main.tf

/**
 * Copyright 2025 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

locals {
  ctx = {
    for k, v in var.context : k => {
      for kk, vv in v : "${local.ctx_p}${k}:${kk}" => vv
    } if !endswith(k, "_vars")
  }
  ctx_p = "$"
  iam_email = (
    local.service_account != null
    ? "serviceAccount:${local.service_account.email}"
    : local.static_iam_email
  )
  name   = split("@", var.name)[0]
  prefix = var.prefix == null ? "" : "${var.prefix}-"
  project_id = (
    var.project_id == null
    # if no project ID is passed we're reusing and can infer it from the email
    ? try(regex("^[^@]+@([^.]+)", var.name)[0], null)
    # otherwise check if we need context expansion
    : lookup(local.ctx.project_ids, var.project_id, var.project_id)
  )
  static_email = (
    var.project_id == null
    ? var.name
    : "${local.prefix}${local.name}@${local.sa_domain}.iam.gserviceaccount.com"
  )
  static_iam_email = "serviceAccount:${local.static_email}"
  static_id = (
    "projects/${local.project_id_universe}/serviceAccounts/${local.static_email}"
  )
  service_account = (
    local.use_data_source
    ? try(data.google_service_account.service_account[0], null)
    : try(google_service_account.service_account[0], null)
  )
  # universe-related locals
  universe = try(
    regex("^([^:]*):[a-z]", local.project_id)[0],
    var.service_account_reuse.universe.prefix,
    ""
  )
  use_data_source = (
    try(var.service_account_reuse.use_data_source, null) == true
  )
  project_id_no_universe = element(split(":", local.project_id), 1)
  # reassemble project id for cases where we are reusing service account
  project_id_universe = (
    local.universe == ""
    ? local.project_id
    : "${local.universe}:${local.project_id_no_universe}"
  )
  sa_domain = join(".", compact([
    local.project_id_no_universe, local.universe
  ]))
  # the condition here avoids referring to attributes not known at plan time
  tag_bindings = (
    var.service_account_reuse != null ||
    try(var.service_account_reuse.attributes.unique_id, null) != null
    ? {}
    : var.tag_bindings
  )
  _tag_bindings = {
    for k, v in local.tag_bindings : k => lookup(local.ctx.tag_values, v, v)
  }
}

data "google_service_account" "service_account" {
  count = local.use_data_source ? 1 : 0
  project = (
    strcontains(local.project_id, ":")
    ? join(".", reverse(split(":", local.project_id)))
    : local.project_id
  )
  account_id = "${local.prefix}${local.name}"
}

resource "google_service_account" "service_account" {
  count                        = var.service_account_reuse == null ? 1 : 0
  project                      = local.project_id
  account_id                   = "${local.prefix}${local.name}"
  display_name                 = var.display_name
  description                  = var.description
  create_ignore_already_exists = var.create_ignore_already_exists
}

resource "google_tags_tag_binding" "binding" {
  for_each  = local.tag_bindings
  parent    = "//iam.googleapis.com/projects/${coalesce(var.project_number, var.project_id)}/serviceAccounts/${local.service_account.unique_id}"
  tag_value = templatestring(local._tag_bindings[each.key], var.context.tag_vars)
}