// packages/server/src/services/aiService.ts
//
// AI-powered email parsing with auto-switcher failover
// Uses Groq (primary) and Mistral (fallback) free tier APIs
//
// Install: npm install zod

import { z } from 'zod';
import type { InteracTransactionInput } from '../../shared/types/transaction';

// ═══════════════════════════════════════════
// ZOD VALIDATION SCHEMA
// ═══════════════════════════════════════════

const TransactionSchema = z.object({
  sender: z.string().min(1),
  amount: z.number().positive(),
  currency: z.string().default('CAD'),
  reference: z.string().nullable().default(null),
  message: z.string().nullable().default(null),
  recipient_email: z.string().email().nullable().default(null),
  date: z.string(),
  status: z.enum(['deposited', 'pending', 'expired', 'cancelled']).default('deposited'),
});

// ═══════════════════════════════════════════
// AI PROMPT TEMPLATE
// ═══════════════════════════════════════════

const SYSTEM_PROMPT = `You are a financial data extraction assistant. Given the raw text/HTML of an Interac e-Transfer notification email from notify@payments.interac.ca, extract the following fields into a JSON object:

- sender: The name of the person who sent the money
- amount: The dollar amount (numeric, no $ sign)
- currency: Always "CAD"
- reference: The Interac reference number
- message: The personal message or memo (sometimes called "dime" in French)
- recipient_email: The email address the transfer was sent TO (the ICC branch email)
- date: The date/time of the transfer in ISO 8601 format
- status: One of "deposited", "pending", "expired", "cancelled"

Rules:
- If a field is not found, set it to null.
- The amount must be a number (e.g., 150.00 not "$150.00").
- Return ONLY valid JSON, no markdown, no explanation, no backticks.`;

function buildUserPrompt(emailBody: string): string {
  return `Email content:\n"""\n${emailBody}\n"""`;
}

// ═══════════════════════════════════════════
// PROVIDER ADAPTERS
// ═══════════════════════════════════════════

interface AIProvider {
  name: string;
  model: string;
  call(systemPrompt: string, userPrompt: string): Promise<string>;
}

/** Groq provider — OpenAI-compatible API */
class GroqProvider implements AIProvider {
  name = 'groq';
  model: string;
  private apiKey: string;
  private baseUrl = 'https://api.groq.com/openai/v1/chat/completions';

  constructor(model = 'llama-3.3-70b-versatile', apiKey?: string) {
    this.model = model;
    this.apiKey = apiKey || process.env.GROQ_API_KEY || '';
    if (!this.apiKey) console.warn('[AI] GROQ_API_KEY not set');
  }

  async call(systemPrompt: string, userPrompt: string): Promise<string> {
    const response = await fetch(this.baseUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${this.apiKey}`,
      },
      body: JSON.stringify({
        model: this.model,
        messages: [
          { role: 'system', content: systemPrompt },
          { role: 'user', content: userPrompt },
        ],
        temperature: 0.1,
        max_tokens: 500,
        response_format: { type: 'json_object' },
      }),
    });

    if (!response.ok) {
      const errorBody = await response.text();
      if (response.status === 429) {
        throw new RateLimitError(`Groq rate limited: ${errorBody}`);
      }
      throw new Error(`Groq API error ${response.status}: ${errorBody}`);
    }

    const data = await response.json();
    return data.choices[0]?.message?.content || '';
  }
}

/** Mistral provider — OpenAI-compatible API */
class MistralProvider implements AIProvider {
  name = 'mistral';
  model: string;
  private apiKey: string;
  private baseUrl = 'https://api.mistral.ai/v1/chat/completions';

  constructor(model = 'mistral-small-latest', apiKey?: string) {
    this.model = model;
    this.apiKey = apiKey || process.env.MISTRAL_API_KEY || '';
    if (!this.apiKey) console.warn('[AI] MISTRAL_API_KEY not set');
  }

  async call(systemPrompt: string, userPrompt: string): Promise<string> {
    const response = await fetch(this.baseUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${this.apiKey}`,
      },
      body: JSON.stringify({
        model: this.model,
        messages: [
          { role: 'system', content: systemPrompt },
          { role: 'user', content: userPrompt },
        ],
        temperature: 0.1,
        max_tokens: 500,
        response_format: { type: 'json_object' },
      }),
    });

    if (!response.ok) {
      const errorBody = await response.text();
      if (response.status === 429) {
        throw new RateLimitError(`Mistral rate limited: ${errorBody}`);
      }
      throw new Error(`Mistral API error ${response.status}: ${errorBody}`);
    }

    const data = await response.json();
    return data.choices[0]?.message?.content || '';
  }
}

// ═══════════════════════════════════════════
// RATE LIMIT ERROR
// ═══════════════════════════════════════════

class RateLimitError extends Error {
  constructor(message: string) {
    super(message);
    this.name = 'RateLimitError';
  }
}

// ═══════════════════════════════════════════
// AUTO-SWITCHER POOL
// ═══════════════════════════════════════════

interface ProviderSlotRuntime {
  provider: AIProvider;
  priority: number;
  enabled: boolean;
  status: 'available' | 'rate_limited' | 'error';
  cooldownUntil?: Date;
  requestsUsed: number;
  successCount: number;
  errorCount: number;
}

export class AIProviderPool {
  private slots: ProviderSlotRuntime[] = [];
  private currentSlotIndex = 0;
  private onSwitch?: (from: string, to: string, reason: string) => void;

  constructor(onSwitch?: (from: string, to: string, reason: string) => void) {
    this.onSwitch = onSwitch;
    this.initializeSlots();
  }

  private initializeSlots() {
    // Priority order: Groq first (faster), Mistral fallback
    const groqKey = process.env.GROQ_API_KEY;
    const mistralKey = process.env.MISTRAL_API_KEY;

    if (groqKey) {
      this.slots.push({
        provider: new GroqProvider('llama-3.3-70b-versatile', groqKey),
        priority: 1,
        enabled: true,
        status: 'available',
        requestsUsed: 0,
        successCount: 0,
        errorCount: 0,
      });
      // Add secondary Groq model
      this.slots.push({
        provider: new GroqProvider('llama-3.1-8b-instant', groqKey),
        priority: 3,
        enabled: true,
        status: 'available',
        requestsUsed: 0,
        successCount: 0,
        errorCount: 0,
      });
    }

    if (mistralKey) {
      this.slots.push({
        provider: new MistralProvider('mistral-small-latest', mistralKey),
        priority: 2,
        enabled: true,
        status: 'available',
        requestsUsed: 0,
        successCount: 0,
        errorCount: 0,
      });
    }

    if (this.slots.length === 0) {
      throw new Error(
        'No AI providers configured. Set GROQ_API_KEY and/or MISTRAL_API_KEY in your .env file.'
      );
    }

    // Sort by priority
    this.slots.sort((a, b) => a.priority - b.priority);
    console.log(`[AI Pool] Initialized with ${this.slots.length} provider slots:`);
    this.slots.forEach((s, i) => {
      console.log(`  [${i}] ${s.provider.name}/${s.provider.model} (priority ${s.priority})`);
    });
  }

  /** Get the next available provider slot, skipping rate-limited ones */
  private getAvailableSlot(): ProviderSlotRuntime | null {
    const now = new Date();

    // First, check if any rate-limited slots have recovered
    for (const slot of this.slots) {
      if (slot.status === 'rate_limited' && slot.cooldownUntil && slot.cooldownUntil <= now) {
        slot.status = 'available';
        slot.cooldownUntil = undefined;
        console.log(`[AI Pool] ${slot.provider.name}/${slot.provider.model} recovered from rate limit`);
      }
    }

    // Find the highest-priority available slot
    for (const slot of this.slots) {
      if (slot.enabled && slot.status === 'available') {
        return slot;
      }
    }

    return null; // All slots exhausted
  }

  /** Parse a single email body using the AI pool with auto-failover */
  async parseEmail(emailBody: string): Promise<InteracTransactionInput> {
    const userPrompt = buildUserPrompt(emailBody);
    let lastError: Error | null = null;

    // Try each available slot
    for (let attempt = 0; attempt < this.slots.length * 2; attempt++) {
      const slot = this.getAvailableSlot();
      if (!slot) {
        // All slots exhausted — wait 10s and retry once
        console.warn('[AI Pool] All providers rate-limited. Waiting 10s...');
        await new Promise((r) => setTimeout(r, 10000));
        const retrySlot = this.getAvailableSlot();
        if (!retrySlot) {
          throw new Error('All AI providers are rate-limited or unavailable. Try again later.');
        }
        return this._callSlot(retrySlot, userPrompt);
      }

      try {
        return await this._callSlot(slot, userPrompt);
      } catch (error: any) {
        lastError = error;

        if (error instanceof RateLimitError) {
          // Mark slot as rate-limited with 60s cooldown
          const previousName = `${slot.provider.name}/${slot.provider.model}`;
          slot.status = 'rate_limited';
          slot.cooldownUntil = new Date(Date.now() + 60_000);
          slot.errorCount++;

          // Find next slot for the switch event
          const nextSlot = this.getAvailableSlot();
          if (nextSlot && this.onSwitch) {
            this.onSwitch(
              previousName,
              `${nextSlot.provider.name}/${nextSlot.provider.model}`,
              'Rate limit hit'
            );
          }

          console.warn(`[AI Pool] ${previousName} rate-limited, switching...`);
          continue; // Try next slot
        }

        // Non-rate-limit error — mark slot but still try fallback
        slot.errorCount++;
        slot.status = 'error';
        slot.cooldownUntil = new Date(Date.now() + 30_000);
        console.error(`[AI Pool] ${slot.provider.name}/${slot.provider.model} error:`, error.message);
        continue;
      }
    }

    throw lastError || new Error('All AI providers failed');
  }

  /** Internal: call a specific slot and parse the response */
  private async _callSlot(
    slot: ProviderSlotRuntime,
    userPrompt: string
  ): Promise<InteracTransactionInput> {
    const rawResponse = await slot.provider.call(SYSTEM_PROMPT, userPrompt);
    slot.requestsUsed++;
    slot.successCount++;

    // Clean potential markdown fences
    const cleaned = rawResponse
      .replace(/```json\s*/g, '')
      .replace(/```\s*/g, '')
      .trim();

    // Parse and validate
    const parsed = JSON.parse(cleaned);
    const validated = TransactionSchema.parse(parsed);
    return validated as InteracTransactionInput;
  }

  /** Get current pool status for the UI */
  getStatus() {
    return this.slots.map((s) => ({
      name: s.provider.name,
      model: s.provider.model,
      priority: s.priority,
      status: s.status,
      enabled: s.enabled,
      requestsUsed: s.requestsUsed,
      successCount: s.successCount,
      errorCount: s.errorCount,
      cooldownUntil: s.cooldownUntil?.toISOString(),
    }));
  }

  getCurrentProvider(): string {
    const slot = this.getAvailableSlot();
    return slot ? `${slot.provider.name}/${slot.provider.model}` : 'none';
  }
}

export default AIProviderPool;