main.tf

data "aws_region" "current" {
  count = var.create ? 1 : 0
}
data "aws_partition" "current" {
  count = var.create ? 1 : 0
}
data "aws_caller_identity" "current" {
  count = var.create ? 1 : 0
}
data "aws_iam_session_context" "current" {
  count = var.create ? 1 : 0
  arn   = data.aws_caller_identity.current[0].arn
}

locals {
  account_id = try(data.aws_caller_identity.current[0].account_id, "")
  partition  = try(data.aws_partition.current[0].partition, "")
  region     = try(data.aws_region.current[0].name, "")

  static_domain_arn = "arn:${local.partition}:es:${local.region}:${local.account_id}:domain/${var.domain_name}"

  tags = merge(var.tags, { terraform-aws-modules = "opensearch" })
}

################################################################################
# Domain
################################################################################

resource "aws_opensearch_domain" "this" {
  count = var.create ? 1 : 0

  # Controlled via aws_opensearch_domain_policy below
  # access_policies  = var.access_policies
  advanced_options = var.advanced_options

  dynamic "advanced_security_options" {
    for_each = length(var.advanced_security_options) > 0 ? [var.advanced_security_options] : []

    content {
      anonymous_auth_enabled         = try(advanced_security_options.value.anonymous_auth_enabled, false)
      enabled                        = try(advanced_security_options.value.enabled, true)
      internal_user_database_enabled = try(advanced_security_options.value.internal_user_database_enabled, null)

      dynamic "master_user_options" {
        for_each = try([advanced_security_options.value.master_user_options], [{}])

        content {
          master_user_arn      = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_arn, data.aws_iam_session_context.current[0].issuer_arn) : null
          master_user_name     = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_name, null) : null
          master_user_password = try(master_user_options.value.master_user_arn, null) == null ? try(master_user_options.value.master_user_password, null) : null
        }
      }
    }
  }

  dynamic "auto_tune_options" {
    for_each = length(var.auto_tune_options) > 0 ? [var.auto_tune_options] : []

    content {
      desired_state = try(auto_tune_options.value.desired_state, "ENABLED")

      dynamic "maintenance_schedule" {
        for_each = try(auto_tune_options.value.maintenance_schedule, [])

        content {
          cron_expression_for_recurrence = maintenance_schedule.value.cron_expression_for_recurrence

          dynamic "duration" {
            for_each = [maintenance_schedule.value.duration]

            content {
              unit  = duration.value.unit
              value = duration.value.value
            }
          }

          start_at = maintenance_schedule.value.start_at
        }
      }

      rollback_on_disable = try(auto_tune_options.value.rollback_on_disable, null)
      use_off_peak_window = try(auto_tune_options.value.use_off_peak_window, null)
    }
  }

  dynamic "cluster_config" {
    for_each = length(var.cluster_config) > 0 ? [var.cluster_config] : []

    content {
      dynamic "cold_storage_options" {
        for_each = try([cluster_config.value.cold_storage_options], [])

        content {
          enabled = try(cold_storage_options.value.enabled, null)
        }
      }

      dedicated_master_count        = try(cluster_config.value.dedicated_master_count, 3)
      dedicated_master_enabled      = try(cluster_config.value.dedicated_master_enabled, true)
      dedicated_master_type         = try(cluster_config.value.dedicated_master_type, "c6g.large.search")
      instance_count                = try(cluster_config.value.instance_count, 3)
      instance_type                 = try(cluster_config.value.instance_type, "r6g.large.search")
      multi_az_with_standby_enabled = try(cluster_config.value.multi_az_with_standby_enabled, null)
      warm_count                    = try(cluster_config.value.warm_count, null)
      warm_enabled                  = try(cluster_config.value.warm_enabled, null)
      warm_type                     = try(cluster_config.value.warm_type, null)

      dynamic "zone_awareness_config" {
        for_each = try([cluster_config.value.zone_awareness_config], [])

        content {
          availability_zone_count = try(zone_awareness_config.value.availability_zone_count, null)
        }
      }

      zone_awareness_enabled = try(cluster_config.value.zone_awareness_enabled, true)
    }
  }

  dynamic "cognito_options" {
    for_each = length(var.cognito_options) > 0 ? [var.cognito_options] : []

    content {
      enabled          = try(cognito_options.value.enabled, null)
      identity_pool_id = cognito_options.value.identity_pool_id
      role_arn         = cognito_options.value.role_arn
      user_pool_id     = cognito_options.value.user_pool_id
    }
  }

  dynamic "domain_endpoint_options" {
    for_each = length(var.domain_endpoint_options) > 0 ? [var.domain_endpoint_options] : []

    content {
      custom_endpoint                 = try(domain_endpoint_options.value.custom_endpoint, null)
      custom_endpoint_certificate_arn = try(domain_endpoint_options.value.custom_endpoint_certificate_arn, null)
      custom_endpoint_enabled         = try(domain_endpoint_options.value.custom_endpoint_enabled, null)
      enforce_https                   = try(domain_endpoint_options.value.enforce_https, true)
      tls_security_policy             = try(domain_endpoint_options.value.tls_security_policy, "Policy-Min-TLS-1-2-2019-07")
    }
  }

  domain_name = var.domain_name

  dynamic "ebs_options" {
    for_each = length(var.ebs_options) > 0 ? [var.ebs_options] : []

    content {
      ebs_enabled = try(ebs_options.value.ebs_enabled, true)
      iops        = try(ebs_options.value.iops, null)
      throughput  = try(ebs_options.value.throughput, null)
      volume_size = try(ebs_options.value.volume_size, null)
      volume_type = try(ebs_options.value.volume_type, "gp3")
    }
  }

  dynamic "encrypt_at_rest" {
    for_each = length(var.encrypt_at_rest) > 0 ? [var.encrypt_at_rest] : []

    content {
      enabled    = try(encrypt_at_rest.value.enabled, true)
      kms_key_id = try(encrypt_at_rest.value.kms_key_id, null)
    }
  }

  engine_version = var.engine_version

  dynamic "log_publishing_options" {
    for_each = { for opt in var.log_publishing_options : opt.log_type => opt }

    content {
      cloudwatch_log_group_arn = try(log_publishing_options.value.cloudwatch_log_group_arn, aws_cloudwatch_log_group.this[log_publishing_options.key].arn)
      enabled                  = try(log_publishing_options.value.enabled, true)
      log_type                 = log_publishing_options.value.log_type
    }
  }

  dynamic "node_to_node_encryption" {
    for_each = length(var.node_to_node_encryption) > 0 ? [var.node_to_node_encryption] : []

    content {
      enabled = try(node_to_node_encryption.value.enabled, true)
    }
  }

  dynamic "off_peak_window_options" {
    for_each = length(var.off_peak_window_options) > 0 ? [var.off_peak_window_options] : []

    content {
      enabled = try(off_peak_window_options.value.enabled, true)

      dynamic "off_peak_window" {
        for_each = try([off_peak_window_options.value.off_peak_window], [])

        content {
          dynamic "window_start_time" {
            for_each = try([off_peak_window.value.window_start_time], [])

            content {
              hours   = try(window_start_time.value.hours, null)
              minutes = try(window_start_time.value.minutes, null)
            }
          }
        }
      }
    }
  }

  dynamic "software_update_options" {
    for_each = length(var.software_update_options) > 0 ? [var.software_update_options] : []

    content {
      auto_software_update_enabled = try(software_update_options.value.auto_software_update_enabled, true)
    }
  }

  dynamic "vpc_options" {
    for_each = length(var.vpc_options) > 0 ? [var.vpc_options] : []

    content {
      security_group_ids = concat(try(vpc_options.value.security_group_ids, []), aws_security_group.this[*].id)
      subnet_ids         = try(vpc_options.value.subnet_ids, null)
    }
  }

  tags = local.tags
}

################################################################################
# Package Association(s)
################################################################################

resource "aws_opensearch_package_association" "this" {
  for_each = { for k, v in var.package_associations : k => v if var.create }

  package_id  = try(each.value.package_id, each.key)
  domain_name = aws_opensearch_domain.this[0].domain_name
}

################################################################################
# VPC Endpoint(s)
################################################################################

resource "aws_opensearch_vpc_endpoint" "this" {
  for_each = { for k, v in var.vpc_endpoints : k => v if var.create }

  domain_arn = aws_opensearch_domain.this[0].arn

  vpc_options {
    security_group_ids = try(each.value.security_group_ids, null)
    subnet_ids         = each.value.subnet_ids
  }
}

################################################################################
# Access Policy
################################################################################

locals {
  create_access_policy = var.create && var.create_access_policy && (length(var.access_policy_statements) > 0 || length(var.access_policy_source_policy_documents) > 0 || length(var.access_policy_override_policy_documents) > 0)
}

resource "aws_opensearch_domain_policy" "this" {
  count = var.create && var.enable_access_policy && (local.create_access_policy || var.access_policies != null) ? 1 : 0

  domain_name     = aws_opensearch_domain.this[0].domain_name
  access_policies = local.create_access_policy ? data.aws_iam_policy_document.this[0].json : var.access_policies
}

data "aws_iam_policy_document" "this" {
  count = local.create_access_policy ? 1 : 0

  source_policy_documents   = var.access_policy_source_policy_documents
  override_policy_documents = var.access_policy_override_policy_documents

  dynamic "statement" {
    for_each = var.access_policy_statements

    content {
      sid         = try(statement.value.sid, null)
      actions     = try(statement.value.actions, null)
      not_actions = try(statement.value.not_actions, null)
      effect      = try(statement.value.effect, null)
      resources = try(statement.value.resources,
        [for path in try(statement.value.resource_paths, ["*"]) : "${aws_opensearch_domain.this[0].arn}/${path}"]
      )
      not_resources = try(statement.value.not_resources, null)

      dynamic "principals" {
        for_each = try(statement.value.principals, [])

        content {
          type        = principals.value.type
          identifiers = principals.value.identifiers
        }
      }

      dynamic "not_principals" {
        for_each = try(statement.value.not_principals, [])

        content {
          type        = not_principals.value.type
          identifiers = not_principals.value.identifiers
        }
      }

      dynamic "condition" {
        for_each = try(statement.value.conditions, [])

        content {
          test     = condition.value.test
          values   = condition.value.values
          variable = condition.value.variable
        }
      }
    }
  }
}

################################################################################
# SAML Options
################################################################################

resource "aws_opensearch_domain_saml_options" "this" {
  count = var.create && var.create_saml_options ? 1 : 0

  domain_name = aws_opensearch_domain.this[0].domain_name

  dynamic "saml_options" {
    for_each = length(var.saml_options) > 0 ? [var.saml_options] : []

    content {
      enabled = try(saml_options.value.enabled, null)

      dynamic "idp" {
        for_each = try([saml_options.value.idp], [])

        content {
          entity_id        = idp.value.entity_id
          metadata_content = idp.value.metadata_content
        }
      }

      master_backend_role     = try(saml_options.value.master_backend_role, null)
      master_user_name        = try(saml_options.value.master_user_name, null)
      roles_key               = try(saml_options.value.roles_key, null)
      session_timeout_minutes = try(saml_options.value.session_timeout_minutes, null)
      subject_key             = try(saml_options.value.subject_key, null)
    }
  }
}

################################################################################
# Outbound Connections
################################################################################

resource "aws_opensearch_outbound_connection" "this" {
  for_each = { for k, v in var.outbound_connections : k => v if var.create }

  accept_connection = try(each.value.accept_connection, null)
  connection_alias  = try(each.value.connection_alias, each.key)
  connection_mode   = each.value.connection_mode

  dynamic "connection_properties" {
    for_each = try([each.value.connection_properties], [])

    content {
      dynamic "cross_cluster_search" {
        for_each = try([connection_properties.value.cross_cluster_search], [])

        content {
          skip_unavailable = try(cross_cluster_search.value.skip_unavailable, null)
        }
      }
    }
  }

  local_domain_info {
    owner_id    = try(each.value.local_domain_info.owner_id, local.account_id)
    region      = try(each.value.local_domain_info.region, local.region)
    domain_name = try(each.value.local_domain_info.domain_name, aws_opensearch_domain.this[0].domain_name)
  }

  remote_domain_info {
    owner_id    = each.value.remote_domain_info.owner_id
    region      = each.value.remote_domain_info.region
    domain_name = each.value.remote_domain_info.domain_name
  }
}

################################################################################
# Cloudwatch Log Group
################################################################################

locals {
  create_cloudwatch_log_groups = var.create && var.create_cloudwatch_log_groups
}

resource "aws_cloudwatch_log_group" "this" {
  for_each = { for opt in var.log_publishing_options : opt.log_type => opt if try(opt.enabled, true) && local.create_cloudwatch_log_groups }

  name              = try(each.value.log_group_name, "/aws/opensearch/${var.domain_name}/${each.key}")
  retention_in_days = try(each.value.log_group_retention_in_days, var.cloudwatch_log_group_retention_in_days)
  kms_key_id        = try(each.value.log_group_kms_key_id, var.cloudwatch_log_group_kms_key_id)

  tags = merge(local.tags, try(each.value.log_group_tags, {}))
}

data "aws_iam_policy_document" "cloudwatch" {
  count = local.create_cloudwatch_log_groups && var.create_cloudwatch_log_resource_policy ? 1 : 0

  statement {
    actions = [
      "logs:CreateLogStream",
      "logs:PutLogEvents",
      "logs:PutLogEventsBatch",
    ]

    # https://github.com/hashicorp/terraform-provider-aws/issues/14497
    # resources = coalescelist([for log in aws_cloudwatch_log_group.this : "${log.arn}:*"], ["arn:${local.partition}:logs:*"])
    resources = ["arn:${local.partition}:logs:*"]

    principals {
      identifiers = ["es.amazonaws.com"]
      type        = "Service"
    }

    condition {
      test     = "StringEquals"
      variable = "aws:SourceAccount"
      values   = [local.account_id]
    }

    condition {
      test     = "ArnLike"
      variable = "aws:SourceArn"
      values   = [local.static_domain_arn]
    }
  }
}

resource "aws_cloudwatch_log_resource_policy" "this" {
  count = local.create_cloudwatch_log_groups && var.create_cloudwatch_log_resource_policy ? 1 : 0

  policy_document = data.aws_iam_policy_document.cloudwatch[0].json
  policy_name     = coalesce(var.cloudwatch_log_resource_policy_name, "opensearch-${var.domain_name}")
}

################################################################################
# Security Group
################################################################################

locals {
  create_security_group = var.create && var.create_security_group && length(var.vpc_options) > 0
  security_group_name   = try(coalesce(var.security_group_name, var.domain_name), "")
}

data "aws_subnet" "this" {
  count = local.create_security_group ? 1 : 0

  id = element(var.vpc_options.subnet_ids, 0)
}

resource "aws_security_group" "this" {
  count = local.create_security_group ? 1 : 0

  name                   = var.security_group_use_name_prefix ? null : local.security_group_name
  name_prefix            = var.security_group_use_name_prefix ? "${local.security_group_name}-" : null
  description            = var.security_group_description
  vpc_id                 = data.aws_subnet.this[0].vpc_id
  revoke_rules_on_delete = true

  tags = merge(local.tags, var.security_group_tags)

  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_vpc_security_group_ingress_rule" "this" {
  for_each = { for k, v in var.security_group_rules : k => v if local.create_security_group && try(v.type, "ingress") == "ingress" }

  # Required
  security_group_id = aws_security_group.this[0].id
  ip_protocol       = try(each.value.ip_protocol, "tcp")

  # Optional
  cidr_ipv4                    = lookup(each.value, "cidr_ipv4", null)
  cidr_ipv6                    = lookup(each.value, "cidr_ipv6", null)
  description                  = try(each.value.description, null)
  from_port                    = try(each.value.from_port, 443)
  prefix_list_id               = lookup(each.value, "prefix_list_id", null)
  referenced_security_group_id = lookup(each.value, "referenced_security_group_id", null)
  to_port                      = try(each.value.to_port, 443)

  tags = merge(local.tags, var.security_group_tags, try(each.value.tags, {}))
}

resource "aws_vpc_security_group_egress_rule" "this" {
  for_each = { for k, v in var.security_group_rules : k => v if local.create_security_group && try(v.type, "ingress") == "egress" }

  # Required
  security_group_id = aws_security_group.this[0].id
  ip_protocol       = try(each.value.ip_protocol, "tcp")

  # Optional
  cidr_ipv4                    = lookup(each.value, "cidr_ipv4", null)
  cidr_ipv6                    = lookup(each.value, "cidr_ipv6", null)
  description                  = try(each.value.description, null)
  from_port                    = try(each.value.from_port, null)
  prefix_list_id               = lookup(each.value, "prefix_list_id", null)
  referenced_security_group_id = lookup(each.value, "referenced_security_group_id", null)
  to_port                      = try(each.value.to_port, null)

  tags = merge(local.tags, var.security_group_tags, try(each.value.tags, {}))
}