/**
 * AI Email Sorter Service
 * Uses Mistral AI for intelligent email categorization
 */

import { Mistral } from '@mistralai/mistralai'
import { config } from '../config/index.mjs'
import { log } from '../middleware/logger.mjs'

/**
 * Email categories with metadata
 * Uses Gmail categories where available
 * 
 * Actions:
 * - 'star': Keep in inbox + add star (VIP)
 * - 'inbox': Keep in inbox
 * - 'archive_read': Archive + mark as read (cleans inbox)
 */
const CATEGORIES = {
  vip: {
    name: 'Important',
    description: 'Important emails from known contacts',
    color: '#ff0000',
    gmailCategory: null,
    action: 'star',       // Keep in inbox + star
    priority: 1,
  },
  customers: {
    name: 'Clients',
    description: 'Emails from clients and projects',
    color: '#4285f4',
    gmailCategory: null,
    action: 'inbox',      // Keep in inbox
    priority: 2,
  },
  invoices: {
    name: 'Invoices',
    description: 'Invoices, receipts and financial documents',
    color: '#0f9d58',
    gmailCategory: null,
    action: 'inbox',      // Keep in inbox
    priority: 3,
  },
  newsletters: {
    name: 'Newsletter',
    description: 'Regular newsletters and updates',
    color: '#9c27b0',
    gmailCategory: 'CATEGORY_UPDATES',
    action: 'archive_read', // Archive + mark as read
    priority: 4,
  },
  promotions: {
    name: 'Promotions',
    description: 'Marketing emails and promotions',
    color: '#ff9800',
    gmailCategory: 'CATEGORY_PROMOTIONS',
    action: 'archive_read', // Archive + mark as read
    priority: 5,
  },
  social: {
    name: 'Social',
    description: 'Social media and platform notifications',
    color: '#00bcd4',
    gmailCategory: 'CATEGORY_SOCIAL',
    action: 'archive_read', // Archive + mark as read
    priority: 6,
  },
  security: {
    name: 'Security',
    description: 'Security codes and notifications',
    color: '#f44336',
    gmailCategory: null,
    action: 'inbox',      // Keep in inbox (important!)
    priority: 1,
  },
  calendar: {
    name: 'Calendar',
    description: 'Calendar invites and events',
    color: '#673ab7',
    gmailCategory: null,
    action: 'inbox',      // Keep in inbox
    priority: 3,
  },
  review: {
    name: 'Review',
    description: 'Emails that need manual review',
    color: '#607d8b',
    gmailCategory: null,
    action: 'inbox',      // Keep in inbox for review
    priority: 10,
  },
}

/**
 * AI Sorter Service Class
 */
export class AISorterService {
  constructor() {
    this.client = null
    this.model = 'mistral-small-latest'
    this.enabled = Boolean(config.mistral.apiKey)

    if (this.enabled) {
      this.client = new Mistral({ apiKey: config.mistral.apiKey })
      log.info('AI Sorter Service initialized with Mistral AI')
    } else {
      log.warn('AI Sorter Service disabled - no MISTRAL_API_KEY')
    }
  }

  /**
   * Get all categories
   */
  getCategories() {
    return CATEGORIES
  }

  /**
   * Get category names as array
   */
  getCategoryNames() {
    return Object.values(CATEGORIES).map(c => c.name)
  }

  /**
   * Get label name for a category key
   */
  getLabelName(key) {
    return CATEGORIES[key]?.name || CATEGORIES.review.name
  }

  /**
   * Get Gmail category ID if available
   */
  getGmailCategory(key) {
    return CATEGORIES[key]?.gmailCategory || null
  }

  /**
   * Get action for category
   */
  getCategoryAction(key) {
    return CATEGORIES[key]?.action || 'inbox'
  }

  /**
   * Get color for category
   */
  getCategoryColor(key) {
    return CATEGORIES[key]?.color || '#607d8b'
  }

  /**
   * Categorize a single email
   */
  async categorize(email, preferences = {}) {
    if (!this.enabled) {
      return { category: 'review', confidence: 0, reason: 'AI not configured' }
    }

    const { from, subject, snippet } = email

    // Build context from preferences
    const preferenceContext = this._buildPreferenceContext(preferences)

    const prompt = `You are an intelligent email sorting assistant. Analyze the following email and categorize it.

AVAILABLE CATEGORIES:
${Object.entries(CATEGORIES).map(([key, cat]) => `- ${key}: ${cat.name} - ${cat.description}`).join('\n')}

${preferenceContext}

EMAIL:
From: ${from}
Subject: ${subject}
Preview: ${snippet?.substring(0, 500) || 'No preview'}

RESPONSE FORMAT (JSON ONLY):
{"category": "category_key", "confidence": 0.0-1.0, "reason": "brief explanation"}

Respond ONLY with the JSON object.`

    try {
      const response = await this.client.chat.complete({
        model: this.model,
        messages: [{ role: 'user', content: prompt }],
        temperature: 0.1,
        maxTokens: 150,
        responseFormat: { type: 'json_object' },
      })

      const content = response.choices[0]?.message?.content
      const result = JSON.parse(content)

      // Validate category
      if (!CATEGORIES[result.category]) {
        result.category = 'review'
      }

      return result
    } catch (error) {
      log.error('AI categorization failed', { error: error.message })
      return { category: 'review', confidence: 0, reason: 'Categorization error' }
    }
  }

  /**
   * Batch categorize multiple emails
   */
  async batchCategorize(emails, preferences = {}) {
    if (!this.enabled || emails.length === 0) {
      return emails.map(e => ({
        email: e,
        classification: { category: 'review', confidence: 0, reason: 'AI not available' },
      }))
    }

    // For small batches, process individually
    if (emails.length <= 5) {
      const results = []
      for (const email of emails) {
        const classification = await this.categorize(email, preferences)
        results.push({ email, classification })
      }
      return results
    }

    // For larger batches, use batch request
    const preferenceContext = this._buildPreferenceContext(preferences)

    const emailList = emails.map((e, i) => 
      `[${i}] From: ${e.from} | Subject: ${e.subject} | Preview: ${e.snippet?.substring(0, 200) || '-'}`
    ).join('\n')

    const prompt = `You are an email sorting assistant. Categorize the following ${emails.length} emails.

CATEGORIES:
${Object.entries(CATEGORIES).map(([key, cat]) => `${key}: ${cat.name}`).join(' | ')}

${preferenceContext}

EMAILS:
${emailList}

RESPONSE FORMAT (JSON ARRAY ONLY):
[{"index": 0, "category": "key"}, {"index": 1, "category": "key"}, ...]

Respond ONLY with the JSON array.`

    try {
      const response = await this.client.chat.complete({
        model: this.model,
        messages: [{ role: 'user', content: prompt }],
        temperature: 0.1,
        maxTokens: emails.length * 50,
        responseFormat: { type: 'json_object' },
      })

      const content = response.choices[0]?.message?.content
      let parsed

      // Handle both array and object responses
      try {
        parsed = JSON.parse(content)
        if (parsed.results) parsed = parsed.results
        if (!Array.isArray(parsed)) {
          throw new Error('Not an array')
        }
      } catch {
        // Fallback to individual processing
        return this._fallbackBatch(emails, preferences)
      }

      return emails.map((email, i) => {
        const result = parsed.find(r => r.index === i)
        const category = result?.category && CATEGORIES[result.category] ? result.category : 'review'
        return {
          email,
          classification: { category, confidence: 0.8, reason: 'Batch' },
        }
      })
    } catch (error) {
      log.error('Batch categorization failed', { error: error.message })
      return this._fallbackBatch(emails, preferences)
    }
  }

  /**
   * Fallback to individual categorization
   */
  async _fallbackBatch(emails, preferences) {
    const results = []
    for (const email of emails) {
      const classification = await this.categorize(email, preferences)
      results.push({ email, classification })
      // Rate limiting pause
      await new Promise(r => setTimeout(r, 100))
    }
    return results
  }

  /**
   * Build preference context for prompt
   */
  _buildPreferenceContext(preferences) {
    const parts = []

    if (preferences.vipSenders?.length) {
      parts.push(`VIP Senders (always categorize as "vip"): ${preferences.vipSenders.join(', ')}`)
    }

    if (preferences.blockedSenders?.length) {
      parts.push(`Blocked Senders (categorize as "promotions"): ${preferences.blockedSenders.join(', ')}`)
    }

    if (preferences.customRules?.length) {
      parts.push(`Custom Rules:\n${preferences.customRules.map(r => `- ${r.condition}: ${r.category}`).join('\n')}`)
    }

    if (preferences.priorityTopics?.length) {
      parts.push(`Priority Topics (higher priority): ${preferences.priorityTopics.join(', ')}`)
    }

    return parts.length > 0 ? `USER PREFERENCES:\n${parts.join('\n')}\n` : ''
  }

  /**
   * Learn from user corrections
   */
  async learnFromCorrection(email, originalCategory, correctedCategory, userId) {
    log.info('Learning correction received', {
      from: email.from,
      original: originalCategory,
      corrected: correctedCategory,
      userId,
    })

    // In production, this would:
    // 1. Store correction in database
    // 2. Update user preferences
    // 3. Potentially fine-tune the model

    return { learned: true }
  }

  /**
   * Get category statistics
   */
  getCategoryStats(classifications) {
    const stats = {}
    for (const { classification } of classifications) {
      const cat = classification.category
      stats[cat] = (stats[cat] || 0) + 1
    }
    return stats
  }
}

// Default export
export default AISorterService