package dehub

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

	"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 := new(object.Tree)
	if head, err := r.GetGitHead(); err != nil && !errors.Is(err, ErrHeadIsZero) {
		return Commit{}, fmt.Errorf("getting HEAD commit: %w", err)
	} else if err == nil {
		headTree = head.GitTree
	}

	_, 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(CommitCommon) (string, error) {
	return abbrevCommitMessage(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
}