bookhoard/internal/services/conversion_service.go

package services

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"time"

	"bookhoard/internal/database"

	"github.com/jackc/pgx/v5/pgtype"
)

// defaultConversionCacheTTL is the fallback kepub cache lifetime when no
// settings registry is wired. Matches the historical hardcoded 24h.
const defaultConversionCacheTTL = 24 * time.Hour

type ConvertedKEPUB struct {
	Path   string
	SHA256 string
	Cached bool
}

type ConversionService struct {
	db                 *database.Queries
	cacheDir           string
	conversionTool     string
	conversionCacheTTL time.Duration
	settings           *database.SettingsRegistry
}

func NewConversionService(db *database.Queries, cacheDir string) *ConversionService {
	return &ConversionService{
		db:                 db,
		cacheDir:           cacheDir,
		conversionTool:     "/usr/bin/kepubify",
		conversionCacheTTL: defaultConversionCacheTTL,
	}
}

// SetSettings wires the tunable settings registry. When wired, the cache TTL
// is read live on each conversion request.
func (s *ConversionService) SetSettings(reg *database.SettingsRegistry) { s.settings = reg }

// cacheTTL returns the active conversion cache TTL.
func (s *ConversionService) cacheTTL() time.Duration {
	if s.settings != nil {
		return s.settings.ConversionCacheTTL()
	}
	if s.conversionCacheTTL > 0 {
		return s.conversionCacheTTL
	}
	return defaultConversionCacheTTL
}

func (s *ConversionService) ConvertEPUBToKEPUB(ctx context.Context, mediaItemID pgtype.UUID, epubPath string) (*ConvertedKEPUB, error) {
	existing, err := s.db.GetMediaItemFormatByType(ctx, database.GetMediaItemFormatByTypeParams{
		MediaItemID: mediaItemID,
		FormatType:  "kepub",
	})
	if err == nil && existing.FilePath.Valid {
		if time.Since(existing.CreatedAt.Time) < s.cacheTTL() {
			return &ConvertedKEPUB{
				Path:   existing.FilePath.String,
				SHA256: existing.FileSha256.String,
				Cached: true,
			}, nil
		}
	}

	kepubPath := filepath.Join(s.cacheDir, fmt.Sprintf("%s.kepub.epub", mediaItemID.Bytes[:]))

	if err := os.MkdirAll(s.cacheDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create cache directory: %w", err)
	}

	if err := s.convertEPUB(epubPath, kepubPath); err != nil {
		return nil, fmt.Errorf("conversion failed: %w", err)
	}

	kepubSHA256, err := s.calculateSHA256(kepubPath)
	if err != nil {
		return nil, fmt.Errorf("hash calculation failed: %w", err)
	}

	epubFormat, err := s.db.GetMediaItemFormatByType(ctx, database.GetMediaItemFormatByTypeParams{
		MediaItemID: mediaItemID,
		FormatType:  "epub",
	})
	if err != nil {
		return nil, fmt.Errorf("EPUB format not found: %w", err)
	}

	fileinfo, err := os.Stat(kepubPath)
	if err != nil {
		return nil, fmt.Errorf("failed to stat converted file: %w", err)
	}

	var fileSize pgtype.Int8
	err = fileSize.Scan(fileinfo.Size())
	if err != nil {
		return nil, err
	}

	_, err = s.db.CreateMediaItemFormat(ctx, database.CreateMediaItemFormatParams{
		MediaItemID:           mediaItemID,
		FormatType:            "kepub",
		FilePath:              pgtype.Text{String: kepubPath, Valid: true},
		FileSha256:            pgtype.Text{String: kepubSHA256, Valid: true},
		FileSizeBytes:         fileSize,
		MimeType:              pgtype.Text{String: "application/vnd.kobo+xml+zip", Valid: true},
		ConvertedFromFormatID: pgtype.UUID{Bytes: epubFormat.ID.Bytes, Valid: true},
	})
	if err != nil {
		return nil, fmt.Errorf("failed to store converted format: %w", err)
	}

	return &ConvertedKEPUB{
		Path:   kepubPath,
		SHA256: kepubSHA256,
		Cached: false,
	}, nil
}

func (s *ConversionService) convertEPUB(epubPath, kepubPath string) error {
	if _, err := os.Stat(s.conversionTool); err == nil {
		cmd := exec.Command(s.conversionTool, "-i", epubPath, "-o", kepubPath)
		if output, err := cmd.CombinedOutput(); err != nil {
			return fmt.Errorf("kepubify failed: %w, output: %s", err, string(output))
		}
		return nil
	}

	cmd := exec.Command("ebook-convert", epubPath, kepubPath, "--output-format", "kepub")
	if output, err := cmd.CombinedOutput(); err != nil {
		return fmt.Errorf("ebook-convert failed: %w, output: %s", err, string(output))
	}
	return nil
}

func (s *ConversionService) calculateSHA256(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", err
	}
	defer file.Close()

	hasher := sha256.New()
	if _, err := io.Copy(hasher, file); err != nil {
		return "", err
	}

	return hex.EncodeToString(hasher.Sum(nil)), nil
}