(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
  typeof define === 'function' && define.amd ? define(['exports'], factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.riotDOMBindings = {}));
})(this, (function (exports) { 'use strict';

  /**
   * Convert a string from camel case to dash-case
   * @param   {string} string - probably a component tag name
   * @returns {string} component name normalized
   */

  /**
   * Convert a string containing dashes to camel case
   * @param   {string} string - input string
   * @returns {string} my-string -> myString
   */
  function dashToCamelCase(string) {
    return string.replace(/-(\w)/g, (_, c) => c.toUpperCase())
  }

  /**
   * Move all the child nodes from a source tag to another
   * @param   {HTMLElement} source - source node
   * @param   {HTMLElement} target - target node
   * @returns {undefined} it's a void method ¯\_(ツ)_/¯
   */

  // Ignore this helper because it's needed only for svg tags
  function moveChildren(source, target) {
    if (source.firstChild) {
      target.appendChild(source.firstChild);
      moveChildren(source, target);
    }
  }

  /**
   * Remove the child nodes from any DOM node
   * @param   {HTMLElement} node - target node
   * @returns {undefined}
   */
  function cleanNode(node) {
    clearChildren(node.childNodes);
  }

  /**
   * Clear multiple children in a node
   * @param   {HTMLElement[]} children - direct children nodes
   * @returns {undefined}
   */
  function clearChildren(children) {
    Array.from(children).forEach(removeChild);
  }


  /**
   * Remove a node
   * @param {HTMLElement}node - node to remove
   * @returns {undefined}
   */
  const removeChild = node => node && node.parentNode && node.parentNode.removeChild(node);

  /**
   * Insert before a node
   * @param {HTMLElement} newNode - node to insert
   * @param {HTMLElement} refNode - ref child
   * @returns {undefined}
   */
  const insertBefore = (newNode, refNode) => refNode && refNode.parentNode && refNode.parentNode.insertBefore(newNode, refNode);

  /**
   * Replace a node
   * @param {HTMLElement} newNode - new node to add to the DOM
   * @param {HTMLElement} replaced - node to replace
   * @returns {undefined}
   */
  const replaceChild = (newNode, replaced) => replaced && replaced.parentNode && replaced.parentNode.replaceChild(newNode, replaced);

  // Riot.js constants that can be used accross more modules

  const IS_PURE_SYMBOL = Symbol('pure'),
    PARENT_KEY_SYMBOL = Symbol('parent');

  const EACH = 0;
  const IF = 1;
  const SIMPLE = 2;
  const TAG = 3;
  const SLOT = 4;

  var bindingTypes = {
    EACH,
    IF,
    SIMPLE,
    TAG,
    SLOT
  };

  const ATTRIBUTE = 0;
  const EVENT = 1;
  const TEXT = 2;
  const VALUE = 3;

  var expressionTypes = {
    ATTRIBUTE,
    EVENT,
    TEXT,
    VALUE
  };

  const HEAD_SYMBOL = Symbol();
  const TAIL_SYMBOL = Symbol();

  /**
   * Create the <template> fragments text nodes
   * @return {Object} {{head: Text, tail: Text}}
   */
  function createHeadTailPlaceholders() {
    const head = document.createTextNode('');
    const tail = document.createTextNode('');

    head[HEAD_SYMBOL] = true;
    tail[TAIL_SYMBOL] = true;

    return {head, tail}
  }

  /**
   * Create the template meta object in case of <template> fragments
   * @param   {TemplateChunk} componentTemplate - template chunk object
   * @returns {Object} the meta property that will be passed to the mount function of the TemplateChunk
   */
  function createTemplateMeta(componentTemplate) {
    const fragment = componentTemplate.dom.cloneNode(true);
    const {head, tail} = createHeadTailPlaceholders();

    return {
      avoidDOMInjection: true,
      fragment,
      head,
      tail,
      children: [head, ...Array.from(fragment.childNodes), tail]
    }
  }

  /**
   * Helper function to set an immutable property
   * @param   {Object} source - object where the new property will be set
   * @param   {string} key - object key where the new property will be stored
   * @param   {*} value - value of the new property
   * @param   {Object} options - set the propery overriding the default options
   * @returns {Object} - the original object modified
   */
  function defineProperty(source, key, value, options = {}) {
    /* eslint-disable fp/no-mutating-methods */
    Object.defineProperty(source, key, {
      value,
      enumerable: false,
      writable: false,
      configurable: true,
      ...options
    });
    /* eslint-enable fp/no-mutating-methods */

    return source
  }

  /**
   * Quick type checking
   * @param   {*} element - anything
   * @param   {string} type - type definition
   * @returns {boolean} true if the type corresponds
   */
  function checkType(element, type) {
    return typeof element === type
  }

  /**
   * Check if an element is part of an svg
   * @param   {HTMLElement}  el - element to check
   * @returns {boolean} true if we are in an svg context
   */
  function isSvg(el) {
    const owner = el.ownerSVGElement;

    return !!owner || owner === null
  }

  /**
   * Check if an element is a template tag
   * @param   {HTMLElement}  el - element to check
   * @returns {boolean} true if it's a <template>
   */
  function isTemplate(el) {
    return el.tagName.toLowerCase() === 'template'
  }

  /**
   * Check that will be passed if its argument is a function
   * @param   {*} value - value to check
   * @returns {boolean} - true if the value is a function
   */
  function isFunction(value) {
    return checkType(value, 'function')
  }

  /**
   * Check if a value is a Boolean
   * @param   {*}  value - anything
   * @returns {boolean} true only for the value is a boolean
   */
  function isBoolean(value) {
    return checkType(value, 'boolean')
  }

  /**
   * Check if a value is an Object
   * @param   {*}  value - anything
   * @returns {boolean} true only for the value is an object
   */
  function isObject(value) {
    return !isNil(value) && value.constructor === Object
  }

  /**
   * Check if a value is null or undefined
   * @param   {*}  value - anything
   * @returns {boolean} true only for the 'undefined' and 'null' types
   */
  function isNil(value) {
    return value === null || value === undefined
  }

  /**
   * ISC License
   *
   * Copyright (c) 2020, Andrea Giammarchi, @WebReflection
   *
   * Permission to use, copy, modify, and/or distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
   * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
   * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
   * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
   * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
   * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
   * PERFORMANCE OF THIS SOFTWARE.
   */

  // fork of https://github.com/WebReflection/udomdiff version 1.1.0
  // due to https://github.com/WebReflection/udomdiff/pull/2
  /* eslint-disable */

  /**
   * @param {Node[]} a The list of current/live children
   * @param {Node[]} b The list of future children
   * @param {(entry: Node, action: number) => Node} get
   * The callback invoked per each entry related DOM operation.
   * @param {Node} [before] The optional node used as anchor to insert before.
   * @returns {Node[]} The same list of future children.
   */
  var udomdiff = (a, b, get, before) => {
    const bLength = b.length;
    let aEnd = a.length;
    let bEnd = bLength;
    let aStart = 0;
    let bStart = 0;
    let map = null;
    while (aStart < aEnd || bStart < bEnd) {
      // append head, tail, or nodes in between: fast path
      if (aEnd === aStart) {
        // we could be in a situation where the rest of nodes that
        // need to be added are not at the end, and in such case
        // the node to `insertBefore`, if the index is more than 0
        // must be retrieved, otherwise it's gonna be the first item.
        const node = bEnd < bLength ?
          (bStart ?
            (get(b[bStart - 1], -0).nextSibling) :
            get(b[bEnd - bStart], 0)) :
          before;
        while (bStart < bEnd)
          insertBefore(get(b[bStart++], 1), node);
      }
      // remove head or tail: fast path
      else if (bEnd === bStart) {
        while (aStart < aEnd) {
          // remove the node only if it's unknown or not live
          if (!map || !map.has(a[aStart]))
            removeChild(get(a[aStart], -1));
          aStart++;
        }
      }
      // same node: fast path
      else if (a[aStart] === b[bStart]) {
        aStart++;
        bStart++;
      }
      // same tail: fast path
      else if (a[aEnd - 1] === b[bEnd - 1]) {
        aEnd--;
        bEnd--;
      }
      // The once here single last swap "fast path" has been removed in v1.1.0
      // https://github.com/WebReflection/udomdiff/blob/single-final-swap/esm/index.js#L69-L85
      // reverse swap: also fast path
      else if (
        a[aStart] === b[bEnd - 1] &&
        b[bStart] === a[aEnd - 1]
      ) {
        // this is a "shrink" operation that could happen in these cases:
        // [1, 2, 3, 4, 5]
        // [1, 4, 3, 2, 5]
        // or asymmetric too
        // [1, 2, 3, 4, 5]
        // [1, 2, 3, 5, 6, 4]
        const node = get(a[--aEnd], -1).nextSibling;
        insertBefore(
          get(b[bStart++], 1),
          get(a[aStart++], -1).nextSibling
        );
        insertBefore(get(b[--bEnd], 1), node);
        // mark the future index as identical (yeah, it's dirty, but cheap 👍)
        // The main reason to do this, is that when a[aEnd] will be reached,
        // the loop will likely be on the fast path, as identical to b[bEnd].
        // In the best case scenario, the next loop will skip the tail,
        // but in the worst one, this node will be considered as already
        // processed, bailing out pretty quickly from the map index check
        a[aEnd] = b[bEnd];
      }
      // map based fallback, "slow" path
      else {
        // the map requires an O(bEnd - bStart) operation once
        // to store all future nodes indexes for later purposes.
        // In the worst case scenario, this is a full O(N) cost,
        // and such scenario happens at least when all nodes are different,
        // but also if both first and last items of the lists are different
        if (!map) {
          map = new Map;
          let i = bStart;
          while (i < bEnd)
            map.set(b[i], i++);
        }
        // if it's a future node, hence it needs some handling
        if (map.has(a[aStart])) {
          // grab the index of such node, 'cause it might have been processed
          const index = map.get(a[aStart]);
          // if it's not already processed, look on demand for the next LCS
          if (bStart < index && index < bEnd) {
            let i = aStart;
            // counts the amount of nodes that are the same in the future
            let sequence = 1;
            while (++i < aEnd && i < bEnd && map.get(a[i]) === (index + sequence))
              sequence++;
            // effort decision here: if the sequence is longer than replaces
            // needed to reach such sequence, which would brings again this loop
            // to the fast path, prepend the difference before a sequence,
            // and move only the future list index forward, so that aStart
            // and bStart will be aligned again, hence on the fast path.
            // An example considering aStart and bStart are both 0:
            // a: [1, 2, 3, 4]
            // b: [7, 1, 2, 3, 6]
            // this would place 7 before 1 and, from that time on, 1, 2, and 3
            // will be processed at zero cost
            if (sequence > (index - bStart)) {
              const node = get(a[aStart], 0);
              while (bStart < index)
                insertBefore(get(b[bStart++], 1), node);
            }
            // if the effort wasn't good enough, fallback to a replace,
            // moving both source and target indexes forward, hoping that some
            // similar node will be found later on, to go back to the fast path
            else {
              replaceChild(
                get(b[bStart++], 1),
                get(a[aStart++], -1)
              );
            }
          }
          // otherwise move the source forward, 'cause there's nothing to do
          else
            aStart++;
        }
        // this node has no meaning in the future list, so it's more than safe
        // to remove it, and check the next live node out instead, meaning
        // that only the live list index should be forwarded
        else
          removeChild(get(a[aStart++], -1));
      }
    }
    return b;
  };

  const UNMOUNT_SCOPE = Symbol('unmount');

  const EachBinding = {
    // dynamic binding properties
    // childrenMap: null,
    // node: null,
    // root: null,
    // condition: null,
    // evaluate: null,
    // template: null,
    // isTemplateTag: false,
    nodes: [],
    // getKey: null,
    // indexName: null,
    // itemName: null,
    // afterPlaceholder: null,
    // placeholder: null,

    // API methods
    mount(scope, parentScope) {
      return this.update(scope, parentScope)
    },
    update(scope, parentScope) {
      const {placeholder, nodes, childrenMap} = this;
      const collection = scope === UNMOUNT_SCOPE ? null : this.evaluate(scope);
      const items = collection ? Array.from(collection) : [];

      // prepare the diffing
      const {
        newChildrenMap,
        batches,
        futureNodes
      } = createPatch(items, scope, parentScope, this);

      // patch the DOM only if there are new nodes
      udomdiff(
        nodes,
        futureNodes,
        patch(
          Array.from(childrenMap.values()),
          parentScope
        ),
        placeholder
      );

      // trigger the mounts and the updates
      batches.forEach(fn => fn());

      // update the children map
      this.childrenMap = newChildrenMap;
      this.nodes = futureNodes;

      return this
    },
    unmount(scope, parentScope) {
      this.update(UNMOUNT_SCOPE, parentScope);

      return this
    }
  };

  /**
   * Patch the DOM while diffing
   * @param   {any[]} redundant - list of all the children (template, nodes, context) added via each
   * @param   {*} parentScope - scope of the parent template
   * @returns {Function} patch function used by domdiff
   */
  function patch(redundant, parentScope) {
    return (item, info) => {
      if (info < 0) {
        // get the last element added to the childrenMap saved previously
        const element = redundant[redundant.length - 1];

        if (element) {
          // get the nodes and the template in stored in the last child of the childrenMap
          const {template, nodes, context} = element;
          // remove the last node (notice <template> tags might have more children nodes)
          nodes.pop();

          // notice that we pass null as last argument because
          // the root node and its children will be removed by domdiff
          if (!nodes.length) {
            // we have cleared all the children nodes and we can unmount this template
            redundant.pop();
            template.unmount(context, parentScope, null);
          }
        }
      }

      return item
    }
  }

  /**
   * Check whether a template must be filtered from a loop
   * @param   {Function} condition - filter function
   * @param   {Object} context - argument passed to the filter function
   * @returns {boolean} true if this item should be skipped
   */
  function mustFilterItem(condition, context) {
    return condition ? !condition(context) : false
  }

  /**
   * Extend the scope of the looped template
   * @param   {Object} scope - current template scope
   * @param   {Object} options - options
   * @param   {string} options.itemName - key to identify the looped item in the new context
   * @param   {string} options.indexName - key to identify the index of the looped item
   * @param   {number} options.index - current index
   * @param   {*} options.item - collection item looped
   * @returns {Object} enhanced scope object
   */
  function extendScope(scope, {itemName, indexName, index, item}) {
    defineProperty(scope, itemName, item);
    if (indexName) defineProperty(scope, indexName, index);

    return scope
  }

  /**
   * Loop the current template items
   * @param   {Array} items - expression collection value
   * @param   {*} scope - template scope
   * @param   {*} parentScope - scope of the parent template
   * @param   {EachBinding} binding - each binding object instance
   * @returns {Object} data
   * @returns {Map} data.newChildrenMap - a Map containing the new children template structure
   * @returns {Array} data.batches - array containing the template lifecycle functions to trigger
   * @returns {Array} data.futureNodes - array containing the nodes we need to diff
   */
  function createPatch(items, scope, parentScope, binding) {
    const {condition, template, childrenMap, itemName, getKey, indexName, root, isTemplateTag} = binding;
    const newChildrenMap = new Map();
    const batches = [];
    const futureNodes = [];

    items.forEach((item, index) => {
      const context = extendScope(Object.create(scope), {itemName, indexName, index, item});
      const key = getKey ? getKey(context) : index;
      const oldItem = childrenMap.get(key);
      const nodes = [];

      if (mustFilterItem(condition, context)) {
        return
      }

      const mustMount = !oldItem;
      const componentTemplate = oldItem ? oldItem.template : template.clone();
      const el = componentTemplate.el || root.cloneNode();
      const meta = isTemplateTag && mustMount ? createTemplateMeta(componentTemplate) : componentTemplate.meta;

      if (mustMount) {
        batches.push(() => componentTemplate.mount(el, context, parentScope, meta));
      } else {
        batches.push(() => componentTemplate.update(context, parentScope));
      }

      // create the collection of nodes to update or to add
      // in case of template tags we need to add all its children nodes
      if (isTemplateTag) {
        nodes.push(...meta.children);
      } else {
        nodes.push(el);
      }

      // delete the old item from the children map
      childrenMap.delete(key);
      futureNodes.push(...nodes);

      // update the children map
      newChildrenMap.set(key, {
        nodes,
        template: componentTemplate,
        context,
        index
      });
    });

    return {
      newChildrenMap,
      batches,
      futureNodes
    }
  }

  function create$6(node, {evaluate, condition, itemName, indexName, getKey, template}) {
    const placeholder = document.createTextNode('');
    const root = node.cloneNode();

    insertBefore(placeholder,  node);
    removeChild(node);

    return {
      ...EachBinding,
      childrenMap: new Map(),
      node,
      root,
      condition,
      evaluate,
      isTemplateTag: isTemplate(root),
      template: template.createDOM(node),
      getKey,
      indexName,
      itemName,
      placeholder
    }
  }

  /**
   * Binding responsible for the `if` directive
   */
  const IfBinding = {
    // dynamic binding properties
    // node: null,
    // evaluate: null,
    // isTemplateTag: false,
    // placeholder: null,
    // template: null,

    // API methods
    mount(scope, parentScope) {
      return this.update(scope, parentScope)
    },
    update(scope, parentScope) {
      const value = !!this.evaluate(scope);
      const mustMount = !this.value && value;
      const mustUnmount = this.value && !value;
      const mount = () => {
        const pristine = this.node.cloneNode();

        insertBefore(pristine, this.placeholder);
        this.template = this.template.clone();
        this.template.mount(pristine, scope, parentScope);
      };

      switch (true) {
      case mustMount:
        mount();
        break
      case mustUnmount:
        this.unmount(scope);
        break
      default:
        if (value) this.template.update(scope, parentScope);
      }

      this.value = value;

      return this
    },
    unmount(scope, parentScope) {
      this.template.unmount(scope, parentScope, true);

      return this
    }
  };

  function create$5(node, { evaluate, template }) {
    const placeholder = document.createTextNode('');

    insertBefore(placeholder, node);
    removeChild(node);

    return {
      ...IfBinding,
      node,
      evaluate,
      placeholder,
      template: template.createDOM(node)
    }
  }

  /**
   * Throw an error with a descriptive message
   * @param   { string } message - error message
   * @returns { undefined } hoppla.. at this point the program should stop working
   */
  function panic(message) {
    throw new Error(message)
  }
  /**
   * Returns the memoized (cached) function.
   * // borrowed from https://www.30secondsofcode.org/js/s/memoize
   * @param {Function} fn - function to memoize
   * @returns {Function} memoize function
   */
  function memoize(fn) {
    const cache = new Map();
    const cached = val => {
      return cache.has(val) ? cache.get(val) : cache.set(val, fn.call(this, val)) && cache.get(val)
    };
    cached.cache = cache;
    return cached
  }

  /**
   * Evaluate a list of attribute expressions
   * @param   {Array} attributes - attribute expressions generated by the riot compiler
   * @returns {Object} key value pairs with the result of the computation
   */
  function evaluateAttributeExpressions(attributes) {
    return attributes.reduce((acc, attribute) => {
      const {value, type} = attribute;

      switch (true) {
      // spread attribute
      case !attribute.name && type === ATTRIBUTE:
        return {
          ...acc,
          ...value
        }
      // value attribute
      case type === VALUE:
        acc.value = attribute.value;
        break
      // normal attributes
      default:
        acc[dashToCamelCase(attribute.name)] = attribute.value;
      }

      return acc
    }, {})
  }

  const ElementProto = typeof Element === 'undefined' ? {} : Element.prototype;
  const isNativeHtmlProperty = memoize(name => ElementProto.hasOwnProperty(name) ); // eslint-disable-line

  /**
   * Add all the attributes provided
   * @param   {HTMLElement} node - target node
   * @param   {Object} attributes - object containing the attributes names and values
   * @returns {undefined} sorry it's a void function :(
   */
  function setAllAttributes(node, attributes) {
    Object
      .entries(attributes)
      .forEach(([name, value]) => attributeExpression(node, { name }, value));
  }

  /**
   * Remove all the attributes provided
   * @param   {HTMLElement} node - target node
   * @param   {Object} newAttributes - object containing all the new attribute names
   * @param   {Object} oldAttributes - object containing all the old attribute names
   * @returns {undefined} sorry it's a void function :(
   */
  function removeAllAttributes(node, newAttributes, oldAttributes) {
    const newKeys = newAttributes ? Object.keys(newAttributes) : [];

    Object
      .keys(oldAttributes)
      .filter(name => !newKeys.includes(name))
      .forEach(attribute => node.removeAttribute(attribute));
  }

  /**
   * Check whether the attribute value can be rendered
   * @param {*} value - expression value
   * @returns {boolean} true if we can render this attribute value
   */
  function canRenderAttribute(value) {
    return value === true || ['string', 'number'].includes(typeof value)
  }

  /**
   * Check whether the attribute should be removed
   * @param {*} value - expression value
   * @returns {boolean} boolean - true if the attribute can be removed}
   */
  function shouldRemoveAttribute(value) {
    return !value && value !== 0
  }

  /**
   * This methods handles the DOM attributes updates
   * @param   {HTMLElement} node - target node
   * @param   {Object} expression - expression object
   * @param   {string} expression.name - attribute name
   * @param   {*} value - new expression value
   * @param   {*} oldValue - the old expression cached value
   * @returns {undefined}
   */
  function attributeExpression(node, { name }, value, oldValue) {
    // is it a spread operator? {...attributes}
    if (!name) {
      if (oldValue) {
        // remove all the old attributes
        removeAllAttributes(node, value, oldValue);
      }

      // is the value still truthy?
      if (value) {
        setAllAttributes(node, value);
      }

      return
    }

    // handle boolean attributes
    if (
      !isNativeHtmlProperty(name) && (
        isBoolean(value) ||
        isObject(value) ||
        isFunction(value)
      )
    ) {
      node[name] = value;
    }

    if (shouldRemoveAttribute(value)) {
      node.removeAttribute(name);
    } else if (canRenderAttribute(value)) {
      node.setAttribute(name, normalizeValue(name, value));
    }
  }

  /**
   * Get the value as string
   * @param   {string} name - attribute name
   * @param   {*} value - user input value
   * @returns {string} input value as string
   */
  function normalizeValue(name, value) {
    // be sure that expressions like selected={ true } will be always rendered as selected='selected'
    return (value === true) ? name : value
  }

  const RE_EVENTS_PREFIX = /^on/;

  const getCallbackAndOptions = value => Array.isArray(value) ? value : [value, false];

  // see also https://medium.com/@WebReflection/dom-handleevent-a-cross-platform-standard-since-year-2000-5bf17287fd38
  const EventListener = {
    handleEvent(event) {
      this[event.type](event);
    }
  };
  const ListenersWeakMap = new WeakMap();

  const createListener = node => {
    const listener = Object.create(EventListener);
    ListenersWeakMap.set(node, listener);
    return listener
  };

  /**
   * Set a new event listener
   * @param   {HTMLElement} node - target node
   * @param   {Object} expression - expression object
   * @param   {string} expression.name - event name
   * @param   {*} value - new expression value
   * @returns {value} the callback just received
   */
  function eventExpression(node, { name }, value) {
    const normalizedEventName = name.replace(RE_EVENTS_PREFIX, '');
    const eventListener = ListenersWeakMap.get(node) || createListener(node);
    const [callback, options] = getCallbackAndOptions(value);
    const handler = eventListener[normalizedEventName];
    const mustRemoveEvent = handler && !callback;
    const mustAddEvent = callback && !handler;

    if (mustRemoveEvent) {
      node.removeEventListener(normalizedEventName, eventListener);
    }

    if (mustAddEvent) {
      node.addEventListener(normalizedEventName, eventListener, options);
    }

    eventListener[normalizedEventName] = callback;
  }

  /**
   * Normalize the user value in order to render a empty string in case of falsy values
   * @param   {*} value - user input value
   * @returns {string} hopefully a string
   */
  function normalizeStringValue(value) {
    return isNil(value) ? '' : value
  }

  /**
   * Get the the target text node to update or create one from of a comment node
   * @param   {HTMLElement} node - any html element containing childNodes
   * @param   {number} childNodeIndex - index of the text node in the childNodes list
   * @returns {Text} the text node to update
   */
  const getTextNode = (node, childNodeIndex) => {
    const target = node.childNodes[childNodeIndex];

    if (target.nodeType === Node.COMMENT_NODE) {
      const textNode = document.createTextNode('');
      node.replaceChild(textNode, target);

      return textNode
    }

    return target
  };

  /**
   * This methods handles a simple text expression update
   * @param   {HTMLElement} node - target node
   * @param   {Object} data - expression object
   * @param   {*} value - new expression value
   * @returns {undefined}
   */
  function textExpression(node, data, value) {
    node.data = normalizeStringValue(value);
  }

  /**
   * This methods handles the input fileds value updates
   * @param   {HTMLElement} node - target node
   * @param   {Object} expression - expression object
   * @param   {*} value - new expression value
   * @returns {undefined}
   */
  function valueExpression(node, expression, value) {
    node.value = normalizeStringValue(value);
  }

  var expressions = {
    [ATTRIBUTE]: attributeExpression,
    [EVENT]: eventExpression,
    [TEXT]: textExpression,
    [VALUE]: valueExpression
  };

  const Expression = {
    // Static props
    // node: null,
    // value: null,

    // API methods
    /**
     * Mount the expression evaluating its initial value
     * @param   {*} scope - argument passed to the expression to evaluate its current values
     * @returns {Expression} self
     */
    mount(scope) {
      // hopefully a pure function
      this.value = this.evaluate(scope);

      // IO() DOM updates
      apply(this, this.value);

      return this
    },
    /**
     * Update the expression if its value changed
     * @param   {*} scope - argument passed to the expression to evaluate its current values
     * @returns {Expression} self
     */
    update(scope) {
      // pure function
      const value = this.evaluate(scope);

      if (this.value !== value) {
        // IO() DOM updates
        apply(this, value);
        this.value = value;
      }

      return this
    },
    /**
     * Expression teardown method
     * @returns {Expression} self
     */
    unmount() {
      // unmount only the event handling expressions
      if (this.type === EVENT) apply(this, null);

      return this
    }
  };

  /**
   * IO() function to handle the DOM updates
   * @param {Expression} expression - expression object
   * @param {*} value - current expression value
   * @returns {undefined}
   */
  function apply(expression, value) {
    return expressions[expression.type](expression.node, expression, value, expression.value)
  }

  function create$4(node, data) {
    return {
      ...Expression,
      ...data,
      node: data.type === TEXT ?
        getTextNode(node, data.childNodeIndex) :
        node
    }
  }

  /**
   * Create a flat object having as keys a list of methods that if dispatched will propagate
   * on the whole collection
   * @param   {Array} collection - collection to iterate
   * @param   {Array<string>} methods - methods to execute on each item of the collection
   * @param   {*} context - context returned by the new methods created
   * @returns {Object} a new object to simplify the the nested methods dispatching
   */
  function flattenCollectionMethods(collection, methods, context) {
    return methods.reduce((acc, method) => {
      return {
        ...acc,
        [method]: (scope) => {
          return collection.map(item => item[method](scope)) && context
        }
      }
    }, {})
  }

  function create$3(node, { expressions }) {
    return {
      ...flattenCollectionMethods(
        expressions.map(expression => create$4(node, expression)),
        ['mount', 'update', 'unmount']
      )
    }
  }

  function extendParentScope(attributes, scope, parentScope) {
    if (!attributes || !attributes.length) return parentScope

    const expressions = attributes.map(attr => ({
      ...attr,
      value: attr.evaluate(scope)
    }));

    return Object.assign(
      Object.create(parentScope || null),
      evaluateAttributeExpressions(expressions)
    )
  }

  // this function is only meant to fix an edge case
  // https://github.com/riot/riot/issues/2842
  const getRealParent = (scope, parentScope) => scope[PARENT_KEY_SYMBOL] || parentScope;

  const SlotBinding = {
    // dynamic binding properties
    // node: null,
    // name: null,
    attributes: [],
    // template: null,

    getTemplateScope(scope, parentScope) {
      return extendParentScope(this.attributes, scope, parentScope)
    },

    // API methods
    mount(scope, parentScope) {
      const templateData = scope.slots ? scope.slots.find(({id}) => id === this.name) : false;
      const {parentNode} = this.node;
      const realParent = getRealParent(scope, parentScope);

      this.template = templateData && create(
        templateData.html,
        templateData.bindings
      ).createDOM(parentNode);

      if (this.template) {
        cleanNode(this.node);
        this.template.mount(this.node, this.getTemplateScope(scope, realParent), realParent);
        this.template.children = Array.from(this.node.childNodes);
      }

      moveSlotInnerContent(this.node);
      removeChild(this.node);

      return this
    },
    update(scope, parentScope) {
      if (this.template) {
        const realParent = getRealParent(scope, parentScope);
        this.template.update(this.getTemplateScope(scope, realParent), realParent);
      }

      return this
    },
    unmount(scope, parentScope, mustRemoveRoot) {
      if (this.template) {
        this.template.unmount(this.getTemplateScope(scope, parentScope), null, mustRemoveRoot);
      }

      return this
    }
  };

  /**
   * Move the inner content of the slots outside of them
   * @param   {HTMLElement} slot - slot node
   * @returns {undefined} it's a void method ¯\_(ツ)_/¯
   */
  function moveSlotInnerContent(slot) {
    const child = slot && slot.firstChild;

    if (!child) return

    insertBefore(child, slot);
    moveSlotInnerContent(slot);
  }

  /**
   * Create a single slot binding
   * @param   {HTMLElement} node - slot node
   * @param   {string} name - slot id
   * @param   {AttributeExpressionData[]} attributes - slot attributes
   * @returns {Object} Slot binding object
   */
  function createSlot(node, { name, attributes }) {
    return {
      ...SlotBinding,
      attributes,
      node,
      name
    }
  }

  /**
   * Create a new tag object if it was registered before, otherwise fallback to the simple
   * template chunk
   * @param   {Function} component - component factory function
   * @param   {Array<Object>} slots - array containing the slots markup
   * @param   {Array} attributes - dynamic attributes that will be received by the tag element
   * @returns {TagImplementation|TemplateChunk} a tag implementation or a template chunk as fallback
   */
  function getTag(component, slots = [], attributes = []) {
    // if this tag was registered before we will return its implementation
    if (component) {
      return component({slots, attributes})
    }

    // otherwise we return a template chunk
    return create(slotsToMarkup(slots), [
      ...slotBindings(slots), {
        // the attributes should be registered as binding
        // if we fallback to a normal template chunk
        expressions: attributes.map(attr => {
          return {
            type: ATTRIBUTE,
            ...attr
          }
        })
      }
    ])
  }


  /**
   * Merge all the slots bindings into a single array
   * @param   {Array<Object>} slots - slots collection
   * @returns {Array<Bindings>} flatten bindings array
   */
  function slotBindings(slots) {
    return slots.reduce((acc, {bindings}) => acc.concat(bindings), [])
  }

  /**
   * Merge all the slots together in a single markup string
   * @param   {Array<Object>} slots - slots collection
   * @returns {string} markup of all the slots in a single string
   */
  function slotsToMarkup(slots) {
    return slots.reduce((acc, slot) => {
      return acc + slot.html
    }, '')
  }


  const TagBinding = {
    // dynamic binding properties
    // node: null,
    // evaluate: null,
    // name: null,
    // slots: null,
    // tag: null,
    // attributes: null,
    // getComponent: null,

    mount(scope) {
      return this.update(scope)
    },
    update(scope, parentScope) {
      const name = this.evaluate(scope);

      // simple update
      if (name && name === this.name) {
        this.tag.update(scope);
      } else {
        // unmount the old tag if it exists
        this.unmount(scope, parentScope, true);

        // mount the new tag
        this.name = name;
        this.tag = getTag(this.getComponent(name), this.slots, this.attributes);
        this.tag.mount(this.node, scope);
      }

      return this
    },
    unmount(scope, parentScope, keepRootTag) {
      if (this.tag) {
        // keep the root tag
        this.tag.unmount(keepRootTag);
      }

      return this
    }
  };

  function create$2(node, {evaluate, getComponent, slots, attributes}) {
    return {
      ...TagBinding,
      node,
      evaluate,
      slots,
      attributes,
      getComponent
    }
  }

  var bindings = {
    [IF]: create$5,
    [SIMPLE]: create$3,
    [EACH]: create$6,
    [TAG]: create$2,
    [SLOT]: createSlot
  };

  /**
   * Text expressions in a template tag will get childNodeIndex value normalized
   * depending on the position of the <template> tag offset
   * @param   {Expression[]} expressions - riot expressions array
   * @param   {number} textExpressionsOffset - offset of the <template> tag
   * @returns {Expression[]} expressions containing the text expressions normalized
   */
  function fixTextExpressionsOffset(expressions, textExpressionsOffset) {
    return expressions.map(e => e.type === TEXT ? {
      ...e,
      childNodeIndex: e.childNodeIndex + textExpressionsOffset
    } : e)
  }

  /**
   * Bind a new expression object to a DOM node
   * @param   {HTMLElement} root - DOM node where to bind the expression
   * @param   {TagBindingData} binding - binding data
   * @param   {number|null} templateTagOffset - if it's defined we need to fix the text expressions childNodeIndex offset
   * @returns {Binding} Binding object
   */
  function create$1(root, binding, templateTagOffset) {
    const { selector, type, redundantAttribute, expressions } = binding;
    // find the node to apply the bindings
    const node = selector ? root.querySelector(selector) : root;

    // remove eventually additional attributes created only to select this node
    if (redundantAttribute) node.removeAttribute(redundantAttribute);
    const bindingExpressions = expressions || [];

    // init the binding
    return (bindings[type] || bindings[SIMPLE])(
      node,
      {
        ...binding,
        expressions: templateTagOffset && !selector ?
          fixTextExpressionsOffset(bindingExpressions, templateTagOffset) :
          bindingExpressions
      }
    )
  }

  // in this case a simple innerHTML is enough
  function createHTMLTree(html, root) {
    const template = isTemplate(root) ? root : document.createElement('template');
    template.innerHTML = html;
    return template.content
  }

  // for svg nodes we need a bit more work
  function createSVGTree(html, container) {
    // create the SVGNode
    const svgNode = container.ownerDocument.importNode(
      new window.DOMParser()
        .parseFromString(
          `<svg xmlns="http://www.w3.org/2000/svg">${html}</svg>`,
          'application/xml'
        )
        .documentElement,
      true
    );

    return svgNode
  }

  /**
   * Create the DOM that will be injected
   * @param {Object} root - DOM node to find out the context where the fragment will be created
   * @param   {string} html - DOM to create as string
   * @returns {HTMLDocumentFragment|HTMLElement} a new html fragment
   */
  function createDOMTree(root, html) {
    if (isSvg(root)) return createSVGTree(html, root)

    return createHTMLTree(html, root)
  }

  /**
   * Inject the DOM tree into a target node
   * @param   {HTMLElement} el - target element
   * @param   {DocumentFragment|SVGElement} dom - dom tree to inject
   * @returns {undefined}
   */
  function injectDOM(el, dom) {
    switch (true) {
    case isSvg(el):
      moveChildren(dom, el);
      break
    case isTemplate(el):
      el.parentNode.replaceChild(dom, el);
      break
    default:
      el.appendChild(dom);
    }
  }

  /**
   * Create the Template DOM skeleton
   * @param   {HTMLElement} el - root node where the DOM will be injected
   * @param   {string|HTMLElement} html - HTML markup or HTMLElement that will be injected into the root node
   * @returns {?DocumentFragment} fragment that will be injected into the root node
   */
  function createTemplateDOM(el, html) {
    return html && (typeof html === 'string' ?
      createDOMTree(el, html) :
      html)
  }

  /**
   * Get the offset of the <template> tag
   * @param {HTMLElement} parentNode - template tag parent node
   * @param {HTMLElement} el - the template tag we want to render
   * @param   {Object} meta - meta properties needed to handle the <template> tags in loops
   * @returns {number} offset of the <template> tag calculated from its siblings DOM nodes
   */
  function getTemplateTagOffset(parentNode, el, meta) {
    const siblings = Array.from(parentNode.childNodes);

    return Math.max(
      siblings.indexOf(el),
      siblings.indexOf(meta.head) + 1,
      0
    )
  }

  /**
   * Template Chunk model
   * @type {Object}
   */
  const TemplateChunk = {
    // Static props
    // bindings: null,
    // bindingsData: null,
    // html: null,
    // isTemplateTag: false,
    // fragment: null,
    // children: null,
    // dom: null,
    // el: null,

    /**
     * Create the template DOM structure that will be cloned on each mount
     * @param   {HTMLElement} el - the root node
     * @returns {TemplateChunk} self
     */
    createDOM(el) {
      // make sure that the DOM gets created before cloning the template
      this.dom = this.dom || createTemplateDOM(el, this.html) || document.createDocumentFragment();

      return this
    },

    // API methods
    /**
     * Attach the template to a DOM node
     * @param   {HTMLElement} el - target DOM node
     * @param   {*} scope - template data
     * @param   {*} parentScope - scope of the parent template tag
     * @param   {Object} meta - meta properties needed to handle the <template> tags in loops
     * @returns {TemplateChunk} self
     */
    mount(el, scope, parentScope, meta = {}) {
      if (!el) panic('Please provide DOM node to mount properly your template');

      if (this.el) this.unmount(scope);

      // <template> tags require a bit more work
      // the template fragment might be already created via meta outside of this call
      const {fragment, children, avoidDOMInjection} = meta;
      // <template> bindings of course can not have a root element
      // so we check the parent node to set the query selector bindings
      const {parentNode} = children ? children[0] : el;
      const isTemplateTag = isTemplate(el);
      const templateTagOffset = isTemplateTag ? getTemplateTagOffset(parentNode, el, meta) : null;

      // create the DOM if it wasn't created before
      this.createDOM(el);

      // create the DOM of this template cloning the original DOM structure stored in this instance
      // notice that if a documentFragment was passed (via meta) we will use it instead
      const cloneNode = fragment || this.dom.cloneNode(true);

      // store root node
      // notice that for template tags the root note will be the parent tag
      this.el = isTemplateTag ? parentNode : el;

      // create the children array only for the <template> fragments
      this.children = isTemplateTag ? children || Array.from(cloneNode.childNodes) : null;

      // inject the DOM into the el only if a fragment is available
      if (!avoidDOMInjection && cloneNode) injectDOM(el, cloneNode);

      // create the bindings
      this.bindings = this.bindingsData.map(binding => create$1(
        this.el,
        binding,
        templateTagOffset
      ));
      this.bindings.forEach(b => b.mount(scope, parentScope));

      // store the template meta properties
      this.meta = meta;

      return this
    },

    /**
     * Update the template with fresh data
     * @param   {*} scope - template data
     * @param   {*} parentScope - scope of the parent template tag
     * @returns {TemplateChunk} self
     */
    update(scope, parentScope) {
      this.bindings.forEach(b => b.update(scope, parentScope));

      return this
    },

    /**
     * Remove the template from the node where it was initially mounted
     * @param   {*} scope - template data
     * @param   {*} parentScope - scope of the parent template tag
     * @param   {boolean|null} mustRemoveRoot - if true remove the root element,
     * if false or undefined clean the root tag content, if null don't touch the DOM
     * @returns {TemplateChunk} self
     */
    unmount(scope, parentScope, mustRemoveRoot = false) {
      const el = this.el;

      if (!el) {
        return this
      }

      this.bindings.forEach(b => b.unmount(scope, parentScope, mustRemoveRoot));

      switch (true) {
      // pure components should handle the DOM unmount updates by themselves
      // for mustRemoveRoot === null don't touch the DOM
      case (el[IS_PURE_SYMBOL] || mustRemoveRoot === null):
        break

      // if children are declared, clear them
      // applicable for <template> and <slot/> bindings
      case Array.isArray(this.children):
        clearChildren(this.children);
        break

      // clean the node children only
      case !mustRemoveRoot:
        el.innerHTML = '';
        break

      // remove the root node only if the mustRemoveRoot is truly
      case !!mustRemoveRoot:
        removeChild(el);
        break
      }

      this.el = null;

      return this
    },

    /**
     * Clone the template chunk
     * @returns {TemplateChunk} a clone of this object resetting the this.el property
     */
    clone() {
      return {
        ...this,
        meta: {},
        el: null
      }
    }
  };


  /**
   * Create a template chunk wiring also the bindings
   * @param   {string|HTMLElement} html - template string
   * @param   {BindingData[]} bindings - bindings collection
   * @returns {TemplateChunk} a new TemplateChunk copy
   */
  function create(html, bindings = []) {
    return {
      ...TemplateChunk,
      html,
      bindingsData: bindings
    }
  }

  exports.bindingTypes = bindingTypes;
  exports.createBinding = create$1;
  exports.createExpression = create$4;
  exports.expressionTypes = expressionTypes;
  exports.template = create;

  Object.defineProperty(exports, '__esModule', { value: true });

}));
