import { useState, useEffect, useCallback } from 'react'
import { X, Copy, Check, Globe, Users, Clock, Trash2, Link2 } from 'lucide-react'
import type { SessionShare, SessionShareVisibility } from '@/types'
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'

interface ShareSessionModalProps {
  sessionId: string
  sessionLabel: string // e.g. ticket number or "Session Details"
  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)

  // Form state
  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)
      // Sort newest first
      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()
      // Reset form state
      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])
      toast.success('Share link generated')
      // Reset form
      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')
    }
  }

  if (!isOpen) return null

  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 (
    <div className="fixed inset-0 z-50 flex items-center justify-center">
      {/* Backdrop */}
      <div
        className="absolute inset-0 bg-black/80 backdrop-blur-sm"
        onClick={onClose}
      />

      {/* Modal */}
      <div className="relative w-full max-w-lg bg-card border border-border rounded-xl shadow-lg">
        {/* Header */}
        <div className="flex items-center justify-between border-b border-border px-6 py-4">
          <div>
            <h2 className="text-lg font-heading font-semibold text-foreground">Share Session</h2>
            <p className="text-sm text-muted-foreground">{sessionLabel}</p>
          </div>
          <button
            onClick={onClose}
            className="rounded-md p-1 text-muted-foreground hover:bg-accent hover:text-foreground"
          >
            <X className="h-5 w-5" />
          </button>
        </div>

        {/* Body */}
        <div className="max-h-[60vh] overflow-y-auto px-6 py-4 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-primary/10 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-primary/10 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"
                className={cn(
                  'w-full rounded-md border border-border bg-card px-3 py-2 text-sm text-foreground placeholder-muted-foreground',
                  'focus:border-primary focus:outline-none focus:ring-1 focus:ring-primary/20'
                )}
                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-primary/10 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-none focus:ring-1 focus:ring-primary/20',
                    '[color-scheme:dark]'
                  )}
                />
              )}
            </div>

            {/* Generate Button */}
            <button
              onClick={handleGenerateLink}
              disabled={isGenerating || (expirationPreset === 'custom' && !customDatetime)}
              className={cn(
                'flex w-full items-center justify-center gap-2 rounded-md bg-gradient-brand px-4 py-2 text-sm font-medium text-white shadow-lg shadow-primary/20',
                'hover:opacity-90 disabled:opacity-50 disabled:cursor-not-allowed'
              )}
            >
              <Link2 className="h-4 w-4" />
              {isGenerating ? 'Generating...' : '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-xl 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>

        {/* Footer */}
        <div className="flex justify-end gap-3 border-t border-border px-6 py-4">
          <button
            onClick={onClose}
            className={cn(
              'rounded-md border border-border px-4 py-2 text-sm font-medium text-muted-foreground',
              'hover:bg-accent hover:text-foreground'
            )}
          >
            Close
          </button>
        </div>
      </div>
    </div>
  )
}

export default ShareSessionModal
