EmailBill/Service/Budget/BudgetSavingsService.cs

namespace Service.Budget;

public interface IBudgetSavingsService
{
    Task<BudgetResult> GetSavingsDtoAsync(
        BudgetPeriodType periodType,
        DateTime? referenceDate = null,
        IEnumerable<BudgetRecord>? existingBudgets = null);
}

public class BudgetSavingsService(
    IBudgetRepository budgetRepository,
    IBudgetArchiveRepository budgetArchiveRepository
) : IBudgetSavingsService
{
    public async Task<BudgetResult> GetSavingsDtoAsync(
        BudgetPeriodType periodType,
        DateTime? referenceDate = null,
        IEnumerable<BudgetRecord>? existingBudgets = null)
    {
        var budgets = existingBudgets;

        if (existingBudgets == null)
        {
            budgets = await budgetRepository.GetAllAsync();
        }

        if (budgets == null)
        {
            throw new InvalidOperationException("No budgets found.");
        }

        budgets = budgets
        // 排序顺序 1.硬性预算 2.月度->年度 3.实际金额倒叙
            .OrderBy(b => b.IsMandatoryExpense)
            .ThenBy(b => b.Type)
            .ThenByDescending(b => b.Limit);

        var year = referenceDate?.Year ?? DateTime.Now.Year;
        var month = referenceDate?.Month ?? DateTime.Now.Month;
        
        if(periodType == BudgetPeriodType.Month)
        {
            return await GetForMonthAsync(budgets, year, month);  
        }
        else if(periodType == BudgetPeriodType.Year)
        {
            return await GetForYearAsync(budgets, year);
        }

        throw new NotSupportedException($"Period type {periodType} is not supported.");
    }

    private async Task<BudgetResult> GetForMonthAsync(
        IEnumerable<BudgetRecord> budgets,
        int year, 
        int month)
    {
        var result = new BudgetResult
        {
            
        };

        var monthlyBudgets = budgets
            .Where(b => b.Type == BudgetPeriodType.Month);
        var yearlyBudgets = budgets
            .Where(b => b.Type == BudgetPeriodType.Year);

        // var actualAmount = await budgetRepository.GetCurrentAmountAsync(budget, startDate, endDate);

        throw new NotImplementedException();
    }

    private async Task<BudgetResult> GetForYearAsync(
        IEnumerable<BudgetRecord> budgets,
        int year)
    {
        throw new NotImplementedException();
    }
}