Feat: ftd.main-package variable and some refactor

WARN: the `ftd.main-package` does not work yet. It's stored in the
`global` map in js output and it's not getting resolved when used in an
ftd file. This should be key on `ftd` object itself.

- `ftd.main-package`: A string variable that stores the name of the
  packaeg. This is useful to determine if a package is mounted in
  another package or if it's running standalone.
- Refactor: Create `HostBuiltins` type and use it instead of Array of
  fixed sized type everywhere. This makes it easy to add new builtins

fastn-core/src/doc.rs

@@ -28,11 +28,11 @@ fn cached_parse(
 pub fn package_dependent_builtins(
     pkg: &fastn_core::Package,
     req_path: &str,
-) -> [(String, fastn_resolved::Definition); 1] {
-    [(
-        "ftd#app-path".to_string(),
+) -> ftd::interpreter::HostBuiltins {
+    [
         fastn_core::host_builtins::app_path(pkg, req_path),
-    )]
+        fastn_core::host_builtins::main_package(pkg),
+    ]
 }
 
 #[tracing::instrument(skip(lib))]

fastn-core/src/host_builtins.rs

@@ -22,7 +22,7 @@
 ///
 /// Visiting `/app/` in browser should render /app/test/
 #[inline]
-pub fn app_path(pkg: &fastn_core::Package, req_path: &str) -> fastn_resolved::Definition {
+pub fn app_path(pkg: &fastn_core::Package, req_path: &str) -> (String, fastn_resolved::Definition) {
     let prefix = pkg
         .apps
         .iter()
@@ -31,8 +31,9 @@ pub fn app_path(pkg: &fastn_core::Package, req_path: &str) -> fastn_resolved::De
         .unwrap_or_default();
     let prefix = prefix.trim_end_matches('/');
 
-    fastn_resolved::Definition::Function(fastn_resolved::Function {
-        name: "ftd#app-path".to_string(),
+    let name = "ftd#app-path".to_string();
+    let def = fastn_resolved::Definition::Function(fastn_resolved::Function {
+        name: name.clone(),
         return_kind: fastn_resolved::KindData {
             kind: fastn_resolved::Kind::string(),
             caption: false,
@@ -57,5 +58,33 @@ pub fn app_path(pkg: &fastn_core::Package, req_path: &str) -> fastn_resolved::De
         js: None,
         line_number: 0,
         external_implementation: false,
-    })
+    });
+
+    (name, def)
+}
+
+/// Ftd string variable that holds the name of the package.
+///
+/// Useful to determine if the package is run standalone or as a dependency:
+#[inline]
+pub fn main_package(pkg: &fastn_core::Package) -> (String, fastn_resolved::Definition) {
+    let name = "ftd#main-package".to_string();
+    let def = fastn_resolved::Definition::Variable(fastn_resolved::Variable {
+        name: name.clone(),
+        kind: fastn_resolved::Kind::string().into_kind_data(),
+        value: fastn_resolved::PropertyValue::Value {
+            value: fastn_resolved::Value::String {
+                text: pkg.name.clone(),
+            },
+            is_mutable: false,
+            line_number: 0,
+        },
+        conditional_value: vec![],
+        mutable: false,
+        is_static: false,
+        line_number: 0,
+    });
+
+
+    (name, def)
 }

ftd/src/interpreter/main.rs

@@ -6,6 +6,10 @@ use ftd::interpreter::things::web_component::WebComponentDefinitionExt;
 use ftd::interpreter::FunctionExt;
 use ftd::interpreter::{ComponentExt, VariableExt};
 
+
+/// Array with the size of how many builtins are provided by the host
+pub type HostBuiltins = [(String, fastn_resolved::Definition); 2];
+
 /// The `InterpreterState` struct is a representation of the state of an interpreter. It contains
 /// information about the interpreter's current state and its progress through the code being
 /// interpreted.
@@ -99,7 +103,7 @@ impl InterpreterState {
     #[tracing::instrument(skip(builtins))]
     fn new_with_expanded_builtins(
         id: String,
-        builtins: Option<[(String, fastn_resolved::Definition); 1]>,
+        builtins: Option<HostBuiltins>,
     ) -> InterpreterState {
         let mut bag = ftd::interpreter::default::builtins().clone();
 
@@ -978,7 +982,7 @@ pub fn interpret(id: &str, source: &str) -> ftd::interpreter::Result<Interpreter
 pub fn interpret_with_line_number(
     id: &str,
     document: ParsedDocument,
-    builtin_overrides: Option<[(String, fastn_resolved::Definition); 1]>,
+    builtin_overrides: Option<HostBuiltins>,
 ) -> ftd::interpreter::Result<Interpreter> {
     use itertools::Itertools;
 

ftd/src/interpreter/mod.rs

@@ -55,6 +55,8 @@ pub use things::value::{PropertyValueExt, PropertyValueSourceExt, ValueExt};
 pub use things::variable::VariableExt;
 pub use things::ThingExt;
 
+pub use main::HostBuiltins;
+
 #[derive(thiserror::Error, Debug)]
 pub enum Error {
     #[error("OtherError: {}", _0)]