git ssb

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var applyProperties = require('./lib/apply-properties')
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var isObservable = require('./is-observable')
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var parseTag = require('./lib/parse-tag')
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var caches = new global.WeakMap()
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module.exports = function (tag, attributes, children) {
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  return Element(global.document, null, tag, attributes, children)
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}
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module.exports.forDocument = function (document, namespace) {
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  return Element.bind(this, document, namespace)
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}
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module.exports.destroy = function (node) {
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  var data = caches.get(node)
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  if (data) {
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    Array.from(data.releases.values()).forEach(tryInvoke)
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    caches.delete(node)
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  }
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  applyProperties.destroy(node)
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}
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function Element (document, namespace, tagName, properties, children) {
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  if (!children && (Array.isArray(properties) || isText(properties))) {
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    children = properties
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    properties = null
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  }
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  properties = properties || {}
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  var tag = parseTag(tagName, properties, namespace)
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  var node = namespace
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    ? document.createElementNS(namespace, tag.tagName)
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    : document.createElement(tag.tagName)
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  if (!namespace) {
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    if (tag.id) {
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      node.id = tag.id
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    }
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    if (tag.classes && tag.classes.length) {
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      node.className = tag.classes.join(' ')
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    }
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  }
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  var data = {
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    targets: new Map(),
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    releases: new Map()
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  }
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  caches.set(node, data)
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  applyProperties(node, properties, namespace)
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  if (children != null) {
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    appendChild(document, node, data, children)
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  }
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  return node
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}
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function appendChild (document, target, data, node) {
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  if (Array.isArray(node)) {
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    node.forEach(function (child) {
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      appendChild(document, target, data, child)
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    })
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  } else if (isObservable(node)) {
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    var nodes = getNodes(document, resolve(node))
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    nodes.forEach(append, target)
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    data.targets.set(node, nodes)
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    data.releases.set(node, bind(document, node, data))
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  } else {
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    target.appendChild(getNode(document, node))
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  }
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}
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function append (child) {
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  this.appendChild(child)
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}
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function bind (document, obs, data) {
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  return obs(function (value) {
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    var oldNodes = data.targets.get(obs)
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    var newNodes = getNodes(document, value)
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    if (oldNodes) {
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      replace(oldNodes, newNodes)
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      data.targets.set(obs, newNodes)
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    }
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  })
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}
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function replace (oldNodes, newNodes) {
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  var parent = oldNodes[oldNodes.length - 1].parentNode
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  var marker = oldNodes[oldNodes.length - 1].nextSibling
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  oldNodes.filter(function (node) {
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    return !~newNodes.indexOf(node)
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  }).forEach(function (node) {
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    parent.removeChild(node)
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  })
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  if (marker) {
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    newNodes.forEach(function (node) {
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      parent.insertBefore(node, marker)
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    })
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  } else {
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    newNodes.forEach(function (node) {
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      parent.appendChild(node)
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    })
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  }
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}
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function isText (value) {
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  return typeof value === 'string' || typeof value === 'number' || typeof value === 'boolean'
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}
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function getNode (document, nodeOrText) {
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  if (nodeOrText == null) {
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    return document.createTextNode('')
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  } else if (isText(nodeOrText)) {
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    return document.createTextNode(nodeOrText.toString())
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  } else {
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    return nodeOrText
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  }
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}
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function getNodes (document, nodeOrNodes) {
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  if (Array.isArray(nodeOrNodes)) {
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    if (nodeOrNodes.length) {
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      var result = []
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      nodeOrNodes.forEach(function (item) {
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        if (Array.isArray(item)) {
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          getNodes(document, item).forEach(push, result)
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        } else {
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          result.push(getNode(document, item))
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        }
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      })
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      return result.map(getNode.bind(this, document))
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    } else {
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      return [getNode(document, null)]
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    }
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  } else {
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    return [getNode(document, nodeOrNodes)]
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  }
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}
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function push (item) {
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  this.push(item)
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}
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function resolve (source) {
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  return typeof source === 'function' ? source() : source
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}
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function tryInvoke (func) {
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  if (typeof func === 'function') {
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    func()
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  }
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}
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