import {
  Component,
  ElementRef,
  HostListener,
  computed,
  inject,
  input,
  output,
  viewChild
} from '@angular/core';
import { CommonModule } from '@angular/common';

import {
  ThemeGridEditorItem,
  ThemeGridRect,
  ThemeLayoutContainerDefinition
} from '../../domain/theme.models';

type DragMode = 'move' | 'resize';

interface DragState {
  key: string;
  mode: DragMode;
  startClientX: number;
  startClientY: number;
  startGrid: ThemeGridRect;
}

@Component({
  selector: 'app-theme-grid-editor',
  standalone: true,
  imports: [CommonModule],
  templateUrl: './theme-grid-editor.component.html',
  styleUrl: './theme-grid-editor.component.scss'
})
export class ThemeGridEditorComponent {
  readonly container = input.required<ThemeLayoutContainerDefinition>();
  readonly items = input.required<ThemeGridEditorItem[]>();
  readonly selectedKey = input<string | null>(null);
  readonly disabled = input(false);

  readonly itemChanged = output<{ key: string; grid: ThemeGridRect }>();
  readonly itemSelected = output<string>();

  private readonly host = inject<ElementRef<HTMLElement>>(ElementRef);
  private dragState: DragState | null = null;

  readonly canvasRef = viewChild.required<ElementRef<HTMLElement>>('canvasRef');
  readonly frameStyle = computed(() => ({
    '--theme-grid-columns': `${this.container().columns}`,
    '--theme-grid-rows': `${this.container().rows}`
  }));

  itemStyle(item: ThemeGridEditorItem): Record<string, string> {
    const { columns, rows } = this.container();

    return {
      left: `${(item.grid.x / columns) * 100}%`,
      top: `${(item.grid.y / rows) * 100}%`,
      width: `${(item.grid.w / columns) * 100}%`,
      height: `${(item.grid.h / rows) * 100}%`
    };
  }

  selectItem(key: string): void {
    this.itemSelected.emit(key);
  }

  startMove(event: PointerEvent, item: ThemeGridEditorItem): void {
    this.startDrag(event, item, 'move');
  }

  startResize(event: PointerEvent, item: ThemeGridEditorItem): void {
    this.startDrag(event, item, 'resize');
  }

  @HostListener('document:pointermove', ['$event'])
  onPointerMove(event: PointerEvent): void {
    if (!this.dragState || this.disabled()) {
      return;
    }

    const canvasRect = this.canvasRef().nativeElement.getBoundingClientRect();
    const columnWidth = canvasRect.width / this.container().columns;
    const rowHeight = canvasRect.height / this.container().rows;
    const deltaColumns = Math.round((event.clientX - this.dragState.startClientX) / columnWidth);
    const deltaRows = Math.round((event.clientY - this.dragState.startClientY) / rowHeight);
    const nextGrid = { ...this.dragState.startGrid };

    if (this.dragState.mode === 'move') {
      nextGrid.x = this.clamp(deltaColumns + this.dragState.startGrid.x, 0, this.container().columns - nextGrid.w);
      nextGrid.y = this.clamp(deltaRows + this.dragState.startGrid.y, 0, this.container().rows - nextGrid.h);
    } else {
      nextGrid.w = this.clamp(deltaColumns + this.dragState.startGrid.w, 1, this.container().columns - nextGrid.x);
      nextGrid.h = this.clamp(deltaRows + this.dragState.startGrid.h, 1, this.container().rows - nextGrid.y);
    }

    this.itemChanged.emit({
      key: this.dragState.key,
      grid: nextGrid
    });
  }

  @HostListener('document:pointerup')
  @HostListener('document:pointercancel')
  onPointerUp(): void {
    this.dragState = null;
  }

  @HostListener('document:keydown.escape')
  onEscape(): void {
    this.dragState = null;
  }

  private startDrag(event: PointerEvent, item: ThemeGridEditorItem, mode: DragMode): void {
    if (this.disabled()) {
      return;
    }

    event.preventDefault();
    event.stopPropagation();
    this.itemSelected.emit(item.key);
    this.dragState = {
      key: item.key,
      mode,
      startClientX: event.clientX,
      startClientY: event.clientY,
      startGrid: { ...item.grid }
    };
  }

  private clamp(value: number, minimum: number, maximum: number): number {
    return Math.min(Math.max(value, minimum), maximum);
  }
}