Lockfile Inventory

import {
  computeMcpServerFingerprint,
  deriveLockedMcpInventory,
  type McpServerDeclaration,
  parseLockfileDocument,
} from '@agent-facets/protocol'

type Comparison =
  | { ok: true }
  | { ok: false; reason: 'unreadable' | 'inventory-unavailable' | 'collision' }
  | { ok: false; reason: 'mismatch'; missing: string[]; unexpected: string[]; changed: string[] }

/** `exported` maps each effective name you wrote to the declaration you wrote under it. */
export function compareExports(
  lockfileText: string,
  exported: Readonly<Record<string, McpServerDeclaration>>,
): Comparison {
  const parsed = parseLockfileDocument(lockfileText)
  if (!parsed.ok) return { ok: false, reason: 'unreadable' }
  const inventory = deriveLockedMcpInventory(parsed.data.lockfile)
  if (!inventory.ok) return { ok: false, reason: inventory.reason }

  const expected = new Map(inventory.servers.map((server) => [server.effectiveName, server.fingerprint]))
  // Recompute from what was exported. Copying the expected fingerprint would compare nothing.
  const observed = new Map(
    Object.entries(exported).map(([name, declaration]) => [name, computeMcpServerFingerprint(declaration)]),
  )

  const missing = [...expected.keys()].filter((name) => !observed.has(name)).sort()
  const unexpected = [...observed.keys()].filter((name) => !expected.has(name)).sort()
  const changed = [...expected]
    .filter(([name, fingerprint]) => observed.has(name) && observed.get(name) !== fingerprint)
    .map(([name]) => name)
    .sort()

  if (missing.length + unexpected.length + changed.length === 0) return { ok: true }
  return { ok: false, reason: 'mismatch', missing, unexpected, changed }
}