import { mkdirSync } from 'node:fs';
import { Simple_KeyValue_Store } from './kv-store.mjs';

mkdirSync('./data', { recursive: true });

const store = new Simple_KeyValue_Store('./data/tasks.ndjson', {
	auto_load: true,
	auto_store: true,
	debounce_flush_timeout: 5000,
});

// ---------------------------------------------------------------------------
// Migration from old flat-key format (task:1, task:2, ...)
// ---------------------------------------------------------------------------

function migrate_if_needed() {
	const old_keys = [];
	for (const [key] of store.data.entries()) {
		if (key.startsWith('task:')) { old_keys.push(key); }
	}
	if (!old_keys.length) { return; }

	console.log(`[storage] Migrating ${old_keys.length} old flat-key entries...`);

	const task_bucket = store.get('task') ?? {};
	let max_id = store.get('meta')?.next_id ?? 0;

	for (const key of old_keys) {
		const entry = store.get(key);
		task_bucket[entry.id] = { ...entry, type: 'task' };
		if (typeof entry.id === 'number' && entry.id > max_id) { max_id = entry.id; }
		store.data.delete(key);
	}

	store.set('task', task_bucket);

	// Absorb old ids.ndjson counter if present
	try {
		const ids_store = new Simple_KeyValue_Store('./data/ids.ndjson', { auto_load: true });
		const old_counter = ids_store.get('seq:task');
		if (old_counter && old_counter > max_id) { max_id = old_counter; }
	} catch {}

	store.set('meta', { ...(store.get('meta') ?? {}), next_id: max_id });
	store.store();
	console.log(`[storage] Migration complete. next_id=${max_id}`);
}

// ---------------------------------------------------------------------------
// Seed default entry types on a fresh store
// ---------------------------------------------------------------------------

function seed_defaults() {
	const now = Date.now();
	store.set('entry_types', {
		task: { id: 'task', title: 'Task', description: 'A unit of work to be completed.', created_at: now, updated_at: now },
		idea: { id: 'idea', title: 'Idea', description: 'A thought, concept, or possibility to explore.', created_at: now, updated_at: now },
		note: { id: 'note', title: 'Note', description: 'A reference, observation, or piece of information.', created_at: now, updated_at: now },
	});
	if (!store.get('task')) { store.set('task', {}); }
	if (!store.get('idea')) { store.set('idea', {}); }
	if (!store.get('note')) { store.set('note', {}); }
	store.store();
}

migrate_if_needed();
if (!store.get('entry_types')) { seed_defaults(); }
if (!store.get('meta')) { store.set('meta', { next_id: 0 }); }

// ---------------------------------------------------------------------------
// ID generation
// ---------------------------------------------------------------------------

export function next_id() {
	const meta = store.get('meta') ?? { next_id: 0 };
	meta.next_id = (meta.next_id ?? 0) + 1;
	store.set('meta', meta);
	return meta.next_id;
}

// ---------------------------------------------------------------------------
// Entry types
// ---------------------------------------------------------------------------

export function list_entry_types() {
	return Object.values(store.get('entry_types') ?? {});
}

export function get_entry_type(id) {
	return (store.get('entry_types') ?? {})[id] ?? null;
}

export function set_entry_type(type) {
	const types = store.get('entry_types') ?? {};
	types[type.id] = type;
	store.set('entry_types', types);
	if (!store.get(type.id)) { store.set(type.id, {}); }
}

export function delete_entry_type(id) {
	const types = store.get('entry_types') ?? {};
	if (!types[id]) { return false; }
	delete types[id];
	store.set('entry_types', types);
	return true;
}

// ---------------------------------------------------------------------------
// Entries
// ---------------------------------------------------------------------------

export function list_entries(type = null) {
	const type_keys = type ? [type] : Object.keys(store.get('entry_types') ?? {});
	const result = [];
	for (const t of type_keys) {
		result.push(...Object.values(store.get(t) ?? {}));
	}
	return result.sort((a, b) => b.created_at - a.created_at);
}

export function get_entry(id) {
	for (const t of Object.keys(store.get('entry_types') ?? {})) {
		const entry = (store.get(t) ?? {})[id];
		if (entry) { return entry; }
	}
	return null;
}

export function set_entry(entry) {
	// Remove from any other bucket in case type changed
	for (const t of Object.keys(store.get('entry_types') ?? {})) {
		if (t === entry.type) { continue; }
		const bucket = store.get(t);
		if (bucket?.[entry.id]) {
			delete bucket[entry.id];
			store.set(t, bucket);
		}
	}
	const bucket = store.get(entry.type) ?? {};
	bucket[entry.id] = entry;
	store.set(entry.type, bucket);
}

export function delete_entry(id) {
	for (const t of Object.keys(store.get('entry_types') ?? {})) {
		const bucket = store.get(t);
		if (bucket?.[id]) {
			delete bucket[id];
			store.set(t, bucket);
			return true;
		}
	}
	return false;
}

export function has_child_entries(parent_id) {
	for (const t of Object.keys(store.get('entry_types') ?? {})) {
		if (Object.values(store.get(t) ?? {}).some(e => e.parent_id === parent_id)) { return true; }
	}
	return false;
}