package spool

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"github.com/rvbox/rvbox/internal/domain"
)

func loadOrCreateIdentity(path string, generate func() (domain.UUID, error)) (domain.UUID, error) {
	data, err := os.ReadFile(path)
	if err == nil {
		return parseIdentity(data)
	}
	if !errors.Is(err, os.ErrNotExist) {
		return domain.UUID{}, fmt.Errorf("read client instance identity: %w", err)
	}
	identity, err := generate()
	if err != nil {
		return domain.UUID{}, fmt.Errorf("generate client instance identity: %w", err)
	}
	if err := writeIdentityAtomically(path, []byte(identity.String()+"\n")); err != nil {
		return domain.UUID{}, err
	}
	return identity, nil
}

func parseIdentity(data []byte) (domain.UUID, error) {
	if len(data) != 37 || data[36] != '\n' {
		return domain.UUID{}, ErrIdentityCorrupt
	}
	identity, err := domain.ParseUUIDv7(string(data[:36]))
	if err != nil {
		return domain.UUID{}, fmt.Errorf("%w: %v", ErrIdentityCorrupt, err)
	}
	return identity, nil
}

func writeIdentityAtomically(path string, data []byte) (result error) {
	directory := filepath.Dir(path)
	temporary, err := os.CreateTemp(directory, ".client-instance-id-*")
	if err != nil {
		return fmt.Errorf("create client identity temporary file: %w", err)
	}
	temporaryPath := temporary.Name()
	defer func() {
		if result != nil {
			_ = os.Remove(temporaryPath)
		}
	}()
	if err := securePrivateFile(temporaryPath); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("secure client identity temporary file: %w", err)
	}
	if _, err := temporary.Write(data); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("write client identity: %w", err)
	}
	if err := temporary.Sync(); err != nil {
		_ = temporary.Close()
		return fmt.Errorf("sync client identity: %w", err)
	}
	if err := temporary.Close(); err != nil {
		return fmt.Errorf("close client identity: %w", err)
	}
	if err := replaceIdentityFile(temporaryPath, path); err != nil {
		return fmt.Errorf("install client identity: %w", err)
	}
	if err := syncDirectory(directory); err != nil {
		return fmt.Errorf("sync client identity directory: %w", err)
	}
	return nil
}