import { Injectable, inject } from '@angular/core';
import { recordDebugNetworkFileChunk } from '../../../../infrastructure/realtime/logging/debug-network-metrics';
import { RealtimeSessionFacade } from '../../../../core/realtime';
import { AttachmentStorageService } from '../../infrastructure/services/attachment-storage.service';
import { MAX_AUTO_SAVE_SIZE_BYTES } from '../../domain/constants/attachment.constants';
import { shouldPersistDownloadedAttachment } from '../../domain/logic/attachment.logic';
import type { Attachment, AttachmentMeta } from '../../domain/models/attachment.model';
import {
  ATTACHMENT_TRANSFER_EWMA_CURRENT_WEIGHT,
  ATTACHMENT_TRANSFER_EWMA_PREVIOUS_WEIGHT,
  DEFAULT_ATTACHMENT_MIME_TYPE,
  FILE_NOT_FOUND_REQUEST_ERROR,
  NO_CONNECTED_PEERS_REQUEST_ERROR
} from '../../domain/constants/attachment-transfer.constants';
import {
  type FileAnnounceEvent,
  type FileAnnouncePayload,
  type FileCancelEvent,
  type FileCancelPayload,
  type FileChunkPayload,
  type FileNotFoundEvent,
  type FileNotFoundPayload,
  type FileRequestEvent,
  type FileRequestPayload,
  type LocalFileWithPath
} from '../../domain/models/attachment-transfer.model';
import { AttachmentPersistenceService } from './attachment-persistence.service';
import { AttachmentRuntimeStore } from './attachment-runtime.store';
import { AttachmentTransferTransportService } from './attachment-transfer-transport.service';

@Injectable({ providedIn: 'root' })
export class AttachmentTransferService {
  private readonly webrtc = inject(RealtimeSessionFacade);
  private readonly runtimeStore = inject(AttachmentRuntimeStore);
  private readonly attachmentStorage = inject(AttachmentStorageService);
  private readonly persistence = inject(AttachmentPersistenceService);
  private readonly transport = inject(AttachmentTransferTransportService);

  getAttachmentMetasForMessages(messageIds: string[]): Record<string, AttachmentMeta[]> {
    const result: Record<string, AttachmentMeta[]> = {};

    for (const messageId of messageIds) {
      const attachments = this.runtimeStore.getAttachmentsForMessage(messageId);

      if (attachments.length > 0) {
        result[messageId] = attachments.map((attachment) => ({
          id: attachment.id,
          messageId: attachment.messageId,
          filename: attachment.filename,
          size: attachment.size,
          mime: attachment.mime,
          isImage: attachment.isImage,
          uploaderPeerId: attachment.uploaderPeerId,
          filePath: undefined,
          savedPath: undefined
        }));
      }
    }

    return result;
  }

  registerSyncedAttachments(
    attachmentMap: Record<string, AttachmentMeta[]>,
    messageRoomIds?: Record<string, string>
  ): void {
    if (messageRoomIds) {
      for (const [messageId, roomId] of Object.entries(messageRoomIds)) {
        this.runtimeStore.rememberMessageRoom(messageId, roomId);
      }
    }

    const newAttachments: Attachment[] = [];

    for (const [messageId, metas] of Object.entries(attachmentMap)) {
      const existing = [...this.runtimeStore.getAttachmentsForMessage(messageId)];

      for (const meta of metas) {
        const alreadyKnown = existing.find((entry) => entry.id === meta.id);

        if (!alreadyKnown) {
          const attachment: Attachment = { ...meta,
            available: false,
            receivedBytes: 0 };

          existing.push(attachment);
          newAttachments.push(attachment);
        }
      }

      this.runtimeStore.setAttachmentsForMessage(messageId, existing);
    }

    if (newAttachments.length > 0) {
      this.runtimeStore.touch();

      for (const attachment of newAttachments) {
        void this.persistence.persistAttachmentMeta(attachment);
      }
    }
  }

  requestFromAnyPeer(messageId: string, attachment: Attachment): void {
    const clearedRequestError = this.clearAttachmentRequestError(attachment);
    const connectedPeers = this.webrtc.getConnectedPeers();

    if (connectedPeers.length === 0) {
      attachment.requestError = NO_CONNECTED_PEERS_REQUEST_ERROR;
      this.runtimeStore.touch();
      console.warn('[Attachments] No connected peers to request file from');
      return;
    }

    if (clearedRequestError)
      this.runtimeStore.touch();

    this.runtimeStore.setPendingRequestPeers(
      this.buildRequestKey(messageId, attachment.id),
      new Set<string>()
    );

    this.sendFileRequestToNextPeer(messageId, attachment.id, attachment.uploaderPeerId);
  }

  handleFileNotFound(payload: FileNotFoundPayload): void {
    const { messageId, fileId } = payload;

    if (!messageId || !fileId)
      return;

    const attachments = this.runtimeStore.getAttachmentsForMessage(messageId);
    const attachment = attachments.find((entry) => entry.id === fileId);
    const didSendRequest = this.sendFileRequestToNextPeer(messageId, fileId, attachment?.uploaderPeerId);

    if (!didSendRequest && attachment) {
      attachment.requestError = FILE_NOT_FOUND_REQUEST_ERROR;
      this.runtimeStore.touch();
    }
  }

  requestImageFromAnyPeer(messageId: string, attachment: Attachment): void {
    this.requestFromAnyPeer(messageId, attachment);
  }

  requestFile(messageId: string, attachment: Attachment): void {
    this.requestFromAnyPeer(messageId, attachment);
  }

  hasPendingRequest(messageId: string, fileId: string): boolean {
    return this.runtimeStore.hasPendingRequest(this.buildRequestKey(messageId, fileId));
  }

  async publishAttachments(
    messageId: string,
    files: File[],
    uploaderPeerId?: string
  ): Promise<void> {
    const attachments: Attachment[] = [];

    for (const file of files) {
      const fileId = crypto.randomUUID?.() ?? `${Date.now()}-${Math.random()}`;
      const attachment: Attachment = {
        id: fileId,
        messageId,
        filename: file.name,
        size: file.size,
        mime: file.type || DEFAULT_ATTACHMENT_MIME_TYPE,
        isImage: file.type.startsWith('image/'),
        uploaderPeerId,
        filePath: (file as LocalFileWithPath).path,
        available: false
      };

      attachments.push(attachment);
      this.runtimeStore.setOriginalFile(`${messageId}:${fileId}`, file);

      try {
        attachment.objectUrl = URL.createObjectURL(file);
        attachment.available = true;
      } catch { /* non-critical */ }

      if (attachment.size <= MAX_AUTO_SAVE_SIZE_BYTES) {
        void this.persistence.saveFileToDisk(attachment, file);
      }

      const fileAnnounceEvent: FileAnnounceEvent = {
        type: 'file-announce',
        messageId,
        file: {
          id: fileId,
          filename: attachment.filename,
          size: attachment.size,
          mime: attachment.mime,
          isImage: attachment.isImage,
          uploaderPeerId
        }
      };

      this.webrtc.broadcastMessage(fileAnnounceEvent);
    }

    const existingList = this.runtimeStore.getAttachmentsForMessage(messageId);

    this.runtimeStore.setAttachmentsForMessage(messageId, [...existingList, ...attachments]);
    this.runtimeStore.touch();

    for (const attachment of attachments) {
      void this.persistence.persistAttachmentMeta(attachment);
    }
  }

  handleFileAnnounce(payload: FileAnnouncePayload): void {
    const { messageId, file } = payload;

    if (!messageId || !file)
      return;

    const list = [...this.runtimeStore.getAttachmentsForMessage(messageId)];
    const alreadyKnown = list.find((entry) => entry.id === file.id);

    if (alreadyKnown)
      return;

    const attachment: Attachment = {
      id: file.id,
      messageId,
      filename: file.filename,
      size: file.size,
      mime: file.mime,
      isImage: !!file.isImage,
      uploaderPeerId: file.uploaderPeerId,
      available: false,
      receivedBytes: 0
    };

    list.push(attachment);
    this.runtimeStore.setAttachmentsForMessage(messageId, list);
    this.runtimeStore.touch();
    void this.persistence.persistAttachmentMeta(attachment);
  }

  handleFileChunk(payload: FileChunkPayload): void {
    const { messageId, fileId, fromPeerId, index, total, data } = payload;

    if (
      !messageId || !fileId ||
      typeof index !== 'number' ||
      typeof total !== 'number' ||
      typeof data !== 'string'
    ) {
      return;
    }

    const list = this.runtimeStore.getAttachmentsForMessage(messageId);
    const attachment = list.find((entry) => entry.id === fileId);

    if (!attachment)
      return;

    const decodedBytes = this.transport.decodeBase64(data);
    const assemblyKey = `${messageId}:${fileId}`;
    const requestKey = this.buildRequestKey(messageId, fileId);

    this.runtimeStore.deletePendingRequest(requestKey);
    this.clearAttachmentRequestError(attachment);

    const chunkBuffer = this.getOrCreateChunkBuffer(assemblyKey, total);

    if (!chunkBuffer[index]) {
      chunkBuffer[index] = decodedBytes.buffer as ArrayBuffer;
      this.runtimeStore.setChunkCount(assemblyKey, (this.runtimeStore.getChunkCount(assemblyKey) ?? 0) + 1);
    }

    this.updateTransferProgress(attachment, decodedBytes, fromPeerId);

    this.runtimeStore.touch();
    this.finalizeTransferIfComplete(attachment, assemblyKey, total);
  }

  async handleFileRequest(payload: FileRequestPayload): Promise<void> {
    const { messageId, fileId, fromPeerId } = payload;

    if (!messageId || !fileId || !fromPeerId)
      return;

    const exactKey = `${messageId}:${fileId}`;
    const originalFile = this.runtimeStore.getOriginalFile(exactKey)
      ?? this.runtimeStore.findOriginalFileByFileId(fileId);

    if (originalFile) {
      await this.transport.streamFileToPeer(
        fromPeerId,
        messageId,
        fileId,
        originalFile,
        () => this.isTransferCancelled(fromPeerId, messageId, fileId)
      );

      return;
    }

    const list = this.runtimeStore.getAttachmentsForMessage(messageId);
    const attachment = list.find((entry) => entry.id === fileId);
    const diskPath = attachment
      ? await this.attachmentStorage.resolveExistingPath(attachment)
      : null;

    if (diskPath) {
      await this.transport.streamFileFromDiskToPeer(
        fromPeerId,
        messageId,
        fileId,
        diskPath,
        () => this.isTransferCancelled(fromPeerId, messageId, fileId)
      );

      return;
    }

    if (attachment?.isImage) {
      const roomName = await this.persistence.resolveCurrentRoomName();
      const legacyDiskPath = await this.attachmentStorage.resolveLegacyImagePath(
        attachment.filename,
        roomName
      );

      if (legacyDiskPath) {
        await this.transport.streamFileFromDiskToPeer(
          fromPeerId,
          messageId,
          fileId,
          legacyDiskPath,
          () => this.isTransferCancelled(fromPeerId, messageId, fileId)
        );

        return;
      }
    }

    if (attachment?.available && attachment.objectUrl) {
      try {
        const response = await fetch(attachment.objectUrl);
        const blob = await response.blob();
        const file = new File([blob], attachment.filename, { type: attachment.mime });

        await this.transport.streamFileToPeer(
          fromPeerId,
          messageId,
          fileId,
          file,
          () => this.isTransferCancelled(fromPeerId, messageId, fileId)
        );

        return;
      } catch { /* fall through */ }
    }

    const fileNotFoundEvent: FileNotFoundEvent = {
      type: 'file-not-found',
      messageId,
      fileId
    };

    this.webrtc.sendToPeer(fromPeerId, fileNotFoundEvent);
  }

  cancelRequest(messageId: string, attachment: Attachment): void {
    const targetPeerId = attachment.uploaderPeerId;

    if (!targetPeerId)
      return;

    try {
      const assemblyKey = `${messageId}:${attachment.id}`;

      this.runtimeStore.deleteChunkBuffer(assemblyKey);
      this.runtimeStore.deleteChunkCount(assemblyKey);

      attachment.receivedBytes = 0;
      attachment.speedBps = 0;
      attachment.startedAtMs = undefined;
      attachment.lastUpdateMs = undefined;

      if (attachment.objectUrl) {
        try {
          URL.revokeObjectURL(attachment.objectUrl);
        } catch { /* ignore */ }

        attachment.objectUrl = undefined;
      }

      attachment.available = false;
      this.runtimeStore.touch();

      const fileCancelEvent: FileCancelEvent = {
        type: 'file-cancel',
        messageId,
        fileId: attachment.id
      };

      this.webrtc.sendToPeer(targetPeerId, fileCancelEvent);
    } catch { /* best-effort */ }
  }

  handleFileCancel(payload: FileCancelPayload): void {
    const { messageId, fileId, fromPeerId } = payload;

    if (!messageId || !fileId || !fromPeerId)
      return;

    this.runtimeStore.addCancelledTransfer(
      this.buildTransferKey(messageId, fileId, fromPeerId)
    );
  }

  async fulfillRequestWithFile(
    messageId: string,
    fileId: string,
    targetPeerId: string,
    file: File
  ): Promise<void> {
    this.runtimeStore.setOriginalFile(`${messageId}:${fileId}`, file);
    await this.transport.streamFileToPeer(
      targetPeerId,
      messageId,
      fileId,
      file,
      () => this.isTransferCancelled(targetPeerId, messageId, fileId)
    );
  }

  private buildTransferKey(messageId: string, fileId: string, peerId: string): string {
    return `${messageId}:${fileId}:${peerId}`;
  }

  private buildRequestKey(messageId: string, fileId: string): string {
    return `${messageId}:${fileId}`;
  }

  private clearAttachmentRequestError(attachment: Attachment): boolean {
    if (!attachment.requestError)
      return false;

    attachment.requestError = undefined;
    return true;
  }

  private isTransferCancelled(targetPeerId: string, messageId: string, fileId: string): boolean {
    return this.runtimeStore.hasCancelledTransfer(
      this.buildTransferKey(messageId, fileId, targetPeerId)
    );
  }

  private sendFileRequestToNextPeer(
    messageId: string,
    fileId: string,
    preferredPeerId?: string
  ): boolean {
    const connectedPeers = this.webrtc.getConnectedPeers();
    const requestKey = this.buildRequestKey(messageId, fileId);
    const triedPeers = this.runtimeStore.getPendingRequestPeers(requestKey) ?? new Set<string>();

    let targetPeerId: string | undefined;

    if (preferredPeerId && connectedPeers.includes(preferredPeerId) && !triedPeers.has(preferredPeerId)) {
      targetPeerId = preferredPeerId;
    } else {
      targetPeerId = connectedPeers.find((peerId) => !triedPeers.has(peerId));
    }

    if (!targetPeerId) {
      this.runtimeStore.deletePendingRequest(requestKey);
      return false;
    }

    triedPeers.add(targetPeerId);
    this.runtimeStore.setPendingRequestPeers(requestKey, triedPeers);

    const fileRequestEvent: FileRequestEvent = {
      type: 'file-request',
      messageId,
      fileId
    };

    this.webrtc.sendToPeer(targetPeerId, fileRequestEvent);

    return true;
  }

  private getOrCreateChunkBuffer(assemblyKey: string, total: number): ArrayBuffer[] {
    const existingChunkBuffer = this.runtimeStore.getChunkBuffer(assemblyKey);

    if (existingChunkBuffer) {
      return existingChunkBuffer;
    }

    const createdChunkBuffer = new Array(total);

    this.runtimeStore.setChunkBuffer(assemblyKey, createdChunkBuffer);
    this.runtimeStore.setChunkCount(assemblyKey, 0);

    return createdChunkBuffer;
  }

  private updateTransferProgress(
    attachment: Attachment,
    decodedBytes: Uint8Array,
    fromPeerId?: string
  ): void {
    const now = Date.now();
    const previousReceived = attachment.receivedBytes ?? 0;

    attachment.receivedBytes = previousReceived + decodedBytes.byteLength;

    if (fromPeerId) {
      recordDebugNetworkFileChunk(fromPeerId, decodedBytes.byteLength, now);
    }

    if (!attachment.startedAtMs)
      attachment.startedAtMs = now;

    if (!attachment.lastUpdateMs)
      attachment.lastUpdateMs = now;

    const elapsedMs = Math.max(1, now - attachment.lastUpdateMs);
    const instantaneousBps = (decodedBytes.byteLength / elapsedMs) * 1000;
    const previousSpeed = attachment.speedBps ?? instantaneousBps;

    attachment.speedBps =
      ATTACHMENT_TRANSFER_EWMA_PREVIOUS_WEIGHT * previousSpeed +
      ATTACHMENT_TRANSFER_EWMA_CURRENT_WEIGHT * instantaneousBps;

    attachment.lastUpdateMs = now;
  }

  private finalizeTransferIfComplete(
    attachment: Attachment,
    assemblyKey: string,
    total: number
  ): void {
    const receivedChunkCount = this.runtimeStore.getChunkCount(assemblyKey) ?? 0;
    const completeBuffer = this.runtimeStore.getChunkBuffer(assemblyKey);

    if (
      !completeBuffer
      || (receivedChunkCount !== total && (attachment.receivedBytes ?? 0) < attachment.size)
      || !completeBuffer.every((part) => part instanceof ArrayBuffer)
    ) {
      return;
    }

    const blob = new Blob(completeBuffer, { type: attachment.mime });

    attachment.available = true;
    attachment.objectUrl = URL.createObjectURL(blob);

    if (shouldPersistDownloadedAttachment(attachment)) {
      void this.persistence.saveFileToDisk(attachment, blob);
    }

    this.runtimeStore.deleteChunkBuffer(assemblyKey);
    this.runtimeStore.deleteChunkCount(assemblyKey);
    this.runtimeStore.touch();
    void this.persistence.persistAttachmentMeta(attachment);
  }
}