I'm learning Helm to setup my 3 AWS EKS clusters - sandbox, staging, and production.

How can I set up my templates so some values are derived based on which cluster the chart is being installed at? For example, in my myapp/templates/deployment.yaml I may want

apiVersion: apps/v1
kind: Deployment
metadata:
  ...
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}

I may want replicas to be either 1, 2, or 4 depending if I'm installing the chart in my sandbox, staging, or production cluster respectively? I wanna do same trick for cpu and memory requests and limits for my pods for example.

I was thinking of having something like this in my values.yaml file

environments:
  - sandbox
  - staging
  - production
perClusterValues:
  replicas:
    - 1
    - 2
    - 4
  cpu:
    requests:
      - 256m
      - 512m
      - 1024m
    limits:
      - 512m
      - 1024m
      - 2048m
  memory:
    requests:
      - 1024Mi
      - 1024Mi
      - 2048Mi
    limits:
      - 2048Mi
      - 2048Mi
      - 3072Mi

So if I install a helm chart in the sandbox environment, I want to be able to do

$ helm install myapp myapp --set environment=sandbox

apiVersion: apps/v1
kind: Deployment
metadata:
  ...
spec:
  {{- if not .Values.autoscaling.enabled }}
  # In pseudo-code, in my YAML files
  # Get the index value from .Values.environments list
  # based on pass-in environment parameter
  {{ $myIndex = indexOf .Values.environments .Value.environment }}
  replicas: {{ .Values.perClusterValues.replicas $myIndex }}
  {{- end }}

I hope you understand my logic, but what is the correct syntax? Or is this even a good approach?