package git

import (
	"context"
	"errors"

	"github.com/go-git/go-billy/v5"
	"github.com/go-git/go-billy/v5/memfs"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/transport"
	"github.com/go-git/go-git/v5/plumbing/transport/http"
	"github.com/go-git/go-git/v5/storage/memory"
)

type ProjectOption func(*Project)

func WithBasicAuth(user, pass string) ProjectOption {
	return func(p *Project) {
		p.auth = &http.BasicAuth{
			Username: user,
			Password: pass,
		}
	}
}

func WithBranch(branch string) ProjectOption {
	return func(p *Project) {
		p.Branch = branch
	}
}

type Project struct {
	Branch  string
	Force   bool
	RepoURL string

	auth       transport.AuthMethod
	fs         billy.Filesystem
	storer     *memory.Storage
	repository *git.Repository
	worktree   *git.Worktree
}

func NewProject(url string, options ...ProjectOption) *Project {
	project := &Project{
		RepoURL:    url,
		fs:         memfs.New(),
		storer:     memory.NewStorage(),
		repository: nil,
	}

	for _, option := range options {
		option(project)
	}

	return project
}

func (p *Project) Checkout() error {
	branchRef := plumbing.NewBranchReferenceName(p.Branch)

	_, err := p.repository.Reference(branchRef, true)
	if errors.Is(err, plumbing.ErrReferenceNotFound) {
		var headRef *plumbing.Reference
		headRef, err = p.repository.Head()
		if err != nil {
			return err
		}

		ref := plumbing.NewHashReference(branchRef, headRef.Hash())
		if err = p.repository.Storer.SetReference(ref); err != nil {
			return err
		}
	} else if err != nil {
		return err
	}

	p.worktree, err = p.repository.Worktree()
	if err != nil {
		return err
	}

	checkoutOpts := git.CheckoutOptions{
		Branch: branchRef,
		Create: false,
	}

	if err = checkoutOpts.Validate(); err != nil {
		return err
	}

	return p.worktree.Checkout(&checkoutOpts)
}

func (p *Project) Clone(ctx context.Context) error {
	cloneOpts := git.CloneOptions{
		URL:               p.RepoURL,
		RecurseSubmodules: git.DefaultSubmoduleRecursionDepth,
	}

	if p.auth != nil {
		cloneOpts.Auth = p.auth
	}

	if err := cloneOpts.Validate(); err != nil {
		return err
	}

	var err error
	p.repository, err = git.CloneContext(
		ctx,
		p.storer,
		p.fs,
		&cloneOpts,
	)
	if err != nil {
		return err
	}

	return nil
}

func (p *Project) HasChanges() bool {
	remoteBranchRef := plumbing.NewRemoteReferenceName("origin", p.Branch)
	remoteBranch, err := p.repository.Reference(remoteBranchRef, true)
	if errors.Is(err, plumbing.ErrReferenceNotFound) {
		return true
	} else if err != nil {
		return false
	}

	localBranchRef, err := p.repository.Reference(plumbing.NewBranchReferenceName(p.Branch), true)
	if err != nil {
		return false
	}

	if localBranchRef.Hash() != remoteBranch.Hash() {
		return true
	}

	return false
}

func (p *Project) Pull(ctx context.Context) error {
	pullOpts := git.PullOptions{
		ReferenceName: plumbing.NewBranchReferenceName(p.Branch),
	}

	if err := pullOpts.Validate(); err != nil {
		return err
	}

	err := p.worktree.PullContext(ctx, &pullOpts)
	if !errors.Is(err, plumbing.ErrReferenceNotFound) && err != nil {
		return err
	}

	return nil
}

func (p *Project) Push(ctx context.Context) error {
	pushOpts := git.PushOptions{
		RemoteName: "origin",
	}

	if p.auth != nil {
		pushOpts.Auth = p.auth
	}

	if err := pushOpts.Validate(); err != nil {
		return err
	}

	return p.repository.PushContext(ctx, &pushOpts)
}