const crypto = require("crypto");
const { config } = require("../config");
const {
	DATASETS,
	normalizeDatasetList,
	normalizeLanguageList,
} = require("../datasets");
const { connectToMongo } = require("../db/client");
const { ensureIndexes } = require("../db/indexes");
const { fetchQuestlogDetail, fetchQuestlogPage } = require("./questlogClient");

const importStatus = {
	running: false,
	startedAt: null,
	finishedAt: null,
	error: null,
	current: null,
	totals: {},
};

const ITEM_DETAIL_CONCURRENCY = 6;

function stableJsonHash(value) {
	return crypto.createHash("sha1").update(JSON.stringify(value)).digest("hex");
}

function extractSourceId(record) {
	return String(
		record?.compoundId ||
			record?.id ||
			record?._id ||
			record?.slug ||
			record?.name ||
			record?.title ||
			stableJsonHash(record),
	);
}

function extractName(record) {
	const value =
		record?.name ||
		record?.title ||
		record?.displayName ||
		record?.id ||
		record?.compoundId ||
		"";
	return String(value).replace(/\s+/g, " ").trim();
}

function buildStoredDocument(dataset, language, record) {
	const sourceId = extractSourceId(record);
	const name = extractName(record);
	const rawText = JSON.stringify(record);

	return {
		dataset: dataset.key,
		language,
		source: "questlog.gg",
		sourceMethod: dataset.method,
		sourceId,
		name,
		searchText: `${name} ${rawText}`,
		raw: record,
		importedAt: new Date(),
	};
}

async function upsertRecords(db, dataset, language, records) {
	if (records.length === 0) {
		return { matched: 0, modified: 0, upserted: 0 };
	}

	const collection = db.collection(dataset.collection);
	const operations = records.map((record) => {
		const document = buildStoredDocument(dataset, language, record);
		return {
			updateOne: {
				filter: { language, sourceId: document.sourceId },
				update: { $set: document },
				upsert: true,
			},
		};
	});

	const result = await collection.bulkWrite(operations, { ordered: false });
	return {
		matched: result.matchedCount || 0,
		modified: result.modifiedCount || 0,
		upserted: result.upsertedCount || 0,
	};
}

async function mapWithConcurrency(values, limit, iteratee) {
	const results = new Array(values.length);
	let nextIndex = 0;

	async function worker() {
		while (nextIndex < values.length) {
			const currentIndex = nextIndex;
			nextIndex += 1;
			results[currentIndex] = await iteratee(
				values[currentIndex],
				currentIndex,
			);
		}
	}

	const workerCount = Math.min(limit, values.length);
	await Promise.all(Array.from({ length: workerCount }, worker));
	return results;
}

function extractItemDetailId(record) {
	if (record?.id) {
		return String(record.id);
	}

	if (record?.compoundId) {
		return String(record.compoundId).replace(/^item-/, "");
	}

	return undefined;
}

async function fetchItemDetailRecords(records, language) {
	const detailDataset = DATASETS.items.detail;
	return mapWithConcurrency(
		records,
		ITEM_DETAIL_CONCURRENCY,
		async (record) => {
			const id = extractItemDetailId(record);
			if (!id) {
				throw new Error(
					`Could not determine Questlog item detail id for ${JSON.stringify(record)}`,
				);
			}

			return fetchQuestlogDetail(detailDataset.method, id, language);
		},
	);
}

async function importItemDetails(db, language, page, records) {
	const detailDataset = DATASETS.items.detail;
	importStatus.current = {
		dataset: detailDataset.key,
		language,
		page,
		records: records.length,
	};
	const details = await fetchItemDetailRecords(records, language);
	return upsertRecords(db, detailDataset, language, details);
}

function resetStatus() {
	importStatus.running = true;
	importStatus.startedAt = new Date().toISOString();
	importStatus.finishedAt = null;
	importStatus.error = null;
	importStatus.current = null;
	importStatus.totals = {};
}

function recordTotals(datasetKey, language, pageResult, recordsCount) {
	const key = `${datasetKey}:${language}`;
	const existing = importStatus.totals[key] || {
		pages: 0,
		records: 0,
		matched: 0,
		modified: 0,
		upserted: 0,
	};
	existing.pages += 1;
	existing.records += recordsCount;
	existing.matched += pageResult.matched;
	existing.modified += pageResult.modified;
	existing.upserted += pageResult.upserted;
	importStatus.totals[key] = existing;
}

async function importDatasetLanguage(db, dataset, language, maxPages) {
	let page = 1;

	while (true) {
		importStatus.current = { dataset: dataset.key, language, page };
		const payload = await fetchQuestlogPage(dataset, language, page);

		if (payload.records.length === 0) {
			break;
		}

		const pageResult = await upsertRecords(
			db,
			dataset,
			language,
			payload.records,
		);
		recordTotals(dataset.key, language, pageResult, payload.records.length);

		if (dataset.detail) {
			const detailResult = await importItemDetails(
				db,
				language,
				page,
				payload.records,
			);
			recordTotals(
				dataset.detail.key,
				language,
				detailResult,
				payload.records.length,
			);
		}

		const reachedKnownEnd = payload.pageCount && page >= payload.pageCount;
		const reachedConfiguredLimit = maxPages && page >= maxPages;
		if (reachedKnownEnd || reachedConfiguredLimit) {
			break;
		}

		page += 1;
	}
}

async function runImport(options = {}) {
	if (importStatus.running) {
		const error = new Error("An import is already running");
		error.status = 409;
		throw error;
	}

	const datasetKeys = normalizeDatasetList(options.datasets);
	const languages = normalizeLanguageList(options.languages);
	const maxPages = options.maxPages || config.importer.maxPages;

	resetStatus();

	try {
		const db = await connectToMongo();
		await ensureIndexes(db);

		for (const datasetKey of datasetKeys) {
			const dataset = DATASETS[datasetKey];
			for (const language of languages) {
				await importDatasetLanguage(db, dataset, language, maxPages);
			}
		}

		importStatus.finishedAt = new Date().toISOString();
		importStatus.running = false;
		importStatus.current = null;
		return getImportStatus();
	} catch (error) {
		importStatus.finishedAt = new Date().toISOString();
		importStatus.running = false;
		importStatus.error = error.message;
		throw error;
	}
}

function getImportStatus() {
	return {
		running: importStatus.running,
		startedAt: importStatus.startedAt,
		finishedAt: importStatus.finishedAt,
		error: importStatus.error,
		current: importStatus.current,
		totals: importStatus.totals,
	};
}

function startImport(options = {}) {
	const promise = runImport(options).catch(() => undefined);
	return promise;
}

module.exports = {
	getImportStatus,
	runImport,
	startImport,
};