import * as borsh from "@coral-xyz/borsh";
import type { Connection } from "@solana/web3.js";
import { SYSVAR_CLOCK_PUBKEY } from "@solana/web3.js";
import type { BN } from "@switchboard-xyz/common";

export interface SolanaClockDataFields {
  slot: BN;
  epochStartTimestamp: BN;
  epoch: BN;
  leaderScheduleEpoch: BN;
  unixTimestamp: BN;
}

export class SolanaClock {
  slot: BN;
  epochStartTimestamp: BN;
  epoch: BN;
  leaderScheduleEpoch: BN;
  unixTimestamp: BN;

  static readonly layout = borsh.struct([
    borsh.u64("slot"),
    borsh.i64("epochStartTimestamp"),
    borsh.u64("epoch"),
    borsh.u64("leaderScheduleEpoch"),
    borsh.i64("unixTimestamp"),
  ]);

  constructor(fields: SolanaClockDataFields) {
    this.slot = fields.slot;
    this.epochStartTimestamp = fields.epochStartTimestamp;
    this.epoch = fields.epoch;
    this.leaderScheduleEpoch = fields.epochStartTimestamp;
    this.unixTimestamp = fields.unixTimestamp;
  }

  static decode(data: Buffer): SolanaClock {
    const dec = SolanaClock.layout.decode(data) as SolanaClockDataFields;

    return new SolanaClock({
      slot: dec.slot,
      epochStartTimestamp: dec.epochStartTimestamp,
      epoch: dec.epoch,
      leaderScheduleEpoch: dec.leaderScheduleEpoch,
      unixTimestamp: dec.unixTimestamp,
    });
  }

  static decodeUnixTimestamp(data: Buffer): BN {
    return borsh.u64("unixTimestamp").decode(data, data.byteLength - 8);
  }

  static async fetch(connection: Connection): Promise<SolanaClock> {
    const sysclockInfo = await connection.getAccountInfo(SYSVAR_CLOCK_PUBKEY);
    if (!sysclockInfo) {
      throw new Error(`Failed to fetch SYSVAR_CLOCK AccountInfo`);
    }
    const clock = SolanaClock.decode(sysclockInfo.data);
    return clock;
  }
}