Implement Array.prototype: concat(), push(), pop() and join() (#52)

* First draft of Array prototype object

* First draft of Array prototype object

* Update to working Array object

* Remove unneeded HashMap import

* Fix indexing by removing private internal HashMap

* Fix formatting issues with cargo fmt

* Implement Array.prototype.concat()

* Implement Array.prototype.concat()

* Cargo format fix

* Implement push, pop and join

* Add documenation links to new methods

src/lib/js/array.rs

@@ -3,29 +3,56 @@ use crate::js::object::{Property, PROTOTYPE};
 use crate::js::value::{from_value, to_value, ResultValue, Value, ValueData};
 use gc::Gc;
 
+/// Utility function for creating array objects: array_obj can be any array with
+/// prototype already set (it will be wiped and recreated from array_contents)
+fn create_array_object(array_obj: Value, array_contents: Vec<Value>) -> ResultValue {
+    let array_obj_ptr = array_obj.clone();
+
+    // Wipe existing contents of the array object
+    let orig_length: i32 = from_value(array_obj.get_field_slice("length")).unwrap();
+    for n in 0..orig_length {
+        array_obj_ptr.remove_prop(&n.to_string());
+    }
+
+    for (n, value) in array_contents.iter().enumerate() {
+        array_obj_ptr.set_field(n.to_string(), value.clone());
+    }
+
+    array_obj_ptr.set_field_slice("length", to_value(array_contents.len() as i32));
+    Ok(array_obj_ptr)
+}
+
+/// Utility function which takes an existing array object and puts additional
+/// values on the end, correctly rewriting the length
+fn add_to_array_object(array_ptr: Value, add_values: Vec<Value>) -> ResultValue {
+    let orig_length: i32 = from_value(array_ptr.get_field_slice("length")).unwrap();
+
+    for (n, value) in add_values.iter().enumerate() {
+        let new_index = orig_length + (n as i32);
+        array_ptr.set_field(new_index.to_string(), value.clone());
+    }
+
+    array_ptr.set_field_slice("length", to_value(orig_length + add_values.len() as i32));
+
+    Ok(array_ptr)
+}
+
 /// Create a new array
 pub fn make_array(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
-    let this_ptr = this.clone();
     // Make a new Object which will internally represent the Array (mapping
     // between indices and values): this creates an Object with no prototype
+    this.set_field_slice("length", to_value(0i32));
     match args.len() {
-        0 => {
-            this_ptr.set_field_slice("length", to_value(0i32));
-        }
+        0 => create_array_object(this, Vec::new()),
         1 => {
-            let length_chosen: i32 = from_value(args[0].clone()).unwrap();
-            this_ptr.set_field_slice("length", to_value(length_chosen));
-        }
-        n => {
-            this_ptr.set_field_slice("length", to_value(n));
-            for k in 0..n {
-                let index_str = k.to_string();
-                this_ptr.set_field(index_str, args[k].clone());
+            let array = create_array_object(this, Vec::new()).unwrap();
+            let size: i32 = from_value(args[0].clone()).unwrap();
+            array.set_field_slice("length", to_value(size));
+            Ok(array)
         }
+        _ => create_array_object(this, args),
     }
 }
-    Ok(this_ptr)
-}
 
 /// Get an array's length
 pub fn get_array_length(this: Value, _: Value, _: Vec<Value>) -> ResultValue {
@@ -34,6 +61,91 @@ pub fn get_array_length(this: Value, _: Value, _: Vec<Value>) -> ResultValue {
     Ok(this.get_field_slice("length"))
 }
 
+/// Array.prototype.concat(...arguments)
+///
+/// When the concat method is called with zero or more arguments, it returns an
+/// array containing the array elements of the object followed by the array
+/// elements of each argument in order.
+/// https://tc39.es/ecma262/#sec-array.prototype.concat
+pub fn concat(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
+    if args.len() == 0 {
+        // If concat is called with no arguments, it returns the original array
+        return Ok(this.clone());
+    }
+
+    // Make a new array (using this object as the prototype basis for the new
+    // one)
+    let mut new_values: Vec<Value> = Vec::new();
+
+    let this_length: i32 = from_value(this.get_field_slice("length")).unwrap();
+    for n in 0..this_length {
+        new_values.push(this.get_field(n.to_string()));
+    }
+
+    for concat_array in args {
+        let concat_length: i32 = from_value(concat_array.get_field_slice("length")).unwrap();
+        for n in 0..concat_length {
+            new_values.push(concat_array.get_field(n.to_string()));
+        }
+    }
+
+    create_array_object(this, new_values)
+}
+
+/// Array.prototype.push ( ...items )
+///
+/// The arguments are appended to the end of the array, in the order in which
+/// they appear. The new length of the array is returned as the result of the
+/// call.
+/// https://tc39.es/ecma262/#sec-array.prototype.push
+pub fn push(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
+    let new_array = add_to_array_object(this, args)?;
+    Ok(new_array.get_field_slice("length"))
+}
+
+/// Array.prototype.pop ( )
+///
+/// The last element of the array is removed from the array and returned.
+/// https://tc39.es/ecma262/#sec-array.prototype.pop
+pub fn pop(this: Value, _: Value, _: Vec<Value>) -> ResultValue {
+    let curr_length: i32 = from_value(this.get_field_slice("length")).unwrap();
+    if curr_length < 1 {
+        return Err(to_value(
+            "Cannot pop() on an array with zero length".to_string(),
+        ));
+    }
+    let pop_index = curr_length - 1;
+    let pop_value: Value = this.get_field(pop_index.to_string());
+    this.remove_prop(&pop_index.to_string());
+    this.set_field_slice("length", to_value(pop_index));
+    Ok(pop_value)
+}
+
+/// Array.prototype.join ( separator )
+///
+/// The elements of the array are converted to Strings, and these Strings are
+/// then concatenated, separated by occurrences of the separator. If no
+/// separator is provided, a single comma is used as the separator.
+/// https://tc39.es/ecma262/#sec-array.prototype.join
+pub fn join(this: Value, _: Value, args: Vec<Value>) -> ResultValue {
+    let separator: String;
+
+    if args.len() > 0 {
+        separator = args[0].to_string();
+    } else {
+        separator = ",".to_string();
+    }
+
+    let mut elem_strs: Vec<String> = Vec::new();
+    let length: i32 = from_value(this.get_field_slice("length")).unwrap();
+    for n in 0..length {
+        let elem_str: String = this.get_field(n.to_string()).to_string();
+        elem_strs.push(elem_str);
+    }
+
+    Ok(to_value(elem_strs.join(&separator)))
+}
+
 /// Create a new `Array` object
 pub fn _create(global: &Value) -> Value {
     let array = to_value(make_array as NativeFunctionData);
@@ -47,6 +159,14 @@ pub fn _create(global: &Value) -> Value {
         set: Gc::new(ValueData::Undefined),
     };
     proto.set_prop_slice("length", length);
+    let concat_func = to_value(concat as NativeFunctionData);
+    concat_func.set_field_slice("length", to_value(1 as i32));
+    proto.set_field_slice("concat", concat_func);
+    let push_func = to_value(push as NativeFunctionData);
+    push_func.set_field_slice("length", to_value(1 as i32));
+    proto.set_field_slice("push", push_func);
+    proto.set_field_slice("pop", to_value(pop as NativeFunctionData));
+    proto.set_field_slice("join", to_value(join as NativeFunctionData));
     array.set_field_slice(PROTOTYPE, proto);
     array
 }