PlotDirector/PlotLine/Services/ManuscriptStructureAnalysisService.cs

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

namespace PlotLine.Services;

public interface IManuscriptStructureAnalysisService
{
    Task<ManuscriptStructureAnalysisResult> AnalyseChapterAsync(ManuscriptStructureAnalysisRequest request, CancellationToken cancellationToken = default);
}

public sealed class ManuscriptStructureAnalysisService(
    IStoryPromptRepository prompts,
    IStoryPromptVersionService versions,
    IStoryIntelligenceClient client,
    IChapterStructureValidator validator,
    ILogger<ManuscriptStructureAnalysisService> logger) : IManuscriptStructureAnalysisService
{
    private const string ChapterPromptFile = "Chapter-Structure-Prompt-V2.md";
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true,
        WriteIndented = true
    };

    public async Task<ManuscriptStructureAnalysisResult> AnalyseChapterAsync(ManuscriptStructureAnalysisRequest request, CancellationToken cancellationToken = default)
    {
        var text = request.ChapterText?.Trim() ?? string.Empty;
        var paragraphs = StoryIntelligenceParagraphs.Split(text);
        if (paragraphs.Count == 0)
        {
            return ManuscriptStructureAnalysisResult.Failed(
                request.TemporaryChapterKey,
                "The approved chapter has no readable text for scene-boundary detection.");
        }

        try
        {
            var promptVersion = versions.GetPromptVersion(ChapterPromptFile);
            var clientStatus = client.GetConfigurationStatus();
            var template = await prompts.LoadPromptAsync(ChapterPromptFile, cancellationToken);
            var prompt = BuildChapterPrompt(template, BuildChapterContextJson(request), StoryIntelligenceParagraphs.Number(paragraphs));
            var result = await client.ExecutePromptAsync(prompt, promptVersion, cancellationToken, clientStatus.ChapterStructureModel);
            var chapterJson = ExtractOutputText(result.RawResponseText);
            var parsed = JsonSerializer.Deserialize<ChapterStructureModel>(chapterJson, JsonOptions);
            var normalisation = ChapterStructureBoundaryNormaliser.Normalise(parsed, paragraphs.Count);
            var chapter = normalisation.ChapterStructure;
            var validation = validator.Validate(chapter, paragraphs.Count);
            ChapterStructureBoundaryNormaliser.AddIssuesTo(validation, normalisation);

            if (!validation.IsValid || chapter?.SceneBoundaries is null || chapter.SceneBoundaries.Count == 0)
            {
                return ManuscriptStructureAnalysisResult.Failed(
                    request.TemporaryChapterKey,
                    BuildValidationMessage(validation),
                    chapterJson);
            }

            var scenes = new List<ManuscriptStructureSceneBoundary>();
            foreach (var boundary in chapter.SceneBoundaries.OrderBy(item => item.SceneNumber ?? int.MaxValue))
            {
                var sceneNumber = boundary.SceneNumber ?? 0;
                var start = boundary.StartParagraph ?? 0;
                var end = boundary.EndParagraph ?? 0;
                if (sceneNumber <= 0 || start <= 0 || end <= 0 || start > end || end > paragraphs.Count)
                {
                    return ManuscriptStructureAnalysisResult.Failed(
                        request.TemporaryChapterKey,
                        $"Scene {sceneNumber:N0} has an invalid paragraph range.",
                        chapterJson);
                }

                var startMap = request.ParagraphMap.FirstOrDefault(item => item.StructuralParagraphOrdinal == start);
                if (startMap is null || startMap.WordParagraphIndex < 0)
                {
                    return ManuscriptStructureAnalysisResult.Failed(
                        request.TemporaryChapterKey,
                        $"Scene {sceneNumber:N0} could not be mapped back to a Word paragraph.",
                        chapterJson);
                }

                var sceneParagraphs = paragraphs.Skip(start - 1).Take(end - start + 1).ToList();
                scenes.Add(new ManuscriptStructureSceneBoundary
                {
                    TemporarySceneKey = $"{request.TemporaryChapterKey}-ai-scene-{sceneNumber}",
                    TemporaryChapterKey = request.TemporaryChapterKey,
                    SceneNumberWithinChapter = sceneNumber,
                    Title = $"Scene {sceneNumber:N0}",
                    WordCount = sceneParagraphs.Sum(CountWords),
                    StartParagraph = start,
                    EndParagraph = end,
                    WordStartPosition = startMap.WordParagraphIndex,
                    Reason = boundary.Reason,
                    Confidence = boundary.Confidence
                });
            }

            logger.LogInformation(
                "Structural scene-boundary analysis completed. ProjectID={ProjectID} BookID={BookID} TemporaryChapterKey={TemporaryChapterKey} Scenes={SceneCount}",
                request.ProjectID,
                request.BookID,
                request.TemporaryChapterKey,
                scenes.Count);

            return ManuscriptStructureAnalysisResult.Succeeded(request.TemporaryChapterKey, scenes, chapterJson);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            logger.LogWarning(
                ex,
                "Structural scene-boundary analysis failed. ProjectID={ProjectID} BookID={BookID} TemporaryChapterKey={TemporaryChapterKey}",
                request.ProjectID,
                request.BookID,
                request.TemporaryChapterKey);
            return ManuscriptStructureAnalysisResult.Failed(request.TemporaryChapterKey, ex.Message);
        }
    }

    private static string BuildChapterContextJson(ManuscriptStructureAnalysisRequest request)
        => JsonSerializer.Serialize(new
        {
            projectId = request.ProjectID,
            bookId = request.BookID,
            chapterId = (int?)null,
            chapterNumber = request.ChapterNumber,
            sourceLabel = request.SourceLabel
        }, JsonOptions);

    private static string BuildChapterPrompt(string promptTemplate, string chapterContextJson, string chapterText)
    {
        if (string.IsNullOrWhiteSpace(promptTemplate))
        {
            throw new InvalidOperationException("Prompt template is empty.");
        }

        return promptTemplate
            .Replace("{{CHAPTER_CONTEXT_JSON}}", chapterContextJson ?? string.Empty, StringComparison.Ordinal)
            .Replace("{{CHAPTER_TEXT}}", chapterText ?? string.Empty, StringComparison.Ordinal);
    }

    private static string ExtractOutputText(string rawResponseText)
    {
        var response = JsonSerializer.Deserialize<OpenAIResponseEnvelope>(rawResponseText, JsonOptions)
            ?? throw new JsonException("OpenAI response envelope was empty.");
        var outputText = response.Output?
            .SelectMany(item => item.Content ?? [])
            .FirstOrDefault(content => string.Equals(content.Type, "output_text", StringComparison.OrdinalIgnoreCase)
                && !string.IsNullOrWhiteSpace(content.Text))
            ?.Text;

        if (string.IsNullOrWhiteSpace(outputText))
        {
            throw new JsonException("OpenAI response did not contain output_text content.");
        }

        return outputText.Trim();
    }

    private static string BuildValidationMessage(ValidationResult validation)
    {
        var first = validation.Errors.FirstOrDefault()?.Message
            ?? validation.Warnings.FirstOrDefault()?.Message
            ?? "Chapter Structure validation failed.";
        return first;
    }

    private static int CountWords(string value)
        => string.IsNullOrWhiteSpace(value)
            ? 0
            : value.Split((char[]?)null, StringSplitOptions.RemoveEmptyEntries).Length;
}

public sealed class ManuscriptStructureAnalysisRequest
{
    public int ProjectID { get; init; }
    public int BookID { get; init; }
    public string TemporaryChapterKey { get; init; } = string.Empty;
    public int ChapterNumber { get; init; }
    public string SourceLabel { get; init; } = string.Empty;
    public string ChapterText { get; init; } = string.Empty;
    public IReadOnlyList<ManuscriptScanParagraphMap> ParagraphMap { get; init; } = [];
}

public sealed class ManuscriptStructureAnalysisResult
{
    public string TemporaryChapterKey { get; init; } = string.Empty;
    public bool Success { get; init; }
    public string? ErrorMessage { get; init; }
    public string? ParsedJson { get; init; }
    public IReadOnlyList<ManuscriptStructureSceneBoundary> Scenes { get; init; } = [];

    public static ManuscriptStructureAnalysisResult Succeeded(string temporaryChapterKey, IReadOnlyList<ManuscriptStructureSceneBoundary> scenes, string? parsedJson)
        => new() { TemporaryChapterKey = temporaryChapterKey, Success = true, Scenes = scenes, ParsedJson = parsedJson };

    public static ManuscriptStructureAnalysisResult Failed(string temporaryChapterKey, string errorMessage, string? parsedJson = null)
        => new() { TemporaryChapterKey = temporaryChapterKey, Success = false, ErrorMessage = errorMessage, ParsedJson = parsedJson };
}

public sealed class ManuscriptStructureSceneBoundary
{
    public string TemporarySceneKey { get; init; } = string.Empty;
    public string TemporaryChapterKey { get; init; } = string.Empty;
    public int SceneNumberWithinChapter { get; init; }
    public string Title { get; init; } = string.Empty;
    public int WordCount { get; init; }
    public int StartParagraph { get; init; }
    public int EndParagraph { get; init; }
    public int WordStartPosition { get; init; }
    public string? Reason { get; init; }
    public decimal? Confidence { get; init; }
}