import fs from "fs";
import path from "path";

import * as core from "@actions/core";

interface FileInfo
{
	name: string;
	contents: string;
	options: fs.WriteFileOptions;
}

/**
 * main function
 */
function main(): void
{
	try
	{
		// parameters
		const key = core.getInput("key", {
			required: true,
		});
		const name = core.getInput("name");
		const knownHosts = core.getInput("known_hosts", {
			required: true,
		});
		const config = core.getInput("config");
		const ifKeyExists = core.getInput("if_key_exists");

		// create ".ssh" directory
		const home = getHomeDirectory();
		const dirName = path.resolve(home, ".ssh");
		fs.mkdirSync(dirName, {
			recursive: true,
			mode: 0o700,
		});

		// files to be created
		const files: FileInfo[] = [
			{
				name: "known_hosts",
				contents: insertLf(knownHosts, true, true),
				options: {
					mode: 0o644,
					flag: "a",
				},
			},
			{
				name: "config",
				contents: insertLf(config, true, true),
				options: {
					mode: 0o644,
					flag: "a",
				},
			},
		];
		if(shouldCreateKeyFile(path.join(dirName, name), ifKeyExists))
		{
			files.push({
				name: name,
				contents: insertLf(key, false, true),
				options: {
					mode: 0o400,
					flag: "ax",
				},
			});
		}

		// create files
		for(const file of files)
		{
			const fileName = path.join(dirName, file.name);
			fs.writeFileSync(fileName, file.contents, file.options);
		}

		console.log(`SSH key has been stored to ${dirName} successfully.`);
	}
	catch(err)
	{
		core.setFailed(err.message);
	}
}

/**
 * get home directory
 * @returns home directory
 */
function getHomeDirectory(): string
{
	const homeEnv = getHomeEnv();
	const home = process.env[homeEnv];
	if(home === undefined)
	{
		throw Error(`${homeEnv} is not defined`);
	}

	if(home === "/github/home")
	{
		// Docker container
		return "/root";
	}

	return home;
}

/**
 * get HOME environment name
 * @returns HOME environment name
 */
function getHomeEnv(): string
{
	if(process.platform === "win32")
	{
		// Windows
		return "USERPROFILE";
	}

	// macOS / Linux
	return "HOME";
}

/**
 * prepend/append LF to value if not empty
 * @param value the value to insert LF
 * @param prepend true to prepend
 * @param append true to append
 * @returns new value
 */
function insertLf(value: string, prepend: boolean, append: boolean): string
{
	let affectedValue = value;

	if(value.length === 0)
	{
		// do nothing if empty
		return "";
	}
	if(prepend && !affectedValue.startsWith("\n"))
	{
		affectedValue = `\n${affectedValue}`;
	}
	if(append && !affectedValue.endsWith("\n"))
	{
		affectedValue = `${affectedValue}\n`;
	}

	return affectedValue;
}

/**
 * should create SSH key file?
 * @param keyFilePath path of key file
 * @param ifKeyExists action if SSH key exists
 * @returns Yes/No
 */
function shouldCreateKeyFile(keyFilePath: string, ifKeyExists: string): boolean
{
	if(!fs.existsSync(keyFilePath))
	{
		// should create if file does not exist
		return true;
	}

	switch(ifKeyExists)
	{
	case "replace":
		// remove file and should create if replace
		fs.unlinkSync(keyFilePath);
		return true;

	case "ignore":
		// should NOT create if ignore
		return false;

	default:
		// error otherwise
		throw new Error(`SSH key is already installed. Set "if_key_exists" to "replace" or "ignore" in order to avoid this error.`);
	}
}

main();