// Copyright 2019 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package repository

import (
	"context"
	"fmt"
	"strings"
	"time"

	"code.gitea.io/gitea/models/db"
	git_model "code.gitea.io/gitea/models/git"
	repo_model "code.gitea.io/gitea/models/repo"
	"code.gitea.io/gitea/models/unit"
	user_model "code.gitea.io/gitea/models/user"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/gitrepo"
	"code.gitea.io/gitea/modules/log"
	repo_module "code.gitea.io/gitea/modules/repository"
	"code.gitea.io/gitea/modules/structs"
	"code.gitea.io/gitea/modules/util"
	notify_service "code.gitea.io/gitea/services/notify"

	"xorm.io/builder"
)

// ErrForkAlreadyExist represents a "ForkAlreadyExist" kind of error.
type ErrForkAlreadyExist struct {
	Uname    string
	RepoName string
	ForkName string
}

// IsErrForkAlreadyExist checks if an error is an ErrForkAlreadyExist.
func IsErrForkAlreadyExist(err error) bool {
	_, ok := err.(ErrForkAlreadyExist)
	return ok
}

func (err ErrForkAlreadyExist) Error() string {
	return fmt.Sprintf("repository is already forked by user [uname: %s, repo path: %s, fork path: %s]", err.Uname, err.RepoName, err.ForkName)
}

func (err ErrForkAlreadyExist) Unwrap() error {
	return util.ErrAlreadyExist
}

// ForkRepoOptions contains the fork repository options
type ForkRepoOptions struct {
	BaseRepo     *repo_model.Repository
	Name         string
	Description  string
	SingleBranch string
}

// ForkRepository forks a repository
func ForkRepository(ctx context.Context, doer, owner *user_model.User, opts ForkRepoOptions) (*repo_model.Repository, error) {
	if err := opts.BaseRepo.LoadOwner(ctx); err != nil {
		return nil, err
	}

	if user_model.IsUserBlockedBy(ctx, doer, opts.BaseRepo.Owner.ID) {
		return nil, user_model.ErrBlockedUser
	}

	// Fork is prohibited, if user has reached maximum limit of repositories
	if !owner.CanForkRepo() {
		return nil, repo_model.ErrReachLimitOfRepo{
			Limit: owner.MaxRepoCreation,
		}
	}

	forkedRepo, err := repo_model.GetUserFork(ctx, opts.BaseRepo.ID, owner.ID)
	if err != nil {
		return nil, err
	}
	if forkedRepo != nil {
		return nil, ErrForkAlreadyExist{
			Uname:    owner.Name,
			RepoName: opts.BaseRepo.FullName(),
			ForkName: forkedRepo.FullName(),
		}
	}

	defaultBranch := opts.BaseRepo.DefaultBranch
	if opts.SingleBranch != "" {
		defaultBranch = opts.SingleBranch
	}
	repo := &repo_model.Repository{
		OwnerID:          owner.ID,
		Owner:            owner,
		OwnerName:        owner.Name,
		Name:             opts.Name,
		LowerName:        strings.ToLower(opts.Name),
		Description:      opts.Description,
		DefaultBranch:    defaultBranch,
		IsPrivate:        opts.BaseRepo.IsPrivate || opts.BaseRepo.Owner.Visibility == structs.VisibleTypePrivate,
		IsEmpty:          opts.BaseRepo.IsEmpty,
		IsFork:           true,
		ForkID:           opts.BaseRepo.ID,
		ObjectFormatName: opts.BaseRepo.ObjectFormatName,
	}

	oldRepoPath := opts.BaseRepo.RepoPath()

	needsRollback := false
	rollbackFn := func() {
		if !needsRollback {
			return
		}

		repoPath := repo_model.RepoPath(owner.Name, repo.Name)

		if exists, _ := util.IsExist(repoPath); !exists {
			return
		}

		// As the transaction will be failed and hence database changes will be destroyed we only need
		// to delete the related repository on the filesystem
		if errDelete := util.RemoveAll(repoPath); errDelete != nil {
			log.Error("Failed to remove fork repo")
		}
	}

	needsRollbackInPanic := true
	defer func() {
		panicErr := recover()
		if panicErr == nil {
			return
		}

		if needsRollbackInPanic {
			rollbackFn()
		}
		panic(panicErr)
	}()

	err = db.WithTx(ctx, func(txCtx context.Context) error {
		if err = repo_module.CreateRepositoryByExample(txCtx, doer, owner, repo, false, true); err != nil {
			return err
		}

		if err = repo_model.IncrementRepoForkNum(txCtx, opts.BaseRepo.ID); err != nil {
			return err
		}

		// copy lfs files failure should not be ignored
		if err = git_model.CopyLFS(txCtx, repo, opts.BaseRepo); err != nil {
			return err
		}

		needsRollback = true

		cloneCmd := git.NewCommand(txCtx, "clone", "--bare")
		if opts.SingleBranch != "" {
			cloneCmd.AddArguments("--single-branch", "--branch").AddDynamicArguments(opts.SingleBranch)
		}
		repoPath := repo_model.RepoPath(owner.Name, repo.Name)
		if stdout, _, err := cloneCmd.AddDynamicArguments(oldRepoPath, repoPath).
			SetDescription(fmt.Sprintf("ForkRepository(git clone): %s to %s", opts.BaseRepo.FullName(), repo.FullName())).
			RunStdBytes(&git.RunOpts{Timeout: 10 * time.Minute}); err != nil {
			log.Error("Fork Repository (git clone) Failed for %v (from %v):\nStdout: %s\nError: %v", repo, opts.BaseRepo, stdout, err)
			return fmt.Errorf("git clone: %w", err)
		}

		if err := repo_module.CheckDaemonExportOK(txCtx, repo); err != nil {
			return fmt.Errorf("checkDaemonExportOK: %w", err)
		}

		if stdout, _, err := git.NewCommand(txCtx, "update-server-info").
			SetDescription(fmt.Sprintf("ForkRepository(git update-server-info): %s", repo.FullName())).
			RunStdString(&git.RunOpts{Dir: repoPath}); err != nil {
			log.Error("Fork Repository (git update-server-info) failed for %v:\nStdout: %s\nError: %v", repo, stdout, err)
			return fmt.Errorf("git update-server-info: %w", err)
		}

		if err = repo_module.CreateDelegateHooks(repoPath); err != nil {
			return fmt.Errorf("createDelegateHooks: %w", err)
		}

		gitRepo, err := gitrepo.OpenRepository(txCtx, repo)
		if err != nil {
			return fmt.Errorf("OpenRepository: %w", err)
		}
		defer gitRepo.Close()

		_, err = repo_module.SyncRepoBranchesWithRepo(txCtx, repo, gitRepo, doer.ID)
		return err
	})
	needsRollbackInPanic = false
	if err != nil {
		rollbackFn()
		return nil, err
	}

	// even if below operations failed, it could be ignored. And they will be retried
	if err := repo_module.UpdateRepoSize(ctx, repo); err != nil {
		log.Error("Failed to update size for repository: %v", err)
	}
	if err := repo_model.CopyLanguageStat(ctx, opts.BaseRepo, repo); err != nil {
		log.Error("Copy language stat from oldRepo failed: %v", err)
	}

	gitRepo, err := gitrepo.OpenRepository(ctx, repo)
	if err != nil {
		log.Error("Open created git repository failed: %v", err)
	} else {
		defer gitRepo.Close()
		if err := repo_module.SyncReleasesWithTags(ctx, repo, gitRepo); err != nil {
			log.Error("Sync releases from git tags failed: %v", err)
		}
	}

	notify_service.ForkRepository(ctx, doer, opts.BaseRepo, repo)

	return repo, nil
}

// ConvertForkToNormalRepository convert the provided repo from a forked repo to normal repo
func ConvertForkToNormalRepository(ctx context.Context, repo *repo_model.Repository) error {
	err := db.WithTx(ctx, func(ctx context.Context) error {
		repo, err := repo_model.GetRepositoryByID(ctx, repo.ID)
		if err != nil {
			return err
		}

		if !repo.IsFork {
			return nil
		}

		if err := repo_model.DecrementRepoForkNum(ctx, repo.ForkID); err != nil {
			log.Error("Unable to decrement repo fork num for old root repo %d of repository %-v whilst converting from fork. Error: %v", repo.ForkID, repo, err)
			return err
		}

		repo.IsFork = false
		repo.ForkID = 0

		if err := repo_module.UpdateRepository(ctx, repo, false); err != nil {
			log.Error("Unable to update repository %-v whilst converting from fork. Error: %v", repo, err)
			return err
		}

		return nil
	})

	return err
}

type findForksOptions struct {
	db.ListOptions
	RepoID int64
	Doer   *user_model.User
}

func (opts findForksOptions) ToConds() builder.Cond {
	return builder.Eq{"fork_id": opts.RepoID}.And(
		repo_model.AccessibleRepositoryCondition(opts.Doer, unit.TypeInvalid),
	)
}

// FindForks returns all the forks of the repository
func FindForks(ctx context.Context, repo *repo_model.Repository, doer *user_model.User, listOptions db.ListOptions) ([]*repo_model.Repository, int64, error) {
	return db.FindAndCount[repo_model.Repository](ctx, findForksOptions{
		ListOptions: listOptions,
		RepoID:      repo.ID,
		Doer:        doer,
	})
}