v0.1.0 initial commit

internal/export/export.go

@@ -0,0 +1,55 @@
+package export
+
+import (
+	"bufio"
+	"io"
+	"os"
+
+	"github.com/lixenwraith/vif-log/internal/logfile"
+)
+
+// Exporter serialises a record set. JSONL is the only implementation; a plain
+// text renderer is the second.
+type Exporter interface {
+	Ext() string
+	Write(w io.Writer, rd *logfile.Reader, metas []logfile.Meta) (int, error)
+}
+
+// JSONL writes the verbatim source lines, so an export reopens in the viewer.
+type JSONL struct{}
+
+func (JSONL) Ext() string { return ".jsonl" }
+
+func (JSONL) Write(w io.Writer, rd *logfile.Reader, metas []logfile.Meta) (int, error) {
+	bw := bufio.NewWriterSize(w, 1<<16)
+	n := 0
+	for _, m := range metas {
+		line, err := rd.Line(m)
+		if err != nil {
+			return n, err
+		}
+		if _, err := bw.Write(line); err != nil {
+			return n, err
+		}
+		if err := bw.WriteByte('\n'); err != nil {
+			return n, err
+		}
+		n++
+	}
+	return n, bw.Flush()
+}
+
+// ToFile writes metas to path. The file is created exclusively: an export can
+// never overwrite a log.
+func ToFile(path string, e Exporter, rd *logfile.Reader, metas []logfile.Meta) (int, error) {
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o644)
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+	n, err := e.Write(f, rd, metas)
+	if err != nil {
+		return n, err
+	}
+	return n, f.Sync()
+}