import type { ReadingLog, ReadingLogEntry } from "@utils/ReadingLog";
import { getContext, setContext } from "svelte";
import { createDateFilter, type DateFilterStore } from "./date-filter.svelte";

export interface ReadingLogStore extends DateFilterStore {
	get entries(): ReadingLogEntry[];

	addEntry(entry: ReadingLogEntry): Promise<void>;
	updateEntry(entry: ReadingLogEntry): Promise<void>;
	removeEntry(entry: ReadingLogEntry): Promise<void>;
	destroy(): void;
}

export function createReadingLog(readingLog: ReadingLog): ReadingLogStore {
	let entries: ReadingLogEntry[] = $state(readingLog.getEntries());

	const dateFilter = createDateFilter(
		() => entries,
		(entry) => entry.createdAt,
		true
	);

	async function addEntry(entry: ReadingLogEntry): Promise<void> {
		await readingLog.createEntry(
			entry.book,
			entry.pagesRead,
			entry.pagesReadTotal
		);
	}

	async function updateEntry(entry: ReadingLogEntry): Promise<void> {
		await readingLog.updateEntry(entry);
	}

	async function removeEntry(entry: ReadingLogEntry): Promise<void> {
		await readingLog.removeEntry(entry);
	}

	const loadHandler = readingLog.on("load", (payload) => {
		entries = payload.entries;
	});

	const createdHandler = readingLog.on("created", (payload) => {
		entries.push(payload.entry);
	});

	const updatedHandler = readingLog.on("updated", (payload) => {
		const index = entries.findIndex(
			(entry) => entry.id === payload.entry.id
		);
		if (index !== -1) {
			entries[index] = payload.entry;
		}
	});

	const removedHandler = readingLog.on("removed", (payload) => {
		const index = entries.findIndex(
			(entry) => entry.id === payload.entry.id
		);
		if (index !== -1) {
			entries.splice(index, 1);
		}
	});

	const sortedData = $derived(
		dateFilter.filteredData.sort((a, b) => a.createdAt.diff(b.createdAt))
	);

	return {
		get entries() {
			return sortedData;
		},
		get filterYear() {
			return dateFilter.filterYear;
		},
		set filterYear(value) {
			dateFilter.filterYear = value;
		},
		get filterMonth() {
			return dateFilter.filterMonth;
		},
		set filterMonth(value) {
			dateFilter.filterMonth = value;
		},
		get filterYears() {
			return dateFilter.filterYears;
		},
		get filterMonths() {
			return dateFilter.filterMonths;
		},
		addEntry,
		updateEntry,
		removeEntry,
		destroy() {
			loadHandler.off();
			createdHandler.off();
			updatedHandler.off();
			removedHandler.off();
		},
	};
}

const READING_LOG_KEY = Symbol("readingLog");

export function setReadingLogContext(state: ReadingLogStore) {
	setContext(READING_LOG_KEY, state);
}

export function getReadingLogContext(): ReadingLogStore {
	return getContext(READING_LOG_KEY);
}