Merge pull request #72 from kpucynski/version-from-tf-code

Support reading required version from TF code.

main.go

@@ -22,11 +22,20 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"sort"
 	"strings"
 
+	"github.com/Masterminds/semver"
+
+	// original hashicorp upstream have broken dependencies, so using fork as workaround
+	// TODO: move back to upstream
+	"github.com/kiranjthomas/terraform-config-inspect/tfconfig"
+	//	"github.com/hashicorp/terraform-config-inspect/tfconfig"
+
 	"github.com/manifoldco/promptui"
 	"github.com/pborman/getopt"
 	"github.com/spf13/viper"
+
 	lib "github.com/warrensbox/terraform-switcher/lib"
 )
 
@@ -121,6 +130,50 @@ func main() {
 					os.Exit(1)
 				}
 			}
+		} else if module, _ := tfconfig.LoadModule(dir); len(module.RequiredCore) >= 1 && len(args) == 0 { //if there is a .tfswitchrc file, and no commmand line arguments
+			tfversion := ""
+
+			// we skip duplicated definitions and use only first one
+			tfconstraint := module.RequiredCore[0]
+			tflist, _ := lib.GetTFList(hashiURL, true)
+			fmt.Printf("Reading required version from terraform code, constraint: %s\n", tfconstraint)
+
+			c, err := semver.NewConstraint(tfconstraint)
+			if err != nil {
+				fmt.Println("Error parsing constraint:", err)
+				os.Exit(1)
+			}
+			vs := make([]*semver.Version, len(tflist))
+			for i, r := range tflist {
+				v, err := semver.NewVersion(r)
+				if err != nil {
+					fmt.Printf("Error parsing version: %s", err)
+					os.Exit(1)
+				}
+
+				vs[i] = v
+			}
+
+			sort.Sort(sort.Reverse(semver.Collection(vs)))
+
+			for _, element := range vs {
+				// Validate a version against a constraint.
+				if c.Check(element) {
+					tfversion = string(element.String())
+					fmt.Printf("Matched version: %s\n", tfversion)
+
+					if lib.ValidVersionFormat(tfversion) {
+						lib.Install(string(tfversion), *custBinPath)
+						break
+					} else {
+						fmt.Println("Invalid terraform version format. Format should be #.#.# or #.#.#-@# where # is numbers and @ is word characters. For example, 0.11.7 and 0.11.9-beta1 are valid versions")
+						os.Exit(1)
+					}
+				}
+			}
+
+			fmt.Println("No version found to match constraint.")
+			os.Exit(1)
 
 		} else if _, err := os.Stat(rcfile); err == nil && len(args) == 0 { //if there is a .tfswitchrc file, and no commmand line arguments
 			fmt.Printf("Reading required terraform version %s \n", rcFilename)