Add sorting functionality

There is a command and config option. The criteria are a list of the
sort criterion and each can be individually reversed.

This only includes support for sorting in the maildir backend currently.
The other backends are not supported in this patch.

1 files changed, 56 insertions, 0 deletions

diff --git a/lib/sort/sort.go b/lib/sort/sort.go
new file mode 100644
index 00000000..89c36a90
--- /dev/null
+++ b/lib/sort/sort.go
@@ -0,0 +1,56 @@
+package sort
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"git.sr.ht/~sircmpwn/aerc/worker/types"
+)
+
+func GetSortCriteria(args []string) ([]*types.SortCriterion, error) {
+	var sortCriteria []*types.SortCriterion
+	reverse := false
+	for _, arg := range args {
+		if arg == "-r" {
+			reverse = true
+			continue
+		}
+		field, err := parseSortField(arg)
+		if err != nil {
+			return nil, err
+		}
+		sortCriteria = append(sortCriteria, &types.SortCriterion{
+			Field:   field,
+			Reverse: reverse,
+		})
+		reverse = false
+	}
+	if reverse {
+		return nil, errors.New("Expected argument to reverse")
+	}
+	return sortCriteria, nil
+}
+
+func parseSortField(arg string) (types.SortField, error) {
+	switch strings.ToLower(arg) {
+	case "arrival":
+		return types.SortArrival, nil
+	case "cc":
+		return types.SortCc, nil
+	case "date":
+		return types.SortDate, nil
+	case "from":
+		return types.SortFrom, nil
+	case "read":
+		return types.SortRead, nil
+	case "size":
+		return types.SortSize, nil
+	case "subject":
+		return types.SortSubject, nil
+	case "to":
+		return types.SortTo, nil
+	default:
+		return types.SortArrival, fmt.Errorf("%v is not a valid sort criterion", arg)
+	}
+}