import { DiagramComponent } from "./diagram-component.js";

/**
 * Render a nested group frame around diagram components.
 *
 * A group is a view-level container, not a domain model. It owns membership,
 * expanded state and frame geometry while DiagramEngine continues to own the
 * lifetime of nodes and links. Application code can map a wiki submap or any
 * other grouping concept onto this generic abstraction.
 */
export class DiagramGroup {
  /**
   * goal   : Create an empty diagram group attached to one engine.
   * pre    : engine is a DiagramEngine and options contains only presentation data.
   * post   : The group has no members and has not yet rendered a frame.
   * result : A DiagramGroup instance.
   * internals : Membership is kept as a Set so nested groups and repeated add
   * operations remain deterministic; bounds are calculated from member handles.
   */
  constructor(engine, options = {}) {
    if (!engine) throw new TypeError("A diagram engine is required");
    this.engine = engine;
    this.label = String(options.label || "");
    this.className = String(options.className || "cmap-group-frame");
    this.backgroundColor = options.backgroundColor || "transparent";
    this.borderColor = options.borderColor || "#5d6d7e";
    this.padding = Number.isFinite(Number(options.padding)) ? Number(options.padding) : 24;
    this.depth = Number.isFinite(Number(options.depth)) ? Number(options.depth) : 0;
    this.expanded = options.expanded !== false;
    this.manageVisibility = options.manageVisibility !== false;
    this.members = new Set();
    this.elementValue = null;
    this.onToggleHandler = null;
    this.onPointerDownHandler = options.onPointerDown || null;
    this.onDoubleClickHandler = options.onDoubleClick || null;
  }

  /**
   * goal   : Add one node or nested group to this group.
   * pre    : member belongs to the same DiagramEngine.
   * post   : The member contributes to group bounds and rendering.
   * result : This group, for fluent setup.
   */
  add(member) {
    if (!(member instanceof DiagramComponent) && !(member instanceof DiagramGroup)) {
      throw new TypeError("A diagram group member is required");
    }
    if (member.engine !== this.engine) throw new TypeError("Group member belongs to another engine");
    this.members.add(member);
    this.redraw();
    return this;
  }

  /** Remove a member and update the frame. */
  remove(member) {
    this.members.delete(member);
    this.redraw();
    return this;
  }

  /** Register the callback invoked when the generic frame toggle is clicked. */
  onToggle(handler) {
    if (handler !== null && handler !== undefined && typeof handler !== "function") {
      throw new TypeError("Invalid group toggle handler");
    }
    this.onToggleHandler = handler || null;
    return this;
  }

  /**
   * goal   : Set the visual appearance of the group frame.
   * pre    : values contains optional CSS colour values.
   * post   : The next redraw uses the supplied background and border colours.
   * result : This group, for fluent setup.
   * internals : Values are kept on the group and applied as CSS custom
   * properties in redraw(), allowing application-specific frame styles.
   */
  setAppearance(values = {}) {
    if (values.backgroundColor !== undefined) this.backgroundColor = String(values.backgroundColor);
    if (values.borderColor !== undefined) this.borderColor = String(values.borderColor);
    if (values.label !== undefined) this.label = String(values.label);
    this.redraw();
    return this;
  }

  /**
   * goal   : Change whether group contents are shown.
   * pre    : expanded is boolean-coercible.
   * post   : The frame and all member components reflect the new state.
   * result : The resulting expanded state.
   * internals : A collapsed group hides direct members; nested groups redraw
   * themselves so their own frames disappear with the enclosing group.
   */
  setExpanded(expanded) {
    this.expanded = Boolean(expanded);
    if (this.manageVisibility) {
      for (const member of this.members) {
        if (member instanceof DiagramGroup) member.setExpanded(this.expanded && member.expanded);
        else member.visible(this.expanded);
      }
    }
    this.redraw();
    return this.expanded;
  }

  /** Return the union bounds of visible member nodes and nested groups. */
  bounds() {
    const members = [...this.members]
      .map((member) => member instanceof DiagramGroup ? member.bounds() :
        (member.visible() ? this.componentBounds(member) : null))
      .filter(Boolean);
    if (!members.length) return null;
    return {
      left: Math.min(...members.map((bounds) => bounds.left)) - this.padding,
      top: Math.min(...members.map((bounds) => bounds.top)) - this.padding,
      right: Math.max(...members.map((bounds) => bounds.right)) + this.padding,
      bottom: Math.max(...members.map((bounds) => bounds.bottom)) + this.padding
    };
  }

  /** Return the DOM frame, if the group currently has one. */
  element() {
    return this.elementValue;
  }

  /**
   * Render or remove the generic frame according to membership and state.
   * The engine calls this after component redraws; applications may call it
   * directly after changing group presentation or membership.
   */
  redraw() {
    const surface = this.engine.surfaceElement();
    const bounds = this.expanded && this.bounds();
    if (!surface || !bounds) {
      this.removeElement();
      return this;
    }
    if (!this.elementValue) {
      const frame = document.createElement("div");
      frame.className = this.className;
      frame.setAttribute("role", "group");
      for (const side of ["top", "right", "bottom", "left"]) {
        const dragEdge = document.createElement("div");
        dragEdge.className = `${this.className}-drag-edge ${this.className}-drag-edge-${side}`;
        if (this.onPointerDownHandler) dragEdge.addEventListener("pointerdown", this.onPointerDownHandler);
        if (this.onDoubleClickHandler) dragEdge.addEventListener("dblclick", this.onDoubleClickHandler);
        frame.append(dragEdge);
      }
      const toggle = document.createElement("button");
      toggle.type = "button";
      toggle.className = `${this.className}-toggle`;
      toggle.addEventListener("click", () => {
        this.setExpanded(!this.expanded);
        if (this.onToggleHandler) this.onToggleHandler(this, this.expanded);
      });
      frame.append(toggle);
      surface.prepend(frame);
      this.elementValue = frame;
    }
    const toggle = this.elementValue.querySelector(`.${this.className}-toggle`);
    if (toggle) {
      toggle.textContent = this.expanded ? "-" : "+";
      toggle.setAttribute("aria-expanded", String(this.expanded));
      toggle.setAttribute("aria-label", this.expanded ? "Collapse group" : "Expand group");
    }
    this.elementValue.setAttribute("aria-label", this.label);
    Object.assign(this.elementValue.style, {
      left: `${bounds.left}px`,
      top: `${bounds.top}px`,
      width: `${bounds.right - bounds.left}px`,
      height: `${bounds.bottom - bounds.top}px`,
      zIndex: String(this.depth)
    });
    this.elementValue.style.setProperty("--rw-cmap-submap-background", this.backgroundColor);
    this.elementValue.style.setProperty("--rw-cmap-submap-border", this.borderColor);
    return this;
  }

  /** Remove the frame and all references owned by this group. */
  destroy() {
    for (const member of this.members) {
      if (member instanceof DiagramGroup) member.destroy();
    }
    this.members.clear();
    this.removeElement();
  }

  componentBounds(component) {
    const attributes = component.attr();
    const x = Number(attributes.x);
    const y = Number(attributes.y);
    const width = Number(attributes.width);
    const height = Number(attributes.height);
    if (![x, y, width, height].every(Number.isFinite)) return null;
    return { left: x, top: y, right: x + width, bottom: y + height };
  }

  removeElement() {
    if (this.elementValue) {
      this.elementValue.remove();
      this.elementValue = null;
    }
  }
}