import {
	type MentionItem, type CreateOption,
	fetchMentionItems, createMentionContext, quoteMention, renderDropdown
} from './mentionCore';
import './mention.css';

export function mention(node: HTMLInputElement | HTMLTextAreaElement) {
	let dropdown: HTMLDivElement | null = null;
	let items: MentionItem[] = [];
	let createOptions: CreateOption[] = [];
	let selectedIndex = 0;
	let mentionStart = -1;
	let mentionMode: '@' | '->' = '@';
	let active = false;
	let suppressInput = false;

	function getQuery(): { query: string; mode: '@' | '->' } | null {
		const pos = node.selectionStart ?? 0;
		const text = node.value;

		if (active && mentionStart >= 0 && mentionStart < pos) {
			const trigger = text[mentionStart] === '@' ? '@' : '->';
			if (trigger !== mentionMode) return null;
			const offset = mentionMode === '->' ? 2 : 1;
			return { query: text.slice(mentionStart + offset, pos), mode: mentionMode };
		}

		for (let i = pos - 1; i >= 0; i--) {
			const ch = text[i];
			if (ch === '@') {
				if (i === 0 || /\s/.test(text[i - 1])) {
					mentionStart = i;
					mentionMode = '@';
					return { query: text.slice(i + 1, pos), mode: '@' };
				}
				return null;
			}
			// Check for -> trigger: '>' at position i, '-' at i-1.
			// Allow a single optional space between -> and the query (e.g. "-> ANDST").
			if (ch === '>' && i > 0 && text[i - 1] === '-') {
				if (i - 1 === 0 || /[\s\n]/.test(text[i - 2])) {
					mentionStart = i - 1;
					mentionMode = '->';
					return { query: text.slice(i + 1, pos).trimStart(), mode: '->' };
				}
				return null;
			}
			// Allow spaces only when we haven't yet passed a non-word char other than space
			// (needed for "-> ANDST" where the space is between trigger and query).
			// For @-mentions, spaces are not allowed in the query (quoted names use autocomplete).
			if (/\s/.test(ch)) return null;
		}
		return null;
	}

	function totalCount(): number {
		return items.length + createOptions.length;
	}

	function show() {
		if (!dropdown) {
			dropdown = document.createElement('div');
			dropdown.className = 'mention-dropdown';
			node.parentElement!.style.position = 'relative';
			node.parentElement!.appendChild(dropdown);
		}
		active = true;
		render();
	}

	function hide() {
		if (dropdown) {
			dropdown.remove();
			dropdown = null;
		}
		active = false;
		items = [];
		createOptions = [];
		mentionStart = -1;
	}

	function render() {
		if (!dropdown) return;
		if (totalCount() === 0) { hide(); return; }
		renderDropdown(dropdown, items, createOptions, selectedIndex, selectItem, (i) => {
			selectedIndex = i;
			render();
		});
	}

	function insertTextAt(from: number, to: number, text: string) {
		const before = node.value.slice(0, from);
		const after = node.value.slice(to);
		node.value = before + text + ' ' + after;
		const newPos = from + text.length + 1;
		node.selectionStart = newPos;
		node.selectionEnd = newPos;
		node.dispatchEvent(new Event('input', { bubbles: true }));
	}

	async function selectItem(index: number) {
		// Save positions before any async work (hide/blur could reset mentionStart)
		const savedFrom = mentionStart;
		const savedTo = node.selectionStart ?? node.value.length;
		console.log('[mention-action] selectItem', index, 'items:', items.length, 'create:', createOptions.length, 'from:', savedFrom, 'to:', savedTo);
		suppressInput = true;
		try {
			if (index < items.length) {
				const text = items[index].insertText;
				console.log('[mention-action] inserting:', text);
				insertTextAt(savedFrom, savedTo, text);
				console.log('[mention-action] after insert, value:', JSON.stringify(node.value));
			} else {
				const opt = createOptions[index - items.length];
				if (!opt) return;
				await createMentionContext(opt);
				const tag = opt.type === 'company' ? quoteMention('@F:', opt.query) : opt.type === 'person' ? quoteMention('@', opt.query) : quoteMention('@P:', opt.query);
				console.log('[mention-action] inserting after create:', tag);
				insertTextAt(savedFrom, savedTo, tag);
				console.log('[mention-action] after create insert, value:', JSON.stringify(node.value));
			}
		} catch (err) {
			console.error('mention selectItem error:', err);
		} finally {
			hide();
			suppressInput = false;
		}
	}

	async function handleInput() {
		if (suppressInput) return;
		const qResult = getQuery();
		if (qResult === null) {
			if (active) hide();
			return;
		}
		const result = await fetchMentionItems(qResult.query, qResult.mode);

		// Re-check after async: state may have changed (e.g. selectItem ran)
		if (suppressInput) return;
		const qResultNow = getQuery();
		if (qResultNow === null) {
			if (active) hide();
			return;
		}

		items = result.items;
		createOptions = result.createOptions;
		selectedIndex = 0;
		if (totalCount() > 0) {
			show();
		} else {
			hide();
		}
	}

	function handleKeydown(e: KeyboardEvent) {
		if (!active) return;
		const count = totalCount();

		if (e.key === 'ArrowDown') {
			e.preventDefault();
			selectedIndex = (selectedIndex + 1) % count;
			render();
		} else if (e.key === 'ArrowUp') {
			e.preventDefault();
			selectedIndex = (selectedIndex - 1 + count) % count;
			render();
		} else if (e.key === 'Enter') {
			e.preventDefault();
			selectItem(selectedIndex);
		} else if (e.key === 'Escape') {
			e.preventDefault();
			hide();
		}
	}

	function handleBlur() {
		if (suppressInput) return;
		setTimeout(hide, 150);
	}

	node.addEventListener('input', handleInput);
	node.addEventListener('keydown', handleKeydown as EventListener);
	node.addEventListener('blur', handleBlur);

	return {
		destroy() {
			node.removeEventListener('input', handleInput);
			node.removeEventListener('keydown', handleKeydown as EventListener);
			node.removeEventListener('blur', handleBlur);
			hide();
		}
	};
}