// Package admin manage repos
package admin

import (
	"errors"
	"fmt"
	"io"
	"io/fs"
	"log"
	"log/slog"
	"os"
	"path/filepath"

	"github.com/go-git/go-billy/v5/memfs"
	"github.com/go-git/go-billy/v5/osfs"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/storage/filesystem"
	"github.com/go-git/go-git/v5/storage/memory"
	"gopkg.in/ini.v1"
	"sigs.k8s.io/yaml"
)

const (
	// Read mode operations for repo
	Read Action = 0
	// Write mode operations for repo
	Write = 1
	// Admin mode operations for repo
	Admin = 2
	// GitExportMagic magic file name for daemon export
	GitExportMagic = "git-daemon-export-ok"
	// GitWebExportMagic magic filename for web repos
	GitWebExportMagic = "git-web-export-ok"
	mgmtRepoName      = "mgmt.git"
)

var (
	ErrMgmtRepoNotFound = errors.New("mgmt repo does not exist")

	defaultRepo = &GitRepo{
		Name:   "mgmt",
		Public: false,
		Permissions: []*Permission{
			{
				Role: "admin",
				Mode: 1,
			},
		},
	}
	defaultServerConfig = &ServerRepos{
		Name:    "default config",
		Version: "v1alpha1",
		Repos: []*GitRepo{
			defaultRepo,
		},
	}
)

// Action composite type for modes
type Action int

// GitWeb git web configuration
type GitWeb struct {
	Owner       string `json:"owner"`
	Description string `json:"description"`
	Category    string `json:"category"`
	URL         string `json:"url"`
}

// Permission authorization controls
type Permission struct {
	Role string `json:"role"`
	Mode Action `json:"mode"`
}

// GitRepo git repository
type GitRepo struct {
	// Public "git-daemon-export-ok" magic file for git-http-backend
	Public bool `json:"public"`
	// Name game of repository
	Name string `json:"name"`
	// Web config settings
	GitWebConfig *GitWeb `json:"git_web_config"`
	// Permissions for authorization
	Permissions []*Permission `json:"permissions"`
}

// ServerRepos repos that are part of this server instance
type ServerRepos struct {
	// Name of the configuration
	Name string `json:"name"`
	// Version of the config file
	Version string `json:"version"`
	// Repos a list of repos that are managed
	Repos []*GitRepo `json:"repos"`
	// this is set by the cli on start
	basePath string
}

func loadConfigFromGit(baseDir, filePath string) ([]byte, error) {
	mgmtPath := filepath.Join(baseDir, mgmtRepoName)
	slog.Info("loading server config", "configPath", mgmtPath)
	_, err := os.Stat(mgmtPath)
	if errors.Is(err, os.ErrNotExist) {
		return []byte(""), ErrMgmtRepoNotFound
	} else if err != nil {
		log.Fatalf("An unexpected error was encountered %s", err)
	}
	repoURI := fmt.Sprintf("file://%s", mgmtPath)
	slog.Info("mgmt repo uri", "uri", repoURI)
	fs := memfs.New()
	storer := memory.NewStorage()
	_, err = git.Clone(storer, fs, &git.CloneOptions{
		URL: repoURI,
	})
	if err != nil {
		return []byte(""), fmt.Errorf("couldn't clone mgmt repo %s %w", repoURI, err)
	}
	file, err := fs.Open(filePath)
	if err != nil {
		return []byte(""), fmt.Errorf("couldn't open file in repo %w", err)
	}

	defer file.Close()
	return io.ReadAll(file)
}

func loadLocalFile(path string) ([]byte, error) {
	file, err := os.Open(path)
	if err != nil {
		return []byte{}, fmt.Errorf("config file not opened or found %w", err)
	}
	defer file.Close()
	configBytes, err := io.ReadAll(file)
	if err != nil {
		return []byte{}, fmt.Errorf("config file not read %w", err)
	}
	return configBytes, nil
}

// setupPolicyFile
func setupPolicyFile(src string) (string, error) {
	workingPolicyFile, err := os.CreateTemp("", "go-git-server-policy")
	if err != nil {
		return "", fmt.Errorf("coudn't read base policy %w", err)
	}
	defer workingPolicyFile.Close()
	basePolicy, err := os.ReadFile(src)
	if err != nil {
		return "", fmt.Errorf("coudn't read base policy %w", err)
	}
	written, err := workingPolicyFile.Write(basePolicy)
	if err != nil {
		return "", fmt.Errorf("encountered error writting policy %w", err)
	}
	if written == 0 {
		return "", fmt.Errorf("nothing was written")
	}
	return workingPolicyFile.Name(), nil
}

// loadServerConfig configPath should be the absolutepath to the configmap if it's not in a repo
func loadServerConfig(mgmtRepo bool, baseDir, configPath string) (*ServerRepos, error) {
	var (
		configBytes []byte
		err         error
	)
	if mgmtRepo {
		configBytes, err = loadConfigFromGit(baseDir, configPath)
		if err != nil {
			return &ServerRepos{}, err
		}
	} else {
		configBytes, err = loadLocalFile(configPath)
		if err != nil {
			slog.Error("Local server config couldn't be loaded")
			return &ServerRepos{}, err
		}
	}
	config := &ServerRepos{}
	err = yaml.Unmarshal(configBytes, &config)
	if err != nil {
		return &ServerRepos{}, errors.New("could not parse gitserver config")
	}
	return config, nil
}

// ServerPolicies generate casbin policies
func (s *ServerRepos) ServerPolicies() [][]string {
	policies := [][]string{}
	for _, repo := range s.Repos {
		policies = append(policies, repo.CasbinPolicies()...)
	}
	return policies
}

// ConfigureRepos run reconciler for all repos
func (s *ServerRepos) ConfigureRepos() error {
	slog.Info("configuring repos", "toBeConfigured", len(s.Repos))
	var errs []error
	for _, repo := range s.Repos {
		if err := repo.ReconcileRepo(s.basePath); err != nil {
			slog.Error("error reconcile", "repo", repo.Name, "err", err)
			errs = append(errs, err)
		}
	}
	return errors.Join(errs...)
}

func readOnlyPaths(role, repoName string) [][]string {
	// WARN this is kind of hard coded pathing... not sure that's great
	return [][]string{
		{role, fmt.Sprintf("/%s/info/refs", repoName), "GET"},
		{role, fmt.Sprintf("/%s/git-upload-pack", repoName), "POST"},
	}
}
func writePaths(role, repoName string) [][]string {
	// WARN this is kind of hard coded pathing... not sure that's great
	return [][]string{{role, fmt.Sprintf("/%s/git-receive-pack", repoName), "POST"}}
}

// Policy generate policy for repo base on mode
func (p *Permission) Policy(repoName string) [][]string {
	policies := [][]string{}
	// if read mode or greater e.g. write mode
	roleName := fmt.Sprintf("role:%s", p.Role)
	if p.Mode >= Read {
		policies = append(policies, readOnlyPaths(roleName, repoName)...)
	}
	// if write mode
	if p.Mode >= Write {
		policies = append(policies, writePaths(roleName, repoName)...)
	}
	return policies
}

// CasbinPolicies generate all policies
func (r *GitRepo) CasbinPolicies() [][]string {
	policies := [][]string{}
	for _, perm := range r.Permissions {
		policies = append(policies, perm.Policy(r.Name)...)
	}
	return policies
}

// ReconcileRepo update repo export settings, update web config
func (r *GitRepo) ReconcileRepo(basePath string) error {
	// if exist -> continue
	repoBase := filepath.Join(basePath, fmt.Sprintf("%s.git", r.Name))
	slog.Info("reconciling repo", "repoPath", repoBase)
	_, err := os.Stat(repoBase)
	if errors.Is(err, fs.ErrNotExist) {
		// if no exist -> init bare
		repoFs := osfs.New(repoBase)
		strg := filesystem.NewStorage(repoFs, nil)
		_, _ = git.Init(strg, nil)
	}
	// set export file for git-http-backend
	okExport := filepath.Join(repoBase, GitExportMagic)
	_, err = os.Stat(okExport)
	if errors.Is(err, fs.ErrNotExist) {
		// Create web export
		f, err := os.Create(okExport)
		f.Close()
		if err != nil {
			return fmt.Errorf("%s couldn't be created %w", GitExportMagic, err)
		}
	}
	r.ConfigureExport(repoBase)
	if r.GitWebConfig == nil {
		r.GitWebConfig = &GitWeb{}
	}
	r.GitWebConfig.ReconcileGitConf(repoBase)
	return nil
}

// ConfigureExport setup repo for sharing and configure web settings
func (r *GitRepo) ConfigureExport(repoBase string) {
	if !r.Public {
		return
	}
	okExport := filepath.Join(repoBase, GitWebExportMagic)
	_, err := os.Create(okExport)
	if err != nil {
		log.Fatalf("%s couldn't be created %s", GitWebExportMagic, err)
	}
}

// ReconcileGitConf reconcile gitweb configuration section of gitconfig
func (r *GitWeb) ReconcileGitConf(repoBase string) {
	confPath := filepath.Join(repoBase, "config")
	cfg, err := ini.Load(confPath)
	if err != nil {
		log.Fatalf("couldn't read gitconfig %s", err)
	}
	// check if empty, delete
	if (GitWeb{} == *r) {
		if cfg.HasSection("gitweb") {
			cfg.DeleteSection("gitweb")
			if err := cfg.SaveTo(confPath); err != nil {
				log.Fatalf("couldn't save gitconfig %s", err)
			}
		}
		return
	}
	section := cfg.Section("gitweb")
	section.Key("description").SetValue(r.Description)
	section.Key("owner").SetValue(r.Owner)
	section.Key("url").SetValue(r.URL)
	section.Key("category").SetValue(r.Category)
	if err := cfg.SaveTo(confPath); err != nil {
		log.Fatalf("couldn't save gitconfig %s", err)
	}
}