package main

import (
	"errors"
	"flag"
	"fmt"
	"os"

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

type repo struct {
	bare bool

	*dehub.Repo
}

func (r *repo) initFlags(flag *flag.FlagSet) {
	flag.BoolVar(&r.bare, "bare", false, "If set then the repo being opened will be expected to be bare")
}

func (r *repo) openRepo() error {
	var err error
	if r.Repo, err = dehub.OpenRepo(".", dehub.OpenBare(r.bare)); err != nil {
		wd, _ := os.Getwd()
		return fmt.Errorf("opening repo at %q: %w", wd, err)
	}
	return nil
}

// softReset resets to HEAD^ (or to an orphaned index, if HEAD has no parents),
// returning the old HEAD.
func (r *repo) softReset(expType string) (dehub.GitCommit, error) {
	head, err := r.GetGitHead()
	if err != nil {
		return head, fmt.Errorf("getting HEAD commit: %w", err)
	} else if typ, err := head.Commit.Type(); err != nil {
		return head, fmt.Errorf("determining commit type of HEAD:% w", err)
	} else if expType != "" && typ != expType {
		return head, fmt.Errorf("expected HEAD to be a %q commit, but found %q",
			expType, typ)
	}

	branchName, branchErr := r.ReferenceToBranchName(plumbing.HEAD)
	numParents := head.GitCommit.NumParents()
	if numParents > 1 {
		return head, errors.New("cannot reset to parent of a commit with multiple parents")

	} else if numParents == 0 {
		// if there are no parents then HEAD is the only commit in the branch.
		// Don't handle ErrNoBranchReference because there's not really anything
		// which can be done for that; we can't set head to "no commit".
		// Otherwise, just remove the branch reference, HEAD will still point to
		// it and all of HEAD's changes will be in the index.
		if branchErr != nil {
			return head, branchErr
		} else if err := r.GitRepo.Storer.RemoveReference(branchName); err != nil {
			return head, fmt.Errorf("removing reference %q: %w", branchName, err)
		}
		return head, nil
	}

	refName := branchName
	if errors.Is(branchErr, dehub.ErrNoBranchReference) {
		refName = plumbing.HEAD
	} else if err != nil {
		return head, fmt.Errorf("resolving HEAD: %w", err)
	}

	parentHash := head.GitCommit.ParentHashes[0]
	newHeadRef := plumbing.NewHashReference(refName, parentHash)
	if err := r.GitRepo.Storer.SetReference(newHeadRef); err != nil {
		return head, fmt.Errorf("storing reference %q: %w", newHeadRef, err)
	}
	return head, nil
}