checkout/src/purchase/views/reports.py

import datetime
from io import StringIO
from zoneinfo import ZoneInfo

import numpy as np
from django.conf import settings
from django.contrib import messages
from django.utils.translation import gettext as _
from django.views.generic import TemplateView
from matplotlib import pyplot as plt
from matplotlib import ticker
from matplotlib.axes import Axes
from matplotlib.container import BarContainer
from matplotlib.dates import AutoDateLocator, ConciseDateFormatter, HourLocator
from matplotlib.figure import Figure

from purchase.models import Basket, PaymentMethod, Product, ProductQuerySet
from purchase.views.utils import ProtectedViewsMixin


class ReportsView(ProtectedViewsMixin, TemplateView):
    permission_required = ["purchase.view_basket"]
    template_name = "purchase/reports.html"

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        baskets = list(Basket.objects.priced().order_by("created_at"))
        if not baskets:
            messages.warning(self.request, _("No sale to report"))
            return context

        dates = Basket.objects.values_list("created_at__date", flat=True).distinct()
        average_basket_by_day = {
            date: Basket.objects.by_date(date).average_basket() for date in dates
        }
        turnover_by_day = {
            date: Basket.objects.by_date(date).turnover() for date in dates
        }

        products = Product.objects.with_turnover().with_sold()
        (
            products_plot,
            products_sold_pie,
            products_turnover_pie,
        ) = self.get_products_plots(products)
        by_hour_plot = self.by_hour_plot(baskets)
        context.update(
            {
                "turnover": Basket.objects.turnover(),
                "turnover_by_day": turnover_by_day,
                "average_basket": Basket.objects.average_basket(),
                "average_basket_by_day": average_basket_by_day,
                "products": products,
                "products_plot": products_plot,
                "products_sold_pie": products_sold_pie,
                "products_turnover_pie": products_turnover_pie,
                "by_hour_plot": by_hour_plot,
                "payment_methods": PaymentMethod.objects.with_turnover().with_sold(),
                "no_payment_method": Basket.objects.no_payment_method().priced(),
            }
        )
        return context

    def get_products_plots(self, products: ProductQuerySet):
        labels, sold, turnover = self.get_products_data_for_plot(products)

        x = np.arange(len(labels))
        width = 0.4
        fig: Figure = plt.figure()
        fig.suptitle(_("Sales by product"))

        color = "tab:orange"
        ax1: Axes = fig.add_subplot()
        bar: BarContainer = ax1.bar(x - width / 2, sold, width=width, color=color)
        ax1.bar_label(bar)
        ax1.tick_params(axis="x", rotation=15)
        ax1.tick_params(axis="y", labelcolor=color)
        ax1.set_xticks(x, labels)
        ax1.set_ylabel(_("# sold"), color=color)

        color = "tab:blue"
        ax2: Axes = ax1.twinx()
        bar = ax2.bar(x + width / 2, turnover, width=width, color=color)
        ax2.bar_label(bar, fmt="%d€")
        ax2.set_ylabel(_("Turnover by product"), color=color)
        ax2.yaxis.set_major_formatter(ticker.FormatStrFormatter("%.2f€"))
        ax2.tick_params(axis="y", labelcolor=color)

        fig.tight_layout()
        img1 = self.get_image_from_fig(fig)

        fig = plt.figure()
        fig.suptitle(_("# sold"))
        ax1 = fig.add_subplot()
        ax1.pie(sold, labels=labels, autopct="%d%%")
        fig.tight_layout()
        img2 = self.get_image_from_fig(fig)

        fig = plt.figure()
        fig.suptitle(_("Turnover by product"))
        ax1 = fig.add_subplot()
        ax1.pie(turnover, labels=labels, autopct="%d%%")
        fig.tight_layout()
        img3 = self.get_image_from_fig(fig)

        return img1, img2, img3

    def get_products_data_for_plot(self, products):
        labels = []
        sold = []
        turnover = []
        for product in products:
            labels.append(product.name)
            sold.append(product.sold)
            turnover.append(product.turnover / 100)
        return labels, sold, turnover

    def by_hour_plot(self, baskets):
        labels, counts, turnovers = self.get_by_hour_data_for_plot(baskets)
        hours_in_day = 24
        fig: Figure = plt.figure()
        fig.suptitle(_("Sales by hour"))
        ax1: Axes = fig.add_subplot()

        color = "tab:orange"
        ax1.bar(labels, counts, width=1 / hours_in_day, color=color)
        ax1.tick_params(axis="x", rotation=15)
        ax1.xaxis.set_minor_locator(HourLocator())
        tz = ZoneInfo(settings.TIME_ZONE)
        locator = AutoDateLocator(tz=tz)
        ax1.xaxis.set_major_locator(locator)
        ax1.xaxis.set_major_formatter(ConciseDateFormatter(locator, tz=tz))
        ax1.set_ylabel(_("Basket count by hour"), color=color)
        ax1.set_yticks(np.linspace(*ax1.get_ybound(), 8))
        ax1.tick_params(axis="y", labelcolor=color)
        ax1.grid(visible=True, which="major", axis="y")

        color = "tab:blue"
        ax2: Axes = ax1.twinx()
        ax2.plot(labels, turnovers, ".-", color=color)
        ax2.set_ylabel(_("Turnover by hour"), color=color)
        ax2.set_ylim(bottom=0)
        ax2.set_yticks(np.linspace(*ax2.get_ybound(), 8))
        ax2.tick_params(axis="y", labelcolor=color)
        ax2.yaxis.set_major_formatter(ticker.FormatStrFormatter("%.2f€"))

        fig.tight_layout()
        return self.get_image_from_fig(fig)

    def get_by_hour_data_for_plot(self, baskets):
        current: datetime.datetime = baskets[0].created_at
        current = current.replace(minute=0, second=0, microsecond=0)
        end: datetime.datetime = baskets[-1].created_at
        basket_index = 0
        labels = []
        counts = []
        turnovers = []
        while current < end:
            end_slot = current + datetime.timedelta(hours=1)
            basket = baskets[basket_index]
            count = 0
            turnover = 0
            while basket.created_at < end_slot:
                count += 1
                turnover += basket.price / 100
                basket_index += 1
                if basket_index == len(baskets):
                    break
                basket = baskets[basket_index]
            labels.append(current.astimezone(ZoneInfo(settings.TIME_ZONE)))
            counts.append(count)
            turnovers.append(turnover)
            current = end_slot
        return labels, counts, turnovers

    def get_image_from_fig(self, fig):
        image_data = StringIO()
        fig.savefig(image_data, format="svg")
        image_data.seek(0)
        img1 = image_data.getvalue()
        return img1