Function applyOperation

packages/effect/src/JsonPatch.ts:318–356

(doc: Schema.Json, op: JsonPatchOperation)

}

function applyOperation(doc: Schema.Json, op: JsonPatchOperation): Schema.Json {
  if (op.path === "") {
    if (op.op === "remove") throw new Error("Unsupported operation at the root")
    return op.value
  }

  const resolved = resolveParent(doc, op.path)
  if (resolved === null) {
    throw new Error(`Cannot ${op.op} at "${op.path}" (parent not found or not a container).`)
  }

  const { lastToken, parent, stack } = resolved

  if (Array.isArray(parent)) {
    if (lastToken === "-" && op.op !== "add") {
      throw new Error(`"-" is not valid for ${op.op} at "${op.path}".`)
    }
    const index = lastToken === "-" ? parent.length : toIndex(lastToken)
    const maxIndex = op.op === "add" ? parent.length : parent.length - 1
    if (index > maxIndex) throw new Error(`Array index out of bounds at "${op.path}".`)
    const updated = parent.slice()
    if (op.op === "add") updated.splice(index, 0, op.value)
    else if (op.op === "remove") updated.splice(index, 1)
    else updated[index] = op.value
    return rebuildFromStack(stack, updated)
  }

  if (isJsonObject(parent)) {
    if (op.op !== "add" && !Object.hasOwn(parent, lastToken)) {
      throw new Error(`Property "${lastToken}" does not exist at "${op.path}".`)
    }
    const updated = { ...parent }
    if (op.op === "remove") delete updated[lastToken]
    else InternalRecord.assignProperty(updated, lastToken, op.value)
    return rebuildFromStack(stack, updated)
  }

  throw new Error(`Cannot ${op.op} at "${op.path}" (parent not found or not a container).`)
}

type StackEntry = { readonly container: unknown; readonly token: number | string }