[tg-hcl] Support for terragrunt files

README.md

@@ -137,6 +137,15 @@ version = "0.11.3"
 3. Run the command `tfswitch` in the same directory as your `.tfswitchrc`
 
 #### *Instead of a `.tfswitchrc` file, a `.terraform-version` file may be used for compatibility with [`tfenv`](https://github.com/tfutils/tfenv#terraform-version-file) and other tools which use it*
+
+### Use terragrunt.hcl file
+If a terragrunt.hcl file with the terraform constrain is included in the current directory, it should automatically download or switch to that terraform version. For example, the following should automatically switch terraform to the lastest version:     
+```ruby
+terragrunt_version_constraint = ">= 0.26, < 0.27"
+terraform_version_constraint  = ">= 0.13, < 0.14"
+...
+```
+
 ## Automation
 **Automatically switch with bash**
 

main.go

@@ -22,6 +22,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"regexp"
 	"sort"
 	"strings"
 
@@ -47,6 +48,7 @@ const (
 	tfvFilename   = ".terraform-version"
 	rcFilename    = ".tfswitchrc"
 	tomlFilename  = ".tfswitch.toml"
+	tgHclFilename = "terragrunt.hcl"
 )
 
 var version = "0.11.0\n"
@@ -80,6 +82,7 @@ func main() {
 	RCFile := dir + fmt.Sprintf("/%s", rcFilename)                   //settings for .tfswitchrc file in current directory (backward compatible purpose)
 	TOMLConfigFile := dir + fmt.Sprintf("/%s", tomlFilename)         //settings for .tfswitch.toml file in current directory (option to specify bin directory)
 	HomeTOMLConfigFile := homedir + fmt.Sprintf("/%s", tomlFilename) //settings for .tfswitch.toml file in home directory (option to specify bin directory)
+	TGHACLFile := dir + fmt.Sprintf("/%s", tgHclFilename)            //settings for terragrunt.hcl file in current directory (option to specify bin directory)
 
 	switch {
 	case *versionFlag:
@@ -143,6 +146,9 @@ func main() {
 			tfversion := os.Getenv("TF_VERSION")
 			fmt.Printf("Terraform version environment variable: %s\n", tfversion)
 			installVersion(tfversion, custBinPath)
+		/* if terragrunt.hcl file found (IN ADDITION TO A TOML FILE) */
+		case fileExists(TGHACLFile) && len(args) == 0:
+			installTGHclFile(&TGHACLFile, &binPath)
 		// if no arg is provided - but toml file is provided
 		case version != "":
 			installVersion(version, &binPath)
@@ -189,6 +195,10 @@ func main() {
 	case checkTFModuleFileExist(dir) && len(args) == 0:
 		installTFProvidedModule(dir, custBinPath)
 
+	/* if terragrunt.hcl file found */
+	case fileExists(TGHACLFile) && len(args) == 0:
+		installTGHclFile(&TGHACLFile, custBinPath)
+
 	/* if Terraform Version environment variable is set */
 	case checkTFEnvExist() && len(args) == 0:
 		tfversion := os.Getenv("TF_VERSION")
@@ -373,14 +383,20 @@ func installOption(listAll bool, custBinPath *string) {
 
 // install when tf file is provided
 func installTFProvidedModule(dir string, custBinPath *string) {
-	tfversion := ""
+	fmt.Printf("Reading required version from terraform file")
 	module, _ := tfconfig.LoadModule(dir)
-	tfconstraint := module.RequiredCore[0]        //we skip duplicated definitions and use only first one
+	tfconstraint := module.RequiredCore[0] //we skip duplicated definitions and use only first one
+	installFromConstraint(&tfconstraint, custBinPath)
+}
+
+// install using a version constraint
+func installFromConstraint(tfconstraint *string, custBinPath *string) {
+	tfversion := ""
 	listAll := true                               //set list all true - all versions including beta and rc will be displayed
 	tflist, _ := lib.GetTFList(hashiURL, listAll) //get list of versions
-	fmt.Printf("Reading required version from terraform file, constraint: %s\n", tfconstraint)
+	fmt.Printf("Reading required version from constraint: %s\n", *tfconstraint)
 
-	constrains, err := semver.NewConstraint(tfconstraint) //NewConstraint returns a Constraints instance that a Version instance can be checked against
+	constrains, err := semver.NewConstraint(*tfconstraint) //NewConstraint returns a Constraints instance that a Version instance can be checked against
 	if err != nil {
 		fmt.Printf("Error parsing constraint: %s\nPlease check constrain syntax on terraform file.\n", err)
 		fmt.Println()
@@ -415,3 +431,23 @@ func installTFProvidedModule(dir string, custBinPath *string) {
 	fmt.Println("No version found to match constraint. Follow the README.md instructions for setup. https://github.com/warrensbox/terraform-switcher/blob/master/README.md")
 	os.Exit(1)
 }
+
+// Install using version constraint from terragrunt file
+func installTGHclFile(tgFile *string, custBinPath *string) {
+	fmt.Printf("Terragrunt file found: %s\n", *tgFile)
+	content := retrieveFileContents(*tgFile)
+	var constraint = ""
+
+	for _, line := range strings.Split(content, "\n") {
+		regex, _ := regexp.Compile(`^terraform_version_constraint\s+=\s+"(?P<version>.*)".*`)
+
+		if regex.MatchString(line) {
+			res := regex.FindStringSubmatch(line)
+			constraint = res[1]
+			installFromConstraint(&constraint, custBinPath)
+		}
+	}
+
+	fmt.Println("No version found to match constraint. Follow the README.md instructions for setup. https://github.com/warrensbox/terraform-switcher/blob/master/README.md")
+	os.Exit(1)
+}