qiyuesuo-client/preview.go

package qiyuesuosdk

import (
	"bytes"
	"fmt"
)

// SealPreviewKeyword 预览 PDF 内用于关键字定位公章的占位文本。
const SealPreviewKeyword = "__SEAL_PREVIEW__"

func buildSealPreviewPDF() []byte {
	text := fmt.Sprintf("BT /F1 20 Tf 72 400 Td (%s) Tj ET", SealPreviewKeyword)
	streamObj := fmt.Sprintf("4 0 obj\n<< /Length %d >>\nstream\n%s\nendstream\n", len(text), text)
	objects := []string{
		"1 0 obj\n<< /Type /Catalog /Pages 2 0 R >>\nendobj\n",
		"2 0 obj\n<< /Type /Pages /Kids [3 0 R] /Count 1 >>\nendobj\n",
		"3 0 obj\n<< /Type /Page /Parent 2 0 R /MediaBox [0 0 595 842] /Contents 4 0 R /Resources << /Font << /F1 5 0 R >> >> >>\nendobj\n",
		streamObj,
		"5 0 obj\n<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica >>\nendobj\n",
	}

	var buf bytes.Buffer
	buf.WriteString("%PDF-1.4\n")
	offsets := make([]int, len(objects)+1)
	for i, obj := range objects {
		offsets[i+1] = buf.Len()
		buf.WriteString(obj)
	}
	xrefPos := buf.Len()
	buf.WriteString(fmt.Sprintf("xref\n0 %d\n0000000000 65535 f \n", len(objects)+1))
	for i := 1; i <= len(objects); i++ {
		buf.WriteString(fmt.Sprintf("%010d 00000 n \n", offsets[i]))
	}
	buf.WriteString(fmt.Sprintf("trailer\n<< /Size %d /Root 1 0 R >>\nstartxref\n%d\n%%EOF\n", len(objects)+1, xrefPos))
	return buf.Bytes()
}

// PreviewCompanySealPDF 生成空白 PDF 并静默盖机构公章，用于预览（不依赖印章图片查看权限）。
func (c *Client) PreviewCompanySealPDF(company CompanyLocateParams, companyDisplayName string) ([]byte, error) {
	processID := c.resolveProcessID("")
	launcher := c.resolveLauncher("")
	if processID == "" || launcher == "" {
		return nil, ErrInvalidParams
	}
	displayName := companyDisplayName
	if displayName == "" {
		displayName = company.Name
	}
	if displayName == "" {
		return nil, ErrInvalidParams
	}

	pdf := buildSealPreviewPDF()
	subject := "机构公章预览"
	docID, err := c.uploadDocument(subject, pdf)
	if err != nil {
		return nil, err
	}
	contractID, err := c.createContract(processID, subject, launcher, docID, displayName, nil)
	if err != nil {
		return nil, err
	}
	spec := CompanySealSpec{
		CompanyName: displayName,
		Keyword:     SealPreviewKeyword,
		OffsetX:     "0",
		OffsetY:     "0",
		Page:        "1",
	}
	if err = c.companySilentSignFor(contractID, company, spec); err != nil {
		return nil, err
	}
	return c.downloadDocument(docID)
}