package httpapi

import (
	"html/template"
	"net/http"
	"net/url"
	"strings"
	"time"
)

type statusPageData struct {
	GeneratedAt    string
	RefreshSeconds int
	Filters        statusPageFilters
	QuickFilters   []statusFilterLink
	Overview       screenStatusOverview
	StatusAPIPath  string
	StatusPagePath string
}

type statusPageFilters struct {
	ServerConnectivity string
	Stale              string
	UpdatedSince       string
	Limit              string
}

type statusFilterLink struct {
	Label  string
	Href   string
	Class  string
	Active bool
}

type screenDetailPageData struct {
	GeneratedAt    string
	RefreshSeconds int
	Record         playerStatusRecord
	StatusPagePath string
}

type statusPageErrorData struct {
	Message        string
	StatusPagePath string
}

// statusPageCSS is the shared stylesheet for all status page templates.
// It is injected via string concatenation at parse time so that each template
// is self-contained and can be executed independently without template inheritance.
const statusPageCSS = `
    :root {
      color-scheme: light;
      --bg: #f4efe7;
      --surface: rgba(255, 252, 247, 0.94);
      --surface-strong: #fffdf9;
      --text: #1d2935;
      --muted: #5d6b78;
      --border: rgba(29, 41, 53, 0.12);
      --online: #2f7d4a;
      --degraded: #9a6a18;
      --offline: #a43b32;
      --shadow: 0 18px 40px rgba(63, 46, 26, 0.12);
    }

    * { box-sizing: border-box; }

    body {
      margin: 0;
      font-family: Georgia, "Times New Roman", serif;
      background:
        radial-gradient(circle at top left, rgba(191, 148, 77, 0.18), transparent 30%),
        linear-gradient(180deg, #f8f4ed 0%, var(--bg) 100%);
      color: var(--text);
    }

    .page {
      max-width: 1100px;
      margin: 0 auto;
      padding: 32px 20px 48px;
    }

    .hero,
    .panel {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 22px;
      box-shadow: var(--shadow);
      backdrop-filter: blur(8px);
    }

    .hero {
      padding: 28px;
      margin-bottom: 20px;
    }

    h1,
    h2 {
      margin: 0;
      font-weight: 600;
      letter-spacing: -0.02em;
    }

    h1 {
      font-size: clamp(2rem, 4vw, 3.2rem);
      margin-bottom: 10px;
    }

    h2 {
      font-size: 1.2rem;
      margin-bottom: 18px;
    }

    .lead,
    .meta,
    .empty,
    td small {
      color: var(--muted);
    }

    .lead {
      margin: 0;
      max-width: 46rem;
      line-height: 1.5;
    }

    .hero-top {
      display: flex;
      gap: 16px;
      justify-content: space-between;
      align-items: flex-start;
      flex-wrap: wrap;
      margin-bottom: 24px;
    }

    .hero-top .meta {
      text-align: right;
      min-width: 12rem;
      font-size: 0.95rem;
      line-height: 1.5;
    }

    .summary-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
      gap: 12px;
    }

    .summary-card {
      padding: 16px;
      border-radius: 18px;
      background: var(--surface-strong);
      border: 1px solid var(--border);
    }

    .summary-card strong {
      display: block;
      font-size: 1.8rem;
      margin-bottom: 4px;
    }

    .summary-card span {
      color: var(--muted);
      font-size: 0.95rem;
    }

    .summary-card.offline strong,
    .state.offline,
    .pill.offline { color: var(--offline); }
    .summary-card.degraded strong,
    .state.degraded,
    .pill.degraded { color: var(--degraded); }
    .summary-card.online strong,
    .state.online,
    .pill.online { color: var(--online); }

    .panel {
      padding: 24px;
    }

    .panel + .panel {
      margin-top: 18px;
    }

    .panel-head {
      display: flex;
      align-items: flex-start;
      justify-content: space-between;
      gap: 12px;
      flex-wrap: wrap;
      margin-bottom: 18px;
    }

    .panel-head h2 {
      margin-bottom: 6px;
    }

    .panel-copy {
      margin: 0;
      color: var(--muted);
      line-height: 1.5;
    }

    .meta-chip,
    .filter-link,
    .json-link,
    .text-link {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      border-radius: 999px;
      border: 1px solid var(--border);
      padding: 6px 12px;
      color: inherit;
      text-decoration: none;
      background: rgba(255, 255, 255, 0.65);
    }

    .meta-chip {
      color: var(--muted);
      font-size: 0.9rem;
    }

    .controls-grid {
      display: grid;
      grid-template-columns: minmax(0, 1.5fr) minmax(0, 1fr);
      gap: 18px;
    }

    .quick-filters {
      display: flex;
      gap: 10px;
      flex-wrap: wrap;
      align-items: flex-start;
    }

    .filter-link.active {
      border-color: rgba(29, 41, 53, 0.28);
      background: var(--surface-strong);
      color: var(--text);
      box-shadow: inset 0 0 0 1px rgba(29, 41, 53, 0.05);
    }

    .filter-link.offline.active { color: var(--offline); }
    .filter-link.degraded.active { color: var(--degraded); }
    .filter-link.online.active { color: var(--online); }

    .filter-form {
      display: grid;
      grid-template-columns: repeat(2, minmax(0, 1fr));
      gap: 12px;
    }

    .field {
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .field label {
      color: var(--muted);
      font-size: 0.82rem;
      text-transform: uppercase;
      letter-spacing: 0.08em;
    }

    .field input,
    .field select {
      width: 100%;
      border-radius: 12px;
      border: 1px solid var(--border);
      background: var(--surface-strong);
      color: var(--text);
      padding: 10px 12px;
      font: inherit;
    }

    .field.full {
      grid-column: 1 / -1;
    }

    .form-actions {
      display: flex;
      gap: 10px;
      flex-wrap: wrap;
      align-items: center;
      grid-column: 1 / -1;
      padding-top: 4px;
    }

    button {
      border: 0;
      border-radius: 999px;
      padding: 10px 16px;
      background: var(--text);
      color: #fffdf9;
      font: inherit;
      cursor: pointer;
    }

    .json-link,
    .text-link {
      color: var(--muted);
      font-size: 0.9rem;
    }

    .table-actions {
      margin-bottom: 16px;
      display: flex;
      gap: 10px;
      flex-wrap: wrap;
      align-items: center;
    }

    .table-wrap {
      overflow-x: auto;
    }

    table {
      width: 100%;
      border-collapse: collapse;
      min-width: 720px;
    }

    th,
    td {
      padding: 14px 0;
      border-bottom: 1px solid var(--border);
      text-align: left;
      vertical-align: top;
    }

    th {
      color: var(--muted);
      font-size: 0.82rem;
      text-transform: uppercase;
      letter-spacing: 0.08em;
    }

    tbody tr:last-child td {
      border-bottom: 0;
    }

    .screen {
      font-weight: 600;
      margin-bottom: 4px;
    }

    .screen-links {
      display: flex;
      gap: 8px;
      flex-wrap: wrap;
      margin-top: 10px;
    }

    .pill {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      border-radius: 999px;
      border: 1px solid currentColor;
      padding: 4px 10px;
      font-size: 0.84rem;
      text-transform: capitalize;
      background: rgba(255, 255, 255, 0.5);
    }

    .empty {
      padding: 10px 0 4px;
      line-height: 1.5;
    }

    /* Key-value detail tables used on the screen detail page. */
    .detail-table {
      min-width: 0;
    }

    .detail-table th {
      font-weight: normal;
      white-space: nowrap;
      padding-right: 24px;
      width: 40%;
    }

    .detail-table tbody tr:last-child th,
    .detail-table tbody tr:last-child td {
      border-bottom: 0;
    }

    @media (max-width: 720px) {
      .page {
        padding: 20px 14px 32px;
      }

      .hero,
      .panel {
        border-radius: 18px;
      }

      .hero {
        padding: 22px;
      }

      .panel {
        padding: 18px;
      }

      .hero-top .meta {
        text-align: left;
      }

      .controls-grid,
      .filter-form {
        grid-template-columns: 1fr;
      }

      .detail-table th {
        width: auto;
      }
    }
`

// statusPageCSSBlock wraps statusPageCSS in a <style> element.
// Each template embeds it via string concatenation so that no template
// inheritance is needed and every page is independently executable.
const statusPageCSSBlock = `  <style>` + statusPageCSS + `  </style>`

var statusTemplateFuncs = template.FuncMap{
	"connectivityLabel":    connectivityLabel,
	"screenDetailPath":     screenDetailPath,
	"screenDetailHTMLPath": screenDetailHTMLPath,
	"statusClass":          statusClass,
	"timestampLabel":       timestampLabel,
}

var statusPageTemplate = template.Must(template.New("status-page").Funcs(statusTemplateFuncs).Parse(`<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <meta http-equiv="refresh" content="{{.RefreshSeconds}}">
  <title>Screen Status</title>
` + statusPageCSSBlock + `
</head>
<body>
  <main class="page">
    <section class="hero">
      <div class="hero-top">
        <div>
          <h1>Screen Status</h1>
          <p class="lead">A compact browser view of the latest screen reports from the current in-memory status overview. Offline and degraded screens stay at the top for quick diagnostics.</p>
        </div>
        <div class="meta">
          <div>{{.Overview.Summary.Total}} screens</div>
          <div>Updated {{.GeneratedAt}}</div>
        </div>
      </div>

      <div class="summary-grid">
        <article class="summary-card">
          <strong>{{.Overview.Summary.Total}}</strong>
          <span>Total known screens</span>
        </article>
        <article class="summary-card offline">
          <strong>{{.Overview.Summary.Offline}}</strong>
          <span>Offline</span>
        </article>
        <article class="summary-card degraded">
          <strong>{{.Overview.Summary.Degraded}}</strong>
          <span>Degraded</span>
        </article>
        <article class="summary-card online">
          <strong>{{.Overview.Summary.Online}}</strong>
          <span>Online</span>
        </article>
        <article class="summary-card">
          <strong>{{.Overview.Summary.Stale}}</strong>
          <span>Stale reports</span>
        </article>
      </div>
    </section>

    <section class="panel">
      <div class="panel-head">
        <div>
          <h2>Filters and refresh</h2>
          <p class="panel-copy">This page refreshes every {{.RefreshSeconds}} seconds. Use the shortcut links or the form to narrow the existing connectivity and freshness filters without leaving the lightweight server-rendered flow.</p>
        </div>
        <a class="meta-chip" href="{{.StatusAPIPath}}">JSON overview</a>
      </div>

      <div class="controls-grid">
        <div>
          <h2>Quick views</h2>
          <div class="quick-filters">
            {{range .QuickFilters}}
            <a class="filter-link {{.Class}} {{if .Active}}active{{end}}" href="{{.Href}}">{{.Label}}</a>
            {{end}}
          </div>
        </div>

        <form class="filter-form" method="get" action="{{.StatusPagePath}}">
          <div class="field">
            <label for="server_connectivity">Server connectivity</label>
            <select id="server_connectivity" name="server_connectivity">
              <option value="" {{if eq .Filters.ServerConnectivity ""}}selected{{end}}>Any</option>
              <option value="online" {{if eq .Filters.ServerConnectivity "online"}}selected{{end}}>Online</option>
              <option value="degraded" {{if eq .Filters.ServerConnectivity "degraded"}}selected{{end}}>Degraded</option>
              <option value="offline" {{if eq .Filters.ServerConnectivity "offline"}}selected{{end}}>Offline</option>
              <option value="unknown" {{if eq .Filters.ServerConnectivity "unknown"}}selected{{end}}>Unknown</option>
            </select>
          </div>

          <div class="field">
            <label for="stale">Freshness</label>
            <select id="stale" name="stale">
              <option value="" {{if eq .Filters.Stale ""}}selected{{end}}>Any</option>
              <option value="true" {{if eq .Filters.Stale "true"}}selected{{end}}>Stale only</option>
              <option value="false" {{if eq .Filters.Stale "false"}}selected{{end}}>Fresh only</option>
            </select>
          </div>

          <div class="field full">
            <label for="updated_since">Updated since (RFC3339)</label>
            <input id="updated_since" name="updated_since" type="text" placeholder="2026-03-22T16:05:00Z" value="{{.Filters.UpdatedSince}}">
          </div>

          <div class="field">
            <label for="limit">Limit</label>
            <input id="limit" name="limit" type="number" min="1" inputmode="numeric" value="{{.Filters.Limit}}">
          </div>

          <div class="form-actions">
            <button type="submit">Apply filters</button>
            <a class="text-link" href="{{.StatusPagePath}}">Clear</a>
          </div>
        </form>
      </div>
    </section>

    <section class="panel">
      <div class="panel-head">
        <div>
          <h2>Latest reports</h2>
          <p class="panel-copy">Each row links to the HTML detail view and the raw JSON endpoint for a quick drill-down.</p>
        </div>
      </div>
      <div class="table-actions">
        <a class="text-link" href="{{.StatusAPIPath}}">Open filtered JSON overview</a>
      </div>
      {{if .Overview.Screens}}
      <div class="table-wrap">
        <table>
          <thead>
            <tr>
              <th>Screen</th>
              <th>Derived state</th>
              <th>Player status</th>
              <th>Server link</th>
              <th>Received</th>
              <th>Heartbeat</th>
            </tr>
          </thead>
          <tbody>
            {{range .Overview.Screens}}
            <tr>
              <td>
                <div class="screen">{{.ScreenID}}</div>
                {{if .MQTTBroker}}<small>{{.MQTTBroker}}</small>{{else if .ServerURL}}<small>{{.ServerURL}}</small>{{else}}<small>No endpoint details</small>{{end}}
                <div class="screen-links">
                  <a class="filter-link" href="{{screenDetailHTMLPath .ScreenID}}">Details</a>
                  <a class="json-link" href="{{screenDetailPath .ScreenID}}">JSON</a>
                </div>
              </td>
              <td><span class="pill {{statusClass .DerivedState}}">{{.DerivedState}}</span></td>
              <td>
                <div>{{.Status}}</div>
                {{if .Stale}}<small>Marked stale by server freshness check</small>{{else}}<small>Fresh within expected heartbeat window</small>{{end}}
              </td>
              <td>
                <span class="state {{statusClass .ServerConnectivity}}">{{connectivityLabel .ServerConnectivity}}</span>
                {{if .ServerURL}}<small>{{.ServerURL}}</small>{{end}}
              </td>
              <td>
                <div>{{timestampLabel .ReceivedAt}}</div>
                {{if .LastHeartbeatAt}}<small>Heartbeat {{timestampLabel .LastHeartbeatAt}}</small>{{end}}
              </td>
              <td>
                {{if gt .HeartbeatEverySeconds 0}}{{.HeartbeatEverySeconds}}s{{else}}-{{end}}
                {{if .StartedAt}}<small>Started {{timestampLabel .StartedAt}}</small>{{end}}
              </td>
            </tr>
            {{end}}
          </tbody>
        </table>
      </div>
      {{else}}
      <p class="empty">No screen has reported status yet. Once a player posts to the existing status API, it will appear here automatically.</p>
      {{end}}
    </section>
  </main>
</body>
</html>
`))

var screenDetailTemplate = template.Must(template.New("screen-detail").Funcs(statusTemplateFuncs).Parse(`<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <meta http-equiv="refresh" content="{{.RefreshSeconds}}">
  <title>{{.Record.ScreenID}} – Screen Status</title>
` + statusPageCSSBlock + `
</head>
<body>
  <main class="page">
    <section class="hero">
      <div class="hero-top">
        <div>
          <h1>{{.Record.ScreenID}}</h1>
          <p class="lead">Single screen diagnostic view based on the last accepted status report.</p>
        </div>
        <div class="meta">
          <div>Updated {{.GeneratedAt}}</div>
          <div style="margin-top: 8px; display: flex; gap: 8px; flex-wrap: wrap; justify-content: flex-end;">
            <a class="meta-chip" href="{{.StatusPagePath}}">← All screens</a>
            <a class="meta-chip" href="{{screenDetailPath .Record.ScreenID}}">JSON</a>
          </div>
        </div>
      </div>

      <div class="summary-grid">
        <article class="summary-card {{statusClass .Record.DerivedState}}">
          <strong><span class="state {{statusClass .Record.DerivedState}}">{{.Record.DerivedState}}</span></strong>
          <span>Derived state</span>
        </article>
        <article class="summary-card">
          <strong>{{.Record.Status}}</strong>
          <span>Player status</span>
        </article>
        <article class="summary-card {{statusClass .Record.ServerConnectivity}}">
          <strong>{{connectivityLabel .Record.ServerConnectivity}}</strong>
          <span>Server connectivity</span>
        </article>
        <article class="summary-card">
          <strong>{{if .Record.Stale}}stale{{else}}fresh{{end}}</strong>
          <span>Freshness</span>
        </article>
      </div>
    </section>

    <section class="panel">
      <div class="panel-head">
        <div>
          <h2>Timing</h2>
          <p class="panel-copy">Timestamps reported by the player and annotated by the server at receive time.</p>
        </div>
      </div>
      <table class="detail-table">
        <tbody>
          <tr>
            <th>Received at (server)</th>
            <td>{{timestampLabel .Record.ReceivedAt}}</td>
          </tr>
          <tr>
            <th>Player timestamp</th>
            <td>{{timestampLabel .Record.Timestamp}}</td>
          </tr>
          <tr>
            <th>Started at</th>
            <td>{{timestampLabel .Record.StartedAt}}</td>
          </tr>
          <tr>
            <th>Last heartbeat at</th>
            <td>{{timestampLabel .Record.LastHeartbeatAt}}</td>
          </tr>
          <tr>
            <th>Heartbeat interval</th>
            <td>{{if gt .Record.HeartbeatEverySeconds 0}}{{.Record.HeartbeatEverySeconds}}s{{else}}-{{end}}</td>
          </tr>
        </tbody>
      </table>
    </section>

    <section class="panel">
      <div class="panel-head">
        <div>
          <h2>Endpoints</h2>
          <p class="panel-copy">Connection details reported by the player in the last accepted status.</p>
        </div>
      </div>
      <table class="detail-table">
        <tbody>
          <tr>
            <th>Server URL</th>
            <td>{{if .Record.ServerURL}}{{.Record.ServerURL}}{{else}}-{{end}}</td>
          </tr>
          <tr>
            <th>MQTT broker</th>
            <td>{{if .Record.MQTTBroker}}{{.Record.MQTTBroker}}{{else}}-{{end}}</td>
          </tr>
        </tbody>
      </table>
    </section>
  </main>
</body>
</html>
`))

var statusPageErrorTemplate = template.Must(template.New("status-error").Funcs(statusTemplateFuncs).Parse(`<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Invalid filter – Screen Status</title>
` + statusPageCSSBlock + `
</head>
<body>
  <main class="page" style="max-width: 640px;">
    <section class="hero">
      <div class="hero-top">
        <div>
          <h1>Invalid filter</h1>
          <p class="lead">{{.Message}}</p>
        </div>
      </div>
      <a class="filter-link" href="{{.StatusPagePath}}">← Back to Screen Status</a>
    </section>
  </main>
</body>
</html>
`))

func handleStatusPage(store playerStatusStore) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		overview, err := buildScreenStatusOverview(store, r.URL.Query())
		if err != nil {
			writeStatusPageQueryError(w, err)
			return
		}

		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.WriteHeader(http.StatusOK)

		data := buildStatusPageData(store, r.URL.Query(), overview)

		if err := statusPageTemplate.Execute(w, data); err != nil {
			http.Error(w, "failed to render status page", http.StatusInternalServerError)
		}
	}
}

func handleScreenDetailPage(store playerStatusStore) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		screenID := strings.TrimSpace(r.PathValue("screenId"))

		record, ok := store.Get(screenID)
		if !ok {
			data := statusPageErrorData{
				Message:        "Fuer diesen Screen liegt noch kein Status vor.",
				StatusPagePath: "/status",
			}
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			w.WriteHeader(http.StatusNotFound)
			_ = statusPageErrorTemplate.Execute(w, data)
			return
		}

		record.Stale = isStale(record, store.Now())
		record.DerivedState = deriveState(record)

		data := screenDetailPageData{
			GeneratedAt:    store.Now().Format(time.RFC3339),
			RefreshSeconds: 15,
			Record:         record,
			StatusPagePath: "/status",
		}

		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		w.WriteHeader(http.StatusOK)

		if err := screenDetailTemplate.Execute(w, data); err != nil {
			http.Error(w, "failed to render detail page", http.StatusInternalServerError)
		}
	}
}

func buildStatusPageData(store playerStatusStore, query url.Values, overview screenStatusOverview) statusPageData {
	filters := statusPageFilters{
		ServerConnectivity: strings.TrimSpace(query.Get("server_connectivity")),
		Stale:              strings.TrimSpace(query.Get("stale")),
		UpdatedSince:       strings.TrimSpace(query.Get("updated_since")),
		Limit:              strings.TrimSpace(query.Get("limit")),
	}

	return statusPageData{
		GeneratedAt:    store.Now().Format(time.RFC3339),
		RefreshSeconds: 15,
		Filters:        filters,
		QuickFilters:   buildStatusQuickFilters(filters),
		Overview:       overview,
		StatusAPIPath:  buildOverviewPath("/api/v1/screens/status", filters),
		StatusPagePath: "/status",
	}
}

func buildStatusQuickFilters(filters statusPageFilters) []statusFilterLink {
	return []statusFilterLink{
		{
			Label:  "All screens",
			Href:   buildStatusPageHref(statusPageFilters{Limit: filters.Limit, UpdatedSince: filters.UpdatedSince}),
			Class:  "",
			Active: filters.ServerConnectivity == "" && filters.Stale == "",
		},
		{
			Label:  "Connectivity offline",
			Href:   buildStatusPageHref(statusPageFilters{ServerConnectivity: "offline", Limit: filters.Limit, UpdatedSince: filters.UpdatedSince}),
			Class:  "offline",
			Active: filters.ServerConnectivity == "offline" && filters.Stale == "",
		},
		{
			Label:  "Connectivity degraded",
			Href:   buildStatusPageHref(statusPageFilters{ServerConnectivity: "degraded", Limit: filters.Limit, UpdatedSince: filters.UpdatedSince}),
			Class:  "degraded",
			Active: filters.ServerConnectivity == "degraded" && filters.Stale == "",
		},
		{
			Label:  "Stale reports",
			Href:   buildStatusPageHref(statusPageFilters{Stale: "true", Limit: filters.Limit, UpdatedSince: filters.UpdatedSince}),
			Class:  "",
			Active: filters.ServerConnectivity == "" && filters.Stale == "true",
		},
		{
			Label:  "Fresh reports",
			Href:   buildStatusPageHref(statusPageFilters{Stale: "false", Limit: filters.Limit, UpdatedSince: filters.UpdatedSince}),
			Class:  "online",
			Active: filters.ServerConnectivity == "" && filters.Stale == "false",
		},
	}
}

func buildStatusPageHref(filters statusPageFilters) string {
	return buildOverviewPath("/status", filters)
}

func buildOverviewPath(basePath string, filters statusPageFilters) string {
	query := url.Values{}
	if filters.ServerConnectivity != "" {
		query.Set("server_connectivity", filters.ServerConnectivity)
	}
	if filters.Stale != "" {
		query.Set("stale", filters.Stale)
	}
	if filters.UpdatedSince != "" {
		query.Set("updated_since", filters.UpdatedSince)
	}
	if filters.Limit != "" {
		query.Set("limit", filters.Limit)
	}
	encoded := query.Encode()
	if encoded == "" {
		return basePath
	}
	return basePath + "?" + encoded
}

// writeStatusPageQueryError renders an HTML 400 error page for invalid query
// parameters on /status. This keeps the error in the same visual context as
// the rest of the status UI instead of returning a raw JSON blob in a browser.
func writeStatusPageQueryError(w http.ResponseWriter, queryErr error) {
	data := statusPageErrorData{
		Message:        overviewQueryErrorMessage(queryErr),
		StatusPagePath: "/status",
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(http.StatusBadRequest)
	if err := statusPageErrorTemplate.Execute(w, data); err != nil {
		http.Error(w, data.Message, http.StatusBadRequest)
	}
}

func statusClass(value string) string {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return "degraded"
	}
	return trimmed
}

func connectivityLabel(value string) string {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return "unknown"
	}
	return trimmed
}

func screenDetailPath(screenID string) string {
	return "/api/v1/screens/" + url.PathEscape(strings.TrimSpace(screenID)) + "/status"
}

func screenDetailHTMLPath(screenID string) string {
	return "/status/" + url.PathEscape(strings.TrimSpace(screenID))
}

func timestampLabel(value string) string {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return "-"
	}
	return trimmed
}