Function mergeCodexHooks

src/targets/codex.ts:696–766

(
  existing: Record<string, unknown> | null,
  pluginHooks: Record<string, HookEntry[]>,
  pluginName: string,
)

 * injecting bookkeeping fields into hook entry objects.
 */
export function mergeCodexHooks(
  existing: Record<string, unknown> | null,
  pluginHooks: Record<string, HookEntry[]>,
  pluginName: string,
): Record<string, unknown> {
  const result: Record<string, unknown[]> = {}
  const managed: ManagedIndex = (existing?._managed as ManagedIndex) ?? {}

  // Collect indices of entries managed by this plugin (to be removed)
  const ownedIndices: Record<string, Set<number>> = {}
  if (managed[pluginName]) {
    for (const [event, indices] of Object.entries(managed[pluginName])) {
      ownedIndices[event] = new Set(indices)
    }
  }

  // Preserve existing hooks, filtering out this plugin's managed entries
  const existingHooks = (existing?.hooks ?? {}) as Record<string, unknown[]>
  for (const [event, matchers] of Object.entries(existingHooks)) {
    if (!Array.isArray(matchers)) continue
    const owned = ownedIndices[event]
    result[event] = owned
      ? matchers.filter((_, idx) => !owned.has(idx))
      : [...matchers]
  }

  // Also filter out entries with legacy `_source` tag from this plugin
  // (migration path from the previous `_source`-in-entry format)
  for (const [event, matchers] of Object.entries(result)) {
    result[event] = (matchers as Array<Record<string, unknown>>).filter((m) => {
      if (typeof m === "object" && m !== null && "_source" in m) {
        return m._source !== pluginName
      }
      return true
    })
  }

  // Build new managed index for this plugin
  const newManagedForPlugin: Record<string, number[]> = {}

  // Add this plugin's hooks (clean entries, no _source field)
  for (const [event, matchers] of Object.entries(pluginHooks)) {
    if (!result[event]) result[event] = []
    const indices: number[] = []
    for (const matcher of matchers) {
      indices.push(result[event].length)
      result[event].push({ ...matcher })
    }
    if (indices.length > 0) {
      newManagedForPlugin[event] = indices
    }
  }

  // Remove empty event arrays
  for (const event of Object.keys(result)) {
    if (result[event].length === 0) delete result[event]
  }