code that works

pkg/tmpfile/tmpfile.go

@@ -0,0 +1,47 @@
+package tmpfile
+
+import (
+	"math/rand"
+	"os"
+	"strings"
+
+	"git.burning.moe/celediel/agedit/pkg/env"
+)
+
+const chars string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
+
+type Generator struct {
+	Prefix, Suffix string
+	Length         int
+}
+
+// GenerateName generates a random temporary filename like agedit_geef0XYC30RGV
+func (g *Generator) GenerateName() string {
+	return g.Prefix + randomString(chars, g.Length) + g.Suffix
+}
+
+// GenerateFullPath generates a random temporary filename and appends it to the OS's temporary directory
+func (g *Generator) GenerateFullPath() string {
+	return env.GetTempDirectory() + string(os.PathSeparator) + g.GenerateName()
+}
+
+// NewGenerator returns a new Generator
+func NewGenerator(prefix, suffix string, length int) Generator {
+	return Generator{
+		Prefix: prefix,
+		Suffix: suffix,
+		Length: length,
+	}
+}
+
+func randomString(set string, length int) string {
+	out := strings.Builder{}
+	for i := 0; i < length; i++ {
+		out.WriteByte(randomChar(set))
+	}
+	return out.String()
+}
+
+func randomChar(set string) byte {
+	return set[rand.Intn(len(set))]
+}

pkg/tmpfile/tmpfile_test.go

@@ -0,0 +1,43 @@
+package tmpfile
+
+import (
+	"io/fs"
+	"os"
+	"testing"
+)
+
+var generator = NewGenerator("test_", ".txt", 18)
+
+// TestCanCreateTmpFile tests if temporary files can be created and removed successfully
+func TestCanCreateTmpFile(t *testing.T) {
+	b := []byte{104, 101, 108, 108, 111, 32, 116, 104, 101, 114, 101}
+
+	for range 1000 {
+		outfile := generator.GenerateFullPath()
+		err := os.WriteFile(outfile, b, fs.FileMode(0600))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if _, err = os.Stat(outfile); err != nil && os.IsNotExist(err) {
+			t.Fatal(err)
+		}
+
+		if err = os.Remove(outfile); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+// TestUniqueTmpFile generates a large number of random names to make sure they're all unique
+func TestUniqueTmpFile(t *testing.T) {
+	var generated_names = map[string]string{}
+
+	for range 100000 {
+		name := generator.GenerateName()
+		if val, ok := generated_names[name]; ok {
+			t.Fatal("Non unique name", val)
+		}
+		generated_names[name] = name
+	}
+}