package git

import (
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
	"strings"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
)

type Repo struct {
	path string
	Meta RepoMeta
}

func (r Repo) Name() string {
	return strings.TrimSuffix(filepath.Base(r.path), ".git")
}

func NewRepo(dir, name string) (*Repo, error) {
	if !strings.HasSuffix(name, ".git") {
		name += ".git"
	}
	r := &Repo{
		path: filepath.Join(dir, name),
	}

	_, err := os.Stat(r.path)
	if err != nil {
		return nil, err
	}

	if err := ensureJSONFile(r.metaPath()); err != nil {
		return nil, err
	}
	fi, err := os.Open(r.metaPath())
	if err != nil {
		return nil, err
	}
	defer fi.Close()

	if err := json.NewDecoder(fi).Decode(&r.Meta); err != nil {
		return nil, err
	}

	return r, nil
}

// DefaultBranch returns the branch referenced by HEAD, setting it if needed
func (r Repo) DefaultBranch() (string, error) {
	repo, err := r.Git()
	if err != nil {
		return "", err
	}

	ref, err := repo.Head()
	if err != nil {
		if !errors.Is(err, plumbing.ErrReferenceNotFound) {
			return "", err
		}
		brs, err := repo.Branches()
		if err != nil {
			return "", err
		}
		defer brs.Close()
		fb, err := brs.Next()
		if err != nil {
			return "", err
		}
		// Rename the default branch to the first branch available
		ref = fb
		sym := plumbing.NewSymbolicReference(plumbing.HEAD, fb.Name())
		if err := repo.Storer.SetReference(sym); err != nil {
			return "", err
		}
	}

	return strings.TrimPrefix(ref.Name().String(), "refs/heads/"), nil
}

// Git allows access to the git repository
func (r Repo) Git() (*git.Repository, error) {
	return git.PlainOpen(r.path)
}

// LastCommit returns the last commit of the repo
func (r Repo) LastCommit() (*object.Commit, error) {
	repo, err := r.Git()
	if err != nil {
		return nil, err
	}

	head, err := repo.Head()
	if err != nil {
		return nil, err
	}

	return repo.CommitObject(head.Hash())
}