Merge pull request #23 from ryeguard/sr/cli

feat(cli): minimal cli

Author: ryeguard

cmd/calc/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/ryeguard/ddbcalc"
+)
+
+var fileFlag = flag.String("file", "", "The file path and name to read. Must be a json file. Required.")
+
+func readJSON(file string) (map[string]interface{}, error) {
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, fmt.Errorf("open: %w", err)
+	}
+	defer f.Close()
+
+	b, err := io.ReadAll(f)
+	if err != nil {
+		return nil, fmt.Errorf("read: %w", err)
+	}
+
+	var data map[string]interface{}
+	err = json.Unmarshal(b, &data)
+	if err != nil {
+		return nil, fmt.Errorf("unmarshal: %w", err)
+	}
+
+	return data, nil
+}
+
+func main() {
+	flag.Parse()
+
+	if *fileFlag == "" {
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	data, err := readJSON(*fileFlag)
+	if err != nil {
+		panic(fmt.Sprintf("readJSON: %v", err))
+	}
+
+	size, err := ddbcalc.StructSizeInBytes(data)
+	if err != nil {
+		panic(fmt.Sprintf("StructSizeInBytes: %v", err))
+	}
+
+	fmt.Printf("The resulting DynamoDB item size is %d bytes\n", size)
+}

cmd/calc/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestReadJSON(t *testing.T) {
+	t.Run("read non-existent file", func(t *testing.T) {
+		_, err := readJSON("non-existent.json")
+		if err == nil {
+			t.Fatalf("readJSON: expected error, got nil")
+		}
+		if !strings.HasPrefix(err.Error(), "open") {
+			t.Fatalf("readJSON: expected error to start with 'open', got %v", err)
+		}
+	})
+
+	t.Run("read invalid file", func(t *testing.T) {
+		_, err := readJSON("../../testdata/test_invalid.json")
+		if err == nil {
+			t.Fatalf("readJSON: expected error, got nil")
+		}
+		if !strings.HasPrefix(err.Error(), "unmarshal") {
+			t.Fatalf("readJSON: expected error to start with 'unmarshal', got %v", err)
+		}
+	})
+
+	t.Run("read valid file", func(t *testing.T) {
+		actual, err := readJSON("../../testdata/test_int.json")
+		if err != nil {
+			t.Fatalf("readJSON: %v", err)
+		}
+		if len(actual) == 0 {
+			t.Fatalf("readJSON: expected non-empty map, got empty map")
+		}
+		if _, ok := actual["IntField"]; !ok {
+			t.Fatalf("readJSON: expected key IntField, got %v", actual)
+		}
+	})
+}

testdata/test_invalid.json

@@ -0,0 +1,3 @@
+{
+    "IntField": "101 
+}