import { Logger } from '../../utils/logger';
import { SQLiteMemoryCore } from '../sqlite-memory-core';

/**
 * @interface ConsensusProposal
 * @description Represents a proposal to be voted on by the consensus mechanism.
 */
export interface ConsensusProposal {
  id: string;
  proposerId: string;
  value: any; // The actual value or decision being proposed
  timestamp: number;
}

/**
 * @interface ConsensusResult
 * @description Represents the outcome of a consensus round.
 */
export interface ConsensusResult {
  proposalId: string;
  agreedValue: any | null;
  status: 'agreed' | 'disagreed' | 'failed' | 'in_progress';
  votes: { [participantId: string]: boolean }; // True for agree, false for disagree
  participantsCount: number;
  agreementCount: number;
  disagreementCount: number;
  faultyParticipants?: string[]; // IDs of participants identified as faulty
}

/**
 * @interface ConsensusConfig
 * @description Configuration for the Byzantine Consensus mechanism.
 */
export interface ConsensusConfig {
  minParticipants: number;
  faultTolerancePercentage: number; // e.g., 0.33 for 33% Byzantine fault tolerance
  timeoutMs: number;
  // Add configuration for Cloud Spanner, leader election, etc.
}

/**
 * @class ByzantineConsensus
 * @description Implements a fault-tolerant decision-making mechanism with Byzantine fault tolerance.
 */
export class ByzantineConsensus {
  private config: ConsensusConfig;
  private logger: Logger;
  private dbCore: SQLiteMemoryCore;
  // Placeholder for Cloud Spanner client
  // private spannerClient: any;

  constructor(config: ConsensusConfig, dbCore: SQLiteMemoryCore) {
    this.config = config;
    this.logger = new Logger('ByzantineConsensus');
    this.dbCore = dbCore;
    // Initialize Cloud Spanner client here (conceptual)
  }

  /**
   * Initiates a consensus round for a given proposal.
   * @param {ConsensusProposal} proposal The proposal to achieve consensus on.
   * @param {string[]} participantIds IDs of the participants in this consensus round.
   * @returns {Promise<ConsensusResult>}
   */
  public async propose(proposal: ConsensusProposal, participantIds: string[]): Promise<ConsensusResult> {
    this.logger.info(`Initiating consensus for proposal ${proposal.id} with ${participantIds.length} participants.`);

    if (participantIds.length < this.config.minParticipants) {
      throw new Error(`Not enough participants for consensus. Required: ${this.config.minParticipants}, Actual: ${participantIds.length}`);
    }

    const votes: { [participantId: string]: boolean } = {};
    let agreementCount = 0;
    let disagreementCount = 0;

    // Simulate vote collection from participants
    const votePromises = participantIds.map(async (pId) => {
      // In a real system, this would involve sending the proposal to each participant
      // and waiting for their signed vote. Faulty participants might send incorrect votes.
      await new Promise(resolve => setTimeout(resolve, Math.random() * 50 + 10)); // Simulate network/processing delay

      // Simulate Byzantine behavior: a percentage of participants might vote randomly or maliciously
      const isFaulty = Math.random() < this.config.faultTolerancePercentage;
      const vote = isFaulty ? Math.random() > 0.5 : true; // Faulty agents vote randomly, honest agents agree

      votes[pId] = vote;
      if (vote) { agreementCount++; } else { disagreementCount++; }
    });

    await Promise.all(votePromises);

    const result: ConsensusResult = {
      proposalId: proposal.id,
      agreedValue: null,
      status: 'in_progress',
      votes,
      participantsCount: participantIds.length,
      agreementCount,
      disagreementCount,
    };

    // Determine consensus based on agreement threshold (e.g., 2f+1 for PBFT, or simple majority for crash fault tolerance)
    // For Byzantine fault tolerance, typically > 2/3 agreement is needed among honest nodes.
    const requiredAgreement = Math.ceil(participantIds.length * (1 - this.config.faultTolerancePercentage));

    if (agreementCount >= requiredAgreement) {
      result.status = 'agreed';
      result.agreedValue = proposal.value;
      this.logger.info(`Consensus reached for proposal ${proposal.id}. Agreed value: ${JSON.stringify(proposal.value)}`);
    } else {
      result.status = 'disagreed';
      this.logger.warn(`Consensus failed for proposal ${proposal.id}. Agreement count: ${agreementCount}, Required: ${requiredAgreement}`);
    }

    // Persist consensus result to Cloud Spanner (conceptual)
    // await this.dbCore.runQuery('INSERT INTO consensus_results ...', [result]);

    return result;
  }

  /**
   * Handles automatic leader election and failover mechanisms (conceptual).
   * @param {string[]} availableParticipants IDs of currently available participants.
   * @returns {Promise<string>} The ID of the elected leader.
   */
  public async electLeader(availableParticipants: string[]): Promise<string> {
    this.logger.info(`Electing leader from ${availableParticipants.length} participants...`);
    // In a real system, this would involve a distributed algorithm (e.g., Paxos, Raft, or a specific BFT leader election).
    // For now, simulate a simple election.
    if (availableParticipants.length === 0) {
      throw new Error('No participants available for leader election.');
    }
    const electedLeader = availableParticipants[Math.floor(Math.random() * availableParticipants.length)];
    this.logger.info(`Leader elected: ${electedLeader}`);
    return electedLeader;
  }

  /**
   * Ensures consistency across distributed Google Cloud infrastructure (conceptual).
   * @returns {Promise<void>}
   */
  public async ensureConsistency(): Promise<void> {
    this.logger.info('Ensuring consistency across distributed infrastructure (conceptual)...');
    // This would involve:
    // - Using Cloud Spanner's strong consistency guarantees.
    // - Implementing distributed transactions.
    // - Conflict resolution strategies for eventual consistency models (e.g., CRDTs).
  }

  /**
   * Resolves conflicts using Vertex AI decision models (conceptual).
   * @param {any} conflictData Data representing the conflict.
   * @returns {Promise<any>} The resolved state.
   */
  public async resolveConflict(conflictData: any): Promise<any> {
    this.logger.warn('Resolving conflict using Vertex AI (conceptual)...', conflictData);
    // This would involve sending conflict data to a Vertex AI model for intelligent resolution.
    await new Promise(resolve => setTimeout(resolve, 150)); // Simulate AI resolution
    const resolvedData = { ...conflictData, resolved: true, resolutionMethod: 'vertex_ai_model' };
    this.logger.info('Conflict resolved.', resolvedData);
    return resolvedData;
  }
}