build: basis of build command

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

build/output.go

@@ -0,0 +1,86 @@
+package build
+
+import (
+	"encoding/csv"
+	"os"
+	"strings"
+
+	"github.com/moby/buildkit/client"
+	"github.com/pkg/errors"
+)
+
+func ParseOutputs(inp []string) ([]client.ExportEntry, error) {
+	var outs []client.ExportEntry
+	if len(inp) == 0 {
+		return nil, nil
+	}
+	for _, s := range inp {
+		csvReader := csv.NewReader(strings.NewReader(s))
+		fields, err := csvReader.Read()
+		if err != nil {
+			return nil, err
+		}
+		if len(fields) == 1 && fields[0] == s {
+			outs = append(outs, client.ExportEntry{
+				Type:      "local",
+				OutputDir: s,
+			})
+			continue
+		}
+
+		out := client.ExportEntry{
+			Attrs: map[string]string{},
+		}
+		for _, field := range fields {
+			parts := strings.SplitN(field, "=", 2)
+			if len(parts) != 2 {
+				return nil, errors.Errorf("invalid value %s", field)
+			}
+			key := strings.ToLower(parts[0])
+			value := parts[1]
+			switch key {
+			case "type":
+				out.Type = value
+			default:
+				out.Attrs[key] = value
+			}
+		}
+		if out.Type == "" {
+			return nil, errors.Errorf("type is required for output")
+		}
+
+		// handle client side
+		switch out.Type {
+		case "local":
+			dest, ok := out.Attrs["dest"]
+			if !ok {
+				return nil, errors.Errorf("dest is required for local output")
+			}
+			out.OutputDir = dest
+			delete(out.Attrs, "dest")
+		case "oci", "dest":
+			dest, ok := out.Attrs["dest"]
+			if !ok {
+				if out.Type != "docker" {
+					return nil, errors.Errorf("dest is required for %s output", out.Type)
+				}
+			} else {
+				if dest == "-" {
+					out.Output = os.Stdout
+				} else {
+					f, err := os.Open(dest)
+					if err != nil {
+						out.Output = f
+					}
+				}
+				delete(out.Attrs, "dest")
+			}
+		case "registry":
+			out.Type = "iamge"
+			out.Attrs["push"] = "true"
+		}
+
+		outs = append(outs, out)
+	}
+	return outs, nil
+}