package main

import (
	"os"
	"strings"
	"testing"
)

// **The genesis path writes its result to stdout and nothing else there.** The installer captures
// stdout alone and parses it as JSON; one stray log line makes that fail with "invalid character"
// — exactly what a builder fmt.Printf caused, breaking a build that had worked. This keeps
// diagnostics on stderr so a future print cannot repeat it silently.
func TestBuilderDiagnosticsStayOffStdout(t *testing.T) {
	allowed := map[string]bool{
		"string(body)": true, // once.go: the result JSON, which IS stdout
		"version)":     true, // --version
		`"stopping")`: true,  // the loop.s shutdown line
		"usage)":       true,  // --help text, for a human
	}
	for _, file := range []string{"once.go", "main.go"} {
		src, err := os.ReadFile(file)
		if err != nil {
			t.Fatal(err)
		}
		for i, raw := range strings.Split(string(src), "\n") {
			line := strings.TrimSpace(raw)
			if !strings.HasPrefix(line, "fmt.Printf(") &&
				!strings.HasPrefix(line, "fmt.Println(") &&
				!strings.HasPrefix(line, "fmt.Print(") {
				continue
			}
			ok := false
			for token := range allowed {
				if strings.Contains(line, token) {
					ok = true
				}
			}
			if !ok {
				t.Errorf("%s:%d writes a diagnostic to stdout, which the installer parses as JSON:\n  %s",
					file, i+1, line)
			}
		}
	}
}