/*

*** Publish/Subscribe global events functions - implementation of pubsub pattern for loose coupled components ***

Usage:

* Publish global application event:

publish("unique event name / category / subcategory", arg1, arg2, arg3);
or
publish(["event1", "event2", "event3"], arg1, arg2, arg3);


* Subscribe to global application event:
(as many subscribtions as neccessary)

subscribe("unique event name", (arg1, arg2, arg3) => { console.log("Do something useful on 'unique event name'..."); });
or
subscribe(["event1", "event2", "event3"], () => { console.log("Do something useful on those three events ..."); });


* To unsubscribe from global application event:
(which may be necessary on componentWillUnmount because react components can't update state when component isn't mounted)

let ref = subscribe("unique event name", (arg1, arg2, arg3) => { });
unsubscribe("unique event name", ref);

unsubscribe will return true if event or events where unsubscribed
*/
const
    _entries = {};

export const
    subscribe = (name, handler) => {
        const
            doSub = n => {
                let
                    entry = _entries[n];
                if (!entry) {
                    entry = _entries[n] = [];
                }
                return _entries[n].push(handler) - 1;
            };
        if (name instanceof Array) {
            let result = [];
            for(let i of name) {
                result.push({"name": i, index: doSub(i)});
            }
            return result;
        } else {
            return doSub(name);
        }
    };

export const
    unsubscribe = (name, ref) => {
        let
            result = false;
        if (ref instanceof Array === false) {
            ref = [{"name": name, index: ref}];
        }
        for(let item of ref) {
            let entry = _entries[item.name]
            if (!entry) {
                continue;
            }
            let index = entry.indexOf(item.index);
            if (index === -1) {
                continue;
            }
            entry.splice(index, 1);
            if (!result) {
                result = true;
            }
        }
        return result;
    };

export const
    publish = (name, ...args) => {
        const
            doPub = n => {
                const
                    entry = _entries[n];
                if (!entry) {
                    return;
                }
                entry.forEach(f => f.apply(this, args));
            };
        if (name instanceof Array) {
            for(let i of name) {
                doPub(i);
            }
        } else {
            doPub(name);
        }
    };