Feature/#103 navigate back (#107)

* #103 Added NAVIGATE_BACK function

* Commented out debugging test

* Updated implementation

pkg/stdlib/html/lib.go

@@ -24,6 +24,7 @@ func NewLib() map[string]core.Function {
 		"CLICK":           Click,
 		"CLICK_ALL":       ClickAll,
 		"NAVIGATE":        Navigate,
+		"NAVIGATE_BACK":   NavigateBack,
 		"INPUT":           Input,
 		"INNER_HTML":      InnerHTML,
 		"INNER_HTML_ALL":  InnerHTMLAll,

pkg/stdlib/html/navigate_back.go

@@ -0,0 +1,62 @@
+package html
+
+import (
+	"context"
+	"github.com/MontFerret/ferret/pkg/html/dynamic"
+	"github.com/MontFerret/ferret/pkg/runtime/core"
+	"github.com/MontFerret/ferret/pkg/runtime/values"
+)
+
+/*
+ * Navigates a document back within its navigation history.
+ * The operation blocks the execution until the page gets loaded.
+ * If the history is empty, the function returns FALSE.
+ * @param doc (Document) - Target document.
+ * @param entry (Int, optional) - Optional value indicating how many pages to skip. Default 1.
+ * @param timeout (Int, optional) - Optional timeout. Default is 5000.
+ * @returns (Boolean) - Returns TRUE if history exists and the operation succeeded, otherwise FALSE.
+ */
+func NavigateBack(_ context.Context, args ...core.Value) (core.Value, error) {
+	err := core.ValidateArgs(args, 1, 3)
+
+	if err != nil {
+		return values.False, err
+	}
+
+	err = core.ValidateType(args[0], core.HTMLDocumentType)
+
+	if err != nil {
+		return values.None, err
+	}
+
+	doc, ok := args[0].(*dynamic.HTMLDocument)
+
+	if !ok {
+		return values.False, core.Errors(core.ErrInvalidType, ErrNotDynamic)
+	}
+
+	skip := values.NewInt(1)
+	timeout := values.NewInt(defaultTimeout)
+
+	if len(args) > 1 {
+		err = core.ValidateType(args[1], core.IntType)
+
+		if err != nil {
+			return values.None, err
+		}
+
+		skip = args[1].(values.Int)
+	}
+
+	if len(args) > 2 {
+		err = core.ValidateType(args[2], core.IntType)
+
+		if err != nil {
+			return values.None, err
+		}
+
+		timeout = args[2].(values.Int)
+	}
+
+	return doc.NavigateBack(skip, timeout)
+}