{% extends "admin/base_site.html" %}
{% load i18n static %}

{% block title %}{% translate "Public site traffic" %}{% endblock %}

{% block extrahead %}
  {{ block.super }}
  <script src="{% static 'core/vendor/chart.umd.min.js' %}" data-chartjs="true"></script>
  <style>
    #viewhistory-graph-module {
      background: var(--body-bg);
      padding: 24px;
      margin-bottom: 24px;
      border: 1px solid var(--hairline-color);
      border-radius: 6px;
    }
    #viewhistory-chart {
      max-width: 100%;
    }
    #viewhistory-empty {
      margin-top: 16px;
    }
  </style>
{% endblock %}

{% block content %}
<div id="content-main">
  <div id="viewhistory-graph-module" class="module">
    <h1>{% translate "Public site traffic" %}</h1>
    <p class="help">{% translate "Daily visits for the most frequently viewed public pages over the last 30 days." %}</p>
    <p><a class="button" href="{% url 'admin:pages_viewhistory_changelist' %}">{% translate "Back to entries" %}</a></p>
    <p id="viewhistory-meta" class="quiet"></p>
    <canvas id="viewhistory-chart" role="img" aria-label="{% translate 'Line chart showing visit counts per day' %}" height="360"></canvas>
    <p id="viewhistory-empty" class="quiet" hidden>{% translate "No visit data is available yet." %}</p>
  </div>
</div>
{% endblock %}

{% block extrahead_bottom %}{% endblock %}

{% block extrajs %}
  {{ block.super }}
  <script>
    document.addEventListener('DOMContentLoaded', () => {
      const canvas = document.getElementById('viewhistory-chart');
      if (!canvas) {
        return;
      }
      const metaLabel = document.getElementById('viewhistory-meta');
      const emptyLabel = document.getElementById('viewhistory-empty');
      const chartJsUrl = '{% static "core/vendor/chart.umd.min.js" %}';

      const waitForChart = (resolve) => {
        if (window.Chart) {
          resolve(window.Chart);
          return true;
        }
        return false;
      };

      const ensureChartJs = () => {
        const existing = document.querySelector('script[data-chartjs]');
        if (existing) {
          if (existing.dataset.chartjsState === 'error') {
            return Promise.resolve(null);
          }

          if (existing.dataset.chartjsState !== 'loaded') {
            return new Promise((resolve) => {
              existing.addEventListener(
                'load',
                () => {
                  existing.dataset.chartjsState = 'loaded';
                  resolve(window.Chart || null);
                },
                { once: true },
              );
              existing.addEventListener(
                'error',
                () => {
                  existing.dataset.chartjsState = 'error';
                  resolve(null);
                },
                { once: true },
              );
            });
          }

          return Promise.resolve(window.Chart || null);
        }

        return new Promise((resolve) => {
          const script = document.createElement('script');
          script.src = chartJsUrl;
          script.async = true;
          script.dataset.chartjs = 'true';
          script.dataset.chartjsState = 'loading';
          script.addEventListener(
            'load',
            () => {
              script.dataset.chartjsState = 'loaded';
              resolve(window.Chart || null);
            },
            { once: true },
          );
          script.addEventListener(
            'error',
            () => {
              script.dataset.chartjsState = 'error';
              resolve(null);
            },
            { once: true },
          );
          document.head.appendChild(script);
        });
      };

      const chartEndpoint = new URL('{{ chart_endpoint }}', window.location);

      const fetchData = () =>
        fetch(chartEndpoint.toString(), {
          headers: { Accept: 'application/json' },
          credentials: 'same-origin',
        }).then((response) => (response.ok ? response.json() : Promise.reject()));

      ensureChartJs()
        .then((Chart) => {
          if (!Chart && !waitForChart(() => {})) {
            throw new Error('Chart.js unavailable');
          }
          return fetchData().then((data) => ({ Chart: window.Chart, data }));
        })
        .then(({ Chart, data }) => {
          if (!data || !Array.isArray(data.labels) || !Array.isArray(data.datasets)) {
            throw new Error('Invalid chart data');
          }
          if (!data.datasets.length) {
            canvas.hidden = true;
            emptyLabel.hidden = false;
            return;
          }
          if (data.meta && metaLabel) {
            const start = data.meta.start || '';
            const end = data.meta.end || '';
            const pages = Array.isArray(data.meta.pages) ? data.meta.pages : [];
            const summary = [];
            if (start && end) {
              summary.push(`{% translate "Range" %}: ${start} – ${end}`);
            }
            if (pages.length) {
              summary.push(`{% translate "Pages" %}: ${pages.join(', ')}`);
            }
            metaLabel.textContent = summary.join(' \u2022 ');
          }
          emptyLabel.hidden = true;
          const context = canvas.getContext('2d');
          new Chart(context, {
            type: 'line',
            data: {
              labels: data.labels,
              datasets: data.datasets.map((dataset) => ({
                ...dataset,
                pointRadius: 3,
                pointHoverRadius: 5,
              })),
            },
            options: {
              responsive: true,
              maintainAspectRatio: false,
              scales: {
                x: {
                  title: {
                    display: true,
                    text: '{% translate "Date" %}',
                  },
                },
                y: {
                  beginAtZero: true,
                  title: {
                    display: true,
                    text: '{% translate "Visits" %}',
                  },
                },
              },
              plugins: {
                legend: {
                  position: 'bottom',
                },
                tooltip: {
                  mode: 'nearest',
                  intersect: false,
                },
              },
            },
          });
        })
        .catch(() => {
          canvas.hidden = true;
          emptyLabel.hidden = false;
          if (emptyLabel) {
            emptyLabel.textContent = '{% translate "Unable to load visit data at this time." %}';
          }
        });
    });
  </script>
{% endblock %}