"use client"

import { useState, useEffect, useCallback } from "react"
import { Card, CardContent, CardHeader, CardTitle, CardDescription } from "@/components/ui/card"
import { Button } from "@/components/ui/button"
import { Input } from "@/components/ui/input"
import { Label } from "@/components/ui/label"
import { Badge } from "@/components/ui/badge"
import {
  Building2, CreditCard, Palette, Check, Loader2, AlertCircle,
  MessageCircle, Radio, QrCode, RefreshCw, Smartphone, Wifi, WifiOff
} from "lucide-react"

interface OrgSettings {
  name: string
  bankName: string
  bankSortCode: string
  bankAccountNo: string
  bankAccountName: string
  refPrefix: string
  primaryColor: string
  gcAccessToken: string
  gcEnvironment: string
  orgType: string
}

export default function SettingsPage() {
  const [settings, setSettings] = useState<OrgSettings | null>(null)
  const [loading, setLoading] = useState(true)
  const [saving, setSaving] = useState<string | null>(null)
  const [saved, setSaved] = useState<string | null>(null)
  const [error, setError] = useState<string | null>(null)

  useEffect(() => {
    fetch("/api/settings")
      .then((r) => r.json())
      .then((data) => { if (data.name) setSettings(data) })
      .catch(() => setError("Failed to load settings"))
      .finally(() => setLoading(false))
  }, [])

  const save = async (section: string, data: Record<string, string>) => {
    setSaving(section)
    setError(null)
    try {
      const res = await fetch("/api/settings", {
        method: "PATCH",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(data),
      })
      if (res.ok) { setSaved(section); setTimeout(() => setSaved(null), 2000) }
      else setError("Failed to save")
    } catch { setError("Failed to save") }
    setSaving(null)
  }

  if (loading) return <div className="flex items-center justify-center py-20"><Loader2 className="h-8 w-8 text-trust-blue animate-spin" /></div>
  if (!settings) return <div className="text-center py-20"><AlertCircle className="h-8 w-8 text-danger-red mx-auto mb-2" /><p className="text-muted-foreground">Failed to load settings</p></div>

  const update = (key: keyof OrgSettings, value: string) => setSettings((s) => s ? { ...s, [key]: value } : s)

  return (
    <div className="space-y-6 max-w-2xl">
      <div>
        <h1 className="text-2xl font-black text-gray-900">Settings</h1>
        <p className="text-sm text-muted-foreground mt-0.5">Configure your organisation&apos;s payment details and integrations</p>
      </div>

      {error && <div className="rounded-lg bg-danger-red/10 border border-danger-red/20 p-3 text-sm text-danger-red">{error}</div>}

      {/* WhatsApp — MOST IMPORTANT, first */}
      <WhatsAppPanel />

      {/* Bank Details */}
      <Card>
        <CardHeader>
          <CardTitle className="text-base flex items-center gap-2"><Building2 className="h-4 w-4 text-trust-blue" /> Bank Account</CardTitle>
          <CardDescription className="text-xs">Shown to donors who choose bank transfer. Each pledge gets a unique reference.</CardDescription>
        </CardHeader>
        <CardContent className="space-y-4">
          <div className="grid grid-cols-2 gap-3">
            <div><Label className="text-xs">Bank Name</Label><Input value={settings.bankName} onChange={(e) => update("bankName", e.target.value)} placeholder="e.g. Barclays" /></div>
            <div><Label className="text-xs">Account Name</Label><Input value={settings.bankAccountName} onChange={(e) => update("bankAccountName", e.target.value)} /></div>
          </div>
          <div className="grid grid-cols-2 gap-3">
            <div><Label className="text-xs">Sort Code</Label><Input value={settings.bankSortCode} onChange={(e) => update("bankSortCode", e.target.value)} placeholder="20-30-80" /></div>
            <div><Label className="text-xs">Account Number</Label><Input value={settings.bankAccountNo} onChange={(e) => update("bankAccountNo", e.target.value)} placeholder="12345678" /></div>
          </div>
          <div><Label className="text-xs">Reference Prefix</Label><Input value={settings.refPrefix} onChange={(e) => update("refPrefix", e.target.value)} maxLength={4} className="w-24" /><p className="text-[10px] text-muted-foreground mt-1">e.g. {settings.refPrefix}-XXXX-50</p></div>
          <Button size="sm" onClick={() => save("bank", { bankName: settings.bankName, bankSortCode: settings.bankSortCode, bankAccountNo: settings.bankAccountNo, bankAccountName: settings.bankAccountName, refPrefix: settings.refPrefix })} disabled={saving === "bank"}>
            {saving === "bank" ? <><Loader2 className="h-3.5 w-3.5 mr-1.5 animate-spin" /> Saving</> : saved === "bank" ? <><Check className="h-3.5 w-3.5 mr-1.5" /> Saved!</> : "Save Bank Details"}
          </Button>
        </CardContent>
      </Card>

      {/* GoCardless */}
      <Card>
        <CardHeader>
          <CardTitle className="text-base flex items-center gap-2"><CreditCard className="h-4 w-4 text-trust-blue" /> GoCardless (Direct Debit)</CardTitle>
          <CardDescription className="text-xs">Enable Direct Debit collection protected by the DD Guarantee.</CardDescription>
        </CardHeader>
        <CardContent className="space-y-4">
          <div><Label className="text-xs">Access Token</Label><Input type="password" value={settings.gcAccessToken} onChange={(e) => update("gcAccessToken", e.target.value)} placeholder="sandbox_xxxxx or live_xxxxx" /></div>
          <div>
            <Label className="text-xs">Environment</Label>
            <div className="flex gap-2 mt-1">
              {["sandbox", "live"].map((env) => (
                <button key={env} onClick={() => update("gcEnvironment", env)} className={`px-3 py-1.5 rounded-lg text-xs font-medium border-2 transition-colors ${settings.gcEnvironment === env ? env === "live" ? "border-danger-red bg-danger-red/5 text-danger-red" : "border-trust-blue bg-trust-blue/5 text-trust-blue" : "border-gray-200 text-muted-foreground"}`}>
                  {env.charAt(0).toUpperCase() + env.slice(1)} {env === "live" && settings.gcEnvironment === "live" && "⚠️"}
                </button>
              ))}
            </div>
          </div>
          <Button size="sm" onClick={() => save("gc", { gcAccessToken: settings.gcAccessToken, gcEnvironment: settings.gcEnvironment })} disabled={saving === "gc"}>
            {saving === "gc" ? <><Loader2 className="h-3.5 w-3.5 mr-1.5 animate-spin" /> Saving</> : saved === "gc" ? <><Check className="h-3.5 w-3.5 mr-1.5" /> Saved!</> : "Save GoCardless"}
          </Button>
        </CardContent>
      </Card>

      {/* Branding */}
      <Card>
        <CardHeader>
          <CardTitle className="text-base flex items-center gap-2"><Palette className="h-4 w-4 text-trust-blue" /> Branding</CardTitle>
        </CardHeader>
        <CardContent className="space-y-4">
          <div><Label className="text-xs">Organisation Name</Label><Input value={settings.name} onChange={(e) => update("name", e.target.value)} /></div>
          <div>
            <Label className="text-xs">Primary Colour</Label>
            <div className="flex gap-2 mt-1"><Input type="color" value={settings.primaryColor} onChange={(e) => update("primaryColor", e.target.value)} className="w-12 h-9 p-0.5" /><Input value={settings.primaryColor} onChange={(e) => update("primaryColor", e.target.value)} className="flex-1" /></div>
          </div>
          <Button size="sm" onClick={() => save("brand", { name: settings.name, primaryColor: settings.primaryColor })} disabled={saving === "brand"}>
            {saving === "brand" ? <><Loader2 className="h-3.5 w-3.5 mr-1.5 animate-spin" /> Saving</> : saved === "brand" ? <><Check className="h-3.5 w-3.5 mr-1.5" /> Saved!</> : "Save Branding"}
          </Button>
        </CardContent>
      </Card>
    </div>
  )
}

// ─── WhatsApp Connection Panel ───────────────────────────────────

function WhatsAppPanel() {
  const [status, setStatus] = useState<string>("loading")
  const [qrImage, setQrImage] = useState<string | null>(null)
  const [phone, setPhone] = useState<string>("")
  const [pushName, setPushName] = useState<string>("")
  const [starting, setStarting] = useState(false)
  const [showQr, setShowQr] = useState(false) // only true after user clicks Connect

  const checkStatus = useCallback(async () => {
    try {
      const res = await fetch("/api/whatsapp/qr")
      const data = await res.json()
      setStatus(data.status)
      if (data.screenshot) setQrImage(data.screenshot)
      if (data.phone) setPhone(data.phone)
      if (data.pushName) setPushName(data.pushName)
      // Auto-show QR panel once connected (user paired successfully)
      if (data.status === "CONNECTED") setShowQr(false)
    } catch {
      setStatus("ERROR")
    }
  }, [])

  // On mount: just check if already connected. Don't start polling yet.
  useEffect(() => { checkStatus() }, [checkStatus])

  // Poll only when user has clicked Connect and we're waiting for scan
  useEffect(() => {
    if (!showQr) return
    const interval = setInterval(checkStatus, 5000)
    return () => clearInterval(interval)
  }, [showQr, checkStatus])

  const startSession = async () => {
    setStarting(true)
    setShowQr(true)
    try {
      await fetch("/api/whatsapp/qr", { method: "POST" })
      await new Promise(r => setTimeout(r, 3000))
      await checkStatus()
    } catch { /* ignore */ }
    setStarting(false)
  }

  if (status === "CONNECTED") {
    return (
      <Card className="border-[#25D366]/30 bg-[#25D366]/[0.02]">
        <CardHeader className="pb-3">
          <CardTitle className="text-base flex items-center gap-2">
            <MessageCircle className="h-4 w-4 text-[#25D366]" /> WhatsApp
            <Badge variant="success" className="gap-1 ml-1"><Radio className="h-2.5 w-2.5" /> Connected</Badge>
          </CardTitle>
        </CardHeader>
        <CardContent>
          <div className="flex items-center gap-4">
            <div className="w-12 h-12 rounded-lg bg-[#25D366]/10 flex items-center justify-center">
              <Smartphone className="h-6 w-6 text-[#25D366]" />
            </div>
            <div>
              <p className="font-medium text-sm">{pushName || "WhatsApp Business"}</p>
              <p className="text-xs text-muted-foreground">+{phone}</p>
            </div>
            <div className="ml-auto">
              <Wifi className="h-5 w-5 text-[#25D366]" />
            </div>
          </div>
          <div className="mt-4 pt-3 border-t border-[#25D366]/10 grid grid-cols-3 gap-3">
            <div className="text-center">
              <p className="text-[10px] text-muted-foreground">Auto-Sends</p>
              <p className="text-xs font-medium">Receipts</p>
            </div>
            <div className="text-center">
              <p className="text-[10px] text-muted-foreground">Reminders</p>
              <p className="text-xs font-medium">4-step</p>
            </div>
            <div className="text-center">
              <p className="text-[10px] text-muted-foreground">Chatbot</p>
              <p className="text-xs font-medium">PAID / HELP</p>
            </div>
          </div>
        </CardContent>
      </Card>
    )
  }

  if (status === "SCAN_QR_CODE" && showQr) {
    return (
      <Card className="border-warm-amber/30">
        <CardHeader className="pb-3">
          <CardTitle className="text-base flex items-center gap-2">
            <MessageCircle className="h-4 w-4 text-[#25D366]" /> WhatsApp
            <Badge variant="warning" className="gap-1 ml-1"><QrCode className="h-2.5 w-2.5" /> Scan QR</Badge>
          </CardTitle>
          <CardDescription className="text-xs">Open WhatsApp on your phone → Settings → Linked Devices → Link a Device</CardDescription>
        </CardHeader>
        <CardContent>
          <div className="flex flex-col items-center gap-4">
            {qrImage ? (
              <div className="relative">
                {/* Crop to QR area: the screenshot shows full WhatsApp web page. 
                    QR code is roughly in center. We use overflow hidden + object positioning. */}
                <div className="w-72 h-72 rounded-lg border-2 border-[#25D366]/20 overflow-hidden bg-white">
                  {/* eslint-disable-next-line @next/next/no-img-element */}
                  <img
                    src={qrImage}
                    alt="WhatsApp QR Code"
                    className="w-[200%] h-auto max-w-none"
                    style={{ marginLeft: "-30%", marginTop: "-35%" }}
                  />
                </div>
                <div className="absolute -bottom-2 -right-2 w-8 h-8 rounded-full bg-[#25D366] flex items-center justify-center shadow-lg">
                  <MessageCircle className="h-4 w-4 text-white" />
                </div>
              </div>
            ) : (
              <div className="w-72 h-72 rounded-lg border-2 border-dashed border-muted flex items-center justify-center">
                <Loader2 className="h-8 w-8 text-muted-foreground animate-spin" />
              </div>
            )}
            <div className="text-center space-y-1">
              <p className="text-sm font-medium">Scan with WhatsApp</p>
              <p className="text-xs text-muted-foreground">Open WhatsApp → Settings → Linked Devices → Link a Device</p>
              <p className="text-xs text-muted-foreground">Auto-refreshes every 5 seconds</p>
            </div>
            <Button variant="outline" size="sm" onClick={checkStatus} className="gap-1.5">
              <RefreshCw className="h-3 w-3" /> Refresh
            </Button>
          </div>
        </CardContent>
      </Card>
    )
  }

  // NO_SESSION or STARTING or ERROR
  return (
    <Card>
      <CardHeader className="pb-3">
        <CardTitle className="text-base flex items-center gap-2">
          <MessageCircle className="h-4 w-4 text-muted-foreground" /> WhatsApp
          <Badge variant="secondary" className="gap-1 ml-1"><WifiOff className="h-2.5 w-2.5" /> Offline</Badge>
        </CardTitle>
        <CardDescription className="text-xs">
          Connect WhatsApp to auto-send pledge receipts, payment reminders, and enable a chatbot for donors.
        </CardDescription>
      </CardHeader>
      <CardContent>
        <div className="rounded-lg bg-muted/50 p-4 space-y-3">
          <div className="flex items-start gap-3">
            <div className="w-10 h-10 rounded-lg bg-[#25D366]/10 flex items-center justify-center flex-shrink-0">
              <Smartphone className="h-5 w-5 text-[#25D366]" />
            </div>
            <div>
              <p className="text-sm font-medium">Connect your WhatsApp number</p>
              <ul className="text-xs text-muted-foreground mt-1 space-y-0.5">
                <li>📨 Pledge receipts with bank transfer details</li>
                <li>⏰ Automatic reminders (2d before → due day → 3d after → 10d final)</li>
                <li>🤖 Donor chatbot: reply PAID, HELP, CANCEL, STATUS</li>
                <li>📊 Volunteer notifications when someone pledges at their table</li>
              </ul>
            </div>
          </div>
          <Button onClick={startSession} disabled={starting} className="w-full bg-[#25D366] hover:bg-[#25D366]/90 text-white">
            {starting ? <><Loader2 className="h-4 w-4 mr-2 animate-spin" /> Starting session...</> : <><MessageCircle className="h-4 w-4 mr-2" /> Connect WhatsApp</>}
          </Button>
          <p className="text-[10px] text-muted-foreground text-center">
            Uses WAHA (WhatsApp HTTP API) · No WhatsApp Business API required · Free tier
          </p>
        </div>
      </CardContent>
    </Card>
  )
}