// The documentation mode's sidebar (Java's GUIDocumentationSidebar): „Text“
// and „Gliederungsfläche“ with Java's icons. An item is dragged onto the
// surface, where it lands with its middle under the pointer, as Java's does;
// tapped, it lands in the middle of the view (Java's tap makes nothing).
// „Exportieren“ saves the surface as an image (F4.8c); if that fails, Java's
// „Fehler beim Speichern aufgetreten!“ shows below it.

import { useRef, useState, type CSSProperties } from 'react';
import type { DocumentationItemKind } from '@mdg-filius/core';
import { DRAG_THRESHOLD } from '../canvas/Canvas.js';
import { useTranslate } from '../i18n/i18n.js';
import addRectangle from '../assets/documentation/add_small.png';
import addText from '../assets/documentation/add_text_small.png';
import exportIcon from '../assets/documentation/download_small.png';

export interface DocumentationSidebarProps {
  /** An item dropped at a point of the screen, or tapped (no point). */
  readonly onItem: (kind: DocumentationItemKind, at: { readonly clientX: number; readonly clientY: number } | null) => void;
  /** „Exportieren“: the surface saved as an image; rejected, it failed. */
  readonly onExport: () => Promise<void>;
}

const ITEMS: readonly { readonly kind: DocumentationItemKind; readonly icon: string; readonly label: string }[] = [
  { kind: 'text', icon: addText, label: 'docu.text' },
  { kind: 'rectangle', icon: addRectangle, label: 'docu.rectangle' },
];

const item: CSSProperties = {
  display: 'flex',
  flexDirection: 'column',
  alignItems: 'center',
  gap: 2,
  minHeight: 64,
  padding: '6px 4px',
  border: '2px solid transparent',
  borderRadius: 8,
  background: 'transparent',
  color: 'var(--text-primary)',
  font: 'inherit',
  fontSize: 12,
  textAlign: 'center',
  overflowWrap: 'anywhere',
  cursor: 'grab',
  touchAction: 'none',
};

export function DocumentationSidebar({ onItem, onExport }: DocumentationSidebarProps) {
  const t = useTranslate();
  const [ghost, setGhost] = useState<{ kind: DocumentationItemKind; x: number; y: number } | null>(null);
  const press = useRef<{ kind: DocumentationItemKind; x: number; y: number; dragging: boolean } | null>(null);
  /** The click the browser sends after a drag ends on the button: not a tap. */
  const afterDrag = useRef(false);
  const [exporting, setExporting] = useState(false);
  const [failed, setFailed] = useState(false);
  const exportImage = () => {
    setExporting(true);
    setFailed(false);
    onExport().then(
      () => setExporting(false),
      () => {
        setExporting(false);
        setFailed(true);
      },
    );
  };

  const onPointerDown = (kind: DocumentationItemKind) => (event: React.PointerEvent<HTMLButtonElement>) => {
    press.current = { kind, x: event.clientX, y: event.clientY, dragging: false };
    // The button is the click's own target: capturing at once takes no click from anything inside it.
    event.currentTarget.setPointerCapture(event.pointerId);
  };
  const onPointerMove = (event: React.PointerEvent<HTMLButtonElement>) => {
    const now = press.current;
    if (now === null) return;
    if (!now.dragging) {
      if (Math.hypot(event.clientX - now.x, event.clientY - now.y) < DRAG_THRESHOLD) return;
      now.dragging = true;
    }
    setGhost({ kind: now.kind, x: event.clientX, y: event.clientY });
  };
  const onPointerUp = (event: React.PointerEvent<HTMLButtonElement>) => {
    const now = press.current;
    press.current = null;
    setGhost(null);
    if (now?.dragging !== true) return;
    afterDrag.current = true;
    onItem(now.kind, { clientX: event.clientX, clientY: event.clientY });
  };

  return (
    <nav
      aria-label={t('docu.sidebar')}
      style={{
        display: 'flex',
        flexDirection: 'column',
        gap: 4,
        padding: 6,
        overflowY: 'auto',
        background: 'var(--surface-card)',
        borderRight: '1px solid var(--border-default)',
        width: 124,
        flexShrink: 0,
      }}
    >
      {ITEMS.map((each) => (
        <button
          key={each.kind}
          type="button"
          style={item}
          data-docu={each.kind}
          onPointerDown={onPointerDown(each.kind)}
          onPointerMove={onPointerMove}
          onPointerUp={onPointerUp}
          onPointerCancel={() => {
            press.current = null;
            setGhost(null);
          }}
          onClick={() => {
            if (afterDrag.current) afterDrag.current = false;
            else onItem(each.kind, null);
          }}
        >
          <img src={each.icon} alt="" width={40} height={40} draggable={false} />
          {t(each.label)}
        </button>
      ))}
      <button type="button" style={{ ...item, cursor: exporting ? 'progress' : 'pointer' }} title={t('docu.exportHint')} disabled={exporting} onClick={exportImage}>
        <img src={exportIcon} alt="" width={40} height={40} draggable={false} />
        {t('docu.export')}
      </button>
      {failed ? (
        <p role="alert" style={{ margin: 0, fontSize: 12, color: 'var(--danger)' }}>
          {t('docu.saveFailed')}
        </p>
      ) : null}
      {ghost === null ? null : (
        // The item's own size, its middle under the pointer, as Java drags it.
        <div
          data-ghost
          style={{
            position: 'fixed',
            left: ghost.x,
            top: ghost.y,
            width: 100,
            height: 50,
            transform: 'translate(-50%, -50%)',
            border: `1px ${ghost.kind === 'text' ? 'solid rgb(179, 179, 179)' : 'solid rgb(163, 163, 163)'}`,
            borderRadius: 5,
            background: ghost.kind === 'rectangle' ? 'rgba(204, 204, 204, 0.78)' : 'transparent',
            pointerEvents: 'none',
            zIndex: 10,
          }}
        />
      )}
    </nav>
  );
}