import { syntaxTree } from '@codemirror/language';
import { Extension, Range } from '@codemirror/state';
import {
	DecorationSet,
	Decoration,
	WidgetType,
	EditorView,
	ViewPlugin,
	ViewUpdate,
	hoverTooltip,
	Tooltip
} from '@codemirror/view';

interface ImageInfo {
	src: string;
	from: number;
	to: number;
	alt: string;
}

const IMAGE_EXT_RE = /\.(png|jpe?g|gif|webp|svg|bmp|ico|avif|apng|tiff?)(\?.*)?$/i;
const IMAGE_ALT_RE = /(?:!\[)(.*?)(?:\])/;
const ICON = `<svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="3" y="3" width="18" height="18" rx="2" ry="2"/><circle cx="8.5" cy="8.5" r="1.5"/><polyline points="21 15 16 10 5 21"/></svg>`;

function isImageUrl(url: string): boolean {
	return IMAGE_EXT_RE.test(url) || url.startsWith('data:image/');
}

function extractImages(view: EditorView): ImageInfo[] {
	const result: ImageInfo[] = [];
	for (const { from, to } of view.visibleRanges) {
		syntaxTree(view.state).iterate({
			from,
			to,
			enter: ({ name, node, from: f, to: t }) => {
				if (name !== 'Image') return;
				const urlNode = node.getChild('URL');
				if (!urlNode) return;
				const src = view.state.sliceDoc(urlNode.from, urlNode.to);
				if (!isImageUrl(src)) return;
				const text = view.state.sliceDoc(f, t);
				const alt = text.match(IMAGE_ALT_RE)?.[1] ?? '';
				result.push({ src, from: f, to: t, alt });
			}
		});
	}
	return result;
}

class IndicatorWidget extends WidgetType {
	constructor(readonly info: ImageInfo) {
		super();
	}

	toDOM(): HTMLElement {
		const el = document.createElement('span');
		el.className = 'cm-image-indicator';
		el.innerHTML = ICON;
		return el;
	}

	eq(other: IndicatorWidget): boolean {
		return this.info.from === other.info.from && this.info.src === other.info.src;
	}
}

class ImagePlugin {
	decorations: DecorationSet;
	images: ImageInfo[] = [];

	constructor(view: EditorView) {
		this.images = extractImages(view);
		this.decorations = this.build();
	}

	update(update: ViewUpdate) {
		if (update.docChanged || update.viewportChanged) {
			this.images = extractImages(update.view);
			this.decorations = this.build();
		}
	}

	private build(): DecorationSet {
		const deco: Range<Decoration>[] = [];
		for (const img of this.images) {
			deco.push(Decoration.widget({ widget: new IndicatorWidget(img), side: 1 }).range(img.to));
		}
		return Decoration.set(deco, true);
	}

	getImageAt(pos: number): ImageInfo | null {
		for (const img of this.images) {
			if (pos >= img.to && pos <= img.to + 1) {
				return img;
			}
		}
		return null;
	}
}

const imagePlugin = ViewPlugin.fromClass(ImagePlugin, {
	decorations: (v) => v.decorations
});

const imageHoverTooltip = hoverTooltip(
	(view, pos): Tooltip | null => {
		const plugin = view.plugin(imagePlugin);
		if (!plugin) return null;

		const img = plugin.getImageAt(pos);
		if (!img) return null;

		return {
			pos: img.to,
			above: true,
			arrow: true,
			create: () => {
				const dom = document.createElement('div');
				dom.className = 'cm-image-tooltip';

				const imgEl = document.createElement('img');
				imgEl.src = img.src;
				imgEl.alt = img.alt;

				imgEl.onerror = () => {
					imgEl.remove();
					dom.textContent = 'Failed to load image';
					dom.classList.add('cm-image-tooltip-error');
				};

				dom.append(imgEl);
				return { dom };
			}
		};
	},
	{ hoverTime: 300 }
);

const theme = EditorView.baseTheme({
	'.cm-image-indicator': {
		display: 'inline-flex',
		alignItems: 'center',
		marginLeft: '4px',
		verticalAlign: 'middle',
		cursor: 'pointer',
		opacity: '0.5',
		color: 'var(--cm-link-color, #1a73e8)',
		transition: 'opacity 0.15s',
		'& svg': { width: '14px', height: '14px' }
	},
	'.cm-image-indicator:hover': { opacity: '1' },
	'.cm-image-tooltip': {
		background: 'var(--bg-secondary)',
		border: '1px solid var(--border-color)',
		boxShadow: '0 4px 12px rgba(0, 0, 0, 0.15)',
		'& img': {
			display: 'block',
			maxWidth: '60vw',
			maxHeight: '50vh'
		}
	},
	'.cm-image-tooltip-error': {
		padding: '16px 24px',
		fontSize: '12px',
		color: 'var(--text-muted)'
	},
	'.cm-tooltip-arrow:before': {
		borderTopColor: 'var(--border-color) !important',
		borderBottomColor: 'var(--border-color) !important'
	},
	'.cm-tooltip-arrow:after': {
		borderTopColor: 'var(--bg-secondary) !important',
		borderBottomColor: 'var(--bg-secondary) !important'
	}
});

export const image = (): Extension => [imagePlugin, imageHoverTooltip, theme];