package git

import "errors"
import "strings"

import git "github.com/go-git/go-git/v5"
import "github.com/go-git/go-git/v5/plumbing"
import "github.com/go-git/go-git/v5/plumbing/object"
import "github.com/go-git/go-git/v5/plumbing/storer"

func GetDefaultBranch(repoPath string) (string, error) {
	var repo *git.Repository
	var err error
	var head *plumbing.Reference
	var target plumbing.ReferenceName
	var targetRef *plumbing.Reference
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return "", err
	}
	_ = EnsureHead(repoPath)
	head, err = repo.Reference(plumbing.HEAD, false)
	if err != nil {
		return "", err
	}
	if head.Type() == plumbing.SymbolicReference {
		target = head.Target()
		targetRef, err = repo.Reference(target, true)
		if err != nil {
			if errors.Is(err, plumbing.ErrReferenceNotFound) {
				return "", nil
			}
			return "", err
		}
		if targetRef.Hash().IsZero() {
			return "", nil
		}
		return target.Short(), nil
	}
	return head.Name().Short(), nil
}

type BranchInfo struct {
	Name        string `json:"name"`
	LastHash    string `json:"last_hash"`
	LastAuthor  string `json:"last_author"`
	LastWhen    string `json:"last_when"`
	LastMessage string `json:"last_message"`
}

func ListBranchInfos(repoPath string) ([]BranchInfo, error) {
	var repo *git.Repository
	var err error
	var iter storer.ReferenceIter
	var branches []BranchInfo
	var ref *plumbing.Reference
	var commit *object.Commit
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return nil, err
	}
	iter, err = repo.Branches()
	if err != nil {
		return nil, err
	}
	defer iter.Close()
	err = iter.ForEach(func(r *plumbing.Reference) error {
		ref = r
		if ref.Hash().IsZero() {
			return nil
		}
		commit, err = repo.CommitObject(ref.Hash())
		if err != nil {
			branches = append(branches, BranchInfo{Name: ref.Name().Short()})
			return nil
		}
		branches = append(branches, BranchInfo{
			Name:        ref.Name().Short(),
			LastHash:    commit.Hash.String(),
			LastAuthor:  commit.Author.Name,
			LastWhen:    commit.Author.When.UTC().Format(timeFormat),
			LastMessage: strings.TrimSpace(commit.Message),
		})
		return nil
	})
	if err != nil {
		return nil, err
	}
	return branches, nil
}

func SetDefaultBranch(repoPath string, branch string) error {
	var repo *git.Repository
	var err error
	var refName plumbing.ReferenceName
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return err
	}
	refName = plumbing.NewBranchReferenceName(branch)
	_, err = repo.Reference(refName, true)
	if err != nil {
		return err
	}
	err = repo.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, refName))
	return err
}

func CreateBranch(repoPath string, name string, from string) error {
	var repo *git.Repository
	var err error
	var commit *object.Commit
	var refName plumbing.ReferenceName
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return err
	}
	refName = plumbing.NewBranchReferenceName(name)
	_, err = repo.Reference(refName, true)
	if err == nil {
		return err
	}
	commit, err = resolveCommit(repo, from)
	if err != nil {
		return err
	}
	err = repo.Storer.SetReference(plumbing.NewHashReference(refName, commit.Hash))
	return err
}

func DeleteBranch(repoPath string, branch string) error {
	var repo *git.Repository
	var err error
	var refName plumbing.ReferenceName
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return err
	}
	refName = plumbing.NewBranchReferenceName(branch)
	err = repo.Storer.RemoveReference(refName)
	return err
}

func RenameBranch(repoPath string, from string, to string) error {
	var repo *git.Repository
	var err error
	var fromRef *plumbing.Reference
	var toRefName plumbing.ReferenceName
	var fromRefName plumbing.ReferenceName
	var head *plumbing.Reference
	if from == to {
		return nil
	}
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return err
	}
	fromRefName = plumbing.NewBranchReferenceName(from)
	toRefName = plumbing.NewBranchReferenceName(to)
	fromRef, err = repo.Reference(fromRefName, true)
	if err != nil {
		return err
	}
	err = repo.Storer.SetReference(plumbing.NewHashReference(toRefName, fromRef.Hash()))
	if err != nil {
		return err
	}
	head, err = repo.Reference(plumbing.HEAD, false)
	if err == nil && head.Type() == plumbing.SymbolicReference && head.Target() == fromRefName {
		_ = repo.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, toRefName))
	}
	err = repo.Storer.RemoveReference(fromRefName)
	return err
}

func EnsureHead(repoPath string) error {
	var repo *git.Repository
	var err error
	var head *plumbing.Reference
	var target plumbing.ReferenceName
	var refName plumbing.ReferenceName
	var iter storer.ReferenceIter
	var first *plumbing.Reference
	repo, err = git.PlainOpen(repoPath)
	if err != nil {
		return err
	}
	head, err = repo.Reference(plumbing.HEAD, false)
	if err == nil {
		if head.Type() == plumbing.SymbolicReference {
			target = head.Target()
			_, err = repo.Reference(target, true)
			if err == nil {
				return nil
			}
		} else {
			return nil
		}
	}
	refName = plumbing.NewBranchReferenceName("main")
	_, err = repo.Reference(refName, true)
	if err == nil {
		return repo.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, refName))
	}
	refName = plumbing.NewBranchReferenceName("master")
	_, err = repo.Reference(refName, true)
	if err == nil {
		return repo.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, refName))
	}
	iter, err = repo.Branches()
	if err != nil {
		return err
	}
	defer iter.Close()
	err = iter.ForEach(func(r *plumbing.Reference) error {
		first = r
		return storer.ErrStop
	})
	if err != nil && err != storer.ErrStop {
		return err
	}
	if first == nil {
		return nil
	}
	return repo.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, first.Name()))
}