import { useEffect, useState } from 'react'
import { Link } from 'react-router-dom'
import { getInitiativeExecutionGraphState } from '../api/executionPlan.js'
import { LoadingState } from './LoadingState.jsx'
import { ErrorState } from './ErrorState.jsx'
import { EmptyState } from './EmptyState.jsx'
import { StatusBadge } from './StatusBadge.jsx'
import { ExecutionFlowBadge } from './ExecutionFlowBadge.jsx'
import {
  buildCriticalPathSteps,
  summarizeCriticalPath,
} from '../utils/executionGraph.js'
import { actionPath, scopedPath } from '../utils/routes.js'

export function CriticalPathPanel({
  initiativeId,
  actions = [],
  graphState: kernelGraphState = null,
  graphLoading = false,
  scopeRoadmapItemId = null,
  embedded = true,
}) {
  const useKernelGraph = kernelGraphState != null || graphLoading
  const [fallbackGraphState, setFallbackGraphState] = useState(null)
  const [fallbackLoading, setFallbackLoading] = useState(!useKernelGraph)
  const [error, setError] = useState(null)

  useEffect(() => {
    if (!initiativeId || useKernelGraph) {
      setFallbackGraphState(null)
      setFallbackLoading(false)
      return undefined
    }
    let cancelled = false
    setFallbackLoading(true)
    setError(null)
    getInitiativeExecutionGraphState(initiativeId, {
      scopeRoadmapItemId: scopeRoadmapItemId || undefined,
    })
      .then((data) => {
        if (!cancelled) setFallbackGraphState(data)
      })
      .catch((err) => {
        if (!cancelled) setError(err.message)
      })
      .finally(() => {
        if (!cancelled) setFallbackLoading(false)
      })
    return () => {
      cancelled = true
    }
  }, [initiativeId, scopeRoadmapItemId, useKernelGraph])

  const graphState = useKernelGraph ? kernelGraphState : fallbackGraphState
  const loading = useKernelGraph ? graphLoading : fallbackLoading

  const steps = buildCriticalPathSteps(graphState, actions)
  const summary = summarizeCriticalPath(graphState, actions)

  const body = (
    <>
      {loading && <LoadingState message="Lade kritischer Pfad …" />}
      {!loading && error && (
        <ErrorState message={error} onRetry={() => window.location.reload()} />
      )}
      {!loading && !error && steps.length === 0 && (
        <EmptyState message="Noch kein kritischer Pfad im aktiven Gate-Horizont — Arbeitspakete mit Abhängigkeiten unter Plan → Zielzustände / Durchführungsplan anlegen." />
      )}
      {!loading && !error && steps.length > 0 && (
        <>
          <p className="critical-path-summary muted">{summary.message}</p>
          <ol className="critical-path-steps item-list">
            {steps.map((step) => (
              <li
                key={step.actionId}
                className={
                  'list-item card-list-item critical-path-step' +
                  (step.isNextReady ? ' critical-path-step--next' : '') +
                  (step.status === 'done' ? ' critical-path-step--done' : '')
                }
              >
                <span className="critical-path-step__index muted">{step.index}</span>
                <div className="list-item-main">
                  <Link to={actionPath(step.actionId)} className="link-inline">
                    <strong>{step.title}</strong>
                  </Link>
                  <p className="list-item-desc muted">{step.reason}</p>
                </div>
                <div className="list-item-meta">
                  <StatusBadge status={step.status} />
                  <ExecutionFlowBadge meta={step.meta} actionStatus={step.status} />
                </div>
              </li>
            ))}
          </ol>
          <p className="muted critical-path-hint">
            Graph unter{' '}
            <Link to={scopedPath('/plan/gates', { initiativeId })} className="link-inline">
              Plan → Zielzustände
            </Link>
            {' '}pflegen.
          </p>
        </>
      )}
    </>
  )

  if (embedded) {
    return (
      <section className="card critical-path-panel">
        <div className="section-header">
          <div>
            <h2>Kritischer Pfad</h2>
            <p className="section-lead muted">
              Abhängigkeitspfad im aktiven Gate-Horizont — Steuerungsantwort für lineare
              Vorhaben (A2).
            </p>
          </div>
        </div>
        {body}
      </section>
    )
  }

  return body
}