import { Loader } from 'aurelia-loader'
import { DOM } from 'aurelia-pal';
import { Origin } from 'aurelia-metadata'
import { ViewEngine, ViewCompileInstruction } from 'aurelia-templating';
import { Container } from 'aurelia-dependency-injection';
import { _createCSSResource, CSSResource } from './hmr-css-resource';
import { ResourceModuleCorrect, AU, AUController, ViewFactoryWithTemplate } from './_typings';
import { TraversalInfo, traverseController } from './view-model-traverse-controller';
import { getElementsToRerender } from './view-traverse-controller';
import { rerenderMatchingSlotChildren, rerenderController } from './render-utils';

const UndefinedResourceModule = { id: null, mainResource: { metadata: {}, value: undefined } } as ResourceModuleCorrect;

export function getAuElements() {
  return Array.from(DOM.querySelectorAll('.au-target')) as Array<Element & AU>;
}

export function getControllersWithClassInstances(oldPrototype: any) {
  // get visible elements to re-render:
  const auElements = getAuElements();

  /* NOTE: viewless components like blur-image do not have el.au.controller set */ 
  const controllersLists = auElements.map(el => el.au && Object.values(el.au) || []);

  // list of unique controllers
  const controllers = Array.from(
    new Set<AUController>(([] as Array<any>).concat(...controllersLists))
  );

  const previouslyTraversed = new Set<any>();
  const traversalInfo = ([] as Array<TraversalInfo>).concat(...controllers.map(parentController => 
    traverseController(oldPrototype, parentController, {
      previouslyTraversed,
      parentController
    })
  ));

  return traversalInfo;
}

export class HmrContext {
  viewEngine = Container.instance.get(ViewEngine) as ViewEngine & { moduleAnalyzer: any, container: Container };
  moduleAnalyzerCache: { [moduleId: string]: ResourceModuleCorrect } = this.viewEngine.moduleAnalyzer.cache;

  constructor (public loader: Loader & { moduleRegistry: Object, templateRegistry: Object }) {
    const styleResourcePlugin = {
      fetch: (moduleId: string) => {
        return {
          [moduleId]: _createCSSResource(moduleId)
        };
      },
      hot: (moduleId: string) => {
        this.reloadCss(moduleId);
      }
    };
    ['.css', '.less', '.sass', '.scss', '.styl'].forEach(ext => this.viewEngine.addResourcePlugin(ext, styleResourcePlugin));
  }

  /**
   * Handles ViewModel changes
   */
  async handleModuleChange(moduleId: string, hot: any) {
    // get old version of the module:
    const previousModule = (this.loader.moduleRegistry as any)[moduleId];
    if (!previousModule) {
      return;
    }

    console.log(`Running default HMR for ${moduleId}`);

    // reload fresh module:
    delete (this.loader.moduleRegistry as any)[moduleId];
    const newModule = await this.loader.loadModule(moduleId);

    const oldResourceModule = this.moduleAnalyzerCache[moduleId];
    let newResourceModule: ResourceModuleCorrect;
    if (oldResourceModule) {
      // almost the same as: ViewEngine.importViewModelResource(moduleId, moduleMember);
      const origin = Origin.get(newModule);
      const normalizedId = origin.moduleId;
      const moduleMember = origin.moduleMember;
      newResourceModule = this.viewEngine.moduleAnalyzer.analyze(normalizedId, newModule, moduleMember) as ResourceModuleCorrect;

      if (!newResourceModule.mainResource && !newResourceModule.resources) {
        hot.decline(moduleId);
        return;
      }

      if (newResourceModule.mainResource) {
        newResourceModule.initialize(this.viewEngine.container);
      }

      // monkey patch old resource module:
      // would be better to simply replace it everywhere
      Object.assign(oldResourceModule, newResourceModule);
    }

    // TODO: kinda CompositionEngine.ensureViewModel()
    // TODO: to replace - use closest container: childContainer.get(viewModelResource.value);

    if (previousModule instanceof Object) {
      // console.log(`Analysing ${moduleId} as a whole`);
      // getControllersWithClassInstances(previousModule, undefined);
      const keys = Object.keys(previousModule);
      keys.forEach(key => {
        const newExportValue = newModule[key];
        if (!newExportValue) {
          return;
        }

        const previousExportValue = previousModule[key];
        const type = typeof previousExportValue;
        if (type === 'function' || type === 'object') {
          // these are the only exports we can reliably replace (classes, objects and functions)

          console.log(`Analyzing ${moduleId}->${key}`);
          const traversalInfo = getControllersWithClassInstances(previousExportValue);
          // console.log(traversalInfo);
          
          traversalInfo.forEach(info => {
            if (info.propertyInParent === undefined) {
              return;
            }
            if (info.instance) {
              const entry = info.immediateParent[info.propertyInParent];
              const newPrototype = newExportValue.prototype;
              if (newPrototype) {
                Object.setPrototypeOf(entry, newPrototype);
              } else {
                console.warn(`No new prototype for ${moduleId}->${key}`);
              }
              if (info.relatedView && info.relatedView.isBound) {
                const {bindingContext, overrideContext} = info.relatedView;
                info.relatedView.unbind();
                info.relatedView.bind(bindingContext, overrideContext);
              }
              // if (info.parentController && info.parentController.isBound) {
              //   const scope = info.parentController.scope;
              //   info.parentController.unbind();
              //   info.parentController.bind(scope);
              // }
            } else {
              console.log(`Replacing`, info.immediateParent[info.propertyInParent], `with`, newExportValue);
              info.immediateParent[info.propertyInParent] = newExportValue;
            }
          });
        }
      });
    }
    // find all instances of the Classes
  }

  /**
   * Handles Hot Reloading when a View changes
   * 
   * TODO: make a queue of changes and handle after few ms multiple TOGETHER
   */
  async handleViewChange(moduleId: string) {
    const templateModuleId = this.loader.applyPluginToUrl(moduleId, 'template-registry-entry');

    console.log(`Handling HMR for ${moduleId}`)
    
    // get old entry:
    let entry = this.loader.getOrCreateTemplateRegistryEntry(moduleId);
    // delete it, and the module from caches:
    delete (this.loader.templateRegistry as any)[moduleId];
    delete (this.loader.moduleRegistry as any)[moduleId];
    delete (this.loader.moduleRegistry as any)[templateModuleId];

    // reload template (also done in loadViewFactory):
    // await this.loader.templatethis.loader.loadTemplate(loader, entry);

    const originalFactory = entry.factory as ViewFactoryWithTemplate; // htmlBehaviorResource.viewFactory
    
    // just to be safe, lets patch up the old ViewFactory
    if (!originalFactory) {
      console.error(`Something's gone wrong, no original ViewFactory?!`)
      return
    }

    const { mainResource, id: associatedModuleId } = this.getResourceModuleByTemplate(originalFactory.template);
    const { metadata: htmlBehaviorResource, value: targetClass } = mainResource;

    if (entry.factory !== htmlBehaviorResource.viewFactory) {
      console.info(`Different origin factories`, entry.factory, htmlBehaviorResource.viewFactory)
    }

    // TODO: find a way to find CSS removed from templates and unload it
    const compileInstruction = new ViewCompileInstruction(htmlBehaviorResource.targetShadowDOM, true);
    compileInstruction.associatedModuleId = associatedModuleId;
    const newViewFactory = (await this.viewEngine.loadViewFactory(moduleId, compileInstruction, null as any, targetClass)) as ViewFactoryWithTemplate;

    // TODO: keep track of hidden Views, e.g. 
    // using beforeBind or mutation-observers https://dev.opera.com/articles/mutation-observers-tutorial/

    // NOTES:
    // the document-fragment in the newViewFactory has different numbers for the same resources:
    // newViewFactory.instructions -- have different numbers than originalFactory
    // newViewFactory.resources.elements -- contains the resources of children but not the SELF HtmlBehaviorResource
    // monkey-patch the template just in case references to it are lying still around somewhere:
    originalFactory.template = newViewFactory.template;
    originalFactory.instructions = newViewFactory.instructions;
    originalFactory.resources = newViewFactory.resources;
    
    // TODO: it might be best to replace the instance of the ViewFactory in the HtmlBehaviorResource:
    // but THIS CAUSES LOOPING WITH NESTED ELEMENTS:
    // if (htmlBehaviorResource.viewFactory) {
    //   htmlBehaviorResource.viewFactory = newViewFactory;
    // }

    const elementsToReRender = getElementsToRerender(originalFactory.template);
    const factoryToRenderWith = newViewFactory;
    // const factoryToRenderWith = originalFactory;
    elementsToReRender.slots.forEach(slot => rerenderMatchingSlotChildren(slot, factoryToRenderWith, originalFactory.template));
    elementsToReRender.viewControllers.forEach(e => rerenderController(e, 'view', factoryToRenderWith));
    elementsToReRender.scopeControllers.forEach(e => rerenderController(e, 'scope', factoryToRenderWith));
  }

  /**
   * handles hot-reloading CSS modules
   */
  reloadCss(moduleId: string) {
    if (!(moduleId in this.loader.moduleRegistry)) {
      return; // first load
    }

    const extensionIndex = moduleId.lastIndexOf('.');
    const moduleExtension = moduleId.substring(extensionIndex + 1);
    const pluginName = `${moduleExtension}-resource-plugin`;
    const cssPluginModuleId = this.loader.applyPluginToUrl(moduleId, pluginName);

    console.log(`Handling HMR for ${moduleId}`);
    delete (this.loader.moduleRegistry as any)[moduleId];
    delete (this.loader.moduleRegistry as any)[cssPluginModuleId];

    const analyzedModule = this.moduleAnalyzerCache[cssPluginModuleId];
    if (typeof analyzedModule === 'undefined') {
      console.error(`Unable to find module, check the plugin exists and the module has been loaded with the expected plugin`);
      return;
    } else if (!analyzedModule.resources || !analyzedModule.resources.length) {
      console.error(`Something's wrong, no resources for this CSS file ${moduleId}`);
      return;
    }

    const mainResource = analyzedModule.resources[0];

    const cssResource = mainResource.metadata as CSSResource;
    if (cssResource._scoped && cssResource._scoped.injectedElements.length) {
      console.error(`Hot Reloading scopedCSS is not yet supported!`);
      return;
      // cssResource._scoped.injectedElements.forEach(el => el.remove());
    }

    if (cssResource.injectedElement) {
      cssResource.injectedElement.remove();
    }
    // reload resource
    cssResource.load(Container.instance);
  }

  getResourceModuleByTemplate(template: any) {
    // find the related ResourceModule (if any)
    const relatedResourceModule = Object.values(this.moduleAnalyzerCache).find(resourceModule => 
      resourceModule.mainResource && 
      resourceModule.mainResource.metadata &&
      resourceModule.mainResource.metadata.viewFactory &&
      resourceModule.mainResource.metadata.viewFactory.template === template
    )
    return relatedResourceModule || UndefinedResourceModule;
  }

  getResourceModuleById(moduleId: string) {
    return moduleId in this.moduleAnalyzerCache ? this.moduleAnalyzerCache[moduleId] : UndefinedResourceModule;
  }

  // these two helpers might be helpful in the future:
  /*
  getResourceModule(moduleId: string) {
    // find the related ResourceModule (if any)
    const relatedResourceModule = Object.values(this.moduleAnalyzerCache).find(resourceModule => {
      const dependencies = resourceModule.loadContext && resourceModule.loadContext.dependencies;
      return dependencies && Object.keys(dependencies).indexOf(moduleId) >= 0;
    }) as ResourceModule
    return relatedResourceModule || UndefinedResourceModule;
  }

  getResourceModuleByBehaviorResource(htmlBehaviorResource: any) {
    // find the related ResourceModule (if any)
    const relatedResourceModule = Object.values(this.moduleAnalyzerCache).find(resourceModule => 
      resourceModule.mainResource && resourceModule.mainResource.metadata === htmlBehaviorResource
    ) as ResourceModule
    return relatedResourceModule || UndefinedResourceModule;
  }
  */
}