package main

import (
	"errors"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing/object"
	gitHttp "github.com/go-git/go-git/v5/plumbing/transport/http"
	"io/ioutil"
	"os"
	"path"
	"sync"
	"time"
)

type Storage interface {
	CreateFile(path string, file string, message string) (err error)
	UpdateFile(path string, file string, message string) (err error)
	DeleteFile(path string, message string) (err error)
}

type Git struct {
	filepath string
	url      string
	username string
	password string
	name     string
	email    string
	lock     *sync.Mutex
}

func (g *Git) init() (r *git.Repository, w *git.Worktree, err error) {
	// Open repo
	r, err = git.PlainOpen(g.filepath)
	if err == nil {
		// Try to get work tree
		w, err = r.Worktree()
		if err == nil {
			// Try to pull
			err = w.Pull(&git.PullOptions{
				Auth: &gitHttp.BasicAuth{
					Username: g.username,
					Password: g.password,
				},
				SingleBranch: true,
			})
			if err == git.NoErrAlreadyUpToDate {
				err = nil
			}
		}
	}
	if err != nil {
		// Delete old things
		g.destroyRepo()
		// Clone
		r, err = git.PlainClone(g.filepath, false, &git.CloneOptions{
			Auth: &gitHttp.BasicAuth{
				Username: g.username,
				Password: g.password,
			},
			URL:          g.url,
			Depth:        1,
			SingleBranch: true,
		})
		if err != nil {
			err = errors.New("failed to clone repo")
		}
		if err == nil {
			w, err = r.Worktree()
			if err != nil {
				err = errors.New("failed to get work tree")
			}
		}
	}
	return
}

func (g *Git) destroyRepo() {
	_ = os.RemoveAll(g.filepath)
}

func (g *Git) push(repository *git.Repository) error {
	err := repository.Push(&git.PushOptions{
		Auth: &gitHttp.BasicAuth{
			Username: g.username,
			Password: g.password,
		},
	})
	if err == nil || err == git.NoErrAlreadyUpToDate {
		return nil
	} else {
		// Destroy repo to prevent errors when trying to create same post again
		g.destroyRepo()
		return errors.New("failed to push to remote")
	}
}

func (g *Git) CreateFile(filepath string, file string, message string) (err error) {
	g.lock.Lock()
	defer g.lock.Unlock()
	_, _, err = g.init()
	if err != nil {
		err = errors.New("failed to initialize repo")
		return
	}
	joinedPath := path.Join(g.filepath, filepath)
	if _, e := os.Stat(joinedPath); e == nil {
		return errors.New("file already exists")
	} else {
		return g.unsafeUpdateFile(filepath, file, message)
	}
}

func (g *Git) UpdateFile(filepath string, file string, message string) error {
	g.lock.Lock()
	defer g.lock.Unlock()
	return g.unsafeUpdateFile(filepath, file, message)
}

func (g *Git) unsafeUpdateFile(filepath string, file string, message string) error {
	repo, w, err := g.init()
	if err != nil {
		return errors.New("failed to initialize repo")
	}
	joinedPath := path.Join(g.filepath, filepath)
	_ = os.MkdirAll(path.Dir(joinedPath), 0755)
	err = ioutil.WriteFile(joinedPath, []byte(file), 0644)
	if err != nil {
		return errors.New("failed to write to file")
	}
	status, err := w.Status()
	if err == nil && status.IsClean() {
		// No file changes, prevent empty commit
		return nil
	} else {
		err = nil
	}
	_, err = w.Add(filepath)
	if err != nil {
		return errors.New("failed to stage file")
	}
	if len(message) == 0 {
		message = "Add " + filepath
	}
	_, err = w.Commit(message, &git.CommitOptions{
		Author: &object.Signature{
			Name:  g.name,
			Email: g.email,
			When:  time.Now(),
		},
	})
	if err != nil {
		return errors.New("failed to commit file")
	}
	return g.push(repo)
}

func (g *Git) DeleteFile(filepath string, message string) (err error) {
	g.lock.Lock()
	defer g.lock.Unlock()
	repo, w, err := g.init()
	if err != nil {
		return errors.New("failed to initialize repo")
	}
	joinedPath := path.Join(g.filepath, filepath)
	err = os.Remove(joinedPath)
	if err != nil {
		return errors.New("failed to delete file")
	}
	_, err = w.Add(filepath)
	if err != nil {
		return errors.New("failed to stage deletion")
	}
	_, err = w.Commit(message, &git.CommitOptions{
		Author: &object.Signature{
			Name:  g.name,
			Email: g.email,
			When:  time.Now(),
		},
	})
	if err != nil {
		return errors.New("failed to commit deletion")
	}
	return g.push(repo)
}