terraform json map regex lookup and using loops properly

Question

So I have a json file below I can definitely restructure it as needed, but its what I started with. It needs to be an external format of terraform of any type. I chose json based on seemingly easy compatability.

I would like to be able to loop through all the regex patterns in the json file below (I truncated this list) and if the regex pattern is a match to testcomputer, then return the ou value to another local variable. One caveat, that I am not sure if I am having an issue with, is that the json requires escaping the \ . In an imperative programming language I just handled this with a switch/case stanza or method that performs evaluations. Not sure how to best do this with HCL.

ou.json:

{
  "ProdInf": {
    "regex": "/^(?i)nyinf-p(\\d+)/",
    "ou": "OU=Inf,OU=Prod,OU=Servers,DC=example,DC=local"
  },
  "ProdHyperV": {
    "regex": "/^(?i)nyhyp-p(\\d+)/",
    "ou": "OU=HyperV,OU=Prod,OU=Servers,DC=example,DC=local"
  },
  "ProdRDS": {
    "regex": "/^(?i)nyrds-p(\\d+)/",
    "ou": "OU=RDS,OU=Prod,OU=Servers,DC=example,DC=local"
  }
}

I have some initial terraform code (contrived and based on my real issue) but it I can't figure out how to proceed from here.:

locals {
  testcomputer = "nyhyp-p29"
  map1 = jsondecode(file("./ou.json"))
  # started to play with loops here, but not really sure how to do what I am want.
  oulist = [for ou in local.map1 : ou].*.ou
  regexlist = [for regex in local.map1 : regex].*.regex
  test_computer_ou = # this is the desired value I am trying to get
}

Answer 1

You would want to modify your json file to look something like this:

{
    "ProdInf": {
        "regex": "^(?i)nyinf-p(\\d+)$",
        "ou": "OU=Inf,OU=Prod,OU=Servers,DC=example,DC=local"
    },
    "ProdHyperV": {
        "regex": "^(?i)nyhyp-p(\\d+)$",
        "ou": "OU=HyperV,OU=Prod,OU=Servers,DC=example,DC=local"
    },
    "ProdRDS": {
        "regex": "^(?i)nyrds-p(\\d+)$",
        "ou": "OU=RDS,OU=Prod,OU=Servers,DC=example,DC=local"
    }
}

From your question I understood that you are looking for a full match, so I've added regex anchors.

The local variables are the following:

locals {
  testcomputer = "nyhyp-p29"
  map1 = jsondecode(file("./ou.json"))
  oulist = [for ou in local.map1 : ou].*.ou
  regexlist = [for regex in local.map1 : regex].*.regex
  test_computer_ou = [for key, value in local.map1: value.ou if length(regexall(value.regex, local.testcomputer)) == 1]
}

The value for test_computer_ou will be:

output "test_computer_ou" {
  value = local.test_computer_ou
}

Output value:

test_computer_ou = [
  "OU=HyperV,OU=Prod,OU=Servers,DC=example,DC=local",
]