chore: Convert free clusters with count (#13)

* test to implement

* v2 schema

* pass tests

* fix linter

* clarify doc

* comments

* refactor to improve readability

* refactor isFreeTier

* typo

* rename consts

* more comments

* add error checks

Author: lantoli

internal/hcl/hcl.go

@@ -2,22 +2,38 @@ package hcl
 
 import (
 	"fmt"
+	"strconv"
 
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/hclsyntax"
 	"github.com/hashicorp/hcl/v2/hclwrite"
+	"github.com/zclconf/go-cty/cty"
 )
 
 const (
-	resourceType = "resource"
-	cluster      = "mongodbatlas_cluster"
-	advCluster   = "mongodbatlas_advanced_cluster"
+	resourceType                 = "resource"
+	cluster                      = "mongodbatlas_cluster"
+	advCluster                   = "mongodbatlas_advanced_cluster"
+	nameReplicationSpecs         = "replication_specs"
+	nameRegionConfigs            = "region_configs"
+	nameElectableSpecs           = "electable_specs"
+	nameProviderRegionName       = "provider_region_name"
+	nameRegionName               = "region_name"
+	nameProviderName             = "provider_name"
+	nameBackingProviderName      = "backing_provider_name"
+	nameProviderInstanceSizeName = "provider_instance_size_name"
+	nameInstanceSize             = "instance_size"
+	nameClusterType              = "cluster_type"
+	namePriority                 = "priority"
+
+	errFreeCluster = "free cluster (because no " + nameReplicationSpecs + ")"
 )
 
 // ClusterToAdvancedCluster transforms all mongodbatlas_cluster definitions in a
 // Terraform configuration file into mongodbatlas_advanced_cluster schema v2 definitions.
 // All other resources and data sources are left untouched.
-// TODO: at the moment it just changes the resource type.
+// Note: hclwrite.Tokens are used instead of cty.Value so expressions like var.region can be preserved.
+// cty.Value only supports resolved values.
 func ClusterToAdvancedCluster(config []byte) ([]byte, error) {
 	parser, err := getParser(config)
 	if err != nil {
@@ -30,31 +46,105 @@ func ClusterToAdvancedCluster(config []byte) ([]byte, error) {
 			continue
 		}
 		resourceBody := resource.Body()
-
-		// TODO: Do the full transformation
 		labels[0] = advCluster
 		resource.SetLabels(labels)
+
+		if isFreeTier(resourceBody) {
+			if err := fillFreeTier(resourceBody); err != nil {
+				return nil, err
+			}
+		}
+
 		resourceBody.AppendNewline()
 		appendComment(resourceBody, "Generated by atlas-cli-plugin-terraform.")
 		appendComment(resourceBody, "Please confirm that all references to this resource are updated.")
 	}
 	return parser.Bytes(), nil
 }
 
-func getParser(config []byte) (*hclwrite.File, error) {
-	parser, diags := hclwrite.ParseConfig(config, "", hcl.Pos{Line: 1, Column: 1})
-	if diags.HasErrors() {
-		return nil, fmt.Errorf("failed to parse Terraform config file: %s", diags.Error())
+func isFreeTier(body *hclwrite.Body) bool {
+	return body.FirstMatchingBlock(nameReplicationSpecs, nil) == nil
+}
+
+func fillFreeTier(body *hclwrite.Body) error {
+	const (
+		valClusterType = "REPLICASET"
+		valPriority    = 7
+	)
+	body.SetAttributeValue(nameClusterType, cty.StringVal(valClusterType))
+	regionConfig := hclwrite.NewEmptyFile()
+	regionConfigBody := regionConfig.Body()
+	setAttrInt(regionConfigBody, "priority", valPriority)
+	if err := moveAttribute(nameProviderRegionName, nameRegionName, body, regionConfigBody, errFreeCluster); err != nil {
+		return err
 	}
-	return parser, nil
+	if err := moveAttribute(nameProviderName, nameProviderName, body, regionConfigBody, errFreeCluster); err != nil {
+		return err
+	}
+	if err := moveAttribute(nameBackingProviderName, nameBackingProviderName, body, regionConfigBody, errFreeCluster); err != nil {
+		return err
+	}
+	electableSpec := hclwrite.NewEmptyFile()
+	if err := moveAttribute(nameProviderInstanceSizeName, nameInstanceSize, body, electableSpec.Body(), errFreeCluster); err != nil {
+		return err
+	}
+	regionConfigBody.SetAttributeRaw(nameElectableSpecs, tokensObject(electableSpec))
+
+	replicationSpec := hclwrite.NewEmptyFile()
+	replicationSpec.Body().SetAttributeRaw(nameRegionConfigs, tokensArrayObject(regionConfig))
+	body.SetAttributeRaw(nameReplicationSpecs, tokensArrayObject(replicationSpec))
+	return nil
+}
+
+func moveAttribute(fromAttrName, toAttrName string, fromBody, toBody *hclwrite.Body, errPrefix string) error {
+	attr := fromBody.GetAttribute(fromAttrName)
+	if attr == nil {
+		return fmt.Errorf("%s: attribute %s not found", errPrefix, fromAttrName)
+	}
+	fromBody.RemoveAttribute(fromAttrName)
+	toBody.SetAttributeRaw(toAttrName, attr.Expr().BuildTokens(nil))
+	return nil
+}
+
+func setAttrInt(body *hclwrite.Body, attrName string, number int) {
+	tokens := hclwrite.Tokens{
+		{Type: hclsyntax.TokenNumberLit, Bytes: []byte(strconv.Itoa(number))},
+	}
+	body.SetAttributeRaw(attrName, tokens)
+}
+
+func tokensArrayObject(file *hclwrite.File) hclwrite.Tokens {
+	ret := hclwrite.Tokens{
+		{Type: hclsyntax.TokenOBrack, Bytes: []byte("[")},
+	}
+	ret = append(ret, tokensObject(file)...)
+	ret = append(ret,
+		&hclwrite.Token{Type: hclsyntax.TokenCBrack, Bytes: []byte("]")})
+	return ret
+}
+
+func tokensObject(file *hclwrite.File) hclwrite.Tokens {
+	ret := hclwrite.Tokens{
+		{Type: hclsyntax.TokenOBrack, Bytes: []byte("{")},
+		{Type: hclsyntax.TokenNewline, Bytes: []byte("\n")},
+	}
+	ret = append(ret, file.BuildTokens(nil)...)
+	ret = append(ret,
+		&hclwrite.Token{Type: hclsyntax.TokenCBrack, Bytes: []byte("}")})
+	return ret
 }
 
 func appendComment(body *hclwrite.Body, comment string) {
 	tokens := hclwrite.Tokens{
-		&hclwrite.Token{
-			Type:  hclsyntax.TokenComment,
-			Bytes: []byte("# " + comment + "\n"),
-		},
+		&hclwrite.Token{Type: hclsyntax.TokenComment, Bytes: []byte("# " + comment + "\n")},
 	}
 	body.AppendUnstructuredTokens(tokens)
 }
+
+func getParser(config []byte) (*hclwrite.File, error) {
+	parser, diags := hclwrite.ParseConfig(config, "", hcl.Pos{Line: 1, Column: 1})
+	if diags.HasErrors() {
+		return nil, fmt.Errorf("failed to parse Terraform config file: %s", diags.Error())
+	}
+	return parser, nil
+}

internal/hcl/hcl_test.go

@@ -1,6 +1,7 @@
 package hcl_test
 
 import (
+	"encoding/json"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -14,14 +15,20 @@ import (
 
 func TestClusterToAdvancedCluster(t *testing.T) {
 	const (
-		root      = "testdata/clu2adv"
-		inSuffix  = ".in.tf"
-		outSuffix = ".out.tf"
+		root        = "testdata/clu2adv"
+		inSuffix    = ".in.tf"
+		outSuffix   = ".out.tf"
+		errFilename = "errors.json"
 	)
+	fs := afero.NewOsFs()
+	errMap := make(map[string]string)
+	errContent, err := afero.ReadFile(fs, filepath.Join(root, errFilename))
+	require.NoError(t, err)
+	err = json.Unmarshal(errContent, &errMap)
+	require.NoError(t, err)
 	g := goldie.New(t,
 		goldie.WithFixtureDir(root),
 		goldie.WithNameSuffix(outSuffix))
-	fs := afero.NewOsFs()
 	pattern := filepath.Join(root, "*"+inSuffix)
 	inputFiles, err := afero.Glob(fs, pattern)
 	require.NoError(t, err)
@@ -31,7 +38,12 @@ func TestClusterToAdvancedCluster(t *testing.T) {
 		inConfig, err := afero.ReadFile(fs, inputFile)
 		require.NoError(t, err)
 		outConfig, err := hcl.ClusterToAdvancedCluster(inConfig)
-		require.NoError(t, err)
-		g.Assert(t, testName, outConfig)
+		if err == nil {
+			g.Assert(t, testName, outConfig)
+		} else {
+			errMsg, found := errMap[testName]
+			assert.True(t, found, "error not found for test %s", testName)
+			assert.Contains(t, err.Error(), errMsg)
+		}
 	}
 }

internal/hcl/testdata/clu2adv/basic.in.tf

@@ -0,0 +1,2 @@
+resource this is an invalid HCL configuration file
+

internal/hcl/testdata/clu2adv/basic.out.tf

@@ -0,0 +1,4 @@
+{
+	"configuration_file_error": "failed to parse Terraform config file",
+	"free_cluster_missing_attribute": "free cluster (because no replication_specs): attribute backing_provider_name not found"
+}

internal/hcl/testdata/clu2adv/configuration_file_error.in.tf

@@ -0,0 +1,19 @@
+resource "resource1" "res1" {
+  name = "name1"
+}
+
+resource "mongodbatlas_cluster" "free_cluster" { # comment in the resource
+  # comment in own line in the beginning
+  count                       = local.use_free_cluster ? 1 : 0
+  project_id                  = var.project_id # inline comment kept
+  name                        = var.cluster_name
+  # comment in own line in the middle is deleted
+  provider_name               = "TENANT" # inline comment for attribute moved is not kept
+  provider_region_name        = var.region
+  provider_instance_size_name = "M0"
+  # comment in own line at the end happens before replication_specs
+}
+
+data "mongodbatlas_cluster" "cluster2" {
+  name = "name4"
+}

internal/hcl/testdata/clu2adv/errors.json

@@ -0,0 +1,20 @@
+resource "resource1" "res1" {
+  name = "name1"
+}
+
+resource "mongodbatlas_cluster" "free_cluster" { # comment in the resource
+  # comment in own line in the beginning
+  count                       = local.use_free_cluster ? 1 : 0
+  project_id                  = var.project_id # inline comment kept
+  name                        = var.cluster_name
+  # comment in own line in the middle is deleted
+  provider_name               = "TENANT" # inline comment for attribute moved is not kept
+  backing_provider_name       = "AWS"
+  provider_region_name        = var.region
+  provider_instance_size_name = "M0"
+  # comment in own line at the end happens before replication_specs
+}
+
+data "mongodbatlas_cluster" "cluster2" {
+  name = "name4"
+}

internal/hcl/testdata/clu2adv/free_cluster_missing_attribute.in.tf

@@ -0,0 +1,30 @@
+resource "resource1" "res1" {
+  name = "name1"
+}
+
+resource "mongodbatlas_advanced_cluster" "free_cluster" { # comment in the resource
+  # comment in own line in the beginning
+  count      = local.use_free_cluster ? 1 : 0
+  project_id = var.project_id # inline comment kept
+  name       = var.cluster_name
+  # comment in own line at the end happens before replication_specs
+  cluster_type = "REPLICASET"
+  replication_specs = [{
+    region_configs = [{
+      priority              = 7
+      region_name           = var.region
+      provider_name         = "TENANT"
+      backing_provider_name = "AWS"
+      electable_specs = {
+        instance_size = "M0"
+      }
+    }]
+  }]
+
+  # Generated by atlas-cli-plugin-terraform.
+  # Please confirm that all references to this resource are updated.
+}
+
+data "mongodbatlas_cluster" "cluster2" {
+  name = "name4"
+}