import { Link } from 'react-router-dom'
import { gatePath } from '../utils/routes.js'
import { gateTitleById } from './GateSelect.jsx'

const DEPENDENCY_TYPE_LABELS = {
  requires: 'Voraussetzung',
  blocks: 'Blockiert',
  related: 'Bezug',
  parallel_group: 'Parallelgruppe',
  optional_branch: 'Optional',
}

const OUTGOING_PHRASES = {
  requires: 'benötigt',
  blocks: 'blockiert',
  related: 'Bezug zu',
}

const INCOMING_PHRASES = {
  requires: 'Voraussetzung für',
  blocks: 'Wird blockiert von',
  related: 'Bezug von',
}

function groupDependencies(itemId, dependencies) {
  /** @type {{ outgoing: typeof dependencies, incoming: typeof dependencies }} */
  const groups = { outgoing: [], incoming: [] }
  for (const dep of dependencies) {
    if (dep.from_item_id === itemId) groups.outgoing.push(dep)
    else if (dep.to_item_id === itemId) groups.incoming.push(dep)
  }
  return groups
}

function DependencyRow({ dep, itemId, siblingItems, direction, canManage, busy, onDelete }) {
  const otherId = direction === 'outgoing' ? dep.to_item_id : dep.from_item_id
  const otherTitle = gateTitleById(siblingItems, otherId) || otherId
  const phrase =
    direction === 'outgoing'
      ? OUTGOING_PHRASES[dep.dependency_type] || dep.dependency_type
      : INCOMING_PHRASES[dep.dependency_type] || dep.dependency_type

  return (
    <li className="list-item card-list-item gate-dependency-item">
      <div className="list-item-main">
        <p className="gate-dependency-item__phrase">
          {direction === 'outgoing' ? (
            <>
              Dieses Gate <strong>{phrase}</strong>{' '}
              <Link to={gatePath(otherId)}>{otherTitle}</Link>
            </>
          ) : (
            <>
              <strong>{phrase}</strong>{' '}
              <Link to={gatePath(otherId)}>{otherTitle}</Link>
            </>
          )}
        </p>
        <p className="muted list-item-sub">
          {DEPENDENCY_TYPE_LABELS[dep.dependency_type] || dep.dependency_type}
          {dep.group_key ? ` · Gruppe ${dep.group_key}` : ''}
        </p>
      </div>
      {canManage && (
        <div className="list-item-meta action-controls">
          <button
            type="button"
            className="btn btn-secondary btn-sm"
            disabled={busy}
            onClick={() => onDelete(dep.id)}
          >
            Entfernen
          </button>
        </div>
      )}
    </li>
  )
}

export function GateDependenciesSection({
  itemId,
  siblingItems = [],
  dependencies = [],
  canManage,
  busy,
  onAdd,
  onDelete,
}) {
  const candidates = siblingItems.filter((item) => item.id !== itemId)
  const { outgoing, incoming } = groupDependencies(itemId, dependencies)
  const hasAny = outgoing.length > 0 || incoming.length > 0

  async function handleAddSubmit(event) {
    event.preventDefault()
    const form = event.target
    const toItemId = form.to_item_id.value
    const dependencyType = form.dependency_type.value
    const groupKey = form.group_key?.value?.trim()
    if (!toItemId) return
    const body = {
      to_item_id: toItemId,
      dependency_type: dependencyType,
    }
    if (dependencyType === 'parallel_group') {
      if (!groupKey) return
      body.group_key = groupKey
    }
    await onAdd(body)
    form.reset()
  }

  return (
    <section className="gate-dependencies-section">
      <div className="section-header">
        <div>
          <h3>Abhängigkeiten</h3>
          <p className="section-lead muted">
            Kanten für den Gate-Graph — ausgehende Abhängigkeiten kannst du hier anlegen und
            entfernen.
          </p>
        </div>
      </div>

      {!hasAny && (
        <p className="muted gate-dependencies-section__empty">
          Noch keine Kanten — im Graph erscheinen Gates sonst nach Reihenfolge.
        </p>
      )}

      {outgoing.length > 0 && (
        <>
          <h4 className="gate-dependencies-section__group-title">Ausgehend</h4>
          <ul className="item-list gate-dependency-list">
            {outgoing.map((dep) => (
              <DependencyRow
                key={dep.id}
                dep={dep}
                itemId={itemId}
                siblingItems={siblingItems}
                direction="outgoing"
                canManage={canManage}
                busy={busy}
                onDelete={onDelete}
              />
            ))}
          </ul>
        </>
      )}

      {incoming.length > 0 && (
        <>
          <h4 className="gate-dependencies-section__group-title">Eingehend</h4>
          <ul className="item-list gate-dependency-list">
            {incoming.map((dep) => (
              <DependencyRow
                key={dep.id}
                dep={dep}
                itemId={itemId}
                siblingItems={siblingItems}
                direction="incoming"
                canManage={canManage}
                busy={busy}
                onDelete={onDelete}
              />
            ))}
          </ul>
        </>
      )}

      {canManage && candidates.length > 0 && (
        <form className="inline-form-block gate-dependency-form" onSubmit={handleAddSubmit}>
          <h4>Kante hinzufügen</h4>
          <p className="muted form-hint gate-dependency-form__hint">
            Dieses Gate …
          </p>
          <label>
            Beziehung
            <select name="dependency_type" defaultValue="requires">
              <option value="requires">benötigt (Voraussetzung)</option>
              <option value="blocks">blockiert</option>
              <option value="parallel_group">Parallelgruppe</option>
              <option value="optional_branch">optionaler Zweig</option>
              <option value="related">steht in Bezug zu</option>
            </select>
          </label>
          <label className="gate-dependency-form__group-key">
            Parallelgruppe (Schlüssel)
            <input
              name="group_key"
              maxLength={128}
              placeholder="z. B. phase-1"
            />
            <span className="muted form-hint">Nur bei Kantenart „Parallelgruppe“.</span>
          </label>
          <label>
            Anderes Gate
            <select name="to_item_id" required defaultValue="">
              <option value="" disabled>
                Gate wählen …
              </option>
              {candidates.map((item) => (
                <option key={item.id} value={item.id}>
                  {item.title}
                </option>
              ))}
            </select>
          </label>
          <button type="submit" className="btn btn-primary" disabled={busy}>
            Kante anlegen
          </button>
        </form>
      )}

      {canManage && candidates.length === 0 && (
        <p className="muted gate-dependencies-section__empty">
          Mindestens ein weiteres Gate im Vorhaben nötig, um Kanten zu definieren.
        </p>
      )}
    </section>
  )
}