add db package

3 files changed, 193 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 27acc3c..441f242 100644
--- a/Makefile
+++ b/Makefile
@@ -8,3 +8,7 @@ fern: fmt
 
 fmt:
 	go fmt ${MOD} ${MOD}/config ${MOD}/file ${MOD}/schema
+
+test:
+	go test -v ${MOD}/db
+.PHONY: test
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
+}
diff --git a/db/db_test.go b/db/db_test.go
new file mode 100644
index 0000000..5a2a983
--- /dev/null
+++ b/db/db_test.go
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: ISC
+// Copyright © 2021 siddharth <s@ricketyspace.net>
+
+package db
+
+import (
+	"os"
+	"path"
+	"testing"
+)
+
+func stringsContain(haystack []string, needle string) bool {
+	for _, s := range haystack {
+		if s == needle {
+			return true
+		}
+	}
+	return false
+}
+
+func TestOpenPathNotSet(t *testing.T) {
+	// Set custom path for db.
+	dbPath = ""
+	defer os.Remove(dbPath)
+
+	_, err := Open()
+	if err == nil {
+		t.Errorf("Error: db.Open did not fail when dbPath is empty\n")
+		return
+	}
+	if err.Error() != "FernDB path not set" {
+		t.Errorf("Error: db.Open wrong error message when dbPath is empty\n")
+		return
+	}
+}
+
+func TestOpenNewDB(t *testing.T) {
+	// Set custom path for db.
+	dbPath = path.Join(os.TempDir(), "fern-db.json")
+	defer os.Remove(dbPath)
+
+	// Open empty db.
+	db, err := Open()
+	if err != nil {
+		t.Errorf("db.Open failed: %v", err.Error())
+		return
+	}
+
+	// Verify that 'downloaded' is initialized
+	if db.downloaded == nil {
+		t.Errorf("db.downloaded is nil")
+		return
+	}
+}
+
+func TestOpenExistingDB(t *testing.T) {
+	// Set custom path for db.
+	dbPath = path.Join(os.TempDir(), "fern-db.json")
+	defer os.Remove(dbPath)
+
+	// Write a sample test db to fern-db.json
+	testDBJSON := []byte(`{"mkbhd":["rivian","v-raptor","m1-imac"],"npr":["william-prince","joy-oladokun","lucy-ducas"],"simone":["weightless","ugly-desks","safety-hat"]}`)
+	dbFile, err := os.Create(dbPath)
+	if err != nil {
+		t.Errorf("Unable to create fern-db.json: %v", err.Error())
+	}
+	n, err := dbFile.Write(testDBJSON)
+	if len(testDBJSON) != n {
+		t.Errorf("Write to fern-db.json failed: %v", err.Error())
+	}
+	dbFile.Close()
+
+	// Open the db.
+	db, err := Open()
+	if err != nil {
+		t.Errorf("db.Open failed: %v", err.Error())
+		return
+	}
+
+	// Validate db.downloaded.
+	var entries, expectedEntries []string
+	var ok bool
+	if len(db.downloaded) != 3 {
+		t.Errorf("db.downloaded does not contain 3 feeds")
+		return
+	}
+	// mkbhd
+	if entries, ok = db.downloaded["mkbhd"]; !ok {
+		t.Errorf("db.downloaded does not contain mkbhd")
+		return
+	}
+	expectedEntries = []string{"rivian", "v-raptor", "m1-imac"}
+	for _, entry := range entries {
+		if !stringsContain(expectedEntries, entry) {
+			t.Errorf("%v does not exist in db.downloaded[mkbhd]", entry)
+			return
+		}
+	}
+	// simone
+	if entries, ok = db.downloaded["simone"]; !ok {
+		t.Errorf("db.downloaded does not contain simone")
+		return
+	}
+	expectedEntries = []string{"weightless", "ugly-desks", "safety-hat"}
+	for _, entry := range entries {
+		if !stringsContain(expectedEntries, entry) {
+			t.Errorf("%v does not exist in db.downloaded[simone]", entry)
+			return
+		}
+	}
+	// npr
+	if entries, ok = db.downloaded["npr"]; !ok {
+		t.Errorf("db.downloaded does not contain npr")
+		return
+	}
+	expectedEntries = []string{"william-prince", "lucy-ducas", "joy-oladokun"}
+	for _, entry := range entries {
+		if !stringsContain(expectedEntries, entry) {
+			t.Errorf("%v does not exist in db.downloaded[npr]", entry)
+			return
+		}
+	}
+}