cmus-remote-node/main.js

API to cmus-remote for controlling cmus

"use strict";

const spawn=require("child_process").spawn;

const READ_TIMEOUT=50;
const KILL_TIMEOUT=1000;

function mProcessClosed(){
	this._.open=false;
	if(this._.killtimeout){
		clearTimeout(this._.killtimeout);
	}
}

function mCheckQueue(){
	if(!this._.open){
		throw new Error("cmus-remote process was closed");
	}
	if(!this._.datahandler&&this._.queue.length>0){
		const [l,h,eR]=this._.queue.shift();
		// console.log("Committing write <<"+l+">>");
		this._.proc.stdin.write(l+"\n","utf8");
		if(eR){
			this._.datahandler=h;
		} else {
			h.call(this);
			mCheckQueue.call(this);
		}
	}
}

function mSubmitLine(line,expectResponse,handler){
	if(!handler)throw 0;
	this._.queue.push([line,handler,expectResponse]);
	mCheckQueue.call(this);
}

class CmusRemote{
	constructor(socketloc /* optional */){
		this._={};

		let args=[];
		if(socketloc)args=args.concat(["--server",socketloc]);
		this._.proc=spawn("cmus-remote",args,{
			stdio: ["pipe","pipe",process.stderr]
		});
		this._.open=true;

		this._.proc.on("close",mProcessClosed.bind(this));
		this._.proc.on("exit",mProcessClosed.bind(this));
		this._.proc.on("error",(err)=>{
			throw err;
		});

		this._.queue=[];

		let buffer="";
		this._.proc.stdout.on("data",(data)=>{
			if(data instanceof Buffer){
				data=new String(data);
			}
			buffer+=data;
			if(this._.readtimeout){
				clearTimeout(this._.readtimeout);
			}
			this._.readtimeout=setTimeout((()=>{
				// console.log("Readtimeout: buffer=<<"+buffer+">>, datahandler=<<"+this._.datahandler+">>, queue=<<"+this._.queue+">>");
				if(buffer.length>0&&this._.datahandler){
					let e=null;
					try {
						this._.datahandler.call(this,buffer);
					} catch(err){
						e=err;
					}
					buffer="";
					this._.datahandler=null;
					mCheckQueue.call(this);
					if(e)throw e;
				}
			}).bind(this),READ_TIMEOUT);
		});
	}

	close(){
		this._.proc.stdin.end();
		this._.killtimeout=setTimeout((()=>{
			this._.proc.kill("SIGTERM");
			this._.killtimeout=setTimeout((()=>{
				this._.proc.kill("SIGKILL");
				this._.killtimeout=null;
			}).bind(this),KILL_TIMEOUT);
		}).bind(this),KILL_TIMEOUT);
	}

	ready(){
		return this._.open;
	}

	status(cb){
		mSubmitLine.call(this,"status",true,(str)=>{
			// console.log("Status internal callback called");
			const lines=str.split("\n");
			const obj={
				track: {},
				settings: {}
			};
			for(const line of lines){
				if(line.length==0)continue;
				const idx=line.indexOf(" ");
				if(idx==-1){
					throw new Error("Unexpected line on 'status' output from cmus-remote: '"+line+"'");
				}
				const head=line.slice(0,idx),rest=line.slice(idx+1);
				if(head=="status"){
					obj.status=rest;
				} else if(head=="file"||head=="duration"||head=="position"){
					obj.track[head]=rest;
				} else if(head=="tag"||head=="set"){
					const idx=rest.indexOf(" ");
					if(idx==-1){
						throw new Error("Unexpected line on 'status' output from cmus-remote: '"+line+"'");
					}
					const tag=rest.slice(0,idx),rest2=rest.slice(idx+1);
					obj[head=="tag"?"track":"settings"][tag]=rest2;
				}
			}
			cb(obj);
		});
	}

	// This requests data of THE ENTIRE LIBRARY. Use with care on large libraries.
	getLibrary(cb){
		mSubmitLine.call(this,"save -e -l -",true,(str)=>{
			const lines=str.split("\n");
			const tracks=[];
			let track=null;
			for(const line of lines){
				if(line.length==0)continue;
				const idx=line.indexOf(" ");
				if(idx==-1){
					throw new Error("Unexpected line on 'save -l -' output from cmus-remote: '"+line+"'");
				}
				const head=line.slice(0,idx),rest=line.slice(idx+1);
				if(head=="file"){
					if(track)tracks.push(track);
					track={};
					track.file=rest;
					continue;
				}
				if(!track){
					throw new Error("Expected 'file' key on output 'save -l -' from cmus-remote: '"+line+"'");
				}
				if(head=="duration"||head=="codec"||head=="bitrate"){
					track[head]=rest;
				} else if(head=="tag"){
					const idx=rest.indexOf(" ");
					if(idx==-1){
						throw new Error("Unexpected line on 'save -l -' output from cmus-remote: '"+line+"'");
					}
					const tag=rest.slice(0,idx),rest2=rest.slice(idx+1);
					track[tag]=rest2;
				}
			}
			if(track)tracks.push(track);
			cb(tracks);
		});
	}

	play(filename /* optional */){
		mSubmitLine.call(this,"player-play"+(filename?" "+filename:""),false,()=>{});
	}

	pause(){
		mSubmitLine.call(this,"player-pause",false,()=>{});
	}

	next(){
		mSubmitLine.call(this,"player-next",false,()=>{});
	}

	prev(){
		mSubmitLine.call(this,"player-prev",false,()=>{});
	}

	stop(){
		mSubmitLine.call(this,"player-stop",false,()=>{});
	}

	/* From the cmus man page:
	 *
	 * seek [+-](<num>[mh] | [HH:]MM:SS)
	 *     Seek to absolute or relative position.  Position can be given in seconds,
	 *     minutes (m), hours (h) or HH:MM:SS format where HH: is optional.
	 *
	 *     Seek 1 minute backward
	 *         :seek -1m
	 *
	 *     Seek 5 seconds forward
	 *         :seek +5
	 *
	 *     Seek to absolute position 1h
	 *         :seek 1h
	 *
	 *     Seek 90 seconds forward
	 *         :seek +1:30
	 */
	seek(repr){
		mSubmitLine.call(this,"seek "+repr,false,()=>{});
	}
}

module.exports=CmusRemote;