/**
 * @license
 * Copyright 2011 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * Library to create tooltips for Blockly.
 * First, call createDom() after onload.
 * Second, set the 'tooltip' property on any SVG element that needs a tooltip.
 * If the tooltip is a string, or a function that returns a string, that message
 * will be displayed. If the tooltip is an SVG element, then that object's
 * tooltip will be used. Third, call bindMouseEvents(e) passing the SVG element.
 *
 * @namespace Blockly.Tooltip
 */
import * as goog from '../closure/goog/goog.js';
goog.declareModuleId('Blockly.Tooltip');

import * as browserEvents from './browser_events.js';
import * as common from './common.js';
import * as blocklyString from './utils/string.js';


/**
 * A type which can define a tooltip.
 * Either a string, an object containing a tooltip property, or a function which
 * returns either a string, or another arbitrarily nested function which
 * eventually unwinds to a string.
 *
 * @alias Blockly.Tooltip.TipInfo
 */
export type TipInfo =
    string|{tooltip: AnyDuringMigration}|(() => TipInfo|string|Function);

/**
 * A function that renders custom tooltip UI.
 * 1st parameter: the div element to render content into.
 * 2nd parameter: the element being moused over (i.e., the element for which the
 * tooltip should be shown).
 *
 * @alias Blockly.Tooltip.CustomTooltip
 */
export type CustomTooltip = (p1: Element, p2: Element) => AnyDuringMigration;

/**
 * An optional function that renders custom tooltips into the provided DIV. If
 * this is defined, the function will be called instead of rendering the default
 * tooltip UI.
 */
let customTooltip: CustomTooltip|undefined = undefined;

/**
 * Sets a custom function that will be called if present instead of the default
 * tooltip UI.
 *
 * @param customFn A custom tooltip used to render an alternate tooltip UI.
 * @alias Blockly.Tooltip.setCustomTooltip
 */
export function setCustomTooltip(customFn: CustomTooltip) {
  customTooltip = customFn;
}

/**
 * Gets the custom tooltip function.
 *
 * @returns The custom tooltip function, if defined.
 */
export function getCustomTooltip(): CustomTooltip|undefined {
  return customTooltip;
}

/** Is a tooltip currently showing? */
let visible = false;

/**
 * Returns whether or not a tooltip is showing
 *
 * @returns True if a tooltip is showing
 * @alias Blockly.Tooltip.isVisible
 */
export function isVisible(): boolean {
  return visible;
}

/** Is someone else blocking the tooltip from being shown? */
let blocked = false;

/**
 * Maximum width (in characters) of a tooltip.
 *
 * @alias Blockly.Tooltip.LIMIT
 */
export const LIMIT = 50;

/** PID of suspended thread to clear tooltip on mouse out. */
let mouseOutPid: AnyDuringMigration = 0;

/** PID of suspended thread to show the tooltip. */
let showPid: AnyDuringMigration = 0;

/**
 * Last observed X location of the mouse pointer (freezes when tooltip appears).
 */
let lastX = 0;

/**
 * Last observed Y location of the mouse pointer (freezes when tooltip appears).
 */
let lastY = 0;

/** Current element being pointed at. */
let element: AnyDuringMigration = null;

/**
 * Once a tooltip has opened for an element, that element is 'poisoned' and
 * cannot respawn a tooltip until the pointer moves over a different element.
 */
let poisonedElement: AnyDuringMigration = null;

/**
 * Horizontal offset between mouse cursor and tooltip.
 *
 * @alias Blockly.Tooltip.OFFSET_X
 */
export const OFFSET_X = 0;

/**
 * Vertical offset between mouse cursor and tooltip.
 *
 * @alias Blockly.Tooltip.OFFSET_Y
 */
export const OFFSET_Y = 10;

/**
 * Radius mouse can move before killing tooltip.
 *
 * @alias Blockly.Tooltip.RADIUS_OK
 */
export const RADIUS_OK = 10;

/**
 * Delay before tooltip appears.
 *
 * @alias Blockly.Tooltip.HOVER_MS
 */
export const HOVER_MS = 750;

/**
 * Horizontal padding between tooltip and screen edge.
 *
 * @alias Blockly.Tooltip.MARGINS
 */
export const MARGINS = 5;

/** The HTML container.  Set once by createDom. */
let containerDiv: HTMLDivElement|null = null;

/**
 * Returns the HTML tooltip container.
 *
 * @returns The HTML tooltip container.
 * @alias Blockly.Tooltip.getDiv
 */
export function getDiv(): HTMLDivElement|null {
  return containerDiv;
}

/**
 * Returns the tooltip text for the given element.
 *
 * @param object The object to get the tooltip text of.
 * @returns The tooltip text of the element.
 * @alias Blockly.Tooltip.getTooltipOfObject
 */
export function getTooltipOfObject(object: AnyDuringMigration|null): string {
  const obj = getTargetObject(object);
  if (obj) {
    let tooltip = obj.tooltip;
    while (typeof tooltip === 'function') {
      tooltip = tooltip();
    }
    if (typeof tooltip !== 'string') {
      throw Error('Tooltip function must return a string.');
    }
    return tooltip;
  }
  return '';
}

/**
 * Returns the target object that the given object is targeting for its
 * tooltip. Could be the object itself.
 *
 * @param obj The object are trying to find the target tooltip object of.
 * @returns The target tooltip object.
 */
function getTargetObject(obj: object|null): {tooltip: AnyDuringMigration}|null {
  while (obj && (obj as any).tooltip) {
    if (typeof (obj as any).tooltip === 'string' ||
        typeof (obj as any).tooltip === 'function') {
      return obj as {tooltip: string | (() => string)};
    }
    obj = (obj as any).tooltip;
  }
  return null;
}

/**
 * Create the tooltip div and inject it onto the page.
 *
 * @alias Blockly.Tooltip.createDom
 */
export function createDom() {
  if (containerDiv) {
    return;  // Already created.
  }
  // Create an HTML container for popup overlays (e.g. editor widgets).
  containerDiv = document.createElement('div');
  containerDiv.className = 'blocklyTooltipDiv';
  const container = common.getParentContainer() || document.body;
  container.appendChild(containerDiv);
}

/**
 * Binds the required mouse events onto an SVG element.
 *
 * @param element SVG element onto which tooltip is to be bound.
 * @alias Blockly.Tooltip.bindMouseEvents
 */
export function bindMouseEvents(element: Element) {
  // TODO (#6097): Don't stash wrapper info on the DOM.
  (element as AnyDuringMigration).mouseOverWrapper_ =
      browserEvents.bind(element, 'mouseover', null, onMouseOver);
  (element as AnyDuringMigration).mouseOutWrapper_ =
      browserEvents.bind(element, 'mouseout', null, onMouseOut);

  // Don't use bindEvent_ for mousemove since that would create a
  // corresponding touch handler, even though this only makes sense in the
  // context of a mouseover/mouseout.
  element.addEventListener('mousemove', onMouseMove, false);
}

/**
 * Unbinds tooltip mouse events from the SVG element.
 *
 * @param element SVG element onto which tooltip is bound.
 * @alias Blockly.Tooltip.unbindMouseEvents
 */
export function unbindMouseEvents(element: Element) {
  if (!element) {
    return;
  }
  // TODO (#6097): Don't stash wrapper info on the DOM.
  browserEvents.unbind((element as AnyDuringMigration).mouseOverWrapper_);
  browserEvents.unbind((element as AnyDuringMigration).mouseOutWrapper_);
  element.removeEventListener('mousemove', onMouseMove);
}

/**
 * Hide the tooltip if the mouse is over a different object.
 * Initialize the tooltip to potentially appear for this object.
 *
 * @param e Mouse event.
 */
function onMouseOver(e: Event) {
  if (blocked) {
    // Someone doesn't want us to show tooltips.
    return;
  }
  // If the tooltip is an object, treat it as a pointer to the next object in
  // the chain to look at.  Terminate when a string or function is found.
  const newElement = getTargetObject(e.currentTarget);
  if (element !== newElement) {
    hide();
    poisonedElement = null;
    element = newElement;
  }
  // Forget about any immediately preceding mouseOut event.
  clearTimeout(mouseOutPid);
}

/**
 * Hide the tooltip if the mouse leaves the object and enters the workspace.
 *
 * @param _e Mouse event.
 */
function onMouseOut(_e: Event) {
  if (blocked) {
    // Someone doesn't want us to show tooltips.
    return;
  }
  // Moving from one element to another (overlapping or with no gap) generates
  // a mouseOut followed instantly by a mouseOver.  Fork off the mouseOut
  // event and kill it if a mouseOver is received immediately.
  // This way the task only fully executes if mousing into the void.
  mouseOutPid = setTimeout(function() {
    element = null;
    poisonedElement = null;
    hide();
  }, 1);
  clearTimeout(showPid);
}

/**
 * When hovering over an element, schedule a tooltip to be shown.  If a tooltip
 * is already visible, hide it if the mouse strays out of a certain radius.
 *
 * @param e Mouse event.
 */
function onMouseMove(e: Event) {
  if (!element || !(element as AnyDuringMigration).tooltip) {
    // No tooltip here to show.
    return;
  } else if (blocked) {
    // Someone doesn't want us to show tooltips.  We are probably handling a
    // user gesture, such as a click or drag.
    return;
  }
  if (visible) {
    // Compute the distance between the mouse position when the tooltip was
    // shown and the current mouse position.  Pythagorean theorem.
    // AnyDuringMigration because:  Property 'pageX' does not exist on type
    // 'Event'.
    const dx = lastX - (e as AnyDuringMigration).pageX;
    // AnyDuringMigration because:  Property 'pageY' does not exist on type
    // 'Event'.
    const dy = lastY - (e as AnyDuringMigration).pageY;
    if (Math.sqrt(dx * dx + dy * dy) > RADIUS_OK) {
      hide();
    }
  } else if (poisonedElement !== element) {
    // The mouse moved, clear any previously scheduled tooltip.
    clearTimeout(showPid);
    // Maybe this time the mouse will stay put.  Schedule showing of tooltip.
    // AnyDuringMigration because:  Property 'pageX' does not exist on type
    // 'Event'.
    lastX = (e as AnyDuringMigration).pageX;
    // AnyDuringMigration because:  Property 'pageY' does not exist on type
    // 'Event'.
    lastY = (e as AnyDuringMigration).pageY;
    showPid = setTimeout(show, HOVER_MS);
  }
}

/**
 * Dispose of the tooltip.
 *
 * @alias Blockly.Tooltip.dispose
 * @internal
 */
export function dispose() {
  element = null;
  poisonedElement = null;
  hide();
}

/**
 * Hide the tooltip.
 *
 * @alias Blockly.Tooltip.hide
 */
export function hide() {
  if (visible) {
    visible = false;
    if (containerDiv) {
      containerDiv.style.display = 'none';
    }
  }
  if (showPid) {
    clearTimeout(showPid);
  }
}

/**
 * Hide any in-progress tooltips and block showing new tooltips until the next
 * call to unblock().
 *
 * @alias Blockly.Tooltip.block
 * @internal
 */
export function block() {
  hide();
  blocked = true;
}

/**
 * Unblock tooltips: allow them to be scheduled and shown according to their own
 * logic.
 *
 * @alias Blockly.Tooltip.unblock
 * @internal
 */
export function unblock() {
  blocked = false;
}

/** Renders the tooltip content into the tooltip div. */
function renderContent() {
  if (!containerDiv || !element) {
    // This shouldn't happen, but if it does, we can't render.
    return;
  }
  if (typeof customTooltip === 'function') {
    customTooltip(containerDiv, element);
  } else {
    renderDefaultContent();
  }
}

/** Renders the default tooltip UI. */
function renderDefaultContent() {
  let tip = getTooltipOfObject(element);
  tip = blocklyString.wrap(tip, LIMIT);
  // Create new text, line by line.
  const lines = tip.split('\n');
  for (let i = 0; i < lines.length; i++) {
    const div = (document.createElement('div'));
    div.appendChild(document.createTextNode(lines[i]));
    containerDiv!.appendChild(div);
  }
}

/**
 * Gets the coordinates for the tooltip div, taking into account the edges of
 * the screen to prevent showing the tooltip offscreen.
 *
 * @param rtl True if the tooltip should be in right-to-left layout.
 * @returns Coordinates at which the tooltip div should be placed.
 */
function getPosition(rtl: boolean): {x: number, y: number} {
  // Position the tooltip just below the cursor.
  const windowWidth = document.documentElement.clientWidth;
  const windowHeight = document.documentElement.clientHeight;

  let anchorX = lastX;
  if (rtl) {
    anchorX -= OFFSET_X + containerDiv!.offsetWidth;
  } else {
    anchorX += OFFSET_X;
  }

  let anchorY = lastY + OFFSET_Y;
  if (anchorY + containerDiv!.offsetHeight > windowHeight + window.scrollY) {
    // Falling off the bottom of the screen; shift the tooltip up.
    anchorY -= containerDiv!.offsetHeight + 2 * OFFSET_Y;
  }

  if (rtl) {
    // Prevent falling off left edge in RTL mode.
    anchorX = Math.max(MARGINS - window.scrollX, anchorX);
  } else {
    if (anchorX + containerDiv!.offsetWidth >
        windowWidth + window.scrollX - 2 * MARGINS) {
      // Falling off the right edge of the screen;
      // clamp the tooltip on the edge.
      anchorX = windowWidth - containerDiv!.offsetWidth - 2 * MARGINS;
    }
  }

  return {x: anchorX, y: anchorY};
}

/** Create the tooltip and show it. */
function show() {
  if (blocked) {
    // Someone doesn't want us to show tooltips.
    return;
  }
  poisonedElement = element;
  if (!containerDiv) {
    return;
  }
  // Erase all existing text.
  containerDiv.textContent = '';

  // Add new content.
  renderContent();

  // Display the tooltip.
  const rtl = (element as any).RTL;
  containerDiv.style.direction = rtl ? 'rtl' : 'ltr';
  containerDiv.style.display = 'block';
  visible = true;

  const {x, y} = getPosition(rtl);
  containerDiv.style.left = x + 'px';
  containerDiv.style.top = y + 'px';
}