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import Block from "./block.ts";import { UseHasher } from "./typings.ts";
class Blockchain<T> {  constructor(    private useHasher: UseHasher,    private blocks: Block<T>[] = []  ) {}
  private buildHash({ payload, index, prevHash }: Omit<Block<T>, 'hash'>) {    let formattedDataToHash: Uint8Array;    const suffix = index + (prevHash ?? '');
    if(payload instanceof Uint8Array) {        formattedDataToHash = new Uint8Array([            ...payload,            ...new TextEncoder().encode(suffix)        ]);    } else if(typeof payload === 'string') {        formattedDataToHash = new TextEncoder().encode(payload + suffix);    } else if(typeof payload === 'object') {        formattedDataToHash = new TextEncoder().encode(JSON.stringify(payload) + suffix)    } else {        throw new Error('Unrecognized payload format; expected Uint8Array, string or object');    }
    return this.useHasher(        formattedDataToHash    );  }
  addBlock(payload: T) {    const { hash: prevHash = null } = this.blocks[this.blocks.length - 1] ?? {};    const index = this.blocks.length;
    const hash = this.buildHash({ payload, index, prevHash });
    this.blocks.push({        index: this.blocks.length,        payload,        hash,        prevHash    })    return this;  }
  validateIntegrity() {    let prevHash: string|null = null;
    for(let i = 0; i < this.blocks.length; i++) {        const currentBlock = this.blocks[i];        if(prevHash !== currentBlock.prevHash) {            throw new Error(`Previous hash ${currentBlock.prevHash} did not match expected value ${prevHash}.`);        }
        const currentHash = this.buildHash({            ...currentBlock,            prevHash        });
        if(currentHash !== currentBlock.hash) {            throw new Error(`Expected hash ${currentHash} but got ${currentBlock.hash} at index ${i}`)        }
        prevHash = currentHash;    }  }
  toArray() {    return structuredClone(this.blocks);  }}
export default Blockchain;