/**
 * Base chain adapter: RPC abstraction, receipt/log fetch, reorg detection, fallback RPC.
 */

import { JsonRpcProvider, TransactionReceipt, Log } from 'ethers';
import type { ChainAdapterConfig, NormalizedReceipt, NormalizedLog, IChainAdapter } from './types.js';
import { getChainConfig } from './config.js';

function toHex(n: bigint): string {
  return '0x' + n.toString(16);
}

export abstract class BaseChainAdapter implements IChainAdapter {
  protected provider: JsonRpcProvider;
  protected config: ChainAdapterConfig;
  private rpcIndex = 0;

  constructor(chainId: number, rpcUrls?: string[]) {
    const cfg = getChainConfig(chainId);
    if (!cfg) throw new Error(`Unknown chainId: ${chainId}`);
    this.config = rpcUrls?.length ? { ...cfg, rpcUrls } : cfg;
    this.provider = new JsonRpcProvider(this.config.rpcUrls[0]);
  }

  getChainId(): number {
    return this.config.chainId;
  }

  getConfig(): ChainAdapterConfig {
    return this.config;
  }

  protected getRpcUrl(): string {
    return this.config.rpcUrls[this.rpcIndex % this.config.rpcUrls.length];
  }

  protected async switchRpc(): Promise<void> {
    if (this.config.rpcUrls.length <= 1) return;
    this.rpcIndex++;
    this.provider = new JsonRpcProvider(this.getRpcUrl());
  }

  async getBlockNumber(): Promise<number> {
    const n = await this.provider.getBlockNumber();
    return n;
  }

  async getBlock(blockNumber: number): Promise<{ number: number; hash: string; parentHash: string; timestamp: number } | null> {
    try {
      const block = await this.provider.getBlock(blockNumber);
      if (!block) return null;
      return {
        number: block.number,
        hash: block.hash ?? '',
        parentHash: block.parentHash ?? '',
        timestamp: block.timestamp,
      };
    } catch {
      return null;
    }
  }

  async sendTransaction(signedTxHex: string): Promise<{ hash: string; from: string; nonce: number }> {
    const tx = await this.provider.broadcastTransaction(signedTxHex);
    return {
      hash: tx.hash,
      from: tx.from ?? '',
      nonce: tx.nonce,
    };
  }

  async getTransactionReceipt(txHash: string): Promise<NormalizedReceipt | null> {
    try {
      const receipt = await this.provider.getTransactionReceipt(txHash);
      if (!receipt) return null;
      return this.normalizeReceipt(receipt);
    } catch {
      return null;
    }
  }

  protected normalizeReceipt(receipt: TransactionReceipt): NormalizedReceipt {
    return {
      chainId: this.config.chainId,
      transactionHash: receipt.hash,
      blockNumber: BigInt(receipt.blockNumber),
      blockHash: receipt.blockHash ?? '',
      transactionIndex: receipt.index,
      from: receipt.from,
      to: receipt.to ?? null,
      gasUsed: BigInt(receipt.gasUsed.toString()),
      cumulativeGasUsed: BigInt(receipt.cumulativeGasUsed.toString()),
      contractAddress: receipt.contractAddress ?? null,
      logsBloom: receipt.logsBloom ?? '',
      status: receipt.status === 1 ? 1 : 0,
      root: receipt.root ?? null,
    };
  }

  async getLogs(
    fromBlock: number,
    toBlock: number,
    address?: string,
    topics?: string[]
  ): Promise<NormalizedLog[]> {
    const filter: { fromBlock: number; toBlock: number; address?: string; topics?: string[] } = {
      fromBlock,
      toBlock,
    };
    if (address) filter.address = address;
    if (topics?.length) filter.topics = topics as `0x${string}`[];
    const logs = await this.provider.getLogs(filter);
    return logs.map((log) => this.normalizeLog(log));
  }

  protected normalizeLog(log: Log): NormalizedLog {
    const topics = log.topics as string[];
    return {
      chainId: this.config.chainId,
      transactionHash: log.transactionHash,
      blockNumber: BigInt(log.blockNumber),
      blockHash: log.blockHash ?? '',
      logIndex: log.index,
      address: log.address,
      topic0: topics[0] ?? null,
      topic1: topics[1] ?? null,
      topic2: topics[2] ?? null,
      topic3: topics[3] ?? null,
      data: log.data,
    };
  }

  async detectReorg(blockNumber: number, expectedBlockHash: string): Promise<boolean> {
    const block = await this.getBlock(blockNumber);
    if (!block) return true;
    return block.hash.toLowerCase() !== expectedBlockHash.toLowerCase();
  }

  async healthCheck(): Promise<boolean> {
    try {
      await this.provider.getBlockNumber();
      return true;
    } catch {
      if (this.config.rpcUrls.length > 1) {
        await this.switchRpc();
        try {
          await this.provider.getBlockNumber();
          return true;
        } catch {
          return false;
        }
      }
      return false;
    }
  }
}