import { CLI_FLAGS } from '$lib/constants';
import { ToolSource } from '$lib/enums';
import { conversationsStore, mcpStore, toolsStore } from '$lib/stores';
import type { ToolGroup } from '$lib/types';
import { SvelteSet } from 'svelte/reactivity';

export interface UseToolsPanelReturn {
	readonly expandedGroups: SvelteSet<string>;
	readonly groups: ToolGroup[];
	readonly activeGroups: ToolGroup[];
	readonly totalToolCount: number;
	readonly noToolsInfoMessage: string | null;
	isGroupChecked(group: ToolGroup): boolean;
	getEnabledToolCount(group: ToolGroup): number;
	getFavicon(group: ToolGroup): string | null;
	isGroupDisabled(group: ToolGroup): boolean;
	toggleGroupExpanded(key: string): void;
	/** Toggle all tools in a group by its stable key (avoids stale group object references). */
	toggleGroupByKey(key: string): void;
	handleOpen(): void;
}

/**
 * Shared reactive state and helpers for the tools panel UI.
 *
 * Used by both the desktop dropdown (`ChatFormActionAddToolsSubmenu`)
 * and the mobile sheet (`ChatFormActionAddSheet`) to avoid
 * duplicating group filtering, checked-state derivation, and favicon logic.
 */
export function useToolsPanel(): UseToolsPanelReturn {
	const expandedGroups = new SvelteSet<string>();
	const groups = $derived(toolsStore.toolGroups);
	const activeGroups = $derived(
		groups.filter(
			(g) =>
				g.source !== ToolSource.MCP ||
				!g.serverId ||
				conversationsStore.isMcpServerEnabledForChat(g.serverId)
		)
	);
	const totalToolCount = $derived(activeGroups.reduce((n, g) => n + g.tools.length, 0));
	const noToolsInfoMessage = $derived.by(() => {
		if (toolsStore.loading) return null;

		if (toolsStore.toolGroups.length > 0) return null;

		// Tools endpoint is unreachable (404) — server started without --tools
		if (toolsStore.isToolsEndpointUnreachable) {
			return `To enable Built-In Tools you need to run llama-server with ${CLI_FLAGS.TOOLS} all or ${CLI_FLAGS.TOOLS} <name> flag. To see MCP Tools you need to add / enable MCP Server(s).`;
		}

		// Other errors — return null so UI shows "Failed to load tools"
		if (toolsStore.error) return null;

		return `To enable Built-In Tools you need to run llama-server with ${CLI_FLAGS.TOOLS} all or ${CLI_FLAGS.TOOLS} <name> flag. To see MCP Tools you need to add / enable MCP Server(s).`;
	});

	function isGroupChecked(group: ToolGroup): boolean {
		return toolsStore.isGroupFullyEnabled(group);
	}

	function getEnabledToolCount(group: ToolGroup): number {
		return group.tools.filter((tool) => toolsStore.isToolEnabled(tool.key)).length;
	}

	function getFavicon(group: ToolGroup): string | null {
		if (group.source !== ToolSource.MCP || !group.serverId) return null;

		return mcpStore.getServerFavicon(group.serverId);
	}

	function isGroupDisabled(group: ToolGroup): boolean {
		return (
			group.source === ToolSource.MCP &&
			!!group.serverId &&
			!conversationsStore.isMcpServerEnabledForChat(group.serverId)
		);
	}

	function toggleGroupExpanded(key: string): void {
		if (expandedGroups.has(key)) {
			expandedGroups.delete(key);
		} else {
			expandedGroups.add(key);
		}
	}

	function toggleGroupByKey(key: string): void {
		// Find current group by key to get up-to-date tool references
		const group = activeGroups.find((g) => g.key === key);

		if (!group) return;

		toolsStore.toggleGroup(group);
	}

	function handleOpen(): void {
		if (toolsStore.builtinTools.length === 0 && !toolsStore.loading) {
			toolsStore.fetchBuiltinTools();
		}

		mcpStore.runHealthChecksForServers(mcpStore.getServers().filter((s) => s.enabled));
	}

	return {
		get activeGroups() {
			return activeGroups;
		},
		expandedGroups,
		getEnabledToolCount,
		getFavicon,
		get groups() {
			return groups;
		},
		handleOpen,
		isGroupChecked,
		isGroupDisabled,
		get noToolsInfoMessage() {
			return noToolsInfoMessage;
		},
		toggleGroupByKey,
		toggleGroupExpanded,
		get totalToolCount() {
			return totalToolCount;
		}
	};
}