import { useEffect, useState } from 'react'
import { useNavigate, useParams } from 'react-router-dom'
import { api } from '../api'
import { Field, StoryCardRow, downloadJSON, pickJSONFile, useToast } from '../components'
import { useDebouncedSave } from '../hooks/useDebouncedSave'
import ArtPicker from '../ArtPicker'
import SchemaEditor, { NpcEditor, addNpc } from '../SchemaEditor'

export default function ScenarioEditor() {
  const { id } = useParams()
  const navigate = useNavigate()
  const [scenario, setScenario] = useState(null)
  const [status, setStatus] = useState('')
  // Raw text buffer for the stat_schema JSON editor + a live parse error.
  const [schemaText, setSchemaText] = useState('')
  const [schemaError, setSchemaError] = useState('')
  // Last successfully-parsed schema (drives the form editor + preview).
  const [parsedSchema, setParsedSchema] = useState(null)
  const [schemaView, setSchemaView] = useState('form') // 'form' | 'json'
  const toast = useToast()
  const debounceSave = useDebouncedSave()

  useEffect(() => {
    api.getScenario(id).then((s) => {
      setScenario(s)
      setSchemaText(s.stat_schema ? JSON.stringify(s.stat_schema, null, 2) : '')
      setParsedSchema(s.stat_schema || null)
    }).catch(() => navigate('/scenarios'))
  }, [id, navigate])

  const setField = (field, value) => {
    const next = { ...scenario, [field]: value }
    setScenario(next)
    debounceSave(field, async () => {
      await api.updateScenario(id, { [field]: value })
      setStatus('Saved')
      setTimeout(() => setStatus(''), 1500)
    })
  }

  // Several fields at once, in one PATCH — the art picker sets `image` and
  // `icon` together (choosing one clears the other, and they must not race).
  const setFields = (patch) => {
    setScenario((prev) => ({ ...prev, ...patch }))
    debounceSave('art', async () => {
      await api.updateScenario(id, patch)
      setStatus('Saved')
      setTimeout(() => setStatus(''), 1500)
    })
  }

  // JSON view: typing only updates the text buffer; nothing is parsed or saved
  // until the user clicks Save (so a half-typed edit doesn't spam errors).
  const onJsonText = (text) => {
    setSchemaText(text)
    if (schemaError) setSchemaError('')
  }

  // Parse the JSON box on demand: apply + save if valid, else show the error.
  const commitJson = () => {
    const trimmed = schemaText.trim()
    if (!trimmed) {
      setSchemaError('')
      setParsedSchema(null)
      saveSchema(null)
      return
    }
    let parsed
    try {
      parsed = JSON.parse(trimmed)
    } catch (err) {
      setSchemaError(`Invalid JSON: ${err.message}`)
      return
    }
    if (typeof parsed !== 'object' || Array.isArray(parsed)) {
      setSchemaError('The schema must be a JSON object (e.g. { "player": { … } }).')
      return
    }
    setSchemaError('')
    setParsedSchema(parsed)
    setSchemaText(JSON.stringify(parsed, null, 2))  // normalize / pretty-print
    saveSchema(parsed)
  }

  const saveSchema = async (parsed) => {
    await api.updateScenario(id, { stat_schema: parsed })
    setScenario((s) => ({ ...s, stat_schema: parsed }))
    setStatus('Saved')
    setTimeout(() => setStatus(''), 1500)
  }

  // Edits from the form editor: keep the JSON text in sync and save. An empty
  // schema clears the RPG layer (null).
  const applySchema = (next) => {
    const cleaned = next && Object.keys(next).length ? next : null
    setParsedSchema(cleaned)
    setSchemaText(cleaned ? JSON.stringify(cleaned, null, 2) : '')
    setSchemaError('')
    debounceSave('stat_schema', () => saveSchema(cleaned))
  }

  // NPCs live in the same stat_schema, but are edited in their own page
  // section — so this is just the `npcs` slice of the same save path.
  const setNpcs = (npcs) => {
    const next = { ...(parsedSchema || {}) }
    if (npcs && Object.keys(npcs).length) next.npcs = npcs
    else delete next.npcs
    applySchema(next)
  }

  const addCard = async () => {
    const card = await api.createStoryCard({ scenario_id: Number(id) })
    setScenario({ ...scenario, story_cards: [...scenario.story_cards, card] })
  }

  const updateCard = (card) => {
    setScenario({
      ...scenario,
      story_cards: scenario.story_cards.map((c) => (c.id === card.id ? card : c)),
    })
    debounceSave(`card-${card.id}`, () => {
      api.updateStoryCard(card.id, {
        name: card.name, type: card.type, keys: card.keys, entry: card.entry, notes: card.notes,
      })
    })
  }

  const deleteCard = async (cardId) => {
    await api.deleteStoryCard(cardId)
    setScenario({ ...scenario, story_cards: scenario.story_cards.filter((c) => c.id !== cardId) })
  }

  const exportCards = async () => {
    const cards = await api.exportStoryCards({ scenario_id: id })
    downloadJSON(cards, `${scenario.title.replace(/\W+/g, '-')}-cards.json`)
  }

  const importCards = async () => {
    try {
      const parsed = await pickJSONFile()
      const cards = Array.isArray(parsed) ? parsed : (parsed.cards || parsed.storyCards)
      if (!Array.isArray(cards)) return toast('Expected a JSON array of story cards.', 'error')
      const created = await api.importStoryCards({ scenario_id: Number(id), cards })
      setScenario({ ...scenario, story_cards: [...scenario.story_cards, ...created] })
    } catch (err) {
      toast(err.message, 'error')
    }
  }

  const exportScenario = async () => {
    downloadJSON(await api.exportScenario(id), `${scenario.title.replace(/\W+/g, '-')}.json`)
  }

  const deleteScenario = async () => {
    if (!confirm('Delete this scenario permanently?')) return
    await api.deleteScenario(id)
    navigate('/scenarios')
  }

  const play = async () => {
    const adv = await api.createAdventure({ scenario_id: Number(id) })
    navigate(`/play/${adv.id}`)
  }

  if (!scenario) return null
  // Shared demo scenarios (Phase 8) are visible to everyone but owned by no
  // one; the backend rejects edits, so present them read-only.
  const readOnly = !!scenario.is_public

  return (
    <div className="page">
      <div className="page-header">
        <h1>{readOnly ? 'Scenario (read-only)' : 'Edit Scenario'}</h1>
        <div style={{ display: 'flex', gap: 10, alignItems: 'center' }}>
          <span style={{ color: 'var(--text-dim)', fontSize: '0.85rem' }}>{status}</span>
          <button onClick={exportScenario}>Export</button>
          {!readOnly && <button className="danger" onClick={deleteScenario}>Delete</button>}
          <button className="primary" onClick={play}>Play</button>
        </div>
      </div>

      {readOnly && (
        <div className="demo-banner">
          This is a shared demo scenario — it can’t be edited, but you can hit
          <strong> Play</strong> to start your own adventure from it, or <strong>Export</strong> and
          re-import it as your own copy.
        </div>
      )}

      <fieldset disabled={readOnly} style={{ border: 'none', padding: 0, margin: 0, minWidth: 0 }}>
      <Field label="Title" value={scenario.title} onChange={(v) => setField('title', v)} />
      <Field label="Description" value={scenario.description} onChange={(v) => setField('description', v)}
        textarea placeholder="Shown in the scenario list; not sent to the AI." />
      <ArtPicker
        title={scenario.title}
        image={scenario.image}
        icon={scenario.icon}
        disabled={readOnly}
        onChange={setFields}
      />
      <Field label="Opening Prompt" value={scenario.prompt} onChange={(v) => setField('prompt', v)}
        textarea rows={6} placeholder="The opening story text. Supports ${placeholders} (Phase 5)." />
      <Field label="Plot Essentials (Memory)" value={scenario.memory} onChange={(v) => setField('memory', v)}
        textarea placeholder="Key facts the AI should always remember." />
      <Field label="Author's Note" value={scenario.authors_note} onChange={(v) => setField('authors_note', v)}
        textarea rows={2} placeholder="Style/theme guidance, injected near the end of context." />
      <Field label="AI Instructions" value={scenario.ai_instructions} onChange={(v) => setField('ai_instructions', v)}
        textarea rows={2} placeholder="Behavioral guidance for the model (always included)." />
      <Field label="Tags" value={scenario.tags} onChange={(v) => setField('tags', v)} placeholder="fantasy, mystery" />

      <div className="page-header" style={{ marginTop: 28 }}>
        <h2 style={{ margin: 0, fontFamily: 'Georgia, serif', fontSize: '1.2rem' }}>Story Cards</h2>
        <div style={{ display: 'flex', gap: 8 }}>
          <button onClick={exportCards} disabled={scenario.story_cards.length === 0}>Export</button>
          {!readOnly && <button onClick={importCards}>Import</button>}
          <button onClick={addCard}>+ Add Card</button>
        </div>
      </div>
      {scenario.story_cards.length === 0 && (
        <div className="empty" style={{ padding: '20px 0' }}>
          No story cards. Cards inject their Entry into context when a trigger word appears in the story.
        </div>
      )}
      {scenario.story_cards.map((card) => (
        <StoryCardRow key={card.id} card={card}
          onChange={updateCard} onDelete={() => deleteCard(card.id)} />
      ))}

      <div className="page-header" style={{ marginTop: 28 }}>
        <h2 style={{ margin: 0, fontFamily: 'Georgia, serif', fontSize: '1.2rem' }}>World State (RPG)</h2>
        <div className="panel-toggles">
          <button type="button" className={schemaView === 'form' ? 'active' : ''}
            onClick={() => setSchemaView('form')}>Editor</button>
          <button type="button" className={schemaView === 'json' ? 'active' : ''}
            onClick={() => setSchemaView('json')}>JSON</button>
        </div>
      </div>
      <p className="dim" style={{ margin: '0 0 10px', fontSize: '0.85rem' }}>
        Optional, and no longer how the story is tracked. Every campaign now keeps
        genre-neutral narrative state — who exists, where they are, what they hold,
        what has been established — without any schema at all, and that is what the
        narrator is told. Numbers defined here are recorded alongside it for
        scenarios that were built on them. Leave blank unless you have one.
      </p>
      {schemaView === 'form' ? (
        <SchemaEditor schema={parsedSchema} onChange={applySchema} />
      ) : (
        <>
          <textarea
            className="schema-editor"
            value={schemaText}
            onChange={(e) => onJsonText(e.target.value)}
            rows={14}
            spellCheck={false}
            placeholder={'{\n  "player": { "hp": { "min": 0, "max": 100, "initial": 100 } },\n  "npcs": {\n    "gwen": { "name": "Gwen", "keys": "Gwen, ranger", "desc": "...",\n      "stats": { "trust": { "min": -100, "max": 100, "initial": 20 } } }\n  },\n  "flags": { "has_key": { "desc": "...", "initial": false } },\n  "milestones": { "goal": { "desc": "..." } }\n}'}
          />
          <div className="schema-json-actions">
            <button type="button" className="primary" onClick={commitJson}>Save JSON</button>
            {schemaError
              ? <span className="schema-error">⚠ {schemaError}</span>
              : <span className="dim" style={{ fontSize: '0.8rem' }}>
                  Edits apply when you click Save.
                </span>}
          </div>
          <SchemaPreview schema={parsedSchema} />
        </>
      )}

      <div className="page-header" style={{ marginTop: 28 }}>
        <h2 style={{ margin: 0, fontFamily: 'Georgia, serif', fontSize: '1.2rem' }}>Cast &amp; NPCs</h2>
        {schemaView === 'form' && (
          <button onClick={() => setNpcs(addNpc(parsedSchema?.npcs))}>+ Add NPC</button>
        )}
      </div>
      <p className="dim" style={{ margin: '0 0 10px', fontSize: '0.85rem' }}>
        Characters the AI tracks by name. Each has its own trigger words, description and
        stats — a dragon’s <em>ferocity</em>, a ranger’s <em>trust</em> — addressed as
        <code> npc.&lt;id&gt;.&lt;stat&gt;</code>. Adding one here also creates a story card
        for it when an adventure starts.
      </p>
      {schemaView === 'form' ? (
        <NpcEditor npcs={parsedSchema?.npcs || {}} onChange={setNpcs} />
      ) : (
        <div className="empty" style={{ padding: '20px 0' }}>
          NPCs are part of the schema JSON above — switch to <strong>Editor</strong> to edit
          them as cards.
        </div>
      )}

      </fieldset>
    </div>
  )
}

// ---- Structured preview of a parsed stat_schema (read-only) ----

function statMeta(def) {
  const parts = []
  if (def.initial !== undefined) parts.push(`start ${def.initial}`)
  if (typeof def.min === 'number' && typeof def.max === 'number') parts.push(`${def.min}–${def.max}`)
  if (def.type === 'counter') parts.push('counter')
  if (typeof def.max_delta_per_turn === 'number') parts.push(`±${def.max_delta_per_turn}/turn`)
  if (def.cooldown) parts.push(`cooldown ${def.cooldown}`)
  return parts.join(' · ')
}

function StatDefRow({ name, def }) {
  if (!def || typeof def !== 'object') return null
  const bands = Array.isArray(def.bands)
    ? def.bands.filter((b) => Array.isArray(b) && b.length === 3)
        .map((b) => `${b[0]}–${b[1]} ${b[2]}`).join(', ')
    : null
  return (
    <div className="schema-stat">
      <div className="schema-stat-head">
        <span className="schema-stat-name">{name}</span>
        <span className="schema-stat-meta">{statMeta(def)}</span>
      </div>
      {def.desc && <div className="schema-desc">{def.desc}</div>}
      {bands && <div className="schema-bands">bands: {bands}</div>}
    </div>
  )
}

function StatDefGroup({ title, defs }) {
  const entries = Object.entries(defs || {}).filter(([, d]) => d && typeof d === 'object')
  if (entries.length === 0) return null
  return (
    <div className="schema-group">
      <div className="schema-group-title">{title}</div>
      {entries.map(([n, d]) => <StatDefRow key={n} name={n} def={d} />)}
    </div>
  )
}

function SchemaPreview({ schema }) {
  if (!schema || typeof schema !== 'object' || Array.isArray(schema)) return null
  const world = schema.world || {}
  const player = schema.player || {}
  const npcs = schema.npcs || {}
  const flags = schema.flags || {}
  const milestones = schema.milestones || {}
  const count = [world, player, npcs, flags, milestones]
    .reduce((n, o) => n + Object.keys(o || {}).length, 0)
  if (count === 0) return null

  return (
    <div className="schema-preview">
      <div className="schema-preview-title">Parsed structure</div>
      <StatDefGroup title="World" defs={world} />
      <StatDefGroup title="Player" defs={player} />
      {Object.entries(npcs).map(([npcId, npc]) => (
        npc && typeof npc === 'object' ? (
          <div key={npcId} className="schema-group">
            <div className="schema-group-title">
              {npc.name || npcId} <span className="schema-npc-id">npc.{npcId}</span>
            </div>
            {npc.keys && <div className="schema-desc">triggers: {npc.keys}</div>}
            {npc.desc && <div className="schema-desc">{npc.desc}</div>}
            {Object.entries(npc.stats || {}).map(([n, d]) => (
              <StatDefRow key={n} name={n} def={d} />
            ))}
          </div>
        ) : null
      ))}
      {Object.keys(flags).length > 0 && (
        <div className="schema-group">
          <div className="schema-group-title">Flags</div>
          {Object.entries(flags).map(([fid, f]) => (
            <div key={fid} className="schema-stat">
              <div className="schema-stat-head">
                <span className="schema-stat-name">{fid}</span>
                <span className="schema-stat-meta">{f?.initial ? 'on by default' : 'off by default'}</span>
              </div>
              {f?.desc && <div className="schema-desc">{f.desc}</div>}
            </div>
          ))}
        </div>
      )}
      {Object.keys(milestones).length > 0 && (
        <div className="schema-group">
          <div className="schema-group-title">Milestones</div>
          {Object.entries(milestones).map(([mid, m]) => (
            <div key={mid} className="schema-stat">
              <div className="schema-stat-head">
                <span className="schema-stat-name">{mid}</span>
              </div>
              {m?.desc && <div className="schema-desc">{m.desc}</div>}
            </div>
          ))}
        </div>
      )}
    </div>
  )
}