/**
 * Handles requests for route beneath a directory with a .spa file dropped in it.
 * @module
 */

import * as path from '@std/path';
import { PRECHECK, SERVER } from '../server.ts';
import { getCookies } from '@std/http/cookie';
import { load_html_with_ssi } from './html.ts';

async function find_spa_file_root(request_path: string): Promise<string | undefined> {
	let current_path = Deno.cwd();
	const relative_path = path.relative(current_path, request_path);
	const path_elements = relative_path.split('/').slice(0, -1);

	let element;

	while ((element = path_elements.shift())) {
		current_path = path.join(current_path, element);

		try {
			const spa_file_stat = await Deno.stat(path.join(current_path, '.spa'));

			if (spa_file_stat.isFile) {
				return current_path;
			}
		} catch (error) {
			if (error instanceof Deno.errors.NotFound) {
				continue;
			}

			throw error;
		}
	}

	return undefined;
}

export type HTTP_METHOD = 'GET' | 'PUT' | 'POST' | 'DELETE' | 'HEAD' | 'OPTIONS';
export type HANDLER_METHOD = (
	request: Request,
	normalized_path: string,
	server: SERVER
) => Promise<Response | undefined> | Response | undefined;
export const PRECHECKS: Partial<Record<HTTP_METHOD, PRECHECK[]>> = {};
export const HANDLERS: Partial<Record<HTTP_METHOD, HANDLER_METHOD>> = {
	HEAD: async (_request: Request, normalized_path: string, _server: SERVER): Promise<Response | undefined> => {
		const spa_root = await find_spa_file_root(normalized_path);
		if (!spa_root) {
			return;
		}

		for await (const index_filename of ['index.html', 'index.htm']) {
			try {
				const index_file_path = path.join(spa_root, index_filename);
				const index_file_stat = await Deno.stat(index_file_path);

				if (index_file_stat.isFile) {
					return new Response('', {
						headers: {
							'Content-Type': 'text/html',
							'Content-Length': `${index_file_stat.size}`,
							'Last-Modified': `${index_file_stat.mtime ?? index_file_stat.ctime}`
						}
					});
				}
			} catch (error) {
				if (error instanceof Deno.errors.NotFound) {
					continue;
				}

				throw error;
			}
		}
	},

	GET: async (request: Request, normalized_path: string, _server: SERVER): Promise<Response | undefined> => {
		const spa_root = await find_spa_file_root(normalized_path);
		if (!spa_root) {
			return;
		}

		for await (const index_filename of ['index.html', 'index.htm']) {
			try {
				const index_file_path = path.join(spa_root, index_filename);
				const index_file_stat = await Deno.stat(index_file_path);

				if (index_file_stat.isFile) {
					const processed: string = await load_html_with_ssi(index_file_path);

					const accepts = request.headers.get('accept') ?? 'text/html';
					if (!['*/*', 'text/html', 'text/plain'].includes(accepts)) {
						return new Response('unsupported accepts header for SPA: ' + accepts, {
							status: 400
						});
					}

					return new Response(processed, {
						headers: {
							'Content-Type': accepts === '*/*' ? 'text/html' : accepts
						}
					});
				}
			} catch (error) {
				if (error instanceof Deno.errors.NotFound) {
					continue;
				}

				throw error;
			}
		}
	},

	OPTIONS: async (request: Request, normalized_path: string): Promise<Response | undefined> => {
		const spa_root = await find_spa_file_root(normalized_path);
		if (!spa_root) {
			return;
		}

		for await (const index_filename of ['index.html', 'index.htm']) {
			try {
				const index_file_path = path.join(spa_root, index_filename);
				const index_file_stat = await Deno.stat(index_file_path);

				if (index_file_stat.isFile) {
					const accepts = request.headers.get('accept') ?? 'text/html';
					if (!['*/*', 'text/html', 'text/plain'].includes(accepts)) {
						return new Response('unsupported accepts header for SPA: ' + accepts, {
							status: 400
						});
					}

					const allowed = ['GET', 'HEAD', 'OPTIONS'];

					return new Response('', {
						headers: {
							'Allow': allowed.sort().join(','),
							'Access-Control-Allow-Origin': Deno.env.get('SERVERUS_ACCESS_CONTROL_ALLOW_ORIGIN') ?? '*'
						}
					});
				}
			} catch (error) {
				if (error instanceof Deno.errors.NotFound) {
					continue;
				}

				throw error;
			}
		}
	}
};

/**
 * Handles requests for static files.
 *
 * @param request The incoming HTTP request
 * @returns Either a response (a static file was requested and returned properly) or undefined if unhandled.
 */
export default async function handle_spa_files_in_path(request: Request, server: SERVER): Promise<Response | undefined> {
	const method: HTTP_METHOD = request.method.toUpperCase() as HTTP_METHOD;
	const handler: HANDLER_METHOD | undefined = HANDLERS[method];

	if (!handler) {
		return;
	}

	const url = new URL(request.url);
	const normalized_path = path.resolve(path.normalize(decodeURIComponent(url.pathname)).replace(/^\/+/, ''));

	// if they're requesting something outside the working dir, just bail
	if (!normalized_path.startsWith(Deno.cwd())) {
		return;
	}

	const prechecks: PRECHECK[] = PRECHECKS[method] ?? [];

	const cookies: Record<string, string> = getCookies(request.headers);
	const query = Object.fromEntries(new URL(request.url).searchParams.entries());

	const metadata = {
		cookies,
		query
	};

	for await (const precheck of prechecks) {
		const error_response: Response | undefined = await precheck(request, metadata);
		if (error_response) {
			return error_response;
		}
	}

	return await handler(request, normalized_path, server);
}