{% extends "base.html" %} {% block title %}Brewlog · Timeline{% endblock %} {% block content %}
<header class="flex flex-col gap-2">
  <h1 class="text-3xl font-semibold">Timeline</h1>
  <p class="max-w-2xl text-sm text-stone-600">
    Follow the history of roasters and roasts in Brewlog.
  </p>
</header>

<div class="mt-8">
  <section
    id="timeline-events"
    data-empty="{{ months.is_empty() }}"
  >
    {% if months.is_empty() %}
    <p
      class="rounded-lg border border-dashed border-amber-300 bg-amber-100/60 p-6 text-sm text-stone-600"
      data-role="timeline-empty-state"
    >
      No events yet.
    </p>
    {% else %}
    <div class="timeline-list relative" id="timeline-items">
      {# Single central timeline line for all months #}
      <div class="timeline-line absolute top-0 bottom-0 w-0.5 bg-amber-200" aria-hidden="true"></div>
      {% for month in months %} {% include "partials/timeline_month.html" %} {% endfor %}
    </div>
    {% endif %}

    <div
      id="timeline-loader"
      class="mt-8 flex flex-col items-center gap-3"
      data-next-url="{% if events.has_next() %}{{ navigator.fragment_page_href(events.next_page().unwrap()) }}{% else %}{% endif %}"
      data-has-more="{{ events.has_next() }}"
      data-empty="{{ months.is_empty() }}"
    >
      <button
        id="timeline-load-more"
        type="button"
        class="inline-flex items-center gap-2 rounded-full border border-amber-500 px-4 py-2 text-sm font-semibold text-amber-700 transition hover:border-amber-400 hover:text-amber-600 disabled:cursor-not-allowed disabled:border-amber-200 disabled:text-amber-300"
        style="{% if months.is_empty() || !events.has_next() %}display: none{% endif %}"
      >
        <span aria-hidden="true">↓</span>
        Load more
      </button>
      <p id="timeline-status" class="text-xs text-stone-500" hidden>Loading…</p>
      <p id="timeline-end" class="text-sm text-stone-500" style="{% if events.has_next() || months.is_empty() %}display: none{% endif %}">No more events.</p>
      <p id="timeline-error" class="text-sm text-red-600" hidden></p>
    </div>
    <div id="timeline-sentinel" class="h-1"></div>
  </section>
</div>

<script type="module">
  const loader = document.getElementById("timeline-loader")
  const itemsContainer = document.getElementById("timeline-items")
  const loadMoreButton = document.getElementById("timeline-load-more")
  const statusLine = document.getElementById("timeline-status")
  const endLine = document.getElementById("timeline-end")
  const errorLine = document.getElementById("timeline-error")
  const sentinel = document.getElementById("timeline-sentinel")
  const emptyState = document.querySelector('[data-role="timeline-empty-state"]')
  const section = document.getElementById("timeline-events")

  if (loader && sentinel) {
    let nextUrl = loader.dataset.nextUrl || ""
    let hasMorePages = loader.dataset.hasMore === "true"
    let loading = false

    const observer = new IntersectionObserver(
      (entries) => {
        if (entries.some((entry) => entry.isIntersecting) && hasMorePages && nextUrl) {
          void loadMore()
        }
      },
      { rootMargin: "200px" }
    )

    const setHasMore = (hasMore, url) => {
      hasMorePages = hasMore
      nextUrl = url || ""
      loader.dataset.hasMore = hasMore ? "true" : "false"
      loader.dataset.nextUrl = nextUrl

      if (!hasMore) {
        if (loadMoreButton) loadMoreButton.style.display = "none"
        if (endLine) endLine.style.display = ""
        observer.disconnect()
      }
    }

    const ensureItemsContainer = () => {
      if (itemsContainer) return itemsContainer
      // First load on a previously empty timeline: create the container
      const container = document.createElement("div")
      container.className = "timeline-list relative"
      container.id = "timeline-items"
      const line = document.createElement("div")
      line.className = "timeline-line absolute top-0 bottom-0 w-0.5 bg-amber-200"
      line.setAttribute("aria-hidden", "true")
      container.appendChild(line)
      section.insertBefore(container, loader)
      return container
    }

    const appendMonths = (chunk) => {
      const monthsFragment = chunk.querySelector("[data-chunk-months]")
      if (!monthsFragment) return

      const container = ensureItemsContainer()

      for (const node of Array.from(monthsFragment.children)) {
        // Skip duplicate month headings (same month spanning a page boundary)
        if (node.hasAttribute("data-timeline-month") && document.getElementById(node.id)) {
          continue
        }
        container.appendChild(node)
      }
    }

    const clearEmptyState = () => {
      if (emptyState && !emptyState.hidden) {
        emptyState.hidden = true
        loader.dataset.empty = "false"
      }
    }

    const loadMore = async () => {
      if (loading || !hasMorePages || !nextUrl) return

      loading = true
      if (statusLine) {
        statusLine.hidden = false
      }
      if (errorLine) {
        errorLine.hidden = true
      }

      try {
        const response = await fetch(nextUrl, {
          headers: {
            "X-Requested-With": "fetch",
            "datastar-request": "true",
          },
        })
        if (!response.ok) {
          throw new Error(`Unexpected response: ${response.status}`)
        }
        const html = await response.text()
        const template = document.createElement("template")
        template.innerHTML = html.trim()
        const chunk = template.content.querySelector("[data-timeline-chunk]")
        if (!chunk) {
          throw new Error("Invalid timeline chunk payload")
        }

        appendMonths(chunk)
        clearEmptyState()

        const hasMore = chunk.dataset.hasMore === "true"
        const url = chunk.dataset.nextUrl || ""
        setHasMore(hasMore, url)
      } catch (error) {
        console.error(error)
        if (errorLine) {
          errorLine.textContent = "Failed to load more events. Please try again."
          errorLine.hidden = false
        }
      } finally {
        loading = false
        if (statusLine) {
          statusLine.hidden = true
        }
      }
    }

    if (loadMoreButton) {
      loadMoreButton.addEventListener("click", () => {
        void loadMore()
      })
    }

    if (hasMorePages && loader.dataset.empty !== "true") {
      observer.observe(sentinel)
    }
  }

  // Sticky header detection - observe all current and future headings
  const stickyObserver = new IntersectionObserver(
    (entries) => {
      entries.forEach((entry) => {
        entry.target.classList.toggle("is-stuck", !entry.isIntersecting)
      })
    },
    { rootMargin: "-1px 0px 0px 0px", threshold: 1 }
  )

  // Use MutationObserver to watch for new month headings being added
  const timelineItems = document.getElementById("timeline-items")
  if (timelineItems) {
    const mutationObserver = new MutationObserver((mutations) => {
      mutations.forEach((mutation) => {
        mutation.addedNodes.forEach((node) => {
          if (node.nodeType === Node.ELEMENT_NODE) {
            const heading = node.querySelector?.(".timeline-heading")
            if (heading) {
              stickyObserver.observe(heading)
            }
          }
        })
      })
    })
    mutationObserver.observe(timelineItems, { childList: true })
  }

  // Observe existing headings
  document.querySelectorAll(".timeline-heading").forEach((heading) => {
    stickyObserver.observe(heading)
  })
</script>
{% endblock %}