import type {Database} from "sqlite3";

import log from "../../log";
import path from "path";
import fs from "fs/promises";
import Config from "../../config";
import Msg, {Message} from "../../models/msg";
import Chan, {Channel} from "../../models/chan";
import Helper from "../../helper";
import type {SearchResponse, SearchQuery, SearchableMessageStorage} from "./types";
import Network from "../../models/network";

// TODO; type
let sqlite3: any;

try {
	sqlite3 = require("sqlite3");
} catch (e: any) {
	Config.values.messageStorage = Config.values.messageStorage.filter((item) => item !== "sqlite");

	log.error(
		"Unable to load sqlite3 module. See https://github.com/mapbox/node-sqlite3/wiki/Binaries"
	);
}

type Migration = {version: number; stmts: string[]};
type Rollback = {version: number; rollback_forbidden?: boolean; stmts: string[]};

export const currentSchemaVersion = 1679743888000; // use `new Date().getTime()`

// Desired schema, adapt to the newest version and add migrations to the array below
const schema = [
	"CREATE TABLE options (name TEXT, value TEXT, CONSTRAINT name_unique UNIQUE (name))",
	"CREATE TABLE messages (id INTEGER PRIMARY KEY AUTOINCREMENT, network TEXT, channel TEXT, time INTEGER, type TEXT, msg TEXT)",
	`CREATE TABLE migrations (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		version INTEGER NOT NULL UNIQUE,
		rollback_forbidden INTEGER DEFAULT 0 NOT NULL
	)`,
	`CREATE TABLE rollback_steps (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		migration_id INTEGER NOT NULL REFERENCES migrations ON DELETE CASCADE,
		step INTEGER NOT NULL,
		statement TEXT NOT NULL
	)`,
	"CREATE INDEX network_channel ON messages (network, channel)",
	"CREATE INDEX time ON messages (time)",
];

// the migrations will be executed in an exclusive transaction as a whole
// add new migrations to the end, with the version being the new 'currentSchemaVersion'
// write a corresponding down migration into rollbacks
export const migrations: Migration[] = [
	{
		version: 1672236339873,
		stmts: [
			"CREATE TABLE messages_new (id INTEGER PRIMARY KEY AUTOINCREMENT, network TEXT, channel TEXT, time INTEGER, type TEXT, msg TEXT)",
			"INSERT INTO messages_new(network, channel, time, type, msg) select network, channel, time, type, msg from messages order by time asc",
			"DROP TABLE messages",
			"ALTER TABLE messages_new RENAME TO messages",
			"CREATE INDEX network_channel ON messages (network, channel)",
			"CREATE INDEX time ON messages (time)",
		],
	},
	{
		version: 1679743888000,
		stmts: [
			`CREATE TABLE IF NOT EXISTS migrations (
				id INTEGER PRIMARY KEY AUTOINCREMENT,
				version INTEGER NOT NULL UNIQUE,
				rollback_forbidden INTEGER DEFAULT 0 NOT NULL
			)`,
			`CREATE TABLE IF NOT EXISTS rollback_steps (
				id INTEGER PRIMARY KEY AUTOINCREMENT,
				migration_id INTEGER NOT NULL REFERENCES migrations ON DELETE CASCADE,
				step INTEGER NOT NULL,
				statement TEXT NOT NULL
			)`,
		],
	},
];

// down migrations need to restore the state of the prior version.
// rollback can be disallowed by adding rollback_forbidden: true to it
export const rollbacks: Rollback[] = [
	{
		version: 1672236339873,
		stmts: [], // changes aren't visible, left empty on purpose
	},
	{
		version: 1679743888000,
		stmts: [], // here we can't drop the tables, as we use them in the code, so just leave those in
	},
];

class Deferred {
	resolve!: () => void;
	promise: Promise<void>;

	constructor() {
		this.promise = new Promise((resolve) => {
			this.resolve = resolve;
		});
	}
}

class SqliteMessageStorage implements SearchableMessageStorage {
	isEnabled: boolean;
	database!: Database;
	initDone: Deferred;
	userName: string;

	constructor(userName: string) {
		this.userName = userName;
		this.isEnabled = false;
		this.initDone = new Deferred();
	}

	async _enable() {
		const logsPath = Config.getUserLogsPath();
		const sqlitePath = path.join(logsPath, `${this.userName}.sqlite3`);

		try {
			await fs.mkdir(logsPath, {recursive: true});
		} catch (e) {
			throw Helper.catch_to_error("Unable to create logs directory", e);
		}

		this.isEnabled = true;

		this.database = new sqlite3.Database(sqlitePath);

		try {
			await this.run_pragmas(); // must be done outside of a transaction
			await this.run_migrations();
		} catch (e) {
			this.isEnabled = false;
			throw Helper.catch_to_error("Migration failed", e);
		}
	}

	async enable() {
		try {
			await this._enable();
		} finally {
			this.initDone.resolve(); // unblock the instance methods
		}
	}

	async setup_new_db() {
		for (const stmt of schema) {
			await this.serialize_run(stmt, []);
		}

		await this.serialize_run("INSERT INTO options (name, value) VALUES ('schema_version', ?)", [
			currentSchemaVersion.toString(),
		]);
	}

	async current_version(): Promise<number> {
		const have_options = await this.serialize_get(
			"select 1 from sqlite_master where type = 'table' and name = 'options'"
		);

		if (!have_options) {
			return 0;
		}

		const version = await this.serialize_get(
			"SELECT value FROM options WHERE name = 'schema_version'"
		);

		if (version === undefined) {
			// technically shouldn't happen, means something created a schema but didn't populate it
			// we'll try our best to recover
			return 0;
		}

		const storedSchemaVersion = parseInt(version.value, 10);
		return storedSchemaVersion;
	}

	async update_version_in_db() {
		return this.serialize_run("UPDATE options SET value = ? WHERE name = 'schema_version'", [
			currentSchemaVersion.toString(),
		]);
	}

	async _run_migrations(dbVersion: number) {
		log.info(
			`sqlite messages schema version is out of date (${dbVersion} < ${currentSchemaVersion}). Running migrations.`
		);

		const to_execute = necessaryMigrations(dbVersion);

		for (const stmt of to_execute.map((m) => m.stmts).flat()) {
			await this.serialize_run(stmt, []);
		}

		await this.update_version_in_db();
	}

	async run_pragmas() {
		await this.serialize_run("PRAGMA foreign_keys = ON;", []);
	}

	async run_migrations() {
		const version = await this.current_version();

		if (version > currentSchemaVersion) {
			throw `sqlite messages schema version is higher than expected (${version} > ${currentSchemaVersion}). Is The Lounge out of date?`;
		} else if (version === currentSchemaVersion) {
			return; // nothing to do
		}

		await this.serialize_run("BEGIN EXCLUSIVE TRANSACTION", []);

		try {
			if (version === 0) {
				await this.setup_new_db();
			} else {
				await this._run_migrations(version);
			}

			await this.insert_rollback_since(version);
		} catch (err) {
			await this.serialize_run("ROLLBACK", []);
			throw err;
		}

		await this.serialize_run("COMMIT", []);
		await this.serialize_run("VACUUM", []);
	}

	async close() {
		if (!this.isEnabled) {
			return;
		}

		this.isEnabled = false;

		return new Promise<void>((resolve, reject) => {
			this.database.close((err) => {
				if (err) {
					reject(`Failed to close sqlite database: ${err.message}`);
					return;
				}

				resolve();
			});
		});
	}

	async fetch_rollbacks(since_version: number) {
		const res = await this.serialize_fetchall(
			`select version, rollback_forbidden, statement
			from rollback_steps
			join migrations on migrations.id=rollback_steps.migration_id
			where version > ?
			order by version desc, step asc`,
			since_version
		);
		const result: Rollback[] = [];

		// convert to Rollback[]
		// requires ordering in the sql statement
		for (const raw of res) {
			const last = result.at(-1);

			if (!last || raw.version !== last.version) {
				result.push({
					version: raw.version,
					rollback_forbidden: Boolean(raw.rollback_forbidden),
					stmts: [raw.statement],
				});
			} else {
				last.stmts.push(raw.statment);
			}
		}

		return result;
	}

	async delete_migrations_older_than(version: number) {
		return this.serialize_run("delete from migrations where migrations.version > ?", [version]);
	}

	async _downgrade_to(version: number) {
		const _rollbacks = await this.fetch_rollbacks(version);

		if (_rollbacks.length === 0) {
			return version;
		}

		const forbidden = _rollbacks.find((item) => item.rollback_forbidden);

		if (forbidden) {
			throw Error(`can't downgrade past ${forbidden.version}`);
		}

		for (const rollback of _rollbacks) {
			for (const stmt of rollback.stmts) {
				await this.serialize_run(stmt, []);
			}
		}

		await this.delete_migrations_older_than(version);
		await this.update_version_in_db();

		return _rollbacks.at(-1)!.version; // assert valid due to length guard above
	}

	async downgrade_to(version: number) {
		if (version <= 0) {
			throw Error(`${version} is not a valid version to downgrade to`);
		}

		await this.serialize_run("BEGIN EXCLUSIVE TRANSACTION", []);

		let new_version: number;

		try {
			new_version = await this._downgrade_to(version);
		} catch (err) {
			await this.serialize_run("ROLLBACK", []);
			throw err;
		}

		await this.serialize_run("COMMIT", []);
		return new_version;
	}

	async downgrade() {
		const res = await this.downgrade_to(currentSchemaVersion);
		return res;
	}

	async insert_rollback_since(version: number) {
		const missing = newRollbacks(version);

		for (const rollback of missing) {
			const migration = await this.serialize_get(
				`insert into migrations
				(version, rollback_forbidden)
				values (?, ?)
				returning id`,
				rollback.version,
				rollback.rollback_forbidden || 0
			);

			for (const stmt of rollback.stmts) {
				let step = 0;
				await this.serialize_run(
					`insert into rollback_steps
					(migration_id, step, statement)
					values (?, ?, ?)`,
					[migration.id, step, stmt]
				);
				step++;
			}
		}
	}

	async index(network: Network, channel: Chan, msg: Msg) {
		await this.initDone.promise;

		if (!this.isEnabled) {
			return;
		}

		const clonedMsg = Object.keys(msg).reduce((newMsg, prop) => {
			// id is regenerated when messages are retrieved
			// previews are not stored because storage is cleared on lounge restart
			// type and time are stored in a separate column
			if (prop !== "id" && prop !== "previews" && prop !== "type" && prop !== "time") {
				newMsg[prop] = msg[prop];
			}

			return newMsg;
		}, {});

		await this.serialize_run(
			"INSERT INTO messages(network, channel, time, type, msg) VALUES(?, ?, ?, ?, ?)",
			[
				network.uuid,
				channel.name.toLowerCase(),
				msg.time.getTime(),
				msg.type,
				JSON.stringify(clonedMsg),
			]
		);
	}

	async deleteChannel(network: Network, channel: Channel) {
		await this.initDone.promise;

		if (!this.isEnabled) {
			return;
		}

		await this.serialize_run("DELETE FROM messages WHERE network = ? AND channel = ?", [
			network.uuid,
			channel.name.toLowerCase(),
		]);
	}

	async getMessages(
		network: Network,
		channel: Channel,
		nextID: () => number
	): Promise<Message[]> {
		await this.initDone.promise;

		if (!this.isEnabled || Config.values.maxHistory === 0) {
			return [];
		}

		// If unlimited history is specified, load 100k messages
		const limit = Config.values.maxHistory < 0 ? 100000 : Config.values.maxHistory;

		const rows = await this.serialize_fetchall(
			"SELECT msg, type, time FROM messages WHERE network = ? AND channel = ? ORDER BY time DESC LIMIT ?",
			network.uuid,
			channel.name.toLowerCase(),
			limit
		);

		return rows.reverse().map((row: any): Message => {
			const msg = JSON.parse(row.msg);
			msg.time = row.time;
			msg.type = row.type;

			const newMsg = new Msg(msg);
			newMsg.id = nextID();

			return newMsg;
		});
	}

	async search(query: SearchQuery): Promise<SearchResponse> {
		await this.initDone.promise;

		if (!this.isEnabled) {
			// this should never be hit as messageProvider is checked in client.search()
			throw new Error(
				"search called but sqlite provider not enabled. This is a programming error"
			);
		}

		// Using the '@' character to escape '%' and '_' in patterns.
		const escapedSearchTerm = query.searchTerm.replace(/([%_@])/g, "@$1");

		let select =
			'SELECT msg, type, time, network, channel FROM messages WHERE type = "message" AND json_extract(msg, "$.text") LIKE ? ESCAPE \'@\'';
		const params: any[] = [`%${escapedSearchTerm}%`];

		if (query.networkUuid) {
			select += " AND network = ? ";
			params.push(query.networkUuid);
		}

		if (query.channelName) {
			select += " AND channel = ? ";
			params.push(query.channelName.toLowerCase());
		}

		const maxResults = 100;

		select += " ORDER BY time DESC LIMIT ? OFFSET ? ";
		params.push(maxResults);
		params.push(query.offset);

		const rows = await this.serialize_fetchall(select, ...params);
		return {
			...query,
			results: parseSearchRowsToMessages(query.offset, rows).reverse(),
		};
	}

	canProvideMessages() {
		return this.isEnabled;
	}

	private serialize_run(stmt: string, params: any[]): Promise<void> {
		return new Promise((resolve, reject) => {
			this.database.serialize(() => {
				this.database.run(stmt, params, (err) => {
					if (err) {
						reject(err);
						return;
					}

					resolve();
				});
			});
		});
	}

	private serialize_fetchall(stmt: string, ...params: any[]): Promise<any[]> {
		return new Promise((resolve, reject) => {
			this.database.serialize(() => {
				this.database.all(stmt, params, (err, rows) => {
					if (err) {
						reject(err);
						return;
					}

					resolve(rows);
				});
			});
		});
	}

	private serialize_get(stmt: string, ...params: any[]): Promise<any> {
		return new Promise((resolve, reject) => {
			this.database.serialize(() => {
				this.database.get(stmt, params, (err, row) => {
					if (err) {
						reject(err);
						return;
					}

					resolve(row);
				});
			});
		});
	}
}

// TODO: type any
function parseSearchRowsToMessages(id: number, rows: any[]) {
	const messages: Msg[] = [];

	for (const row of rows) {
		const msg = JSON.parse(row.msg);
		msg.time = row.time;
		msg.type = row.type;
		msg.networkUuid = row.network;
		msg.channelName = row.channel;
		msg.id = id;
		messages.push(new Msg(msg));
		id += 1;
	}

	return messages;
}

export function necessaryMigrations(since: number): Migration[] {
	return migrations.filter((m) => m.version > since);
}

export function newRollbacks(since: number): Rollback[] {
	return rollbacks.filter((r) => r.version > since);
}

export default SqliteMessageStorage;