/**
 * Copyright (c) 2019 The xterm.js authors. All rights reserved.
 * @license MIT
 */

import { IBufferCellPosition, ILink, ILinkDecorations, ILinkWithState, ILinkifier2, ILinkifierEvent } from 'browser/Types';
import { Disposable, dispose, toDisposable } from 'vs/base/common/lifecycle';
import { IDisposable } from 'common/Types';
import { IBufferService } from 'common/services/Services';
import { ILinkProviderService, IMouseService, IRenderService } from './services/Services';
import { Emitter } from 'vs/base/common/event';
import { addDisposableListener } from 'vs/base/browser/dom';

export class Linkifier extends Disposable implements ILinkifier2 {
  public get currentLink(): ILinkWithState | undefined { return this._currentLink; }
  protected _currentLink: ILinkWithState | undefined;
  private _mouseDownLink: ILinkWithState | undefined;
  private _lastMouseEvent: MouseEvent | undefined;
  private _linkCacheDisposables: IDisposable[] = [];
  private _lastBufferCell: IBufferCellPosition | undefined;
  private _isMouseOut: boolean = true;
  private _wasResized: boolean = false;
  private _activeProviderReplies: Map<Number, ILinkWithState[] | undefined> | undefined;
  private _activeLine: number = -1;

  private readonly _onShowLinkUnderline = this._register(new Emitter<ILinkifierEvent>());
  public readonly onShowLinkUnderline = this._onShowLinkUnderline.event;
  private readonly _onHideLinkUnderline = this._register(new Emitter<ILinkifierEvent>());
  public readonly onHideLinkUnderline = this._onHideLinkUnderline.event;

  constructor(
    private readonly _element: HTMLElement,
    @IMouseService private readonly _mouseService: IMouseService,
    @IRenderService private readonly _renderService: IRenderService,
    @IBufferService private readonly _bufferService: IBufferService,
    @ILinkProviderService private readonly _linkProviderService: ILinkProviderService
  ) {
    super();
    this._register(toDisposable(() => {
      dispose(this._linkCacheDisposables);
      this._linkCacheDisposables.length = 0;
      this._lastMouseEvent = undefined;
      // Clear out link providers as they could easily cause an embedder memory leak
      this._activeProviderReplies?.clear();
    }));
    // Listen to resize to catch the case where it's resized and the cursor is out of the viewport.
    this._register(this._bufferService.onResize(() => {
      this._clearCurrentLink();
      this._wasResized = true;
    }));
    this._register(addDisposableListener(this._element, 'mouseleave', () => {
      this._isMouseOut = true;
      this._clearCurrentLink();
    }));
    this._register(addDisposableListener(this._element, 'mousemove', this._handleMouseMove.bind(this)));
    this._register(addDisposableListener(this._element, 'mousedown', this._handleMouseDown.bind(this)));
    this._register(addDisposableListener(this._element, 'mouseup', this._handleMouseUp.bind(this)));
  }

  private _handleMouseMove(event: MouseEvent): void {
    this._lastMouseEvent = event;

    const position = this._positionFromMouseEvent(event, this._element, this._mouseService);
    if (!position) {
      return;
    }
    this._isMouseOut = false;

    // Ignore the event if it's an embedder created hover widget
    const composedPath = event.composedPath() as HTMLElement[];
    for (let i = 0; i < composedPath.length; i++) {
      const target = composedPath[i];
      // Hit Terminal.element, break and continue
      if (target.classList.contains('xterm')) {
        break;
      }
      // It's a hover, don't respect hover event
      if (target.classList.contains('xterm-hover')) {
        return;
      }
    }

    if (!this._lastBufferCell || (position.x !== this._lastBufferCell.x || position.y !== this._lastBufferCell.y)) {
      this._handleHover(position);
      this._lastBufferCell = position;
    }
  }

  private _handleHover(position: IBufferCellPosition): void {
    // TODO: This currently does not cache link provider results across wrapped lines, activeLine
    //       should be something like `activeRange: {startY, endY}`
    // Check if we need to clear the link
    if (this._activeLine !== position.y || this._wasResized) {
      this._clearCurrentLink();
      this._askForLink(position, false);
      this._wasResized = false;
      return;
    }

    // Check the if the link is in the mouse position
    const isCurrentLinkInPosition = this._currentLink && this._linkAtPosition(this._currentLink.link, position);
    if (!isCurrentLinkInPosition) {
      this._clearCurrentLink();
      this._askForLink(position, true);
    }
  }

  private _askForLink(position: IBufferCellPosition, useLineCache: boolean): void {
    if (!this._activeProviderReplies || !useLineCache) {
      this._activeProviderReplies?.forEach(reply => {
        reply?.forEach(linkWithState => {
          if (linkWithState.link.dispose) {
            linkWithState.link.dispose();
          }
        });
      });
      this._activeProviderReplies = new Map();
      this._activeLine = position.y;
    }
    let linkProvided = false;

    // There is no link cached, so ask for one
    for (const [i, linkProvider] of this._linkProviderService.linkProviders.entries()) {
      if (useLineCache) {
        const existingReply = this._activeProviderReplies?.get(i);
        // If there isn't a reply, the provider hasn't responded yet.

        // TODO: If there isn't a reply yet it means that the provider is still resolving. Ensuring
        // provideLinks isn't triggered again saves ILink.hover firing twice though. This probably
        // needs promises to get fixed
        if (existingReply) {
          linkProvided = this._checkLinkProviderResult(i, position, linkProvided);
        }
      } else {
        linkProvider.provideLinks(position.y, (links: ILink[] | undefined) => {
          if (this._isMouseOut) {
            return;
          }
          const linksWithState: ILinkWithState[] | undefined = links?.map(link  => ({ link }));
          this._activeProviderReplies?.set(i, linksWithState);
          linkProvided = this._checkLinkProviderResult(i, position, linkProvided);

          // If all providers have responded, remove lower priority links that intersect ranges of
          // higher priority links
          if (this._activeProviderReplies?.size === this._linkProviderService.linkProviders.length) {
            this._removeIntersectingLinks(position.y, this._activeProviderReplies);
          }
        });
      }
    }
  }

  private _removeIntersectingLinks(y: number, replies: Map<Number, ILinkWithState[] | undefined>): void {
    const occupiedCells = new Set<number>();
    for (let i = 0; i < replies.size; i++) {
      const providerReply = replies.get(i);
      if (!providerReply) {
        continue;
      }
      for (let i = 0; i < providerReply.length; i++) {
        const linkWithState = providerReply[i];
        const startX = linkWithState.link.range.start.y < y ? 0 : linkWithState.link.range.start.x;
        const endX = linkWithState.link.range.end.y > y ? this._bufferService.cols : linkWithState.link.range.end.x;
        for (let x = startX; x <= endX; x++) {
          if (occupiedCells.has(x)) {
            providerReply.splice(i--, 1);
            break;
          }
          occupiedCells.add(x);
        }
      }
    }
  }

  private _checkLinkProviderResult(index: number, position: IBufferCellPosition, linkProvided: boolean): boolean {
    if (!this._activeProviderReplies) {
      return linkProvided;
    }

    const links = this._activeProviderReplies.get(index);

    // Check if every provider before this one has come back undefined
    let hasLinkBefore = false;
    for (let j = 0; j < index; j++) {
      if (!this._activeProviderReplies.has(j) || this._activeProviderReplies.get(j)) {
        hasLinkBefore = true;
      }
    }

    // If all providers with higher priority came back undefined, then this provider's link for
    // the position should be used
    if (!hasLinkBefore && links) {
      const linkAtPosition = links.find(link => this._linkAtPosition(link.link, position));
      if (linkAtPosition) {
        linkProvided = true;
        this._handleNewLink(linkAtPosition);
      }
    }

    // Check if all the providers have responded
    if (this._activeProviderReplies.size === this._linkProviderService.linkProviders.length && !linkProvided) {
      // Respect the order of the link providers
      for (let j = 0; j < this._activeProviderReplies.size; j++) {
        const currentLink = this._activeProviderReplies.get(j)?.find(link => this._linkAtPosition(link.link, position));
        if (currentLink) {
          linkProvided = true;
          this._handleNewLink(currentLink);
          break;
        }
      }
    }

    return linkProvided;
  }

  private _handleMouseDown(): void {
    this._mouseDownLink = this._currentLink;
  }

  private _handleMouseUp(event: MouseEvent): void {
    if (!this._currentLink) {
      return;
    }

    const position = this._positionFromMouseEvent(event, this._element, this._mouseService);
    if (!position) {
      return;
    }

    if (this._mouseDownLink && linkEquals(this._mouseDownLink.link, this._currentLink.link) && this._linkAtPosition(this._currentLink.link, position)) {
      this._currentLink.link.activate(event, this._currentLink.link.text);
    }
  }

  private _clearCurrentLink(startRow?: number, endRow?: number): void {
    if (!this._currentLink || !this._lastMouseEvent) {
      return;
    }

    // If we have a start and end row, check that the link is within it
    if (!startRow || !endRow || (this._currentLink.link.range.start.y >= startRow && this._currentLink.link.range.end.y <= endRow)) {
      this._linkLeave(this._element, this._currentLink.link, this._lastMouseEvent);
      this._currentLink = undefined;
      dispose(this._linkCacheDisposables);
      this._linkCacheDisposables.length = 0;
    }
  }

  private _handleNewLink(linkWithState: ILinkWithState): void {
    if (!this._lastMouseEvent) {
      return;
    }

    const position = this._positionFromMouseEvent(this._lastMouseEvent, this._element, this._mouseService);

    if (!position) {
      return;
    }

    // Trigger hover if the we have a link at the position
    if (this._linkAtPosition(linkWithState.link, position)) {
      this._currentLink = linkWithState;
      this._currentLink.state = {
        decorations: {
          underline: linkWithState.link.decorations === undefined ? true : linkWithState.link.decorations.underline,
          pointerCursor: linkWithState.link.decorations === undefined ? true : linkWithState.link.decorations.pointerCursor
        },
        isHovered: true
      };
      this._linkHover(this._element, linkWithState.link, this._lastMouseEvent);

      // Add listener for tracking decorations changes
      linkWithState.link.decorations = {} as ILinkDecorations;
      Object.defineProperties(linkWithState.link.decorations, {
        pointerCursor: {
          get: () => this._currentLink?.state?.decorations.pointerCursor,
          set: v => {
            if (this._currentLink?.state && this._currentLink.state.decorations.pointerCursor !== v) {
              this._currentLink.state.decorations.pointerCursor = v;
              if (this._currentLink.state.isHovered) {
                this._element.classList.toggle('xterm-cursor-pointer', v);
              }
            }
          }
        },
        underline: {
          get: () => this._currentLink?.state?.decorations.underline,
          set: v => {
            if (this._currentLink?.state && this._currentLink?.state?.decorations.underline !== v) {
              this._currentLink.state.decorations.underline = v;
              if (this._currentLink.state.isHovered) {
                this._fireUnderlineEvent(linkWithState.link, v);
              }
            }
          }
        }
      });

      // Listen to viewport changes to re-render the link under the cursor (only when the line the
      // link is on changes)
      this._linkCacheDisposables.push(this._renderService.onRenderedViewportChange(e => {
        // Sanity check, this shouldn't happen in practice as this listener would be disposed
        if (!this._currentLink) {
          return;
        }
        // When start is 0 a scroll most likely occurred, make sure links above the fold also get
        // cleared.
        const start = e.start === 0 ? 0 : e.start + 1 + this._bufferService.buffer.ydisp;
        const end = this._bufferService.buffer.ydisp + 1 + e.end;
        // Only clear the link if the viewport change happened on this line
        if (this._currentLink.link.range.start.y >= start && this._currentLink.link.range.end.y <= end) {
          this._clearCurrentLink(start, end);
          if (this._lastMouseEvent) {
            // re-eval previously active link after changes
            const position = this._positionFromMouseEvent(this._lastMouseEvent, this._element, this._mouseService!);
            if (position) {
              this._askForLink(position, false);
            }
          }
        }
      }));
    }
  }

  protected _linkHover(element: HTMLElement, link: ILink, event: MouseEvent): void {
    if (this._currentLink?.state) {
      this._currentLink.state.isHovered = true;
      if (this._currentLink.state.decorations.underline) {
        this._fireUnderlineEvent(link, true);
      }
      if (this._currentLink.state.decorations.pointerCursor) {
        element.classList.add('xterm-cursor-pointer');
      }
    }

    if (link.hover) {
      link.hover(event, link.text);
    }
  }

  private _fireUnderlineEvent(link: ILink, showEvent: boolean): void {
    const range = link.range;
    const scrollOffset = this._bufferService.buffer.ydisp;
    const event = this._createLinkUnderlineEvent(range.start.x - 1, range.start.y - scrollOffset - 1, range.end.x, range.end.y - scrollOffset - 1, undefined);
    const emitter = showEvent ? this._onShowLinkUnderline : this._onHideLinkUnderline;
    emitter.fire(event);
  }

  protected _linkLeave(element: HTMLElement, link: ILink, event: MouseEvent): void {
    if (this._currentLink?.state) {
      this._currentLink.state.isHovered = false;
      if (this._currentLink.state.decorations.underline) {
        this._fireUnderlineEvent(link, false);
      }
      if (this._currentLink.state.decorations.pointerCursor) {
        element.classList.remove('xterm-cursor-pointer');
      }
    }

    if (link.leave) {
      link.leave(event, link.text);
    }
  }

  /**
   * Check if the buffer position is within the link
   * @param link
   * @param position
   */
  private _linkAtPosition(link: ILink, position: IBufferCellPosition): boolean {
    const lower = link.range.start.y * this._bufferService.cols + link.range.start.x;
    const upper = link.range.end.y * this._bufferService.cols + link.range.end.x;
    const current = position.y * this._bufferService.cols + position.x;
    return (lower <= current && current <= upper);
  }

  /**
   * Get the buffer position from a mouse event
   * @param event
   */
  private _positionFromMouseEvent(event: MouseEvent, element: HTMLElement, mouseService: IMouseService): IBufferCellPosition | undefined {
    const coords = mouseService.getCoords(event, element, this._bufferService.cols, this._bufferService.rows);
    if (!coords) {
      return;
    }

    return { x: coords[0], y: coords[1] + this._bufferService.buffer.ydisp };
  }

  private _createLinkUnderlineEvent(x1: number, y1: number, x2: number, y2: number, fg: number | undefined): ILinkifierEvent {
    return { x1, y1, x2, y2, cols: this._bufferService.cols, fg };
  }
}

function linkEquals(a: ILink, b: ILink): boolean {
  return (
    a.text === b.text &&
    a.range.start.x === b.range.start.x &&
    a.range.start.y === b.range.start.y &&
    a.range.end.x === b.range.end.x &&
    a.range.end.y === b.range.end.y
  );
}