import { useEffect, useMemo, useState } from 'react'
import type { ReactNode } from 'react'
import type { EditorProps } from '../registry'
import { useEditorState } from '../ui/hooks'
import { BREAKPOINTS, effective, patchFor, readField } from './model'
import type { Breakpoint, StyleField } from './model'
import { pxOf } from './tokens'
import type { Scale } from './tokens'
import { Icon } from '../ui/Icon'
import { describeStyle, fieldForSide } from './model'

type Data = Record<string, any>

const LEGACY_FLOW = ['vertical', 'horizontal', 'grid']
const ICON: Record<string, Record<string, string>> = {
  flow: { row: 'flow-row', stack: 'flow-stack', actions: 'flow-actions', vertical: 'flow-stack', horizontal: 'flow-row', grid: 'flow-grid' },
  align: { start: 'align-start', center: 'align-center', end: 'align-end', left: 'text-left', right: 'text-right' },
  justify: { start: 'align-start', center: 'align-center', end: 'align-end' },
}
const cap = (o: string) => o[0].toUpperCase() + o.slice(1)

/** Apply a `set` payload to local data the way the server will (null deletes). */
const applyLocal = (data: Data, patch: Record<string, unknown>): Data => {
  const next = { ...data }
  for (const [k, v] of Object.entries(patch)) v === null ? delete next[k] : (next[k] = v)
  return next
}

/**
 * The "Style" dialog: controls for every schema field tagged `x-style` (or inferred from naming),
 * grouped by what they do. Nothing here knows a node type - add an `x-style` field to any schema
 * and it shows up. Spacing is a box-model diagram; breakpoints edit `responsive.<bp>.*`.
 */
export function StylePanel({ node, schema, ctrl }: EditorProps) {
  const fields = useMemo(() => describeStyle(schema), [schema])
  const [data, setData] = useState<Data>(node.data ?? {})
  const [bp, setBp] = useState<Breakpoint | undefined>()
  const rev = useEditorState((s) => s.editRev)
  useEffect(() => {
    if (rev) void ctrl.node(node.id, true).then((n) => setData(n.data ?? {})).catch(() => {})
  }, [rev, ctrl, node.id])

  const hasResponsive = fields.some((f) => f.responsive.length)
  const shown = bp ? fields.filter((f) => f.responsive.includes(bp)) : fields
  const set = (f: StyleField, v: unknown) => {
    setData((d) => applyLocal(d, patchFor(d, f, v, bp)))
    void ctrl.setStyle(node.id, f, v, { bp })
  }
  const get = (f: StyleField) => readField(data, f, bp)

  const of = (...kinds: StyleField['kind'][]) => shown.filter((f) => kinds.includes(f.kind))
  const flow = fields.find((f) => f.kind === 'flow')
  const flowValue = flow ? String(readField(data, flow, bp) ?? data[flow.name] ?? '') : ''
  const showColumns = !flow || !flowValue || ['row', 'grid', 'horizontal'].includes(flowValue)

  return (
    <div className="cms-style">
      {hasResponsive && (
        <div className="cms-tabs" role="tablist" aria-label="Breakpoint">
          {[undefined, ...BREAKPOINTS].map((b) => (
            <button key={b ?? 'base'} role="tab" aria-selected={bp === b} className={bp === b ? 'is-on' : ''} onClick={() => setBp(b)}>
              {b ? b[0].toUpperCase() + b.slice(1) : 'All sizes'}
            </button>
          ))}
        </div>
      )}
      {bp && <p className="cms-muted">Overrides for {bp === 'mobile' ? 'small screens' : bp === 'tablet' ? 'tablets' : 'desktops'}; unset values inherit from “All sizes”.</p>}

      {of('flow', 'columns', 'align', 'justify').length > 0 && (
        <Section title="Layout">
          {of('flow', 'columns', 'align', 'justify')
            .filter((f) => f.kind !== 'columns' || showColumns)
            .map((f) => (
              <Control key={f.name} f={f} value={get(f)} onChange={(v) => set(f, v)} />
            ))}
        </Section>
      )}

      {!bp && fields.some((f) => f.kind === 'spacing' || f.kind === 'gap') && (
        <Section title="Spacing">
          <BoxModel fields={fields} data={data} onChange={set} ctrl={ctrl} />
          {fields.filter((f) => f.kind === 'gap').map((f) => (
            <Control key={f.name} f={f} value={data[f.name]} onChange={(v) => set(f, v)} scale={f.options.length ? ctrl.scaleFor(f) : undefined} />
          ))}
        </Section>
      )}

      {of('tone', 'border').length > 0 && (
        <Section title="Surface">
          {of('tone', 'border').map((f) => (
            <Control key={f.name} f={f} value={get(f)} onChange={(v) => set(f, v)} />
          ))}
        </Section>
      )}
      {of('reveal', 'choice').length > 0 && (
        <Section title="More">
          {of('reveal', 'choice').map((f) => (
            <Control key={f.name} f={f} value={get(f)} onChange={(v) => set(f, v)} />
          ))}
        </Section>
      )}

      {fields.some((f) => f.inferred) && <p className="cms-muted cms-style__note">Controls detected from field names. Add <code>x-style</code> to the schema to make this explicit.</p>}
    </div>
  )
}

function Section({ title, children }: { title: string; children: ReactNode }) {
  return (
    <section className="cms-style__section">
      <h4>{title}</h4>
      {children}
    </section>
  )
}

// --- controls ------------------------------------------------------------------------

function Control({ f, value, onChange, scale }: { f: StyleField; value: unknown; onChange(v: unknown): void; scale?: Scale }) {
  const set = value !== undefined && value !== null
  return (
    <div className="cms-ctl" data-style-field={f.name}>
      <div className="cms-ctl__head">
        <span className="cms-ctl__label" title={f.description}>
          {f.label}
        </span>
        {set && (
          <button type="button" className="cms-ctl__clear" aria-label={`Reset ${f.label}`} title="Reset (inherit)" onClick={() => onChange(undefined)}>
            <Icon name="refresh" size={14} />
          </button>
        )}
      </div>
      <Widget f={f} value={value} onChange={onChange} scale={scale} />
    </div>
  )
}

function Widget({ f, value, onChange, scale }: { f: StyleField; value: unknown; onChange(v: unknown): void; scale?: Scale }) {
  if (f.kind === 'columns') return <Columns f={f} value={value} onChange={onChange} />
  const icons = ICON[f.kind] ?? {}
  let options = f.options.map(String)
  if (f.kind === 'flow' && !LEGACY_FLOW.includes(String(value))) options = options.filter((o) => !LEGACY_FLOW.includes(o))
  if (options.length > 6) {
    return (
      <select className="cms-input" value={value === undefined ? '' : String(value)} onChange={(e) => onChange(e.target.value === '' ? undefined : e.target.value)}>
        <option value="">—</option>
        {options.map((o) => (
          <option key={o}>{o}</option>
        ))}
      </select>
    )
  }
  return <Chips options={options} value={value as string | undefined} onChange={onChange} icons={icons} scale={scale} />
}

function Chips({ options, value, onChange, icons = {}, scale }: { options: string[]; value?: string; onChange(v: string): void; icons?: Record<string, string>; scale?: Scale }) {
  return (
    <div className="cms-chips" role="radiogroup">
      {options.map((o) => {
        const px = scale ? pxOf(scale, o) : null
        return (
          <button key={o} type="button" role="radio" aria-checked={value === o} className={`cms-chip${value === o ? ' is-on' : ''}`} title={px !== null ? `${Math.round(px)}px` : undefined} onClick={() => onChange(o)}>
            {icons[o] && <Icon name={icons[o]} size={15} />}
            {icons[o] ? cap(o) : o}
          </button>
        )
      })}
    </div>
  )
}

function Columns({ f, value, onChange }: { f: StyleField; value: unknown; onChange(v: unknown): void }) {
  if (f.options.length) return <Chips options={f.options.map(String)} value={value === undefined ? undefined : String(value)} onChange={(v) => onChange(Number(v))} />
  const min = f.min ?? 1
  const max = f.max ?? 12
  const n = typeof value === 'number' ? value : undefined
  return (
    <div className="cms-stepper">
      <button type="button" className="cms-ico" aria-label="Fewer columns" disabled={(n ?? min) <= min} onClick={() => onChange(Math.max(min, (n ?? min + 1) - 1))}>
        −
      </button>
      <input className="cms-input" type="number" aria-label="Columns" min={min} max={max} value={n ?? ''} placeholder="auto" onChange={(e) => onChange(e.target.value === '' ? undefined : Math.min(max, Math.max(min, Number(e.target.value))))} />
      <button type="button" className="cms-ico" aria-label="More columns" disabled={(n ?? 0) >= max} onClick={() => onChange(Math.min(max, (n ?? min - 1) + 1))}>
        +
      </button>
    </div>
  )
}

// --- box model ---------------------------------------------------------------------------

type Edge = 'top' | 'right' | 'bottom' | 'left'

/** margin ⟶ padding diagram: one token select per side the schema can express. */
function BoxModel({ fields, data, onChange, ctrl }: { fields: StyleField[]; data: Data; onChange(f: StyleField, v: unknown): void; ctrl: EditorProps['ctrl'] }) {
  const boxes = (['margin', 'padding'] as const).filter((b) => fields.some((f) => f.kind === 'spacing' && f.box === b && f.options.length))
  if (!boxes.length) return null
  const cell = (box: 'margin' | 'padding', edge: Edge, seenAll: Set<string>) => {
    const f = fieldForSide(fields, box, edge)
    if (!f) return <span className="cms-box__none">–</span>
    if (f.side === 'all' || f.side === 'x' || f.side === 'y') {
      // One field covers several edges: put its select on the first, mark the rest as linked.
      if (seenAll.has(f.name)) return <span className="cms-box__link" title={`${f.label} (shared)`}>
          <Icon name="link" size={12} /> {f.side === 'all' ? 'all' : f.side}
        </span>
      seenAll.add(f.name)
    }
    const { value, from } = effective(data, fields, f)
    const own = data[f.name]
    const scale = ctrl.scaleFor(f)
    return (
      <select
        className={`cms-box__sel${own === undefined || own === null ? ' is-inherited' : ''}`}
        aria-label={`${box} ${f.side === 'all' ? 'all sides' : edge}`}
        value={own === undefined || own === null ? '' : String(own)}
        onChange={(e) => onChange(f, e.target.value === '' ? undefined : e.target.value)}
        title={f.description}
      >
        <option value="">{value !== undefined && from !== f ? `${String(value)} (${from.name})` : '—'}</option>
        {f.options.map((o) => {
          const px = pxOf(scale, String(o))
          return (
            <option key={String(o)} value={String(o)}>
              {String(o)}
              {px !== null ? ` · ${Math.round(px)}` : ''}
            </option>
          )
        })}
      </select>
    )
  }
  const render = (i: number): ReactNode => {
    const box = boxes[i]
    const seen = new Set<string>()
    return (
      <div className={`cms-box cms-box--${box}`} key={box}>
        <span className="cms-box__title">{box}</span>
        <div className="cms-box__top">{cell(box, 'top', seen)}</div>
        <div className="cms-box__left">{cell(box, 'left', seen)}</div>
        <div className="cms-box__mid">{i + 1 < boxes.length ? render(i + 1) : <span className="cms-box__content">content</span>}</div>
        <div className="cms-box__right">{cell(box, 'right', seen)}</div>
        <div className="cms-box__bottom">{cell(box, 'bottom', seen)}</div>
      </div>
    )
  }
  return <div className="cms-boxmodel">{render(0)}</div>
}