import { useEffect, useMemo, useState } from 'react'
import { Link, useNavigate, useParams } from 'react-router-dom'
import { ArrowLeft, FileSpreadsheet, Loader2, Save, Trash2 } from 'lucide-react'
import { api } from '../utils/api'

const MODULE_LABEL = {
  nutrition: 'Ernährung',
  weight: 'Gewicht',
  blood_pressure: 'Blutdruck',
  activity: 'Aktivität',
}

function SampleTable({ sampleRows, columns }) {
  if (!sampleRows?.length || !columns?.length) return null
  const showCols = columns.slice(0, 8)
  return (
    <div style={{ overflowX: 'auto', marginTop: 12 }}>
      <table style={{ width: '100%', fontSize: 12, borderCollapse: 'collapse' }}>
        <thead>
          <tr>
            {showCols.map((c) => (
              <th
                key={c}
                style={{
                  textAlign: 'left',
                  padding: '8px 6px',
                  borderBottom: '1px solid var(--border)',
                  color: 'var(--text2)',
                  whiteSpace: 'nowrap',
                }}
              >
                {c}
              </th>
            ))}
          </tr>
        </thead>
        <tbody>
          {sampleRows.slice(0, 5).map((row, i) => (
            <tr key={i}>
              {showCols.map((c) => (
                <td
                  key={c}
                  style={{
                    padding: '6px',
                    borderBottom: '1px solid var(--border)',
                    maxWidth: 140,
                    overflow: 'hidden',
                    textOverflow: 'ellipsis',
                  }}
                >
                  {row[c] ?? '—'}
                </td>
              ))}
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  )
}

export default function AdminCsvTemplateEditorPage() {
  const { id: routeId } = useParams()
  const navigate = useNavigate()
  const isNew = routeId === 'new'
  const templateId = isNew ? null : Number(routeId)

  const [modules, setModules] = useState([])
  const [module, setModule] = useState('nutrition')
  const [mappingName, setMappingName] = useState('')
  const [description, setDescription] = useState('')
  const [delimiter, setDelimiter] = useState(';')
  const [encoding, setEncoding] = useState('utf-8')
  const [hasHeader, setHasHeader] = useState(true)
  const [columnSignature, setColumnSignature] = useState([])
  const [columns, setColumns] = useState([])
  const [fieldMappings, setFieldMappings] = useState({})
  const [typeConversionsText, setTypeConversionsText] = useState('{}')
  const [sampleRows, setSampleRows] = useState([])
  const [seedHint, setSeedHint] = useState(null)

  const [file, setFile] = useState(null)
  const [delimiterOverride, setDelimiterOverride] = useState('')
  const [seedTemplateId, setSeedTemplateId] = useState('')
  const [seedOptions, setSeedOptions] = useState([])

  const [loading, setLoading] = useState(!isNew)
  const [analyzing, setAnalyzing] = useState(false)
  const [saving, setSaving] = useState(false)
  const [error, setError] = useState(null)

  const modMeta = useMemo(() => modules.find((m) => m.id === module), [modules, module])
  const targetOptions = useMemo(() => {
    if (!modMeta?.fields) return []
    return Object.entries(modMeta.fields).map(([key, meta]) => ({
      value: key,
      label: `${key}${meta.required ? ' *' : ''}`,
    }))
  }, [modMeta])

  const requiredTargets = useMemo(() => {
    if (!modMeta?.fields) return []
    return Object.entries(modMeta.fields)
      .filter(([, v]) => v.required)
      .map(([k]) => k)
  }, [modMeta])

  useEffect(() => {
    api
      .getCsvModules()
      .then((r) => setModules(r.modules || []))
      .catch(() => {})
  }, [])

  useEffect(() => {
    if (!module) return
    api
      .adminListCsvTemplates(module)
      .then((d) => setSeedOptions(d.templates || []))
      .catch(() => setSeedOptions([]))
  }, [module])

  useEffect(() => {
    if (isNew || !templateId) return
    let ok = true
    setLoading(true)
    setError(null)
    api
      .adminGetCsvTemplate(templateId)
      .then((t) => {
        if (!ok) return
        setModule(t.module)
        setMappingName(t.mapping_name || '')
        setDescription(t.description || '')
        setDelimiter(t.delimiter || ',')
        setEncoding(t.encoding || 'utf-8')
        setHasHeader(!!t.has_header)
        setColumnSignature(t.column_signature || [])
        const fm = t.field_mappings || {}
        setFieldMappings(fm)
        setColumns(Object.keys(fm))
        setTypeConversionsText(JSON.stringify(t.type_conversions || {}, null, 2))
        setSampleRows([])
        setSeedHint(null)
      })
      .catch((e) => {
        if (ok) setError(e.message)
      })
      .finally(() => {
        if (ok) setLoading(false)
      })
    return () => {
      ok = false
    }
  }, [isNew, templateId])

  const assignedTargets = useMemo(() => {
    return new Set(
      Object.values(fieldMappings).filter((v) => v && v !== '-' && v !== '_skip'),
    )
  }, [fieldMappings])

  const missingRequired = useMemo(() => {
    return requiredTargets.filter((r) => !assignedTargets.has(r))
  }, [requiredTargets, assignedTargets])

  const handleAnalyze = async () => {
    if (!file) {
      setError('Bitte eine CSV-Datei wählen.')
      return
    }
    setAnalyzing(true)
    setError(null)
    try {
      const delim = delimiterOverride || null
      const seed = seedTemplateId === '' ? null : Number(seedTemplateId)
      const res = await api.adminAnalyzeCsvTemplate(file, module, delim, seed)
      setColumns(res.columns || [])
      setColumnSignature(res.column_signature_normalized || [])
      setFieldMappings(res.field_mappings || {})
      setTypeConversionsText(JSON.stringify(res.type_conversions || {}, null, 2))
      setSampleRows(res.sample_rows || [])
      setDelimiter(res.delimiter || ';')
      setEncoding(res.encoding || 'utf-8')
      setSeedHint(res.seed_template || null)
    } catch (e) {
      setError(e.message || 'Analyse fehlgeschlagen')
    } finally {
      setAnalyzing(false)
    }
  }

  const updateMapping = (col, dbField) => {
    setFieldMappings((prev) => ({ ...prev, [col]: dbField || '-' }))
  }

  const handleSave = async () => {
    setError(null)
    let tc = null
    try {
      tc = JSON.parse(typeConversionsText || '{}')
      if (tc !== null && typeof tc !== 'object') throw new Error()
    } catch {
      setError('type_conversions: ungültiges JSON.')
      return
    }
    if (!mappingName.trim()) {
      setError('Bitte einen Namen für die Vorlage eingeben.')
      return
    }
    if (!columns.length || !Object.keys(fieldMappings).length) {
      setError('Keine Spalten-Zuordnung: CSV analysieren oder Vorlage laden.')
      return
    }
    if (missingRequired.length) {
      setError(`Pflicht-Zielfelder fehlen: ${missingRequired.join(', ')}`)
      return
    }

    const payload = {
      module,
      mapping_name: mappingName.trim(),
      description: description.trim() || null,
      column_signature: columnSignature.length ? columnSignature : null,
      delimiter,
      encoding: encoding || 'utf-8',
      has_header: hasHeader,
      field_mappings: fieldMappings,
      type_conversions: tc,
    }

    if (!payload.column_signature?.length) {
      setError('column_signature fehlt — bitte CSV erneut analysieren.')
      return
    }

    setSaving(true)
    try {
      if (isNew) {
        await api.adminCreateCsvTemplate(payload)
      } else {
        const { module: _m, ...patch } = payload
        await api.adminUpdateCsvTemplate(templateId, patch)
      }
      navigate('/admin/csv-templates')
    } catch (e) {
      setError(e.message || 'Speichern fehlgeschlagen')
    } finally {
      setSaving(false)
    }
  }

  const handleDelete = async () => {
    if (isNew || !templateId) return
    if (!confirm('System-Vorlage wirklich löschen?')) return
    setError(null)
    try {
      await api.adminDeleteCsvTemplate(templateId)
      navigate('/admin/csv-templates')
    } catch (e) {
      setError(e.message || 'Löschen fehlgeschlagen')
    }
  }

  if (loading) {
    return (
      <div style={{ padding: 24, textAlign: 'center' }}>
        <Loader2 size={28} className="spin" style={{ animation: 'spin 0.8s linear infinite' }} />
      </div>
    )
  }

  return (
    <div style={{ padding: '16px 16px 96px', maxWidth: 920, margin: '0 auto' }}>
      <Link
        to="/admin/csv-templates"
        className="btn btn-secondary"
        style={{ display: 'inline-flex', alignItems: 'center', gap: 8, marginBottom: 16, textDecoration: 'none' }}
      >
        <ArrowLeft size={18} /> Zur Liste
      </Link>

      <h1 className="page-title" style={{ display: 'flex', alignItems: 'center', gap: 10 }}>
        <FileSpreadsheet size={26} strokeWidth={2} />
        {isNew ? 'Neue CSV-Vorlage' : 'Vorlage bearbeiten'}
      </h1>

      {error && (
        <div className="card" style={{ padding: 12, borderColor: 'var(--danger)', color: 'var(--danger)', marginBottom: 16 }}>
          {error}
        </div>
      )}

      <div className="card" style={{ padding: 16, marginBottom: 16 }}>
        <div className="form-label">Modul</div>
        <select
          className="form-input"
          value={module}
          disabled={!isNew}
          onChange={(e) => setModule(e.target.value)}
          style={{ width: '100%', marginTop: 8 }}
        >
          {modules.map((m) => (
            <option key={m.id} value={m.id}>
              {MODULE_LABEL[m.id] || m.id}
            </option>
          ))}
        </select>
        {!isNew && (
          <p style={{ fontSize: 13, color: 'var(--text3)', marginTop: 8 }}>
            Modul bestehender Vorlagen kann nicht geändert werden.
          </p>
        )}
      </div>

      <div className="card" style={{ padding: 16, marginBottom: 16 }}>
        <div className="form-label">1. Beispiel-CSV (wie Import)</div>
        <input
          type="file"
          accept=".csv,text/csv"
          className="form-input"
          style={{ marginTop: 8, width: '100%' }}
          onChange={(e) => setFile(e.target.files?.[0] || null)}
        />
        <div style={{ marginTop: 12, display: 'grid', gap: 12 }}>
          <label style={{ fontSize: 14, color: 'var(--text2)' }}>
            Trennzeichen (optional, sonst automatisch):
            <select
              className="form-input"
              style={{ width: '100%', marginTop: 6 }}
              value={delimiterOverride}
              onChange={(e) => setDelimiterOverride(e.target.value)}
            >
              <option value="">Auto</option>
              <option value=";">Semikolon</option>
              <option value=",">Komma</option>
              <option value="\t">Tab</option>
            </select>
          </label>
          <label style={{ fontSize: 14, color: 'var(--text2)' }}>
            Optional: feste Seed-Vorlage für Vorschläge:
            <select
              className="form-input"
              style={{ width: '100%', marginTop: 6 }}
              value={seedTemplateId}
              onChange={(e) => setSeedTemplateId(e.target.value)}
            >
              <option value="">Beste passende System-Vorlage (Jaccard)</option>
              {seedOptions.map((s) => (
                <option key={s.id} value={String(s.id)}>
                  {s.mapping_name}
                </option>
              ))}
            </select>
          </label>
        </div>
        <button
          type="button"
          className="btn btn-primary"
          style={{ marginTop: 16, width: '100%' }}
          disabled={!file || analyzing}
          onClick={handleAnalyze}
        >
          {analyzing ? (
            <>
              <Loader2 size={18} style={{ marginRight: 8, animation: 'spin 0.7s linear infinite' }} />
              Analysiere …
            </>
          ) : (
            'CSV analysieren & Vorschläge'
          )}
        </button>
        {seedHint && (
          <p style={{ fontSize: 13, color: 'var(--text2)', marginTop: 12 }}>
            Seed: <strong>{seedHint.mapping_name}</strong> · Übereinstimmung ca.{' '}
            {Math.round((seedHint.confidence || 0) * 100)} %
          </p>
        )}
        {sampleRows.length > 0 && <SampleTable sampleRows={sampleRows} columns={columns} />}
      </div>

      <div className="card" style={{ padding: 16, marginBottom: 16 }}>
        <div className="form-label">2. Stammdaten</div>
        <label className="form-label" style={{ marginTop: 12 }}>
          Name *
        </label>
        <input
          className="form-input"
          style={{ width: '100%' }}
          value={mappingName}
          onChange={(e) => setMappingName(e.target.value)}
          placeholder="z. B. FDDB Export 2026"
        />
        <label className="form-label" style={{ marginTop: 12 }}>
          Beschreibung
        </label>
        <textarea
          className="form-input"
          style={{ width: '100%', minHeight: 64 }}
          value={description}
          onChange={(e) => setDescription(e.target.value)}
        />
        <div style={{ display: 'grid', gridTemplateColumns: '1fr 1fr', gap: 12, marginTop: 12 }}>
          <label>
            <span className="form-label">Trennzeichen (gespeichert)</span>
            <select className="form-input" style={{ width: '100%', marginTop: 6 }} value={delimiter} onChange={(e) => setDelimiter(e.target.value)}>
              <option value=";">Semikolon</option>
              <option value=",">Komma</option>
              <option value="\t">Tab</option>
            </select>
          </label>
          <label>
            <span className="form-label">Kopfzeile</span>
            <select
              className="form-input"
              style={{ width: '100%', marginTop: 6 }}
              value={hasHeader ? 'yes' : 'no'}
              onChange={(e) => setHasHeader(e.target.value === 'yes')}
            >
              <option value="yes">Ja</option>
              <option value="no">Nein (nicht unterstützt im Import)</option>
            </select>
          </label>
        </div>
      </div>

      <div className="card" style={{ padding: 16, marginBottom: 16 }}>
        <div className="form-label">3. Spalten → Zielfelder (* = Pflicht)</div>
        {!columns.length ? (
          <p style={{ fontSize: 14, color: 'var(--text2)', marginTop: 8 }}>Nach CSV-Analyse erscheinen die Zeilen hier.</p>
        ) : (
          <div style={{ marginTop: 12, display: 'flex', flexDirection: 'column', gap: 10 }}>
            {columns.map((col) => (
              <div
                key={col}
                style={{
                  display: 'grid',
                  gridTemplateColumns: 'minmax(0, 1fr) minmax(140px, 200px)',
                  gap: 10,
                  alignItems: 'center',
                }}
              >
                <code style={{ fontSize: 12, wordBreak: 'break-word', color: 'var(--text2)' }}>{col}</code>
                <select
                  className="form-input"
                  value={fieldMappings[col] || '-'}
                  onChange={(e) => updateMapping(col, e.target.value)}
                >
                  <option value="-">— ignorieren</option>
                  {targetOptions.map((o) => (
                    <option key={o.value} value={o.value}>
                      {o.label}
                    </option>
                  ))}
                </select>
              </div>
            ))}
          </div>
        )}
        {missingRequired.length > 0 && (
          <p style={{ fontSize: 13, color: 'var(--danger)', marginTop: 12 }}>
            Noch zuzuweisen: {missingRequired.join(', ')}
          </p>
        )}
      </div>

      <div className="card" style={{ padding: 16, marginBottom: 16 }}>
        <div className="form-label">4. type_conversions (JSON)</div>
        <p style={{ fontSize: 13, color: 'var(--text2)', marginTop: 8 }}>
          Vom Vorschlag übernommen; bei Bedarf manuell anpassen (z. B. kJ-Faktor, Datumsformat).
        </p>
        <textarea
          className="form-input"
          style={{ width: '100%', minHeight: 200, marginTop: 8, fontFamily: 'monospace', fontSize: 12 }}
          value={typeConversionsText}
          onChange={(e) => setTypeConversionsText(e.target.value)}
        />
      </div>

      <div style={{ display: 'flex', flexWrap: 'wrap', gap: 12 }}>
        <button type="button" className="btn btn-primary" disabled={saving} onClick={handleSave} style={{ flex: 1, minWidth: 160 }}>
          {saving ? (
            <>
              <Loader2 size={18} style={{ marginRight: 8, animation: 'spin 0.7s linear infinite' }} />
              Speichern …
            </>
          ) : (
            <>
              <Save size={18} style={{ marginRight: 8 }} />
              Speichern
            </>
          )}
        </button>
        {!isNew && (
          <button type="button" className="btn btn-secondary" onClick={handleDelete} style={{ color: 'var(--danger)', borderColor: 'var(--danger)' }}>
            <Trash2 size={18} style={{ marginRight: 8 }} />
            Löschen
          </button>
        )}
      </div>
    </div>
  )
}