Initial commit

packages/shared/src/protocol.ts

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+/**
+ * BitTorrent Protocol Structures (BEP 9 & 10)
+ * This file defines the structures for the Extension Protocol and Metadata Extension.
+ */
+
+export interface ExtensionHandshake {
+  m: { [extensionName: string]: number }; // Supported extensions and their local IDs
+  p?: number; // Local TCP port
+  v?: string; // Client version string
+  metadata_size?: number; // Total size of the info dictionary in bytes
+}
+
+export interface MetadataRequest {
+  msg_type: number; // 0 for request, 1 for data, 2 for reject
+  piece: number; // The piece index being requested
+  total_size?: number; // Only for data messages
+}
+
+/**
+ * Simulates the reassembly of metadata pieces.
+ * In a real scenario, these pieces would come from different peers over individual TCP packets.
+ */
+export class MetadataReassembler {
+  private pieces: Map<number, Uint8Array> = new Map();
+  private totalSize: number;
+  private pieceSize: number = 16384; // 16KiB
+
+  constructor(totalSize: number) {
+    this.totalSize = totalSize;
+  }
+
+  public addPiece(index: number, data: Uint8Array): boolean {
+    this.pieces.set(index, data);
+    return this.isComplete();
+  }
+
+  public isComplete(): boolean {
+    const totalPieces = Math.ceil(this.totalSize / this.pieceSize);
+    return this.pieces.size === totalPieces;
+  }
+
+  public getFullMetadata(): Uint8Array | null {
+    if (!this.isComplete()) return null;
+
+    const fullData = new Uint8Array(this.totalSize);
+    const sortedIndices = Array.from(this.pieces.keys()).sort((a, b) => a - b);
+
+    let offset = 0;
+    for (const index of sortedIndices) {
+      const piece = this.pieces.get(index)!;
+      fullData.set(piece, offset);
+      offset += piece.length;
+    }
+
+    return fullData;
+  }
+
+  public getProgress(): number {
+    const totalPieces = Math.ceil(this.totalSize / this.pieceSize);
+    return (this.pieces.size / totalPieces) * 100;
+  }
+}
+
+/**
+ * Tracks which pieces we have and provides bitfield generation.
+ */
+export class Bitfield {
+  private bits: Uint8Array;
+  public totalPieces: number;
+
+  constructor(totalPieces: number) {
+    this.totalPieces = totalPieces;
+    this.bits = new Uint8Array(Math.ceil(totalPieces / 8));
+  }
+
+  public set(index: number) {
+    if (index >= this.totalPieces) return;
+    const byteIndex = Math.floor(index / 8);
+    const bitIndex = 7 - (index % 8);
+    this.bits[byteIndex] |= (1 << bitIndex);
+  }
+
+  public has(index: number): boolean {
+    if (index >= this.totalPieces) return false;
+    const byteIndex = Math.floor(index / 8);
+    const bitIndex = 7 - (index % 8);
+    return (this.bits[byteIndex] & (1 << bitIndex)) !== 0;
+  }
+
+  public toBuffer(): Uint8Array {
+    return this.bits;
+  }
+
+  public fromBuffer(buffer: Uint8Array) {
+    this.bits = new Uint8Array(buffer);
+  }
+}