/**
 * 採購單表單管理 Hook
 */

import { useState, useEffect } from "react";
import type { PurchaseOrder, PurchaseOrderItem, Supplier, PurchaseOrderStatus } from "@/types/purchase-order";
import { calculateSubtotal } from "@/utils/purchase-order";

interface UsePurchaseOrderFormProps {
    order?: PurchaseOrder;
    suppliers: Supplier[];
}

export function usePurchaseOrderForm({ order, suppliers }: UsePurchaseOrderFormProps) {
    const [supplierId, setSupplierId] = useState("");
    const [expectedDate, setExpectedDate] = useState("");
    const [items, setItems] = useState<PurchaseOrderItem[]>([]);
    const [notes, setNotes] = useState("");
    const [status, setStatus] = useState<PurchaseOrderStatus>("draft");
    const [warehouseId, setWarehouseId] = useState<string | number>("");
    const [invoiceNumber, setInvoiceNumber] = useState("");
    const [invoiceDate, setInvoiceDate] = useState("");
    const [invoiceAmount, setInvoiceAmount] = useState("");

    // 載入編輯訂單資料
    useEffect(() => {
        if (order) {
            setSupplierId(order.supplierId);
            setExpectedDate(order.expectedDate);
            setItems(order.items);
            setNotes(order.remark || "");
            setStatus(order.status);
            setWarehouseId(order.warehouse_id || "");
            setInvoiceNumber(order.invoiceNumber || "");
            setInvoiceDate(order.invoiceDate || "");
            setInvoiceAmount(order.invoiceAmount ? String(order.invoiceAmount) : "");
        }
    }, [order]);

    const resetForm = () => {
        setSupplierId("");
        setExpectedDate("");
        setItems([]);
        setNotes("");
        setStatus("draft");
        setWarehouseId("");
        setInvoiceNumber("");
        setInvoiceDate("");
        setInvoiceAmount("");
    };

    const selectedSupplier = suppliers.find((s) => String(s.id) === String(supplierId));
    const isOrderSent = order && order.status !== "draft";

    // 新增商品項目
    const addItem = () => {
        if (!selectedSupplier) return;

        setItems([
            ...items,
            {
                productId: "",
                productName: "",
                quantity: 1,
                unitPrice: 0,
                subtotal: 0,
                selectedUnit: "base",
            },
        ]);
    };

    // 移除商品項目
    const removeItem = (index: number) => {
        setItems(items.filter((_, i) => i !== index));
    };

    // 更新商品項目
    const updateItem = (index: number, field: keyof PurchaseOrderItem, value: any) => {
        const newItems = [...items];
        const item = { ...newItems[index] };

        if (field === "productId" && selectedSupplier) {
            // value is productId string
            const product = selectedSupplier.commonProducts.find((p) => p.productId === value);
            if (product) {
                // @ts-ignore
                item.productId = value;
                item.productName = product.productName;
                item.base_unit_id = product.base_unit_id;
                item.base_unit_name = product.base_unit_name;
                item.large_unit_id = product.large_unit_id;
                item.large_unit_name = product.large_unit_name;
                item.purchase_unit_id = product.purchase_unit_id;
                item.conversion_rate = product.conversion_rate;
                item.unitPrice = product.lastPrice;
                item.previousPrice = product.lastPrice;

                // 決定預設單位
                const isPurchaseUnitLarge = product.purchase_unit_id && product.large_unit_id && product.purchase_unit_id === product.large_unit_id;

                if (isPurchaseUnitLarge) {
                    item.selectedUnit = 'large';
                    item.unitId = product.large_unit_id;
                } else {
                    item.selectedUnit = 'base';
                    item.unitId = product.base_unit_id;
                }

                // 初始小計 = 數量 * 單價
                item.subtotal = calculateSubtotal(Number(item.quantity), Number(item.unitPrice));
            }
        } else if (field === "selectedUnit") {
            // @ts-ignore
            item.selectedUnit = value;
            if (value === 'large') {
                item.unitId = item.large_unit_id;
            } else {
                item.unitId = item.base_unit_id;
            }
            // Switch unit doesn't change Total Amount (Subtotal), but implies Unit Price changes?
            // Actually if I switch unit, the Quantity is usually for that unit.
            // If I have 1 Box ($100), and switch to Pc. Quantity is still 1. 
            // Total is $100. So Unit Price (per Pc) becomes $100.
            // This seems safely consistent with "Total Amount" anchor.
        } else {
            // @ts-ignore
            item[field] = value;
        }

        // 重新計算 (Always derive UnitPrice from Subtotal and Quantity)
        // 除了剛剛已經算過 subtotal 的 productId case
        if (field !== "productId") {
            if (item.quantity > 0) {
                item.unitPrice = Number(item.subtotal) / Number(item.quantity);
            } else {
                item.unitPrice = 0;
            }
        }

        newItems[index] = item;
        setItems(newItems);
    };

    return {
        // State
        supplierId,
        expectedDate,
        items,
        notes,
        status,
        selectedSupplier,
        isOrderSent,
        warehouseId,
        invoiceNumber,
        invoiceDate,
        invoiceAmount,

        // Setters
        setSupplierId,
        setExpectedDate,
        setNotes,
        setStatus,
        setWarehouseId,
        setInvoiceNumber,
        setInvoiceDate,
        setInvoiceAmount,

        // Methods
        addItem,
        removeItem,
        updateItem,
        resetForm,
    };
}