packages/server/src/providers/pool.ts

import type { AIProvider } from '../services/aiService.js';
import type { ParsedTransaction } from '@icc/shared';
import pino from 'pino';

const logger = pino({ level: 'info' });

interface ProviderSlot {
  provider: AIProvider;
  cooldownUntil: number; // timestamp ms
  dailyRequests: number;
  dailyLimit: number;
  disabled: boolean;
}

function sleep(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

export class AIProviderPool {
  private slots: ProviderSlot[];
  private currentIndex = 0;

  constructor(providers: { provider: AIProvider; dailyLimit: number }[]) {
    this.slots = providers.map(({ provider, dailyLimit }) => ({
      provider,
      cooldownUntil: 0,
      dailyRequests: 0,
      dailyLimit,
      disabled: false,
    }));
  }

  getCurrentSlotId(): string {
    return this.slots[this.currentIndex]?.provider.name ?? 'none';
  }

  getStatus() {
    return this.slots.map((slot) => ({
      name: slot.provider.name,
      available: !slot.disabled && Date.now() >= slot.cooldownUntil && slot.dailyRequests < slot.dailyLimit,
      dailyRequests: slot.dailyRequests,
      dailyLimit: slot.dailyLimit,
      cooldownRemaining: Math.max(0, slot.cooldownUntil - Date.now()),
    }));
  }

  private findAvailableSlot(): ProviderSlot | null {
    const now = Date.now();

    // Always start from slot 0 (primary provider) to enforce priority ordering
    for (let i = 0; i < this.slots.length; i++) {
      const slot = this.slots[i];
      if (!slot.disabled && now >= slot.cooldownUntil && slot.dailyRequests < slot.dailyLimit) {
        this.currentIndex = i;
        return slot;
      }
    }

    return null;
  }

  async parse(emailBody: string): Promise<ParsedTransaction> {
    const maxRetries = this.slots.length * 3;

    for (let attempt = 0; attempt < maxRetries; attempt++) {
      const slot = this.findAvailableSlot();

      if (!slot) {
        // All slots exhausted — find the shortest cooldown and wait
        const now = Date.now();
        const soonest = this.slots
          .filter((s) => !s.disabled && s.dailyRequests < s.dailyLimit)
          .reduce((min, s) => Math.min(min, s.cooldownUntil), Infinity);

        if (soonest === Infinity) {
          throw new Error('All AI providers exhausted for the day');
        }

        const waitMs = Math.max(soonest - now, 1000);
        logger.warn(`All providers rate-limited. Waiting ${Math.round(waitMs / 1000)}s...`);
        await sleep(waitMs);
        continue;
      }

      try {
        logger.info(`Parsing with ${slot.provider.name} (attempt ${attempt + 1}/${maxRetries})`);
        const result = await slot.provider.parse(emailBody);
        slot.dailyRequests++;
        return result;
      } catch (error: any) {
        if (error.status === 429 || error.status === 413) {
          // Rate limited or request too large — set cooldown and try next
          const retryAfter = parseInt(error.headers?.['retry-after'] || '30');
          slot.cooldownUntil = Date.now() + retryAfter * 1000;
          logger.info(
            `${error.status === 413 ? 'Request too large' : 'Rate limited'} on ${slot.provider.name}, cooldown ${retryAfter}s. Switching...`
          );
          this.currentIndex = (this.currentIndex + 1) % this.slots.length;
          continue;
        }

        if (error.status === 400) {
          // 400 errors: invalid model, json_validate_failed, bad request
          const bodyStr = error.body ?? error.message ?? '';
          const isInvalidModel = bodyStr.includes('invalid_model') || bodyStr.includes('Invalid model');
          if (isInvalidModel) {
            slot.disabled = true;
            logger.warn(`Invalid model on ${slot.provider.name}, permanently disabled`);
          } else {
            // Cooldown to prevent retry loop (findAvailableSlot starts from 0)
            slot.cooldownUntil = Date.now() + 30_000;
            logger.warn(`400 error on ${slot.provider.name}, 30s cooldown. Trying next...`);
          }
          this.currentIndex = (this.currentIndex + 1) % this.slots.length;
          continue;
        }

        if (error.status === 403) {
          // 403: model blocked at org level or forbidden — permanently disable
          slot.disabled = true;
          logger.warn(`Forbidden (403) on ${slot.provider.name}, permanently disabled. Trying next...`);
          this.currentIndex = (this.currentIndex + 1) % this.slots.length;
          continue;
        }

        if (error.status === 404) {
          // 404: model does not exist on this provider — permanently disable the slot
          slot.disabled = true;
          logger.warn(`Model not found (404) on ${slot.provider.name}, permanently disabled. Trying next...`);
          this.currentIndex = (this.currentIndex + 1) % this.slots.length;
          continue;
        }

        if (error.status >= 500) {
          // Server error — 1 min cooldown
          slot.cooldownUntil = Date.now() + 60_000;
          logger.warn(`Server error on ${slot.provider.name}, 60s cooldown`);
          this.currentIndex = (this.currentIndex + 1) % this.slots.length;
          continue;
        }

        // Any other error (JSON parse, network, etc.) — cooldown and try next
        slot.cooldownUntil = Date.now() + 10_000;
        logger.warn(`Unexpected error on ${slot.provider.name}: ${error.message || error.status}. Trying next...`);
        this.currentIndex = (this.currentIndex + 1) % this.slots.length;
        continue;
      }
    }

    throw new Error('Max retries exceeded across all providers');
  }

  /** Reset daily counters (call at midnight UTC) */
  resetDaily() {
    for (const slot of this.slots) {
      slot.dailyRequests = 0;
      slot.disabled = false;
      slot.cooldownUntil = 0;
    }
  }
}