import React from 'react';

const canUseDOM = !!(
    (typeof window !== 'undefined' && window.document && window.document.createElement)
);

export class StateTree
{
    state = {}
    subs = {}
    context = {}
    instance = null

    constructor(context)
    {
        this.context = context || {};
    }

    get()
    {
        return this.state;
    }

    set(state)
    {
        this.state = state;
    }

    setInstance(instance)
    {
        this.instance = instance;
    }

    update()
    {
        if (this.instance)
        {
            this.state = this.instance.state;
        }
        for (const k in this.subs)
        {
            this.subs[k].update();
        }
    }

    export()
    {
        const r = {
            state: this.state,
            subs: {},
        };
        for (const k in this.subs)
        {
            r.subs[k] = this.subs[k].export();
        }
        return r;
    }

    import(st)
    {
        this.state = st.state;
        this.subs = {};
        for (const k in st.subs)
        {
            this.sub(k).import(st.subs[k]);
        }
    }

    sub(key)
    {
        if (!this.subs[key])
        {
            this.subs[key] = new StateTree(this.context);
        }
        return this.subs[key];
    }
}

export class StateTreeComponent extends React.Component
{
    constructor(props)
    {
        super(props);
        if (props.state)
        {
            this.state = props.state.get();
            this.ctx = props.state.context;
            this.props.state.setInstance(this);
        }
    }

    componentWillUnmount()
    {
        if (this.props.state)
        {
            this.props.state.set(this.state);
            this.props.state.setInstance(null);
        }
    }
}