import { useEffect, useMemo, useState } from 'react'
import { NavLink, Outlet, useNavigate, useLocation } from 'react-router-dom'
import MoonDot from '../../components/MoonDot.jsx'
import BrandLogo from '../../components/BrandLogo.jsx'
import { useAuth } from '../../contexts/AuthContext.jsx'
import { useSite } from '../../contexts/SiteContext.jsx'
import { applyNavOverrides } from '../../lib/navOverrides.js'
import { useNavOverrides } from '../../lib/useNavOverrides.js'
import { withModuleNav } from '../../modules/nav.js'
import { useFeatureGate } from '../../modules/features.jsx'
import { navItemVisibleTo, allowedPathsFor, isAllowedPath } from '../../lib/adminNav.js'

// Small inline stroke icons (16px, currentColor) — same style as ProviderIcon.
// One shared frame keeps them terse; each item just supplies its path(s).
function Icon({ children, size = 16 }) {
  return (
    <svg
      width={size}
      height={size}
      viewBox="0 0 24 24"
      fill="none"
      stroke="currentColor"
      strokeWidth="2"
      strokeLinecap="round"
      strokeLinejoin="round"
      aria-hidden="true"
      focusable="false"
    >
      {children}
    </svg>
  )
}
const IconHome = () => <Icon><path d="M3 10.5 12 3l9 7.5" /><path d="M5 9.5V21h14V9.5" /></Icon>
const IconPosts = () => <Icon><path d="M5 3h14v18H5z" /><path d="M8 8h8M8 12h8M8 16h5" /></Icon>
const IconWiki = () => <Icon><path d="M4 4h9a3 3 0 0 1 3 3v13a2 2 0 0 0-2-2H4z" /><path d="M20 4h-2a2 2 0 0 0-2 2v14a2 2 0 0 1 2-2h2z" /></Icon>
const IconPages = () => <Icon><path d="M5 3h9l5 5v13H5z" /><path d="M14 3v5h5" /><path d="M8 13h8M8 17h8" /></Icon>
const IconActivity = () => <Icon><path d="M3 12h4l3 8 4-16 3 8h4" /></Icon>
const IconShield = () => <Icon><path d="M12 3l7 3v5c0 5-3.5 8-7 10-3.5-2-7-5-7-10V6z" /><path d="M9 12l2 2 4-4" /></Icon>
const IconUsers = () => <Icon><circle cx="9" cy="8" r="3" /><path d="M3 20a6 6 0 0 1 12 0" /><path d="M16 6a3 3 0 0 1 0 6M17 20a6 6 0 0 0-3-5" /></Icon>
const IconGear = () => <Icon><circle cx="12" cy="12" r="3" /><path d="M12 2v3M12 19v3M2 12h3M19 12h3M4.9 4.9l2.1 2.1M17 17l2.1 2.1M19.1 4.9L17 7M7 17l-2.1 2.1" /></Icon>
const IconHero = () => <Icon><path d="M3 5h18v14H3z" /><circle cx="8" cy="10" r="1.6" /><path d="M4 18l5-5 3 3 3-4 5 6" /></Icon>
const IconKey = () => <Icon><circle cx="8" cy="12" r="4" /><path d="M12 12h9M18 12v3M15 12v2" /></Icon>
const IconBot = () => <Icon><rect x="4" y="8" width="16" height="11" rx="2" /><path d="M12 8V4M8 13h.01M16 13h.01M9 17h6" /></Icon>
const IconPulse = () => <Icon><path d="M3 12h3l2 6 4-14 2 8h7" /></Icon>
const IconUser = () => <Icon><circle cx="12" cy="8" r="4" /><path d="M4 21a8 8 0 0 1 16 0" /></Icon>
const IconNav = () => <Icon><path d="M4 6h16M4 12h16M4 18h10" /><circle cx="18" cy="18" r="2.5" /></Icon>
const IconPalette = () => <Icon><path d="M12 3a9 9 0 1 0 0 18 2 2 0 0 0 1.6-3.2 2 2 0 0 1 1.6-3.2H18a3 3 0 0 0 3-3 9 9 0 0 0-9-8.6z" /><circle cx="7.5" cy="11.5" r="1" /><circle cx="10.5" cy="7.5" r="1" /><circle cx="15" cy="8.5" r="1" /></Icon>
const IconModules = () => <Icon><path d="M12 3l8 4.5-8 4.5-8-4.5z" /><path d="M4 12l8 4.5 8-4.5" /><path d="M4 16.5L12 21l8-4.5" /></Icon>

// Nav is grouped into collapsible categories. A group with no `title` renders
// its items ungrouped (Dashboard at top, Account at bottom). Each item's `roles`
// (when present) matches server-side enforcement so the sidebar never shows a
// link that would 403; an item without `roles` is visible to everyone.
// Moderators are further confined to just their section + account (see below).
//
// Exported because Admin -> Navigation edits this list. It stays declared here:
// the editor may relabel, reorder, hide and regroup, and `roles` is never its to
// touch (§7) — navItemVisibleTo below is the filter that still decides.
export const NAV = [
  {
    items: [
      { to: '/admin', label: 'Dashboard', end: true, icon: IconHome, roles: ['admin', 'editor', 'moderator'] },
    ],
  },
  {
    title: 'Content',
    items: [
      { to: '/admin/posts', label: 'Posts', icon: IconPosts, roles: ['admin', 'editor'] },
      { to: '/admin/pages', label: 'Pages', icon: IconPages, roles: ['admin', 'editor'] },
      { to: '/admin/wiki', label: 'Wiki', icon: IconWiki, roles: ['admin', 'editor'] },
      { to: '/admin/activity', label: 'Activity', icon: IconActivity, roles: ['admin', 'editor'] },
    ],
  },
  {
    title: 'Moderation',
    items: [
      { to: '/admin/moderation', label: 'Moderation', icon: IconShield, roles: ['admin', 'moderator'] },
      { to: '/admin/moderation/appeals', label: 'Appeals', icon: IconShield, roles: ['admin', 'moderator'] },
    ],
  },
  {
    title: 'System',
    items: [
      { to: '/admin/users', label: 'Users', icon: IconUsers, roles: ['admin'] },
      { to: '/admin/invites', label: 'Invites', icon: IconUsers, roles: ['admin'] },
      { to: '/admin/settings', label: 'Settings', icon: IconGear, roles: ['admin'] },
      // Admin-only, matching the server: every route under /admin/modules
      // re-gates to `admin` on top of the group's staff gate, because installing
      // a module runs its code in this process.
      { to: '/admin/modules', label: 'Modules', icon: IconModules, roles: ['admin'] },
      { to: '/admin/appearance', label: 'Appearance', icon: IconPalette, roles: ['admin'] },
      { to: '/admin/navigation', label: 'Navigation', icon: IconNav, roles: ['admin'] },
      { to: '/admin/hero', label: 'Hero Editor', icon: IconHero, roles: ['admin'] },
      { to: '/admin/auth-providers', label: 'Authentication', icon: IconKey, roles: ['admin'] },
      { to: '/admin/discord-bot', label: 'Discord Bot', icon: IconBot, roles: ['admin'] },
      { to: '/admin/bot-activity', label: 'Web Bot Activity', icon: IconPulse, roles: ['admin'] },
    ],
  },
  {
    items: [
      { to: '/admin/account', label: 'Account', icon: IconUser },
    ],
  },
]

const COLLAPSE_KEY = 'admin.nav.collapsed'

// The one row an override may never hide: the nav editor itself, which is the
// only screen that can un-hide anything. The write path already refuses it
// (server/src/utils/navOverrides.js) and the editor's own toggle is disabled —
// this is the third guard, and the one that also covers a row edited straight
// in the database. Cheap, and it makes "cannot be hidden" true without
// qualification.
const UNHIDEABLE = '/admin/navigation'

function keepEditorReachable(overrides) {
  const entry = overrides?.[UNHIDEABLE]
  if (!entry || entry.hidden !== true) return overrides
  const { hidden, ...rest } = entry
  return { ...overrides, [UNHIDEABLE]: rest }
}

// Who may see a sidebar row, and where that lets them go, both derived from the
// row's own `roles` — lib/adminNav.js, which is where the two hardcoded path
// lists this component used to carry went (MODULE_SYSTEM.md §1.4). Re-exported
// because Admin -> Navigation has always imported it from here.
export { navItemVisibleTo }

const TITLES = {
  '/admin': 'Dashboard',
  '/admin/posts': 'Posts',
  '/admin/pages': 'Pages',
  '/admin/wiki': 'Wiki Pages',
  '/admin/hero': 'Hero Editor',
  '/admin/moderation': 'Moderation',
  '/admin/moderation/appeals': 'Appeals',
  '/admin/settings': 'Site Settings',
  '/admin/appearance': 'Appearance',
  '/admin/navigation': 'Navigation',
  '/admin/activity': 'Activity Log',
  '/admin/bot-activity': 'Web Bot Activity',
  '/admin/discord-bot': 'Discord Bot',
  '/admin/auth-providers': 'Authentication',
  '/admin/users': 'Users',
  '/admin/invites': 'Invites',
  '/admin/account': 'Account Security',
}

// An installed module's admin pages are not in TITLES and cannot be — core does
// not know what they are called. Their nav row does, so the row is the title:
// the longest matching module row wins, so a detail page under a section titles
// as that section rather than falling through to a bare "Admin". Restricted to
// rows a module registered, which is what keeps every core path resolving
// through TITLES and sectionTitle exactly as it does today.
function moduleTitle(baseNav, pathname) {
  return baseNav
    .flatMap((g) => g.items)
    .filter((i) => i.moduleId && (pathname === i.to || pathname.startsWith(`${i.to}/`)))
    .sort((a, b) => b.to.length - a.to.length)[0]?.label
}

// Fallback page title for dynamic sub-routes not in the exact-match TITLES map.
function sectionTitle(pathname) {
  if (pathname.startsWith('/admin/moderation')) return 'Moderation'
  if (pathname.startsWith('/admin/users/')) return 'User'
  return 'Admin'
}

const navBtnBase = {
  textAlign: 'left',
  borderRadius: 8,
  padding: '10px 14px',
  fontFamily: 'var(--sans)',
  fontSize: '0.92rem',
  textDecoration: 'none',
  display: 'flex',
  alignItems: 'center',
  gap: 10,
  transition: 'background .15s,color .15s',
}

export default function AdminLayout() {
  const { user, logout } = useAuth()
  const { mode, siteTitle } = useSite()
  const navOverrides = useNavOverrides()
  const navigate = useNavigate()
  const location = useLocation()
  const isVisible = useFeatureGate()

  // Core's rows plus every installed module's, before the override merge sees
  // them — so a module row is editable in Admin -> Navigation like any other
  // (modules/nav.js). Computed once: the registry is fixed before the first
  // render and nothing unregisters.
  const baseNav = useMemo(() => withModuleNav(NAV, 'admin'), [])
  const title =
    TITLES[location.pathname] || moduleTitle(baseNav, location.pathname) || sectionTitle(location.pathname)
  // The hero canvas editor needs room — let it use the full content width.
  const wide = location.pathname === '/admin/hero'
  const modeDot = mode === 'live' ? 'var(--mode-live)' : 'var(--mode-maint)'

  const isModerator = user?.role === 'moderator'

  // An admin may relabel, reorder, hide and regroup these rows from Admin →
  // Navigation. The merge runs FIRST and the role filter after it, so the filter
  // stays the boundary: an override cannot show a moderator a row their role
  // gate hides, whatever it says. With no stored row applyNavOverrides returns
  // NAV itself and this is exactly the code that ran before the feature.
  const navGroups = useMemo(
    () =>
      applyNavOverrides(baseNav, keepEditorReachable(navOverrides.nav_admin))
        .map((g) => ({
          ...g,
          // `isVisible` is a no-op for every core row — none carries a `feature`
          // — and is applied here so that a module row which does carry one is
          // gated on the sidebar rather than silently advertised.
          items: g.items.filter((item) => navItemVisibleTo(item, user?.role) && isVisible(item)),
        }))
        // Drop any now-empty group so an empty category header never renders.
        .filter((g) => g.items.length > 0),
    [baseNav, navOverrides.nav_admin, user?.role, isVisible],
  )

  // Accordion: track which titled categories are collapsed. Persist across
  // reloads; default all-open. The group holding the active route auto-opens.
  const [collapsed, setCollapsed] = useState(() => {
    try {
      return JSON.parse(localStorage.getItem(COLLAPSE_KEY)) || {}
    } catch {
      return {}
    }
  })
  const toggleGroup = (title) => {
    setCollapsed((prev) => {
      const next = { ...prev, [title]: !prev[title] }
      try {
        localStorage.setItem(COLLAPSE_KEY, JSON.stringify(next))
      } catch {
        /* private mode / quota — collapse is non-essential */
      }
      return next
    })
  }
  const activeGroupTitle = navGroups.find((g) =>
    g.title && g.items.some((i) => (i.end ? location.pathname === i.to : location.pathname.startsWith(i.to)))
  )?.title

  // Where a moderator may go, from the same `roles` that decide what they see.
  // It used to be a third hardcoded list — a prefix check over three paths —
  // which disagreed with the sidebar's own five-path allowlist: `/admin/houses`
  // was on the sidebar and not in the redirect, so a moderator who clicked
  // Houses in their own nav was bounced straight back to Moderation. One
  // derivation cannot disagree with itself, which is the point of deriving it.
  const allowed = useMemo(() => allowedPathsFor(baseNav, user?.role), [baseNav, user?.role])

  // Confine a moderator who deep-links (or is redirected to the index) to a page
  // outside their remit — the API would 403 anyway, so send them to their home.
  useEffect(() => {
    if (!isModerator) return
    if (!isAllowedPath(location.pathname, allowed)) {
      navigate('/admin/moderation', { replace: true })
    }
  }, [isModerator, location.pathname, navigate, allowed])

  // Keep the admin out of search indexes (belt-and-suspenders with robots.txt).
  useEffect(() => {
    const meta = document.createElement('meta')
    meta.name = 'robots'
    meta.content = 'noindex, nofollow'
    document.head.appendChild(meta)
    return () => document.head.removeChild(meta)
  }, [])

  async function signOut() {
    await logout()
    navigate('/admin/login', { replace: true })
  }

  return (
    <div className="admin-grid">
      {/* Sidebar */}
      <aside
        style={{
          borderRight: '1px solid var(--line)',
          background: 'var(--bg)',
          display: 'flex',
          flexDirection: 'column',
          position: 'sticky',
          top: 0,
          height: '100vh',
        }}
      >
        <div style={{ padding: '22px 22px 18px', borderBottom: '1px solid var(--line-soft)', display: 'flex', alignItems: 'center', gap: 10 }}>
          <BrandLogo height={24} />
          <MoonDot />
          <div>
            <div className="display" style={{ fontSize: '1.02rem', color: 'var(--head)', letterSpacing: '0.03em' }}>
              {siteTitle}
            </div>
            <div className="sans" style={{ color: 'var(--dim)', fontSize: '0.66rem', letterSpacing: '0.14em', textTransform: 'uppercase' }}>
              Admin
            </div>
          </div>
        </div>

        <nav style={{ flex: 1, padding: '14px 12px', display: 'flex', flexDirection: 'column', gap: 4, overflowY: 'auto' }}>
          {navGroups.map((group) => {
            const links = group.items.map((n) => (
              <NavLink
                key={n.to}
                to={n.to}
                end={n.end}
                className="admin-nav-link"
                style={({ isActive }) => ({
                  ...navBtnBase,
                  background: isActive ? 'var(--blue)' : 'transparent',
                  color: isActive ? 'var(--ink)' : 'var(--muted)',
                  borderLeft: `2px solid ${isActive ? 'var(--accent)' : 'transparent'}`,
                })}
              >
                {n.icon && <n.icon />}
                <span>{n.label}</span>
              </NavLink>
            ))

            // Untitled groups (Dashboard, Account) render their links directly.
            if (!group.title) {
              return (
                <div key={group.items[0]?.to || 'group'} style={{ display: 'flex', flexDirection: 'column', gap: 4 }}>
                  {links}
                </div>
              )
            }

            // Titled groups get a collapsible header. The group with the active
            // route stays open regardless of the stored collapse preference.
            const isOpen = group.title === activeGroupTitle || !collapsed[group.title]
            return (
              <div key={group.title} className="admin-nav-group">
                <button
                  type="button"
                  className="admin-nav-head sans"
                  onClick={() => toggleGroup(group.title)}
                  aria-expanded={isOpen}
                >
                  <span>{group.title}</span>
                  <svg
                    className="admin-nav-chev"
                    width="12"
                    height="12"
                    viewBox="0 0 24 24"
                    fill="none"
                    stroke="currentColor"
                    strokeWidth="2.5"
                    strokeLinecap="round"
                    strokeLinejoin="round"
                    style={{ transform: isOpen ? 'rotate(0deg)' : 'rotate(-90deg)' }}
                    aria-hidden="true"
                  >
                    <path d="M6 9l6 6 6-6" />
                  </svg>
                </button>
                {isOpen && (
                  <div className="admin-nav-items" style={{ display: 'flex', flexDirection: 'column', gap: 4 }}>
                    {links}
                  </div>
                )}
              </div>
            )
          })}
        </nav>

        <div style={{ padding: '14px 16px', borderTop: '1px solid var(--line-soft)' }}>
          <div className="sans" style={{ display: 'flex', alignItems: 'center', gap: 8, marginBottom: 12, fontSize: '0.78rem', color: 'var(--muted)' }}>
            <span style={{ width: 9, height: 9, borderRadius: '50%', background: modeDot, boxShadow: `0 0 8px ${modeDot}` }} />
            Site is&nbsp;<strong style={{ color: 'var(--ink)', textTransform: 'capitalize' }}>{mode}</strong>
          </div>
          <button
            onClick={signOut}
            className="sans"
            style={{ display: 'block', width: '100%', textAlign: 'center', border: '1px solid var(--line)', borderRadius: 8, padding: 9, color: 'var(--muted)', background: 'transparent', fontSize: '0.84rem', cursor: 'pointer' }}
          >
            Sign out
          </button>
        </div>
      </aside>

      {/* Main */}
      <main style={{ display: 'flex', flexDirection: 'column', minWidth: 0 }}>
        <header
          style={{
            display: 'flex',
            alignItems: 'center',
            justifyContent: 'space-between',
            gap: 16,
            padding: '20px 32px',
            borderBottom: '1px solid var(--line-soft)',
            background: 'var(--bg)',
            position: 'sticky',
            top: 0,
            zIndex: 10,
          }}
        >
          <h1 className="display" style={{ margin: 0, fontSize: '1.5rem', color: 'var(--head)' }}>
            {title}
          </h1>
          <div className="sans" style={{ display: 'flex', alignItems: 'center', gap: 14, fontSize: '0.84rem', color: 'var(--muted)' }}>
            <a href="/" target="_blank" rel="noreferrer" style={{ color: 'var(--accent)', textDecoration: 'none' }}>
              View site →
            </a>
            <span
              style={{ width: 30, height: 30, borderRadius: '50%', background: 'linear-gradient(180deg,#2a3a52,#1a2536)', border: '1px solid var(--line)', display: 'flex', alignItems: 'center', justifyContent: 'center', color: '#d8e2ef', fontSize: '0.8rem', textTransform: 'uppercase' }}
            >
              {(user?.username || 'A').charAt(0)}
            </span>
          </div>
        </header>

        <div style={{ flex: 1, padding: '30px 32px 60px', maxWidth: wide ? 'none' : 1000, width: '100%' }}>
          <Outlet />
        </div>
      </main>
    </div>
  )
}