Add initial project structure with core functionality for book and stationery uploads

- Created main application entry point in `main.go`.
- Added configuration management in `config/config.go` and tests in `config/config_test.go`.
- Implemented handlers for book and stationery uploads in `handlers/book.go` and `handlers/stationery.go`, including validation logic.
- Established database connection and services in `services/database.go` and `services/book_service.go`.
- Defined models for books and stationery in `models/book.go` and `models/stationery.go`.
- Set up Firebase integration for image uploads in `services/firebase.go`.
- Created migration scripts for database schema in `migrations/001_create_tables.sql` and subsequent updates.
- Added CORS and error handling middleware.
- Included comprehensive tests for handlers, services, and utilities.
- Documented API endpoints and usage in `README.md` and migration instructions in `migrations/README.md`.
- Introduced `.gitignore` to exclude unnecessary files and directories.
- Added Go module support with `go.mod` and `go.sum` files.
- Implemented utility functions for slug generation and validation in `utils/slug.go` and `utils/validation.go`.

utils/validation_test.go

@@ -0,0 +1,195 @@
+package utils
+
+import "testing"
+
+func TestValidateBookFields(t *testing.T) {
+	tests := []struct {
+		name            string
+		bookName        string
+		cost            string
+		price           string
+		discount        string
+		quantity        string
+		publisherAuthor string
+		category        string
+		description     string
+		wantErrors      int
+	}{
+		{
+			name:            "valid fields",
+			bookName:        "Test Book",
+			cost:            "10.50",
+			price:           "15.99",
+			discount:        "0",
+			quantity:        "100",
+			publisherAuthor: "Test Publisher",
+			category:        "Fiction",
+			description:     "A test book",
+			wantErrors:      0,
+		},
+		{
+			name:            "missing book_name",
+			bookName:        "",
+			cost:            "10.50",
+			price:           "15.99",
+			quantity:        "100",
+			publisherAuthor: "Test Publisher",
+			category:        "Fiction",
+			wantErrors:      1,
+		},
+		{
+			name:            "invalid cost",
+			bookName:        "Test Book",
+			cost:            "-10",
+			price:           "15.99",
+			quantity:        "100",
+			publisherAuthor: "Test Publisher",
+			category:        "Fiction",
+			wantErrors:      1,
+		},
+		{
+			name:            "missing category",
+			bookName:        "Test Book",
+			cost:            "10.50",
+			price:           "15.99",
+			quantity:        "100",
+			publisherAuthor: "Test Publisher",
+			category:        "",
+			wantErrors:      1,
+		},
+		{
+			name:            "description too long",
+			bookName:        "Test Book",
+			cost:            "10.50",
+			price:           "15.99",
+			quantity:        "100",
+			publisherAuthor: "Test Publisher",
+			category:        "Fiction",
+			description:     string(make([]byte, 1001)), // 1001 characters
+			wantErrors:      1,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			errors := ValidateBookFields(
+				tt.bookName,
+				tt.cost,
+				tt.price,
+				tt.discount,
+				tt.quantity,
+				tt.publisherAuthor,
+				tt.category,
+				tt.description,
+			)
+
+			if len(errors) != tt.wantErrors {
+				t.Errorf("ValidateBookFields() returned %d errors, want %d", len(errors), tt.wantErrors)
+			}
+		})
+	}
+}
+
+func TestValidateStationeryFields(t *testing.T) {
+	tests := []struct {
+		name           string
+		stationeryName string
+		cost           string
+		price          string
+		quantity       string
+		category       string
+		wantErrors     int
+	}{
+		{
+			name:           "valid fields",
+			stationeryName: "Test Pen",
+			cost:           "2.50",
+			price:          "5.99",
+			quantity:       "200",
+			category:       "Writing",
+			wantErrors:     0,
+		},
+		{
+			name:           "missing stationery_name",
+			stationeryName: "",
+			cost:           "2.50",
+			price:          "5.99",
+			quantity:       "200",
+			category:       "Writing",
+			wantErrors:     1,
+		},
+		{
+			name:           "invalid quantity",
+			stationeryName: "Test Pen",
+			cost:           "2.50",
+			price:          "5.99",
+			quantity:       "-10",
+			category:       "Writing",
+			wantErrors:     1,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			errors := ValidateStationeryFields(
+				tt.stationeryName,
+				tt.cost,
+				tt.price,
+				"",
+				tt.quantity,
+				tt.category,
+				"",
+			)
+
+			if len(errors) != tt.wantErrors {
+				t.Errorf("ValidateStationeryFields() returned %d errors, want %d", len(errors), tt.wantErrors)
+			}
+		})
+	}
+}
+
+func TestValidateFileType(t *testing.T) {
+	tests := []struct {
+		name        string
+		contentType string
+		wantErr     bool
+	}{
+		{"valid PNG", "image/png", false},
+		{"valid JPEG", "image/jpeg", false},
+		{"valid JPG", "image/jpg", false},
+		{"valid WEBP", "image/webp", false},
+		{"invalid type", "image/gif", true},
+		{"invalid type", "text/plain", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ValidateFileType(tt.contentType)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ValidateFileType() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+func TestValidateFileSize(t *testing.T) {
+	tests := []struct {
+		name    string
+		size    int64
+		maxSize int64
+		wantErr bool
+	}{
+		{"valid size", 5 * 1024 * 1024, 10 * 1024 * 1024, false},
+		{"exact max size", 10 * 1024 * 1024, 10 * 1024 * 1024, false},
+		{"too large", 11 * 1024 * 1024, 10 * 1024 * 1024, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ValidateFileSize(tt.size, tt.maxSize)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("ValidateFileSize() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}