package main

import (
	"encoding/json"
	"html/template"
	"log"
	"net/http"
	"os"
	"path"
	"strings"
	"sync"
	"time"
)

// ====== Datenmodelle ======

type Service struct {
	ID          string    `json:"id"`
	Name        string    `json:"name"`
	Description string    `json:"description"`
	Status      string    `json:"status"`
	LastChange  time.Time `json:"last_change"`
}

type Config struct {
	Title       string        `json:"title"`
	PollSeconds int           `json:"poll_seconds"`
	Services    []ServiceSeed `json:"services"`
}

type ServiceSeed struct {
	Name        string `json:"name"`
	Description string `json:"description"`
	Status      string `json:"status"`
	// Optional: RFC3339 (z.B. "2025-10-14T08:31:00Z")
	LastChange string `json:"last_change,omitempty"`
}

type ServicesResponse struct {
	Title       string    `json:"title"`
	PollSeconds int       `json:"poll_seconds"`
	Services    []Service `json:"services"`
	UpdatedAt   time.Time `json:"updated_at"`
}

// ====== Zustand (mit Mutex) ======

type State struct {
	mu          sync.RWMutex
	title       string
	pollSeconds int
	services    map[string]*Service
	order       []string // Beibehaltung der Anzeige-Reihenfolge
}

func newState() *State {
	return &State{
		title:       "Status-Dashboard",
		pollSeconds: 15,
		services:    make(map[string]*Service),
		order:       []string{},
	}
}

func (s *State) loadConfig(cfg *Config) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if cfg.Title != "" {
		s.title = cfg.Title
	}
	if cfg.PollSeconds > 0 {
		s.pollSeconds = cfg.PollSeconds
	}

	s.services = make(map[string]*Service)
	s.order = s.order[:0]

	idCount := map[string]int{}
	for _, seed := range cfg.Services {
		id := slugify(seed.Name)
		idCount[id]++
		if idCount[id] > 1 {
			id = id + "-" + itoa(idCount[id])
		}
		t := time.Now().UTC()
		if seed.LastChange != "" {
			if parsed, err := time.Parse(time.RFC3339, seed.LastChange); err == nil {
				t = parsed
			}
		}
		srv := &Service{
			ID:          id,
			Name:        seed.Name,
			Description: seed.Description,
			Status:      seed.Status,
			LastChange:  t,
		}
		s.services[id] = srv
		s.order = append(s.order, id)
	}
}

func (s *State) listServices() ServicesResponse {
	s.mu.RLock()
	defer s.mu.RUnlock()
	list := make([]Service, 0, len(s.order))
	for _, id := range s.order {
		if srv, ok := s.services[id]; ok {
			// Kopie (keine Zeiger nach außen)
			list = append(list, *srv)
		}
	}
	return ServicesResponse{
		Title:       s.title,
		PollSeconds: s.pollSeconds,
		Services:    list,
		UpdatedAt:   time.Now().UTC(),
	}
}

func (s *State) updateService(id string, update map[string]string) (*Service, bool) {
	s.mu.Lock()
	defer s.mu.Unlock()

	srv, ok := s.services[id]
	if !ok {
		return nil, false
	}
	changed := false

	if name, ok := update["name"]; ok && name != "" && name != srv.Name {
		srv.Name = name
		changed = true
	}
	if desc, ok := update["description"]; ok && desc != srv.Description {
		srv.Description = desc
		changed = true
	}
	if st, ok := update["status"]; ok && st != "" && st != srv.Status {
		srv.Status = st
		changed = true
	}
	// Wenn irgendein Feld geändert wurde, Zeitstempel setzen
	if changed {
		srv.LastChange = time.Now().UTC()
	}
	return srv, true
}

func (s *State) addService(seed ServiceSeed) *Service {
	s.mu.Lock()
	defer s.mu.Unlock()

	id := slugify(seed.Name)
	dup := 1
	for {
		if _, exists := s.services[id]; !exists {
			break
		}
		dup++
		id = slugify(seed.Name) + "-" + itoa(dup)
	}
	t := time.Now().UTC()
	if seed.LastChange != "" {
		if parsed, err := time.Parse(time.RFC3339, seed.LastChange); err == nil {
			t = parsed
		}
	}
	srv := &Service{
		ID:          id,
		Name:        seed.Name,
		Description: seed.Description,
		Status:      seed.Status,
		LastChange:  t,
	}
	s.services[id] = srv
	s.order = append(s.order, id)
	return srv
}

// ====== HTTP Handlers ======

func envOr(k, def string) string {
	if v := os.Getenv(k); v != "" {
		return v
	}
	return def
}

func main() {
	addr := envOr("addr", ":8080")
	cfgPath := envOr("config", "./services.json")

	state := newState()

	// Demo-Daten, falls keine Config angegeben ist
	if cfgPath == "" {
		state.loadConfig(&Config{
			Title:       "Mein Status-Dashboard",
			PollSeconds: 15,
			Services: []ServiceSeed{
				{Name: "API-Gateway", Description: "Eingangspunkt für alle Backend-APIs", Status: "Online"},
				{Name: "Datenbank", Description: "Primärer PostgreSQL-Cluster", Status: "Wartung"},
				{Name: "Benachrichtigungen", Description: "E-Mail/Push-Service", Status: "Beeinträchtigt"},
				{Name: "Website", Description: "Öffentliche Landingpage", Status: "Offline"},
			},
		})
	} else {
		cfg, err := readConfig(cfgPath)
		if err != nil {
			log.Fatalf("Konfiguration laden fehlgeschlagen: %v", err)
		}
		state.loadConfig(cfg)
	}

	// Routen
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		renderIndex(w, state)
	})

	http.HandleFunc("/static/style.css", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/css; charset=utf-8")
		http.ServeContent(w, r, "style.css", buildTime, strings.NewReader(styleCSS))
	})
	http.HandleFunc("/static/app.js", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/javascript; charset=utf-8")
		http.ServeContent(w, r, "app.js", buildTime, strings.NewReader(appJS))
	})
	http.HandleFunc("/favicon.ico", func(w http.ResponseWriter, r *http.Request) {
		http.NotFound(w, r)
	})

	// API
	http.HandleFunc("/api/services", func(w http.ResponseWriter, r *http.Request) {
		switch r.Method {
		case http.MethodGet:
			writeJSON(w, state.listServices())
		case http.MethodPost:
			// Bulk-Add: Array von ServiceSeed
			var seeds []ServiceSeed
			if err := json.NewDecoder(r.Body).Decode(&seeds); err != nil {
				http.Error(w, "invalid JSON body", http.StatusBadRequest)
				return
			}
			created := make([]*Service, 0, len(seeds))
			for _, sd := range seeds {
				if strings.TrimSpace(sd.Name) == "" {
					continue
				}
				created = append(created, state.addService(sd))
			}
			writeJSON(w, created)
		default:
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		}
	})

	http.HandleFunc("/api/service/", func(w http.ResponseWriter, r *http.Request) {
		// /api/service/{id}  (nur Update per POST)
		id := strings.TrimPrefix(r.URL.Path, "/api/service/")
		id = path.Clean("/" + id)[1:] // simple sanitize
		if id == "" {
			http.NotFound(w, r)
			return
		}
		switch r.Method {
		case http.MethodPost:
			var payload map[string]string
			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
				http.Error(w, "invalid JSON body", http.StatusBadRequest)
				return
			}
			srv, ok := state.updateService(id, payload)
			if !ok {
				http.Error(w, "service not found", http.StatusNotFound)
				return
			}
			writeJSON(w, srv)
		default:
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		}
	})

	log.Printf("🚀 Server läuft auf %s", addr)
	log.Fatal(http.ListenAndServe(addr, nil))
}

// ====== Hilfsfunktionen ======

func renderIndex(w http.ResponseWriter, st *State) {
	st.mu.RLock()
	defer st.mu.RUnlock()

	data := struct {
		Title       string
		PollSeconds int
	}{
		Title:       st.title,
		PollSeconds: st.pollSeconds,
	}

	tpl := template.Must(template.New("index").Parse(indexHTML))
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := tpl.Execute(w, data); err != nil {
		http.Error(w, "template error", http.StatusInternalServerError)
	}
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	enc := json.NewEncoder(w)
	enc.SetIndent("", "  ")
	_ = enc.Encode(v)
}

func readConfig(p string) (*Config, error) {
    b, err := os.ReadFile(p)
    if err != nil { return nil, err }
    var cfg Config
    if err := json.Unmarshal(b, &cfg); err != nil { return nil, err }
    return &cfg, nil
}

var buildTime = time.Now()

func slugify(s string) string {
	s = strings.ToLower(strings.TrimSpace(s))
	// sehr einfache Slug-Funktion
	r := make([]rune, 0, len(s))
	for _, ch := range s {
		if (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9') {
			r = append(r, ch)
		} else if ch == ' ' || ch == '-' || ch == '_' {
			if len(r) == 0 || r[len(r)-1] == '-' {
				continue
			}
			r = append(r, '-')
		}
	}
	out := strings.Trim(rmDashes(string(r)), "-")
	if out == "" {
		out = "srv"
	}
	return out
}

func rmDashes(s string) string {
	return strings.ReplaceAll(strings.ReplaceAll(s, "--", "-"), "---", "-")
}

func itoa(i int) string {
	// kleine, schnelle itoa ohne strconv
	if i == 0 {
		return "0"
	}
	var buf [32]byte
	pos := len(buf)
	for i > 0 {
		pos--
		buf[pos] = byte('0' + i%10)
		i /= 10
	}
	return string(buf[pos:])
}

// ====== Assets (lokal bereitgestellt) ======

const indexHTML = `<!doctype html>
<html lang="de">
<head>
  <meta charset="utf-8" />
  <meta name="viewport" content="width=device-width,initial-scale=1" />
  <title>{{.Title}}</title>
  <link rel="stylesheet" href="/static/style.css" />
  <script>window.AppConfig = { title: {{printf "%q" .Title}}, pollSeconds: {{.PollSeconds}} };</script>
</head>
<body>
  <header class="page-header">
    <div class="container">
      <h1 id="app-title">{{.Title}}</h1>
      <div class="header-meta">
        <span id="last-refresh" class="muted">–</span>
        <button id="refresh-btn" class="btn" aria-label="Jetzt aktualisieren">Aktualisieren</button>
      </div>
    </div>
  </header>

  <main class="container">
    <div id="filters" class="filters">
      <label class="sr-only" for="status-filter">Status-Filter</label>
      <select id="status-filter" class="select">
        <option value="">Alle Status</option>
        <option>Online</option>
        <option>Offline</option>
        <option>Wartung</option>
        <option>Beeinträchtigt</option>
        <option>Unbekannt</option>
      </select>
    </div>

    <div id="grid" class="grid" role="list"></div>
  </main>

  <footer class="container footer">
    <span class="muted">Läuft lokal · Keine externen Ressourcen</span>
  </footer>

  <script src="/static/app.js" defer></script>
</body>
</html>`

const styleCSS = `:root{
  --bg: #0b0c10;
  --bg-elev: #111218;
  --card: #14151d;
  --fg: #e6e7ea;
  --muted: #9aa0aa;
  --border: #262838;
  --shadow: 0 10px 20px rgba(0,0,0,.35);

  --green: #33d17a;
  --red: #e01b24;
  --yellow: #f5c211;
  --orange: #ff8800;
  --blue: #3b82f6;
  --gray: #6b7280;
}
@media (prefers-color-scheme: light){
  :root{
    --bg: #f6f7fb;
    --bg-elev: #fff;
    --card: #fff;
    --fg: #0f1219;
    --muted: #5e6573;
    --border: #e6e8ef;
    --shadow: 0 10px 20px rgba(0,0,0,.08);
  }
}
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  color:var(--fg);
  background:linear-gradient(180deg,var(--bg), var(--bg-elev));
  font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", Arial, "Noto Sans", "Apple Color Emoji","Segoe UI Emoji", "Noto Color Emoji", sans-serif;
}

.container{max-width:1100px;margin:0 auto;padding:0 1rem}
.page-header{
  position:sticky;top:0;z-index:10;
  backdrop-filter:saturate(120%) blur(6px);
  background: color-mix(in lab, var(--bg-elev) 70%, transparent);
  border-bottom:1px solid var(--border);
}
.page-header .container{
  display:flex;align-items:center;justify-content:space-between;gap:.75rem;padding:1rem 1rem;
}
h1{font-size:1.4rem;margin:0}
.header-meta{display:flex;align-items:center;gap:.75rem}
.muted{color:var(--muted)}

.btn{
  border:1px solid var(--border);
  background:var(--card);
  color:var(--fg);
  border-radius:12px;
  padding:.45rem .8rem;
  box-shadow:var(--shadow);
  cursor:pointer;
  transition:transform .05s ease, background .2s ease, border-color .2s ease;
}
.btn:hover{transform:translateY(-1px)}
.btn:active{transform:translateY(0)}
.select{
  border:1px solid var(--border);
  background:var(--card);
  color:var(--fg);
  border-radius:12px;
  padding:.45rem .8rem;
}
.filters{display:flex;justify-content:flex-end;padding:1rem 0}
.grid{
  display:grid;
  grid-template-columns:repeat(auto-fill, minmax(280px, 1fr));
  gap:1rem;
  padding:0 0 2rem 0;
}
.card{
  border:1px solid var(--border);
  background:var(--card);
  border-radius:16px;
  box-shadow:var(--shadow);
  padding:1rem;
  display:flex;
  flex-direction:column;
  gap:.65rem;
  transition: translate .15s ease, box-shadow .2s ease, border-color .2s ease;
}
.card:hover{translate:0 -2px}
.card-title{
  display:flex;align-items:center;justify-content:space-between;gap:.5rem;
}
.card-title h2{
  font-size:1.05rem; margin:0; line-height:1.2; font-weight:650;
}
.desc{color:var(--muted);margin:0}
.row{display:flex; align-items:center; justify-content:space-between; gap:.75rem}
.status-badge{
  font-size:.8rem;
  border-radius:999px;
  padding:.25rem .6rem;
  border:1px solid var(--border);
  background:var(--bg-elev);
  display:inline-flex; align-items:center; gap:.4rem;
}
.dot{width:.55rem;height:.55rem;border-radius:999px;display:inline-block;border:1px solid var(--border)}
.st-online .status-badge{border-color: color-mix(in srgb, var(--green) 45%, var(--border))}
.st-online .dot{background:var(--green)}
.st-offline .status-badge{border-color: color-mix(in srgb, var(--red) 45%, var(--border))}
.st-offline .dot{background:var(--red)}
.st-wartung .status-badge{border-color: color-mix(in srgb, var(--yellow) 50%, var(--border))}
.st-wartung .dot{background:var(--yellow)}
.st-beeinträchtigt .status-badge{border-color: color-mix(in srgb, var(--orange) 50%, var(--border))}
.st-beeinträchtigt .dot{background:var(--orange)}
.st-unbekannt .status-badge{border-color: color-mix(in srgb, var(--gray) 45%, var(--border))}
.st-unbekannt .dot{background:var(--gray)}

.meta{font-size:.85rem;color:var(--muted)}
.footer{padding:2rem 0 3rem 0;text-align:center}

.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}
`

const appJS = `"use strict";

(function(){
  const cfg = window.AppConfig || { title: 'Status-Dashboard', pollSeconds: 15 };
  const grid = document.getElementById('grid');
  const lastRefreshEl = document.getElementById('last-refresh');
  const btn = document.getElementById('refresh-btn');
  const filterEl = document.getElementById('status-filter');

  let timer = null;
  let cache = [];

  function statusKey(s){
    if(!s) return 'unbekannt';
    const n = s.toLowerCase();
    if(n === 'online') return 'online';
    if(n === 'offline') return 'offline';
    if(n === 'wartung' || n === 'wartend' ) return 'wartung';
    if(n === 'beeinträchtigt' || n === 'degraded') return 'beeinträchtigt';
    if(n === 'unknown' || n === 'unbekannt') return 'unbekannt';
    return n; // frei definierter Status -> eigener Key
  }

  function classForStatus(s){
    const k = statusKey(s);
    const allowed = ['online','offline','wartung','beeinträchtigt','unbekannt'];
    return 'st-' + (allowed.includes(k) ? k : 'unbekannt');
  }

  function esc(s){
    return String(s ?? '').replace(/[&<>"']/g, c => ({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'}[c]));
  }

  function timeAgo(ts){
    const d = new Date(ts);
    const now = new Date();
    const diff = (d - now) / 1000; // Sekunden (negativ, wenn in der Vergangenheit)
    const rtf = new Intl.RelativeTimeFormat('de', { numeric: 'auto' });
    const units = [
      ['year', 60*60*24*365],
      ['month', 60*60*24*30],
      ['week', 60*60*24*7],
      ['day', 60*60*24],
      ['hour', 60*60],
      ['minute', 60],
      ['second', 1],
    ];
    for(const [unit, sec] of units){
      const val = Math.round(diff / sec);
      if(Math.abs(val) >= 1){
        return rtf.format(val, unit);
      }
    }
    return 'gerade eben';
  }

  function render(services){
    const f = (filterEl.value || '').toLowerCase();
    grid.innerHTML = '';
    for(const s of services){
      if(f && statusKey(s.status) !== statusKey(f)) continue;

      const card = document.createElement('article');
      card.className = 'card ' + classForStatus(s.status);
      card.setAttribute('role','listitem');

      const title = document.createElement('div');
      title.className = 'card-title';
      const h2 = document.createElement('h2');
      h2.textContent = s.name;
      const badge = document.createElement('span');
      badge.className = 'status-badge';
      badge.innerHTML = '<span class="dot" aria-hidden="true"></span><span>'+esc(s.status || 'Unbekannt')+'</span>';
      title.appendChild(h2);
      title.appendChild(badge);

      const desc = document.createElement('p');
      desc.className = 'desc';
      desc.textContent = s.description || '—';

      const meta = document.createElement('div');
      meta.className = 'meta row';
      const lc = new Date(s.last_change);
      const timeSpan = document.createElement('span');
      timeSpan.textContent = 'Letzte Änderung: ' + timeAgo(lc.toISOString());
      timeSpan.title = lc.toLocaleString('de-DE');
      meta.appendChild(timeSpan);

      card.appendChild(title);
      card.appendChild(desc);
      card.appendChild(meta);

      grid.appendChild(card);
    }
  }

  async function fetchServices(){
    const res = await fetch('/api/services', { cache: 'no-store' });
    if(!res.ok) throw new Error('HTTP '+res.status);
    const data = await res.json();
    document.getElementById('app-title').textContent = data.title || cfg.title;
    cache = data.services || [];
    render(cache);
    const upd = new Date(data.updated_at).toLocaleTimeString('de-DE', {hour:'2-digit', minute:'2-digit', second:'2-digit'});
    lastRefreshEl.textContent = 'Zuletzt aktualisiert: '+ upd;
  }

  function startTimer(){
    clearTimer();
    const ms = Math.max(3, Number(cfg.pollSeconds || 15)) * 1000;
    timer = setInterval(fetchServices, ms);
  }
  function clearTimer(){
    if(timer){ clearInterval(timer); timer = null; }
  }

  // init
  btn.addEventListener('click', fetchServices);
  filterEl.addEventListener('change', ()=> render(cache));

  fetchServices().catch(console.error);
  startTimer();
})();
`