import { useEffect, useState } from 'react'
import { useNavigate, useLocation } from 'react-router-dom'
import { LayoutGrid, Box, PenLine, Clock, FileText, Bookmark, BarChart3, Settings, PanelLeftClose, PanelLeftOpen, MessageSquareText } from 'lucide-react'
import { cn } from '@/lib/utils'
import { useUserPreferencesStore } from '@/store/userPreferencesStore'
import { CategoryList } from '@/components/sidebar/CategoryList'
import { TagCloud } from '@/components/sidebar/TagCloud'
import { PinnedFlowsSection } from '@/components/sidebar/PinnedFlowsSection'
import { NavItem } from './NavItem'
import { categoriesApi, tagsApi, sessionsApi, treesApi } from '@/api'
import { pinnedFlowsApi } from '@/api/pinnedFlows'
import type { PinnedFlow } from '@/api/pinnedFlows'
import { toast } from '@/lib/toast'

interface CategoryItem {
  id: string
  name: string
  color: string
  count: number
}

export function Sidebar() {
  const sidebarCollapsed = useUserPreferencesStore(s => s.sidebarCollapsed)
  const toggleSidebar = useUserPreferencesStore(s => s.toggleSidebar)

  const [categories, setCategories] = useState<CategoryItem[]>([])
  const [tags, setTags] = useState<string[]>([])
  const [activeCategoryId, setActiveCategoryId] = useState<string | null>(null)
  const [activeTags, setActiveTags] = useState<string[]>([])
  const [activeSessionCount, setActiveSessionCount] = useState(0)
  const [pinnedFlows, setPinnedFlows] = useState<PinnedFlow[]>([])
  const [treeCounts, setTreeCounts] = useState({ total: 0, troubleshooting: 0, procedural: 0, maintenance: 0 })

  // Fetch sidebar data on mount
  useEffect(() => {
    const fetchData = async () => {
      try {
        const [cats, tagList, activeSessions, allTrees, pinnedData] = await Promise.all([
          categoriesApi.list(),
          tagsApi.list().catch(() => []),
          sessionsApi.list({ completed: false, size: 50 }).catch(() => []),
          treesApi.list({ sort_by: 'name' }).catch(() => []),
          pinnedFlowsApi.list().catch(() => ({ items: [], count: 0 })),
        ])
        setCategories(cats.map(c => ({
          id: c.id,
          name: c.name,
          color: c.color || '#3b82f6',
          count: c.tree_count || 0,
        })))
        setTags(tagList.map((t: { name: string }) => t.name).slice(0, 15))
        setActiveSessionCount(activeSessions.length)
        setPinnedFlows(pinnedData.items)

        const total = allTrees.length
        const troubleshooting = allTrees.filter(t => t.tree_type === 'troubleshooting').length
        const procedural = allTrees.filter(t => t.tree_type === 'procedural').length
        const maintenance = allTrees.filter(t => t.tree_type === 'maintenance').length
        setTreeCounts({ total, troubleshooting, procedural, maintenance })
      } catch {
        // Silently handle errors
      }
    }
    fetchData()
  }, [])

  const navigate = useNavigate()
  const location = useLocation()

  // Sync active filters from URL when on /trees page
  useEffect(() => {
    if (location.pathname === '/trees') {
      const params = new URLSearchParams(location.search)
      setActiveCategoryId(params.get('category') || null)
      const tagsParam = params.get('tags')
      setActiveTags(tagsParam ? tagsParam.split(',') : [])
    }
  }, [location.pathname, location.search])

  const handleCategorySelect = (id: string | null) => {
    setActiveCategoryId(id)
    const params = new URLSearchParams(location.search)
    if (id) {
      params.set('category', id)
    } else {
      params.delete('category')
    }
    navigate(`/trees?${params.toString()}`)
  }

  const handleTagClick = (tag: string) => {
    const next = activeTags.includes(tag)
      ? activeTags.filter(t => t !== tag)
      : [...activeTags, tag]
    setActiveTags(next)
    const params = new URLSearchParams(location.search)
    if (next.length > 0) {
      params.set('tags', next.join(','))
    } else {
      params.delete('tags')
    }
    navigate(`/trees?${params.toString()}`)
  }

  const handleUnpin = async (treeId: string) => {
    try {
      await pinnedFlowsApi.unpin(treeId)
      setPinnedFlows(prev => prev.filter(f => f.tree_id !== treeId))
      toast.success('Unpinned from sidebar')
    } catch {
      toast.error('Failed to unpin flow')
    }
  }

  const handleSidebarWheel = (e: React.WheelEvent<HTMLElement>) => {
    const sidebar = e.currentTarget
    const canSidebarScroll = sidebar.scrollHeight > sidebar.clientHeight
    const atTop = sidebar.scrollTop <= 0
    const atBottom = sidebar.scrollTop + sidebar.clientHeight >= sidebar.scrollHeight - 1

    // If sidebar can't consume wheel movement, forward it to main content scroller.
    if (!canSidebarScroll || (e.deltaY < 0 && atTop) || (e.deltaY > 0 && atBottom)) {
      const main = document.querySelector('.main-content') as HTMLElement | null
      if (main) {
        main.scrollTop += e.deltaY
        e.preventDefault()
      }
    }
  }

  return (
    <nav
      className="sidebar flex flex-col border-r border-border bg-[hsl(var(--sidebar-bg))]"
      onWheel={handleSidebarWheel}
    >
      {sidebarCollapsed ? (
        <>
          {/* Collapsed: icon-only nav */}
          <div className="flex flex-col items-center px-1.5 py-3 space-y-1">
            <NavItem href="/" icon={LayoutGrid} label="Dashboard" collapsed />
            <NavItem href="/trees" icon={Box} label="All Flows" matchPaths={['/trees', '/flows']} collapsed />
            <NavItem href="/my-trees" icon={PenLine} label="Flow Editor" collapsed />
            <NavItem href="/sessions" icon={Clock} label="Sessions" badge={activeSessionCount || undefined} collapsed />
            <NavItem href="/shares" icon={FileText} label="Exports" collapsed />
            <NavItem href="/step-library" icon={Bookmark} label="Step Library" collapsed />
            <NavItem href="/analytics" icon={BarChart3} label="Analytics" collapsed />
            <NavItem href="/feedback" icon={MessageSquareText} label="Feedback" collapsed />
          </div>
        </>
      ) : (
        <>
          {/* Pinned Flows */}
          <PinnedFlowsSection flows={pinnedFlows} onUnpin={handleUnpin} />

          <div className="border-b border-[hsl(var(--border-subtle))]" />

          {/* Primary Navigation */}
          <div className="px-3 py-2 space-y-0.5">
            <NavItem href="/" icon={LayoutGrid} label="Dashboard" />
            <NavItem
              href="/trees"
              icon={Box}
              label="All Flows"
              badge={treeCounts.total || undefined}
              matchPaths={['/trees', '/flows']}
              children={[
                { href: '/trees?type=troubleshooting', label: 'Troubleshooting', count: treeCounts.troubleshooting || undefined },
                { href: '/trees?type=procedural', label: 'Projects', count: treeCounts.procedural || undefined },
                { href: '/trees?type=maintenance', label: 'Maintenance', count: treeCounts.maintenance || undefined },
              ]}
            />
            <NavItem href="/my-trees" icon={PenLine} label="Flow Editor" />
            <NavItem href="/sessions" icon={Clock} label="Sessions" badge={activeSessionCount || undefined} />
            <NavItem href="/shares" icon={FileText} label="Exports" />
            <NavItem href="/step-library" icon={Bookmark} label="Step Library" />
            <NavItem href="/analytics" icon={BarChart3} label="Analytics" />
          </div>

          <div className="border-b border-[hsl(var(--border-subtle))]" />

          {/* Categories */}
          <CategoryList
            categories={categories}
            activeId={activeCategoryId}
            onSelect={handleCategorySelect}
          />

          <div className="border-b border-[hsl(var(--border-subtle))]" />

          {/* Tags */}
          <TagCloud tags={tags} activeTags={activeTags} onTagClick={handleTagClick} />
        </>
      )}

      {/* Spacer */}
      <div className="flex-1" />

      {/* Footer */}
      <div className={cn(
        "border-t border-[hsl(var(--border-subtle))]",
        sidebarCollapsed ? "px-1.5 py-2 flex flex-col items-center" : "px-3 py-2 space-y-0.5"
      )}>
        {!sidebarCollapsed && (
          <>
            <NavItem href="/feedback" icon={MessageSquareText} label="Feedback" />
            <NavItem href="/account" icon={Settings} label="Account" />
          </>
        )}
        <button
          onClick={toggleSidebar}
          className={cn(
            "flex w-full items-center rounded-lg text-[0.8125rem] font-medium text-muted-foreground hover:bg-[hsl(var(--sidebar-hover))] hover:text-foreground transition-colors",
            sidebarCollapsed ? "justify-center p-2.5" : "gap-3 px-3 py-2"
          )}
          title={sidebarCollapsed ? 'Expand sidebar' : 'Collapse sidebar'}
        >
          {sidebarCollapsed ? <PanelLeftOpen size={20} /> : <PanelLeftClose size={18} />}
          {!sidebarCollapsed && <span>Collapse</span>}
        </button>
      </div>
    </nav>
  )
}