const logger = require('logplease').create('job');
const {v4: uuidv4} = require('uuid');
const cp = require('child_process');
const path = require('path');
const config = require('./config');
const globals = require('./globals');
const fs = require('fs/promises');
const ps_list = require('ps-list');
const wait_pid = require('waitpid');

const job_states = {
    READY: Symbol('Ready to be primed'),
    PRIMED: Symbol('Primed and ready for execution'),
    EXECUTED: Symbol('Executed and ready for cleanup')
};

let uid = 0;
let gid = 0;

class Job {

    constructor({ runtime, files, args, stdin, timeouts }) {
        this.uuid =  uuidv4();
        this.runtime = runtime;
        this.files = files.map((file,i) => ({
            name: file.name || `file${i}.code`,
            content: file.content
        }));
        
        this.args = args;
        this.stdin = stdin;
        this.timeouts = timeouts;

        this.uid = config.runner_uid_min + uid;
        this.gid = config.runner_gid_min + gid;

        uid++;
        gid++;

        uid %= (config.runner_uid_max - config.runner_uid_min) + 1;
        gid %= (config.runner_gid_max - config.runner_gid_min) + 1;


        this.state = job_states.READY;
        this.dir = path.join(config.data_directory, globals.data_directories.jobs, this.uuid);
    }

    async prime() {
        logger.info(`Priming job uuid=${this.uuid}`);

        logger.debug('Writing files to job cache');

        logger.debug(`Transfering ownership uid=${this.uid} gid=${this.gid}`);

        await fs.mkdir(this.dir, { mode:0o700 });
        await fs.chown(this.dir, this.uid, this.gid);

        for (const file of this.files) {
            let file_path = path.join(this.dir, file.name);

            await fs.write_file(file_path, file.content);
            await fs.chown(file_path, this.uid, this.gid);
        }

        this.state = job_states.PRIMED;

        logger.debug('Primed job');
    }

    async safe_call(file, args, timeout) {
        return new Promise((resolve, reject) => {
            const nonetwork = config.disable_networking ? ['nosocket'] : [];

            const prlimit = [
                'prlimit',
                '--nproc=' + config.max_process_count,
                '--nofile=' + config.max_open_files,
                '--fsize=' + config.max_file_size
            ];

            const proc_call = [
                ...prlimit,
                ...nonetwork,
                'bash',file,
                ...args
            ];

            var stdout = '';
            var stderr = '';
            var output = '';

            const proc = cp.spawn(proc_call[0], proc_call.splice(1) ,{
                env: { 
                    ...this.runtime.env_vars,
                    PISTON_LANGUAGE: this.runtime.language
                },
                stdio: 'pipe',
                cwd: this.dir,
                uid: this.uid,
                gid: this.gid,
                detached: true //give this process its own process group
            });

            proc.stdin.write(this.stdin);
            proc.stdin.end();
            proc.stdin.destroy();

            const kill_timeout = set_timeout(_ => proc.kill('SIGKILL'), timeout);

            proc.stderr.on('data', data => {
                if (stderr.length > config.output_max_size) {
                    proc.kill('SIGKILL');
                } else {
                    stderr += data;
                    output += data;
                }
            });

            proc.stdout.on('data', data => {
                if (stdout.length > config.output_max_size) {
                    proc.kill('SIGKILL');
                } else {
                    stdout += data;
                    output += data;
                }
            });

            const exit_cleanup = () => {
                clear_timeout(kill_timeout);

                proc.stderr.destroy();
                proc.stdout.destroy();
            };

            proc.on('exit', (code, signal)=>{
                exit_cleanup();

                resolve({ stdout, stderr, code, signal, output });
            });

            proc.on('error', (err) => {
                exit_cleanup();

                reject({ error: err, stdout, stderr, output });
            });
        });
    }

    async execute() {
        if (this.state !== job_states.PRIMED) {
            throw new Error('Job must be in primed state, current state: ' + this.state.toString());
        }

        logger.info(`Executing job uuid=${this.uuid} uid=${this.uid} gid=${this.gid} runtime=${this.runtime.toString()}`);

        logger.debug('Compiling');

        let compile;

        if (this.runtime.compiled) {
            compile = await this.safe_call(
                path.join(this.runtime.pkgdir, 'compile'),
                this.files.map(x => x.name),
                this.timeouts.compile
            );
        }

        logger.debug('Running');

        const run = await this.safe_call(
            path.join(this.runtime.pkgdir, 'run'),
            [this.files[0].name, ...this.args],
            this.timeouts.run
        );

        this.state = job_states.EXECUTED;

        return {
            compile,
            run,
            language: this.runtime.language,
            version: this.runtime.version.raw
        };
    }


    async cleanup_processes(){
        let processes = [1];
        while(processes.length > 0){
            processes = await ps_list();
            processes = processes.filter(proc => proc.uid == this.uid);

            for(const proc of processes){
                // First stop the processes, but keep their resources allocated so they cant re-fork
                try{
                    process.kill(proc.pid, 'SIGSTOP');
                }catch{
                    // Could already be dead
                }
            }


            for(const proc of processes){
                // Then clear them out of the process tree
                try{
                    process.kill(proc.pid, 'SIGKILL');
                }catch{
                    // Could already be dead and just needs to be waited on
                }
                wait_pid(proc.pid);
            }
        }
    }

    async cleanup_filesystem(){
        
        for (const clean_path of globals.clean_directories) {
            const contents = await fs.readdir(clean_path);

            for (const file of contents) {
                const file_path = path.join(clean_path, file);
                try{
                    const stat = await fs.stat(file_path);
                    if(stat.uid == this.uid)
                        await fs.rm(file_path,  { recursive: true, force: true });
                }catch(e){
                    // File was somehow deleted in the time that we read the dir to when we checked the file
                    logger.warn(`Error removing file ${file_path}: ${e}`)
                }
            }

        }

        await fs.rm(this.dir, { recursive: true, force: true });
    }

    async cleanup() {
        logger.info(`Cleaning up job uuid=${this.uuid}`);
        
        await Promise.all([
            this.cleanup_processes(),
            this.cleanup_filesystem()
        ]);
    }

}

module.exports = {
    Job
};