courier: Rename Procmail to MDA

This patch renames courier.Procmail to courier.MDA, to make it more
obvious that the functionality is not tied to that particular MDA.

It's just for readability, there are no functional changes.

internal/courier/mda_test.go

@@ -0,0 +1,124 @@
+package courier
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+
+	"blitiri.com.ar/go/chasquid/internal/testlib"
+)
+
+func TestMDA(t *testing.T) {
+	dir := testlib.MustTempDir(t)
+	defer testlib.RemoveIfOk(t, dir)
+
+	p := MDA{
+		Binary:  "tee",
+		Args:    []string{dir + "/%to_user%"},
+		Timeout: 1 * time.Minute,
+	}
+
+	err, _ := p.Deliver("from@x", "to@local", []byte("data"))
+	if err != nil {
+		t.Fatalf("Deliver: %v", err)
+	}
+
+	data, err := ioutil.ReadFile(dir + "/to")
+	if err != nil || !bytes.Equal(data, []byte("data")) {
+		t.Errorf("Invalid data: %q - %v", string(data), err)
+	}
+}
+
+func TestMDATimeout(t *testing.T) {
+	p := MDA{"/bin/sleep", []string{"1"}, 100 * time.Millisecond}
+
+	err, permanent := p.Deliver("from", "to@local", []byte("data"))
+	if err != errTimeout {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if permanent {
+		t.Errorf("expected transient, got permanent")
+	}
+}
+
+func TestMDABadCommandLine(t *testing.T) {
+	// Non-existent binary.
+	p := MDA{"thisdoesnotexist", nil, 1 * time.Minute}
+	err, permanent := p.Deliver("from", "to", []byte("data"))
+	if err == nil {
+		t.Errorf("unexpected success for non-existent binary")
+	}
+	if !permanent {
+		t.Errorf("expected permanent, got transient")
+	}
+
+	// Incorrect arguments.
+	p = MDA{"cat", []string{"--fail_unknown_option"}, 1 * time.Minute}
+	err, _ = p.Deliver("from", "to", []byte("data"))
+	if err == nil {
+		t.Errorf("unexpected success for incorrect arguments")
+	}
+}
+
+// Test that local delivery failures are considered permanent or not
+// according to the exit code.
+func TestExitCode(t *testing.T) {
+	// TODO: This can happen when building under unusual circumstances, such
+	// as Debian package building. Are they reasonable enough for us to keep
+	// this?
+	if _, err := os.Stat("../../test/util/exitcode"); os.IsNotExist(err) {
+		t.Skipf("util/exitcode not found, running from outside repo?")
+	}
+
+	cases := []struct {
+		cmd             string
+		args            []string
+		expectPermanent bool
+	}{
+		{"does/not/exist", nil, true},
+		{"../../test/util/exitcode", []string{"1"}, true},
+		{"../../test/util/exitcode", []string{"75"}, false},
+	}
+	for _, c := range cases {
+		p := &MDA{c.cmd, c.args, 5 * time.Second}
+		err, permanent := p.Deliver("from", "to", []byte("data"))
+		if err == nil {
+			t.Errorf("%q: pipe delivery worked, expected failure", c.cmd)
+		}
+		if c.expectPermanent != permanent {
+			t.Errorf("%q: permanent expected=%v, got=%v",
+				c.cmd, c.expectPermanent, permanent)
+		}
+	}
+}
+
+func TestSanitize(t *testing.T) {
+	cases := []struct{ v, expected string }{
+		// These are the same.
+		{"thisisfine", "thisisfine"},
+		{"ñaca", "ñaca"},
+		{"123-456_789", "123-456_789"},
+		{"123+456~789", "123+456~789"},
+
+		// These have problematic characters that get dropped.
+		{"with spaces", "withspaces"},
+		{"with/slash", "withslash"},
+		{"quote';andsemicolon", "quoteandsemicolon"},
+		{"a;b", "ab"},
+		{`"test"`, "test"},
+
+		// Interesting cases taken from
+		// http://www.user.uni-hannover.de/nhtcapri/bidirectional-text.html
+		// We allow them, they're the same on both sides.
+		{"١٩٩٩–١٢–٣١", "١٩٩٩–١٢–٣١"},
+		{"موزه‌ها", "موزه\u200cها"},
+	}
+	for _, c := range cases {
+		out := sanitizeForMDA(c.v)
+		if out != c.expected {
+			t.Errorf("%q: expected %q, got %q", c.v, c.expected, out)
+		}
+	}
+}