/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use indexmap::{IndexMap, IndexSet};

use anyhow::{bail, Result};
use askama::Template;
use uniffi_bindgen::to_askama_error;
use uniffi_pipeline::Node;

use crate::{ConcurrencyMode, Config};

/// Initial IR, this stores the metadata and other data
#[derive(Debug, Clone, Node)]
pub struct Root {
    /// In library mode, we get the name of the library file for free.
    pub cdylib: Option<String>,
    pub namespaces: IndexMap<String, Namespace>,
    pub cpp_scaffolding: CppScaffolding,
    pub module_docs: Vec<ApiModuleDocs>,
}

#[derive(Debug, Clone, Node, Template)]
#[template(path = "cpp/UniFFIScaffolding.cpp", escape = "none")]
pub struct CppScaffolding {
    pub ffi_definitions: CombinedItems<FfiDefinition>,
    pub scaffolding_calls: CombinedItems<ScaffoldingCall>,
    pub pointer_types: CombinedItems<PointerType>,
    pub callback_return_handler_classes: CombinedItems<CallbackReturnHandlerClass>,
    pub callback_interfaces: CombinedItems<CppCallbackInterface>,
}

// A Scaffolding call implemented in the C++ code
#[derive(Debug, Clone, Node)]
pub struct ScaffoldingCall {
    pub id: u64,
    pub ffi_func: FfiFunction,
    pub handler_class_name: String,
    pub arguments: Vec<FfiValueArgument>,
    pub return_ty: Option<FfiValueReturnType>,
}

/// FFI argument that's handled by one of the `FfiValue*` classes in the C++ code
#[derive(Debug, Clone, Node)]
pub struct FfiValueArgument {
    pub name: String,
    /// C++ class field name
    pub field_name: String,
    /// C++ function variable name
    pub var_name: String,
    pub ffi_value_class: String,
    /// Is this argument for a method receiver?
    pub receiver: bool,
    pub ty: FfiTypeNode,
}

/// FFI return value that's handled by one of the `FfiValue*` classes in the C++ code
#[derive(Debug, Clone, Node)]
pub struct FfiValueReturnType {
    pub ffi_value_class: String,
    pub ty: FfiTypeNode,
}

// A `PointerType` const to define in the C++ code
#[derive(Debug, Clone, Node)]
pub struct PointerType {
    pub id: u64,
    pub name: String,
    pub label: String,
    pub ffi_value_class: String,
    pub ffi_func_clone: RustFfiFunctionName,
    pub ffi_func_free: RustFfiFunctionName,
    pub trait_interface_info: Option<PointerTypeTraitInterfaceInfo>,
}

#[derive(Debug, Clone, Node)]
pub struct PointerTypeTraitInterfaceInfo {
    pub free_fn: String,
    pub clone_fn: String,
}

// Used to generate the C++ callback interface code
#[derive(Debug, Clone, Node)]
pub struct CppCallbackInterface {
    pub id: u64,
    pub name: String,
    /// C++ class that handles:
    ///   - Lowering the JS value, storing it, then passing the value to Rust
    ///   - Storing values from Rust, then lifting them to JS
    ///   - Cleaning up the stored value when we fail to lower/lift other values.
    ///
    /// This is only generated for regular callback interfaces.  For trait interfaces, the FfiValue
    /// class is defined in `PointerType.cpp`
    pub ffi_value_class: Option<String>,
    /// Name of the C++ variable that stores the UniFFICallbackHandler instance
    pub handler_var: String,
    // Name of the C++ static variable for the VTable
    pub vtable_var: String,
    /// Rust scaffolding function to initialize the VTable
    pub init_fn: RustFfiFunctionName,
    /// Name of the function generated by uniffi-bindgen-gecko-js to free a callback interface
    /// handle.
    pub free_fn: String,
    /// Name of the function generated by uniffi-bindgen-gecko-js to clone a callback interface
    /// handle.
    pub clone_fn: String,
    pub vtable_struct_type: FfiTypeNode,
    pub methods: Vec<CppCallbackInterfaceMethod>,
}

// Used to generate the C++ code to handle a callback method
#[derive(Debug, Clone, Node)]
pub struct CppCallbackInterfaceMethod {
    /// Name of the handler function
    pub fn_name: String,
    pub kind: CallbackMethodKind,
    pub return_handler_class_name: String,
    /// Name of the subclass
    pub async_handler_class_name: String,
    pub ffi_func: FfiFunctionType,
    pub arguments: Vec<FfiValueArgument>,
    pub return_ty: Option<FfiValueReturnType>,
    pub out_pointer_ty: FfiTypeNode,
}

/// Callback method kind.
///
/// There's currently only 2 options:
///   - Methods that are async in both Rust and JS
///   - Sync Rust methods wrapped to be fire-and-forget JS methods
#[derive(Debug, Clone, Node)]
pub enum CallbackMethodKind {
    Sync,
    FireAndForget,
    Async(CppCallbackInterfaceMethodAsyncData),
}

#[derive(Debug, Clone, Node)]
pub struct CppCallbackInterfaceMethodAsyncData {
    pub complete_callback_type_name: String,
    pub result_type_name: String,
}

#[derive(Debug, Clone, Node)]
pub struct CallbackReturnHandlerClass {
    pub name: String,
    pub return_ty: Option<FfiValueReturnType>,
    pub return_type_name: String,
}

/// Base class for an async callback method handler
///
/// This derives from `AsyncCallbackMethodHandlerBase` and adds support for returning data to
/// Rust.  The final callback method handler derives from this and adds support for argument
/// handling.
///
/// Splitting the classes this way reduces memory usage.  We only need to create one of these base
/// classes for each return type rather than one per method.
#[derive(Debug, Clone, Node)]
pub struct AsyncCallbackMethodHandlerBase {
    pub class_name: String,
    pub complete_callback_type_name: String,
    pub result_type_name: String,
    pub return_type: Option<FfiValueReturnType>,
}

#[derive(Debug, Clone, Node, Template)]
#[template(path = "js/Module.sys.mjs", escape = "none")]
pub struct Namespace {
    pub name: String,
    pub config: Config,
    pub js_name: String,
    pub js_filename: String,
    pub fixture: bool,
    pub crate_name: String,
    pub docstring: Option<String>,
    pub js_docstring: String,
    pub functions: Vec<Function>,
    pub type_definitions: Vec<TypeDefinition>,
    pub ffi_definitions: IndexSet<FfiDefinition>,
    pub checksums: Vec<Checksum>,
    pub ffi_rustbuffer_alloc: RustFfiFunctionName,
    pub ffi_rustbuffer_from_bytes: RustFfiFunctionName,
    pub ffi_rustbuffer_free: RustFfiFunctionName,
    pub ffi_rustbuffer_reserve: RustFfiFunctionName,
    pub ffi_uniffi_contract_version: RustFfiFunctionName,
    pub string_type_node: TypeNode,
    pub has_callback_interface: bool,
    pub imports: Vec<String>,
}

#[derive(Debug, Clone, Node)]
pub enum TypeDefinition {
    Interface(Interface),
    CallbackInterface(CallbackInterface),
    Record(Record),
    Enum(Enum),
    Custom(CustomType),
    Simple(TypeNode),
    Optional(OptionalType),
    Sequence(SequenceType),
    Map(MapType),
    External(ExternalType),
}

#[derive(Debug, Clone, Node)]
pub struct NamespaceMetadata {
    pub crate_name: String,
    pub name: String,
}

#[derive(Debug, Clone, Node)]
pub struct Function {
    pub name: String,
    pub callable: Callable,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

#[derive(Debug, Clone, Node)]
pub struct Constructor {
    pub name: String,
    pub self_name: String,
    pub callable: Callable,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

#[derive(Debug, Clone, Node)]
pub struct Method {
    pub name: String,
    pub self_name: String,
    pub callable: Callable,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

/// Common data from Function/Method/Constructor
#[derive(Debug, Clone, Node)]
pub struct Callable {
    pub name: String,
    pub async_data: Option<AsyncData>,
    pub is_js_async: bool,
    pub concurrency_mode: ConcurrencyMode,
    // UniFFIScaffolding method used to invoke this callable
    pub uniffi_scaffolding_method: String,
    pub kind: CallableKind,
    pub arguments: Vec<Argument>,
    pub return_type: ReturnType,
    pub throws_type: ThrowsType,
    pub checksum: Option<u16>,
    pub ffi_func: RustFfiFunctionName,
    pub id: u64,
}

#[derive(Debug, Clone, Node)]
pub enum CallableKind {
    Function,
    Method {
        self_type: TypeNode,
        ffi_converter: String,
    },
    Constructor {
        self_type: TypeNode,
        primary: bool,
    },
    VTableMethod {
        self_type: TypeNode,
        for_callback_interface: bool,
    },
}

#[derive(Debug, Clone, Node)]
pub struct ReturnType {
    pub ty: Option<TypeNode>,
}

#[derive(Debug, Clone, Node)]
pub struct ThrowsType {
    pub ty: Option<TypeNode>,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct AsyncData {
    pub ffi_rust_future_poll: RustFfiFunctionName,
    pub ffi_rust_future_cancel: RustFfiFunctionName,
    pub ffi_rust_future_free: RustFfiFunctionName,
    pub ffi_rust_future_complete: RustFfiFunctionName,
    pub ffi_foreign_future_complete: FfiFunctionTypeName,
    pub ffi_foreign_future_result: FfiStructName,
}

#[derive(Debug, Clone, Node)]
pub struct Argument {
    pub name: String,
    pub ty: TypeNode,
    pub by_ref: bool,
    pub optional: bool,
    pub default: Option<DefaultValueNode>,
}

#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub enum DefaultValue {
    Default(TypeNode),
    Literal(LiteralNode),
}

#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub struct DefaultValueNode {
    #[node(wraps)]
    pub default: DefaultValue,
    /// The default value rendered as a string
    pub js_lit: String,
}

#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub struct LiteralNode {
    pub js_lit: String,
    pub lit: Literal,
}

#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub enum Literal {
    Boolean(bool),
    String(String),
    // Integers are represented as the widest representation we can.
    // Number formatting vary with language and radix, so we avoid a lot of parsing and
    // formatting duplication by using only signed and unsigned variants.
    UInt(u64, Radix, TypeNode),
    Int(i64, Radix, TypeNode),
    // Pass the string representation through as typed in the UDL.
    // This avoids a lot of uncertainty around precision and accuracy,
    // though bindings for languages less sophisticated number parsing than WebIDL
    // will have to do extra work.
    Float(String, TypeNode),
    Enum(String, TypeNode),
    EmptySequence,
    EmptyMap,
    None,
    Some { inner: Box<Literal> },
}

// Represent the radix of integer literal values.
// We preserve the radix into the generated bindings for readability reasons.
#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub enum Radix {
    Decimal = 10,
    Octal = 8,
    Hexadecimal = 16,
}

#[derive(Debug, Clone, Node)]
pub struct Record {
    pub name: String,
    pub remote: bool, // only used when generating scaffolding from UDL
    pub fields: Vec<Field>,
    pub docstring: Option<String>,
    pub js_docstring: String,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node)]
pub struct Field {
    pub name: String,
    pub ty: TypeNode,
    pub default: Option<DefaultValueNode>,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

#[derive(Debug, Clone, Node)]
pub enum EnumShape {
    Enum,
    Error { flat: bool },
}

#[derive(Debug, Clone, Node)]
pub struct Enum {
    pub name: String,
    pub is_flat: bool,
    pub shape: EnumShape,
    pub remote: bool,
    pub variants: Vec<Variant>,
    pub discr_type: TypeNode,
    pub non_exhaustive: bool,
    pub js_docstring: String,
    pub docstring: Option<String>,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node)]
pub struct Variant {
    pub name: String,
    pub discr: LiteralNode,
    pub fields: Vec<Field>,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

#[derive(Debug, Clone, Node)]
pub struct Interface {
    pub name: String,
    pub js_class_name: String,
    pub object_id: u64,
    pub interface_base_class: InterfaceBaseClass,
    pub constructors: Vec<Constructor>,
    pub methods: Vec<Method>,
    pub uniffi_traits: Vec<UniffiTrait>,
    pub trait_impls: Vec<ObjectTraitImpl>,
    pub remote: bool, // only used when generating scaffolding from UDL
    pub imp: ObjectImpl,
    pub docstring: Option<String>,
    pub js_docstring: String,
    pub self_type: TypeNode,
    pub vtable: Option<VTable>,
    pub ffi_func_clone: RustFfiFunctionName,
    pub ffi_func_free: RustFfiFunctionName,
}

#[derive(Debug, Clone, Node)]
pub struct CallbackInterface {
    pub name: String,
    pub interface_base_class: InterfaceBaseClass,
    pub vtable: VTable,
    pub docstring: Option<String>,
    pub js_docstring: String,
    pub self_type: TypeNode,
}

/// Javascript interface class.
///
/// This is an abstract base class that the interface implements.
/// For trait/callback interfaces this is what the JS code should extend.
#[derive(Debug, Clone, Node)]
pub struct InterfaceBaseClass {
    pub name: String,
    pub methods: Vec<Method>,
    pub docstring: Option<String>,
    pub js_docstring: String,
}

#[derive(Debug, Clone, Node)]
pub struct VTable {
    /// Name of the interface this VTable is for
    pub interface_name: String,
    /// Was this generated for a CallbackInterface?
    pub callback_interface: bool,
    pub callback_interface_id: u64,
    /// Name of the JS variable that stores the UniFFICallbackHandler instance
    pub js_handler_var: String,
    pub struct_type: FfiTypeNode,
    pub init_fn: RustFfiFunctionName,
    pub methods: Vec<VTableMethod>,
}

/// Single method in a vtable
#[derive(Debug, Clone, Node)]
pub struct VTableMethod {
    pub callable: Callable,
    pub ffi_type: FfiTypeNode,
}

#[derive(Debug, Clone, Node)]
pub enum UniffiTrait {
    Debug { fmt: Method },
    Display { fmt: Method },
    Eq { eq: Method, ne: Box<Method> },
    Hash { hash: Method },
}

#[derive(Debug, Clone, Node)]
pub struct ObjectTraitImpl {
    pub ty: TypeNode,
    pub trait_name: String,
    pub tr_module_name: Option<String>,
}

#[derive(Debug, Clone, Node)]
pub struct CustomType {
    pub name: String,
    pub builtin: TypeNode,
    pub docstring: Option<String>,
    pub js_docstring: String,
    pub self_type: TypeNode,
    pub type_name: Option<String>,
    pub lift_expr: Option<String>,
    pub lower_expr: Option<String>,
}

#[derive(Debug, Clone, Node)]
pub struct OptionalType {
    pub inner: TypeNode,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node)]
pub struct SequenceType {
    pub inner: TypeNode,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node)]
pub struct MapType {
    pub key: TypeNode,
    pub value: TypeNode,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node)]
pub struct ExternalType {
    pub namespace: String,
    pub name: String,
    pub self_type: TypeNode,
}

#[derive(Debug, Clone, Node, Eq, PartialEq, Hash)]
pub struct TypeNode {
    pub ty: Type,
    /// Name of the JS class for this type (only set for user-defined types like
    /// enums/records/interfaces).
    pub class_name: Option<String>,
    pub jsdoc_name: String,
    pub canonical_name: String,
    pub ffi_converter: String,
    pub is_used_as_error: bool,
    pub ffi_type: FfiTypeNode,
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, Node)]
pub enum Type {
    // Primitive types.
    UInt8,
    Int8,
    UInt16,
    Int16,
    UInt32,
    Int32,
    UInt64,
    Int64,
    Float32,
    Float64,
    Boolean,
    String,
    Bytes,
    Timestamp,
    Duration,
    Interface {
        // The module path to the object
        module_name: String,
        // The name in the "type universe"
        name: String,
        // How the object is implemented.
        imp: ObjectImpl,
    },
    // Types defined in the component API, each of which has a string name.
    Record {
        module_name: String,
        name: String,
    },
    Enum {
        module_name: String,
        name: String,
    },
    CallbackInterface {
        module_name: String,
        name: String,
    },
    // Structurally recursive types.
    Optional {
        inner_type: Box<Type>,
    },
    Sequence {
        inner_type: Box<Type>,
    },
    Map {
        key_type: Box<Type>,
        value_type: Box<Type>,
    },
    // Custom type on the scaffolding side
    Custom {
        module_name: String,
        name: String,
        builtin: Box<Type>,
    },
}

impl Type {
    pub fn name(&self) -> Result<&str> {
        match &self {
            Type::Record { name, .. }
            | Type::Enum { name, .. }
            | Type::Interface { name, .. }
            | Type::CallbackInterface { name, .. }
            | Type::Custom { name, .. } => Ok(name.as_str()),
            _ => bail!("This type has no name"),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, Node)]
pub enum ObjectImpl {
    // A single Rust type
    Struct,
    // A trait that's can be implemented by Rust types
    Trait,
    // A trait + a callback interface -- can be implemented by both Rust and foreign types.
    CallbackTrait,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub enum FfiDefinition {
    /// FFI Function exported in the Rust library
    RustFunction(FfiFunction),
    /// FFI Function definition used in the interface, language, for example a callback interface method.
    FunctionType(FfiFunctionType),
    /// Struct definition used in the interface, for example a callback interface Vtable.
    Struct(FfiStruct),
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct RustFfiFunctionName(pub String);

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiStructName(pub String);

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiFunctionTypeName(pub String);

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiFunction {
    pub name: RustFfiFunctionName,
    pub async_data: Option<AsyncData>,
    pub arguments: Vec<FfiArgument>,
    pub return_type: FfiReturnType,
    pub has_rust_call_status_arg: bool,
    pub kind: FfiFunctionKind,
}

#[derive(Debug, Clone, PartialEq, Eq, Node, Hash)]
pub enum FfiFunctionKind {
    Scaffolding,
    ObjectClone,
    ObjectFree,
    RustFuturePoll,
    RustFutureComplete,
    RustFutureCancel,
    RustFutureFree,
    RustBufferFromBytes,
    RustBufferFree,
    RustBufferAlloc,
    RustBufferReserve,
    RustVtableInit,
    UniffiContractVersion,
    Checksum,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiFunctionType {
    pub name: FfiFunctionTypeName,
    pub arguments: Vec<FfiArgument>,
    pub return_type: FfiReturnType,
    pub has_rust_call_status_arg: bool,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiReturnType {
    pub ty: Option<FfiTypeNode>,
    pub type_name: String,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiStruct {
    pub name: FfiStructName,
    pub fields: Vec<FfiField>,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiField {
    pub name: String,
    pub ty: FfiTypeNode,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiArgument {
    pub name: String,
    pub ty: FfiTypeNode,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub struct FfiTypeNode {
    pub ty: FfiType,
    pub type_name: String,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub enum FfiType {
    UInt8,
    Int8,
    UInt16,
    Int16,
    UInt32,
    Int32,
    UInt64,
    Int64,
    Float32,
    Float64,
    RustBuffer(Option<String>),
    ForeignBytes,
    Function(FfiFunctionTypeName),
    Struct(FfiStructName),
    Handle(HandleKind),
    RustCallStatus,
    Reference(Box<FfiType>),
    MutReference(Box<FfiType>),
    VoidPointer,
}

#[derive(Debug, Clone, Node, PartialEq, Eq, Hash)]
pub enum HandleKind {
    RustFuture,
    ForeignFuture,
    ForeignFutureCallbackData,
    StructInterface {
        namespace: String,
        interface_name: String,
    },
    TraitInterface {
        namespace: String,
        interface_name: String,
    },
}

#[derive(Debug, Clone, Node)]
pub struct Checksum {
    pub fn_name: RustFfiFunctionName,
    pub checksum: u16,
}

#[derive(Debug, Clone, Node, Template)]
#[template(path = "api-doc.md", escape = "none")]
pub struct ApiModuleDocs {
    pub filename: String,
    pub jsdoc_module_name: String,
    pub module_name: String,
    pub classes: Vec<String>,
    pub functions: Vec<String>,
}

/// Combines fixture and non-fixture template items
#[derive(Debug, Clone, Node)]
pub struct CombinedItems<T> {
    pub items: Vec<T>,
    pub fixture_items: Vec<T>,
}

impl<T> CombinedItems<T> {
    /// Create a new CombinedItems value
    ///
    /// F is a function that finds items in module and pushes them to a vec.
    pub fn new<F>(root: &mut Root, mut f: F) -> Self
    where
        F: FnMut(&mut Namespace, &mut CombinedItemsIdGenerator, &mut Vec<T>),
    {
        Self::try_new(root, |namespace, id_generator, items| {
            f(namespace, id_generator, items);
            Ok(())
        })
        .unwrap()
    }

    pub fn try_new<F>(root: &mut Root, mut f: F) -> Result<Self>
    where
        F: FnMut(&mut Namespace, &mut CombinedItemsIdGenerator, &mut Vec<T>) -> Result<()>,
    {
        // Use 2 separate counters for "real" Rust components vs fixtures.
        let mut combined_items = Self {
            items: vec![],
            fixture_items: vec![],
        };
        let mut id_generator = CombinedItemsIdGenerator::default();
        // Process non-fixture items first for a couple reasons:
        // * It works better when a pass wants to de-dupe items, like we do for FFI definitions,
        //   and an item appears in both `items` and `fixture_items`.  This way the de-duped item
        //   won't be disabled by the if guard and also it will appear on top of the item list,
        //   which avoids issues with dependent definitions.
        // * It means the IDs get grouped together, which can make for a more efficient `switch`
        //   statement.

        root.try_visit_mut(|namespace: &mut Namespace| {
            if !namespace.fixture {
                f(namespace, &mut id_generator, &mut combined_items.items)
            } else {
                Ok(())
            }
        })?;
        root.try_visit_mut(|namespace: &mut Namespace| {
            if namespace.fixture {
                f(
                    namespace,
                    &mut id_generator,
                    &mut combined_items.fixture_items,
                )
            } else {
                Ok(())
            }
        })?;
        Ok(combined_items)
    }

    pub fn sort_by_key<F, K>(&mut self, f: F)
    where
        F: Fn(&T) -> K,
        K: Ord,
    {
        self.items.sort_by_key(&f);
        self.fixture_items.sort_by_key(&f);
    }

    /// Iterate over child items
    /// Each item is the tuple (preprocssor_condition, <T>, preprocssor_condition_end), where
    /// `preprocssor_condition` is the preprocessor preprocssor_condition that should control if
    /// the items are included.
    fn iter(&self) -> impl Iterator<Item = (String, &[T], String)> {
        vec![
            ("".to_string(), &*self.items, "".to_string()),
            (
                "#ifdef MOZ_UNIFFI_FIXTURES".to_string(),
                &*self.fixture_items,
                "#endif /* MOZ_UNIFFI_FIXTURES */".to_string(),
            ),
        ]
        .into_iter()
    }

    /// Create a new CombinedItems value by mapping the items and fixture_items lists to new lists.
    pub fn map<F, U>(&self, mut f: F) -> CombinedItems<U>
    where
        F: FnMut(&Vec<T>) -> Vec<U>,
    {
        CombinedItems {
            items: f(&self.items),
            fixture_items: f(&self.fixture_items),
        }
    }

    pub fn try_map<F, U>(&self, mut f: F) -> Result<CombinedItems<U>>
    where
        F: FnMut(&Vec<T>) -> Result<Vec<U>>,
    {
        Ok(CombinedItems {
            items: f(&self.items)?,
            fixture_items: f(&self.fixture_items)?,
        })
    }
}

#[derive(Default)]
pub struct CombinedItemsIdGenerator {
    counter: u64,
}

impl CombinedItemsIdGenerator {
    pub fn new_id(&mut self) -> u64 {
        self.counter += 1;
        self.counter
    }
}

impl ScaffoldingCall {
    pub fn is_async(&self) -> bool {
        self.ffi_func.async_data.is_some()
    }
}

impl FfiFunction {
    pub fn arg_types(&self) -> Vec<&str> {
        self.arguments
            .iter()
            .map(|a| a.ty.type_name.as_str())
            .chain(self.has_rust_call_status_arg.then_some("RustCallStatus*"))
            .collect()
    }
}

impl FfiFunctionType {
    pub fn arg_types(&self) -> Vec<&str> {
        self.arguments
            .iter()
            .map(|a| a.ty.type_name.as_str())
            .chain(self.has_rust_call_status_arg.then_some("RustCallStatus*"))
            .collect()
    }
}

pub mod filters {
    use super::*;
    use askama::Result;

    pub fn class_name(ty: &TypeNode, _: &dyn askama::Values) -> Result<String> {
        match &ty.class_name {
            Some(class_name) => Ok(class_name.clone()),
            None => Err(to_askama_error(&format!(
                "Trying to get class name for {:?}",
                ty
            ))),
        }
    }

    // Render an expression to check if two instances of this type are equal
    pub fn field_equals(field: &Field, _: &dyn askama::Values, first_obj: &str, second_obj: &str) -> Result<String> {
        let name = &field.name;
        Ok(match &field.ty.ty {
            Type::Record { .. } => format!("{first_obj}.{name}.equals({second_obj}.{name})"),
            _ => format!("{first_obj}.{name} == {second_obj}.{name}"),
        })
    }

    // Remove the trailing comma from a block of text.
    //
    // This can make generating argument lists more convenient.
    pub fn remove_trailing_comma<T: std::fmt::Display>(text: T, _: &dyn askama::Values) -> Result<String> {
        let text = text.to_string();
        let Some(last_comma) = text.rfind(',') else {
            return Ok(text.to_string());
        };
        if !text[last_comma + 1..].chars().all(char::is_whitespace) {
            return Ok(text.to_string());
        }
        Ok(text[..last_comma].to_string())
    }
}