From cc5cbdb8605fa3170eea964b2ad8765fc73f1caa Mon Sep 17 00:00:00 2001
From: Derrick Hammer <derrick@derrickhammer.com>
Date: Thu, 7 Sep 2023 18:40:27 -0400
Subject: [PATCH] feat: add CID class

---
 src/cid.ts   | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/index.ts |   3 +-
 2 files changed, 114 insertions(+), 1 deletion(-)
 create mode 100644 src/cid.ts

diff --git a/src/cid.ts b/src/cid.ts
new file mode 100644
index 0000000..8ea03c8
--- /dev/null
+++ b/src/cid.ts
@@ -0,0 +1,112 @@
+import Multibase from "#multibase.js";
+import { Multihash } from "#multihash.js";
+import { CID_TYPES, REGISTRY_TYPES } from "#constants.js";
+import { decodeEndian, encodeEndian } from "#util.js";
+import { concatBytes, equalBytes } from "@noble/curves/abstract/utils";
+
+export default class CID extends Multibase {
+  type: number;
+  hash: Multihash;
+  size?: number;
+
+  constructor(type: number, hash: Multihash, size?: number) {
+    super();
+    this.type = type;
+    this.hash = hash;
+    this.size = size;
+  }
+
+  static decode(cid: string): CID {
+    const decodedBytes = Multibase.decodeString(cid);
+    return CID._init(decodedBytes);
+  }
+
+  static fromBytes(bytes: Uint8Array): CID {
+    return CID._init(bytes);
+  }
+
+  private static _init(bytes: Uint8Array): CID {
+    const type = bytes[0];
+    if (type === CID_TYPES.BRIDGE) {
+      return new CID(type, new Multihash(bytes));
+    }
+
+    const hash = new Multihash(bytes.subarray(1, 34));
+    let size: number | undefined = undefined;
+    const sizeBytes = bytes.subarray(34);
+    if (sizeBytes.length > 0) {
+      size = decodeEndian(sizeBytes);
+    }
+
+    if (!Object.values(CID_TYPES).includes(type)) {
+      throw new Error(`invalid cid type ${type}`);
+    }
+
+    return new CID(type, hash, size);
+  }
+
+  copyWith({ size, type }: { type?: number; size?: number }): CID {
+    type = type || this.type;
+
+    if (!Object.values(CID_TYPES).includes(type)) {
+      throw new Error(`invalid cid type ${type}`);
+    }
+
+    return new CID(type, this.hash, size || this.size);
+  }
+
+  toBytes(): Uint8Array {
+    if (this.type === CID_TYPES.BRIDGE) {
+      return this.hash.fullBytes;
+    } else if (this.type === CID_TYPES.RAW) {
+      let sizeBytes = encodeEndian(this.size as number, 8);
+
+      while (sizeBytes.length > 0 && sizeBytes[sizeBytes.length - 1] === 0) {
+        sizeBytes = sizeBytes.slice(0, -1);
+      }
+      if (sizeBytes.length === 0) {
+        sizeBytes = new Uint8Array(1);
+      }
+
+      return concatBytes(
+        this._getPrefixBytes(),
+        this.hash.fullBytes,
+        sizeBytes,
+      );
+    }
+
+    return concatBytes(this._getPrefixBytes(), this.hash.fullBytes);
+  }
+
+  private _getPrefixBytes(): Uint8Array {
+    return Uint8Array.from([this.type]);
+  }
+
+  toRegistryEntry(): Uint8Array {
+    return concatBytes(Uint8Array.from([REGISTRY_TYPES.CID]), this.toBytes());
+  }
+
+  toRegistryCID(): Uint8Array {
+    return this.copyWith({ type: CID_TYPES.RESOLVER }).toBytes();
+  }
+
+  toString(): string {
+    return this.type === CID_TYPES.BRIDGE
+      ? Buffer.from(this.hash.fullBytes).toString("utf8")
+      : this.toBase58();
+  }
+
+  equals(other: CID): boolean {
+    return equalBytes(this.toBytes(), other.toBytes());
+  }
+
+  hashCode(): number {
+    const fullBytes = this.toBytes();
+    return (
+      fullBytes[0] +
+      fullBytes[1] * 256 +
+      fullBytes[2] * 256 * 256 +
+      fullBytes[3] * 256 * 256 * 256
+    );
+  }
+}
diff --git a/src/index.ts b/src/index.ts
index d8f10b9..ae426d8 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -4,6 +4,7 @@ import { ed25519 } from "@noble/curves/ed25519";
 import KeyPairEd25519 from "#ed25519.js";
 import { S5NodeConfig } from "./types.js";
 import NodeId from "#nodeId.js";
+import CID from "#cid.js";
 
 export * from "./types.js";
 export * from "./constants.js";
@@ -16,7 +17,7 @@ export {
   BasePeer,
 } from "./transports/index.js";
 export type { SignedRegistryEntry };
-export { NodeId };
+export { NodeId, CID };
 
 export function createNode(config: S5NodeConfig) {
   return new S5Node(config);