import {getFormNavigationController} from "./form-navigation";
import type {ReactiveController, ReactiveControllerHost} from "lit";
import type {ZincFormControl} from "./zinc-element";
import type Button from "../components/button";

//
// We store a WeakMap of forms + controls so we can keep references to all Zinc controls within a given form. As
// elements connect and disconnect to/from the DOM, their containing form is used as the key and the form control is
// added and removed from the form's set, respectively.
//
export const formCollections: WeakMap<HTMLFormElement, Set<ZincFormControl>> = new WeakMap();

//
// We store a WeakMap of reportValidity() overloads so we can override it when form controls connect to the DOM and
// restore the original behavior when they disconnect.
//
const reportValidityOverloads: WeakMap<HTMLFormElement, () => boolean> = new WeakMap();
const checkValidityOverloads: WeakMap<HTMLFormElement, () => boolean> = new WeakMap();

//
// We store a Set of controls that users have interacted with. This allows us to determine the interaction state
// without littering the DOM with additional data attributes.
//
const userInteractedControls: WeakSet<ZincFormControl> = new WeakSet();

//
// We store a WeakMap of interactions for each form control so we can track when all conditions are met for validation.
//
const interactions = new WeakMap<ZincFormControl, string[]>();

export interface FormControlControllerOptions {
  /** A function that returns the form containing the form control. */
  form: (input: ZincFormControl) => HTMLFormElement | null;
  /** A function that returns the form control's name, which will be submitted with the form data. */
  name: (input: ZincFormControl) => string;
  /** A function that returns the form control's current value. */
  value: (input: ZincFormControl) => unknown | unknown[];
  /** A function that returns the form control's default value. */
  defaultValue: (input: ZincFormControl) => unknown | unknown[];
  /** A function that returns the form control's current disabled state. If disabled, the value won't be submitted. */
  disabled: (input: ZincFormControl) => boolean;
  /**
   * A function that maps to the form control's reportValidity() function. When the control is invalid, this will
   * prevent submission and trigger the browser's constraint violation warning.
   */
  reportValidity: (input: ZincFormControl) => boolean;

  /**
   * A function that maps to the form control's `checkValidity()` function. When the control is invalid, this will return false.
   *   this is helpful is you want to check validation without triggering the native browser constraint violation warning.
   */
  checkValidity: (input: ZincFormControl) => boolean;
  /** A function that sets the form control's value */
  setValue: (input: ZincFormControl, value: unknown) => void;
  /**
   * An array of event names to listen to. When all events in the list are emitted, the control will receive validity
   * states such as user-valid and user-invalid.user interacted validity states. */
  assumeInteractionOn: string[];
}

export class FormControlController implements ReactiveController {
  host: ZincFormControl & ReactiveControllerHost;
  form?: HTMLFormElement | null;
  options: FormControlControllerOptions;

  constructor(host: ReactiveControllerHost & ZincFormControl, options?: Partial<FormControlControllerOptions>) {
    (this.host = host).addController(this);
    this.options = {
      form: input => {
        // If there's a form attribute, use it to find the target form by id
        // Controls may not always reflect the 'form' property. For example, `<zn-button>` doesn't reflect.
        const formId = input.form;

        if (formId) {
          const root = input.getRootNode() as Document | ShadowRoot | HTMLElement;
          const form = root.querySelector(`#${formId}`);

          if (form) {
            return form as HTMLFormElement;
          }
        }

        return input.closest('form');
      },
      name: input => input.name,
      value: input => input.value,
      defaultValue: input => input.defaultValue,
      disabled: input => input.disabled ?? false,
      reportValidity: input => (typeof input.reportValidity === 'function' ? input.reportValidity() : true),
      checkValidity: input => (typeof input.checkValidity === 'function' ? input.checkValidity() : true),
      setValue: (input, value: string) => (input.value = value),
      assumeInteractionOn: ['zn-input'],
      ...options
    };
  }

  async hostConnected() {
    const form = this.options.form(this.host);

    if (form) {
      this.attachForm(form);
    }

    // Listen for interactions
    interactions.set(this.host, []);
    this.options.assumeInteractionOn.forEach(event => {
      this.host.addEventListener(event, this.handleInteraction);
    });

    await this.host.updateComplete;
    if (form) {
      this.checkFormValidity();
    }
  }

  hostDisconnected() {
    this.detachForm();

    // Clean up interactions
    interactions.delete(this.host);
    this.options.assumeInteractionOn.forEach(event => {
      this.host.removeEventListener(event, this.handleInteraction);
    });
  }

  hostUpdated() {
    const form = this.options.form(this.host);

    // Detach if the form no longer exists
    if (!form) {
      this.detachForm();
    }

    // If the form has changed, reattach it
    if (form && this.form !== form) {
      this.detachForm();
      this.attachForm(form);
    }

    if (this.host.hasUpdated) {
      this.setValidity(this.host.validity?.valid);
    }
  }

  private attachForm(form?: HTMLFormElement) {
    if (!form) {
      this.form = undefined;
      return;
    }

    this.form = form;

    // Add this element to the form's collection
    if (formCollections.has(this.form)) {
      formCollections.get(this.form)!.add(this.host);
    } else {
      formCollections.set(this.form, new Set<ZincFormControl>([this.host]));
    }

    // Initialize form navigation controller if the form has the data-enter-navigation attribute
    if (this.form.hasAttribute('data-enter-navigation')) {
      getFormNavigationController(this.form);
    }

    this.form.addEventListener('formdata', this.handleFormData);
    this.form.addEventListener('submit', this.handleFormSubmit);
    this.form.addEventListener('reset', this.handleFormReset);

    // Pagelet events to check form completion state
    this.form.addEventListener('complete', this.enableSubmit);
    this.form.addEventListener('cancelled', this.enableSubmit);
    this.form.addEventListener('error', this.enableSubmit);

    // Overload the form's reportValidity() method so it looks at Zinc form controls
    if (!reportValidityOverloads.has(this.form)) {
      reportValidityOverloads.set(this.form, this.form.reportValidity);
      this.form.reportValidity = () => this.reportFormValidity();
    }

    // Overload the form's checkValidity() method so it looks at Zinc form controls
    if (!checkValidityOverloads.has(this.form)) {
      checkValidityOverloads.set(this.form, this.form.checkValidity);
      this.form.checkValidity = () => this.checkFormValidity();
    }
  }

  private detachForm() {
    if (!this.form) return;

    const formCollection = formCollections.get(this.form);

    if (!formCollection) {
      return;
    }

    // Remove this host from the form's collection
    formCollection.delete(this.host);

    // Check to make sure there's no other form controls in the collection. If we do this
    // without checking if any other controls are still in the collection, then we will wipe out the
    // validity checks for all other elements.
    if (formCollection.size <= 0) {
      this.form.removeEventListener('formdata', this.handleFormData);
      this.form.removeEventListener('submit', this.handleFormSubmit);
      this.form.removeEventListener('reset', this.handleFormReset);

      this.form.removeEventListener('complete', this.enableSubmit);
      this.form.removeEventListener('cancelled', this.enableSubmit);
      this.form.removeEventListener('error', this.enableSubmit);

      if (reportValidityOverloads.has(this.form)) {
        this.form.reportValidity = reportValidityOverloads.get(this.form)!;
        reportValidityOverloads.delete(this.form);
      }

      if (checkValidityOverloads.has(this.form)) {
        this.form.checkValidity = checkValidityOverloads.get(this.form)!;
        checkValidityOverloads.delete(this.form);
      }

      // So it looks weird here to not always set the form to undefined. But I _think_ if we un-attach this.form here,
      // we end up in this fun spot where future validity checks don't have a reference to the form validity handler.
      // First form element in sets the validity handler. So we can't clean up `this.form` until there are no other form elements in the form.
      this.form = undefined;
    }
  }

  private handleFormData = (event: FormDataEvent) => {
    const disabled = this.options.disabled(this.host);
    const name = this.options.name(this.host);
    const value = this.options.value(this.host);

    // For buttons, we only submit the value if they were the submitter. This is currently done in doAction() by
    // injecting the name/value on a temporary button, so we can just skip them here.
    const isButton = this.host.tagName.toLowerCase() === 'zn-button';

    if (
      this.host.isConnected &&
      !disabled &&
      !isButton &&
      name.length > 0 &&
      typeof value !== 'undefined'
    ) {
      const appendPrimitive = (val: string | number | boolean) => {
        event.formData.append(name, val.toString());
      };
      const appendFile = (file: Blob, filename?: string) => {
        // If a filename is provided or it's a File (has name), FormData will use it properly
        const maybeFile = file as unknown as File;
        const fname = filename ?? (typeof maybeFile.name === 'string' ? maybeFile.name : undefined);
        // Overloads: append(name, blob, filename?)
        if (typeof fname === 'string') {
          event.formData.append(name, file, fname);
        } else {
          event.formData.append(name, file);
        }
      };

      const isFileList = (val: unknown): val is FileList => typeof FileList !== 'undefined' && val instanceof FileList;
      const isBlob = (val: unknown): val is Blob => typeof Blob !== 'undefined' && val instanceof Blob;

      if (isFileList(value)) {
        // Match native input[type=file] behavior: append each File; if empty, append nothing
        if (value.length > 0) {
          for (let i = 0; i < value.length; i++) {
            const f = value.item(i);
            if (f) appendFile(f, f.name);
          }
        }
      } else if (isBlob(value)) {
        appendFile(value, (value as unknown as File).name);
      } else if (Array.isArray(value)) {
        (value as unknown[]).forEach(val => {
          if (isBlob(val)) {
            appendFile(val as Blob, (val as unknown as File).name);
          } else if (isFileList(val)) {
            const fl = val as FileList;
            for (let i = 0; i < fl.length; i++) {
              const f = fl.item(i);
              if (f) appendFile(f, f.name);
            }
          } else {
            appendPrimitive(val as string | number | boolean);
          }
        });
      } else {
        appendPrimitive(value as string | number | boolean);
      }

      this.host.dispatchEvent(new CustomEvent('zn-formdata', {bubbles: true, composed: true}));
    }
  };

  private handleFormSubmit = (event: Event) => {
    const disabled = this.options.disabled(this.host);
    const reportValidity = this.options.reportValidity;

    // Update the interacted state for all controls when the form is submitted
    if (this.form && !this.form.noValidate) {
      formCollections.get(this.form)?.forEach(control => {
        this.setUserInteracted(control, true);
      });
    }

    // get the submit button
    const submitButton = this.form?.querySelector('[type="submit"]') as HTMLButtonElement | null;
    const content = submitButton?.innerHTML ?? 'Submit';
    if (submitButton) {
      submitButton.setAttribute('data-original-text', content);

      setTimeout(() => {
        // disable duplicate submit
        submitButton.disabled = true;
        submitButton.innerHTML = !this.form?.hasAttribute('data-no-loading-text')
          ? this.form?.getAttribute('data-loading-text') || 'Processing...'
          : content;
      }, 20);

      setTimeout(() => {
        submitButton.disabled = false;
        submitButton.innerHTML = content;
      }, 15000);
    }

    if (this.form && !this.form.noValidate && !disabled && !reportValidity(this.host)) {
      event.preventDefault();
      event.stopImmediatePropagation();

      // remove the disabled state from the submit button
      if (submitButton) {
        submitButton.disabled = false;
        submitButton.innerHTML = content;
      }
    }
  };

  private enableSubmit = (e: Event) => {
    const target = e.target;

    // Make sure the event is coming from the attached form
    if (target !== this.form) {
      return;
    }

    const submitButton = this.form?.querySelector('[type="submit"]') as HTMLButtonElement | null;
    if (submitButton) {
      const content = submitButton.getAttribute('data-original-text') ?? submitButton.innerHTML;

      submitButton.disabled = false;
      submitButton.innerHTML = content;
    }
  }

  private handleFormReset = () => {
    this.options.setValue(this.host, this.options.defaultValue(this.host));
    this.setUserInteracted(this.host, false);
    interactions.set(this.host, []);
  };

  private handleInteraction = (event: Event) => {
    const emittedEvents = interactions.get(this.host)!;

    if (!emittedEvents.includes(event.type)) {
      emittedEvents.push(event.type);
    }

    // Mark it as user-interacted as soon as all associated events have been emitted
    if (emittedEvents.length === this.options.assumeInteractionOn.length) {
      this.setUserInteracted(this.host, true);
    }
    this.checkFormValidity();
  };

  private checkFormValidity = () => {
    //
    // This is very similar to the `reportFormValidity` function, but it does not trigger native constraint validation
    // Allow the user to simply check if the form is valid and handling validity in their own way.
    //
    // We preserve the original method in a WeakMap, but we don't call it from the overload because that would trigger
    // validations in an unexpected order. When the element disconnects, we revert to the original behavior. This won't
    // be necessary once we can use ElementInternals.
    //
    // Note that we're also honoring the form's novalidate attribute.
    //
    const submit = this.form?.querySelector('[type="submit"]') as HTMLButtonElement | null;
    if (this.form && !this.form.noValidate) {
      // This seems sloppy, but checking all elements will cover native inputs, Zinc inputs, and other custom
      // elements that support the constraint validation API.
      const elements: NodeListOf<HTMLInputElement> = this.form.querySelectorAll<HTMLInputElement>('*');
      for (const element of elements) {
        if (typeof element.checkValidity === 'function' && !element.checkValidity()) {
          submit?.setAttribute('disabled', 'disabled');
          return false;
        }
      }
    }

    submit?.removeAttribute('disabled');
    return true;
  };

  private reportFormValidity = () => {
    //
    // Zinc form controls work hard to act like regular form controls. They support the Constraint Validation API
    // and its associated methods such as setCustomValidity() and reportValidity(). However, the HTMLFormElement also
    // has a reportValidity() method that will trigger validation on all child controls. Since we're not yet using
    // ElementInternals, we need to overload this method so it looks for any element with the reportValidity() method.
    //
    // We preserve the original method in a WeakMap, but we don't call it from the overload because that would trigger
    // validations in an unexpected order. When the element disconnects, we revert to the original behavior. This won't
    // be necessary once we can use ElementInternals.
    //
    // Note that we're also honoring the form's novalidate attribute.
    //
    if (this.form && !this.form.noValidate) {
      // This seems sloppy, but checking all elements will cover native inputs, Zinc inputs, and other custom
      // elements that support the constraint validation API.
      const elements: NodeListOf<HTMLInputElement> = this.form.querySelectorAll<HTMLInputElement>('*');
      for (const element of elements) {
        if (typeof element.reportValidity === 'function' && !element.reportValidity()) {
          return false;
        }
      }
    }

    return true;
  };

  private setUserInteracted(el: ZincFormControl, hasInteracted: boolean) {
    if (hasInteracted) {
      userInteractedControls.add(el);
    } else {
      userInteractedControls.delete(el);
    }

    el.requestUpdate();
  }

  private doAction(type: 'submit' | 'reset', submitter?: HTMLInputElement | Button) {
    if (this.form) {
      const button = document.createElement('button');
      button.type = type;
      button.style.position = 'absolute';
      button.style.width = '0';
      button.style.height = '0';
      button.style.clipPath = 'inset(50%)';
      button.style.overflow = 'hidden';
      button.style.whiteSpace = 'nowrap';

      // Pass name, value, and form attributes through to the temporary button
      if (submitter) {
        button.name = submitter.name;
        button.value = submitter.value;

        ['formaction', 'formenctype', 'formmethod', 'formnovalidate', 'formtarget'].forEach(attr => {
          if (submitter.hasAttribute(attr)) {
            button.setAttribute(attr, submitter.getAttribute(attr)!);
          }
        });
      }

      this.form.append(button);

      // make sure this form is 'zn-register-element' event with the form
      if (this.form instanceof HTMLFormElement) {
        document.dispatchEvent(new CustomEvent('zn-register-element', {
          detail: {element: this.form}
        }));
      }

      button.click();
      button.remove();
    }
  }

  /** Returns the associated `<form>` element, if one exists. */
  getForm() {
    return this.form ?? null;
  }

  /** Resets the form, restoring all the control to their default value */
  reset(submitter?: HTMLInputElement | Button) {
    this.doAction('reset', submitter);
  }

  /** Submits the form, triggering validation and form data injection. */
  submit(submitter?: HTMLInputElement | Button) {
    // Calling form.submit() bypasses the submit event and constraint validation. To prevent this, we can inject a
    // native submit button into the form, "click" it, then remove it to simulate a standard form submission.
    this.doAction('submit', submitter);
  }

  /**
   * Synchronously sets the form control's validity. Call this when you know the future validity but need to update
   * the host element immediately, i.e. before Lit updates the component in the next update.
   */
  setValidity(isValid: boolean) {
    const host = this.host;
    const hasInteracted = Boolean(userInteractedControls.has(host));
    const required = Boolean(host.required);

    // We're mapping the following "states" to data attributes. In the future, we can use ElementInternals.states to
    // create a similar mapping, but instead of [data-invalid] it will look like :--invalid.
    host.toggleAttribute('data-required', required);
    host.toggleAttribute('data-optional', !required);
    host.toggleAttribute('data-invalid', !isValid);
    host.toggleAttribute('data-valid', isValid);
    host.toggleAttribute('data-user-invalid', !isValid && hasInteracted);
    host.toggleAttribute('data-user-valid', isValid && hasInteracted);
  }

  /**
   * Updates the form control's validity based on the current value of `host.validity.valid`. Call this when anything
   * that affects constraint validation changes so the component receives the correct validity states.
   */
  updateValidity() {
    const host = this.host;
    this.setValidity(host.validity?.valid);
  }

  /**
   * Dispatches a non-bubbling, cancelable custom event of type `zn-invalid`.
   * If the `zm-invalid` event will be cancelled then the original `invalid`
   * event (which may have been passed as argument) will also be cancelled.
   * If no original `invalid` event has been passed then the `zn-invalid`
   * event will be cancelled before being dispatched.
   */
  emitInvalidEvent(originalInvalidEvent?: Event) {
    const znInvalidEvent = new CustomEvent<Record<PropertyKey, never>>('zn-invalid', {
      bubbles: false,
      composed: false,
      cancelable: true,
      detail: {}
    });

    if (!originalInvalidEvent) {
      znInvalidEvent.preventDefault();
    }

    if (!this.host.dispatchEvent(znInvalidEvent)) {
      originalInvalidEvent?.preventDefault();
    }
  }
}

/*
 * Predefined common validity states.
 * All of them are read-only.
 */

// A validity state object that represents `valid`
export const validValidityState: ValidityState = Object.freeze({
  badInput: false,
  customError: false,
  patternMismatch: false,
  rangeOverflow: false,
  rangeUnderflow: false,
  stepMismatch: false,
  tooLong: false,
  tooShort: false,
  typeMismatch: false,
  valid: true,
  valueMissing: false
});

// A validity state object that represents `value missing`
export const customErrorValidityState: ValidityState = Object.freeze({
  ...validValidityState,
  customError: true,
  valid: false
});

// A validity state object that represents a custom error
export const valueMissingValidityState: ValidityState = Object.freeze({
  ...validValidityState,
  valueMissing: true,
  valid: false
});