thunk.js

var cuid = require("cuid")

var dom = require("./render")
var diff = require("./diff")
var patch = require("./patch")
var isString = require("./lib/is-string")

/* Usage
var thunk = require("virtual-dom/thunk")

module.exports = thunk(function render(current, previous) {
    if (previous && previous.id === current.id) {
        return null
    }

    return h("div", current.value)
})
*/
module.exports = thunk

function thunk(type, render) {
    if (arguments.length === 1) {
        render = type
        type = null
    }

    function Thunk(state) {
        if (!(this instanceof Thunk)) {
            return new Thunk(state)
        }

        this.state = state
    }

    Thunk.prototype.type = isString(type) ? type : cuid()
    Thunk.prototype.render = render
    Thunk.prototype.init = initThunk
    Thunk.prototype.update = updateThunk

    return Thunk
}

function initThunk() {
    var vnode = this.vnode = this.render(this.state)
    return dom(vnode)
}

function updateThunk(previous, domNode) {
    var currentState = this.state
    var render = this.render

    var vnode = render(currentState, previous.state)

    if (vnode) {
        this.vnode = vnode
        patch(domNode, diff(previous.vnode, vnode))
    } else {
        this.vnode = previous.vnode
    }
}