package dehub

import (
	"dehub/fs"
	"dehub/yamlutil"
	"errors"
	"strings"

	"gopkg.in/src-d/go-git.v4/plumbing"
	"gopkg.in/src-d/go-git.v4/plumbing/object"
)

// CommitChange describes the structure of a change commit message.
type CommitChange struct {
	Message    string        `yaml:"message"`
	ChangeHash yamlutil.Blob `yaml:"change_hash"`
}

var _ CommitInterface = CommitChange{}

// NewCommitChange constructs a Commit populated with a CommitChange
// encompassing the currently staged file changes. The Credentials of the
// returned Commit will _not_ be filled in.
func (r *Repo) NewCommitChange(msg string) (Commit, error) {
	_, headTree, err := r.head()
	if errors.Is(err, plumbing.ErrReferenceNotFound) {
		headTree = &object.Tree{}
	} else if err != nil {
		return Commit{}, err
	}

	_, stagedTree, err := fs.FromStagedChangesTree(r.GitRepo)
	if err != nil {
		return Commit{}, err
	}

	cc := CommitChange{Message: msg}
	if cc.ChangeHash, err = cc.Hash(headTree, stagedTree); err != nil {
		return Commit{}, err
	}

	return Commit{
		Change: &cc,
	}, nil
}

// MessageHead implements the method for the CommitInterface interface.
func (cc CommitChange) MessageHead() (string, error) {
	i := strings.Index(cc.Message, "\n")
	if i > 0 {
		return cc.Message[:i], nil
	}
	return cc.Message, nil
}

// Hash implements the method for the CommitInterface interface.
func (cc CommitChange) Hash(parent, this *object.Tree) ([]byte, error) {
	return genChangeHash(nil, cc.Message, parent, this), nil
}

// GetHash implements the method for the CommitInterface interface.
func (cc CommitChange) GetHash() []byte {
	return cc.ChangeHash
}