import { type FederatedPointerEvent, Graphics, Text, CanvasTextMetrics } from 'pixi.js';
import { drawControlBox } from '../draw';
import { centreY } from '../math';
import { Theme, textStyle } from '../Theme';
import { type Size, Widget } from '../Widget';

export interface ButtonOptions {
  /** Visual weight: 'primary' uses the accent color, 'ghost' has no background until hovered. */
  variant?: 'default' | 'primary' | 'ghost' | 'danger';
  /** Fixed width; otherwise measured from the label. */
  width?: number;
  /**
   * Label position in a button wider than its text. 'center' suits standalone buttons,
   * 'left' the ones that read as a list or a field (menu entries, dropdowns).
   */
  align?: 'center' | 'left';
  onClick?: () => void;
}

/** Push button; Enter/Space activate it while focused. Clicks fire only for the primary pointer button. */
export class Button extends Widget {
  private readonly bg = new Graphics();
  private readonly labelText: Text;
  private pressed = false;
  /** Caller-owned toggle state: renders like a primary button but is not flipped by clicks. */
  toggled = false;
  variant: NonNullable<ButtonOptions['variant']>;
  protected readonly align: NonNullable<ButtonOptions['align']>;
  onClick?: () => void;

  constructor(text: string, options: ButtonOptions = {}) {
    super();
    this.variant = options.variant ?? 'default';
    this.align = options.align ?? 'center';
    this.onClick = options.onClick;
    this.focusable = true;
    this.cursor = 'pointer';
    this.minHeight = Theme.controlHeight;
    if (options.width) this.minWidth = options.width;
    this.labelText = new Text({ text, style: textStyle(this.variant === 'primary' ? 'accent' : 'body') });
    this.addChild(this.bg, this.labelText);

    // Leaving while pressed cancels the click: a release elsewhere must not activate.
    this.trackHover(() => {
      this.pressed = false;
    });
    this.on('pointerdown', (e: FederatedPointerEvent) => {
      if (e.button !== 0) return;
      this.pressed = true;
      this.invalidate();
    });
    this.on('pointerup', (e: FederatedPointerEvent) => {
      if (e.button !== 0 || !this.pressed) return;
      this.pressed = false;
      this.invalidate();
      this.onClick?.();
    });
    this.on('pointerupoutside', () => {
      this.pressed = false;
      this.invalidate();
    });
  }

  get text(): string {
    return this.labelText.text;
  }

  /** Repaints only; the parent must relayout when the measured width matters. */
  setText(text: string): void {
    this.labelText.text = text;
    this.invalidate();
  }

  setToggled(toggled: boolean): void {
    if (this.toggled === toggled) return;
    this.toggled = toggled;
    this.invalidate();
  }

  /** Whether the label sits on a filled accent surface and therefore needs the light style. */
  protected get onAccent(): boolean {
    return this.toggled || this.variant === 'primary' || this.variant === 'danger';
  }

  override measure(): Size {
    const metrics = CanvasTextMetrics.measureText(this.labelText.text, this.labelText.style);
    return {
      w: Math.max(this.minWidth, Math.ceil(metrics.width) + Theme.padding * 2),
      h: Math.max(this.minHeight, Theme.controlHeight),
    };
  }

  override onKeyDown(event: KeyboardEvent): boolean {
    if (event.key === 'Enter' || event.key === ' ') {
      this.onClick?.();
      return true;
    }
    return false;
  }

  override redraw(): void {
    const c = Theme.colors;
    const flat = this.variant === 'default' || this.variant === 'ghost';
    let fill: number | null = c.control;
    let border: number | null = c.border;
    if (this.variant === 'primary') {
      fill = c.accent;
      border = null;
    }
    if (this.variant === 'danger') {
      fill = c.danger;
      border = null;
    }
    if (this.variant === 'ghost') {
      fill = null;
      border = null;
    }
    if (this.toggled) {
      fill = c.accent;
      border = null;
    }
    if (this.hovered && !this.toggled && flat) fill = c.controlHover;
    if (this.pressed && flat) fill = c.controlActive;
    const stroke = this.focused ? c.accent : border;

    this.bg.clear();
    if (fill !== null && stroke !== null) {
      drawControlBox(this.bg, this.w, this.h, { fill, border: stroke });
    } else if (fill !== null) {
      this.bg.roundRect(0, 0, this.w, this.h, Theme.radius).fill(fill);
    } else if (stroke !== null) {
      this.bg.roundRect(0.5, 0.5, this.w - 1, this.h - 1, Theme.radius).stroke({ width: 1, color: stroke });
    }
    this.labelText.style = textStyle(this.onAccent ? 'accent' : 'body');
    const label = this.labelText;
    const x = this.align === 'left' ? Theme.padding : (this.w - label.width) / 2;
    label.position.set(Math.round(x), centreY(this.h, label.height));
  }
}