table: Add identity, static and regexp table modules

internal/table/regexp.go

@@ -0,0 +1,93 @@
+package table
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/foxcpp/maddy/internal/config"
+	"github.com/foxcpp/maddy/internal/module"
+)
+
+type Regexp struct {
+	modName    string
+	instName   string
+	inlineArgs []string
+
+	re          *regexp.Regexp
+	replacement string
+
+	expandPlaceholders bool
+}
+
+func NewRegexp(modName, instName string, _, inlineArgs []string) (module.Module, error) {
+	return &Regexp{
+		modName:    modName,
+		instName:   instName,
+		inlineArgs: inlineArgs,
+	}, nil
+}
+
+func (r *Regexp) Init(cfg *config.Map) error {
+	var (
+		fullMatch       bool
+		caseInsensitive bool
+	)
+	cfg.Bool("full_match", false, true, &fullMatch)
+	cfg.Bool("case_insensitive", false, true, &caseInsensitive)
+	cfg.Bool("expand_replaceholders", false, true, &r.expandPlaceholders)
+	if _, err := cfg.Process(); err != nil {
+		return err
+	}
+
+	if len(r.inlineArgs) < 2 {
+		return fmt.Errorf("%s: two arguments required", r.modName)
+	}
+	regex := r.inlineArgs[0]
+	r.replacement = r.inlineArgs[1]
+
+	if fullMatch {
+		if !strings.HasPrefix(regex, "^") {
+			regex = "^" + regex
+		}
+		if !strings.HasSuffix(regex, "$") {
+			regex = regex + "$"
+		}
+	}
+
+	if caseInsensitive {
+		regex = "(?i)" + regex
+	}
+
+	var err error
+	r.re, err = regexp.Compile(regex)
+	if err != nil {
+		return fmt.Errorf("%s: %v", r.modName, err)
+	}
+	return nil
+}
+
+func (r *Regexp) Name() string {
+	return r.modName
+}
+
+func (r *Regexp) InstanceName() string {
+	return r.modName
+}
+
+func (r *Regexp) Lookup(key string) (string, bool, error) {
+	matches := r.re.FindStringSubmatchIndex(key)
+	if matches == nil {
+		return "", false, nil
+	}
+
+	if !r.expandPlaceholders {
+		return r.replacement, true, nil
+	}
+
+	return string(r.re.ExpandString([]byte{}, r.replacement, key, matches)), true, nil
+}
+
+func init() {
+	module.Register("regexp", NewRegexp)
+}