budgeteer/http/budgeting.go

package http

import (
	"fmt"
	"net/http"
	"strconv"
	"time"

	"git.javil.eu/jacob1123/budgeteer/postgres"
	"github.com/gin-gonic/gin"
)

type BudgetingData struct {
	AlwaysNeededData
	Categories       []CategoryWithBalance
	AvailableBalance float64
	Date             time.Time
	Next             time.Time
	Previous         time.Time
}

func getFirstOfMonth(year, month int, location *time.Location) time.Time {
	return time.Date(year, time.Month(month), 1, 0, 0, 0, 0, location)
}

func getFirstOfMonthTime(date time.Time) time.Time {
	var monthM time.Month
	year, monthM, _ := date.Date()
	month := int(monthM)
	return getFirstOfMonth(year, month, date.Location())
}

type CategoryWithBalance struct {
	*postgres.GetCategoriesRow
	Available          float64
	AvailableLastMonth float64
	Activity           float64
	Assigned           float64
}

func getDate(c *gin.Context) (time.Time, error) {
	var year, month int
	yearString := c.Param("year")
	monthString := c.Param("month")
	if yearString == "" && monthString == "" {
		return getFirstOfMonthTime(time.Now()), nil
	}

	year, err := strconv.Atoi(yearString)
	if err != nil {
		return time.Time{}, fmt.Errorf("parse year: %w", err)
	}

	month, err = strconv.Atoi(monthString)
	if err != nil {
		return time.Time{}, fmt.Errorf("parse month: %w", err)
	}

	return getFirstOfMonth(year, month, time.Now().Location()), nil
}

func (h *Handler) budgeting(c *gin.Context) {
	alwaysNeededData := c.MustGet("data").(AlwaysNeededData)
	budgetUUID := alwaysNeededData.Budget.ID

	firstOfMonth, err := getDate(c)
	if err != nil {
		c.Redirect(http.StatusTemporaryRedirect, "/budget/"+budgetUUID.String())
		return
	}

	firstOfNextMonth := firstOfMonth.AddDate(0, 1, 0)
	firstOfPreviousMonth := firstOfMonth.AddDate(0, -1, 0)
	d := BudgetingData{
		AlwaysNeededData: alwaysNeededData,
		Date:             firstOfMonth,
		Next:             firstOfNextMonth,
		Previous:         firstOfPreviousMonth,
	}

	categories, err := h.Service.DB.GetCategories(c.Request.Context(), budgetUUID)

	cumultativeBalances, err := h.Service.DB.GetCumultativeBalances(c.Request.Context(), budgetUUID)
	if err != nil {
		c.AbortWithError(http.StatusInternalServerError, fmt.Errorf("load balances: %w", err))
		return
	}

	// skip everything in the future
	categoriesWithBalance, moneyUsed, err := h.calculateBalances(c, alwaysNeededData.Budget, firstOfNextMonth, firstOfMonth, categories, cumultativeBalances)
	if err != nil {
		return
	}
	d.Categories = categoriesWithBalance

	data := c.MustGet("data").(AlwaysNeededData)
	var availableBalance float64 = 0
	for _, cat := range categories {
		if cat.ID != data.Budget.IncomeCategoryID {
			continue
		}
		availableBalance = moneyUsed

		for _, bal := range cumultativeBalances {
			if bal.CategoryID != cat.ID {
				continue
			}

			if !bal.Date.Before(firstOfNextMonth) {
				continue
			}

			availableBalance += bal.Transactions.GetFloat64()
		}
	}

	d.AvailableBalance = availableBalance

	c.HTML(http.StatusOK, "budgeting.html", d)
}

func (h *Handler) calculateBalances(c *gin.Context, budget postgres.Budget, firstOfNextMonth time.Time, firstOfMonth time.Time, categories []postgres.GetCategoriesRow, cumultativeBalances []postgres.GetCumultativeBalancesRow) ([]CategoryWithBalance, float64, error) {
	categoriesWithBalance := []CategoryWithBalance{}
	hiddenCategory := CategoryWithBalance{
		GetCategoriesRow: &postgres.GetCategoriesRow{
			Name:  "",
			Group: "Hidden Categories",
		},
	}

	var moneyUsed float64 = 0
	for i := range categories {
		cat := &categories[i]
		categoryWithBalance := CategoryWithBalance{
			GetCategoriesRow: cat,
		}
		for _, bal := range cumultativeBalances {
			if bal.CategoryID != cat.ID {
				continue
			}

			if !bal.Date.Before(firstOfNextMonth) {
				continue
			}

			moneyUsed -= bal.Assignments.GetFloat64()
			categoryWithBalance.Available += bal.Assignments.GetFloat64()
			categoryWithBalance.Available += bal.Transactions.GetFloat64()
			if categoryWithBalance.Available < 0 && bal.Date.Before(firstOfMonth) {
				moneyUsed += categoryWithBalance.Available
				categoryWithBalance.Available = 0
			}

			if bal.Date.Before(firstOfMonth) {
				categoryWithBalance.AvailableLastMonth = categoryWithBalance.Available
			} else if bal.Date.Before(firstOfNextMonth) {
				categoryWithBalance.Activity = bal.Transactions.GetFloat64()
				categoryWithBalance.Assigned = bal.Assignments.GetFloat64()
			}

		}

		// do not show hidden categories
		if cat.Group == "Hidden Categories" {
			hiddenCategory.Available += categoryWithBalance.Available
			hiddenCategory.AvailableLastMonth += categoryWithBalance.AvailableLastMonth
			hiddenCategory.Activity += categoryWithBalance.Activity
			hiddenCategory.Assigned += categoryWithBalance.Assigned
			continue
		}

		if cat.ID == budget.IncomeCategoryID {
			continue
		}

		categoriesWithBalance = append(categoriesWithBalance, categoryWithBalance)
	}

	categoriesWithBalance = append(categoriesWithBalance, hiddenCategory)

	return categoriesWithBalance, moneyUsed, nil
}