import { FormEvent, useEffect, useState } from "react";
import { useNavigate, useParams } from "react-router-dom";
import { apiGet, apiPost, apiPut } from "../lib/api";
import { useSession } from "../lib/session";
import type {
  ActiveCatalogSummary,
  DashboardOverview,
  QuarterKey,
  SampleDetail,
  SampleKind,
  SamplingMode,
} from "../lib/types";

const QUARTERS: { key: QuarterKey; label: string }[] = [
  { key: "LEFT_FRONT", label: "Vorne links" },
  { key: "RIGHT_FRONT", label: "Vorne rechts" },
  { key: "LEFT_REAR", label: "Hinten links" },
  { key: "RIGHT_REAR", label: "Hinten rechts" },
];

export default function SampleRegistrationPage() {
  const { sampleId } = useParams();
  const navigate = useNavigate();
  const { user } = useSession();

  const [catalogs, setCatalogs] = useState<ActiveCatalogSummary | null>(null);
  const [sampleNumber, setSampleNumber] = useState<number | null>(null);
  const [editable, setEditable] = useState(true);
  const [farmerBusinessKey, setFarmerBusinessKey] = useState("");
  const [cowNumber, setCowNumber] = useState("");
  const [cowName, setCowName] = useState("");
  const [sampleKind, setSampleKind] = useState<SampleKind>("LACTATION");
  const [samplingMode, setSamplingMode] = useState<SamplingMode>("SINGLE_SITE");
  const [flaggedQuarters, setFlaggedQuarters] = useState<QuarterKey[]>([]);
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [message, setMessage] = useState<string | null>(null);
  const [showValidation, setShowValidation] = useState(false);

  useEffect(() => {
    async function load() {
      try {
        const catalogResponse = await apiGet<ActiveCatalogSummary>("/catalogs/summary");
        setCatalogs(catalogResponse);

        if (sampleId) {
          const sample = await apiGet<SampleDetail>(`/samples/${sampleId}`);
          setSampleNumber(sample.sampleNumber);
          setEditable(sample.registrationEditable);
          setFarmerBusinessKey(sample.farmerBusinessKey);
          setCowNumber(sample.cowNumber);
          setCowName(sample.cowName ?? "");
          setSampleKind(sample.sampleKind);
          setSamplingMode(sample.samplingMode);
          setFlaggedQuarters(
            sample.quarters.filter((quarter) => quarter.flagged).map((quarter) => quarter.quarterKey),
          );
        } else {
          const dashboard = await apiGet<DashboardOverview>("/dashboard");
          setSampleNumber(dashboard.nextSampleNumber);
          setFarmerBusinessKey(catalogResponse.farmers[0]?.businessKey ?? "");
        }
      } catch (loadError) {
        setMessage((loadError as Error).message);
      } finally {
        setLoading(false);
      }
    }

    void load();
  }, [sampleId]);

  function toggleFlaggedQuarter(quarterKey: QuarterKey) {
    setFlaggedQuarters((current) =>
      current.includes(quarterKey)
        ? current.filter((entry) => entry !== quarterKey)
        : [...current, quarterKey],
    );
  }

  async function handleSubmit(event: FormEvent<HTMLFormElement>) {
    event.preventDefault();
    setShowValidation(true);
    if (!user) {
      return;
    }
    if (!farmerBusinessKey || !cowNumber.trim()) {
      setMessage("Landwirt und Kuh-Nummer sind erforderlich.");
      return;
    }

    setSaving(true);
    setMessage(null);

    const payload = {
      farmerBusinessKey,
      cowNumber,
      cowName,
      sampleKind,
      samplingMode,
      flaggedQuarters,
      userCode: user.displayName,
      userDisplayName: user.displayName,
    };

    try {
      const response = sampleId
        ? await apiPut<SampleDetail>(`/samples/${sampleId}/registration`, payload)
        : await apiPost<SampleDetail>("/samples", payload);
      navigate(`/samples/${response.id}/${response.routeSegment}`);
    } catch (saveError) {
      setMessage((saveError as Error).message);
    } finally {
      setSaving(false);
    }
  }

  if (loading) {
    return <div className="empty-state">Probe wird vorbereitet ...</div>;
  }

  return (
    <form className={`page-stack ${showValidation ? "show-validation" : ""}`} onSubmit={handleSubmit}>
      <section className="section-card section-card--hero">
        <div>
          <p className="eyebrow">Neuanlage</p>
          <h3>Probe {sampleNumber ?? "..."}</h3>
          <p className="muted-text">
            Die Probenummer wird fortlaufend vergeben. Trockensteller lassen sich ueber den
            Schalter Trockenstellerprobe markieren.
          </p>
        </div>

        {!editable ? (
          <div className="alert alert--warning">
            Diese Probe ist bereits weiter im Ablauf. Stammdaten sind nicht mehr editierbar.
          </div>
        ) : null}

        {message ? <div className="alert alert--error">{message}</div> : null}
      </section>

      <section className="form-grid form-grid--stacked">
        <article className="section-card">
          <p className="eyebrow">Stammdaten</p>
          <div className="field-grid field-grid--stacked">
            <label className="field field--required">
              <span>Landwirt</span>
              <select
                value={farmerBusinessKey}
                onChange={(event) => setFarmerBusinessKey(event.target.value)}
                disabled={!editable}
                required
              >
                {catalogs?.farmers.map((farmer) => (
                  <option key={farmer.businessKey} value={farmer.businessKey}>
                    {farmer.name}
                  </option>
                ))}
              </select>
            </label>

            <label className="field field--required">
              <span>Kuh-Nummer</span>
              <input
                value={cowNumber}
                onChange={(event) => setCowNumber(event.target.value)}
                disabled={!editable}
                required
              />
            </label>

            <label className="field">
              <span>Kuh-Name</span>
              <input
                value={cowName}
                onChange={(event) => setCowName(event.target.value)}
                disabled={!editable}
              />
            </label>
          </div>
        </article>

        <article className="section-card">
          <p className="eyebrow">Probentyp</p>
          <div className="choice-row">
            <button
              type="button"
              className={`choice-chip ${sampleKind === "LACTATION" ? "is-selected" : ""}`}
              onClick={() => setSampleKind("LACTATION")}
              disabled={!editable}
            >
              Laktationsprobe
            </button>
            <button
              type="button"
              className={`choice-chip ${sampleKind === "DRY_OFF" ? "is-selected" : ""}`}
              onClick={() => setSampleKind("DRY_OFF")}
              disabled={!editable}
            >
              Trockenstellerprobe
            </button>
          </div>

          <p className="eyebrow section-card__spacer">Entnahmestelle</p>
          <div className="choice-row">
            <button
              type="button"
              className={`choice-chip ${samplingMode === "SINGLE_SITE" ? "is-selected" : ""}`}
              onClick={() => setSamplingMode("SINGLE_SITE")}
              disabled={!editable}
            >
              Einzelprobe
            </button>
            <button
              type="button"
              className={`choice-chip ${samplingMode === "FOUR_QUARTER" ? "is-selected" : ""}`}
              onClick={() => setSamplingMode("FOUR_QUARTER")}
              disabled={!editable}
            >
              4/4 Probe
            </button>
            <button
              type="button"
              className={`choice-chip ${samplingMode === "UNKNOWN_SITE" ? "is-selected" : ""}`}
              onClick={() => setSamplingMode("UNKNOWN_SITE")}
              disabled={!editable}
            >
              Unbek.
            </button>
          </div>
        </article>
      </section>

      {samplingMode === "FOUR_QUARTER" ? (
        <section className="section-card">
          <div className="section-card__header">
            <div>
              <p className="eyebrow">Auffaellige Viertel</p>
              <h3>Viertel markieren</h3>
            </div>
          </div>

          <div className="quarter-grid">
            {QUARTERS.map((quarter) => (
              <button
                key={quarter.key}
                type="button"
                className={`quarter-tile ${flaggedQuarters.includes(quarter.key) ? "is-flagged" : ""}`}
                onClick={() => toggleFlaggedQuarter(quarter.key)}
                disabled={!editable}
              >
                <span>{quarter.label}</span>
                <strong>{flaggedQuarters.includes(quarter.key) ? "Auffällig" : "OK"}</strong>
              </button>
            ))}
          </div>
        </section>
      ) : null}

      <div className="page-actions">
        <button type="submit" className="accent-button" disabled={saving || !editable}>
          {saving ? "Speichern ..." : "Speichern"}
        </button>
      </div>
    </form>
  );
}