import { requireSalesOrAdmin } from '~/server/utils/auth';
import { getNocoDbConfiguration, normalizePersonName } from '~/server/utils/nocodb';
import type { Expense } from '~/utils/types';

export default defineEventHandler(async (event) => {
  console.log('[EXPENSES] Find duplicate expenses request');

  try {
    // Require sales or admin access
    await requireSalesOrAdmin(event);

    const query = getQuery(event);
    const dateRange = query.dateRange as string || '30'; // Default to last 30 days
    
    // Calculate date range
    const endDate = new Date();
    const startDate = new Date();
    startDate.setDate(startDate.getDate() - parseInt(dateRange));

    // Get expenses from NocoDB
    const config = getNocoDbConfiguration();
    const expenseTableId = "mxfcefkk4dqs6uq";
    
    const response = await $fetch(`${config.url}/api/v2/tables/${expenseTableId}/records`, {
      headers: {
        'xc-token': config.token
      },
      params: {
        limit: 5000,
        where: `(Time,gte,${startDate.toISOString().split('T')[0]})~and(Time,lte,${endDate.toISOString().split('T')[0]})`,
        sort: '-Time'
      }
    }) as any;

    const expenses = response.list || [];
    console.log('[EXPENSES] Analyzing', expenses.length, 'expenses for duplicates');

    // Find duplicate groups
    const duplicateGroups = findDuplicateExpenses(expenses);
    
    // Also find payer name variations
    const payerVariations = findPayerNameVariations(expenses);

    console.log('[EXPENSES] Found', duplicateGroups.length, 'duplicate groups and', payerVariations.length, 'payer variations');

    return {
      success: true,
      data: {
        duplicateGroups,
        payerVariations,
        totalExpenses: expenses.length,
        duplicateCount: duplicateGroups.reduce((sum, group) => sum + group.expenses.length, 0),
        dateRange: {
          start: startDate.toISOString().split('T')[0],
          end: endDate.toISOString().split('T')[0]
        }
      }
    };

  } catch (error: any) {
    console.error('[EXPENSES] Failed to find duplicates:', error);
    
    if (error.statusCode === 403) {
      throw createError({
        statusCode: 403,
        statusMessage: 'Access denied. Sales or admin role required.'
      });
    }

    throw createError({
      statusCode: 500,
      statusMessage: 'Failed to find duplicate expenses'
    });
  }
});

/**
 * Find duplicate expenses based on multiple criteria
 */
function findDuplicateExpenses(expenses: any[]) {
  const duplicateGroups: Array<{
    id: string;
    expenses: any[];
    matchReason: string;
    confidence: number;
    masterCandidate: any;
  }> = [];

  const processedIds = new Set<number>();

  for (let i = 0; i < expenses.length; i++) {
    const expense1 = expenses[i];
    
    if (processedIds.has(expense1.Id)) continue;

    const matches = [expense1];
    let matchReasons = new Set<string>();
    
    for (let j = i + 1; j < expenses.length; j++) {
      const expense2 = expenses[j];
      
      if (processedIds.has(expense2.Id)) continue;

      const similarity = calculateExpenseSimilarity(expense1, expense2);
      
      if (similarity.score >= 0.8) {
        matches.push(expense2);
        processedIds.add(expense2.Id);
        similarity.reasons.forEach(r => matchReasons.add(r));
      }
    }

    if (matches.length > 1) {
      // Mark all as processed
      matches.forEach(match => processedIds.add(match.Id));

      // Determine the best master candidate
      const masterCandidate = selectMasterExpense(matches);
      
      duplicateGroups.push({
        id: `group_${duplicateGroups.length + 1}`,
        expenses: matches,
        matchReason: Array.from(matchReasons).join(', '),
        confidence: Math.max(...matches.slice(1).map(match => 
          calculateExpenseSimilarity(masterCandidate, match).score
        )),
        masterCandidate
      });
    }
  }

  return duplicateGroups;
}

/**
 * Find payer name variations (like "Abbie" vs "abbie")
 */
function findPayerNameVariations(expenses: any[]) {
  const payerMap = new Map<string, Set<string>>();
  
  // Group payers by normalized name
  expenses.forEach(expense => {
    if (expense.Payer) {
      const normalized = normalizePersonName(expense.Payer);
      if (!payerMap.has(normalized)) {
        payerMap.set(normalized, new Set());
      }
      payerMap.get(normalized)!.add(expense.Payer);
    }
  });
  
  // Find variations
  const variations: Array<{
    normalizedName: string;
    variations: string[];
    expenseCount: number;
  }> = [];
  
  payerMap.forEach((variationSet, normalized) => {
    if (variationSet.size > 1) {
      const variationArray = Array.from(variationSet);
      const expenseCount = expenses.filter(e => 
        e.Payer && normalizePersonName(e.Payer) === normalized
      ).length;
      
      variations.push({
        normalizedName: normalized,
        variations: variationArray,
        expenseCount
      });
    }
  });
  
  return variations.sort((a, b) => b.expenseCount - a.expenseCount);
}

/**
 * Calculate similarity between two expenses
 */
function calculateExpenseSimilarity(expense1: any, expense2: any) {
  const scores: Array<{ type: string; score: number; weight: number }> = [];
  const reasons: string[] = [];

  // Exact match on establishment, price, and date (highest weight for true duplicates)
  if (expense1['Establishment Name'] === expense2['Establishment Name'] &&
      expense1.Price === expense2.Price &&
      expense1.Time === expense2.Time) {
    scores.push({ type: 'exact', score: 1.0, weight: 0.5 });
    reasons.push('Exact match');
  }

  // Same payer, establishment, and price on same day (likely duplicate)
  const date1 = expense1.Time?.split('T')[0];
  const date2 = expense2.Time?.split('T')[0];
  
  if (normalizePersonName(expense1.Payer) === normalizePersonName(expense2.Payer) &&
      expense1['Establishment Name'] === expense2['Establishment Name'] &&
      expense1.Price === expense2.Price &&
      date1 === date2) {
    scores.push({ type: 'same-day', score: 0.95, weight: 0.4 });
    reasons.push('Same person, place, amount on same day');
  }

  // Similar establishment names with same price and payer
  if (expense1['Establishment Name'] && expense2['Establishment Name']) {
    const nameSimilarity = calculateStringSimilarity(
      expense1['Establishment Name'],
      expense2['Establishment Name']
    );
    
    if (nameSimilarity > 0.8 && 
        expense1.Price === expense2.Price &&
        normalizePersonName(expense1.Payer) === normalizePersonName(expense2.Payer)) {
      scores.push({ type: 'similar', score: nameSimilarity, weight: 0.3 });
      reasons.push('Similar establishment name');
    }
  }

  // Time proximity check (within 5 minutes)
  if (expense1.Time && expense2.Time) {
    const time1 = new Date(expense1.Time).getTime();
    const time2 = new Date(expense2.Time).getTime();
    const timeDiff = Math.abs(time1 - time2);
    
    if (timeDiff < 5 * 60 * 1000 && // 5 minutes
        expense1['Establishment Name'] === expense2['Establishment Name']) {
      scores.push({ type: 'time-proximity', score: 0.9, weight: 0.2 });
      reasons.push('Within 5 minutes at same establishment');
    }
  }

  // Calculate weighted average
  const totalWeight = scores.reduce((sum, s) => sum + s.weight, 0);
  const weightedScore = totalWeight > 0 
    ? scores.reduce((sum, s) => sum + (s.score * s.weight), 0) / totalWeight 
    : 0;

  return {
    score: weightedScore,
    reasons,
    details: scores
  };
}

/**
 * Calculate string similarity using Levenshtein distance
 */
function calculateStringSimilarity(str1: string, str2: string): number {
  const s1 = str1.toLowerCase().trim();
  const s2 = str2.toLowerCase().trim();
  
  if (s1 === s2) return 1.0;
  
  const distance = levenshteinDistance(s1, s2);
  const maxLength = Math.max(s1.length, s2.length);
  
  return maxLength > 0 ? 1 - (distance / maxLength) : 0;
}

/**
 * Calculate Levenshtein distance between two strings
 */
function levenshteinDistance(str1: string, str2: string): number {
  const matrix = Array(str2.length + 1).fill(null).map(() => Array(str1.length + 1).fill(null));

  for (let i = 0; i <= str1.length; i += 1) {
    matrix[0][i] = i;
  }

  for (let j = 0; j <= str2.length; j += 1) {
    matrix[j][0] = j;
  }

  for (let j = 1; j <= str2.length; j += 1) {
    for (let i = 1; i <= str1.length; i += 1) {
      const indicator = str1[i - 1] === str2[j - 1] ? 0 : 1;
      matrix[j][i] = Math.min(
        matrix[j][i - 1] + 1, // deletion
        matrix[j - 1][i] + 1, // insertion
        matrix[j - 1][i - 1] + indicator // substitution
      );
    }
  }

  return matrix[str2.length][str1.length];
}

/**
 * Select the best master expense from a group
 */
function selectMasterExpense(expenses: any[]) {
  return expenses.reduce((best, current) => {
    const bestScore = calculateExpenseCompletenessScore(best);
    const currentScore = calculateExpenseCompletenessScore(current);
    
    return currentScore > bestScore ? current : best;
  });
}

/**
 * Calculate completeness score for an expense
 */
function calculateExpenseCompletenessScore(expense: any): number {
  const fields = ['Establishment Name', 'Price', 'Payer', 'Category', 'Contents', 'Time'];
  const filledFields = fields.filter(field => 
    expense[field] && expense[field].toString().trim().length > 0
  );
  
  let score = filledFields.length / fields.length;
  
  // Bonus for having contents description
  if (expense.Contents && expense.Contents.length > 10) {
    score += 0.2;
  }
  
  // Bonus for recent creation (more likely to be accurate)
  if (expense.CreatedAt) {
    const created = new Date(expense.CreatedAt);
    const now = new Date();
    const hoursOld = (now.getTime() - created.getTime()) / (1000 * 60 * 60);
    
    if (hoursOld < 24) score += 0.1;
  }
  
  return Math.min(score, 1.0);
}