import { useState, useEffect, useCallback } from 'react'
import { Copy, Check, Globe, Users, Clock, Trash2, Link2 } from 'lucide-react'
import type { SessionShare, SessionShareVisibility } from '@/types'
import { analytics } from '@/lib/analytics'
import { sessionsApi } from '@/api/sessions'
import { buildSessionShareUrl, filterSharesForSession } from '@/lib/sessionShare'
import { cn } from '@/lib/utils'
import { toast } from '@/lib/toast'
import { Spinner } from '@/components/common/Spinner'
import { Modal } from '@/components/common/Modal'
import { Button } from '@/components/ui/Button'
import { Input } from '@/components/ui/Input'

interface ShareSessionModalProps {
  sessionId: string
  sessionLabel: string
  isOpen: boolean
  onClose: () => void
}

type ExpirationPreset = 'never' | '1day' | '7days' | '30days' | 'custom'

function getRelativeTime(dateString: string): string {
  const now = Date.now()
  const date = new Date(dateString).getTime()
  const diffMs = now - date
  const diffSeconds = Math.floor(diffMs / 1000)
  const diffMinutes = Math.floor(diffSeconds / 60)
  const diffHours = Math.floor(diffMinutes / 60)
  const diffDays = Math.floor(diffHours / 24)

  if (diffSeconds < 60) return 'just now'
  if (diffMinutes < 60) return `${diffMinutes} minute${diffMinutes === 1 ? '' : 's'} ago`
  if (diffHours < 24) return `${diffHours} hour${diffHours === 1 ? '' : 's'} ago`
  if (diffDays < 30) return `${diffDays} day${diffDays === 1 ? '' : 's'} ago`
  const diffMonths = Math.floor(diffDays / 30)
  return `${diffMonths} month${diffMonths === 1 ? '' : 's'} ago`
}

function getExpirationLabel(expiresAt: string | null): { text: string; isExpired: boolean } {
  if (!expiresAt) return { text: 'No expiration', isExpired: false }
  const now = Date.now()
  const expiry = new Date(expiresAt).getTime()
  if (expiry <= now) return { text: 'Expired', isExpired: true }

  const diffMs = expiry - now
  const diffHours = Math.floor(diffMs / (1000 * 60 * 60))
  const diffDays = Math.floor(diffHours / 24)

  if (diffDays > 0) return { text: `Expires in ${diffDays} day${diffDays === 1 ? '' : 's'}`, isExpired: false }
  if (diffHours > 0) return { text: `Expires in ${diffHours} hour${diffHours === 1 ? '' : 's'}`, isExpired: false }
  return { text: 'Expires soon', isExpired: false }
}

function computeExpiresAt(preset: ExpirationPreset, customDatetime: string): string | undefined {
  if (preset === 'never') return undefined
  if (preset === 'custom') {
    if (!customDatetime) return undefined
    return new Date(customDatetime).toISOString()
  }

  const now = new Date()
  switch (preset) {
    case '1day':
      now.setDate(now.getDate() + 1)
      break
    case '7days':
      now.setDate(now.getDate() + 7)
      break
    case '30days':
      now.setDate(now.getDate() + 30)
      break
  }
  return now.toISOString()
}

export function ShareSessionModal({ sessionId, sessionLabel, isOpen, onClose }: ShareSessionModalProps) {
  const [shares, setShares] = useState<SessionShare[]>([])
  const [isLoadingShares, setIsLoadingShares] = useState(false)
  const [isGenerating, setIsGenerating] = useState(false)
  const [copiedShareId, setCopiedShareId] = useState<string | null>(null)

  const [visibility, setVisibility] = useState<SessionShareVisibility>('account')
  const [shareName, setShareName] = useState('')
  const [expirationPreset, setExpirationPreset] = useState<ExpirationPreset>('never')
  const [customDatetime, setCustomDatetime] = useState('')
  const [visibilityError, setVisibilityError] = useState<string | null>(null)

  const loadShares = useCallback(async () => {
    setIsLoadingShares(true)
    try {
      const allShares = await sessionsApi.listMyShares()
      const sessionShares = filterSharesForSession(allShares, sessionId)
      sessionShares.sort((a, b) => new Date(b.created_at).getTime() - new Date(a.created_at).getTime())
      setShares(sessionShares)
    } catch (err) {
      console.error('Failed to load shares:', err)
    } finally {
      setIsLoadingShares(false)
    }
  }, [sessionId])

  useEffect(() => {
    if (isOpen) {
      loadShares()
      setVisibility('account')
      setShareName('')
      setExpirationPreset('never')
      setCustomDatetime('')
      setVisibilityError(null)
      setCopiedShareId(null)
    }
  }, [isOpen, sessionId, loadShares])

  const handleGenerateLink = async () => {
    setIsGenerating(true)
    setVisibilityError(null)
    try {
      const expires_at = computeExpiresAt(expirationPreset, customDatetime)
      const newShare = await sessionsApi.createShare(sessionId, {
        visibility,
        share_name: shareName.trim() || undefined,
        expires_at,
      })
      setShares([newShare, ...shares])
      analytics.sessionShared({ session_id: sessionId, visibility })
      toast.success('Share link generated')
      setShareName('')
      setExpirationPreset('never')
      setCustomDatetime('')
    } catch (err: unknown) {
      const error = err as { response?: { status?: number; data?: { detail?: string } } }
      if (
        error.response?.status === 403 &&
        error.response?.data?.detail?.toLowerCase().includes('public session sharing')
      ) {
        setVisibilityError(error.response.data.detail ?? 'Organization does not allow public session sharing')
      } else {
        console.error('Failed to generate share link:', err)
        toast.error('Failed to generate share link')
      }
    } finally {
      setIsGenerating(false)
    }
  }

  const handleCopyUrl = async (share: SessionShare) => {
    try {
      const url = buildSessionShareUrl(share)
      await navigator.clipboard.writeText(url)
      setCopiedShareId(share.id)
      toast.success('Link copied to clipboard')
      setTimeout(() => setCopiedShareId(null), 2000)
    } catch (err) {
      console.error('Failed to copy link:', err)
      toast.error('Failed to copy link')
    }
  }

  const handleRevoke = async (shareId: string) => {
    try {
      await sessionsApi.revokeShare(shareId)
      setShares(shares.filter((s) => s.id !== shareId))
      toast.success('Share link revoked')
    } catch (err) {
      console.error('Failed to revoke share:', err)
      toast.error('Failed to revoke share')
    }
  }

  const presetButtons: { value: ExpirationPreset; label: string }[] = [
    { value: 'never', label: 'Never' },
    { value: '1day', label: '1 day' },
    { value: '7days', label: '7 days' },
    { value: '30days', label: '30 days' },
    { value: 'custom', label: 'Custom' },
  ]

  return (
    <Modal
      isOpen={isOpen}
      onClose={onClose}
      title="Share Session"
      size="lg"
      footer={
        <div className="flex justify-end">
          <Button variant="secondary" onClick={onClose}>
            Close
          </Button>
        </div>
      }
    >
      {/* Subtitle */}
      <p className="-mt-2 mb-4 text-sm text-muted-foreground">{sessionLabel}</p>

      <div className="space-y-6">
        {/* Create Share Form */}
        <div className="space-y-4">
          {/* Visibility */}
          <div>
            <label className="mb-2 block text-sm font-medium text-foreground">
              Visibility
            </label>
            <div className="space-y-2">
              <button
                onClick={() => { setVisibility('account'); setVisibilityError(null) }}
                className={cn(
                  'flex w-full items-center gap-3 rounded-md border px-4 py-3 text-left transition-colors',
                  visibility === 'account'
                    ? 'border-primary/30 bg-accent-dim text-foreground'
                    : 'border-border bg-transparent text-muted-foreground hover:border-border hover:bg-accent'
                )}
              >
                <Users className="h-4 w-4" />
                <div className="flex-1">
                  <div className="text-sm font-medium">Account Only</div>
                  <div className="text-xs text-muted-foreground">Visible to your team</div>
                </div>
                {visibility === 'account' && (
                  <div className="h-2 w-2 rounded-full bg-primary" />
                )}
              </button>
              <button
                onClick={() => { setVisibility('public'); setVisibilityError(null) }}
                className={cn(
                  'flex w-full items-center gap-3 rounded-md border px-4 py-3 text-left transition-colors',
                  visibility === 'public'
                    ? 'border-primary/30 bg-accent-dim text-foreground'
                    : 'border-border bg-transparent text-muted-foreground hover:border-border hover:bg-accent'
                )}
              >
                <Globe className="h-4 w-4" />
                <div className="flex-1">
                  <div className="text-sm font-medium">Public</div>
                  <div className="text-xs text-muted-foreground">Anyone with the link</div>
                </div>
                {visibility === 'public' && (
                  <div className="h-2 w-2 rounded-full bg-primary" />
                )}
              </button>
            </div>
            {visibilityError && (
              <p className="mt-2 text-sm text-red-400">{visibilityError}</p>
            )}
          </div>

          {/* Share Name */}
          <div>
            <label className="mb-2 block text-sm font-medium text-foreground">
              Share Name <span className="text-muted-foreground">(optional)</span>
            </label>
            <Input
              type="text"
              value={shareName}
              onChange={(e) => setShareName(e.target.value.slice(0, 100))}
              placeholder="e.g. Training link, Customer escalation"
              maxLength={100}
            />
          </div>

          {/* Expiration */}
          <div>
            <label className="mb-2 block text-sm font-medium text-foreground">
              Expiration
            </label>
            <div className="flex flex-wrap gap-2">
              {presetButtons.map((preset) => (
                <button
                  key={preset.value}
                  onClick={() => setExpirationPreset(preset.value)}
                  className={cn(
                    'rounded-md border px-3 py-1.5 text-sm transition-colors',
                    expirationPreset === preset.value
                      ? 'border-primary/30 bg-accent-dim text-foreground'
                      : 'border-border text-muted-foreground hover:border-border hover:bg-accent'
                  )}
                >
                  {preset.label}
                </button>
              ))}
            </div>
            {expirationPreset === 'custom' && (
              <input
                type="datetime-local"
                value={customDatetime}
                onChange={(e) => setCustomDatetime(e.target.value)}
                className={cn(
                  'mt-2 w-full rounded-md border border-border bg-card px-3 py-2 text-sm text-foreground',
                  'focus:border-primary focus:outline-hidden focus:ring-1 focus:ring-primary/20',
                  'scheme-dark'
                )}
              />
            )}
          </div>

          {/* Generate Button */}
          <Button
            onClick={handleGenerateLink}
            disabled={expirationPreset === 'custom' && !customDatetime}
            loading={isGenerating}
            className="w-full"
          >
            <Link2 className="h-4 w-4" />
            Generate Link
          </Button>
        </div>

        {/* Existing Shares */}
        {shares.length > 0 && (
          <div>
            <h3 className="mb-3 text-sm font-medium text-foreground">
              Active Shares ({shares.length})
            </h3>
            <div className="space-y-3">
              {shares.map((share) => {
                const expiration = getExpirationLabel(share.expires_at)
                const isCopied = copiedShareId === share.id
                return (
                  <div
                    key={share.id}
                    className="bg-card border border-border rounded-lg p-4 space-y-2"
                  >
                    <div className="flex items-start justify-between gap-2">
                      <div className="flex-1 min-w-0">
                        <div className="flex items-center gap-2">
                          <span className={cn(
                            'inline-flex items-center gap-1 rounded-full px-2 py-0.5 text-xs',
                            share.visibility === 'public'
                              ? 'bg-accent text-muted-foreground'
                              : 'bg-accent text-muted-foreground'
                          )}>
                            {share.visibility === 'public' ? (
                              <Globe className="h-3 w-3" />
                            ) : (
                              <Users className="h-3 w-3" />
                            )}
                            {share.visibility === 'public' ? 'Public' : 'Account'}
                          </span>
                          <span className="truncate text-sm font-medium text-foreground">
                            {share.share_name || 'Untitled share'}
                          </span>
                        </div>
                        <div className="mt-1 flex flex-wrap items-center gap-x-3 gap-y-1 text-xs text-muted-foreground">
                          <span>{getRelativeTime(share.created_at)}</span>
                          <span>
                            {share.view_count > 0
                              ? `${share.view_count} view${share.view_count === 1 ? '' : 's'}`
                              : 'Not viewed yet'}
                          </span>
                          <span className={cn(
                            'flex items-center gap-1',
                            expiration.isExpired && 'text-red-400'
                          )}>
                            <Clock className="h-3 w-3" />
                            {expiration.text}
                          </span>
                        </div>
                      </div>
                      <div className="flex items-center gap-1 shrink-0">
                        <button
                          onClick={() => handleCopyUrl(share)}
                          title="Copy share URL"
                          className={cn(
                            'rounded-md border border-border p-1.5 text-sm transition-colors',
                            isCopied
                              ? 'border-emerald-500/30 bg-emerald-500/10 text-emerald-400'
                              : 'text-muted-foreground hover:bg-accent hover:text-foreground'
                          )}
                        >
                          {isCopied ? (
                            <Check className="h-3.5 w-3.5" />
                          ) : (
                            <Copy className="h-3.5 w-3.5" />
                          )}
                        </button>
                        <button
                          onClick={() => handleRevoke(share.id)}
                          title="Revoke share"
                          className="rounded-md border border-border p-1.5 text-muted-foreground hover:bg-red-500/10 hover:border-red-500/30 hover:text-red-400 transition-colors"
                        >
                          <Trash2 className="h-3.5 w-3.5" />
                        </button>
                      </div>
                    </div>
                  </div>
                )
              })}
            </div>
          </div>
        )}

        {/* Loading state */}
        {isLoadingShares && shares.length === 0 && (
          <div className="flex items-center justify-center py-4">
            <Spinner size="sm" className="h-5 w-5 border-t-foreground" />
          </div>
        )}
      </div>
    </Modal>
  )
}

export default ShareSessionModal
