Lens example

lenses.hs

{-# LANGUAGE TemplateHaskell, Rank2Types, NoMonomorphismRestriction #-}
module Main where

import           Control.Lens
import qualified Data.Map.Strict as M

data Deployment = Deployment
                  { _deploymentName :: String
                  , _nodes :: [Node]
                  } deriving Show

data Node = Node
            { _nodeName :: String
            , _applications :: [Application]
            } deriving Show

data Application = Application
                   { _applicationName :: String
                   , _volume :: Volume
                   } deriving Show

data Volume = Volume { _dataset :: Dataset } deriving Show

data Dataset = Dataset
               { _datasetName :: Maybe String
               , _datasetId :: Maybe String
               } deriving Show
makeLenses ''Deployment
makeLenses ''Node
makeLenses ''Application
makeLenses ''Volume
makeLenses ''Dataset

myDeployment = Deployment "deployment1" [node1, node2, node3]

node1 = Node "node1" [app1, app2]
node2 = Node "node2" [app2, app3]
node3 = Node "node3" [app1, app3]

app1 = Application "app1" (Volume (Dataset (Just "dataset1") Nothing))

app2 = Application "app2" (Volume (Dataset Nothing Nothing))

app3 = Application "app3" (Volume (Dataset (Just "dataset3") Nothing))

datasets = M.fromList
           [("dataset1", "9ae635d6-b24d-41b6-a8e5-4b2da67498e9"),
            ("dataset3", "34117f32-e679-4234-92dc-a39246bf436e")]

findDataset (Just name) = M.findWithDefault "MISSING" name datasets
findDataset Nothing = "MISSING"

update_dataset_id dataset = dataset & datasetId .~ Just (findDataset (dataset ^. datasetName))

update_all_dataset_ids deployment = deployment & nodes.mapped.applications.mapped.volume.dataset %~ update_dataset_id

main = print $ update_all_dataset_ids myDeployment

output.hs

Deployment
  { _deploymentName = "deployment1"
  , _nodes =
      [ Node
          { _nodeName = "node1"
          , _applications =
              [ Application
                  { _applicationName = "app1"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset
                              { _datasetName = Just "dataset1"
                              , _datasetId = Just "9ae635d6-b24d-41b6-a8e5-4b2da67498e9"
                              }
                        }
                  }
              , Application
                  { _applicationName = "app2"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset { _datasetName = Nothing , _datasetId = Just "MISSING" }
                        }
                  }
              ]
          }
      , Node
          { _nodeName = "node2"
          , _applications =
              [ Application
                  { _applicationName = "app2"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset { _datasetName = Nothing , _datasetId = Just "MISSING" }
                        }
                  }
              , Application
                  { _applicationName = "app3"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset
                              { _datasetName = Just "dataset3"
                              , _datasetId = Just "34117f32-e679-4234-92dc-a39246bf436e"
                              }
                        }
                  }
              ]
          }
      , Node
          { _nodeName = "node3"
          , _applications =
              [ Application
                  { _applicationName = "app1"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset
                              { _datasetName = Just "dataset1"
                              , _datasetId = Just "9ae635d6-b24d-41b6-a8e5-4b2da67498e9"
                              }
                        }
                  }
              , Application
                  { _applicationName = "app3"
                  , _volume =
                      Volume
                        { _dataset =
                            Dataset
                              { _datasetName = Just "dataset3"
                              , _datasetId = Just "34117f32-e679-4234-92dc-a39246bf436e"
                              }
                        }
                  }
              ]
          }
      ]
  }