import React, { useEffect, useMemo, useState } from 'react'
import { useParams, useLocation } from 'react-router-dom'
import api from '../utils/api'
import PageReturnButton from '../components/PageReturnButton'
import NavStateLink from '../components/NavStateLink'
import {
  EXERCISES_LIST_PATH,
  buildCurrentLocationReturnContext,
} from '../utils/navReturnContext'
import ExerciseRichTextBlock from '../components/ExerciseRichTextBlock'
import ExerciseAttachmentMediaStrip from '../components/ExerciseAttachmentMediaStrip'
import CombinationPlanBracket from '../components/CombinationPlanBracket'
import ExercisePeekModal from '../components/ExercisePeekModal'
import { formatSkillLevelSlug } from '../constants/skillLevels'
import { formatExerciseSkillIntensityLabel } from '../constants/exerciseSkillIntensity'

function TagRow({ exercise }) {
  const tags = []
  ;(exercise.focus_areas || []).forEach((f) => {
    tags.push({ key: `fa-${f.id}`, label: f.name, accent: !!f.is_primary })
  })
  ;(exercise.training_styles || []).forEach((t) => {
    tags.push({ key: `ts-${t.id}`, label: t.name, accent: false })
  })
  ;(exercise.training_types || []).forEach((t) => {
    tags.push({ key: `tt-${t.id}`, label: t.name, accent: false })
  })
  ;(exercise.target_groups || []).forEach((g) => {
    tags.push({ key: `tg-${g.id}`, label: g.name, accent: !!g.is_primary })
  })
  if (tags.length === 0) return null
  return (
    <div className="exercise-tag-row">
      {tags.map((t) => (
        <span key={t.key} className={`exercise-tag${t.accent ? ' exercise-tag--accent' : ''}`}>
          {t.label}
        </span>
      ))}
    </div>
  )
}

function metaParts(exercise) {
  const parts = []
  if (exercise.duration_min != null || exercise.duration_max != null) {
    const a = exercise.duration_min
    const b = exercise.duration_max
    if (a != null && b != null && a !== b) parts.push(`${a}–${b} Min.`)
    else if (a != null) parts.push(`ca. ${a} Min.`)
    else if (b != null) parts.push(`ca. ${b} Min.`)
  }
  if (exercise.group_size_min != null || exercise.group_size_max != null) {
    const a = exercise.group_size_min
    const b = exercise.group_size_max
    if (a != null && b != null && a !== b) parts.push(`Gruppe ${a}–${b}`)
    else if (a != null) parts.push(`Gruppe ab ${a}`)
    else if (b != null) parts.push(`Gruppe bis ${b}`)
  }
  return parts
}

function ExerciseDetailPage() {
  const { id } = useParams()
  const location = useLocation()
  const editReturnContext = useMemo(
    () => buildCurrentLocationReturnContext(location, 'Zurück zur Übung'),
    [location]
  )
  const [exercise, setExercise] = useState(null)
  const [error, setError] = useState(null)
  const [loading, setLoading] = useState(true)
  /** Schnellansicht für eingebettete Einzelübungen (Kombination) — ohne Route zu verlassen */
  const [embeddedPeekExerciseId, setEmbeddedPeekExerciseId] = useState(null)

  useEffect(() => {
    let cancelled = false
    const load = async () => {
      setLoading(true)
      setError(null)
      try {
        const data = await api.getExercise(id)
        if (!cancelled) setExercise(data)
      } catch (err) {
        if (!cancelled) setError(err)
      } finally {
        if (!cancelled) setLoading(false)
      }
    }
    if (id) load()
    return () => {
      cancelled = true
    }
  }, [id])

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

  if (error) {
    const msg = error.message || String(error)
    return (
      <div style={{ padding: '1rem' }} className="app-page">
        <div className="card">
          <h2>Übung</h2>
          <p style={{ color: 'var(--danger)' }}>{msg}</p>
          <PageReturnButton
            fallbackPath={EXERCISES_LIST_PATH}
            fallbackLabel="Zurück zur Übungsliste"
          />
        </div>
      </div>
    )
  }

  if (!exercise) return null

  const meta = metaParts(exercise)

  const isCombinationDetail =
    (exercise.exercise_kind || '').toLowerCase().trim() === 'combination' &&
    Array.isArray(exercise.combination_slots) &&
    exercise.combination_slots.length > 0
  const catalogMethodProfileForBracket =
    exercise.method_profile &&
    typeof exercise.method_profile === 'object' &&
    !Array.isArray(exercise.method_profile)
      ? exercise.method_profile
      : {}

  return (
    <div className="exercise-detail-shell" style={{ padding: '12px 12px 24px' }}>
      <ExercisePeekModal
        key={embeddedPeekExerciseId != null ? String(embeddedPeekExerciseId) : 'exercise-detail-peek'}
        open={embeddedPeekExerciseId != null}
        exerciseId={embeddedPeekExerciseId}
        onClose={() => setEmbeddedPeekExerciseId(null)}
      />
      <div style={{ marginBottom: '12px', display: 'flex', justifyContent: 'space-between', gap: '8px', flexWrap: 'wrap', alignItems: 'center' }}>
        <PageReturnButton
          fallbackPath={EXERCISES_LIST_PATH}
          fallbackLabel="Zurück zur Übungsliste"
          className="page-return-btn btn btn-secondary btn-small"
        />
        <div style={{ display: 'flex', flexWrap: 'wrap', gap: '8px', marginLeft: 'auto' }}>
          <NavStateLink
            to={`/exercises/${exercise.id}/edit`}
            returnContext={editReturnContext}
            className="btn btn-primary"
          >
            Bearbeiten
          </NavStateLink>
        </div>
      </div>

      <div className="card exercise-detail-section">
        <h1 style={{ margin: 0, fontSize: '1.35rem', lineHeight: 1.25 }}>{exercise.title}</h1>
        {exercise.summary && (
          <div style={{ marginTop: '10px', color: 'var(--text2)', fontSize: '15px' }}>
            <ExerciseRichTextBlock html={exercise.summary} exerciseId={exercise.id} media={exercise.media} />
          </div>
        )}
        <TagRow exercise={exercise} />
        <div style={{ display: 'flex', flexWrap: 'wrap', gap: '6px', marginTop: '10px' }}>
          <span className="badge">{exercise.visibility}</span>
          <span className="badge">{exercise.status}</span>
          {exercise.club_name && <span className="badge">{exercise.club_name}</span>}
        </div>
        {meta.length > 0 && <p className="exercise-meta-line">{meta.join(' · ')}</p>}
      </div>

      {isCombinationDetail ? (
        <section className="card exercise-detail-section">
          <h2>Ablauf und Stationen</h2>
          <p style={{ marginTop: 0, fontSize: '0.88rem', color: 'var(--text2)', lineHeight: 1.45 }}>
            Katalog‑Ablauf mit Archetyp, Zeiten und Stationen. Station bzw. Einzelübung antippen öffnet eine
            Schnellansicht mit Kurztext und Ablauf, ohne diese Seite zu verlassen. Die vollständige Übungsseite
            liegt im Popup unten als Link.
          </p>
          <div className="training-run-combo-embed">
            <CombinationPlanBracket
              methodArchetype={String(exercise.method_archetype || '').trim()}
              methodProfile={catalogMethodProfileForBracket}
              combinationSlots={exercise.combination_slots}
              planningAdjusted={false}
              candidateInteraction="button"
              onCandidatePeek={(exerciseId) => setEmbeddedPeekExerciseId(Number(exerciseId))}
            />
          </div>
        </section>
      ) : null}

      {exercise.goal && (
        <section className="card exercise-detail-section">
          <h2>Ziel</h2>
          <ExerciseRichTextBlock html={exercise.goal} exerciseId={exercise.id} media={exercise.media} />
        </section>
      )}

      {(exercise.equipment || []).length > 0 && (
        <section className="card exercise-detail-section">
          <h2>Material &amp; Aufbau</h2>
          <ul style={{ paddingLeft: '1.2rem', margin: 0 }}>
            {exercise.equipment.map((x, i) => (
              <li key={i}>{x}</li>
            ))}
          </ul>
        </section>
      )}

      {exercise.preparation && (
        <section className="card exercise-detail-section">
          <h2>Vorbereitung</h2>
          <ExerciseRichTextBlock html={exercise.preparation} exerciseId={exercise.id} media={exercise.media} />
        </section>
      )}

      {exercise.execution && (
        <section className="card exercise-detail-section">
          <h2>Ablauf</h2>
          <ExerciseRichTextBlock html={exercise.execution} exerciseId={exercise.id} media={exercise.media} />
        </section>
      )}

      <ExerciseAttachmentMediaStrip exercise={exercise} exerciseId={exercise.id} />

      {exercise.trainer_notes && (
        <section className="card exercise-detail-section">
          <h2>Hinweise für Trainer</h2>
          <ExerciseRichTextBlock html={exercise.trainer_notes} exerciseId={exercise.id} media={exercise.media} />
        </section>
      )}

      {(exercise.skills || []).length > 0 && (
        <section className="card exercise-detail-section">
          <h2>Fähigkeiten</h2>
          <div className="exercise-tag-row">
            {exercise.skills.map((s) => {
              const rl = formatSkillLevelSlug(s.required_level)
              const tl = formatSkillLevelSlug(s.target_level)
              const lvl =
                rl || tl ? ` (${[rl, tl].filter(Boolean).join(' → ')})` : ''
              return (
                <span key={s.id} className="exercise-tag">
                  {s.skill_name}
                  {` · ${formatExerciseSkillIntensityLabel(s.intensity)}`}
                  {lvl}
                </span>
              )
            })}
          </div>
        </section>
      )}

      {(exercise.variants || []).length > 0 && (
        <section className="card exercise-detail-section">
          <h2>Varianten</h2>
          {exercise.variants.map((v) => {
            const dur =
              v.duration_min != null || v.duration_max != null
                ? v.duration_min != null && v.duration_max != null && v.duration_min !== v.duration_max
                  ? `${v.duration_min}–${v.duration_max} Min.`
                  : v.duration_min != null
                    ? `ca. ${v.duration_min} Min.`
                    : `bis ca. ${v.duration_max} Min.`
                : null
            const diffLabel =
              v.difficulty_adjustment === 'easier'
                ? 'einfacher'
                : v.difficulty_adjustment === 'harder'
                  ? 'schwerer'
                  : v.difficulty_adjustment === 'same'
                    ? 'gleiche Schwierigkeit'
                    : v.difficulty_adjustment === 'adapted'
                      ? 'angepasst'
                      : null
            const equip =
              Array.isArray(v.equipment_changes) && v.equipment_changes.length > 0
                ? v.equipment_changes.join(', ')
                : null
            return (
              <div
                key={v.id}
                style={{
                  marginBottom: '1rem',
                  paddingBottom: '1rem',
                  borderBottom: '1px solid var(--border)',
                }}
              >
                <strong style={{ fontSize: '15px' }}>{v.variant_name}</strong>
                {(dur || diffLabel || equip || v.progression_level != null) && (
                  <div style={{ fontSize: '13px', color: 'var(--text3)', marginTop: '4px' }}>
                    {[dur, diffLabel, equip && `Material: ${equip}`, v.progression_level != null && `Progression ${v.progression_level}`]
                      .filter(Boolean)
                      .join(' · ')}
                  </div>
                )}
                {v.description && <p style={{ color: 'var(--text2)', marginTop: '4px' }}>{v.description}</p>}
                {v.execution_changes && (
                  <div style={{ marginTop: '8px' }}>
                    <ExerciseRichTextBlock
                      html={v.execution_changes}
                      exerciseId={exercise.id}
                      media={exercise.media}
                    />
                  </div>
                )}
              </div>
            )
          })}
        </section>
      )}
    </div>
  )
}

export default ExerciseDetailPage