import * as crypto from 'crypto';
import {NachklangAdminDB} from '../Admin.db.js';
import {AppPermission, isAppName, isAppPermission, ACCESS_ROLE} from '../admin.schema.js';

const db = NachklangAdminDB.db;

/**
 * Invitations are this API's only path to a new account (there is no public
 * sign-up). The raw token exists exactly twice: in the mail we send and in the
 * request body when it comes back. What we store is its SHA-256 hash, so a
 * database dump does not hand out account access - the same reasoning as the
 * calendar module's session key hashing, and the reason lookups go through
 * `findByToken` rather than any query on a plaintext column.
 */

export const INVITATION_TTL_DAYS = 7;

export interface OpenInvitation {
	id: number;
	email: string;
	name: string;
	permissions: AppPermission[];
	invitedBy: string | null;
	createdAt: Date;
	expiresAt: Date;
}

export interface AcceptableInvitation {
	id: number;
	email: string;
	name: string;
	permissions: AppPermission[];
}

const hashToken = (token: string): string => {
	return crypto.createHash('sha256').update(token).digest('hex');
};

const generateToken = (): string => {
	// 32 bytes, url-safe: it travels in a mail link's query string.
	return crypto.randomBytes(32).toString('base64url');
};

/**
 * Reads the stored permission list. Two shapes are accepted: the current
 * `[{app, role}]`, and a bare `['tickets', ...]` from before roles existed,
 * which means the same thing at the `access` role. Invitations live for seven
 * days, so a deploy that changes the shape has in-flight rows in the old one -
 * tolerating both is what stops those invitees from being stranded.
 *
 * mysql2 hands back a JSON column already parsed; a driver or column-type
 * change that turns it into a string must not break the read path either.
 */
const parsePermissions = (value: unknown): AppPermission[] => {
	const raw = typeof value === 'string' ? JSON.parse(value) : value;
	if (!Array.isArray(raw)) {
		return [];
	}

	return raw.flatMap((entry): AppPermission[] => {
		if (isAppName(entry)) {
			return [{app: entry, role: ACCESS_ROLE}];
		}
		return isAppPermission(entry) ? [{app: entry.app, role: entry.role}] : [];
	});
};

const expiryFromNow = (): Date => {
	return new Date(Date.now() + INVITATION_TTL_DAYS * 24 * 60 * 60 * 1000);
};

/**
 * Creates an invitation and returns the raw token for the mail. Any earlier
 * open invitation for the same address is revoked first: two valid links for
 * one mailbox is a needless second live credential, and "resend" would
 * otherwise quietly accumulate them.
 */
export const createInvitation = async (
	email: string,
	name: string,
	permissions: AppPermission[],
	invitedBy: string | null
): Promise<{id: number; token: string; expiresAt: Date}> => {
	const token = generateToken();
	const expiresAt = expiryFromNow();
	const valid = permissions.filter(isAppPermission);

	const id = await db.transaction().execute(async trx => {
		await trx
			.updateTable('invitations')
			.set({revoked_at: new Date()})
			.where('email', '=', email)
			.where('accepted_at', 'is', null)
			.where('revoked_at', 'is', null)
			.execute();

		const result = await trx
			.insertInto('invitations')
			.values({
				email,
				name,
				token_hash: hashToken(token),
				permissions: JSON.stringify(valid),
				invited_by: invitedBy,
				created_at: new Date(),
				expires_at: expiresAt
			})
			.executeTakeFirst();

		return Number(result.insertId);
	});

	return {id, token, expiresAt};
};

/**
 * Looks up a still-usable invitation by raw token. Callers must not
 * distinguish "unknown", "expired", "revoked" and "already accepted" to the
 * client: all four answer with the same shape, so a stranger cannot probe which
 * tokens ever existed.
 */
export const findByToken = async (token: string): Promise<AcceptableInvitation | null> => {
	const row = await db
		.selectFrom('invitations')
		.select(['id', 'email', 'name', 'permissions'])
		.where('token_hash', '=', hashToken(token))
		.where('accepted_at', 'is', null)
		.where('revoked_at', 'is', null)
		.where('expires_at', '>', new Date())
		.executeTakeFirst();

	if (!row) {
		return null;
	}

	return {id: row.id, email: row.email, name: row.name, permissions: parsePermissions(row.permissions)};
};

/** Marks the invitation accepted. Conditional on it still being open so two
 *  concurrent accepts of the same link cannot both create an account. */
export const markAccepted = async (invitationId: number): Promise<boolean> => {
	const result = await db
		.updateTable('invitations')
		.set({accepted_at: new Date()})
		.where('id', '=', invitationId)
		.where('accepted_at', 'is', null)
		.where('revoked_at', 'is', null)
		.executeTakeFirst();

	return Number(result.numUpdatedRows) > 0;
};

/**
 * Reverses markAccepted. Used only to compensate a failed acceptance: the user
 * could not be created, so the link must become usable again rather than
 * stranding the invitee with a burnt token and no account.
 */
export const unmarkAccepted = async (invitationId: number): Promise<void> => {
	await db
		.updateTable('invitations')
		.set({accepted_at: null})
		.where('id', '=', invitationId)
		.execute();
};

export const listOpenInvitations = async (): Promise<OpenInvitation[]> => {
	const rows = await db
		.selectFrom('invitations')
		.select(['id', 'email', 'name', 'permissions', 'invited_by', 'created_at', 'expires_at'])
		.where('accepted_at', 'is', null)
		.where('revoked_at', 'is', null)
		.where('expires_at', '>', new Date())
		.orderBy('created_at', 'desc')
		.execute();

	return rows.map(row => ({
		id: row.id,
		email: row.email,
		name: row.name,
		permissions: parsePermissions(row.permissions),
		invitedBy: row.invited_by,
		createdAt: row.created_at,
		expiresAt: row.expires_at
	}));
};

export const getOpenInvitation = async (invitationId: number): Promise<OpenInvitation | null> => {
	const all = await listOpenInvitations();
	return all.find(invitation => invitation.id === invitationId) ?? null;
};

/** Resend issues a *new* token and expiry and invalidates the old one, rather
 *  than re-mailing the existing link: if the first mail leaked, resending it
 *  would extend the leak's lifetime. */
export const resendInvitation = async (
	invitationId: number
): Promise<{token: string; email: string; name: string; expiresAt: Date} | null> => {
	const invitation = await getOpenInvitation(invitationId);
	if (!invitation) {
		return null;
	}

	const token = generateToken();
	const expiresAt = expiryFromNow();

	await db
		.updateTable('invitations')
		.set({token_hash: hashToken(token), expires_at: expiresAt, created_at: new Date()})
		.where('id', '=', invitationId)
		.execute();

	return {token, email: invitation.email, name: invitation.name, expiresAt};
};

export const revokeInvitation = async (invitationId: number): Promise<boolean> => {
	const result = await db
		.updateTable('invitations')
		.set({revoked_at: new Date()})
		.where('id', '=', invitationId)
		.where('accepted_at', 'is', null)
		.where('revoked_at', 'is', null)
		.executeTakeFirst();

	return Number(result.numUpdatedRows) > 0;
};

/** Used by the bootstrap to stay idempotent across restarts. */
export const hasOpenInvitationFor = async (email: string): Promise<boolean> => {
	const row = await db
		.selectFrom('invitations')
		.select('id')
		.where('email', '=', email)
		.where('accepted_at', 'is', null)
		.where('revoked_at', 'is', null)
		.where('expires_at', '>', new Date())
		.executeTakeFirst();

	return Boolean(row);
};