Prefer game versions according to acceptable versions list (fixes #181)

The acceptable versions list should now be specified in order of preference, where the last version is the most preferable Minecraft version

core/interfaces.go

@@ -10,9 +10,9 @@ type Updater interface {
 	// ParseUpdate takes an unparsed interface{} (as a map[string]interface{}), and returns an Updater for a mod file.
 	// This can be done using the mapstructure library or your own parsing methods.
 	ParseUpdate(map[string]interface{}) (interface{}, error)
-	// CheckUpdate checks whether there is an update for each of the mods in the given slice, for the given MC version,
+	// CheckUpdate checks whether there is an update for each of the mods in the given slice,
 	// called for all of the mods that this updater handles
-	CheckUpdate([]Mod, string, Pack) ([]UpdateCheck, error)
+	CheckUpdate([]Mod, Pack) ([]UpdateCheck, error)
 	// DoUpdate carries out the update previously queried in CheckUpdate, on each Mod's metadata,
 	// given pointers to Mods and the value of CachedState for each mod
 	DoUpdate([]*Mod, []interface{}) error

core/pack.go

@@ -164,6 +164,16 @@ func (pack Pack) GetMCVersion() (string, error) {
 	return mcVersion, nil
 }
 
+// GetSupportedMCVersions gets the versions of Minecraft this pack allows in downloaded mods, ordered by preference (highest = most desirable)
+func (pack Pack) GetSupportedMCVersions() ([]string, error) {
+	mcVersion, ok := pack.Versions["minecraft"]
+	if !ok {
+		return nil, errors.New("no minecraft version specified in modpack")
+	}
+	allVersions := append(append([]string(nil), viper.GetStringSlice("acceptable-game-versions")...), mcVersion)
+	return allVersions, nil
+}
+
 func (pack Pack) GetPackName() string {
 	if pack.Name == "" {
 		return "export"

core/versionutil.go

@@ -145,3 +145,16 @@ func ComponentToFriendlyName(component string) string {
 		return component
 	}
 }
+
+// HighestSliceIndex returns the highest index of the given values in the slice (-1 if no value is found in the slice)
+func HighestSliceIndex(slice []string, values []string) int {
+	highest := -1
+	for _, val := range values {
+		for i, v := range slice {
+			if v == val && i > highest {
+				highest = i
+			}
+		}
+	}
+	return highest
+}