"use strict";

/**
 * Entry point for the night photography data visualization app.
 * Coordinates fetching data, initializing chart & gallery, and handling filters.
 */

(async () => {
  window.addEventListener('load', initApp);

  /**
   * Initializes the application by fetching data and rendering UI components.
   * @returns {Promise<void>}
   */
  async function initApp() {
    const mainContainer = document.querySelector('main');
    if (!mainContainer) return;

    try {
      const response = await fetch('/data');
      if (!response.ok) throw new Error(`HTTP Error ${response.status}`);
      const data = await response.json();

      const { temperatures = [], images = [] } = data;
      renderSummary(temperatures, images);
      renderChart(temperatures);
      renderGallery(images);

      const filterControls = document.querySelector('.filter-controls');
      if (filterControls) {
        filterControls.addEventListener('input', handleFilterChange.bind(null, temperatures, images));
      }
    } catch (err) {
      console.error('App initialization failed:', err);
      showError(mainContainer, 'Fehler beim Laden der Daten.');
    }
  }

  /**
   * Handles changes in filter controls.
   * @param {Array} temperatures
   * @param {Array} images
   * @param {Event} evt
   */
  function handleFilterChange(temperatures, images, evt) {
    const filterContainer = evt.currentTarget;
    if (!filterContainer) return;

    const timeRange = filterContainer.querySelector('[name="timeRange"]')?.value || '';
    const minTemp = parseFloat(filterContainer.querySelector('[name="minTemp"]')?.value) || null;
    const maxTemp = parseFloat(filterContainer.querySelector('[name="maxTemp"]')?.value) || null;

    const filteredTemps = temperatures.filter(t => {
      const valueOk = (!minTemp || t.value >= minTemp) && (!maxTemp || t.value <= maxTemp);
      return valueOk;
    });

    const filteredImages = images.filter(i => {
      const relatedTemp = temperatures.find(t => t.timestamp === i.timestamp);
      if (!relatedTemp) return true;
      return (!minTemp || relatedTemp.value >= minTemp) && (!maxTemp || relatedTemp.value <= maxTemp);
    });

    renderChart(filteredTemps);
    renderGallery(filteredImages);
    renderSummary(filteredTemps, filteredImages);
  }

  /**
   * Renders a simple line chart (placeholder logic – to be replaced by visualization module if available).
   * @param {Array<{timestamp:string,value:number}>} temps
   */
  function renderChart(temps) {
    const chart = document.querySelector('#temperature-chart');
    if (!chart) return;
    chart.innerHTML = '';

    const avg = temps.reduce((acc, t) => acc + t.value, 0) / (temps.length || 1);

    const list = document.createElement('ul');
    list.className = 'chart__list';
    temps.forEach(t => {
      const li = document.createElement('li');
      li.textContent = `${new Date(t.timestamp).toLocaleTimeString()} – ${t.value.toFixed(1)}°C`;
      list.appendChild(li);
    });

    const avgDisplay = document.createElement('p');
    avgDisplay.className = 'chart__avg';
    avgDisplay.textContent = `Durchschnitt: ${avg.toFixed(1)}°C`;

    chart.appendChild(list);
    chart.appendChild(avgDisplay);
  }

  /**
   * Renders an image gallery.
   * @param {Array<{filename:string,timestamp:string,metadata:object}>} images
   */
  function renderGallery(images) {
    const gallery = document.querySelector('#image-gallery');
    if (!gallery) return;
    gallery.innerHTML = '';

    images.forEach(img => {
      const imgEl = document.createElement('div');
      imgEl.className = 'gallery__image-placeholder';
      imgEl.setAttribute('aria-label', `Bild aufgenommen um ${new Date(img.timestamp).toLocaleString()}`);
      imgEl.textContent = `[Bild: ${img.filename}]`;
      gallery.appendChild(imgEl);
    });

    const count = document.createElement('p');
    count.className = 'gallery__count';
    count.textContent = `Anzahl Bilder: ${images.length}`;
    gallery.appendChild(count);
  }

  /**
   * Render a quick summary of available data.
   * @param {Array} temps
   * @param {Array} images
   */
  function renderSummary(temps, images) {
    const summary = document.querySelector('#data-summary');
    if (!summary) return;

    const avgTemp = temps.reduce((acc, t) => acc + t.value, 0) / (temps.length || 1);
    summary.textContent = `Durchschnittstemperatur: ${avgTemp.toFixed(1)}°C | Bilder: ${images.length}`;
  }

  /**
   * Shows an error message in a container.
   * @param {HTMLElement} container
   * @param {string} msg
   */
  function showError(container, msg) {
    container.innerHTML = '';
    const p = document.createElement('p');
    p.className = 'error';
    p.textContent = msg;
    container.appendChild(p);
  }
})();