import { useEffect, useState } from "preact/hooks";

type Promotion = { id: string; annee: string | null };
type Student = { numEtud: number; idPromo: string };

function parsePromo(id: string) {
  const m = id.match(/^(\d+A)(FISE|FISA)(.+)$/);
  if (!m) return { annee: id, filiere: "?", anneeSco: "?" };
  return { annee: m[1], filiere: m[2], anneeSco: m[3] };
}

const ANNEES = ["3A", "4A", "5A"];
const FILIERES = ["FISE", "FISA"];

export default function AdminPromotions() {
  const [promos, setPromos] = useState<Promotion[]>([]);
  const [students, setStudents] = useState<Student[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [creating, setCreating] = useState(false);

  // PromoBuilder state
  const [selectedAnnee, setSelectedAnnee] = useState("4A");
  const [selectedFiliere, setSelectedFiliere] = useState("FISE");
  const [anneeSco, setAnneeSco] = useState("");

  const generatedId = anneeSco.trim()
    ? `${selectedAnnee}${selectedFiliere}${anneeSco.trim()}`
    : "";

  async function load() {
    try {
      const [pRes, sRes] = await Promise.all([
        fetch("/students/api/promotions"),
        fetch("/students/api/students"),
      ]);
      if (!pRes.ok) throw new Error("Impossible de charger les promotions");
      setPromos(await pRes.json());
      if (sRes.ok) setStudents(await sRes.json());
    } catch (e) {
      setError(e instanceof Error ? e.message : "Erreur");
    } finally {
      setLoading(false);
    }
  }

  useEffect(() => {
    load();
  }, []);

  async function createPromo() {
    if (!generatedId) return;
    setCreating(true);
    try {
      const res = await fetch("/students/api/promotions", {
        method: "POST",
        headers: { "content-type": "application/json" },
        body: JSON.stringify({
          idPromo: generatedId,
          annee: selectedAnnee,
        }),
      });
      if (!res.ok) {
        const body = await res.json().catch(() => ({}));
        throw new Error(body.error ?? "Création échouée");
      }
      setAnneeSco("");
      await load();
    } catch (e) {
      setError(e instanceof Error ? e.message : "Erreur");
    } finally {
      setCreating(false);
    }
  }

  async function deletePromo(id: string) {
    if (!confirm(`Supprimer la promotion ${id} ?`)) return;
    try {
      const res = await fetch(
        `/students/api/promotions/${encodeURIComponent(id)}`,
        { method: "DELETE" },
      );
      if (!res.ok) throw new Error("Suppression échouée");
      await load();
    } catch (e) {
      setError(e instanceof Error ? e.message : "Erreur");
    }
  }

  function studentCount(idPromo: string) {
    return students.filter((s) => s.idPromo === idPromo).length;
  }

  return (
    <div class="page-content">
      <h2 class="page-title">Gestion des Promotions</h2>

      {error && <p class="state-error">{error}</p>}

      {/* PromoBuilder */}
      <div class="promo-builder">
        <p class="promo-builder-title">Créer une promotion</p>
        <p class="promo-builder-subtitle">
          POST /promotions – idPromo est généré automatiquement
        </p>

        <div class="promo-builder-row">
          <div class="promo-builder-field">
            <label>Année</label>
            <div class="pill-group">
              {ANNEES.map((a) => (
                <button
                  key={a}
                  type="button"
                  class={`pill-btn${selectedAnnee === a ? " active" : ""}`}
                  onClick={() => setSelectedAnnee(a)}
                >
                  {a}
                </button>
              ))}
            </div>
          </div>

          <div class="promo-builder-field">
            <label>Filière</label>
            <div class="pill-group">
              {FILIERES.map((f) => (
                <button
                  key={f}
                  type="button"
                  class={`pill-btn${selectedFiliere === f ? " active" : ""}`}
                  onClick={() => setSelectedFiliere(f)}
                >
                  {f}
                </button>
              ))}
            </div>
          </div>

          <div class="promo-builder-field">
            <label>Année scolaire</label>
            <input
              class="form-input"
              placeholder="ex: 25/26, 24/27…"
              value={anneeSco}
              onInput={(e) => setAnneeSco((e.target as HTMLInputElement).value)}
              style="min-width: 9rem"
            />
          </div>
        </div>

        <div style="display: flex; align-items: center; gap: 1rem; flex-wrap: wrap">
          <div style="display: flex; align-items: center; gap: 0.5rem">
            <span style="font-size: 0.78rem; color: light-dark(var(--light-foreground-dim), var(--dark-foreground-dim))">
              idPromo généré :
            </span>
            <span class="promo-id-preview">
              {generatedId || "—"}
            </span>
          </div>
          <button
            type="button"
            class="btn btn-primary"
            onClick={createPromo}
            disabled={creating || !generatedId}
          >
            {creating ? "…" : "+ Créer la promo"}
          </button>
        </div>
      </div>

      {/* Existing promotions table */}
      <p style="font-size: 0.82rem; font-weight: var(--font-weight-bold); margin-bottom: 0.5rem">
        Promotions existantes
      </p>

      {loading
        ? <p class="state-loading">Chargement…</p>
        : (
          <div class="data-table-wrap">
            <table class="data-table">
              <thead>
                <tr>
                  <th>idPromo</th>
                  <th>Année</th>
                  <th>Filière</th>
                  <th>Année sco.</th>
                  <th>Nb étudiants</th>
                  <th>Actions</th>
                </tr>
              </thead>
              <tbody>
                {promos.length === 0
                  ? (
                    <tr>
                      <td colspan={6} class="state-empty">
                        Aucune promotion enregistrée
                      </td>
                    </tr>
                  )
                  : promos.map((p) => {
                    const parsed = parsePromo(p.id);
                    const count = studentCount(p.id);
                    return (
                      <tr key={p.id}>
                        <td>
                          <span class="promo-chip">{p.id}</span>
                        </td>
                        <td>{parsed.annee}</td>
                        <td>
                          <span class="filiere-chip">{parsed.filiere}</span>
                        </td>
                        <td>{parsed.anneeSco}</td>
                        <td class="col-dim">
                          {count} étudiant{count !== 1 ? "s" : ""}
                        </td>
                        <td>
                          <button
                            type="button"
                            class="btn btn-sm btn-danger"
                            onClick={() => deletePromo(p.id)}
                          >
                            🗑
                          </button>
                        </td>
                      </tr>
                    );
                  })}
              </tbody>
            </table>
          </div>
        )}
    </div>
  );
}