From 564ef69718207b6ebf7eb0897706e3019564d051 Mon Sep 17 00:00:00 2001
From: "marko.tikvic" <marko.tikvic@to-net.rs>
Date: Tue, 23 Oct 2018 14:54:44 +0200
Subject: [PATCH] added simple sql filter string parser/generator

---
 filtering.go | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 filtering.go

diff --git a/filtering.go b/filtering.go
new file mode 100644
index 0000000..ec68510
--- /dev/null
+++ b/filtering.go
@@ -0,0 +1,76 @@
+package webutility
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+type Filter map[string]string
+
+func (fs Filter) validate(validFilters []string) (Filter, bool) {
+	goodFilters := make(map[string]string)
+	cnt := 0
+	len := 0
+	for f, _ := range fs {
+		len++
+		for _, v := range validFilters {
+			if f == v {
+				cnt++
+				goodFilters[f] = fs[f]
+			}
+		}
+	}
+
+	result := true
+	if len > 0 && cnt == 0 {
+		// if no valid filters are found declare filtering request as invalid
+		result = false
+	}
+
+	return goodFilters, result
+}
+
+// requires input in format: "param1::value1|param2::value2..."
+func ParseFilters(req *http.Request, header string) (filters Filter) {
+	q := req.FormValue(header)
+	q = strings.Trim(q, "\"")
+	kvp := strings.Split(q, "|")
+	filters = make(map[string]string, len(kvp))
+
+	for i, _ := range kvp {
+		kv := strings.Split(kvp[i], "::")
+		if len(kv) == 2 {
+			key := kv[0]
+			val := kv[1]
+			filters[key] = val
+		}
+	}
+
+	return filters
+}
+
+func MakeFilterString(prefix string, filters Filter, validFilters []string) (res string, ok bool) {
+	if prefix != "" {
+		prefix += "."
+	}
+	if len(filters) == 0 {
+		return "", true
+	}
+
+	filters, ok = filters.validate(validFilters)
+	if !ok {
+		return "", ok
+	}
+
+	for k, v := range filters {
+		if res != "" {
+			res += " and "
+		} else {
+			res += " where "
+		}
+		res += fmt.Sprintf("%s%s = '%s'", prefix, k, v)
+	}
+
+	return res, ok
+}
-- 
1.8.1.2