Add query package with first set of conditions and tests

database/query/condition-string.go

@@ -0,0 +1,56 @@
+package query
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+type stringCondition struct {
+	key      string
+	operator uint8
+	value    string
+}
+
+func newStringCondition(key string, operator uint8, value interface{}) *stringCondition {
+	switch v := value.(type) {
+	case string:
+		return &stringCondition{
+			key:      key,
+			operator: operator,
+			value:    v,
+		}
+	default:
+		return &stringCondition{
+			key:      fmt.Sprintf("incompatible value %v for string", value),
+			operator: errorPresent,
+		}
+	}
+}
+
+func (c *stringCondition) complies(f Fetcher) bool {
+	comp, ok := f.GetString(c.key)
+	if !ok {
+		return false
+	}
+
+	switch c.operator {
+	case Matches:
+		return c.value == comp
+	case Contains:
+		return strings.Contains(comp, c.value)
+	case StartsWith:
+		return strings.HasPrefix(comp, c.value)
+	case EndsWith:
+		return strings.HasSuffix(comp, c.value)
+	default:
+		return false
+	}
+}
+
+func (c *stringCondition) check() error {
+	if c.operator == errorPresent {
+		return errors.New(c.key)
+	}
+	return nil
+}