deps-parser.js

var Emitter  = require('./emitter'),
    utils    = require('./utils'),
    Observer = require('./observer'),
    catcher  = new Emitter()

/**
 *  Auto-extract the dependencies of a computed property
 *  by recording the getters triggered when evaluating it.
 */
function catchDeps (binding) {
    if (binding.isFn) return
    utils.log('\n- ' + binding.key)
    var got = utils.hash()
    binding.deps = []
    catcher.on('get', function (dep) {
        var has = got[dep.key]
        if (
            // avoid duplicate bindings
            (has && has.compiler === dep.compiler) ||
            // avoid repeated items as dependency
            // only when the binding is from self or the parent chain
            (dep.compiler.repeat && !isParentOf(dep.compiler, binding.compiler))
        ) {
            return
        }
        got[dep.key] = dep
        utils.log('  - ' + dep.key)
        binding.deps.push(dep)
        dep.subs.push(binding)
    })
    binding.value.$get()
    catcher.off('get')
}

/**
 *  Test if A is a parent of or equals B
 */
function isParentOf (a, b) {
    while (b) {
        if (a === b) {
            return true
        }
        b = b.parent
    }
}

module.exports = {

    /**
     *  the observer that catches events triggered by getters
     */
    catcher: catcher,

    /**
     *  parse a list of computed property bindings
     */
    parse: function (bindings) {
        utils.log('\nparsing dependencies...')
        Observer.shouldGet = true
        bindings.forEach(catchDeps)
        Observer.shouldGet = false
        utils.log('\ndone.')
    }
    
}