import { Track } from '../types/track';
import * as trackService from '../services/uploadService';

/**
 * Taille par défaut d'un chunk (5MB)
 */
export const CHUNK_SIZE = 5 * 1024 * 1024; // 5MB

/**
 * Seuil pour utiliser le chunked upload (100MB)
 */
const CHUNKED_UPLOAD_THRESHOLD = 10 * 1024 * 1024; // 10MB

/**
 * Divise un fichier en chunks
 * @param file Fichier à diviser
 * @param chunkSize Taille de chaque chunk
 * @returns Tableau de Blobs représentant les chunks
 */
export function splitFileIntoChunks(
  file: File,
  chunkSize: number = CHUNK_SIZE,
): Blob[] {
  const chunks: Blob[] = [];
  let start = 0;

  while (start < file.size) {
    const end = Math.min(start + chunkSize, file.size);
    chunks.push(file.slice(start, end));
    start = end;
  }

  return chunks;
}

/**
 * Calcule le nombre total de chunks nécessaires
 * @param totalSize Taille totale du fichier
 * @param chunkSize Taille de chaque chunk
 * @returns Nombre total de chunks
 */
export function calculateTotalChunks(
  totalSize: number,
  chunkSize: number = CHUNK_SIZE,
): number {
  return Math.ceil(totalSize / chunkSize);
}

/**
 * État d'un upload par chunks
 */
export interface ChunkedUploadState {
  uploadId: string | null;
  totalChunks: number;
  uploadedChunks: number;
  progress: number;
  isPaused: boolean;
  isComplete: boolean;
  error: string | null;
  track: Track | null;
}

/**
 * Gestionnaire d'upload par chunks
 * Gère l'upload d'un fichier volumineux en le divisant en chunks
 */
export class ChunkedUploadManager {
  private file: File;
  private chunks: Blob[];
  private state: ChunkedUploadState;
  private onProgress?: (progress: number) => void;
  private isCancelled = false;
  private currentChunkIndex = 0;

  private readonly MAX_RETRIES = 3;

  constructor(file: File, onProgress?: (progress: number) => void) {
    this.file = file;
    this.chunks = splitFileIntoChunks(file, CHUNK_SIZE);
    this.onProgress = onProgress;
    this.state = {
      uploadId: null,
      totalChunks: this.chunks.length,
      uploadedChunks: 0,
      progress: 0,
      isPaused: false,
      isComplete: false,
      error: null,
      track: null,
    };
  }

  /**
   * Démarre l'upload par chunks
   */
  async start(): Promise<Track> {
    if (this.state.isComplete) {
      if (this.state.track) {
        return this.state.track;
      }
      throw new Error('Upload already completed but no track available');
    }

    if (this.isCancelled) {
      throw new Error('Upload was cancelled');
    }

    try {
      // 1. Initier l'upload
      if (!this.state.uploadId) {
        const uploadId = await trackService.initiateChunkedUpload(
          this.state.totalChunks,
          this.file.size,
          this.file.name,
        );
        this.state.uploadId = uploadId;
      }

      // 2. Uploader chaque chunk séquentiellement
      for (let i = this.currentChunkIndex; i < this.chunks.length; i++) {
        if (this.isCancelled || this.state.isPaused) {
          break;
        }

        this.currentChunkIndex = i;
        const chunk = this.chunks[i];
        const chunkNumber = i + 1; // 1-based

        // Retry logic pour chaque chunk
        let success = false;
        let lastError: Error | null = null;

        for (let retry = 0; retry <= this.MAX_RETRIES; retry++) {
          try {
            const response = await trackService.uploadChunk(
              this.state.uploadId!,
              chunkNumber,
              this.state.totalChunks,
              this.file.size,
              this.file.name,
              chunk,
              (chunkProgress) => {
                // Progression globale = (chunks uploadés + progression du chunk actuel) / total
                const globalProgress =
                  ((i * 100 + chunkProgress) / this.state.totalChunks) * 0.9; // 90% pour l'upload, 10% pour l'assemblage
                this.updateProgress(globalProgress);
              },
            );

            // Le backend retourne la progression dans la réponse
            this.state.uploadedChunks = response.received_chunks;
            this.updateProgress(response.progress * 0.9); // 90% pour l'upload

            success = true;

            break;
          } catch (error) {
            lastError = error as Error;
            if (retry < this.MAX_RETRIES) {
              // Attendre avant de réessayer (backoff exponentiel)
              await new Promise((resolve) =>
                setTimeout(resolve, Math.pow(2, retry) * 1000),
              );
            }
          }
        }

        if (!success) {
          throw lastError || new Error('Failed to upload chunk after retries');
        }
      }

      // 3. Vérifier que tous les chunks ont été uploadés
      if (this.isCancelled) {
        throw new Error('Upload was cancelled');
      }

      if (this.state.uploadedChunks < this.state.totalChunks) {
        throw new Error(
          `Not all chunks uploaded: ${this.state.uploadedChunks}/${this.state.totalChunks}`,
        );
      }

      // 4. Compléter l'upload
      this.updateProgress(95);
      const track = await trackService.completeChunkedUpload(
        this.state.uploadId!,
      );

      this.state.track = track;
      this.state.isComplete = true;
      this.updateProgress(100);

      return track;
    } catch (error) {
      this.state.error =
        error instanceof Error ? error.message : 'Unknown error occurred';
      throw error;
    }
  }

  /**
   * Met en pause l'upload
   */
  pause(): void {
    this.state.isPaused = true;
  }

  /**
   * Reprend l'upload
   */
  async resume(): Promise<Track> {
    if (this.state.isComplete) {
      if (this.state.track) {
        return this.state.track;
      }
      throw new Error('Upload already completed but no track available');
    }

    this.state.isPaused = false;
    return this.start();
  }

  /**
   * Annule l'upload
   */
  cancel(): void {
    this.isCancelled = true;
    this.state.isPaused = true;
    this.state.error = 'Upload cancelled';
  }

  /**
   * Retourne l'état actuel de l'upload
   */
  getState(): ChunkedUploadState {
    return { ...this.state };
  }

  /**
   * Met à jour la progression et appelle le callback
   */
  private updateProgress(progress: number): void {
    this.state.progress = Math.min(100, Math.max(0, progress));
    if (this.onProgress) {
      this.onProgress(this.state.progress);
    }
  }
}

/**
 * Détermine si un fichier doit utiliser le chunked upload
 * @param file Fichier à vérifier
 * @returns true si le fichier est > 100MB
 */
export function shouldUseChunkedUpload(file: File): boolean {
  return file.size > CHUNKED_UPLOAD_THRESHOLD;
}