'use client'

import { useEffect, useMemo, useState } from 'react'
import type { PageSpecV1 } from '@/lib/interactive-page'
import { intentColor } from '@/lib/interactive-demo/intent-colors'
import type { IntentId } from '@/lib/interactive-demo/types'
import { useDarkMode } from '@/components/interactive-demo/demo-speak'
import { cn } from '@/lib/utils'

function collectIntents(page: PageSpecV1): IntentId[] {
  const set = new Set<IntentId>()
  for (const card of page.overview?.cards ?? []) {
    if (card.intent) set.add(card.intent)
  }
  for (const section of page.sections) {
    for (const block of section.blocks) {
      if (block.type === 'stats') {
        for (const item of block.items) {
          if (item.intent) set.add(item.intent)
        }
      }
      if (block.type === 'chart') {
        for (const s of block.payload.series) {
          if (s.intent) set.add(s.intent)
        }
      }
      if (block.type === 'demo') {
        const panels = [
          ...block.demo.scene.panels,
          ...block.demo.acts.flatMap((a) => a.scene?.panels ?? []),
        ]
        for (const panel of panels) {
          if (panel.type === 'svg-scene') {
            for (const n of panel.payload.nodes) if (n.intent) set.add(n.intent)
            for (const e of panel.payload.edges ?? []) if (e.intent) set.add(e.intent)
          }
          if (panel.type === 'chart') {
            for (const s of panel.payload.series) if (s.intent) set.add(s.intent)
          }
        }
      }
    }
  }
  return [...set]
}

const INTENT_LABELS_FR: Record<IntentId, string> = {
  highlight: 'Focus',
  flow: 'Flux',
  cache: 'Mémoire',
  compute: 'Calcul',
  output: 'Résultat',
  warning: 'Attention',
}

const INTENT_LABELS_EN: Record<IntentId, string> = {
  highlight: 'Focus',
  flow: 'Flow',
  cache: 'Memory',
  compute: 'Compute',
  output: 'Result',
  warning: 'Warning',
}

export function PageStickyNav({ page }: { page: PageSpecV1 }) {
  const [active, setActive] = useState(page.sections[0]?.id ?? '')
  const dark = useDarkMode()
  const intents = useMemo(() => collectIntents(page), [page])

  useEffect(() => {
    const nodes = page.sections
      .map((s) => document.getElementById(s.id))
      .filter(Boolean) as HTMLElement[]
    if (!nodes.length) return

    const obs = new IntersectionObserver(
      (entries) => {
        const visible = entries
          .filter((e) => e.isIntersecting)
          .sort((a, b) => b.intersectionRatio - a.intersectionRatio)
        const top = visible[0]?.target?.id
        if (top) setActive(top)
      },
      { rootMargin: '-20% 0px -55% 0px', threshold: [0.1, 0.25, 0.5] }
    )
    nodes.forEach((n) => obs.observe(n))
    return () => obs.disconnect()
  }, [page.sections])

  return (
    <div
      className="sticky top-0 z-30 backdrop-blur-sm"
      style={{
        background: 'color-mix(in oklab, var(--pp-paper) 96%, transparent)',
        borderTop: '1px solid var(--pp-line)',
        borderBottom: '1px solid var(--pp-line)',
      }}
    >
      <nav
        className="mx-auto flex max-w-[1100px] gap-1 overflow-x-auto px-5 py-2.5 scrollbar-thin"
        aria-label="Sections"
        style={{ fontFamily: 'var(--pp-mono)' }}
      >
        {page.sections.map((s, i) => (
          <a
            key={s.id}
            href={`#${s.id}`}
            className={cn(
              'shrink-0 rounded-lg px-2.5 py-1.5 text-xs transition-colors',
              active === s.id ? 'font-semibold' : 'hover:opacity-80'
            )}
            style={
              active === s.id
                ? { background: 'var(--pp-ink)', color: 'var(--pp-paper)' }
                : { color: 'var(--pp-muted)' }
            }
          >
            {i + 1} · {s.title}
          </a>
        ))}
      </nav>
      {intents.length > 0 ? (
        <div
          className="mx-auto flex max-w-[1100px] flex-wrap gap-3 px-5 py-2 text-[11px]"
          style={{
            borderTop: '1px solid var(--pp-line)',
            fontFamily: 'var(--pp-mono)',
            color: 'var(--pp-muted)',
          }}
        >
          <span className="font-semibold uppercase tracking-[0.14em] text-[10px]">
            {page.lang.startsWith('fr') ? 'Légende' : 'Legend'}
          </span>
          {intents.map((id) => {
            const color = intentColor(id, dark)
            return (
              <span
                key={id}
                className="inline-flex items-center gap-1.5"
              >
                <span
                  className="inline-block h-2.5 w-2.5 rounded-full"
                  style={{ backgroundColor: color }}
                />
                {page.lang.startsWith('fr')
                  ? INTENT_LABELS_FR[id]
                  : INTENT_LABELS_EN[id]}
              </span>
            )
          })}
        </div>
      ) : null}
    </div>
  )
}