class Alert{
    constructor(alert_type, source, state) {
        // The type of alert.
        this.type = alert_type;
        // The source of the alert.
        this.source = source;
        // Other info in the alert.
        this.state = state;
        // The alert messages.
        if (alert_type=='signal'){
            this.msg = 'Signal state change: ' + this.source + ' = ' + this.state;
        }
        if (alert_type=='strategy'){
            this.msg = 'Strategy alert: ' + this.source + ' = ' + this.state;
        }
    }
    alert_source(){
        return this.source;
    }
    alert_type(){
        return this.type;
    }
    alert_state(){
        return this.state;
    }
    alert_msg(){
        return this.msg;
    }
}

class Alerts {
    constructor(target_id) {
        // The list of alert messages.
        this.alerts = [];
        // The html element id that displays the alert messages.
        this.target_id = target_id;
        // The html element that displays the alert messages.
        this.target = null;
    }
    publish_alerts(alert_type, data){
        if (alert_type == 'signal_changes'){
            // If the alert_type is signal changes then data will
            // contain a list of objects with format: { name: str, state: bool }
            console.log('publishing alerts')
            for(let sig in data){
                console.log('publishing single alert');
                this.alerts.push( new Alert('signal', sig, data[sig]) );
            }
            this.update_html();

        }
        if (alert_type == 'strategy'){
            // If the alert_type is strategy then data will
            // contain a list of objects with format: { name: str, state: bool }
            console.log('publishing strategy alerts')
            this.alerts.push( new Alert('strategy', 'source', data) );
            this.update_html();

        }
    }

    update_html(){
        let alerts ='';
        for (let index in this.alerts){
            let alert = this.alerts[index].alert_msg();
            alerts += '<span>' + alert + '</span><br>';
        }
        this.target.innerHTML = alerts;
    }

    set_target(){
        // This is called after the html document has been parsed.
        this.target = document.getElementById(this.target_id);
    }
}