/** 명령행 — AutoCAD 명령행처럼 기록·입력·자동완성을 담당한다. */
import { type FC, type FormEvent, useMemo, useRef, useState } from 'react';
import { describeCommand, matchCommandPrefixes } from '../commands/registry';
import { getCommandHistory, runCommandInput } from '../commands/run-command';
import { getInputController, getLastStateInstructions } from '../state';

export const CommandLine: FC = () => {
	const [text, setText] = useState('');
	const [historyIndex, setHistoryIndex] = useState<number | null>(null);
	const inputRef = useRef<HTMLInputElement>(null);
	const history = getCommandHistory();
	const instruction = getLastStateInstructions() || '명령을 입력하거나 도구를 선택하십시오.';

	const suggestions = useMemo(() => matchCommandPrefixes(text).slice(0, 8), [text]);

	const submit = (event: FormEvent) => {
		event.preventDefault();
		const value = text.trim();
		if (!value) {
			// 빈 ENTER는 활성 명령의 확정 신호다 (선택 끝내기·직전 명령 반복)
			getInputController().handleEnterKey();
			return;
		}
		// 진행 중인 명령이 문자·숫자를 기다리면 그쪽으로, 아니면 명령으로 해석된다
		getInputController().submitText(value);
		setText('');
		setHistoryIndex(null);
	};

	const recallHistory = (direction: -1 | 1) => {
		if (!history.length) return;
		const nextIndex =
			historyIndex === null
				? history.length - 1
				: Math.min(history.length - 1, Math.max(0, historyIndex + direction));
		setHistoryIndex(nextIndex);
		setText(history[nextIndex].split(' ')[0]);
	};

	return (
		<section className="cad-command-area controls">
			<div className="cad-command-history">
				{history.slice(-3).map((line, index) => (
					// biome-ignore lint/suspicious/noArrayIndexKey: 기록은 순서 자체가 식별자다
					<span key={`${line}-${index}`}>{line}</span>
				))}
			</div>
			<form onSubmit={submit}>
				<label htmlFor="cad-command">명령:</label>
				<input
					id="cad-command"
					ref={inputRef}
					value={text}
					onChange={(event) => setText(event.target.value)}
					onKeyDown={(event) => {
						if (event.nativeEvent.isComposing) return; // 한글 조합 중 키는 IME 몫
						if (event.key === 'Escape') {
							event.preventDefault();
							getInputController().handleEscapeKey();
						}
						if (event.key === 'ArrowUp') {
							event.preventDefault();
							recallHistory(-1);
						}
						if (event.key === 'ArrowDown') {
							event.preventDefault();
							recallHistory(1);
						}
						if (event.key === 'Tab' && suggestions.length) {
							event.preventDefault();
							setText(suggestions[0].id);
						}
					}}
					placeholder="명령 입력 (예: L, LINE, REC, MOVE)"
					autoComplete="off"
					spellCheck={false}
				/>
				<span className="cad-command-prompt">{instruction}</span>
			</form>
			{text.trim() && suggestions.length > 0 && (
				<div className="cad-command-suggestions">
					{suggestions.map((command) => (
						<button
							type="button"
							key={command.id}
							onClick={() => {
								runCommandInput(command.id);
								setText('');
								inputRef.current?.focus();
							}}
						>
							{describeCommand(command)}
						</button>
					))}
				</div>
			)}
		</section>
	);
};