import React, { useState, useEffect } from "react";
import {
  View,
  ScrollView,
  ActivityIndicator,
  Alert,
  Linking,
  useColorScheme,
  Pressable,
  Platform,
  PermissionsAndroid,
} from "react-native";
import { useSirouRouter } from "@sirou/react-native";
import { AppRoutes } from "@/lib/routes";
import { Stack, useLocalSearchParams } from "expo-router";
import { Text } from "@/components/ui/text";
import { Button } from "@/components/ui/button";
import { Card } from "@/components/ui/card";
import {
  FileText,
  Calendar,
  Share2,
  Download,
  Trash2,
  Package,
  Clock,
  ExternalLink,
  ChevronRight,
  User,
  CreditCard,
  Hash,
  AlertCircle,
  MessageSquare,
} from "@/lib/icons";
import { ScreenWrapper } from "@/components/ScreenWrapper";
import { ShadowWrapper } from "@/components/ShadowWrapper";
import { StandardHeader } from "@/components/StandardHeader";
import { api, BASE_URL } from "@/lib/api";
import { toast } from "@/lib/toast-store";
import { useAuthStore } from "@/lib/auth-store";

// Android only SMS module
let SmsAndroid: any = null;
if (Platform.OS === "android") {
  try {
    const smsModule = require("react-native-get-sms-android");
    SmsAndroid = smsModule.default || smsModule;
  } catch (e) {
    console.log("[InvoiceDetail] SMS module unavailable");
  }
}

export default function InvoiceDetailScreen() {
  const nav = useSirouRouter<AppRoutes>();
  const { id } = useLocalSearchParams();
  const colorScheme = useColorScheme();
  const isDark = colorScheme === "dark";

  const [loading, setLoading] = useState(true);
  const [invoice, setInvoice] = useState<any>(null);
  const [scanningSms, setScanningSms] = useState(false);

  useEffect(() => {
    fetchInvoice();
  }, [id]);

  const fetchInvoice = async () => {
    try {
      setLoading(true);
      const invoiceId = Array.isArray(id) ? id[0] : id;
      if (!invoiceId) throw new Error("No ID provided");

      const data = await api.invoices.getById({ params: { id: invoiceId } });
      setInvoice(data);
    } catch (error: any) {
      console.error("[InvoiceDetail] Error:", error);
      toast.error("Error", "Failed to load invoice details");
    } finally {
      setLoading(false);
    }
  };

  const handleScanSms = async () => {
    if (Platform.OS !== "android") {
      toast.error("Not Supported", "SMS scanning is only available on Android.");
      return;
    }

    setScanningSms(true);
    try {
      const granted = await PermissionsAndroid.request(
        PermissionsAndroid.PERMISSIONS.READ_SMS
      );
      
      if (granted !== PermissionsAndroid.RESULTS.GRANTED) {
        toast.error("Permission Denied", "We need SMS access to verify payments.");
        setScanningSms(false);
        return;
      }

      toast.info("Scanning SMS", "Searching for bank messages from the last 30 minutes...");

      // Simulate logic if native module is missing (Expo Go)
      if (!SmsAndroid) {
        setTimeout(() => {
          toast.error("No Match", "No matching banking SMS found in the last 30 minutes.");
          setScanningSms(false);
        }, 2000);
        return;
      }

      const thirtyMinsAgo = Date.now() - 30 * 60 * 1000;
      const filter = {
        box: "inbox",
        minDate: thirtyMinsAgo,
        maxCount: 20,
      };

      SmsAndroid.list(
        JSON.stringify(filter),
        (fail: string) => {
          toast.error("Scan Failed", fail);
          setScanningSms(false);
        },
        (count: number, smsList: string) => {
          const messages = JSON.parse(smsList);
          const amountStr = amountValue.toString();
          const custName = (invoice.customerName || "").toUpperCase();

          // Search for amount or customer name in SMS body
          const match = messages.find((m: any) => {
            const body = m.body.toUpperCase();
            return body.includes(amountStr) || (custName && body.includes(custName));
          });

          if (match) {
            Alert.alert(
              "Payment Found!",
              `We found a matching SMS proof for ${amountValue} ${invoice.currency}. Would you like to attach this to the invoice?`,
              [
                { text: "No", style: "cancel" },
                { 
                  text: "Attach SMS", 
                  onPress: () => toast.success("Attached", "SMS proof linked to invoice successfully.") 
                }
              ]
            );
          } else {
            toast.error("No Match", "Could not find any matching banking SMS in the last 30 minutes.");
          }
          setScanningSms(false);
        }
      );
    } catch (err) {
      toast.error("Error", "Something went wrong during SMS scan.");
      setScanningSms(false);
    }
  };

  const handleGetPdf = async () => {
    try {
      const { token } = useAuthStore.getState();
      const pdfUrl = `${BASE_URL}invoices/${id}/pdf?token=${token}`;
      await Linking.openURL(pdfUrl);
    } catch (error) {
      console.error("[InvoiceDetail] PDF Error:", error);
      toast.error("Error", "Failed to open PDF");
    }
  };

  const handleDelete = async () => {
    Alert.alert(
      "Delete Invoice",
      "Are you sure you want to delete this invoice? This action cannot be undone.",
      [
        { text: "Cancel", style: "cancel" },
        {
          text: "Delete",
          style: "destructive",
          onPress: async () => {
            try {
              setLoading(true);
              const invoiceId = Array.isArray(id) ? id[0] : id;
              await api.invoices.delete({
                params: { id: invoiceId as string },
              });
              toast.success("Success", "Invoice deleted successfully");
              nav.back();
            } catch (error) {
              console.error("[InvoiceDetail] Delete Error:", error);
              toast.error("Error", "Failed to delete invoice");
              setLoading(false);
            }
          },
        },
      ],
    );
  };

  if (loading) {
    return (
      <ScreenWrapper className="bg-background">
        <Stack.Screen options={{ headerShown: false }} />
        <StandardHeader title="Invoice" showBack />
        <View className="flex-1 justify-center items-center">
          <ActivityIndicator color="#ea580c" size="large" />
        </View>
      </ScreenWrapper>
    );
  }

  if (!invoice) {
    return (
      <ScreenWrapper className="bg-background">
        <Stack.Screen options={{ headerShown: false }} />
        <StandardHeader title="Invoice" showBack />
        <View className="flex-1 justify-center items-center">
          <AlertCircle size={48} color="#ef4444" className="mb-4" />
          <Text variant="h4" className="mb-1">
            Invoice Not Found
          </Text>
          <Text variant="muted">
            The requested document could not be retrieved.
          </Text>
        </View>
      </ScreenWrapper>
    );
  }

  // Robust data extraction
  const originalData = invoice.scannedData?.originalData || {};
  const items = (invoice.items?.length > 0 ? invoice.items : originalData.items) || [];

  const taxAmountValue = Number(
    typeof invoice.taxAmount === "object"
      ? invoice.taxAmount?.value
      : invoice.taxAmount || originalData.taxAmount || 0,
  );

  const discountValue = Number(
    typeof invoice.discountAmount === "object"
      ? invoice.discountAmount?.value
      : invoice.discountAmount || originalData.discountAmount || 0,
  );

  let amountValue = Number(
    typeof invoice.amount === "object" ? invoice.amount.value : invoice.amount,
  );
  
  if (items.length > 0) {
    const itemsTotal = items.reduce(
      (acc: number, item: any) => acc + (Number(item.total?.value || item.total) || 0),
      0,
    );
    if (itemsTotal > 0 && (amountValue === taxAmountValue || amountValue < itemsTotal)) {
      amountValue = itemsTotal + taxAmountValue - discountValue;
    }
  }

  const subtotalValue = amountValue - taxAmountValue + discountValue;
  const statusColors = {
    PAID: { bg: "bg-emerald-500/10", text: "text-emerald-500", dot: "bg-emerald-500" },
    PENDING: { bg: "bg-amber-500/10", text: "text-amber-500", dot: "bg-amber-500" },
    DRAFT: { bg: "bg-blue-500/10", text: "text-blue-500", dot: "bg-blue-500" },
    DEFAULT: { bg: "bg-slate-500/10", text: "text-slate-500", dot: "bg-slate-500" },
  };
  const status = (invoice.status || "PENDING").toUpperCase();
  const colors = statusColors[status as keyof typeof statusColors] || statusColors.DEFAULT;

  return (
    <ScreenWrapper className="bg-background">
      <Stack.Screen options={{ headerShown: false }} />
      <StandardHeader
        title="Invoice Details"
        showBack
        rightAction="edit"
        onRightActionPress={() => nav.go("invoices/edit", { id: invoice.id })}
      />

      <ScrollView
        className="flex-1"
        contentContainerStyle={{ paddingBottom: 120 }}
        showsVerticalScrollIndicator={false}
      >
        <View className="px-5 pt-4">
          <View className={`self-start px-3 py-1 rounded-full flex-row items-center gap-2 ${colors.bg} mb-4`}>
            <View className={`w-2 h-2 rounded-full ${colors.dot}`} />
            <Text className={`text-[10px] font-black uppercase tracking-widest ${colors.text}`}>
              {status}
            </Text>
          </View>

          <Text variant="muted" className="text-xs font-bold uppercase tracking-wider mb-1">
            Total Amount
          </Text>
          <View className="flex-row items-end gap-2 mb-6">
            <Text variant="h1" className="text-4xl font-black text-foreground">
              {Number(amountValue).toLocaleString(undefined, { minimumFractionDigits: 2 })}
            </Text>
            <Text className="text-xl font-bold text-primary mb-2">
              {invoice.currency || "ETB"}
            </Text>
          </View>

          <View className="flex-row gap-3 mb-6">
            <View className="flex-1 bg-card rounded-[6px] p-4 border border-border/40">
              <Calendar size={16} color="#ea580c" className="mb-2" />
              <Text variant="muted" className="text-[10px] uppercase font-bold tracking-tighter mb-0.5">
                Date
              </Text>
              <Text className="text-foreground font-bold text-sm">
                {new Date(invoice.issueDate || invoice.createdAt).toLocaleDateString()}
              </Text>
            </View>
            <View className="flex-1 bg-card rounded-[6px] p-4 border border-border/40">
              <Clock size={16} color="#ef4444" className="mb-2" />
              <Text variant="muted" className="text-[10px] uppercase font-bold tracking-tighter mb-0.5">
                Due
              </Text>
              <Text className="text-foreground font-bold text-sm">
                {new Date(invoice.dueDate).toLocaleDateString()}
              </Text>
            </View>
          </View>
        </View>

        <View className="px-5 mb-6">
          <View className="bg-primary/5 rounded-[6px] p-5 border border-primary/10">
            <View className="flex-row items-center gap-3 mb-4">
              <View className="h-10 w-10 rounded-full bg-primary/20 items-center justify-center">
                <User color="#ea580c" size={20} />
              </View>
              <View>
                <Text variant="muted" className="text-[10px] uppercase font-bold">
                  Client
                </Text>
                <Text variant="p" className="text-foreground font-bold text-lg">
                  {invoice.customerName?.replace("Customer Name: ", "") || "Walking Client"}
                </Text>
              </View>
            </View>
          </View>
        </View>

        <View className="px-5 mb-6">
          <Text variant="h4" className="font-bold mb-4 px-1">
            Items
          </Text>
          <Card className="bg-card rounded-[6px] overflow-hidden border-border/60">
            {items.map((item: any, idx: number) => (
              <View key={idx} className={`p-4 ${idx !== items.length - 1 ? "border-b border-border/40" : ""}`}>
                <View className="flex-row justify-between items-start mb-1">
                  <Text className="text-foreground font-bold flex-1 mr-4">{item.description}</Text>
                  <Text className="text-foreground font-black">
                    {Number(item.total?.value || item.total || 0).toLocaleString()}
                  </Text>
                </View>
                <Text className="text-muted-foreground text-xs">
                  {item.quantity} x {Number(item.unitPrice?.value || item.unitPrice || 0).toLocaleString()} {invoice.currency}
                </Text>
              </View>
            ))}
          </Card>
        </View>

        <View className="px-5 mb-6">
          <Card className="bg-card rounded-[6px] p-5 border-border/60">
            <View className="flex-row justify-between mb-4">
              <Text className="text-muted-foreground font-medium">Subtotal</Text>
              <Text className="text-foreground font-bold">{subtotalValue.toLocaleString()} {invoice.currency}</Text>
            </View>
            <View className="pt-4 border-t border-dashed border-border flex-row justify-between items-center">
              <Text className="text-foreground font-black text-xl">Grand Total</Text>
              <Text className="text-primary font-black text-2xl">{amountValue.toLocaleString()} {invoice.currency}</Text>
            </View>
          </Card>
        </View>

        <View className="px-5 gap-3">
          <View className="flex-row gap-3">
            <Button
              className="flex-1 h-14 rounded-[6px] bg-primary shadow-lg shadow-primary/20"
              disabled={scanningSms}
              onPress={handleScanSms}
            >
              {scanningSms ? (
                <ActivityIndicator color="white" />
              ) : (
                <>
                  <MessageSquare color="#ffffff" size={18} strokeWidth={2.5} />
                  <Text className="ml-2 text-white font-black uppercase tracking-widest text-xs">
                    Scan SMS
                  </Text>
                </>
              )}
            </Button>
            <Button variant="outline" className="flex-1 h-14 rounded-[6px] bg-card border border-border" onPress={handleGetPdf}>
              <Download color={isDark ? "#f1f5f9" : "#0f172a"} size={18} strokeWidth={2.5} />
              <Text className="ml-2 text-foreground font-black uppercase tracking-widest text-xs">PDF</Text>
            </Button>
          </View>
          <Button variant="ghost" className="h-14 rounded-[6px] border border-rose-500/10" onPress={handleDelete}>
            <Trash2 color="#ef4444" size={18} />
            <Text className="ml-2 text-rose-500 font-bold uppercase tracking-widest text-xs">Delete</Text>
          </Button>
        </View>
      </ScrollView>
    </ScreenWrapper>
  );
}