/**
 * H3 v0.11.0 "Keen Klingon"
 * Copyright 2020 Fabio Cevasco <h3rald@h3rald.com>
 *
 * @license MIT
 * For the full license, see: https://github.com/h3rald/h3/blob/master/LICENSE
 */
const checkProperties = (obj1, obj2) => {
  if (Object.keys(obj1).length !== Object.keys(obj2).length) {
    return false;
  }
  for (const key in obj1) {
    if (!(key in obj2)) {
      return false;
    }
    if (!equal(obj1[key], obj2[key])) {
      return false;
    }
  }
  return true;
};

const equal = (obj1, obj2) => {
  if ((obj1 === null && obj2 === null) || (obj1 === undefined && obj2 === undefined)) {
    return true;
  }
  if ((obj1 === undefined && obj2 !== undefined) || (obj1 !== undefined && obj2 === undefined) || (obj1 === null && obj2 !== null) || (obj1 !== null && obj2 === null)) {
    return false;
  }
  if (obj1.constructor !== obj2.constructor) {
    return false;
  }
  if (typeof obj1 === 'function') {
    if (obj1.toString() !== obj2.toString()) {
      return false;
    }
  }
  if ([String, Number, Boolean].includes(obj1.constructor)) {
    return obj1 === obj2;
  }
  if (obj1.constructor === Array) {
    if (obj1.length !== obj2.length) {
      return false;
    }
    for (let i = 0; i < obj1.length; i++) {
      if (!equal(obj1[i], obj2[i])) {
        return false;
      }
    }
    return true;
  }
  return checkProperties(obj1, obj2);
};

const selectorRegex = /^([a-z][a-z0-9:_=-]*)?(#[a-z0-9:_=-]+)?(\.[^ ]+)*$/i;
const [PATCH, INSERT, DELETE] = [-1, -2, -3];
let $onrenderCallbacks = [];

// Virtual DOM implementation with HyperScript syntax
class VNode {
  constructor(...args) {
    this.type = undefined;
    this.props = {};
    this.data = {};
    this.id = undefined;
    this.$html = undefined;
    this.$onrender = undefined;
    this.style = undefined;
    this.value = undefined;
    this.children = [];
    this.classList = [];
    this.eventListeners = {};
    if (args.length === 0) {
      throw new Error('[VNode] No arguments passed to VNode constructor.');
    }
    if (args.length === 1) {
      let vnode = args[0];
      if (typeof vnode === 'string') {
        // Assume empty element
        this.processSelector(vnode);
      } else if (typeof vnode === 'function' || (typeof vnode === 'object' && vnode !== null)) {
        // Text node
        if (vnode.type === '#text') {
          this.type = '#text';
          this.value = vnode.value;
        } else {
          this.from(this.processVNodeObject(vnode));
        }
      } else {
        throw new Error('[VNode] Invalid first argument passed to VNode constructor.');
      }
    } else if (args.length === 2) {
      let [selector, data] = args;
      if (typeof selector !== 'string') {
        throw new Error('[VNode] Invalid first argument passed to VNode constructor.');
      }
      this.processSelector(selector);
      if (typeof data === 'string') {
        // Assume single child text node
        this.children = [new VNode({ type: '#text', value: data })];
        return;
      }
      if (typeof data !== 'function' && (typeof data !== 'object' || data === null)) {
        throw new Error('[VNode] The second argument of a VNode constructor must be an object, an array or a string.');
      }
      if (Array.isArray(data)) {
        // Assume 2nd argument as children
        this.processChildren(data);
      } else {
        if (data instanceof Function || data instanceof VNode) {
          this.processChildren(data);
        } else {
          // Not a VNode, assume props object
          this.processProperties(data);
        }
      }
    } else {
      let [selector, props, children] = args;
      if (args.length > 3) {
        children = args.slice(2);
      }
      children = Array.isArray(children) ? children : [children];
      if (typeof selector !== 'string') {
        throw new Error('[VNode] Invalid first argument passed to VNode constructor.');
      }
      this.processSelector(selector);
      if (props instanceof Function || props instanceof VNode || typeof props === 'string') {
        // 2nd argument is a child
        children = [props].concat(children);
      } else {
        if (typeof props !== 'object' || props === null) {
          throw new Error('[VNode] Invalid second argument passed to VNode constructor.');
        }
        this.processProperties(props);
      }
      this.processChildren(children);
    }
  }

  from(data) {
    this.value = data.value;
    this.type = data.type;
    this.id = data.id;
    this.$html = data.$html;
    this.$onrender = data.$onrender;
    this.style = data.style;
    this.data = data.data;
    this.value = data.value;
    this.eventListeners = data.eventListeners;
    this.children = data.children;
    this.props = data.props;
    this.classList = data.classList;
  }

  equal(a, b) {
    return equal(a, b === undefined ? this : b);
  }

  processProperties(attrs) {
    this.id = this.id || attrs.id;
    this.$html = attrs.$html;
    this.$onrender = attrs.$onrender;
    this.style = attrs.style;
    this.value = attrs.value;
    this.data = attrs.data || {};
    this.classList = attrs.classList && attrs.classList.length > 0 ? attrs.classList : this.classList;
    this.props = attrs;
    Object.keys(attrs)
      .filter((a) => a.startsWith('on') && attrs[a])
      .forEach((key) => {
        if (typeof attrs[key] !== 'function') {
          throw new Error(`[VNode] Event handler specified for ${key} event is not a function.`);
        }
        this.eventListeners[key.slice(2)] = attrs[key];
        delete this.props[key];
      });
    delete this.props.value;
    delete this.props.$html;
    delete this.props.$onrender;
    delete this.props.id;
    delete this.props.data;
    delete this.props.style;
    delete this.props.classList;
  }

  processSelector(selector) {
    if (!selector.match(selectorRegex) || selector.length === 0) {
      throw new Error(`[VNode] Invalid selector: ${selector}`);
    }
    const [, type, id, classes] = selector.match(selectorRegex);
    this.type = type;
    if (id) {
      this.id = id.slice(1);
    }
    this.classList = (classes && classes.split('.').slice(1)) || [];
  }

  processVNodeObject(arg) {
    if (arg instanceof VNode) {
      return arg;
    }
    if (arg instanceof Function) {
      let vnode = arg();
      if (typeof vnode === 'string') {
        vnode = new VNode({ type: '#text', value: vnode });
      }
      if (!(vnode instanceof VNode)) {
        throw new Error('[VNode] Function argument does not return a VNode');
      }
      return vnode;
    }
    throw new Error('[VNode] Invalid first argument provided to VNode constructor.');
  }

  processChildren(arg) {
    const children = Array.isArray(arg) ? arg : [arg];
    this.children = children
      .map((c) => {
        if (typeof c === 'string') {
          return new VNode({ type: '#text', value: c });
        }
        if (typeof c === 'function' || (typeof c === 'object' && c !== null)) {
          return this.processVNodeObject(c);
        }
        if (c) {
          throw new Error(`[VNode] Specified child is not a VNode: ${c}`);
        }
      })
      .filter((c) => c);
  }

  // Renders the actual DOM Node corresponding to the current Virtual Node
  render() {
    if (this.type === '#text') {
      return document.createTextNode(this.value);
    }
    const node = document.createElement(this.type);
    if (this.id) {
      node.id = this.id;
    }
    Object.keys(this.props).forEach((p) => {
      // Set attributes
      if (typeof this.props[p] === 'boolean') {
        this.props[p] ? node.setAttribute(p, '') : node.removeAttribute(p);
      }
      if (['string', 'number'].includes(typeof this.props[p])) {
        node.setAttribute(p, this.props[p]);
      }
      // Set properties
      node[p] = this.props[p];
    });
    // Event Listeners
    Object.keys(this.eventListeners).forEach((event) => {
      node.addEventListener(event, this.eventListeners[event]);
    });
    // Value
    if (this.value) {
      if (['textarea', 'input'].includes(this.type)) {
        node.value = this.value;
      } else {
        node.setAttribute('value', this.value);
      }
    }
    // Style
    if (this.style) {
      node.style.cssText = this.style;
    }
    // Classes
    this.classList.forEach((c) => {
      node.classList.add(c);
    });
    // Data
    Object.keys(this.data).forEach((key) => {
      node.dataset[key] = this.data[key];
    });
    // Children
    this.children.forEach((c) => {
      const cnode = c.render();
      node.appendChild(cnode);
      c.$onrender && $onrenderCallbacks.push(() => c.$onrender(cnode));
    });
    if (this.$html) {
      node.innerHTML = this.$html;
    }
    return node;
  }

  // Updates the current Virtual Node with a new Virtual Node (and syncs the existing DOM Node)
  redraw(data) {
    let { node, vnode } = data;
    const newvnode = vnode;
    const oldvnode = this;
    if (
      oldvnode.constructor !== newvnode.constructor ||
      oldvnode.type !== newvnode.type ||
      (oldvnode.type === newvnode.type && oldvnode.type === '#text' && oldvnode !== newvnode)
    ) {
      const renderedNode = newvnode.render();
      node.parentNode.replaceChild(renderedNode, node);
      newvnode.$onrender && newvnode.$onrender(renderedNode);
      oldvnode.from(newvnode);
      return;
    }
    // ID
    if (oldvnode.id !== newvnode.id) {
      node.id = newvnode.id || '';
      oldvnode.id = newvnode.id;
    }
    // Value
    if (oldvnode.value !== newvnode.value) {
      oldvnode.value = newvnode.value;
      if (['textarea', 'input'].includes(oldvnode.type)) {
        node.value = newvnode.value || '';
      } else {
        node.setAttribute('value', newvnode.value || '');
      }
    }
    // Classes
    if (!equal(oldvnode.classList, newvnode.classList)) {
      oldvnode.classList.forEach((c) => {
        if (!newvnode.classList.includes(c)) {
          node.classList.remove(c);
        }
      });
      newvnode.classList.forEach((c) => {
        if (!oldvnode.classList.includes(c)) {
          node.classList.add(c);
        }
      });
      oldvnode.classList = newvnode.classList;
    }
    // Style
    if (oldvnode.style !== newvnode.style) {
      node.style.cssText = newvnode.style || '';
      oldvnode.style = newvnode.style;
    }
    // Data
    if (!equal(oldvnode.data, newvnode.data)) {
      Object.keys(oldvnode.data).forEach((a) => {
        if (!newvnode.data[a]) {
          delete node.dataset[a];
        } else if (newvnode.data[a] !== oldvnode.data[a]) {
          node.dataset[a] = newvnode.data[a];
        }
      });
      Object.keys(newvnode.data).forEach((a) => {
        if (!oldvnode.data[a]) {
          node.dataset[a] = newvnode.data[a];
        }
      });
      oldvnode.data = newvnode.data;
    }
    // Properties & Attributes
    if (!equal(oldvnode.props, newvnode.props)) {
      Object.keys(oldvnode.props).forEach((a) => {
        node[a] = newvnode.props[a];
        if (typeof newvnode.props[a] === 'boolean') {
          oldvnode.props[a] = newvnode.props[a];
          newvnode.props[a] ? node.setAttribute(a, '') : node.removeAttribute(a);
        } else if ([null, undefined].includes(newvnode.props[a])) {
          delete oldvnode.props[a];
          node.removeAttribute(a);
        } else if (newvnode.props[a] !== oldvnode.props[a]) {
          oldvnode.props[a] = newvnode.props[a];
          if (['string', 'number'].includes(typeof newvnode.props[a])) {
            node.setAttribute(a, newvnode.props[a]);
          }
        }
      });
      Object.keys(newvnode.props).forEach((a) => {
        if (!oldvnode.props[a] && newvnode.props[a]) {
          oldvnode.props[a] = newvnode.props[a];
          if (['string', 'number'].includes(typeof newvnode.props[a])) {
            node.setAttribute(a, newvnode.props[a]);
          }
        }
      });
    }
    // Event listeners
    if (!equal(oldvnode.eventListeners, newvnode.eventListeners)) {
      Object.keys(oldvnode.eventListeners).forEach((a) => {
        if (!newvnode.eventListeners[a]) {
          node.removeEventListener(a, oldvnode.eventListeners[a]);
        } else if (!equal(newvnode.eventListeners[a], oldvnode.eventListeners[a])) {
          node.removeEventListener(a, oldvnode.eventListeners[a]);
          node.addEventListener(a, newvnode.eventListeners[a]);
        }
      });
      Object.keys(newvnode.eventListeners).forEach((a) => {
        if (!oldvnode.eventListeners[a]) {
          node.addEventListener(a, newvnode.eventListeners[a]);
        }
      });
      oldvnode.eventListeners = newvnode.eventListeners;
    }
    // Children
    let childMap = mapChildren(oldvnode, newvnode);
    let resultMap = [...Array(newvnode.children.length).keys()];
    while (!equal(childMap, resultMap)) {
      let count = -1;
      checkmap: for (const i of childMap) {
        count++;
        if (i === count) {
          // Matching nodes;
          continue;
        }
        switch (i) {
          case PATCH: {
            oldvnode.children[count].redraw({
              node: node.childNodes[count],
              vnode: newvnode.children[count],
            });
            break checkmap;
          }
          case INSERT: {
            oldvnode.children.splice(count, 0, newvnode.children[count]);
            const renderedNode = newvnode.children[count].render();
            node.insertBefore(renderedNode, node.childNodes[count]);
            newvnode.children[count].$onrender && newvnode.children[count].$onrender(renderedNode);
            break checkmap;
          }
          case DELETE: {
            oldvnode.children.splice(count, 1);
            node.removeChild(node.childNodes[count]);
            break checkmap;
          }
          default: {
            const vtarget = oldvnode.children.splice(i, 1)[0];
            oldvnode.children.splice(count, 0, vtarget);
            const target = node.removeChild(node.childNodes[i]);
            node.insertBefore(target, node.childNodes[count]);
            break checkmap;
          }
        }
      }
      childMap = mapChildren(oldvnode, newvnode);
      resultMap = [...Array(newvnode.children.length).keys()];
    }
    // $onrender
    if (!equal(oldvnode.$onrender, newvnode.$onrender)) {
      oldvnode.$onrender = newvnode.$onrender;
    }
    // innerHTML
    if (oldvnode.$html !== newvnode.$html) {
      node.innerHTML = newvnode.$html;
      oldvnode.$html = newvnode.$html;
      oldvnode.$onrender && oldvnode.$onrender(node);
    }
  }
}

const mapChildren = (oldvnode, newvnode) => {
  const newList = newvnode.children;
  const oldList = oldvnode.children;
  let map = [];
  for (let nIdx = 0; nIdx < newList.length; nIdx++) {
    let op = PATCH;
    for (let oIdx = 0; oIdx < oldList.length; oIdx++) {
      if (equal(newList[nIdx], oldList[oIdx]) && !map.includes(oIdx)) {
        op = oIdx; // Same node found
        break;
      }
    }
    if (op < 0 && newList.length >= oldList.length && map.length >= oldList.length) {
      op = INSERT;
    }
    map.push(op);
  }
  const oldNodesFound = map.filter((c) => c >= 0);
  if (oldList.length > newList.length) {
    // Remove remaining nodes
    [...Array(oldList.length - newList.length).keys()].forEach(() => map.push(DELETE));
  } else if (oldNodesFound.length === oldList.length) {
    // All nodes not found are insertions
    map = map.map((c) => (c < 0 ? INSERT : c));
  }
  return map;
};

/**
 * The code of the following class is heavily based on Storeon
 * Modified according to the terms of the MIT License
 * <https://github.com/storeon/storeon/blob/master/LICENSE>
 * Copyright 2019 Andrey Sitnik <andrey@sitnik.ru>
 */
class Store {
  constructor() {
    this.events = {};
    this.state = {};
  }
  dispatch(event, data) {
    if (event !== '$log') this.dispatch('$log', { event, data });
    if (this.events[event]) {
      let changes = {};
      let changed;
      this.events[event].forEach((i) => {
        this.state = { ...this.state, ...i(this.state, data) };
      });
    }
  }

  on(event, cb) {
    (this.events[event] || (this.events[event] = [])).push(cb);

    return () => {
      this.events[event] = this.events[event].filter((i) => i !== cb);
    };
  }
}

class Route {
  constructor({ path, def, query, parts }) {
    this.path = path;
    this.def = def;
    this.query = query;
    this.parts = parts;
    this.params = {};
    if (this.query) {
      const rawParams = this.query.split('&');
      rawParams.forEach((p) => {
        const [name, value] = p.split('=');
        this.params[decodeURIComponent(name)] = decodeURIComponent(value);
      });
    }
  }
}

class Router {
  constructor({ element, routes, store, location }) {
    this.element = element;
    this.redraw = null;
    this.store = store;
    this.location = location || window.location;
    if (!routes || Object.keys(routes).length === 0) {
      throw new Error('[Router] No routes defined.');
    }
    const defs = Object.keys(routes);
    this.routes = routes;
  }

  setRedraw(vnode, state) {
    this.redraw = () => {
      vnode.redraw({
        node: this.element.childNodes[0],
        vnode: this.routes[this.route.def](state),
      });
      this.store.dispatch('$redraw');
    };
  }

  async start() {
    const processPath = async (data) => {
      const oldRoute = this.route;
      const fragment = (data && data.newURL && data.newURL.match(/(#.+)$/) && data.newURL.match(/(#.+)$/)[1]) || this.location.hash;
      const path = fragment.replace(/\?.+$/, '').slice(1);
      const rawQuery = fragment.match(/\?(.+)$/);
      const query = rawQuery && rawQuery[1] ? rawQuery[1] : '';
      const pathParts = path.split('/').slice(1);

      let parts = {};
      for (let def of Object.keys(this.routes)) {
        let routeParts = def.split('/').slice(1);
        let match = true;
        let index = 0;
        parts = {};
        while (match && routeParts[index]) {
          const rP = routeParts[index];
          const pP = pathParts[index];
          if (rP.startsWith(':') && pP) {
            parts[rP.slice(1)] = pP;
          } else {
            match = rP === pP;
          }
          index++;
        }
        if (match) {
          this.route = new Route({ query, path, def, parts });
          break;
        }
      }
      if (!this.route) {
        throw new Error(`[Router] No route matches '${fragment}'`);
      }
      // Old route component teardown
      let state = {};
      if (oldRoute) {
        const oldRouteComponent = this.routes[oldRoute.def];
        state = (oldRouteComponent.teardown && (await oldRouteComponent.teardown(oldRouteComponent.state))) || state;
      }
      // New route component setup
      const newRouteComponent = this.routes[this.route.def];
      newRouteComponent.state = state;
      newRouteComponent.setup && (await newRouteComponent.setup(newRouteComponent.state));
      // Redrawing...
      redrawing = true;
      this.store.dispatch('$navigation', this.route);
      while (this.element.firstChild) {
        this.element.removeChild(this.element.firstChild);
      }
      const vnode = newRouteComponent(newRouteComponent.state);
      const node = vnode.render();
      this.element.appendChild(node);
      this.setRedraw(vnode, newRouteComponent.state);
      redrawing = false;
      vnode.$onrender && vnode.$onrender(node);
      $onrenderCallbacks.forEach((cbk) => cbk());
      $onrenderCallbacks = [];
      window.scrollTo(0, 0);
      this.store.dispatch('$redraw');
    };
    window.addEventListener('hashchange', processPath);
    await processPath();
  }

  navigateTo(path, params) {
    let query = Object.keys(params || {})
      .map((p) => `${encodeURIComponent(p)}=${encodeURIComponent(params[p])}`)
      .join('&');
    query = query ? `?${query}` : '';
    this.location.hash = `#${path}${query}`;
  }
}

// High Level API

export const h = (...args) => {
  return new VNode(...args);
};

export const h3 = {};

let store = null;
let router = null;
let redrawing = false;

h3.init = (config) => {
  let { element, routes, modules, preStart, postStart, location } = config;
  if (!routes) {
    // Assume config is a component object, define default route
    if (typeof config !== 'function') {
      throw new Error('[h3.init] The specified argument is not a valid configuration object or component function');
    }
    routes = { '/': config };
  }
  element = element || document.body;
  if (!(element && element instanceof Element)) {
    throw new Error('[h3.init] Invalid element specified.');
  }
  // Initialize store
  store = new Store();
  (modules || []).forEach((i) => {
    i(store);
  });
  store.dispatch('$init');
  // Initialize router
  router = new Router({ element, routes, store, location });
  return Promise.resolve(preStart && preStart())
    .then(() => router.start())
    .then(() => postStart && postStart());
};

h3.navigateTo = (path, params) => {
  if (!router) {
    throw new Error('[h3.navigateTo] No application initialized, unable to navigate.');
  }
  return router.navigateTo(path, params);
};

Object.defineProperty(h3, 'route', {
  get: () => {
    if (!router) {
      throw new Error('[h3.route] No application initialized, unable to retrieve current route.');
    }
    return router.route;
  },
});

Object.defineProperty(h3, 'state', {
  get: () => {
    if (!store) {
      throw new Error('[h3.state] No application initialized, unable to retrieve current state.');
    }
    return store.state;
  },
});

h3.on = (event, cb) => {
  if (!store) {
    throw new Error('[h3.on] No application initialized, unable to listen to events.');
  }
  return store.on(event, cb);
};

h3.dispatch = (event, data) => {
  if (!store) {
    throw new Error('[h3.dispatch] No application initialized, unable to dispatch events.');
  }
  return store.dispatch(event, data);
};

h3.redraw = (setRedrawing) => {
  if (!router || !router.redraw) {
    throw new Error('[h3.redraw] No application initialized, unable to redraw.');
  }
  if (redrawing) {
    return;
  }
  redrawing = true;
  router.redraw();
  redrawing = setRedrawing || false;
};

h3.screen = ({ setup, display, teardown }) => {
  if (!display || typeof display !== 'function') {
    throw new Error('[h3.screen] No display property specified.');
  }
  if (setup && typeof setup !== 'function') {
    throw new Error('[h3.screen] setup property is not a function.');
  }
  if (teardown && typeof teardown !== 'function') {
    throw new Error('[h3.screen] teardown property is not a function.');
  }
  const fn = display;
  if (setup) {
    fn.setup = setup;
  }
  if (teardown) {
    fn.teardown = teardown;
  }
  return fn;
};

export default h3;