Query piped nodes when counting with -R/-F (#22)

With piped input, `-C` skipped the query and counted the piped lines' second column, so `... | node-lookup -R -C` reported the upstream fact instead of each node's role.

- query each piped node for `-R`/`-F` with `-C` and count the results
- count piped lines directly only for bare `-C` with piped input; `-C` with `-j`/`-1`/`-2` still requires `-R`/`-F`
- validate flags before reading stdin so invalid combos never block on an open pipe
- add tests for piped count paths, rejected combos and validation ordering

Reviewed-on: #22
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

main.go

@@ -357,15 +357,38 @@ func run(cfg config, nodeName, factName, match string, showRole, partial, invers
 		return nil
 	}
 
-	if (nodeOnly || valueOnly || count || ansible) && !showRole && factName == "" {
-		return fmt.Errorf("-R or -F must be used with -1, -2, -C, or -A")
+	hasQuery := showRole || factName != ""
+	// Bare -C counts already-looked-up piped lines; only it needs stdin to validate.
+	bareCount := count && !hasQuery && !nodeOnly && !valueOnly && !ansible && !jsonMode && nodeName == ""
+	countErr := fmt.Errorf("-R or -F must be used with -1, -2, -C, or -A")
+
+	if (nodeOnly || valueOnly || (count && !bareCount) || ansible) && !hasQuery {
+		return countErr
 	}
-	if (match != "" || partial || inverse) && !showRole && factName == "" {
+	if (match != "" || partial || inverse) && !hasQuery {
 		return fmt.Errorf("-R or -F must be used with -m, -p, or -i")
 	}
 
+	var reader *bufio.Reader
+	piped := false
+	if nodeName == "" {
+		reader, piped = stdinReader(os.Stdin)
+	}
+
+	if bareCount {
+		if !piped {
+			return countErr
+		}
+		var lines []string
+		scanner := bufio.NewScanner(reader)
+		for scanner.Scan() {
+			lines = append(lines, scanner.Text())
+		}
+		fmt.Println(strings.Join(countResults(lines), "\n"))
+		return nil
+	}
+
 	var collected []fact
-	var stdinLines []string
 
 	doQuery := func(node string) error {
 		query := buildQuery(node, factName, match, cfg.RoleFact, showRole, partial, inverse)
@@ -377,21 +400,15 @@ func run(cfg config, nodeName, factName, match string, showRole, partial, invers
 		return nil
 	}
 
-	if reader, ok := stdinReader(os.Stdin); ok && nodeName == "" {
+	if piped {
 		scanner := bufio.NewScanner(reader)
-		if count {
-			for scanner.Scan() {
-				stdinLines = append(stdinLines, scanner.Text())
+		for scanner.Scan() {
+			fields := strings.Fields(scanner.Text())
+			if len(fields) == 0 {
+				continue
 			}
-		} else {
-			for scanner.Scan() {
-				fields := strings.Fields(scanner.Text())
-				if len(fields) == 0 {
-					continue
-				}
-				if err := doQuery(qualifyNode(fields[0], cfg.Domain)); err != nil {
-					fmt.Fprintln(os.Stderr, "error:", err)
-				}
+			if err := doQuery(qualifyNode(fields[0], cfg.Domain)); err != nil {
+				fmt.Fprintln(os.Stderr, "error:", err)
 			}
 		}
 	} else {
@@ -410,11 +427,7 @@ func run(cfg config, nodeName, factName, match string, showRole, partial, invers
 		_ = enc.Encode(factsByHost(collected, factName, cfg.RoleFact, showRole))
 
 	case count:
-		values := stdinLines
-		if len(values) == 0 {
-			values = returnData
-		}
-		fmt.Println(strings.Join(countResults(values), "\n"))
+		fmt.Println(strings.Join(countResults(returnData), "\n"))
 
 	case ansible:
 		// Attach each host's queried fact(s) as inventory host vars, e.g.