const path = require('path');
const { randomUUID } = require('crypto');
const { snapshotsSystemDir, snapshotsTenantsDir } = require('./paths');
const { readJsonIfExists, writeJson } = require('./fs');
const { listAllResources } = require('./resources');

function buildResourceDiff(resource) {
  return {
    in_sync: JSON.stringify(resource.desired_state || {}) === JSON.stringify(resource.current_state || {}),
    desired_state: resource.desired_state || {},
    current_state: resource.current_state || {},
  };
}

function filterTenantResources(resources, tenantId) {
  const filtered = {};

  for (const [resourceType, items] of Object.entries(resources)) {
    filtered[resourceType] = items.filter((item) => {
      if (!item) {
        return false;
      }

      if (resourceType === 'tenant') {
        return item.id === tenantId;
      }

      return item.desired_state && item.desired_state.tenant_id === tenantId;
    });
  }

  return filtered;
}

async function createSnapshot(scope, context) {
  const resources = await listAllResources();
  const selected = scope === 'system'
    ? resources
    : filterTenantResources(resources, scope.replace('tenant:', ''));

  const snapshot = {
    snapshot_id: randomUUID(),
    schema_version: 'v1',
    scope,
    created_at: new Date().toISOString(),
    request_id: context.request_id,
    correlation_id: context.correlation_id,
    resources: selected,
    diffs: Object.fromEntries(
      Object.entries(selected).map(([resourceType, items]) => [
        resourceType,
        items.map((item) => ({
          resource_id: item.id,
          diff: buildResourceDiff(item),
        })),
      ])
    ),
  };

  const filePath = scope === 'system'
    ? path.join(snapshotsSystemDir, 'latest.json')
    : path.join(snapshotsTenantsDir, `${scope.replace('tenant:', '')}.json`);

  await writeJson(filePath, snapshot);
  return snapshot;
}

async function getLatestSystemSnapshot() {
  return readJsonIfExists(path.join(snapshotsSystemDir, 'latest.json'));
}

async function getLatestTenantSnapshot(tenantId) {
  return readJsonIfExists(path.join(snapshotsTenantsDir, `${tenantId}.json`));
}

module.exports = {
  createSnapshot,
  getLatestSystemSnapshot,
  getLatestTenantSnapshot,
};