/**
 * File History Utilities
 *
 * Helper functions for integrating PDF metadata service with FileContext operations.
 * Handles extraction of history from files and preparation for metadata injection.
 */

import { pdfMetadataService, type ToolOperation } from '../services/pdfMetadataService';
import { StirlingFileStub } from '../types/fileContext';
import { FileId, FileMetadata } from '../types/file';
import { createFileId } from '../types/fileContext';

const DEBUG = process.env.NODE_ENV === 'development';

/**
 * Extract history information from a PDF file and update StirlingFileStub
 */
export async function extractFileHistory(
  file: File,
  record: StirlingFileStub
): Promise<StirlingFileStub> {
  // Only process PDF files
  if (!file.type.includes('pdf')) {
    return record;
  }

  try {
    const arrayBuffer = await file.arrayBuffer();
    const historyMetadata = await pdfMetadataService.extractHistoryMetadata(arrayBuffer);

    if (historyMetadata) {
      const history = historyMetadata.stirlingHistory;

      // Update record with history information
      return {
        ...record,
        originalFileId: history.originalFileId,
        versionNumber: history.versionNumber,
        parentFileId: history.parentFileId as FileId | undefined,
        toolHistory: history.toolChain
      };
    }
  } catch (error) {
    if (DEBUG) console.warn('📄 Failed to extract file history:', file.name, error);
  }

  return record;
}

/**
 * Inject history metadata into a PDF file for tool operations
 */
export async function injectHistoryForTool(
  file: File,
  sourceStirlingFileStub: StirlingFileStub,
  toolName: string,
  parameters?: Record<string, any>
): Promise<File> {
  // Only process PDF files
  if (!file.type.includes('pdf')) {
    return file;
  }

  try {
    const arrayBuffer = await file.arrayBuffer();

    // Create tool operation record
    const toolOperation: ToolOperation = {
      toolName,
      timestamp: Date.now(),
      parameters
    };

    let modifiedBytes: ArrayBuffer;

    // Extract version info directly from the PDF metadata to ensure accuracy
    const existingHistoryMetadata = await pdfMetadataService.extractHistoryMetadata(arrayBuffer);

    let newVersionNumber: number;
    let originalFileId: string;
    let parentFileId: string;
    let parentToolChain: ToolOperation[];

    if (existingHistoryMetadata) {
      // File already has embedded history - increment version
      const history = existingHistoryMetadata.stirlingHistory;
      newVersionNumber = history.versionNumber + 1;
      originalFileId = history.originalFileId;
      parentFileId = sourceStirlingFileStub.id; // This file becomes the parent
      parentToolChain = history.toolChain || [];

    } else if (sourceStirlingFileStub.originalFileId && sourceStirlingFileStub.versionNumber) {
      // File record has history but PDF doesn't (shouldn't happen, but fallback)
      newVersionNumber = sourceStirlingFileStub.versionNumber + 1;
      originalFileId = sourceStirlingFileStub.originalFileId;
      parentFileId = sourceStirlingFileStub.id;
      parentToolChain = sourceStirlingFileStub.toolHistory || [];
    } else {
      // File has no history - this becomes version 1
      newVersionNumber = 1;
      originalFileId = sourceStirlingFileStub.id; // Use source file ID as original
      parentFileId = sourceStirlingFileStub.id; // Parent is the source file
      parentToolChain = []; // No previous tools
    }

    // Create new tool chain with the new operation
    const newToolChain = [...parentToolChain, toolOperation];

    modifiedBytes = await pdfMetadataService.injectHistoryMetadata(
      arrayBuffer,
      originalFileId,
      parentFileId,
      newToolChain,
      newVersionNumber
    );

    // Create new file with updated metadata
    return new File([modifiedBytes], file.name, { type: file.type });
  } catch (error) {
    if (DEBUG) console.warn('📄 Failed to inject history for tool operation:', error);
    return file; // Return original file if injection fails
  }
}

/**
 * Prepare StirlingFiles with history-injected PDFs for tool operations
 * Preserves fileId and all StirlingFile metadata while injecting history
 */
export async function prepareStirlingFilesWithHistory(
  stirlingFiles: import('../types/fileContext').StirlingFile[],
  getStirlingFileStub: (fileId: import('../types/file').FileId) => StirlingFileStub | undefined,
  toolName: string,
  parameters?: Record<string, any>
): Promise<import('../types/fileContext').StirlingFile[]> {
  const processedFiles: import('../types/fileContext').StirlingFile[] = [];

  for (const stirlingFile of stirlingFiles) {
    const fileStub = getStirlingFileStub(stirlingFile.fileId);

    if (!fileStub) {
      // If no stub found, keep original file
      processedFiles.push(stirlingFile);
      continue;
    }

    // Inject history into the file data
    const fileWithHistory = await injectHistoryForTool(stirlingFile, fileStub, toolName, parameters);

    // Create new StirlingFile with the updated file data but preserve fileId and quickKey
    const updatedStirlingFile = new File([fileWithHistory], fileWithHistory.name, {
      type: fileWithHistory.type,
      lastModified: fileWithHistory.lastModified
    }) as import('../types/fileContext').StirlingFile;

    // Preserve the original fileId and quickKey
    Object.defineProperty(updatedStirlingFile, 'fileId', {
      value: stirlingFile.fileId,
      writable: false,
      enumerable: true,
      configurable: false
    });

    Object.defineProperty(updatedStirlingFile, 'quickKey', {
      value: stirlingFile.quickKey,
      writable: false,
      enumerable: true,
      configurable: false
    });

    processedFiles.push(updatedStirlingFile);
  }

  return processedFiles;
}

/**
 * Verify that processed files preserved metadata from originals
 * Logs warnings for tools that strip standard PDF metadata
 */
export async function verifyToolMetadataPreservation(
  originalFiles: File[],
  processedFiles: File[],
  toolName: string
): Promise<void> {
  if (originalFiles.length === 0 || processedFiles.length === 0) return;

  try {
    // For single-file tools, compare the original with the processed file
    if (originalFiles.length === 1 && processedFiles.length === 1) {
      const originalBytes = await originalFiles[0].arrayBuffer();
      const processedBytes = await processedFiles[0].arrayBuffer();

      await pdfMetadataService.verifyMetadataPreservation(
        originalBytes,
        processedBytes,
        toolName
      );
    }
    // For multi-file tools, we could add more complex verification later
  } catch (error) {
    if (DEBUG) console.warn(`📄 Failed to verify metadata preservation for ${toolName}:`, error);
  }
}

/**
 * Group files by processing branches - each branch ends in a leaf file
 * Returns Map<fileId, lineagePath[]> where fileId is the leaf and lineagePath is the path back to original
 */
export function groupFilesByOriginal(StirlingFileStubs: StirlingFileStub[]): Map<string, StirlingFileStub[]> {
  const groups = new Map<string, StirlingFileStub[]>();

  // Create a map for quick lookups
  const fileMap = new Map<string, StirlingFileStub>();
  for (const record of StirlingFileStubs) {
    fileMap.set(record.id, record);
  }

  // Find leaf files (files that are not parents of any other files AND have version history)
  // Original files (v0) should only be leaves if they have no processed versions at all
  const leafFiles = StirlingFileStubs.filter(stub => {
    const isParentOfOthers = StirlingFileStubs.some(otherStub => otherStub.parentFileId === stub.id);
    const isOriginalOfOthers = StirlingFileStubs.some(otherStub => otherStub.originalFileId === stub.id);

    // A file is a leaf if:
    // 1. It's not a parent of any other files, AND
    // 2. It has processing history (versionNumber > 0) OR it's not referenced as original by others
    return !isParentOfOthers && (stub.versionNumber && stub.versionNumber > 0 || !isOriginalOfOthers);
  });

  // For each leaf file, build its complete lineage path back to original
  for (const leafFile of leafFiles) {
    const lineagePath: StirlingFileStub[] = [];
    let currentFile: StirlingFileStub | undefined = leafFile;

    // Trace back through parentFileId chain to build this specific branch
    while (currentFile) {
      lineagePath.push(currentFile);

      // Move to parent file in this branch
      let nextFile: StirlingFileStub | undefined = undefined;

      if (currentFile.parentFileId) {
        nextFile = fileMap.get(currentFile.parentFileId);
      } else if (currentFile.originalFileId && currentFile.originalFileId !== currentFile.id) {
        // For v1 files, the original file might be referenced by originalFileId
        nextFile = fileMap.get(currentFile.originalFileId);
      }

      // Check for infinite loops before moving to next
      if (nextFile && lineagePath.some(file => file.id === nextFile!.id)) {
        break;
      }

      currentFile = nextFile;
    }

    // Sort lineage with latest version first (leaf at top)
    lineagePath.sort((a, b) => (b.versionNumber || 0) - (a.versionNumber || 0));

    // Use leaf file ID as the group key - each branch gets its own group
    groups.set(leafFile.id, lineagePath);
  }

  return groups;
}

/**
 * Get the latest version of each file group (optimized version using leaf flags)
 */
export function getLatestVersions(fileStubs: StirlingFileStub[]): StirlingFileStub[] {
  // If we have leaf flags, use them for much faster filtering
  const hasLeafFlags = fileStubs.some(fileStub => fileStub.isLeaf !== undefined);

  if (hasLeafFlags) {
    // Fast path: just return files marked as leaf nodes
    return fileStubs.filter(fileStub => fileStub.isLeaf !== false); // Default to true if undefined
  } else {
    // Fallback to expensive calculation for backward compatibility
    const groups = groupFilesByOriginal(fileStubs);
    const latestVersions: StirlingFileStub[] = [];

    for (const [_, fileStubs] of groups) {
      if (fileStubs.length > 0) {
        // First item is the latest version (sorted desc by version number)
        latestVersions.push(fileStubs[0]);
      }
    }

    return latestVersions;
  }
}

/**
 * Get version history for a file
 */
export function getVersionHistory(
  targetFileStub: StirlingFileStub,
  allFileStubs: StirlingFileStub[]
): StirlingFileStub[] {
  const originalId = targetFileStub.originalFileId || targetFileStub.id;

  return allFileStubs
    .filter(fileStub => {
      const fileStubOriginalId = fileStub.originalFileId || fileStub.id;
      return fileStubOriginalId === originalId;
    })
    .sort((a, b) => (b.versionNumber || 0) - (a.versionNumber || 0));
}

/**
 * Check if a file has version history
 */
export function hasVersionHistory(fileStub: StirlingFileStub): boolean {
  return !!(fileStub.originalFileId && fileStub.versionNumber && fileStub.versionNumber > 0);
}

/**
 * Generate a descriptive name for a file version
 */
export function generateVersionName(fileStub: StirlingFileStub): string {
  const baseName = fileStub.name.replace(/\.pdf$/i, '');

  if (!hasVersionHistory(fileStub)) {
    return fileStub.name;
  }

  const versionInfo = fileStub.versionNumber ? ` (v${fileStub.versionNumber})` : '';
  const toolInfo = fileStub.toolHistory && fileStub.toolHistory.length > 0
    ? ` - ${fileStub.toolHistory[fileStub.toolHistory.length - 1].toolName}`
    : '';

  return `${baseName}${versionInfo}${toolInfo}.pdf`;
}

/**
 * Get recent files efficiently using leaf flags from IndexedDB
 * This is much faster than loading all files and calculating leaf nodes
 */
export async function getRecentLeafFiles(): Promise<import('../services/fileStorage').StoredFile[]> {
  try {
    const { fileStorage } = await import('../services/fileStorage');
    return await fileStorage.getLeafFiles();
  } catch (error) {
    console.warn('Failed to get recent leaf files from IndexedDB:', error);
    return [];
  }
}

/**
 * Get recent file metadata efficiently using leaf flags from IndexedDB
 * This is much faster than loading all files and calculating leaf nodes
 */
export async function getRecentLeafFileMetadata(): Promise<Omit<import('../services/fileStorage').StoredFile, 'data'>[]> {
  try {
    const { fileStorage } = await import('../services/fileStorage');
    return await fileStorage.getLeafFileMetadata();
  } catch (error) {
    console.warn('Failed to get recent leaf file metadata from IndexedDB:', error);
    return [];
  }
}

/**
 * Extract basic file metadata (version number and tool chain) without full history calculation
 * This is lightweight and used for displaying essential info on file thumbnails
 */
export async function extractBasicFileMetadata(
  file: File,
  fileStub: StirlingFileStub
): Promise<StirlingFileStub> {
  // Only process PDF files
  if (!file.type.includes('pdf')) {
    return fileStub;
  }

  try {
    const arrayBuffer = await file.arrayBuffer();
    const historyMetadata = await pdfMetadataService.extractHistoryMetadata(arrayBuffer);

    if (historyMetadata) {
      const history = historyMetadata.stirlingHistory;

      // Update fileStub with essential metadata only (no parent/original relationships)
      return {
        ...fileStub,
        versionNumber: history.versionNumber,
        toolHistory: history.toolChain
      };
    }
  } catch (error) {
    if (DEBUG) console.warn('📄 Failed to extract basic metadata:', file.name, error);
  }

  return fileStub;
}

/**
 * Load file history on-demand for a specific file
 * This replaces the automatic history extraction during file loading
 */
export async function loadFileHistoryOnDemand(
  file: File,
  fileId: FileId,
  updateFileStub?: (id: FileId, updates: Partial<StirlingFileStub>) => void
): Promise<{
  originalFileId?: string;
  versionNumber?: number;
  parentFileId?: FileId;
  toolHistory?: Array<{
    toolName: string;
    timestamp: number;
    parameters?: Record<string, any>;
  }>;
} | null> {
  // Only process PDF files
  if (!file.type.includes('pdf')) {
    return null;
  }

  try {
    const baseFileStub: StirlingFileStub = {
      id: fileId,
      name: file.name,
      size: file.size,
      type: file.type,
      lastModified: file.lastModified
    };

    const updatedFileStub = await extractFileHistory(file, baseFileStub);

    if (updatedFileStub !== baseFileStub && (updatedFileStub.originalFileId || updatedFileStub.versionNumber)) {
      const historyData = {
        originalFileId: updatedFileStub.originalFileId,
        versionNumber: updatedFileStub.versionNumber,
        parentFileId: updatedFileStub.parentFileId,
        toolHistory: updatedFileStub.toolHistory
      };

      // Update the file stub if update function is provided
      if (updateFileStub) {
        updateFileStub(fileId, historyData);
      }

      return historyData;
    }

    return null;
  } catch (error) {
    console.warn(`Failed to load history for ${file.name}:`, error);
    return null;
  }
}

/**
 * Create metadata for storing files with history information
 */
export async function createFileMetadataWithHistory(
  file: File,
  fileId: FileId,
  thumbnail?: string
): Promise<FileMetadata> {
  const baseMetadata: FileMetadata = {
    id: fileId,
    name: file.name,
    type: file.type,
    size: file.size,
    lastModified: file.lastModified,
    thumbnail,
    isLeaf: true // New files are leaf nodes by default
  };

  // Extract metadata for PDF files
  if (file.type.includes('pdf')) {
    try {
      const arrayBuffer = await file.arrayBuffer();
      const [historyMetadata, standardMetadata] = await Promise.all([
        pdfMetadataService.extractHistoryMetadata(arrayBuffer),
        pdfMetadataService.extractStandardMetadata(arrayBuffer)
      ]);

      const result = { ...baseMetadata };

      // Add standard PDF metadata if available
      if (standardMetadata) {
        result.pdfMetadata = standardMetadata;
      }

      // Add history metadata if available (basic version for display)
      if (historyMetadata) {
        const history = historyMetadata.stirlingHistory;
        // Only add basic metadata needed for display, not full history relationships
        result.versionNumber = history.versionNumber;
        result.historyInfo = {
          originalFileId: history.originalFileId,
          parentFileId: history.parentFileId,
          versionNumber: history.versionNumber,
          toolChain: history.toolChain
        };
      }

      return result;
    } catch (error) {
      if (DEBUG) console.warn('📄 Failed to extract metadata:', file.name, error);
    }
  }

  return baseMetadata;
}