add db package

1 files changed, 66 insertions, 0 deletions

diff --git a/db/db.go b/db/db.go
new file mode 100644
index 0000000..2d6a4d5
--- /dev/null
+++ b/db/db.go
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: ISC
+// Copyright © 2021 siddharth <s@ricketyspace.net>
+
+package db
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path"
+
+	"ricketyspace.net/fern/file"
+)
+
+var dbPath string
+
+type FernDB struct {
+	// Key: feed-id
+	// Value: feed-id's entries that were downloaded
+	downloaded map[string][]string
+}
+
+func init() {
+	dbPath = "" // Reset.
+
+	// Construct default dbPath
+	h, err := os.UserHomeDir()
+	if err != nil {
+		return
+	}
+	dbPath = path.Join(h, ".config", "fern", "db.json")
+
+}
+
+func Open() (*FernDB, error) {
+	if len(dbPath) == 0 {
+		return nil, fmt.Errorf("FernDB path not set")
+	}
+
+	// Check if db exists.
+	_, err := os.Stat(dbPath)
+	if err != nil {
+		// db does not exist yet; create an empty one.
+		db := new(FernDB)
+		db.downloaded = make(map[string][]string)
+		return db, nil
+	}
+
+	// Read db from disk.
+	f, err := os.Open(dbPath)
+	if err != nil {
+		return nil, err
+	}
+	bs, err := file.Read(f)
+	if err != nil {
+		return nil, err
+	}
+
+	// Unmarshal db into an object.
+	db := new(FernDB)
+	err = json.Unmarshal(bs, &db.downloaded)
+	if err != nil {
+		return nil, err
+	}
+	return db, nil
+}