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

package repository

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	git_model "code.gitea.io/gitea/models/git"
	repo_model "code.gitea.io/gitea/models/repo"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/git/gitcmd"
	"code.gitea.io/gitea/modules/gitrepo"
	"code.gitea.io/gitea/modules/glob"
	"code.gitea.io/gitea/modules/log"
	repo_module "code.gitea.io/gitea/modules/repository"
	"code.gitea.io/gitea/modules/setting"
	"code.gitea.io/gitea/modules/util"

	"github.com/huandu/xstrings"
)

type transformer struct {
	Name      string
	Transform func(string) string
}

type expansion struct {
	Name         string
	Value        string
	Transformers []transformer
}

var defaultTransformers = []transformer{
	{Name: "SNAKE", Transform: xstrings.ToSnakeCase},
	{Name: "KEBAB", Transform: xstrings.ToKebabCase},
	{Name: "CAMEL", Transform: xstrings.ToCamelCase},
	{Name: "PASCAL", Transform: xstrings.ToPascalCase},
	{Name: "LOWER", Transform: strings.ToLower},
	{Name: "UPPER", Transform: strings.ToUpper},
	{Name: "TITLE", Transform: util.ToTitleCase},
}

func generateExpansion(ctx context.Context, src string, templateRepo, generateRepo *repo_model.Repository, sanitizeFileName bool) string {
	year, month, day := time.Now().Date()
	expansions := []expansion{
		{Name: "YEAR", Value: strconv.Itoa(year), Transformers: nil},
		{Name: "MONTH", Value: fmt.Sprintf("%02d", int(month)), Transformers: nil},
		{Name: "MONTH_ENGLISH", Value: month.String(), Transformers: defaultTransformers},
		{Name: "DAY", Value: fmt.Sprintf("%02d", day), Transformers: nil},
		{Name: "REPO_NAME", Value: generateRepo.Name, Transformers: defaultTransformers},
		{Name: "TEMPLATE_NAME", Value: templateRepo.Name, Transformers: defaultTransformers},
		{Name: "REPO_DESCRIPTION", Value: generateRepo.Description, Transformers: nil},
		{Name: "TEMPLATE_DESCRIPTION", Value: templateRepo.Description, Transformers: nil},
		{Name: "REPO_OWNER", Value: generateRepo.OwnerName, Transformers: defaultTransformers},
		{Name: "TEMPLATE_OWNER", Value: templateRepo.OwnerName, Transformers: defaultTransformers},
		{Name: "REPO_LINK", Value: generateRepo.Link(), Transformers: nil},
		{Name: "TEMPLATE_LINK", Value: templateRepo.Link(), Transformers: nil},
		{Name: "REPO_HTTPS_URL", Value: generateRepo.CloneLinkGeneral(ctx).HTTPS, Transformers: nil},
		{Name: "TEMPLATE_HTTPS_URL", Value: templateRepo.CloneLinkGeneral(ctx).HTTPS, Transformers: nil},
		{Name: "REPO_SSH_URL", Value: generateRepo.CloneLinkGeneral(ctx).SSH, Transformers: nil},
		{Name: "TEMPLATE_SSH_URL", Value: templateRepo.CloneLinkGeneral(ctx).SSH, Transformers: nil},
	}

	expansionMap := make(map[string]string)
	for _, e := range expansions {
		expansionMap[e.Name] = e.Value
		for _, tr := range e.Transformers {
			expansionMap[fmt.Sprintf("%s_%s", e.Name, tr.Name)] = tr.Transform(e.Value)
		}
	}

	return os.Expand(src, func(key string) string {
		if expansion, ok := expansionMap[key]; ok {
			if sanitizeFileName {
				return fileNameSanitize(expansion)
			}
			return expansion
		}
		return key
	})
}

// GiteaTemplate holds information about a .gitea/template file
type GiteaTemplate struct {
	Path    string
	Content []byte

	globs []glob.Glob
}

// Globs parses the .gitea/template globs or returns them if they were already parsed
func (gt *GiteaTemplate) Globs() []glob.Glob {
	if gt.globs != nil {
		return gt.globs
	}

	gt.globs = make([]glob.Glob, 0)
	scanner := bufio.NewScanner(bytes.NewReader(gt.Content))
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		g, err := glob.Compile(line, '/')
		if err != nil {
			log.Info("Invalid glob expression '%s' (skipped): %v", line, err)
			continue
		}
		gt.globs = append(gt.globs, g)
	}
	return gt.globs
}

func readGiteaTemplateFile(tmpDir string) (*GiteaTemplate, error) {
	gtPath := filepath.Join(tmpDir, ".gitea", "template")
	if _, err := os.Stat(gtPath); os.IsNotExist(err) {
		return nil, nil
	} else if err != nil {
		return nil, err
	}

	content, err := os.ReadFile(gtPath)
	if err != nil {
		return nil, err
	}

	return &GiteaTemplate{Path: gtPath, Content: content}, nil
}

func processGiteaTemplateFile(ctx context.Context, tmpDir string, templateRepo, generateRepo *repo_model.Repository, giteaTemplateFile *GiteaTemplate) error {
	if err := util.Remove(giteaTemplateFile.Path); err != nil {
		return fmt.Errorf("remove .giteatemplate: %w", err)
	}
	if len(giteaTemplateFile.Globs()) == 0 {
		return nil // Avoid walking tree if there are no globs
	}
	tmpDirSlash := strings.TrimSuffix(filepath.ToSlash(tmpDir), "/") + "/"
	return filepath.WalkDir(tmpDirSlash, func(path string, d os.DirEntry, walkErr error) error {
		if walkErr != nil {
			return walkErr
		}

		if d.IsDir() {
			return nil
		}

		base := strings.TrimPrefix(filepath.ToSlash(path), tmpDirSlash)
		for _, g := range giteaTemplateFile.Globs() {
			if g.Match(base) {
				content, err := os.ReadFile(path)
				if err != nil {
					return err
				}

				generatedContent := []byte(generateExpansion(ctx, string(content), templateRepo, generateRepo, false))
				if err := os.WriteFile(path, generatedContent, 0o644); err != nil {
					return err
				}

				substPath := filepath.FromSlash(filepath.Join(tmpDirSlash, generateExpansion(ctx, base, templateRepo, generateRepo, true)))

				// Create parent subdirectories if needed or continue silently if it exists
				if err = os.MkdirAll(filepath.Dir(substPath), 0o755); err != nil {
					return err
				}

				// Substitute filename variables
				if err = os.Rename(path, substPath); err != nil {
					return err
				}
				break
			}
		}
		return nil
	}) // end: WalkDir
}

func generateRepoCommit(ctx context.Context, repo, templateRepo, generateRepo *repo_model.Repository, tmpDir string) error {
	commitTimeStr := time.Now().Format(time.RFC3339)
	authorSig := repo.Owner.NewGitSig()

	// Because this may call hooks we should pass in the environment
	env := append(os.Environ(),
		"GIT_AUTHOR_NAME="+authorSig.Name,
		"GIT_AUTHOR_EMAIL="+authorSig.Email,
		"GIT_AUTHOR_DATE="+commitTimeStr,
		"GIT_COMMITTER_NAME="+authorSig.Name,
		"GIT_COMMITTER_EMAIL="+authorSig.Email,
		"GIT_COMMITTER_DATE="+commitTimeStr,
	)

	// Clone to temporary path and do the init commit.
	templateRepoPath := templateRepo.RepoPath()
	if err := git.Clone(ctx, templateRepoPath, tmpDir, git.CloneRepoOptions{
		Depth:  1,
		Branch: templateRepo.DefaultBranch,
	}); err != nil {
		return fmt.Errorf("git clone: %w", err)
	}

	// Get active submodules from the template
	submodules, err := git.GetTemplateSubmoduleCommits(ctx, tmpDir)
	if err != nil {
		return fmt.Errorf("GetTemplateSubmoduleCommits: %w", err)
	}

	if err = util.RemoveAll(filepath.Join(tmpDir, ".git")); err != nil {
		return fmt.Errorf("remove git dir: %w", err)
	}

	// Variable expansion
	giteaTemplateFile, err := readGiteaTemplateFile(tmpDir)
	if err != nil {
		return fmt.Errorf("readGiteaTemplateFile: %w", err)
	}

	if giteaTemplateFile != nil {
		err = processGiteaTemplateFile(ctx, tmpDir, templateRepo, generateRepo, giteaTemplateFile)
		if err != nil {
			return err
		}
	}

	if err = git.InitRepository(ctx, tmpDir, false, templateRepo.ObjectFormatName); err != nil {
		return err
	}

	if stdout, _, err := gitcmd.NewCommand("remote", "add", "origin").
		AddDynamicArguments(repo.RepoPath()).
		WithDir(tmpDir).
		WithEnv(env).
		RunStdString(ctx); err != nil {
		log.Error("Unable to add %v as remote origin to temporary repo to %s: stdout %s\nError: %v", repo, tmpDir, stdout, err)
		return fmt.Errorf("git remote add: %w", err)
	}

	if err = git.AddTemplateSubmoduleIndexes(ctx, tmpDir, submodules); err != nil {
		return fmt.Errorf("failed to add submodules: %v", err)
	}

	// set default branch based on whether it's specified in the newly generated repo or not
	defaultBranch := repo.DefaultBranch
	if strings.TrimSpace(defaultBranch) == "" {
		defaultBranch = templateRepo.DefaultBranch
	}

	return initRepoCommit(ctx, tmpDir, repo, repo.Owner, defaultBranch)
}

// GenerateGitContent generates git content from a template repository
func GenerateGitContent(ctx context.Context, templateRepo, generateRepo *repo_model.Repository) (err error) {
	tmpDir, cleanup, err := setting.AppDataTempDir("git-repo-content").MkdirTempRandom("gitea-" + generateRepo.Name)
	if err != nil {
		return fmt.Errorf("failed to create temp dir for repository %s: %w", generateRepo.FullName(), err)
	}
	defer cleanup()

	if err = generateRepoCommit(ctx, generateRepo, templateRepo, generateRepo, tmpDir); err != nil {
		return fmt.Errorf("generateRepoCommit: %w", err)
	}

	// re-fetch repo
	if generateRepo, err = repo_model.GetRepositoryByID(ctx, generateRepo.ID); err != nil {
		return fmt.Errorf("getRepositoryByID: %w", err)
	}

	// if there was no default branch supplied when generating the repo, use the default one from the template
	if strings.TrimSpace(generateRepo.DefaultBranch) == "" {
		generateRepo.DefaultBranch = templateRepo.DefaultBranch
	}

	if err = gitrepo.SetDefaultBranch(ctx, generateRepo, generateRepo.DefaultBranch); err != nil {
		return fmt.Errorf("setDefaultBranch: %w", err)
	}
	if err = repo_model.UpdateRepositoryColsNoAutoTime(ctx, generateRepo, "default_branch"); err != nil {
		return fmt.Errorf("updateRepository: %w", err)
	}

	if err := repo_module.UpdateRepoSize(ctx, generateRepo); err != nil {
		return fmt.Errorf("failed to update size for repository: %w", err)
	}

	if err := git_model.CopyLFS(ctx, generateRepo, templateRepo); err != nil {
		return fmt.Errorf("failed to copy LFS: %w", err)
	}
	return nil
}

// GenerateRepoOptions contains the template units to generate
type GenerateRepoOptions struct {
	Name            string
	DefaultBranch   string
	Description     string
	Private         bool
	GitContent      bool
	Topics          bool
	GitHooks        bool
	Webhooks        bool
	Avatar          bool
	IssueLabels     bool
	ProtectedBranch bool
}

// IsValid checks whether at least one option is chosen for generation
func (gro GenerateRepoOptions) IsValid() bool {
	return gro.GitContent || gro.Topics || gro.GitHooks || gro.Webhooks || gro.Avatar ||
		gro.IssueLabels || gro.ProtectedBranch // or other items as they are added
}

var fileNameSanitizeRegexp = regexp.MustCompile(`(?i)\.\.|[<>:\"/\\|?*\x{0000}-\x{001F}]|^(con|prn|aux|nul|com\d|lpt\d)$`)

// Sanitize user input to valid OS filenames
//
//		Based on https://github.com/sindresorhus/filename-reserved-regex
//	 Adds ".." to prevent directory traversal
func fileNameSanitize(s string) string {
	return strings.TrimSpace(fileNameSanitizeRegexp.ReplaceAllString(s, "_"))
}
