Add query package with first set of conditions and tests

database/query/condition-regex.go

@@ -0,0 +1,57 @@
+package query
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+)
+
+type regexCondition struct {
+	key      string
+	operator uint8
+	regex    *regexp.Regexp
+}
+
+func newRegexCondition(key string, operator uint8, value interface{}) *regexCondition {
+	switch v := value.(type) {
+	case string:
+		r, err := regexp.Compile(v)
+		if err != nil {
+			return &regexCondition{
+				key:      fmt.Sprintf("could not compile regex \"%s\": %s", v, err),
+				operator: errorPresent,
+			}
+		}
+		return &regexCondition{
+			key:      key,
+			operator: operator,
+			regex:    r,
+		}
+	default:
+		return &regexCondition{
+			key:      fmt.Sprintf("incompatible value %v for string", value),
+			operator: errorPresent,
+		}
+	}
+}
+
+func (c *regexCondition) complies(f Fetcher) bool {
+	comp, ok := f.GetString(c.key)
+	if !ok {
+		return false
+	}
+
+	switch c.operator {
+	case Matches:
+		return c.regex.MatchString(comp)
+	default:
+		return false
+	}
+}
+
+func (c *regexCondition) check() error {
+	if c.operator == errorPresent {
+		return errors.New(c.key)
+	}
+	return nil
+}