Add method of entity.Address to generate a nickname

entity/meta.go

@@ -1,6 +1,9 @@
 package entity
 
 import "fmt"
+import "strings"
+import "unicode"
+import "unicode/utf8"
 import "path/filepath"
 import "git.tebibyte.media/sashakoshka/fspl/errors"
 
@@ -31,7 +34,7 @@ func (addr Address) String () string {
 }
 // SourceFile returns the FSPL source file associated with the address. If the
 // address does not point to an FSPL source file, it returns "", false.
-func (addr Address) IsSourceFile () (string, bool) {
+func (addr Address) SourceFile () (string, bool) {
 	ext := filepath.Ext(string(addr))
 	if ext == ".fspl" {
 		return "", false
@@ -52,3 +55,46 @@ func (addr Address) Module () (string, bool) {
 		return "", false
 	}
 }
+// Nickname automatically generates a nickname from the address, which is a
+// valid Ident token. On failure "", false is returned. The nickname is
+// generated according to the folowing rules:
+//
+//  - If the name contains at least one dot, the last dot and everything after
+//    it is removed
+//  - All non-letter, non-numeric characters are removed, and any letters that
+//    were directly after them are converted to uppercase
+//  - All numeric digits at the start of the string are removed
+//  - The first character is converted to lowercase
+func (addr Address) Nickname () (string, bool) {
+	// get the normalized basename with no extension
+	base := filepath.Base(string(addr))
+	base  = strings.TrimSuffix(base, filepath.Ext(base))
+
+	// remove all non-letter, non-digit characters and convert to camel case
+	nickname := ""
+	uppercase := false
+	for _, char := range base {
+		if unicode.IsLetter(char) || unicode.IsDigit(char) {
+			if uppercase {
+				uppercase = false
+				char = unicode.ToUpper(char)
+			}
+			nickname += string(char)
+		} else {
+			uppercase = true
+		}
+	}
+
+	// remove numeric digits
+	for len(nickname) > 0 {
+		char, size := utf8.DecodeRuneInString(nickname)
+		nickname = nickname[size:]
+		if unicode.IsLetter(char) {
+			// lowercase the first letter
+			nickname = string(unicode.ToLower(char)) + nickname
+			break
+		}
+	}
+	
+	return nickname, nickname != ""
+}