Move PDF handling code to a separate file

2 files changed, 102 insertions, 73 deletions

diff --git a/cmd/pdfbook/main.go b/cmd/pdfbook/main.go
index 45bbc4f..3146865 100644
--- a/cmd/pdfbook/main.go
+++ b/cmd/pdfbook/main.go
@@ -1,24 +1,23 @@
 package main
 
 import (
-	"errors"
 	"flag"
 	"fmt"
-	"html"
-	"image"
-	_ "image/jpeg"
-	_ "image/png"
-	"io/ioutil"
 	"log"
 	"os"
 	"path"
 	"path/filepath"
 	"strings"
 
-	"rescribe.xyz/gofpdf"
-	"rescribe.xyz/utils/pkg/hocr"
+	"rescribe.xyz/bookpipeline"
 )
 
+type Pdfer interface {
+	Setup() error
+	AddPage(imgpath, hocrpath string) error
+	Save(path string) error
+}
+
 const pageWidth = 5 // pageWidth in inches
 
 // pxToPt converts a pixel value into a pt value (72 pts per inch)
@@ -27,68 +26,7 @@ func pxToPt(i int) float64 {
 	return float64(i) / pageWidth
 }
 
-// setupPdf creates a new PDF with appropriate settings and fonts
-// TODO: this will go in pdf.go in due course
-// TODO: find a font that's closer to the average dimensions of the
-//       text we're dealing with, and put it somewhere sensible
-func setupPdf() *gofpdf.Fpdf {
-	pdf := gofpdf.New("P", "pt", "A4", "")
-	// Even though it's invisible, we need to add a font which can do
-	// UTF-8 so that text renders correctly.
-	pdf.AddUTF8Font("dejavu", "", "DejaVuSansCondensed.ttf")
-	pdf.SetFont("dejavu", "", 10)
-	pdf.SetAutoPageBreak(false, float64(0))
-	return pdf
-}
-
-// addPage adds a page to the pdf with an image and (invisible)
-// text from an hocr file
-func addPage(pdf *gofpdf.Fpdf, imgpath string, hocrpath string) error {
-	file, err := ioutil.ReadFile(hocrpath)
-	if err != nil {
-		return errors.New(fmt.Sprintf("Could not read file %s: %v", hocrpath, err))
-	}
-	// TODO: change hocr.Parse to take a Reader rather than []byte
-	h, err := hocr.Parse(file)
-	if err != nil {
-		return errors.New(fmt.Sprintf("Could not parse hocr in file %s: %v", hocrpath, err))
-	}
-
-	f, err := os.Open(imgpath)
-	defer f.Close()
-	if err != nil {
-		return errors.New(fmt.Sprintf("Could not open file %s: %v", imgpath, err))
-	}
-	img, _, err := image.Decode(f)
-	if err != nil {
-		return errors.New(fmt.Sprintf("Could not decode image: %v", err))
-	}
-	b := img.Bounds()
-	pdf.AddPageFormat("P", gofpdf.SizeType{Wd: pxToPt(b.Dx()), Ht: pxToPt(b.Dy())})
-
-	// TODO: check for errors in pdf as going through
-
-	_ = pdf.RegisterImageOptions(imgpath, gofpdf.ImageOptions{})
-	pdf.ImageOptions(imgpath, 0, 0, pxToPt(b.Dx()), pxToPt(b.Dy()), false, gofpdf.ImageOptions{}, 0, "")
-
-	pdf.SetTextRenderingMode(gofpdf.TextRenderingModeInvisible)
-
-	for _, l := range h.Lines {
-		coords, err := hocr.BoxCoords(l.Title)
-		if err != nil {
-			continue
-		}
-		pdf.SetXY(pxToPt(coords[0]), pxToPt(coords[1]))
-		pdf.CellFormat(pxToPt(coords[2]), pxToPt(coords[3]), html.UnescapeString(hocr.LineText(l)), "", 0, "T", false, 0, "")
-	}
-	return nil
-}
-
-func savePdf(pdf *gofpdf.Fpdf, p string) error {
-	return pdf.OutputFileAndClose(p)
-}
-
-func walker(pdf *gofpdf.Fpdf) filepath.WalkFunc {
+func walker(pdf Pdfer) filepath.WalkFunc {
 	return func(fpath string, info os.FileInfo, err error) error {
 		if info.IsDir() {
 			return nil
@@ -104,7 +42,7 @@ func walker(pdf *gofpdf.Fpdf) filepath.WalkFunc {
 		} else {
 			imgpath = strings.TrimSuffix(fpath, ".hocr") + ".png"
 		}
-		return addPage(pdf, imgpath, fpath)
+		return pdf.AddPage(imgpath, fpath)
 	}
 }
 
@@ -123,14 +61,15 @@ func main() {
 		return
 	}
 
-	pdf := setupPdf()
+	pdf := new(bookpipeline.Fpdf)
+	pdf.Setup()
 
 	err := filepath.Walk(flag.Arg(0), walker(pdf))
 	if err != nil {
 		log.Fatalln("Failed to walk", flag.Arg(0), err)
 	}
 
-	err = savePdf(pdf, flag.Arg(1))
+	err = pdf.Save(flag.Arg(1))
 	if err != nil {
 		log.Fatalln("Failed to save", flag.Arg(1), err)
 	}
diff --git a/pdf.go b/pdf.go
new file mode 100644
index 0000000..e7480fe
--- /dev/null
+++ b/pdf.go
@@ -0,0 +1,90 @@
+package bookpipeline
+
+import (
+	"errors"
+	"fmt"
+	"html"
+	"image"
+	_ "image/jpeg"
+	_ "image/png"
+	"io/ioutil"
+	"os"
+
+	//"rescribe.xyz/gofpdf@addtextrenderingmode"
+	"rescribe.xyz/gofpdf"
+	"rescribe.xyz/utils/pkg/hocr"
+)
+
+const pageWidth = 5 // pageWidth in inches
+
+// pxToPt converts a pixel value into a pt value (72 pts per inch)
+// This uses pageWidth to determine the appropriate value
+func pxToPt(i int) float64 {
+	return float64(i) / pageWidth
+}
+
+type Fpdf struct {
+	fpdf *gofpdf.Fpdf
+}
+
+// Setup creates a new PDF with appropriate settings and fonts
+// TODO: find a font that's closer to the average dimensions of the
+//       text we're dealing with
+// TODO: once we have a good font, embed it in the binary as bytes
+func (p *Fpdf) Setup() error {
+	p.fpdf = gofpdf.New("P", "pt", "A4", "")
+	// Even though it's invisible, we need to add a font which can do
+	// UTF-8 so that text renders correctly.
+	p.fpdf.AddUTF8Font("dejavu", "", "DejaVuSansCondensed.ttf")
+	p.fpdf.SetFont("dejavu", "", 10)
+	p.fpdf.SetAutoPageBreak(false, float64(0))
+	return p.fpdf.Error()
+}
+
+// AddPage adds a page to the pdf with an image and (invisible)
+// text from an hocr file
+func (p *Fpdf) AddPage(imgpath, hocrpath string) error {
+	file, err := ioutil.ReadFile(hocrpath)
+	if err != nil {
+		return errors.New(fmt.Sprintf("Could not read file %s: %v", hocrpath, err))
+	}
+	// TODO: change hocr.Parse to take a Reader rather than []byte
+	h, err := hocr.Parse(file)
+	if err != nil {
+		return errors.New(fmt.Sprintf("Could not parse hocr in file %s: %v", hocrpath, err))
+	}
+
+	f, err := os.Open(imgpath)
+	defer f.Close()
+	if err != nil {
+		return errors.New(fmt.Sprintf("Could not open file %s: %v", imgpath, err))
+	}
+	img, _, err := image.Decode(f)
+	if err != nil {
+		return errors.New(fmt.Sprintf("Could not decode image: %v", err))
+	}
+	b := img.Bounds()
+	p.fpdf.AddPageFormat("P", gofpdf.SizeType{Wd: pxToPt(b.Dx()), Ht: pxToPt(b.Dy())})
+
+	// TODO: check for errors in pdf as going through
+
+	_ = p.fpdf.RegisterImageOptions(imgpath, gofpdf.ImageOptions{})
+	p.fpdf.ImageOptions(imgpath, 0, 0, pxToPt(b.Dx()), pxToPt(b.Dy()), false, gofpdf.ImageOptions{}, 0, "")
+
+	p.fpdf.SetTextRenderingMode(gofpdf.TextRenderingModeInvisible)
+
+	for _, l := range h.Lines {
+		coords, err := hocr.BoxCoords(l.Title)
+		if err != nil {
+			continue
+		}
+		p.fpdf.SetXY(pxToPt(coords[0]), pxToPt(coords[1]))
+		p.fpdf.CellFormat(pxToPt(coords[2]), pxToPt(coords[3]), html.UnescapeString(hocr.LineText(l)), "", 0, "T", false, 0, "")
+	}
+	return p.fpdf.Error()
+}
+
+// Save saves the PDF to the file at path
+func (p *Fpdf) Save(path string) error {
+	return p.fpdf.OutputFileAndClose(path)
+}