/**
 * earth-now.co
 * Author:  Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 * File:    packages/registry/src/load.ts
 * Purpose: Load and validate the metric YAML files and JSON fixtures from disk (server-side only)
 */

import { readFileSync, readdirSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";
import { parse as parseYaml } from "yaml";
import {
  type MetricEntry,
  type MetricFixture,
  fixturesFileSchema,
  metricsFileSchema,
} from "./schema.js";

// load.js lives in <pkg>/dist (built) or <pkg>/src (tests) — the package root is one level up.
const PACKAGE_ROOT = join(dirname(fileURLToPath(import.meta.url)), "..");

export interface Registry {
  metrics: MetricEntry[];
  byId: Map<string, MetricEntry>;
}

/** Load every metrics/*.yaml file, validate, and check cross-references. */
export function loadRegistry(rootDir: string = PACKAGE_ROOT): Registry {
  const metricsDir = join(rootDir, "metrics");
  const files = readdirSync(metricsDir).filter((f) => f.endsWith(".yaml") || f.endsWith(".yml"));
  const metrics: MetricEntry[] = [];
  for (const file of files.sort()) {
    // merge: true enables YAML 1.1 merge keys (<<: *anchor) used by grouped
    // metric families like the top-10 country populations.
    const doc: unknown = parseYaml(readFileSync(join(metricsDir, file), "utf8"), { merge: true });
    const parsed = metricsFileSchema.safeParse(doc);
    if (!parsed.success) {
      throw new Error(`Registry file ${file} is invalid:\n${parsed.error.message}`);
    }
    metrics.push(...parsed.data.metrics);
  }

  const byId = new Map<string, MetricEntry>();
  for (const m of metrics) {
    if (byId.has(m.id)) throw new Error(`Duplicate metric id in registry: ${m.id}`);
    byId.set(m.id, m);
  }
  // Derived metrics must reference declared metrics.
  for (const m of metrics) {
    if (m.derived) {
      for (const input of m.derived.inputs) {
        if (!byId.has(input.id)) {
          throw new Error(`Metric ${m.id} derives from undeclared metric ${input.id}`);
        }
      }
    }
  }
  return { metrics, byId };
}

/** Load every fixtures/*.json file (keyed by metric id) and validate. */
export function loadFixtures(rootDir: string = PACKAGE_ROOT): Map<string, MetricFixture> {
  const fixturesDir = join(rootDir, "fixtures");
  const files = readdirSync(fixturesDir).filter((f) => f.endsWith(".json"));
  const out = new Map<string, MetricFixture>();
  for (const file of files.sort()) {
    const doc: unknown = JSON.parse(readFileSync(join(fixturesDir, file), "utf8"));
    const parsed = fixturesFileSchema.safeParse(doc);
    if (!parsed.success) {
      throw new Error(`Fixture file ${file} is invalid:\n${parsed.error.message}`);
    }
    for (const [metricId, fixture] of Object.entries(parsed.data)) {
      if (out.has(metricId)) throw new Error(`Duplicate fixture for metric ${metricId} in ${file}`);
      out.set(metricId, fixture);
    }
  }
  return out;
}