package samba

import (
	"bytes"
	"context"
	"embed"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"text/template"
	"time"

	"github.com/darroyo/nasctl/internal/db"
	"github.com/darroyo/nasctl/internal/system"
)

const ModuleName = "samba"

//go:embed smb.conf.tmpl
var smbConfTemplate embed.FS

type Config struct {
	SMBConfPath string
	Reload      bool
}

type Module struct {
	cfg Config
}

type templateShare struct {
	Name         string
	Path         string
	Comment      string
	ReadOnly     bool
	GuestOK      bool
	ValidUsers   []string
	ValidGroups  []string
	InvalidUsers []string
}

type templateData struct {
	Shares []templateShare
}

func New(cfg Config) *Module {
	if cfg.SMBConfPath == "" {
		cfg.SMBConfPath = "/etc/samba/smb.conf"
	}
	return &Module{cfg: cfg}
}

func (m *Module) Name() string {
	return ModuleName
}

func (m *Module) IsDirty(ctx context.Context, database *db.DB) (bool, error) {
	return database.IsDirty(ModuleName)
}

func (m *Module) Apply(ctx context.Context, database *db.DB) error {
	if err := m.maybeBackup(database); err != nil {
		return err
	}

	shares, err := database.ListSambaShares()
	if err != nil {
		return err
	}

	content, err := m.renderConfig(shares)
	if err != nil {
		return err
	}

	if err := writeAtomic(m.cfg.SMBConfPath, content); err != nil {
		return err
	}

	if m.cfg.Reload {
		stdout, stderr, err := system.Run(ctx, "systemctl", "reload", "smbd")
		if err != nil {
			return fmt.Errorf("reload smbd: %w (stdout=%q stderr=%q)", err, stdout, stderr)
		}
	}

	message := fmt.Sprintf("applied %d samba share(s) to %s", len(shares), m.cfg.SMBConfPath)
	if err := database.AppendApplyLog(ModuleName, message, true); err != nil {
		return err
	}
	return database.ClearDirty(ModuleName)
}

func (m *Module) renderConfig(shares []db.SambaShare) ([]byte, error) {
	tmplContent, err := smbConfTemplate.ReadFile("smb.conf.tmpl")
	if err != nil {
		return nil, fmt.Errorf("read smb.conf template: %w", err)
	}

	funcMap := template.FuncMap{
		"join": strings.Join,
	}

	tmpl, err := template.New("smb.conf").Funcs(funcMap).Parse(string(tmplContent))
	if err != nil {
		return nil, fmt.Errorf("parse smb.conf template: %w", err)
	}

	data := templateData{Shares: make([]templateShare, 0, len(shares))}
	for _, share := range shares {
		data.Shares = append(data.Shares, templateShare{
			Name:         share.Name,
			Path:         share.Path,
			Comment:      share.Comment,
			ReadOnly:     share.ReadOnly,
			GuestOK:      share.GuestOK,
			ValidUsers:   share.ValidUsers,
			ValidGroups:  share.ValidGroups,
			InvalidUsers: share.InvalidUsers,
		})
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, data); err != nil {
		return nil, fmt.Errorf("execute smb.conf template: %w", err)
	}
	return buf.Bytes(), nil
}

func (m *Module) maybeBackup(database *db.DB) error {
	done, ok, err := database.GetSetting("backup.samba.done")
	if err != nil {
		return err
	}
	if ok && done == "true" {
		return nil
	}
	if _, err := os.Stat(m.cfg.SMBConfPath); os.IsNotExist(err) {
		return nil
	} else if err != nil {
		return nil
	}
	src, err := os.ReadFile(m.cfg.SMBConfPath)
	if err != nil {
		return nil
	}
	backupPath := m.cfg.SMBConfPath + ".nasctl.bak." + time.Now().Format("20060102T150405")
	if err := os.WriteFile(backupPath, src, 0o644); err != nil {
		return fmt.Errorf("backup smb.conf: %w", err)
	}
	_ = database.SetSetting("backup.samba.done", "true")
	return nil
}

func writeAtomic(path string, content []byte) error {
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return fmt.Errorf("create config dir: %w", err)
	}

	tmp, err := os.CreateTemp(dir, ".smb.conf.*")
	if err != nil {
		return fmt.Errorf("create temp file: %w", err)
	}
	tmpPath := tmp.Name()

	cleanup := func() {
		_ = tmp.Close()
		_ = os.Remove(tmpPath)
	}

	if _, err := tmp.Write(content); err != nil {
		cleanup()
		return fmt.Errorf("write temp config: %w", err)
	}
	if err := tmp.Chmod(0o644); err != nil {
		cleanup()
		return fmt.Errorf("chmod temp config: %w", err)
	}
	if err := tmp.Close(); err != nil {
		cleanup()
		return fmt.Errorf("close temp config: %w", err)
	}
	if err := os.Rename(tmpPath, path); err != nil {
		cleanup()
		return fmt.Errorf("rename temp config: %w", err)
	}
	return nil
}