import { EditorView, Decoration, DecorationSet, ViewPlugin, ViewUpdate } from '@codemirror/view';
import { RangeSetBuilder, Extension } from '@codemirror/state';

export const timestampChipClassName = 'cm-ext-timestamp-chip';

/**
 * 格式化当前时间为 HH:mm（如 16:30）
 */
export const getFormattedCurrentTime = (date = new Date()): string => {
	const hours = date.getHours().toString().padStart(2, '0');
	const minutes = date.getMinutes().toString().padStart(2, '0');
	return `${hours}:${minutes}`;
};

/**
 * 检测光标前是否为 /now 或 /time 关键词，若是则瞬时展开为时间戳
 */
export const tryExpandQuickTimestamp = (
	view: EditorView,
	from: number,
	to: number,
	triggerChar: string,
): boolean => {
	if (view.composing || view.state.readOnly) return false;

	const doc = view.state.doc;
	const line = doc.lineAt(from);
	const lineTextBefore = doc.sliceString(line.from, from);

	let matchLength = 0;
	if (lineTextBefore.endsWith('/now')) {
		matchLength = 4;
	} else if (lineTextBefore.endsWith('/time')) {
		matchLength = 5;
	}

	if (matchLength === 0) return false;

	const matchFrom = from - matchLength;
	const timeStr = getFormattedCurrentTime();
	const replacement = `[${timeStr}]${triggerChar}`;

	view.dispatch({
		changes: { from: matchFrom, to, insert: replacement },
		selection: { anchor: matchFrom + replacement.length },
		userEvent: 'input.quickTimestamp',
	});

	return true;
};

const timestampDeco = Decoration.mark({ class: timestampChipClassName });

const buildTimestampDecorations = (view: EditorView): DecorationSet => {
	const builder = new RangeSetBuilder<Decoration>();
	const TIMESTAMP_REGEX = /\[\d{1,2}:\d{2}\]/g;

	for (const { from, to } of view.visibleRanges) {
		const text = view.state.doc.sliceString(from, to);
		TIMESTAMP_REGEX.lastIndex = 0;
		let match: RegExpExecArray | null;
		while ((match = TIMESTAMP_REGEX.exec(text)) !== null) {
			const start = from + match.index;
			const end = start + match[0].length;
			builder.add(start, end, timestampDeco);
		}
	}

	return builder.finish();
};

const timestampChipPlugin = ViewPlugin.fromClass(
	class {
		public decorations: DecorationSet;
		public constructor(view: EditorView) {
			this.decorations = buildTimestampDecorations(view);
		}
		public update(update: ViewUpdate) {
			if (update.docChanged || update.viewportChanged) {
				this.decorations = buildTimestampDecorations(update.view);
			}
		}
	},
	{
		decorations: v => v.decorations,
	},
);

const quickTimestampExtension = (): Extension => [
	EditorView.theme({
		[`& .${timestampChipClassName}`]: {
			fontVariantNumeric: 'tabular-nums',
			backgroundColor: 'var(--joplin-background-color-hover3, rgba(0, 0, 0, 0.06))',
			color: 'var(--joplin-color-accent, #007aff)',
			fontSize: '0.88em',
			fontWeight: '600',
			padding: '1px 6px',
			borderRadius: '4px',
			marginRight: '3px',
			letterSpacing: '0.02em',
			display: 'inline-block',
			verticalAlign: 'baseline',
		},
	}),
	EditorView.inputHandler.of((view, from, to, text) => {
		if (text === ' ' || text === '\t' || text === '\n') {
			if (tryExpandQuickTimestamp(view, from, to, text)) {
				return true;
			}
		}
		return false;
	}),
	timestampChipPlugin,
];

export default quickTimestampExtension;