// ─────────────────────────────────────────────────────────────────────────────
// services/presetLoader.ts – Reads + deep-merges preset files with caching
// ─────────────────────────────────────────────────────────────────────────────
import fs from "fs/promises";
import path from "path";
import deepmerge from "deepmerge";
import { PRESETS_DIR, MANIFEST_FILE, TOKENS_FILE } from "../constants.js";
import type { Preset, PresetManifest, DesignTokens, ComponentTemplate, LayoutTemplate } from "../types/index.js";
// ── In-memory cache ───────────────────────────────────────────────────────────
const cache = new Map<string, Preset>();
export function invalidateCache(presetId: string): void {
cache.delete(presetId);
}
// ── Main loader ───────────────────────────────────────────────────────────────
export async function loadPreset(
presetId: string,
_visitedIds: ReadonlySet<string> = new Set()
): Promise<Preset> {
if (cache.has(presetId)) {
return cache.get(presetId)!;
}
const preset = await readPresetFromDisk(presetId, _visitedIds);
cache.set(presetId, preset);
return preset;
}
export async function listAvailablePresets(): Promise<string[]> {
try {
const entries = await fs.readdir(PRESETS_DIR, { withFileTypes: true });
return entries
.filter((e) => e.isDirectory())
.map((e) => e.name)
.sort();
} catch {
return [];
}
}
// ── Disk reader ───────────────────────────────────────────────────────────────
async function readPresetFromDisk(
presetId: string,
visitedIds: ReadonlySet<string> = new Set()
): Promise<Preset> {
const presetsRoot = path.resolve(PRESETS_DIR);
const presetDir = path.resolve(presetsRoot, presetId);
// Ensure the resolved preset directory is within the presets root to prevent path traversal
if (!presetDir.startsWith(presetsRoot + path.sep)) {
throw new Error(`Invalid preset ID '${presetId}'`);
}
// Check directory exists
try {
await fs.access(presetDir);
} catch {
throw new Error(`Preset '${presetId}' not found at ${presetDir}`);
}
// Load manifest
const manifestPath = path.join(presetDir, MANIFEST_FILE);
const manifestRaw = await fs.readFile(manifestPath, "utf-8");
const manifest = JSON.parse(manifestRaw) as PresetManifest;
// Load own tokens
const tokensPath = path.join(presetDir, TOKENS_FILE);
let ownTokens: Partial<DesignTokens> = {};
try {
const tokensRaw = await fs.readFile(tokensPath, "utf-8");
ownTokens = JSON.parse(tokensRaw) as Partial<DesignTokens>;
} catch {
// No tokens file — ok for child presets
}
// Resolve parent tokens (inheritance chain)
let tokens: DesignTokens;
if (manifest.extends) {
if (visitedIds.has(manifest.extends)) {
throw new Error(
`Circular preset inheritance detected: '${manifest.extends}' is already in the chain [${[...visitedIds].join(" → ")}]`
);
}
const nextVisited = new Set([...visitedIds, presetId]);
const parent = await loadPreset(manifest.extends, nextVisited);
tokens = deepmerge(parent.tokens, ownTokens as DesignTokens, {
arrayMerge: (_dst, src) => src,
});
} else {
tokens = ownTokens as DesignTokens;
}
// Load components — scan all subdirectories dynamically
const components: Record<string, ComponentTemplate> = {};
const componentsRoot = path.join(presetDir, "components");
try {
const categoryEntries = await fs.readdir(componentsRoot, { withFileTypes: true });
const categoryDirs = categoryEntries
.filter((e) => e.isDirectory())
.map((e) => e.name);
for (const dir of categoryDirs) {
const dirPath = path.join(componentsRoot, dir);
const files = await fs.readdir(dirPath);
for (const file of files.filter((f) => f.endsWith(".json"))) {
const raw = await fs.readFile(path.join(dirPath, file), "utf-8");
const template = JSON.parse(raw) as ComponentTemplate;
components[template.name] = template;
}
}
} catch {
// No components directory — ok
}
// Inherit parent components if extends
if (manifest.extends) {
const nextVisited = new Set([...visitedIds, presetId]);
const parent = await loadPreset(manifest.extends, nextVisited);
for (const [name, template] of Object.entries(parent.components)) {
if (!(name in components)) {
components[name] = template;
}
}
}
// Load layouts
const layouts: Record<string, LayoutTemplate> = {};
const layoutsDir = path.join(presetDir, "layouts");
try {
const files = await fs.readdir(layoutsDir);
for (const file of files.filter((f) => f.endsWith(".json"))) {
const raw = await fs.readFile(path.join(layoutsDir, file), "utf-8");
const layout = JSON.parse(raw) as LayoutTemplate;
layouts[layout.name] = layout;
}
} catch {
// No layouts directory
}
// Inherit parent layouts if extends
if (manifest.extends) {
const nextVisited = new Set([...visitedIds, presetId]);
const parent = await loadPreset(manifest.extends, nextVisited);
for (const [name, layout] of Object.entries(parent.layouts)) {
if (!(name in layouts)) {
layouts[name] = layout;
}
}
}
return { manifest, tokens, components, layouts };
}
