import { useCallback, useState } from "react";
import type { Coverage, FormState, Medication, RefillEntry } from "../types";
import { getMedTotal } from "../types";

export interface UseRefillReturn {
	// Refill state
	showRefillModal: boolean;
	setShowRefillModal: React.Dispatch<React.SetStateAction<boolean>>;
	refillPacks: number;
	setRefillPacks: React.Dispatch<React.SetStateAction<number>>;
	refillLoose: number;
	setRefillLoose: React.Dispatch<React.SetStateAction<number>>;
	refillSaving: boolean;
	refillHistory: RefillEntry[];
	refillHistoryExpanded: boolean;
	setRefillHistoryExpanded: React.Dispatch<React.SetStateAction<boolean>>;

	// Edit stock (correction) state
	showEditStockModal: boolean;
	setShowEditStockModal: React.Dispatch<React.SetStateAction<boolean>>;
	editStockFullBlisters: number;
	setEditStockFullBlisters: React.Dispatch<React.SetStateAction<number>>;
	editStockPartialBlisterPills: number;
	setEditStockPartialBlisterPills: React.Dispatch<React.SetStateAction<number>>;
	editStockSaving: boolean;

	// Actions
	loadRefillHistory: (medId: number) => Promise<void>;
	submitRefill: (
		medId: number,
		editingId: number | null,
		setForm: React.Dispatch<React.SetStateAction<FormState>>,
		loadMeds: () => void
	) => Promise<void>;
	submitStockCorrection: (medId: number, selectedMed: Medication, loadMeds: () => void) => Promise<void>;
	openRefillModal: () => void;
	closeRefillModal: () => void;
	openEditStockModal: (selectedMed: Medication, coverage: { all: Coverage[] }) => void;
	closeEditStockModal: () => void;
}

export function useRefill(): UseRefillReturn {
	// Refill state
	const [showRefillModal, setShowRefillModal] = useState(false);
	const [refillPacks, setRefillPacks] = useState(1);
	const [refillLoose, setRefillLoose] = useState(0);
	const [refillSaving, setRefillSaving] = useState(false);
	const [refillHistory, setRefillHistory] = useState<RefillEntry[]>([]);
	const [refillHistoryExpanded, setRefillHistoryExpanded] = useState(false);

	// Edit stock (correction) state
	const [showEditStockModal, setShowEditStockModal] = useState(false);
	const [editStockFullBlisters, setEditStockFullBlisters] = useState(0);
	const [editStockPartialBlisterPills, setEditStockPartialBlisterPills] = useState(0);
	const [editStockSaving, setEditStockSaving] = useState(false);

	// Load refill history for a medication
	const loadRefillHistory = useCallback(async (medId: number) => {
		try {
			const res = await fetch(`/api/medications/${medId}/refills`, { credentials: "include" });
			if (res.ok) {
				const data = await res.json();
				setRefillHistory(Array.isArray(data) ? data : data.refills || []);
			} else {
				setRefillHistory([]);
			}
		} catch {
			setRefillHistory([]);
		}
	}, []);

	// Submit a refill
	const submitRefill = useCallback(
		async (
			medId: number,
			editingId: number | null,
			setForm: React.Dispatch<React.SetStateAction<FormState>>,
			loadMeds: () => void
		) => {
			if (refillPacks < 1 && refillLoose < 1) return;
			setRefillSaving(true);
			try {
				const res = await fetch(`/api/medications/${medId}/refill`, {
					method: "POST",
					headers: { "Content-Type": "application/json" },
					credentials: "include",
					body: JSON.stringify({ packsAdded: refillPacks, loosePillsAdded: refillLoose }),
				});
				if (res.ok) {
					const data = await res.json();
					// Update form values if we're in edit mode
					if (editingId === medId && data.newStock) {
						setForm((f) => ({
							...f,
							packCount: String(data.newStock.packCount),
							looseTablets: String(data.newStock.looseTablets),
						}));
					}
					// Reset refill form
					setRefillPacks(1);
					setRefillLoose(0);
					// Close refill modal via history back for proper back-button support
					if (showRefillModal) {
						window.history.back();
					}
					// Reload medications to get updated stock
					loadMeds();
					// Reload refill history
					await loadRefillHistory(medId);
				}
			} catch {
				// ignore
			}
			setRefillSaving(false);
		},
		[refillPacks, refillLoose, showRefillModal, loadRefillHistory]
	);

	// Submit a stock correction - user says how many pills they have RIGHT NOW
	const submitStockCorrection = useCallback(
		async (medId: number, selectedMed: Medication, loadMeds: () => void) => {
			if (!selectedMed) return;
			setEditStockSaving(true);
			try {
				// Auto-convert: handle full blister and negative partial blister
				let finalFullBlisters = editStockFullBlisters;
				let finalPartialPills = editStockPartialBlisterPills;

				// Handle full blister: e.g. 9 pills in a 9-pill blister = +1 full blister, 0 partial
				if (finalPartialPills >= selectedMed.pillsPerBlister) {
					finalFullBlisters += 1;
					finalPartialPills = 0;
				}

				// Handle negative partial: e.g. -3 with 136 full = 135 full, 6 partial (for 9-pill blister)
				if (finalPartialPills < 0 && finalFullBlisters > 0) {
					finalFullBlisters -= 1;
					finalPartialPills = selectedMed.pillsPerBlister + finalPartialPills;
				}

				// Ensure we don't go negative
				if (finalPartialPills < 0) finalPartialPills = 0;
				if (finalFullBlisters < 0) finalFullBlisters = 0;

				// What the user says they have RIGHT NOW = the new DB total
				const desiredTotal = finalFullBlisters * selectedMed.pillsPerBlister + finalPartialPills;

				// The "base" from DB structure (without any stockAdjustment)
				const baseTotal =
					selectedMed.packCount * selectedMed.blistersPerPack * selectedMed.pillsPerBlister + selectedMed.looseTablets;

				// stockAdjustment = what we need to make getMedTotal() return desiredTotal
				const newStockAdjustment = desiredTotal - baseTotal;

				// Use the PATCH endpoint - it sets stockAdjustment AND lastStockCorrectionAt
				const res = await fetch(`/api/medications/${medId}/stock-adjustment`, {
					method: "PATCH",
					headers: { "Content-Type": "application/json" },
					credentials: "include",
					body: JSON.stringify({ stockAdjustment: newStockAdjustment }),
				});
				if (res.ok) {
					// Close edit stock modal via history back
					if (showEditStockModal) {
						window.history.back();
					}
					// Reload medications to get updated stock
					loadMeds();
				}
			} catch {
				// ignore
			}
			setEditStockSaving(false);
		},
		[editStockFullBlisters, editStockPartialBlisterPills, showEditStockModal]
	);

	const openRefillModal = useCallback(() => {
		setShowRefillModal(true);
		window.history.pushState({ modal: "refill" }, "");
	}, []);

	const closeRefillModal = useCallback(() => {
		if (showRefillModal) {
			window.history.back();
		}
	}, [showRefillModal]);

	const openEditStockModal = useCallback((selectedMed: Medication, coverage: { all: Coverage[] }) => {
		if (!selectedMed) return;
		// Get current stock from coverage (after consumption)
		const medCoverage = coverage.all.find((c) => c.name === selectedMed.name);
		const dbTotal = getMedTotal(selectedMed);
		const currentStock = medCoverage ? Math.round(medCoverage.medsLeft) : dbTotal;

		// Simply divide into full blisters and partial
		const fullBlisters = Math.floor(currentStock / selectedMed.pillsPerBlister);
		const partialPills = currentStock % selectedMed.pillsPerBlister;

		// Pre-fill with current values
		setEditStockFullBlisters(fullBlisters);
		setEditStockPartialBlisterPills(partialPills);
		setShowEditStockModal(true);
		window.history.pushState({ modal: "editStock" }, "");
	}, []);

	const closeEditStockModal = useCallback(() => {
		if (showEditStockModal) {
			window.history.back();
		}
	}, [showEditStockModal]);

	return {
		showRefillModal,
		setShowRefillModal,
		refillPacks,
		setRefillPacks,
		refillLoose,
		setRefillLoose,
		refillSaving,
		refillHistory,
		refillHistoryExpanded,
		setRefillHistoryExpanded,
		showEditStockModal,
		setShowEditStockModal,
		editStockFullBlisters,
		setEditStockFullBlisters,
		editStockPartialBlisterPills,
		setEditStockPartialBlisterPills,
		editStockSaving,
		loadRefillHistory,
		submitRefill,
		submitStockCorrection,
		openRefillModal,
		closeRefillModal,
		openEditStockModal,
		closeEditStockModal,
	};
}