RedditBot/src/services/strategy-selector.ts

import type { Config } from '../config/index.js';
import type { MessagesRepository, StrategyStats } from '../database/repositories.js';
import type { Logger } from '../utils/logger.js';

export interface SelectedStrategy {
  id: string;
  promptOverride: string;
  reason: 'exploit' | 'explore';
}

export class StrategySelector {
  private variants: Config['strategies']['variants'];
  private explorationRate: number;
  private minSamples: number;

  constructor(
    private config: Config,
    private messagesRepo: MessagesRepository,
    private logger: Logger,
    section: 'strategies' | 'chatStrategies' = 'strategies',
  ) {
    const cfg = config[section];
    this.variants = cfg.variants;
    this.explorationRate = cfg.explorationRate;
    this.minSamples = cfg.minSamples;
  }

  selectStrategy(): SelectedStrategy | null {
    if (this.variants.length === 0) {
      return null;
    }

    // Exploration: random strategy
    if (Math.random() < this.explorationRate) {
      const variant = this.variants[Math.floor(Math.random() * this.variants.length)];
      this.logger.debug(`Strategy selected (explore): ${variant.id}`);
      return { id: variant.id, promptOverride: variant.promptOverride, reason: 'explore' };
    }

    // Exploitation: pick the best-performing strategy
    const stats = this.messagesRepo.getStrategyStats();
    const statsMap = new Map(stats.map(s => [s.strategyId, s]));

    // Find strategies with insufficient samples - prioritize exploring them
    const unexplored = this.variants.filter(v => {
      const s = statsMap.get(v.id);
      return !s || s.totalSent < this.minSamples;
    });

    if (unexplored.length > 0) {
      const variant = unexplored[Math.floor(Math.random() * unexplored.length)];
      this.logger.debug(`Strategy selected (under-sampled): ${variant.id}`);
      return { id: variant.id, promptOverride: variant.promptOverride, reason: 'explore' };
    }

    // All strategies have enough samples - pick the best response rate
    let bestVariant = this.variants[0];
    let bestRate = -1;

    for (const variant of this.variants) {
      const s = statsMap.get(variant.id);
      if (s && s.responseRate > bestRate) {
        bestRate = s.responseRate;
        bestVariant = variant;
      }
    }

    this.logger.debug(`Strategy selected (exploit, ${bestRate}% response rate): ${bestVariant.id}`);
    return { id: bestVariant.id, promptOverride: bestVariant.promptOverride, reason: 'exploit' };
  }

  getStats(): (StrategyStats & { configured: boolean })[] {
    const dbStats = this.messagesRepo.getStrategyStats();
    const statsMap = new Map(dbStats.map(s => [s.strategyId, s]));

    // Include all configured variants, even if they have no data yet
    const results: (StrategyStats & { configured: boolean })[] = [];

    for (const variant of this.variants) {
      const s = statsMap.get(variant.id);
      results.push({
        strategyId: variant.id,
        totalSent: s?.totalSent || 0,
        totalResponses: s?.totalResponses || 0,
        responseRate: s?.responseRate || 0,
        configured: true,
      });
    }

    // Include any historical strategies no longer in config
    for (const s of dbStats) {
      if (!this.variants.some(v => v.id === s.strategyId)) {
        results.push({ ...s, configured: false });
      }
    }

    return results;
  }

  hasStrategies(): boolean {
    return this.variants.length > 0;
  }
}