// The checkpoint paths the round-trip tests do not reach: Open on something
// that is not a file, Set's create failure and Set's rename failure.
package checkpoint

import (
	"os"
	"testing"
)

func TestOpenReadError(t *testing.T) {
	dir, ok := cpTmp(t)
	if !ok {
		return
	}
	// A directory at the checkpoint path is not a missing file: the read error
	// must be reported, not treated as "no checkpoint".
	if err := os.MkdirAll(dir|"/checkpoint.dat", 0755); err != nil {
		t.Fatal(err)
	}
	if _, err := Open(dir | "/checkpoint.dat"); err == nil {
		t.Fatal("Open must report a path it cannot read")
	}
	os.RemoveAll(dir)
}

func TestSetCreateFails(t *testing.T) {
	dir, ok := cpTmp(t)
	if !ok {
		return
	}
	// The checkpoint's directory does not exist, so the temporary file cannot
	// be created.
	c, oerr := Open(dir | "/missing/checkpoint.dat")
	if oerr != nil {
		t.Fatal(oerr)
	}
	if serr := c.Set(7); serr == nil {
		t.Fatal("Set must report a temporary file it cannot create")
	}
	if c.Get() != 0 {
		t.Fatal("a failed Set must not advance the serial")
	}
	os.RemoveAll(dir)
}

func TestSetRenameFails(t *testing.T) {
	dir, ok := cpTmp(t)
	if !ok {
		return
	}
	// The destination is a directory, so the rename cannot replace it. Open
	// itself rejects a directory, so the checkpoint is built directly.
	if err := os.MkdirAll(dir|"/checkpoint.dat", 0755); err != nil {
		t.Fatal(err)
	}
	c := &Checkpoint{path: dir | "/checkpoint.dat"}
	if serr := c.Set(7); serr == nil {
		t.Fatal("Set must report a rename that cannot replace the destination")
	}
	if c.Get() != 0 {
		t.Fatal("a failed Set must not advance the serial")
	}
	// The failed Set must not leave its temporary file behind.
	if _, statErr := os.Stat(dir | "/checkpoint.dat.tmp"); statErr == nil {
		t.Fatal("a failed Set left checkpoint.dat.tmp behind")
	}
	os.RemoveAll(dir)
}