import type { UIBill } from '$lib/models/bill';
import type { CategoryStat, MonthlyStat, DailyExpenseData, TotalStats, PieChartDataItem } from '$lib/types/analysis';
import { pieColors } from '$lib/constants/chart';

/**
 * 计算分类统计
 */
export function calculateCategoryStats(records: UIBill[]): CategoryStat[] {
  const stats = new Map<string, { expense: number; income: number; count: number }>();
  
  for (const r of records) {
    if (!stats.has(r.category)) {
      stats.set(r.category, { expense: 0, income: 0, count: 0 });
    }
    const s = stats.get(r.category)!;
    s.count++;
    const amount = r.amount || 0;
    if (r.incomeExpense === '支出') {
      s.expense += amount;
    } else {
      s.income += amount;
    }
  }
  
  return [...stats.entries()]
    .map(([category, data]) => ({ category, ...data }))
    .sort((a, b) => b.expense - a.expense);
}

/**
 * 计算月度统计
 */
export function calculateMonthlyStats(records: UIBill[]): MonthlyStat[] {
  const stats = new Map<string, { expense: number; income: number }>();
  
  for (const r of records) {
    const month = r.time.substring(0, 7); // YYYY-MM
    if (!stats.has(month)) {
      stats.set(month, { expense: 0, income: 0 });
    }
    const s = stats.get(month)!;
    const amount = r.amount || 0;
    if (r.incomeExpense === '支出') {
      s.expense += amount;
    } else {
      s.income += amount;
    }
  }
  
  return [...stats.entries()]
    .map(([month, data]) => ({ month, ...data }))
    .sort((a, b) => a.month.localeCompare(b.month));
}

/**
 * 计算每日支出数据（用于面积图）
 */
export function calculateDailyExpenseData(records: UIBill[]): DailyExpenseData[] {
  const stats = new Map<string, number>();
  
  for (const r of records) {
    if (r.incomeExpense !== '支出') continue;
    const date = r.time.substring(0, 10); // YYYY-MM-DD
    const amount = r.amount || 0;
    stats.set(date, (stats.get(date) || 0) + amount);
  }
  
  return [...stats.entries()]
    .map(([date, value]) => ({ date: new Date(date), value }))
    .sort((a, b) => a.date.getTime() - b.date.getTime());
}

/**
 * 计算总计统计
 */
export function calculateTotalStats(records: UIBill[]): TotalStats {
  return {
    expense: records
      .filter(r => r.incomeExpense === '支出')
      .reduce((sum, r) => sum + (r.amount || 0), 0),
    income: records
      .filter(r => r.incomeExpense === '收入')
      .reduce((sum, r) => sum + (r.amount || 0), 0),
    count: records.length,
  };
}

/**
 * 计算百分比
 */
export function getPercentage(value: number, total: number): number {
  return total > 0 ? (value / total) * 100 : 0;
}

/**
 * 计算饼状图数据
 */
export function calculatePieChartData(
  categoryStats: CategoryStat[], 
  totalExpense: number
): PieChartDataItem[] {
  return categoryStats
    .filter(s => s.expense > 0)
    .map((stat, i) => ({
      category: stat.category,
      value: stat.expense,
      color: pieColors[i % pieColors.length],
      percentage: getPercentage(stat.expense, totalExpense)
    }));
}

/**
 * 获取 Top N 支出记录
 */
export function getTopExpenses(records: UIBill[], n: number = 10): UIBill[] {
  return records
    .filter(r => r.incomeExpense === '支出')
    .sort((a, b) => (b.amount || 0) - (a.amount || 0))
    .slice(0, n);
}

/**
 * 统计支出/收入笔数
 */
export function countByType(records: UIBill[], type: '支出' | '收入'): number {
  return records.filter(r => r.incomeExpense === type).length;
}