1 files changed, 52 insertions, 0 deletions
diff --git a/sent.go b/sent.go
new file mode 100644
index 0000000..dc16051
--- /dev/null
+++ b/sent.go
@@ -0,0 +1,52 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+	"slices"
+)
+
+func readSent(filename string) ([]flat, error) {
+	data, err := os.ReadFile(filename)
+	sent := make([]flat, 0)
+	if err != nil {
+		// This is fine, as we might just started and didn't dump
+		// anything into sent file yet.
+		if errors.Is(err, os.ErrNotExist) {
+			return sent, nil
+		}
+		return sent, err
+	}
+	err = json.Unmarshal(data, &sent)
+	if err != nil {
+		return sent, err
+	}
+	if !slices.IsSortedFunc(sent, compareID) {
+		return nil, errors.New("Invalid sent: not sorted")
+	}
+	return sent, nil
+}
+
+func removeAlreadySent(fetched []flat, sent []flat) []flat {
+	if !slices.IsSortedFunc(sent, compareID) {
+		panic("Sent expected to be sorted")
+	}
+	recent := make([]flat, 0)
+	for _, f := range fetched {
+		_, found := slices.BinarySearchFunc(sent, f, compareID)
+		if found {
+			continue
+		}
+		recent = append(recent, f)
+	}
+	return recent
+}
+
+func writeSent(sent []flat, filename string) error {
+	jsonData, err := json.Marshal(sent)
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(filename, jsonData, 0644)
+}