modules/workload_policy/main.tf

locals {
  backup = merge(local.full, local.log, local.diff)
  diff = var.workload_backup_policy == null ? {} : { for key_index, value in var.workload_backup_policy.protection_policy :
    (key_index) => value
    if key_index == "differential" && var.workload_backup_policy["backup_frequency"] == "Weekly"
  }
  full = var.workload_backup_policy == null ? {} : { for key_index, value in var.workload_backup_policy.protection_policy :
    (key_index) => value
    if key_index == "full"
  }
  log = var.workload_backup_policy == null ? {} : { for key_index, value in var.workload_backup_policy.protection_policy :
    (key_index) => value
    if key_index == "log"
  }
}

resource "azurerm_backup_policy_vm_workload" "this" {
  count = var.workload_backup_policy == null ? 0 : 1

  name                = var.workload_backup_policy.name
  recovery_vault_name = var.recovery_vault_name
  resource_group_name = var.resource_group_name
  workload_type       = var.workload_backup_policy.workload_type

  dynamic "protection_policy" {
    for_each = length(local.full) > 0 ? local.full : {}

    content {
      policy_type = protection_policy.value["policy_type"]

      backup {
        frequency = var.workload_backup_policy["backup_frequency"] != null ? var.workload_backup_policy["backup_frequency"] : null #60 #(required) The backup frequency in minutes for the VM Workload Backup Policy. Possible values are 15, 30, 60, 120, 240, 480, 720 and 1440.
        time      = protection_policy.value["backup"].time != null ? protection_policy.value["backup"].time : null
        weekdays  = var.workload_backup_policy["backup_frequency"] != "Daily" && protection_policy.value["backup"].weekdays != null ? protection_policy.value["backup"].weekdays : null # 
      }
      dynamic "retention_daily" {
        for_each = var.workload_backup_policy["backup_frequency"] != "Weekly" ? { this = protection_policy.value["retention_daily_count"] } : {}

        content {
          count = protection_policy.value["retention_daily_count"]
        }
      }
      dynamic "retention_monthly" {
        for_each = protection_policy.value["retention_monthly"] != null ? { this = protection_policy.value["retention_monthly"] } : {}

        content {
          count       = protection_policy.value["retention_monthly"].count != null ? protection_policy.value["retention_monthly"].count : null # (Required) The number of monthly backups to keep. Must be between 1 and 9999
          format_type = var.workload_backup_policy["backup_frequency"]
          monthdays   = var.workload_backup_policy["backup_frequency"] == "Daily" ? protection_policy.value["retention_monthly"].monthdays : []
          weekdays    = protection_policy.value["retention_monthly"].count != null && length(protection_policy.value["retention_monthly"].weeks) > 0 && length(protection_policy.value["backup"].weekdays) > 0 ? protection_policy.value["backup"].weekdays : [] # (Optional) The weekday backups to retain . Must be one of Sunday, Monday, Tuesday, Wednesday, Thursday, Friday or Saturday.
          weeks       = protection_policy.value["retention_monthly"].count != null && var.workload_backup_policy["backup_frequency"] == "Weekly" ? protection_policy.value["retention_monthly"].weeks : null                                                     # (Optional) The weeks of the month to retain backups of. Must be one of First, Second, Third, Fourth, Last.
        }
      }
      dynamic "retention_weekly" {
        for_each = var.workload_backup_policy["backup_frequency"] == "Weekly" ? { this = protection_policy.value["retention_weekly"] } : {}

        content {
          count    = retention_weekly.value.count
          weekdays = retention_weekly.value.weekdays
        }
      }
      dynamic "retention_yearly" {
        for_each = protection_policy.value["retention_yearly"] != null ? { this = protection_policy.value["retention_yearly"] } : {}

        content {
          count       = protection_policy.value["retention_yearly"].count != null ? protection_policy.value["retention_yearly"].count : null # (Required) The number of monthly backups to keep. Must be between 1 and 9999
          format_type = var.workload_backup_policy["backup_frequency"]
          months      = (protection_policy.value["retention_yearly"].count != null && length(protection_policy.value["retention_yearly"].months) > 0) ? protection_policy.value["retention_yearly"].months : [] # (Required) The months of the year to retain backups of. Must be one of January, February, March, April, May, June, July, August, September, October, November and December.
          monthdays   = var.workload_backup_policy["backup_frequency"] == "Daily" ? protection_policy.value["retention_yearly"].monthdays : []
          weekdays    = protection_policy.value["retention_yearly"].count != 0 && length(protection_policy.value["retention_yearly"].months) > 0 && length(protection_policy.value["retention_yearly"].weeks) > 0 ? protection_policy.value["backup"].weekdays : null # (Optional) The weekday backups to retain . Must be one of Sunday, Monday, Tuesday, Wednesday, Thursday, Friday or Saturday.
          weeks       = protection_policy.value["retention_yearly"].count != 0 && var.workload_backup_policy["backup_frequency"] == "Weekly" ? protection_policy.value["retention_yearly"].weeks : null                                                               # (Optional) The weeks of the month to retain backups of. Must be one of First, Second, Third, Fourth, Last.
        }
      }
    }
  }
  # log backup
  dynamic "protection_policy" {
    for_each = length(local.log) > 0 ? local.log : {}

    content {
      policy_type = protection_policy.value["policy_type"]

      backup {
        frequency_in_minutes = protection_policy.value["backup"].frequency_in_minutes != null ? protection_policy.value["backup"].frequency_in_minutes : null #60 #(required) The backup frequency in minutes for the VM Workload Backup Policy. Possible values are 15, 30, 60, 120, 240, 480, 720 and 1440.
      }
      simple_retention {
        count = protection_policy.value["retention_daily_count"] # (Required) The count that is used to count retention duration with duration type Days. Possible values are between 7 and 35.
      }
    }
  }
  # diff backup
  dynamic "protection_policy" {
    for_each = length(local.diff) > 0 ? local.diff : {}

    content {
      policy_type = protection_policy.value["policy_type"]

      backup {
        frequency = var.workload_backup_policy["backup_frequency"]
        time      = protection_policy.value["backup"].time
        weekdays  = protection_policy.value["backup"].weekdays
      }
      simple_retention {
        count = protection_policy.value["retention_daily_count"]
      }
    }
  }
  settings {
    time_zone           = var.workload_backup_policy.settings["time_zone"] # https://jackstromberg.com/2017/01/list-of-time-zones-consumed-by-azure/
    compression_enabled = var.workload_backup_policy.settings["compression_enabled"]
  }
}