import React, { useState, useEffect } from 'react'
import { Link } from 'react-router-dom'
import { CalendarCheck, ClipboardList, FilePenLine, Library } from 'lucide-react'
import { useAuth } from '../context/AuthContext'
import api from '../utils/api'
import EmailVerificationBanner from '../components/EmailVerificationBanner'
import DashboardTrainingVisibilityWidget from '../components/DashboardTrainingVisibilityWidget'

function unitWhenLabel(u) {
  const d = u.planned_date ? String(u.planned_date).slice(0, 10) : ''
  const t = u.planned_time_start ? String(u.planned_time_start).slice(0, 5) : ''
  const bits = [d, t].filter(Boolean)
  return bits.length ? bits.join(' · ') : 'Termin'
}

function formatCappedCount(n, capped) {
  if (capped && n >= 1) return `${n}+`
  return String(n)
}

function Dashboard() {
  const [profile, setProfile] = useState(null)
  const [loading, setLoading] = useState(true)
  const [trainingHome, setTrainingHome] = useState(null)
  const [trainingHomeErr, setTrainingHomeErr] = useState(null)
  const [phase0Stats, setPhase0Stats] = useState(null)
  const [phase0Err, setPhase0Err] = useState(null)
  const { user } = useAuth()

  useEffect(() => {
    loadData()
  }, [])

  useEffect(() => {
    if (!user?.id) {
      setTrainingHome(null)
      setTrainingHomeErr(null)
      return undefined
    }
    let cancelled = false
    ;(async () => {
      setTrainingHomeErr(null)
      try {
        const today = new Date().toISOString().slice(0, 10)
        const [upcomingRaw, reviewPendingRaw, plannedPool] = await Promise.all([
          api.listTrainingUnits({
            assigned_to_me: true,
            status: 'planned',
            start_date: today,
            sort: 'asc',
            limit: 8,
          }),
          api.listTrainingUnits({
            assigned_to_me: true,
            debrief_pending: true,
            sort: 'desc',
            limit: 8,
          }),
          api.listTrainingUnits({
            assigned_to_me: true,
            status: 'planned',
            start_date: today,
            sort: 'asc',
            limit: 40,
          }),
        ])
        const noteHits = (plannedPool || []).filter((u) => {
          const tn = (u.trainer_notes || '').trim()
          const n = (u.notes || '').trim()
          return Boolean(tn || n)
        }).slice(0, 5)
        if (!cancelled) {
          setTrainingHome({
            upcoming: Array.isArray(upcomingRaw) ? upcomingRaw : [],
            reviewPending: Array.isArray(reviewPendingRaw) ? reviewPendingRaw : [],
            plannedWithNotes: noteHits,
          })
        }
      } catch (e) {
        if (!cancelled) {
          console.error('Dashboard Trainingsübersicht:', e)
          setTrainingHomeErr(e.message || 'Konnte Trainingsdaten nicht laden')
          setTrainingHome(null)
        }
      }
    })()
    return () => {
      cancelled = true
    }
  }, [user?.id])

  useEffect(() => {
    if (!user?.id) {
      setPhase0Stats(null)
      setPhase0Err(null)
      return undefined
    }
    let cancelled = false
    ;(async () => {
      setPhase0Err(null)
      try {
        const year = new Date().getFullYear()
        const yearStart = `${year}-01-01`
        const yearEnd = `${year}-12-31`
        const [draftList, mineList, ytdCompleted] = await Promise.all([
          api.listExercises({ created_by_me: true, status: 'draft', limit: 100 }),
          api.listExercises({ created_by_me: true, limit: 100 }),
          api.listTrainingUnits({
            assigned_to_me: true,
            status: 'completed',
            start_date: yearStart,
            end_date: yearEnd,
            limit: 250,
            sort: 'desc',
          }),
        ])
        if (!cancelled) {
          const drafts = Array.isArray(draftList) ? draftList : []
          setPhase0Stats({
            year,
            draftCount: drafts.length,
            draftCapped: drafts.length >= 100,
            draftPreview: drafts.slice(0, 8).map((ex) => ({
              id: ex.id,
              title: ex.title || `Übung #${ex.id}`,
            })),
            mineCount: Array.isArray(mineList) ? mineList.length : 0,
            mineCapped: Array.isArray(mineList) && mineList.length >= 100,
            ytdCompletedCount: Array.isArray(ytdCompleted) ? ytdCompleted.length : 0,
            ytdCapped: Array.isArray(ytdCompleted) && ytdCompleted.length >= 250,
          })
        }
      } catch (e) {
        if (!cancelled) {
          console.error('Dashboard Übungs-Kennzahlen:', e)
          setPhase0Err(e.message || 'Konnte Übungs-Kennzahlen nicht laden')
          setPhase0Stats(null)
        }
      }
    })()
    return () => {
      cancelled = true
    }
  }, [user?.id])

  const loadData = async () => {
    try {
      const profileData = await api.getCurrentProfile()
      setProfile(profileData)
    } catch (err) {
      console.error('Failed to load data:', err)
    } finally {
      setLoading(false)
    }
  }

  if (loading) {
    return (
      <div className="app-page" style={{ padding: '2rem 0', textAlign: 'center' }}>
        <div className="spinner"></div>
        <p>Laden...</p>
      </div>
    )
  }

  const draftsHref = '/exercises?status=draft&mine=1'
  const mineHref = '/exercises?mine=1'

  return (
    <div className="app-page dashboard-page">
      <div className="dashboard-greeting">
        <div>
          <h1 className="page-title" style={{ marginBottom: '6px' }}>
            Dashboard
          </h1>
          <p className="muted" style={{ marginTop: 0 }}>
            Willkommen, {user?.name || user?.email}! Shinkan unterstützt dich bei Übungen, Planung und
            Vereinsstruktur.
          </p>
        </div>
      </div>
      {profile && <EmailVerificationBanner profile={profile} />}

      {user?.id ? (
        <>
          <section className="dashboard-section" aria-labelledby="dash-phase0-title">
            <div className="dashboard-section__header">
              <div className="dashboard-section__headline">
                <h2 id="dash-phase0-title" className="dashboard-section__title">
                  Kurzüberblick
                </h2>
                <p className="dashboard-section__description">
                  Trainings dieses Kalenderjahres beziehen sich auf den <strong>geplanten Termin</strong> (nicht
                  zwingend Abschlussdatum). Zahlen können bei sehr vielen Einträgen mit „+“ enden.
                </p>
              </div>
            </div>
            {phase0Err ? (
              <p className="dashboard-phase0-kpis__err" role="alert">
                {phase0Err}
              </p>
            ) : null}
            {!phase0Err && !phase0Stats ? (
              <div className="dashboard-phase0-kpis__loading muted">Zahlen werden geladen…</div>
            ) : null}
            {!phase0Err && phase0Stats ? (
              <div className="dashboard-phase0-kpis">
                <Link className="dashboard-kpi-card" to={draftsHref}>
                  <span className="dashboard-kpi-card__icon" aria-hidden>
                    <FilePenLine size={22} strokeWidth={2} />
                  </span>
                  <span className="dashboard-kpi-card__value">
                    {formatCappedCount(phase0Stats.draftCount, phase0Stats.draftCapped)}
                  </span>
                  <span className="dashboard-kpi-card__label">Übungs-Entwürfe</span>
                  <span className="dashboard-kpi-card__hint">finalisieren</span>
                </Link>
                <Link className="dashboard-kpi-card" to={mineHref}>
                  <span className="dashboard-kpi-card__icon" aria-hidden>
                    <Library size={22} strokeWidth={2} />
                  </span>
                  <span className="dashboard-kpi-card__value">
                    {formatCappedCount(phase0Stats.mineCount, phase0Stats.mineCapped)}
                  </span>
                  <span className="dashboard-kpi-card__label">Meine Übungen</span>
                  <span className="dashboard-kpi-card__hint">alle Status</span>
                </Link>
                <div className="dashboard-kpi-card dashboard-kpi-card--static">
                  <span className="dashboard-kpi-card__icon" aria-hidden>
                    <ClipboardList size={22} strokeWidth={2} />
                  </span>
                  <span className="dashboard-kpi-card__value">
                    {formatCappedCount(phase0Stats.ytdCompletedCount, phase0Stats.ytdCapped)}
                  </span>
                  <span className="dashboard-kpi-card__label">Gehalten {phase0Stats.year}</span>
                  <span className="dashboard-kpi-card__hint">abrechnungsnah</span>
                </div>
              </div>
            ) : null}
            {!phase0Err && phase0Stats?.draftPreview?.length ? (
              <div className="card dashboard-draft-preview" style={{ marginTop: '1rem' }}>
                <h3 className="dashboard-preview-card__title" style={{ marginTop: 0 }}>
                  Entwürfe fertigstellen
                </h3>
                <p className="muted" style={{ marginTop: '0.35rem', marginBottom: '0.85rem', fontSize: '0.92rem' }}>
                  Private Übungs-Entwürfe (z. B. aus der Planung) — Ziel, Durchführung und Details in der Bearbeitung
                  ergänzen.
                </p>
                <ul className="dashboard-preview-card__list">
                  {phase0Stats.draftPreview.map((ex) => (
                    <li key={ex.id}>
                      <Link to={`/exercises/${ex.id}/edit`} className="dashboard-preview-card__link">
                        {ex.title}
                      </Link>
                    </li>
                  ))}
                </ul>
                <p style={{ margin: '0.75rem 0 0', fontSize: '0.86rem' }}>
                  <Link to={draftsHref}>Alle Entwürfe in der Übersicht</Link>
                </p>
              </div>
            ) : null}
          </section>

          <section className="dashboard-section" aria-labelledby="dash-trainings-title">
            <div className="dashboard-section__header">
              <div className="dashboard-section__headline">
                <h2 id="dash-trainings-title" className="dashboard-section__title">
                  Trainings
                </h2>
                <p className="dashboard-section__description">
                  Einheiten, bei denen du als Leitung oder Co-Trainer eingetragen bist.
                </p>
              </div>
              <div className="dashboard-section__actions">
                <Link to="/planning" className="btn btn-secondary" style={{ textDecoration: 'none' }}>
                  <CalendarCheck size={16} strokeWidth={2} aria-hidden style={{ marginRight: 6 }} />
                  Planung
                </Link>
              </div>
            </div>
            <div className="dashboard-training-preview-grid">
              <div className="card dashboard-preview-card">
                <h3 className="dashboard-preview-card__title">Nächste Termine</h3>
                {trainingHomeErr ? (
                  <p className="dashboard-preview-card__err">{trainingHomeErr}</p>
                ) : trainingHome?.upcoming?.length ? (
                  <ul className="dashboard-preview-card__list">
                    {trainingHome.upcoming.map((u) => (
                      <li key={u.id}>
                        <Link to={`/planning/run/${u.id}`} className="dashboard-preview-card__link">
                          {unitWhenLabel(u)}
                        </Link>
                        {u.group_name ? (
                          <span className="dashboard-preview-card__meta">{` — ${u.group_name}`}</span>
                        ) : null}
                        {u.lead_trainer_name ? (
                          <span className="dashboard-preview-card__sub">
                            Leitung: {u.lead_trainer_name}
                          </span>
                        ) : null}
                      </li>
                    ))}
                  </ul>
                ) : (
                  <p className="dashboard-preview-card__empty">
                    Keine anstehenden Termine.{' '}
                    <Link to="/planning">Zur Trainingsplanung</Link>
                  </p>
                )}
              </div>

              <div className="card dashboard-preview-card">
                <h3 className="dashboard-preview-card__title">Hinweise (anstehend)</h3>
                {trainingHomeErr ? (
                  <p className="dashboard-preview-card__err">{trainingHomeErr}</p>
                ) : trainingHome?.plannedWithNotes?.length ? (
                  <ul className="dashboard-preview-card__list dashboard-preview-card__list--notes">
                    {trainingHome.plannedWithNotes.map((u) => {
                      const snippet = (u.trainer_notes || u.notes || '').trim().slice(0, 120)
                      return (
                        <li key={`n-${u.id}`}>
                          <Link to={`/planning/run/${u.id}`} className="dashboard-preview-card__link">
                            {unitWhenLabel(u)}
                          </Link>
                          {u.group_name ? (
                            <span className="dashboard-preview-card__meta">{` · ${u.group_name}`}</span>
                          ) : null}
                          <div className="dashboard-preview-card__note-snippet">
                            {snippet}
                            {(u.trainer_notes || u.notes || '').trim().length > 120 ? '…' : ''}
                          </div>
                        </li>
                      )
                    })}
                  </ul>
                ) : (
                  <p className="dashboard-preview-card__empty">
                    Keine Vermerke in den nächsten geplanten Terminen.
                  </p>
                )}
              </div>

              <div className="card dashboard-preview-card">
                <h3 className="dashboard-preview-card__title">Offene Rückschau</h3>
                {trainingHomeErr ? (
                  <p className="dashboard-preview-card__err">{trainingHomeErr}</p>
                ) : trainingHome?.reviewPending?.length ? (
                  <ul className="dashboard-preview-card__list">
                    {trainingHome.reviewPending.map((u) => (
                      <li key={`r-${u.id}`}>
                        <Link to={`/planning?unit=${u.id}`} className="dashboard-preview-card__link">
                          {(u.actual_date || u.planned_date || '').toString().slice(0, 10) || 'Datum'}
                        </Link>
                        {u.group_name ? (
                          <span className="dashboard-preview-card__meta">{` — ${u.group_name}`}</span>
                        ) : null}
                      </li>
                    ))}
                  </ul>
                ) : (
                  <p className="dashboard-preview-card__empty">
                    Keine durchgeführten Trainings mit offener Nachbereitung. Zum Abschluss der Rückschau in der
                    Planung „Rückschau erledigt“ aktivieren.
                  </p>
                )}
              </div>
            </div>
            <DashboardTrainingVisibilityWidget user={user} />
          </section>
        </>
      ) : null}
    </div>
  )
}

export default Dashboard