Extract metadata from pdf file

extract.go

package pdflib

import (
	"fmt"
	"time"

	"github.com/timemore/foundation/errors"
	pdf "github.com/unidoc/unipdf/v3/model"
)

func Export() {
	fmt.Println("hello")
}

type PDFDocMetaDataInfo struct {
	Title        string
	NumPages     int64
	Author       string
	Subject      string
	Keywords     string
	Creator      string
	Producer     string
	CreationDate *time.Time
	ModifiedDate *time.Time
	Trapped      string
	CustomInfo   map[string]string
}

func MetaData(r *pdf.PdfReader) (*PDFDocMetaDataInfo, error) {
	numPages, err := r.GetNumPages()
	if err != nil {
		return nil, errors.Wrap("get document pages", err)
	}

	documentMetaData := PDFDocMetaDataInfo{
		NumPages: int64(numPages),
	}
	if pdfInfo, err := r.GetPdfInfo(); err == nil {
		if pdfInfo.Title != nil {
			documentMetaData.Title = pdfInfo.Title.Decoded()
		}

		if pdfInfo.Author != nil {
			documentMetaData.Author = pdfInfo.Author.Decoded()
		}

		if pdfInfo.Subject != nil {
			documentMetaData.Subject = pdfInfo.Subject.Decoded()
		}

		if pdfInfo.Keywords != nil {
			documentMetaData.Keywords = pdfInfo.Keywords.Decoded()
		}

		if pdfInfo.Creator != nil {
			documentMetaData.Creator = pdfInfo.Creator.Decoded()
		}

		if pdfInfo.Producer != nil {
			documentMetaData.Producer = pdfInfo.Producer.Decoded()
		}
		if pdfInfo.CreationDate != nil {
			creationDate := pdfInfo.CreationDate.ToGoTime()
			documentMetaData.CreationDate = &creationDate
		}

		if pdfInfo.ModifiedDate != nil {
			modifiedDate := pdfInfo.ModifiedDate.ToGoTime()
			documentMetaData.ModifiedDate = &modifiedDate
		}

		if pdfInfo.Trapped != nil {
			documentMetaData.Trapped = pdfInfo.Trapped.String()
		}

		customInfoKeys := pdfInfo.CustomKeys()
		documentMetaData.CustomInfo = make(map[string]string, len(customInfoKeys))

		for _, key := range customInfoKeys {
			documentMetaData.CustomInfo[key] = pdfInfo.GetCustomInfo(key).Decoded()
		}
	}

	return &documentMetaData, nil
}