report: add method loadReport

The loadReport method load the ReportFile from the current directory,
as written by [report.write] method.

1 files changed, 94 insertions, 5 deletions

diff --git a/report.go b/report.go
index 5ac725e..eb68b6c 100644
--- a/report.go
+++ b/report.go
@@ -6,20 +6,109 @@ package spdxconv
 import (
 	"bytes"
 	"encoding/csv"
+	"errors"
 	"fmt"
+	"io"
 	"os"
+	"strconv"
+	"strings"
 )
 
 // ReportFile contains the list of files that will be converted or inserted
 // with SPDX identifiers.
 const ReportFile = `spdxconv.report`
 
+const reportMetaPrefix = `//spdxconv:`
+
+const (
+	reportGroupRegular = `regular`
+	reportGroupBinary  = `binary`
+	reportGroupUnknown = `unknown`
+)
+
+const v1FieldsPerRecord = 4
+
 type report struct {
 	listRegular []*file
 	listBinary  []*file
 	listUnknown []*file
 }
 
+// loadReport load the [ReportFile] from the current directory.
+func loadReport() (rep *report, err error) {
+	var logp = `loadReport`
+	var content []byte
+	content, err = os.ReadFile(ReportFile)
+	if err != nil {
+		return nil, fmt.Errorf(`%s: %w`, logp, err)
+	}
+
+	br := bytes.NewReader(content)
+	csvr := csv.NewReader(br)
+	csvr.FieldsPerRecord = v1FieldsPerRecord
+	csvr.ReuseRecord = true
+	csvr.TrimLeadingSpace = true
+
+	rep = &report{}
+	var group string
+	var record []string
+	var fields []string
+	var f *file
+	var n int
+
+	record, err = csvr.Read()
+	for !errors.Is(err, io.EOF) {
+		if errors.Is(err, csv.ErrFieldCount) {
+			if !strings.HasPrefix(record[0], reportMetaPrefix) {
+				goto next
+			}
+			group = strings.TrimPrefix(record[0], reportMetaPrefix)
+			switch group {
+			case reportGroupRegular, reportGroupBinary, reportGroupUnknown:
+				// OK
+			default:
+				group = ``
+			}
+			goto next
+		}
+
+		f = &file{
+			path:          record[0],
+			copyrightYear: record[2],
+		}
+		fields = strings.Split(record[1], `:`)
+		f.licenseID = fields[0]
+		if len(fields) == 2 && fields[0] == valExist {
+			f.idxLicenseID, err = strconv.Atoi(fields[1])
+			if err != nil {
+				return nil, fmt.Errorf(`%s: line %d: %w`, logp, n, err)
+			}
+		}
+		fields = strings.Split(record[3], `:`)
+		f.copyrightText = fields[0]
+		if len(fields) == 2 && fields[0] == valExist {
+			f.idxCopyrightText, err = strconv.Atoi(fields[1])
+			if err != nil {
+				return nil, fmt.Errorf(`%s: line %d: %w`, logp, n, err)
+			}
+		}
+
+		switch group {
+		case reportGroupRegular:
+			rep.listRegular = append(rep.listRegular, f)
+		case reportGroupBinary:
+			rep.listBinary = append(rep.listBinary, f)
+		case reportGroupUnknown:
+			rep.listUnknown = append(rep.listUnknown, f)
+		}
+	next:
+		record, err = csvr.Read()
+		n++
+	}
+
+	return rep, nil
+}
+
 func newReport() (rep *report) {
 	rep = &report{}
 	return rep
@@ -48,13 +137,13 @@ func (rep *report) scan(conv *SPDXConv, listFile []string) (err error) {
 
 func (rep *report) write() (err error) {
 	var buf bytes.Buffer
-	buf.WriteString("//spdxconv:version:v1\n")
-	buf.WriteString("//spdxconv:header:path,license_id,year,copyright_id\n")
+	buf.WriteString(reportMetaPrefix + "version:v1\n")
+	buf.WriteString(reportMetaPrefix + "header:path,license_id,year,copyright_id\n")
 
 	var csvw = csv.NewWriter(&buf)
 	var record = make([]string, 4)
 
-	buf.WriteString("//spdxconv:regular\n")
+	buf.WriteString(reportMetaPrefix + reportGroupRegular + "\n")
 	for _, file := range rep.listRegular {
 		record[0] = file.path
 		record[1] = file.licenseID
@@ -67,7 +156,7 @@ func (rep *report) write() (err error) {
 	}
 	csvw.Flush()
 
-	buf.WriteString("//spdxconv:binary\n")
+	buf.WriteString(reportMetaPrefix + reportGroupBinary + "\n")
 	for _, file := range rep.listBinary {
 		record[0] = file.path
 		record[1] = file.licenseID
@@ -80,7 +169,7 @@ func (rep *report) write() (err error) {
 	}
 	csvw.Flush()
 
-	buf.WriteString("//spdxconv:unknown\n")
+	buf.WriteString(reportMetaPrefix + reportGroupUnknown + "\n")
 	for _, file := range rep.listUnknown {
 		record[0] = file.path
 		record[1] = file.licenseID