From 43c9afcae624aaa118c112647a20f17e0c7e5b12 Mon Sep 17 00:00:00 2001
From: Haled Odat <8566042+HalidOdat@users.noreply.github.com>
Date: Sat, 4 Nov 2023 12:31:56 +0100
Subject: [PATCH] Add `$boa.string` module

---
 boa_cli/src/debug/mod.rs     |  7 ++++
 boa_cli/src/debug/string.rs  | 77 ++++++++++++++++++++++++++++++++++++
 boa_engine/src/string/mod.rs |  4 ++
 docs/boa_object.md           | 31 +++++++++++++++
 4 files changed, 119 insertions(+)
 create mode 100644 boa_cli/src/debug/string.rs

diff --git a/boa_cli/src/debug/mod.rs b/boa_cli/src/debug/mod.rs
index 72a24a2d15..c02b24e1e8 100644
--- a/boa_cli/src/debug/mod.rs
+++ b/boa_cli/src/debug/mod.rs
@@ -10,6 +10,7 @@ mod object;
 mod optimizer;
 mod realm;
 mod shape;
+mod string;
 
 fn create_boa_object(context: &mut Context<'_>) -> JsObject {
     let function_module = function::create_object(context);
@@ -19,6 +20,7 @@ fn create_boa_object(context: &mut Context<'_>) -> JsObject {
     let gc_module = gc::create_object(context);
     let realm_module = realm::create_object(context);
     let limits_module = limits::create_object(context);
+    let string_module = string::create_string(context);
 
     ObjectInitializer::new(context)
         .property(
@@ -56,6 +58,11 @@ fn create_boa_object(context: &mut Context<'_>) -> JsObject {
             limits_module,
             Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE,
         )
+        .property(
+            "string",
+            string_module,
+            Attribute::WRITABLE | Attribute::NON_ENUMERABLE | Attribute::CONFIGURABLE,
+        )
         .build()
 }
 
diff --git a/boa_cli/src/debug/string.rs b/boa_cli/src/debug/string.rs
new file mode 100644
index 0000000000..5b61ba6b8d
--- /dev/null
+++ b/boa_cli/src/debug/string.rs
@@ -0,0 +1,77 @@
+use boa_engine::{
+    js_string, object::ObjectInitializer, property::Attribute, string::JsStrVariant, Context,
+    JsNativeError, JsObject, JsResult, JsValue, NativeFunction,
+};
+
+fn storage(_: &JsValue, args: &[JsValue], _: &mut Context<'_>) -> JsResult<JsValue> {
+    let Some(value) = args.get(0) else {
+        return Err(JsNativeError::typ()
+            .with_message("expected string argument")
+            .into());
+    };
+
+    let Some(string) = value.as_string() else {
+        return Err(JsNativeError::typ()
+            .with_message(format!("expected string, got {}", value.type_of()))
+            .into());
+    };
+
+    let storage = if string.is_static() { "static" } else { "heap" };
+    Ok(js_string!(storage).into())
+}
+
+fn encoding(_: &JsValue, args: &[JsValue], _: &mut Context<'_>) -> JsResult<JsValue> {
+    let Some(value) = args.get(0) else {
+        return Err(JsNativeError::typ()
+            .with_message("expected string argument")
+            .into());
+    };
+
+    let Some(string) = value.as_string() else {
+        return Err(JsNativeError::typ()
+            .with_message(format!("expected string, got {}", value.type_of()))
+            .into());
+    };
+
+    let str = string.as_str();
+    let encoding = match str.variant() {
+        JsStrVariant::Ascii(_) => "ascii",
+        JsStrVariant::U16(_) => "U16",
+    };
+    Ok(js_string!(encoding).into())
+}
+
+fn summary(_: &JsValue, args: &[JsValue], context: &mut Context<'_>) -> JsResult<JsValue> {
+    let Some(value) = args.get(0) else {
+        return Err(JsNativeError::typ()
+            .with_message("expected string argument")
+            .into());
+    };
+
+    let Some(string) = value.as_string() else {
+        return Err(JsNativeError::typ()
+            .with_message(format!("expected string, got {}", value.type_of()))
+            .into());
+    };
+
+    let storage = if string.is_static() { "static" } else { "heap" };
+    let encoding = match string.as_str().variant() {
+        JsStrVariant::Ascii(_) => "ascii",
+        JsStrVariant::U16(_) => "U16",
+    };
+
+    let summary = ObjectInitializer::new(context)
+        .property("storage", js_string!(storage), Attribute::all())
+        .property("encoding", js_string!(encoding), Attribute::all())
+        .build();
+
+    Ok(summary.into())
+}
+
+pub(super) fn create_string(context: &mut Context<'_>) -> JsObject {
+    ObjectInitializer::new(context)
+        .function(NativeFunction::from_fn_ptr(storage), "storage", 1)
+        .function(NativeFunction::from_fn_ptr(encoding), "encoding", 1)
+        .function(NativeFunction::from_fn_ptr(summary), "summary", 1)
+        .build()
+}
diff --git a/boa_engine/src/string/mod.rs b/boa_engine/src/string/mod.rs
index d45510d27b..e621642710 100644
--- a/boa_engine/src/string/mod.rs
+++ b/boa_engine/src/string/mod.rs
@@ -920,6 +920,10 @@ impl JsString {
     pub(crate) fn trim_end(&self) -> JsStr<'_> {
         self.as_str().trim_end()
     }
+
+    pub fn is_static(&self) -> bool {
+        self.ptr.is_tagged()
+    }
 }
 
 impl Clone for JsString {
diff --git a/docs/boa_object.md b/docs/boa_object.md
index 64bc38a687..2c44197975 100644
--- a/docs/boa_object.md
+++ b/docs/boa_object.md
@@ -286,3 +286,34 @@ function x() {
 }
 x(); // RuntimeLimit: Maximum recursion limit 100 exceeded
 ```
+
+## Module `$boa.string`
+
+This module contains helpful functions for getting information about a strings.
+
+### Function `$boa.string.storage(str)`
+
+Returns the string's inner storage type, if it's a well known string that is stored in the `STATIC_STRINGS` array in boa,
+then `"static"` is returned, `"heap"` otherwise.
+
+```JavaScript
+$boa.string.storage("push")             // "static"
+$boa.string.storage("specialFunction")  // "heap"
+```
+
+### Function `$boa.string.encoding(str)`
+
+Returns the string's inner encoding of the string.
+
+```JavaScript
+$boa.string.encoding("Greeting") // "ascii"
+$boa.string.encoding("挨拶")      // "U16"
+```
+
+### Function `$boa.string.summary(str)`
+
+Returns an object with a short summary of the of the given string.
+
+```JavaScript
+$boa.string.summary("Greeting") // { storage: "heap", encoding: "ascii" }
+```