import type { Command } from '../../core/commands/Command';
import { oneStep } from '../../core/commands/CompoundCommand';
import { UnpackContainerCommand } from '../../core/commands/containerCommands';
import { ReorderObjectCommand, SetParentCommand } from '../../core/commands/sceneObjectCommands';
import { ancestorIdsOf, childIdsOf, findObject, visibleTreeOrder } from '../../core/model/hierarchy';
import { isLiveInstance, isTemplateContent, resolvedHolder } from '../../core/model/instance';
import { findAsset, type ObjectHolder } from '../../core/model/Project';
import { deviationMarks } from '../../core/properties/deviation';
import { type DropSpot, ListView, Menu, Panel, ScrollContainer } from '../../ui';
import {
  addCollider,
  addRigidbody,
  canAddCollider,
  canAddRigidbody,
  createContainer,
  removeObjects,
} from '../actions';
import { hasAssetEditor } from '../assetTabs';
import { ASSET_ICON_SVG } from './assetIcons';
import { type EditorState, objectSelection } from '../state';

/**
 * Objects of the scene or container being edited, as a tree; dragging re-parents or reorders and always
 * keeps world position. Fold state is view state kept here, never in the project.
 */
export class HierarchyPanel extends Panel {
  private readonly list = new ListView();
  private readonly scroll = new ScrollContainer();
  /** Ids of the objects whose children are shown. Anything missing is collapsed. */
  private readonly expanded = new Set<string>();
  /**
   * Which objects are listed. A function, not an id, so a container renamed or swapped under the
   * panel needs no notification; the Container tab points this at the template it edits.
   */
  private source: () => ObjectHolder | undefined = () => this.state.activeScene;
  /** Id of the holder the rows were built from, to notice when the source starts naming another. */
  private shownHolderId = '';

  constructor(private readonly state: EditorState) {
    super({ title: 'Scene objects', padding: 0, gap: 0 });
    this.minWidth = 160;
    this.list.emptyText = 'Place assets here';
    this.list.onSelect = (id, modifiers) => {
      const holder = this.holder();
      if (!holder) return;
      if (id && modifiers && (modifiers.ctrl || modifiers.shift)) state.toggleObject(holder.id, id);
      else state.select(id ? objectSelection(holder.id, [id]) : null);
    };
    this.list.onDrop = (draggedId, spot) => this.drop(draggedId, spot);
    this.list.onToggle = (id, expand) => this.setExpanded(id, expand);
    this.list.onActivate = (id) => this.setExpanded(id, !this.expanded.has(id));
    this.list.onContextMenu = (id, x, y) => this.openContextMenu(id, x, y);
    this.scroll.setContent(this.list);
    this.content.add(this.scroll, 1);

    state.on('project', () => this.refresh());
    // A different project brings different objects – start folded again.
    state.on('load', () => {
      this.expanded.clear();
      this.refresh();
    });
    state.on('selection', () => {
      // The Container tab's picker only changes the selection, which swaps the holder under this
      // panel; without the id check the title and rows would keep naming the previous one.
      const swapped = (this.holder()?.id ?? '') !== this.shownHolderId;
      if (this.revealSelection() || swapped) this.refresh();
      else this.syncSelection();
    });
    this.refresh();
  }

  /** A move that leaves the order as it is does nothing, so a drag back to its start costs no undo step. */
  private drop(draggedId: string, spot: DropSpot): void {
    const holder = this.holder();
    const object = holder && findObject(holder, draggedId);
    if (!holder || !object) return;
    if (spot.at === 'onto') {
      if (object.parentId === spot.targetId) return;
      // Unfold the new parent, otherwise the dragged row would seem to vanish on drop.
      this.expanded.add(spot.targetId);
      this.state.execute(new SetParentCommand(holder.id, draggedId, spot.targetId));
      return;
    }
    let parentId = '';
    let beforeId = '';
    if (spot.at !== 'end') {
      const target = findObject(holder, spot.targetId);
      if (!target) return;
      parentId = target.parentId;
      const order = childIdsOf(holder, parentId);
      beforeId = spot.at === 'before' ? target.id : (order[order.indexOf(target.id) + 1] ?? '');
    }
    if (beforeId === draggedId) return;
    const siblings = childIdsOf(holder, parentId);
    const rest = siblings.filter((id) => id !== draggedId);
    const at = beforeId ? rest.indexOf(beforeId) : rest.length;
    const wanted = [...rest.slice(0, at), draggedId, ...rest.slice(at)];
    if (object.parentId === parentId && wanted.join() === siblings.join()) return;
    const commands: Command[] = [];
    if (object.parentId !== parentId) commands.push(new SetParentCommand(holder.id, draggedId, parentId));
    commands.push(new ReorderObjectCommand(holder.id, draggedId, beforeId));
    if (parentId) this.expanded.add(parentId);
    this.state.execute(oneStep('Move object', commands));
  }

  /**
   * Lists another holder's objects – the Container tab hands in its template, the Scene tab the
   * active scene again.
   */
  showObjectsOf(source: () => ObjectHolder | undefined): void {
    this.source = source;
    this.refresh();
  }

  /** With the content of placed containers resolved in – the rows show it like any other object. */
  private holder(): ObjectHolder | undefined {
    const holder = this.source();
    return holder && resolvedHolder(this.state.project, holder);
  }

  /** Ids of the rows currently shown – subtrees of collapsed objects are not among them (test hook). */
  rowOrder(): string[] {
    const holder = this.holder();
    return holder ? visibleTreeOrder(holder, this.expanded).map((e) => e.object.id) : [];
  }

  /** Label colour of a row as `#rrggbb` – gold means it or something below it deviates (test hook). */
  rowColor(id: string): string | null {
    return this.list.rowColor(id);
  }

  /** Global centre of a row's chevron, so tests can click the real hit area (test hook). */
  chevronPosition(id: string): { x: number; y: number } | null {
    return this.list.chevronGlobal(id);
  }

  /** Global centre of a row, away from its chevron (test hook). */
  rowPosition(id: string): { x: number; y: number } | null {
    return this.list.rowGlobal(id);
  }

  /** Global centre of the type icon at a row's right edge (test hook). */
  iconPosition(id: string): { x: number; y: number } | null {
    return this.list.iconGlobal(id);
  }

  expandAll(): void {
    for (const object of this.holder()?.objects ?? []) this.expanded.add(object.id);
    this.refresh();
  }

  collapseAll(): void {
    this.expanded.clear();
    // Keep the selected object reachable instead of folding it away under the user's hands.
    this.revealSelection();
    this.refresh();
  }

  private openContextMenu(id: string, x: number, y: number): Menu | undefined {
    const { state } = this;
    const holder = this.holder();
    if (!holder) return undefined;
    const inScene = holder.type === 'scene';
    const object = findObject(holder, id);
    const asset = object && findAsset(state.project, object.assetId);
    // Content of a placed container belongs to its template: values can be changed here, the
    // structure cannot (see `model/instance.ts`).
    const source = this.source();
    const fromTemplate = Boolean(source && isTemplateContent(source, id));
    const instance = Boolean(object && source && isLiveInstance(state.project, source, object));
    // Inside a multi-selection the menu acts on all selected objects.
    const selected = state.selectedObjectIds.includes(id) ? state.selectedObjectIds : [id];
    const many = selected.length > 1;
    const menu = new Menu([
      {
        label: 'Select asset',
        onSelect: () => object && state.select({ kind: 'asset', assetId: object.assetId }),
      },
      {
        // The same as double-clicking the asset in the asset panel: selects it and opens its tab.
        // A kind without an editor of its own would only be selected, so it is offered greyed out.
        label: 'Open asset',
        disabled: !asset || !hasAssetEditor(asset.type),
        onSelect: () => object && state.openAsset(object.assetId),
      },
      {
        label: 'Add collider',
        disabled: !object || !source || many || !canAddCollider(state.project, source, object),
        onSelect: () => addCollider(state, holder.id, id),
      },
      {
        label: 'Add rigidbody',
        disabled: !object || !source || many || !canAddRigidbody(state.project, source, object),
        onSelect: () => addRigidbody(state, holder.id, id),
      },
      {
        label: many ? `Create container from ${selected.length} objects` : 'Create container',
        disabled: !source || selected.some((oid) => isTemplateContent(source, oid)),
        onSelect: () => createContainer(state, holder.id, selected),
      },
      {
        label: 'Unpack container',
        disabled: !instance,
        onSelect: () => state.execute(new UnpackContainerCommand(holder.id, id)),
      },
      {
        label: 'Unparent (move to top level)',
        disabled: !object?.parentId || many || fromTemplate,
        onSelect: () => state.execute(new SetParentCommand(holder.id, id, '')),
      },
      { label: 'Expand all', onSelect: () => this.expandAll() },
      { label: 'Collapse all', onSelect: () => this.collapseAll() },
      {
        label: many
          ? `Remove ${selected.length} objects from ${inScene ? 'scene' : 'container'}`
          : `Remove from ${inScene ? 'scene' : 'container'}`,
        danger: true,
        disabled: !source || selected.some((oid) => isTemplateContent(source, oid)),
        onSelect: () => removeObjects(state, holder.id, selected),
      },
    ]);
    menu.open(x, y);
    return menu;
  }

  private setExpanded(id: string, expand: boolean): void {
    if (expand) this.expanded.add(id);
    else this.expanded.delete(id);
    this.refresh();
  }

  /** Unfolds the ancestors of every selected object. Returns whether that changed anything. */
  private revealSelection(): boolean {
    const holder = this.holder();
    if (!holder) return false;
    let changed = false;
    for (const id of this.state.selectedObjectIds) {
      for (const ancestorId of ancestorIdsOf(holder, id)) {
        if (this.expanded.has(ancestorId)) continue;
        this.expanded.add(ancestorId);
        changed = true;
      }
    }
    return changed;
  }

  private refresh(): void {
    const holder = this.holder();
    this.shownHolderId = holder?.id ?? '';
    const kind = holder?.type === 'container' ? 'Container' : 'Scene';
    this.setTitle(holder ? `${kind}: ${holder.name}` : 'Scene objects');
    // From the stored holder, not the resolved one: what an object follows depends on where it
    // lives, and in a resolved view container content looks stored.
    const source = this.source();
    const marks = source ? deviationMarks(this.state.project, source) : new Set<string>();
    this.list.setItems(
      (holder ? visibleTreeOrder(holder, this.expanded) : []).map(({ object, depth, hasChildren }) => {
        const asset = findAsset(this.state.project, object.assetId);
        return {
          id: object.id,
          label: object.name || asset?.name || '?',
          icon: asset && ASSET_ICON_SVG[asset.type],
          iconAtEnd: true,
          depth,
          expanded: hasChildren ? this.expanded.has(object.id) : undefined,
          overridden: marks.has(object.id),
        };
      }),
    );
    this.syncSelection();
    this.scroll.relayoutContent();
    this.scrollToSelection();
  }

  private syncSelection(): void {
    const s = this.state.selection;
    this.list.select(s?.kind === 'object' ? s.objectId : null, true);
    this.list.highlight(s?.kind === 'object' ? s.objectIds : []);
  }

  /** Keeps the primary selection in view after unfolding brought it back into the list. */
  private scrollToSelection(): void {
    const s = this.state.selection;
    if (s?.kind !== 'object' || !s.objectId) return;
    const index = this.rowOrder().indexOf(s.objectId);
    if (index >= 0) this.scroll.ensureVisible(index * this.list.rowHeight, this.list.rowHeight);
  }
}