Pull request: all: fix lint and naming issues

Merge in DNS/adguard-home from 2276-fix-lint to master

Updates #2276.

Squashed commit of the following:

commit 433f44cc7b674a20ed60a9d29466ba888b3ef66e
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 7 14:14:28 2020 +0300

    querylog: improve code and documentation

commit 851df97d2a87de5e7180a502055ee6f1a6defdca
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 4 20:36:32 2020 +0300

    all: fix lint and naming issues

internal/querylog/searchparams.go

@@ -0,0 +1,57 @@
+package querylog
+
+import "time"
+
+// searchParams represent the search query sent by the client
+type searchParams struct {
+	// searchCriteria - list of search criteria that we use to get filter results
+	searchCriteria []searchCriteria
+
+	// olderThen - return entries that are older than this value
+	// if not set - disregard it and return any value
+	olderThan time.Time
+
+	offset             int // offset for the search
+	limit              int // limit the number of records returned
+	maxFileScanEntries int // maximum log entries to scan in query log files. if 0 - no limit
+}
+
+// newSearchParams - creates an empty instance of searchParams
+func newSearchParams() *searchParams {
+	return &searchParams{
+		// default max log entries to return
+		limit: 500,
+
+		// by default, we scan up to 50k entries at once
+		maxFileScanEntries: 50000,
+	}
+}
+
+// quickMatchesGetDataParams - quickly checks if the line matches the searchParams
+// this method does not guarantee anything and the reason is to do a quick check
+// without deserializing anything
+func (s *searchParams) quickMatch(line string) bool {
+	for _, c := range s.searchCriteria {
+		if !c.quickMatch(line) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// match - checks if the logEntry matches the searchParams
+func (s *searchParams) match(entry *logEntry) bool {
+	if !s.olderThan.IsZero() && entry.Time.UnixNano() >= s.olderThan.UnixNano() {
+		// Ignore entries newer than what was requested
+		return false
+	}
+
+	for _, c := range s.searchCriteria {
+		if !c.match(entry) {
+			return false
+		}
+	}
+
+	return true
+}