValidationErrorsCount == 0)
            .Select(TryReadScene)
            .Where(scene => scene is not null)
            .Cast<SceneIntelligenceScene>()
            .ToList();

        var characterIndex = await BuildCharacterIndexAsync(projectId);
        var locationIndex = await BuildLocationIndexAsync(projectId);
        var assetIndex = await BuildAssetIndexAsync(projectId);
        var existingRelationships = await characters.ListRelationshipsByProjectAsync(projectId);

        var characterResolutions = ResolveCharacters(scenes, characterIndex).ToList();
        var locationResolutions = ResolveLocations(scenes, locationIndex).ToList();
        var assetResolutions = ResolveAssets(scenes, assetIndex).ToList();
        var relationshipPreview = ResolveRelationships(scenes, existingRelationships).ToList();
        var knowledgePreview = ResolveKnowledge(scenes).ToList();
        var timelinePreview = ResolveTimeline(scenes).ToList();
        var warnings = BuildWarnings(characterResolutions, locationResolutions, assetResolutions).ToList();

        return new StoryIntelligenceImportPreview
        {
            Characters = characterResolutions,
            Locations = locationResolutions,
            Assets = assetResolutions,
            Relationships = relationshipPreview,
            Knowledge = knowledgePreview,
            Timeline = timelinePreview,
            Warnings = warnings
        };
    }

    private IEnumerable<StoryImportEntityResolution> ResolveCharacters(IEnumerable<SceneIntelligenceScene> scenes, EntityIndex index)
    {
        foreach (var item in scenes
            .SelectMany(scene => (scene.Characters ?? []).Select(character => new CharacterMention(character.Name, character.Confidence, character.Notes)))
            .Concat(scenes.Select(scene => new CharacterMention(scene.PointOfView?.CharacterName, scene.PointOfView?.Confidence, "Point of view character.")))
            .Where(item => !string.IsNullOrWhiteSpace(item.Name))
            .GroupBy(item => Clean(item.Name), StringComparer.OrdinalIgnoreCase)
            .Select(group => group.First()))
        {
            var name = Clean(item.Name);
            if (IgnoredPovNames.Contains(name))
            {
                yield return LogResolution(new StoryImportEntityResolution
                {
                    InputName = name,
                    EntityType = "Character",
                    Status = StoryImportResolutionStatuses.Ignored,
                    Confidence = item.Confidence,
                    Notes = "Narrator identity is intentionally left for later chapter metadata resolution."
                });
                continue;
            }

            if (GenericPeople.Contains(name.ToLowerInvariant()))
            {
                yield return LogResolution(new StoryImportEntityResolution
                {
                    InputName = name,
                    EntityType = "Character",
                    Status = StoryImportResolutionStatuses.UnresolvedPersonReference,
                    Confidence = item.Confidence,
                    Notes = "Generic person reference; would not create a Character record."
                });
                continue;
            }

            yield return LogResolution(MatchEntity("Character", name, item.Confidence, index, StoryImportResolutionStatuses.NewCharacter));
        }
    }

    private IEnumerable<StoryImportEntityResolution> ResolveLocations(IEnumerable<SceneIntelligenceScene> scenes, EntityIndex index)
    {
        foreach (var item in scenes
            .SelectMany(scene => scene.Locations ?? [])
            .Where(location => !string.IsNullOrWhiteSpace(location.Name))
            .GroupBy(location => Clean(location.Name), StringComparer.OrdinalIgnoreCase)
            .Select(group => group.First()))
        {
            var name = Clean(item.Name);
            if (IsGenericLocation(item))
            {
                yield return LogResolution(new StoryImportEntityResolution
                {
                    InputName = name,
                    EntityType = "Location",
                    Status = StoryImportResolutionStatuses.GenericReference,
                    Confidence = item.Confidence,
                    Notes = "Generic location reference; would not create a Location record."
                });
                continue;
            }

            yield return LogResolution(MatchEntity("Location", name, item.Confidence, index, StoryImportResolutionStatuses.NewLocation));
        }
    }

    private IEnumerable<StoryImportEntityResolution> ResolveAssets(IEnumerable<SceneIntelligenceScene> scenes, EntityIndex index)
    {
        foreach (var item in scenes
            .SelectMany(scene => scene.Assets ?? [])
            .Where(asset => !string.IsNullOrWhiteSpace(asset.Name))
            .GroupBy(asset => Clean(asset.Name), StringComparer.OrdinalIgnoreCase)
            .Select(group => group.First()))
        {
            var name = Clean(item.Name);
            if (GenericAssets.Contains(name.ToLowerInvariant()))
            {
                yield return LogResolution(new StoryImportEntityResolution
                {
                    InputName = name,
                    EntityType = "Asset",
                    Status = StoryImportResolutionStatuses.GenericReference,
                    Confidence = item.Confidence,
                    Notes = "Generic object reference; would not create an Asset record unless later confirmed as meaningful."
                });
                continue;
            }

            yield return LogResolution(MatchEntity("Asset", name, item.Confidence, index, StoryImportResolutionStatuses.NewAsset));
        }
    }

    private static IEnumerable<StoryImportRelationshipPreview> ResolveRelationships(IEnumerable<SceneIntelligenceScene> scenes, IReadOnlyList<CharacterRelationship> existingRelationships)
    {
        foreach (var relationship in scenes.SelectMany(scene => scene.Relationships ?? []))
        {
            if (string.IsNullOrWhiteSpace(relationship.CharacterA) || string.IsNullOrWhiteSpace(relationship.CharacterB))
            {
                continue;
            }

            var exists = existingRelationships.Any(existing =>
                NamesMatch(existing.CharacterAName, relationship.CharacterA) && NamesMatch(existing.CharacterBName, relationship.CharacterB)
                || NamesMatch(existing.CharacterAName, relationship.CharacterB) && NamesMatch(existing.CharacterBName, relationship.CharacterA));

            yield return new StoryImportRelationshipPreview
            {
                Action = exists ? "Would Update Relationship" : "Would Create Relationship",
                CharacterA = relationship.CharacterA,
                CharacterB = relationship.CharacterB,
                Signal = relationship.RelationshipSignal ?? "relationship signal",
                Confidence = relationship.Confidence
            };
        }
    }

    private static IEnumerable<StoryImportKnowledgePreview> ResolveKnowledge(IEnumerable<SceneIntelligenceScene> scenes)
        => scenes.SelectMany(scene => scene.KnowledgeChanges ?? [])
            .Where(change => !string.IsNullOrWhiteSpace(change.RecipientCharacter) && !string.IsNullOrWhiteSpace(change.KnowledgeItem))
            .Select(change => new StoryImportKnowledgePreview
            {
                Character = change.RecipientCharacter!,
                KnowledgeItem = change.KnowledgeItem!,
                OldState = "Unknown",
                NewState = string.IsNullOrWhiteSpace(change.ChangeType) ? "Would update" : change.ChangeType!,
                Confidence = change.Confidence
            });

    private static IEnumerable<StoryImportTimelinePreview> ResolveTimeline(IEnumerable<SceneIntelligenceScene> scenes)
        => scenes.SelectMany(scene => (scene.TimelineClues ?? []).Select(clue => new StoryImportTimelinePreview
        {
            SceneNumber = scene.SceneReference?.SceneNumber.HasValue == true ? Convert.ToInt32(scene.SceneReference.SceneNumber.Value) : null,
            SceneDate = !string.IsNullOrWhiteSpace(clue.AbsoluteDate) ? clue.AbsoluteDate! : clue.Clue ?? "Timeline clue",
            Confidence = clue.Confidence
        }));

    private StoryImportEntityResolution MatchEntity(string entityType, string inputName, decimal? confidence, EntityIndex index, string newStatus)
    {
        var candidates = index.Find(inputName);
        return candidates.Count switch
        {
            0 => new StoryImportEntityResolution { InputName = inputName, EntityType = entityType, Status = newStatus, Confidence = confidence },
            1 => new StoryImportEntityResolution
            {
                InputName = inputName,
                EntityType = entityType,
                Status = StoryImportResolutionStatuses.Matched,
                MatchedID = candidates[0].EntityID,
                MatchedName = candidates[0].Name,
                Confidence = confidence,
                Candidates = candidates
            },
            _ => new StoryImportEntityResolution
            {
                InputName = inputName,
                EntityType = entityType,
                Status = StoryImportResolutionStatuses.Ambiguous,
                Confidence = confidence,
                Candidates = candidates
            }
        };
    }

    private async Task<EntityIndex> BuildCharacterIndexAsync(int projectId)
    {
        var rows = new List<EntityIndexRow>();
        foreach (var character in await characters.ListCharactersAsync(projectId))
        {
            rows.Add(new EntityIndexRow(character.CharacterID, character.CharacterName, character.CharacterName, "Name"));
            if (!string.IsNullOrWhiteSpace(character.ShortName))
            {
                rows.Add(new EntityIndexRow(character.CharacterID, character.CharacterName, character.ShortName!, "Display name"));
            }

            foreach (var alias in await characters.ListAliasesAsync(character.CharacterID))
            {
                rows.Add(new EntityIndexRow(character.CharacterID, character.CharacterName, alias.Alias, "Alias"));
            }
        }

        return new EntityIndex(rows);
    }

    private async Task<EntityIndex> BuildLocationIndexAsync(int projectId)
    {
        var rows = new List<EntityIndexRow>();
        foreach (var location in await locations.ListByProjectAsync(projectId))
        {
            rows.Add(new EntityIndexRow(location.LocationID, location.LocationName, location.LocationName, "Name"));
            foreach (var alias in await locations.ListAliasesAsync(location.LocationID))
            {
                rows.Add(new EntityIndexRow(location.LocationID, location.LocationName, alias.Alias, "Alias"));
            }
        }

        return new EntityIndex(rows);
    }

    private async Task<EntityIndex> BuildAssetIndexAsync(int projectId)
    {
        var rows = new List<EntityIndexRow>();
        foreach (var asset in await assets.ListAssetsAsync(projectId))
        {
            rows.Add(new EntityIndexRow(asset.StoryAssetID, asset.AssetName, asset.AssetName, "Name"));
            foreach (var alias in await assets.ListAliasesAsync(asset.StoryAssetID))
            {
                rows.Add(new EntityIndexRow(asset.StoryAssetID, asset.AssetName, alias.Alias, "Alias"));
            }
        }

        return new EntityIndex(rows);
    }

    private StoryImportEntityResolution LogResolution(StoryImportEntityResolution resolution)
    {
        logger.LogInformation(
            "Story Intelligence Import Preview resolved {EntityType}. Input={InputName} Status={Status} Resolved={ResolvedName} Confidence={ConfidencePercent} Candidates={Candidates}",
            resolution.EntityType,
            resolution.InputName,
            resolution.Status,
            resolution.MatchedName,
            resolution.ConfidencePercent,
            string.Join(", ", resolution.Candidates.Select(candidate => candidate.Name)));
        return resolution;
    }

    private static IEnumerable<string> BuildWarnings(
        IReadOnlyList<StoryImportEntityResolution> characterResolutions,
        IReadOnlyList<StoryImportEntityResolution> locationResolutions,
        IReadOnlyList<StoryImportEntityResolution> assetResolutions)
    {
        var unresolved = characterResolutions.Concat(locationResolutions).Concat(assetResolutions)
            .Count(item => item.Status is StoryImportResolutionStatuses.Ambiguous or StoryImportResolutionStatuses.UnresolvedPersonReference);
        yield return unresolved == 0 ? "No unresolved entities." : $"{unresolved:N0} unresolved or ambiguous reference(s).";
    }

    private static SceneIntelligenceScene? TryReadScene(StoryIntelligenceSavedSceneResult result)
    {
        if (string.IsNullOrWhiteSpace(result.ParsedJson))
        {
            return null;
        }

        try
        {
            var direct = JsonSerializer.Deserialize<SceneIntelligenceScene>(result.ParsedJson, JsonOptions);
            if (!string.IsNullOrWhiteSpace(direct?.SchemaVersion))
            {
                return direct;
            }

            using var document = JsonDocument.Parse(result.ParsedJson);
            if (document.RootElement.TryGetProperty("parsedScene", out var parsedScene))
            {
                return parsedScene.Deserialize<SceneIntelligenceScene>(JsonOptions);
            }
        }
        catch (JsonException)
        {
        }

        return null;
    }

    private static bool IsGenericLocation(SceneIntelligenceLocation location)
        => string.Equals(location.LocationType, "generic", StringComparison.OrdinalIgnoreCase)
            || GenericLocations.Contains(Clean(location.Name).ToLowerInvariant());

    private static string Clean(string? value)
        => string.Join(' ', (value ?? string.Empty).Trim().Split((char[]?)null, StringSplitOptions.RemoveEmptyEntries));

    private static bool NamesMatch(string? first, string? second)
        => string.Equals(Clean(first), Clean(second), StringComparison.OrdinalIgnoreCase);

    private static HashSet<string> CreateSet(params string[] values)
        => new(values, StringComparer.OrdinalIgnoreCase);

    private sealed record EntityIndexRow(int EntityID, string EntityName, string MatchValue, string MatchReason);

    private sealed record CharacterMention(string? Name, decimal? Confidence, string? Notes);

    private sealed class EntityIndex(IReadOnlyList<EntityIndexRow> rows)
    {
        public IReadOnlyList<StoryImportResolutionCandidate> Find(string value)
        {
            var clean = Clean(value);
            var matches = rows
                .Where(row => string.Equals(Clean(row.MatchValue), clean, StringComparison.Ordinal)
                    || string.Equals(Clean(row.MatchValue), clean, StringComparison.OrdinalIgnoreCase))
                .GroupBy(row => row.EntityID)
                .Select(group =>
                {
                    var first = group.First();
                    return new StoryImportResolutionCandidate
                    {
                        EntityID = first.EntityID,
                        Name = first.EntityName,
                        MatchReason = first.MatchReason
                    };
                })
                .ToList();

            return matches;
        }
    }
}