import { MathPoint } from '../helper/Calc';
import Draggable from '../elements/base/Draggable';
import Line from '../elements/Line';
import Point from '../elements/Point';
import Shape from '../elements/Shape';
import SelectionRect from '../components/SelectionRect';
import EventManager from './EventManager';
import DividerLine from '../elements/DividerLine';
import CanvasManager from './CanvasManager';

const SNAP_SPACING = 50;
export default class InteractionManager extends EventManager {
  private _mode: InteractionMode = 'select';
  protected _snapSpacing: number | null = SNAP_SPACING;
  private snap<Value extends number | MathPoint>(value: Value): Value {
    if (this._snapSpacing === null || this.keys.alt) return value;
    if (typeof value === 'object') {
      return {
        ...value,
        x: this.snap(value.x),
        y: this.snap(value.y)
      } as Value;
    } else
      return (Math.round((value as number) / this._snapSpacing) *
        this._snapSpacing) as Value;
  }
  public get snapping() {
    return this._snapSpacing !== null;
  }
  public toggleSnapping(snapping = !this.snapping) {
    this._snapSpacing = snapping ? SNAP_SPACING * (this.scale ?? 1) : null;
    // request redraw is not neccessary but requestRedraw also triggers an update (-> updates the attributes of the webcomponent)
    this.requestRedraw();
  }

  private _showGrid = true;
  public get showGrid() {
    return this._showGrid;
  }
  public toggleGrid(show = !this.showGrid) {
    this._showGrid = show;
    this.requestRedraw();
  }

  protected baseScale = 1 / 50;
  protected _scale: number = 1;
  public get scale() {
    return this._scale * this.baseScale;
  }
  public setScale(scale: number | null) {
    this._scale = scale || 1;
    this.requestRedraw();
  }

  protected redraw(ctx: CanvasRenderingContext2D): void {
    super.redraw(ctx);
    this.selectionRect?.draw(ctx);
    this.ghostLine?.draw(ctx);
    this.ghostDividerLine?.draw(ctx);
    if (this.showGrid) {
      const spacing = SNAP_SPACING;
      ctx.strokeStyle = '#00000050';
      ctx.lineWidth = 1;
      ctx.setLineDash([]);
      ctx.beginPath();
      const { width, height } = this.getCanvasDimensions();
      for (let x = 0; x < width; x += spacing) {
        ctx.moveTo(x, 0);
        ctx.lineTo(x, height);
      }
      for (let y = 0; y < height; y += spacing) {
        ctx.moveTo(0, y);
        ctx.lineTo(width, y);
      }
      ctx.stroke();
    }
  }

  /**
   * When creating a shape in create mode
   */
  private creatingShape: { shape: Shape; lastPoint: Point } | null = null;
  protected handleClick(
    this: CanvasManager,
    {
      hit,
      ctrlPressed,
      alreadySelected,
      isRightClick,
      coords
    }: {
      coords: MathPoint;
      hit: Draggable | null;
      alreadySelected: boolean;
      ctrlPressed: boolean;
      isRightClick: boolean;
    }
  ) {
    coords = this.snap(coords);
    switch (this._mode) {
      case 'select':
      case 'divider':
        if (this.selectionRect) {
          const newSelections = this.selectionRect.getSelectedElements(
            this.getChildren()
          );
          this.select(newSelections, { keepSelection: ctrlPressed });
          this.selectionRect = null;
          this.requestRedraw();
          return;
        }

        // do not unselect on context menu
        if (isRightClick && alreadySelected) break;

        // do not select certain objects
        if (hit && !this.canSelect(hit)) break;

        if (hit) {
          if (alreadySelected) {
            if (ctrlPressed) {
              // when clicking on a selected element while holding ctrl, we want to deselect it
              this.blur(hit);
            } else {
              // blur clicked element / blur everything
              this.blur(hit);
            }
          } else {
            if (ctrlPressed) {
              // when clicking on an unselected element while holding ctrl, we want to select it and keep the other elements selected
              this.select(hit, { keepSelection: true });
            } else {
              // when clicking on an unselected element while not holding ctrl, we want to select it and deselect the other elements
              this.select(hit, { keepSelection: false });
            }
          }
        } else {
          if (!ctrlPressed) this.blur();
        }
        break;
      case 'create':
        if (!hit) {
          if (isRightClick) {
            this.ghostLine = null;
            this.creatingShape = null;
          } else {
            if (this.creatingShape) {
              // add point to creating shape
              const point = this.creatingShape.shape.addPoint(
                coords,
                this.creatingShape.lastPoint
              );
              if (point) this.creatingShape.lastPoint = point;

              this.requestRedraw();
            } else {
              // create new point
              const shape = Shape.createPoint(this, coords);
              this.addChild(shape);
              this.creatingShape = {
                shape,
                lastPoint: shape.getPoints()[0]
              };
            }
            this.ghostLine = new Line(this, {
              start: coords,
              end: coords
            });
            this.ghostLine.setStroke('#000000b0');
          }
        } else if (hit instanceof Line) {
          // create new point in line
          const shape = (
            this.getChildren((s) => s instanceof Shape) as Shape[]
          ).find((shape) => shape.hasChild(hit));
          if (!shape) break;
          const point = new Point(this, coords);
          shape.addPoint(point);
          this.requestRedraw();
        } else if (hit instanceof Point) {
          if (this.creatingShape) {
            const isLastPoint = hit === this.creatingShape.lastPoint;
            const isEndpoint = this.creatingShape.shape.isEndPoint(hit);
            const isChild = this.creatingShape.shape.hasChild(hit);
            // when clicking on other endpoint -> connect
            if (!isLastPoint && isEndpoint) {
              this.creatingShape.shape.connectPoints(
                hit,
                this.creatingShape.lastPoint
              );
              this.ghostLine = null;
              this.creatingShape = null;
            } else if (isChild) {
              // when clicking on any other point of same shape -> end creating shape
              this.ghostLine = null;
              this.creatingShape = null;
            } else {
              // when clicking on an endpoint of another shape -> connect
              const shape = (
                this.getChildren((s) => s instanceof Shape) as Shape[]
              ).find((shape) => shape.hasChild(hit));
              if (!shape || !shape.isEndPoint(hit)) break;
              this.creatingShape.shape.connect(
                shape,
                this.creatingShape.lastPoint,
                hit
              );
              this.ghostLine = null;
              this.creatingShape = null;
            }
          }
        }
        break;
    }
  }

  protected handleMouseMove({ current }: { current: MathPoint }) {
    switch (this.mode) {
      case 'create':
        if (this.ghostLine) this.ghostLine.setEnd(current);
        this.requestRedraw();
        break;
    }
  }

  private ghostLine: Line | null = null;
  private ghostDividerLine: DividerLine | null = null;
  private selectionRect: SelectionRect | null = null;
  protected handleDragStart(
    this: CanvasManager,
    {
      start,
      hit
    }: {
      start: MathPoint;
      hit: Draggable | null;
    }
  ) {
    switch (this._mode) {
      case 'select':
        // only draw selection rect if we're not dragging an element
        if (!hit) {
          if (!this.keys.ctrl) this.blur();
          this.selectionRect = new SelectionRect({
            x: start.x,
            y: start.y
          });
        }
        break;
      case 'create':
        // if dragging point -> create line starting at point
        if (hit && hit instanceof Point) {
          const shape = (
            this.getChildren((s) => s instanceof Shape) as Shape[]
          ).find((shape) => shape.hasChild(hit));
          if (!shape || !shape.isEndPoint(hit)) break;
          this.ghostLine = new Line(this, {
            start: {
              x: hit.x,
              y: hit.y
            },
            end: start
          });
          this.ghostLine.setStroke('#000000b0');
        }
        break;
      case 'divider':
        if (!hit || !this.canSelect(hit))
          // create line from startPoint
          this.ghostDividerLine = new DividerLine(this, {
            start: this.snap(start),
            end: this.snap(start)
          });
        break;
    }
  }

  protected handleDragging({
    start,
    current,
    element,
    dragStart
  }: {
    start: MathPoint;
    current: MathPoint;
    element: Draggable | null;
    dragStart: MathPoint & { startPositions: MathPoint[] };
  }) {
    switch (this._mode) {
      case 'select':
      case 'divider':
        if (this.ghostDividerLine) {
          this.ghostDividerLine.setEnd(this.snap(current));
          this.requestRedraw();
        }

        if (this.selected.length > 0 && element) {
          // drag currently selected element
          const change = {
            x: current.x - start.x,
            y: current.y - start.y
          };

          this.selected.forEach((shape, index) => {
            const startCoords = dragStart.startPositions[index];
            const x = this.snap(startCoords.x + change.x);
            const y = this.snap(startCoords.y + change.y);

            // prevent moving element twice (move element and its parent)
            if (!this.selected.some((child) => child.hasChild(shape)))
              shape.move({ x, y, relative: false });
          });

          this.requestRedraw();
        } else {
          // draw selection rect
          if (this.selectionRect) {
            this.selectionRect.setSecondCoords(current);
            this.requestRedraw();
          }
        }
        break;
      case 'create':
        if (this.ghostLine) {
          this.ghostLine.setEnd(current);
          this.requestRedraw();
        }
        break;
    }
  }

  protected handleDragEnd(
    this: CanvasManager,
    {
      to,
      element
    }: {
      from: MathPoint;
      to: MathPoint;
      element: Draggable | null;
    }
  ) {
    switch (this._mode) {
      case 'select':
        if (this.selectionRect) {
          const newSelections = this.selectionRect.getSelectedElements(
            this.getChildren()
          );
          this.select(newSelections, { keepSelection: this.keys.ctrl });
          this.selectionRect = null;
        }
        if (element) {
          // snap to grid
          element.move({
            relative: false,
            x: this.snap(element.x),
            y: this.snap(element.y)
          });
        }
        break;
      case 'create':
        if (this.ghostLine && element) {
          // create new line from point -> check if lands on point -> end on point + merge shapes
          const hitElement = this.getElementAt(to);
          if (hitElement instanceof Point) {
            const end = hitElement;
            const start = element;

            const children = this.getChildren(
              (s) => s instanceof Shape
            ) as Shape[];
            const shape1 = children.find((shape) => shape.hasChild(start));
            const shape2 =
              end instanceof Shape
                ? end
                : children.find((shape) => shape.hasChild(end));

            if (!shape1 || !shape2) {
              console.error("Couldn't find shapes for merging");
            } else shape1.connect(shape2, element as Point, end);
          }
        }
        this.ghostLine = null;
        break;
      case 'divider':
        if (this.ghostDividerLine) {
          this.addChild(this.ghostDividerLine);
          this.ghostDividerLine = null;
        }
    }
    this.selectionRect = null;
    this.requestRedraw();
  }

  protected upadateCursor(coords: MathPoint): CSSStyleDeclaration['cursor'] {
    // check if we're hovering over a draggable element and change cursor accordingly
    const hit = this.getElementAt(coords);
    const canSelect = Boolean(hit && this.canSelect(hit));
    switch (this.mode) {
      case 'select':
        return hit && canSelect ? 'grab' : 'default';
      case 'create':
        if (hit && hit instanceof Point) {
          const shape = (
            this.getChildren((s) => s instanceof Shape) as Shape[]
          ).find((shape) => shape.hasChild(hit));
          const isEndPoint = shape?.isEndPoint(hit);
          return isEndPoint ? 'crosshair' : 'default';
        } else return 'pointer';
      case 'divider':
        return canSelect ? 'grab' : 'pointer';
      default:
        return 'default';
    }
  }

  protected handleKeyboardEvent(key: string) {
    // switch modes
    if (['d', 's', 'c'].some((k) => key.toLowerCase() === k)) {
      switch (key.toLowerCase()) {
        case 'c':
          this.mode = 'create';
          break;
        case 's':
          this.mode = 'select';
          break;
        case 'd':
          this.mode = 'divider';
          break;
      }
      return;
    }

    // delete selected elements
    switch (key) {
      case 'Delete':
      case 'Backspace':
        this.selected.forEach((shape) => shape.delete());
        this.blur();
        break;
    }

    // mode specific keyboard events
    switch (this.mode) {
      case 'select':
        switch (key) {
          case 'Escape':
            this.blur();
            break;
          case 'a':
          case 'A':
            if (this.keys.ctrl) {
              const toSelect = this.getChildren((child) =>
                this.canSelect(child)
              );
              this.select(toSelect);
            }
        }
        break;
      case 'create':
        switch (key) {
          case 'Escape':
            this.ghostLine = null;
            this.creatingShape = null;
            this.mode = 'select';
            this.requestRedraw();
            break;
        }
        break;
      case 'divider':
        switch (key) {
          case 'Escape':
            this.ghostDividerLine = null;
            this.mode = 'select';
            this.requestRedraw();
            break;
        }
        break;
    }
  }

  public canSelect(element: Draggable): boolean {
    if (this.mode === 'divider') {
      if (element instanceof DividerLine) return true;
      if (
        this.getChildren((child) => child instanceof DividerLine).some((line) =>
          line.hasChild(element)
        )
      )
        return true;
      return false;
    }
    return true;
  }

  public get mode() {
    return this._mode;
  }

  public set mode(mode: typeof this._mode) {
    this._mode = mode;
    this.ghostLine = null;
    this.creatingShape = null;
    this.ghostDividerLine = null;
    if (mode === 'divider') this.blur();
    else {
      this.getChildren((child) => child instanceof DividerLine).forEach(
        (line) => this.blur(line)
      );
    }
    this.requestRedraw();
  }

  public export() {
    return {
      ...super.export(),
      mode: this.mode,
      showGrid: this.showGrid,
      snapping: this.snapping
    };
  }

  public import(data: Partial<ReturnType<this['export']>>) {
    super.import(data);
    if (data.mode) this.mode = data.mode;
    if (data.showGrid !== undefined) this._showGrid = data.showGrid;
    if (data.snapping !== undefined) this.toggleSnapping(data.snapping);
  }
}