2 files changed, 208 insertions, 0 deletions
diff --git a/commands/bug/select/select.go b/commands/bug/select/select.go
new file mode 100644
index 00000000..908ad58c
--- /dev/null
+++ b/commands/bug/select/select.go
@@ -0,0 +1,129 @@
+package _select
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+
+	"github.com/pkg/errors"
+
+	"github.com/MichaelMure/git-bug/cache"
+	"github.com/MichaelMure/git-bug/entities/bug"
+	"github.com/MichaelMure/git-bug/entity"
+)
+
+const selectFile = "select"
+
+var ErrNoValidId = errors.New("you must provide a bug id or use the \"select\" command first")
+
+// ResolveBug first try to resolve a bug using the first argument of the command
+// line. If it fails, it fallback to the select mechanism.
+//
+// Returns:
+// - the bug if any
+// - the new list of command line arguments with the bug prefix removed if it
+//   has been used
+// - an error if the process failed
+func ResolveBug(repo *cache.RepoCache, args []string) (*cache.BugCache, []string, error) {
+	// At first, try to use the first argument as a bug prefix
+	if len(args) > 0 {
+		b, err := repo.ResolveBugPrefix(args[0])
+
+		if err == nil {
+			return b, args[1:], nil
+		}
+
+		if err != bug.ErrBugNotExist {
+			return nil, nil, err
+		}
+	}
+
+	// first arg is not a valid bug prefix, we can safely use the preselected bug if any
+
+	b, err := selected(repo)
+
+	// selected bug is invalid
+	if err == bug.ErrBugNotExist {
+		// we clear the selected bug
+		err = Clear(repo)
+		if err != nil {
+			return nil, nil, err
+		}
+		return nil, nil, ErrNoValidId
+	}
+
+	// another error when reading the bug
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// bug is successfully retrieved
+	if b != nil {
+		return b, args, nil
+	}
+
+	// no selected bug and no valid first argument
+	return nil, nil, ErrNoValidId
+}
+
+// Select will select a bug for future use
+func Select(repo *cache.RepoCache, id entity.Id) error {
+	f, err := repo.LocalStorage().OpenFile(selectFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
+	if err != nil {
+		return err
+	}
+
+	_, err = f.Write([]byte(id.String()))
+	if err != nil {
+		return err
+	}
+
+	return f.Close()
+}
+
+// Clear will clear the selected bug, if any
+func Clear(repo *cache.RepoCache) error {
+	return repo.LocalStorage().Remove(selectFile)
+}
+
+func selected(repo *cache.RepoCache) (*cache.BugCache, error) {
+	f, err := repo.LocalStorage().Open(selectFile)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		} else {
+			return nil, err
+		}
+	}
+
+	buf, err := ioutil.ReadAll(io.LimitReader(f, 100))
+	if err != nil {
+		return nil, err
+	}
+	if len(buf) == 100 {
+		return nil, fmt.Errorf("the select file should be < 100 bytes")
+	}
+
+	id := entity.Id(buf)
+	if err := id.Validate(); err != nil {
+		err = repo.LocalStorage().Remove(selectFile)
+		if err != nil {
+			return nil, errors.Wrap(err, "error while removing invalid select file")
+		}
+
+		return nil, fmt.Errorf("select file in invalid, removing it")
+	}
+
+	b, err := repo.ResolveBug(id)
+	if err != nil {
+		return nil, err
+	}
+
+	err = f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+}
diff --git a/commands/bug/select/select_test.go b/commands/bug/select/select_test.go
new file mode 100644
index 00000000..702700f4
--- /dev/null
+++ b/commands/bug/select/select_test.go
@@ -0,0 +1,79 @@
+package _select
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/MichaelMure/git-bug/cache"
+	"github.com/MichaelMure/git-bug/repository"
+)
+
+func TestSelect(t *testing.T) {
+	repo := repository.CreateGoGitTestRepo(t, false)
+
+	repoCache, err := cache.NewRepoCache(repo)
+	require.NoError(t, err)
+
+	_, _, err = ResolveBug(repoCache, []string{})
+	require.Equal(t, ErrNoValidId, err)
+
+	err = Select(repoCache, "invalid")
+	require.NoError(t, err)
+
+	// Resolve without a pattern should fail when no bug is selected
+	_, _, err = ResolveBug(repoCache, []string{})
+	require.Error(t, err)
+
+	// generate a bunch of bugs
+
+	rene, err := repoCache.NewIdentity("René Descartes", "rene@descartes.fr")
+	require.NoError(t, err)
+
+	for i := 0; i < 10; i++ {
+		_, _, err := repoCache.NewBugRaw(rene, time.Now().Unix(), "title", "message", nil, nil)
+		require.NoError(t, err)
+	}
+
+	// and two more for testing
+	b1, _, err := repoCache.NewBugRaw(rene, time.Now().Unix(), "title", "message", nil, nil)
+	require.NoError(t, err)
+	b2, _, err := repoCache.NewBugRaw(rene, time.Now().Unix(), "title", "message", nil, nil)
+	require.NoError(t, err)
+
+	err = Select(repoCache, b1.Id())
+	require.NoError(t, err)
+
+	// normal select without args
+	b3, _, err := ResolveBug(repoCache, []string{})
+	require.NoError(t, err)
+	require.Equal(t, b1.Id(), b3.Id())
+
+	// override selection with same id
+	b4, _, err := ResolveBug(repoCache, []string{b1.Id().String()})
+	require.NoError(t, err)
+	require.Equal(t, b1.Id(), b4.Id())
+
+	// override selection with a prefix
+	b5, _, err := ResolveBug(repoCache, []string{b1.Id().Human()})
+	require.NoError(t, err)
+	require.Equal(t, b1.Id(), b5.Id())
+
+	// args that shouldn't override
+	b6, _, err := ResolveBug(repoCache, []string{"arg"})
+	require.NoError(t, err)
+	require.Equal(t, b1.Id(), b6.Id())
+
+	// override with a different id
+	b7, _, err := ResolveBug(repoCache, []string{b2.Id().String()})
+	require.NoError(t, err)
+	require.Equal(t, b2.Id(), b7.Id())
+
+	err = Clear(repoCache)
+	require.NoError(t, err)
+
+	// Resolve without a pattern should error again after clearing the selected bug
+	_, _, err = ResolveBug(repoCache, []string{})
+	require.Error(t, err)
+}