llvm-native-core 0.1.12

//! C++ Run-Time Type Information (RTTI) — implements type_info emission,
//! type descriptor generation, and dynamic_cast support.
//!
//! Follows the Itanium C++ ABI for RTTI layout:
//! - type_info: basic type descriptor (vtable + name string)
//! - __class_type_info: type_info + nothing extra
//! - __si_class_type_info: single inheritance
//! - __vmi_class_type_info: multiple/virtual inheritance
//! - __pbase_type_info, __pointer_type_info, etc.
//!
//! Clean-room behavioral reconstruction from:
//! - Itanium C++ ABI (v1.86), §2.9 "RTTI"
//! - C++ Standard §18.7 (typeinfo)
//! - No LLVM/Clang source code is consulted.

use std::collections::HashMap;

use super::name_mangling::{MangledName, Mangler};

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Descriptor Kinds
// ═══════════════════════════════════════════════════════════════════════════════

/// The kind of RTTI descriptor.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RttiKind {
    /// Fundamental type (int, double, etc.)
    Fundamental,
    /// Pointer type
    Pointer,
    /// Pointer to member type
    PointerToMember,
    /// Array type
    Array,
    /// Function type
    Function,
    /// Enum type
    Enum,
    /// Class without bases
    Class,
    /// Class with single non-virtual base
    SiClass,
    /// Class with multiple or virtual bases
    VmiClass,
}

impl RttiKind {
    /// The name of the C++ RTTI class for this kind.
    pub fn class_name(&self) -> &'static str {
        match self {
            RttiKind::Fundamental => "type_info",
            RttiKind::Pointer => "__pointer_type_info",
            RttiKind::PointerToMember => "__pointer_to_member_type_info",
            RttiKind::Array => "__array_type_info",
            RttiKind::Function => "__function_type_info",
            RttiKind::Enum => "__enum_type_info",
            RttiKind::Class => "__class_type_info",
            RttiKind::SiClass => "__si_class_type_info",
            RttiKind::VmiClass => "__vmi_class_type_info",
        }
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Descriptor
// ═══════════════════════════════════════════════════════════════════════════════

/// A complete RTTI type descriptor.
#[derive(Debug, Clone)]
pub struct RttiDescriptor {
    /// The type name (demangled, e.g., "MyClass").
    pub type_name: String,
    /// The mangled typeinfo symbol (e.g., `_ZTI7MyClass`).
    pub typeinfo_symbol: MangledName,
    /// The mangled typeinfo name symbol (e.g., `_ZTS7MyClass`).
    pub typeinfo_name_symbol: MangledName,
    /// The RTTI kind.
    pub kind: RttiKind,
    /// The vtable pointer (points to the type_info vtable).
    pub vtable_ptr: String,
    /// The human-readable type name stored in the RTTI.
    pub name_string: String,
    /// For __si_class_type_info: the base class typeinfo.
    pub base_type: Option<Box<RttiDescriptor>>,
    /// For __vmi_class_type_info: base class info with flags/offsets.
    pub base_info: Vec<BaseClassTypeInfo>,
    /// For pointer types: the pointee typeinfo.
    pub pointee_type: Option<Box<RttiDescriptor>>,
}

/// Information about a base class in a vmi_class_type_info descriptor.
#[derive(Debug, Clone)]
pub struct BaseClassTypeInfo {
    /// The typeinfo of the base class.
    pub typeinfo: Box<RttiDescriptor>,
    /// Flags: bit 0 = is_virtual, bit 1 = is_public
    pub flags: u32,
    /// Offset of the base within the derived class.
    pub offset: i64,
}

impl RttiDescriptor {
    pub fn new(
        type_name: &str,
        typeinfo_symbol: MangledName,
        typeinfo_name_symbol: MangledName,
        kind: RttiKind,
    ) -> Self {
        Self {
            type_name: type_name.to_string(),
            typeinfo_symbol,
            typeinfo_name_symbol,
            kind,
            vtable_ptr: String::new(),
            name_string: type_name.to_string(),
            base_type: None,
            base_info: Vec::new(),
            pointee_type: None,
        }
    }

    /// Generate the LLVM IR for the typeinfo name string.
    pub fn emit_name_ir(&self) -> String {
        format!(
            "@{} = private unnamed_addr constant [{} x i8] c\"{}\\00\", align 1\n",
            self.typeinfo_name_symbol,
            self.name_string.len() + 1,
            self.name_string
        )
    }

    /// Generate the LLVM IR for the typeinfo descriptor.
    pub fn emit_typeinfo_ir(&self) -> String {
        let mut ir = String::new();

        match self.kind {
            RttiKind::Fundamental | RttiKind::Enum | RttiKind::Function => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr }} {{\n",
                    self.typeinfo_symbol
                ));
                ir.push_str(&format!("  ptr {}, ; vtable\n", self.vtable_ptr));
                ir.push_str(&format!("  ptr @{} ; name\n", self.typeinfo_name_symbol));
                ir.push_str("}, align 8\n");
            }
            RttiKind::Pointer => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, ptr }} {{\n",
                    self.typeinfo_symbol
                ));
                ir.push_str(&format!("  ptr {}, ; vtable\n", self.vtable_ptr));
                ir.push_str(&format!("  ptr @{}, ; name\n", self.typeinfo_name_symbol));
                if let Some(ref pointee) = self.pointee_type {
                    ir.push_str(&format!(
                        "  ptr @{} ; pointee typeinfo\n",
                        pointee.typeinfo_symbol
                    ));
                } else {
                    ir.push_str("  ptr null ; pointee typeinfo\n");
                }
                ir.push_str("}, align 8\n");
            }
            RttiKind::Class => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr }} {{\n",
                    self.typeinfo_symbol
                ));
                ir.push_str(&format!("  ptr {}, ; vtable\n", self.vtable_ptr));
                ir.push_str(&format!("  ptr @{} ; name\n", self.typeinfo_name_symbol));
                ir.push_str("}, align 8\n");
            }
            RttiKind::SiClass => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, ptr }} {{\n",
                    self.typeinfo_symbol
                ));
                ir.push_str(&format!("  ptr {}, ; vtable\n", self.vtable_ptr));
                ir.push_str(&format!("  ptr @{}, ; name\n", self.typeinfo_name_symbol));
                if let Some(ref base) = self.base_type {
                    ir.push_str(&format!(
                        "  ptr @{} ; base typeinfo\n",
                        base.typeinfo_symbol
                    ));
                } else {
                    ir.push_str("  ptr null ; base typeinfo\n");
                }
                ir.push_str("}, align 8\n");
            }
            RttiKind::VmiClass => {
                let base_count = self.base_info.len();
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, i32, i32, [{} x {{ ptr, i64 }}] }} {{\n",
                    self.typeinfo_symbol, base_count
                ));
                ir.push_str(&format!("  ptr {}, ; vtable\n", self.vtable_ptr));
                ir.push_str(&format!("  ptr @{}, ; name\n", self.typeinfo_name_symbol));
                ir.push_str(&format!("  i32 {}, ; flags\n", 0u32));
                ir.push_str(&format!("  i32 {}, ; base count\n", base_count));
                ir.push_str("  [");
                for (i, base) in self.base_info.iter().enumerate() {
                    if i > 0 {
                        ir.push_str(", ");
                    }
                    ir.push_str(&format!(
                        "{{ ptr @{}, i64 {} }}",
                        base.typeinfo.typeinfo_symbol, base.offset
                    ));
                }
                ir.push_str("]\n}, align 8\n");
            }
            _ => {}
        }

        ir
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Builder
// ═══════════════════════════════════════════════════════════════════════════════

/// Builds RTTI descriptors for types in a translation unit.
pub struct RttiBuilder {
    mangler: Mangler,
    descriptors: HashMap<String, RttiDescriptor>,
    /// The type_info vtable pointer (platform-specific, typically null or
    /// a reference to the C++ ABI library's vtable).
    typeinfo_vtable: String,
}

impl RttiBuilder {
    pub fn new() -> Self {
        Self {
            mangler: Mangler::new(),
            descriptors: HashMap::new(),
            typeinfo_vtable: "null".to_string(),
        }
    }

    /// Set the typeinfo vtable pointer symbol.
    pub fn set_typeinfo_vtable(&mut self, vtable: &str) {
        self.typeinfo_vtable = vtable.to_string();
    }

    /// Build an RTTI descriptor for a class type.
    pub fn build_class_rtti(
        &mut self,
        class_name: &str,
        bases: &[(String, bool, bool)], // (base_name, is_virtual, is_direct)
    ) -> &RttiDescriptor {
        let typeinfo_name = self.mangler.mangle_typeinfo_name(class_name);
        let typeinfo = self.mangler.mangle_typeinfo(class_name);

        let kind = if bases.is_empty() {
            RttiKind::Class
        } else if bases.len() == 1 && !bases[0].1 {
            RttiKind::SiClass
        } else {
            RttiKind::VmiClass
        };

        let mut desc = RttiDescriptor::new(class_name, typeinfo, typeinfo_name, kind);
        desc.vtable_ptr = self.typeinfo_vtable.clone();
        desc.name_string = class_name.to_string();

        match kind {
            RttiKind::SiClass => {
                // Build base typeinfo first
                let base_name = &bases[0].0;
                self.build_class_rtti(base_name, &[]);
                if let Some(base) = self.descriptors.get(base_name) {
                    desc.base_type = Some(Box::new(base.clone()));
                }
            }
            RttiKind::VmiClass => {
                for (base_name, is_virtual, _) in bases {
                    self.build_class_rtti(base_name, &[]);
                    if let Some(base) = self.descriptors.get(base_name) {
                        desc.base_info.push(BaseClassTypeInfo {
                            typeinfo: Box::new(base.clone()),
                            flags: if *is_virtual { 1u32 } else { 0u32 } | 2u32, // public
                            offset: 0,                                           // simplified
                        });
                    }
                }
            }
            _ => {}
        }

        self.descriptors
            .insert(class_name.to_string(), desc.clone());
        self.descriptors.get(class_name).unwrap()
    }

    /// Build an RTTI descriptor for a fundamental type.
    pub fn build_fundamental_rtti(&mut self, type_name: &str) -> &RttiDescriptor {
        let typeinfo_name = self.mangler.mangle_typeinfo_name(type_name);
        let typeinfo = self.mangler.mangle_typeinfo(type_name);

        let desc = RttiDescriptor::new(type_name, typeinfo, typeinfo_name, RttiKind::Fundamental);
        self.descriptors.insert(type_name.to_string(), desc.clone());
        self.descriptors.get(type_name).unwrap()
    }

    /// Build an RTTI descriptor for a pointer type.
    pub fn build_pointer_rtti(&mut self, pointee_name: &str) -> &RttiDescriptor {
        let pointer_name = format!("P{}", pointee_name);
        let typeinfo_name = self.mangler.mangle_typeinfo_name(&pointer_name);
        let typeinfo = self.mangler.mangle_typeinfo(&pointer_name);

        let mut desc =
            RttiDescriptor::new(&pointer_name, typeinfo, typeinfo_name, RttiKind::Pointer);
        desc.vtable_ptr = self.typeinfo_vtable.clone();

        // Build pointee typeinfo
        self.build_fundamental_rtti(pointee_name);
        if let Some(pointee) = self.descriptors.get(pointee_name) {
            desc.pointee_type = Some(Box::new(pointee.clone()));
        }

        let pointer_name_clone = pointer_name.clone();
        self.descriptors.insert(pointer_name, desc.clone());
        self.descriptors.get(&pointer_name_clone).unwrap()
    }

    /// Get a previously built descriptor.
    pub fn get_descriptor(&self, name: &str) -> Option<&RttiDescriptor> {
        self.descriptors.get(name)
    }

    /// Emit all RTTI data as LLVM IR.
    pub fn emit_all_ir(&self) -> String {
        let mut ir = String::new();
        ir.push_str("; RTTI Type Descriptors\n");

        // Emit name strings first
        for desc in self.descriptors.values() {
            ir.push_str(&desc.emit_name_ir());
        }
        ir.push('\n');

        // Emit typeinfo descriptors
        for desc in self.descriptors.values() {
            ir.push_str(&desc.emit_typeinfo_ir());
            ir.push('\n');
        }

        ir
    }

    /// Generate the dynamic_cast helper logic (LLVM IR).
    /// This is a simplified version — full dynamic_cast requires
    /// walking the class hierarchy at runtime.
    pub fn emit_dynamic_cast_helper(&self) -> String {
        r#"
; Dynamic cast helper — walks the class hierarchy.
; In a full implementation, this would be in libcxxabi.
define ptr @__dynamic_cast(ptr %obj, ptr %src_typeinfo, ptr %dst_typeinfo, i64 %hint) {
entry:
  ; Simplified: just check if types are equal
  %cmp = icmp eq ptr %src_typeinfo, %dst_typeinfo
  br i1 %cmp, label %success, label %walk_bases

walk_bases:
  ; Check __si_class_type_info base
  %si_vtable = getelementptr ptr, ptr %src_typeinfo, i32 0
  %si_base_ptr = getelementptr ptr, ptr %src_typeinfo, i32 2
  %si_base = load ptr, ptr %si_base_ptr
  %has_base = icmp ne ptr %si_base, null
  br i1 %has_base, label %recurse, label %fail

recurse:
  %result = call ptr @__dynamic_cast(ptr %obj, ptr %si_base, ptr %dst_typeinfo, i64 0)
  %found = icmp ne ptr %result, null
  br i1 %found, label %success, label %fail

success:
  ret ptr %obj

fail:
  ret ptr null
}
"#
        .to_string()
    }
}

impl Default for RttiBuilder {
    fn default() -> Self {
        Self::new()
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Constants
// ═══════════════════════════════════════════════════════════════════════════════

/// Well-known type_info vtable symbols.
pub mod typeinfo_vtables {
    /// Standard type_info vtable for Linux (provided by libstdc++).
    pub const GCC_LINUX_TYPEINFO_VTABLE: &str = "_ZTVN10__cxxabiv117__class_type_infoE";
    /// SI class type_info vtable.
    pub const GCC_LINUX_SI_CLASS_TYPEINFO_VTABLE: &str = "_ZTVN10__cxxabiv120__si_class_type_infoE";
    /// VMI class type_info vtable.
    pub const GCC_LINUX_VMI_CLASS_TYPEINFO_VTABLE: &str =
        "_ZTVN10__cxxabiv121__vmi_class_type_infoE";
    /// Pointer type_info vtable.
    pub const GCC_LINUX_POINTER_TYPEINFO_VTABLE: &str = "_ZTVN10__cxxabiv119__pointer_type_infoE";
}

// ═══════════════════════════════════════════════════════════════════════════════
// type_info Generation Per Class with Mangled Name
// ═══════════════════════════════════════════════════════════════════════════════

/// Generates the complete type_info for a class, including mangled name
/// and vtable pointer.
#[derive(Debug, Clone)]
pub struct TypeInfoGenerator {
    /// The class name (demangled).
    pub class_name: String,
    /// The mangled type_info symbol.
    pub typeinfo_sym: String,
    /// The mangled type_info name symbol.
    pub typeinfo_name_sym: String,
    /// The type_info vtable symbol to reference.
    pub vtable_sym: String,
}

impl TypeInfoGenerator {
    pub fn new(class_name: &str, mangler: &mut Mangler) -> Self {
        let typeinfo_name_sym = mangler.mangle_typeinfo_name(class_name).into_string();
        let typeinfo_sym = mangler.mangle_typeinfo(class_name).into_string();
        Self {
            class_name: class_name.to_string(),
            typeinfo_sym,
            typeinfo_name_sym,
            vtable_sym: String::new(),
        }
    }

    /// Set the type_info vtable pointer.
    pub fn with_vtable(mut self, vtable: &str) -> Self {
        self.vtable_sym = vtable.to_string();
        self
    }

    /// Emit the complete type_info object as LLVM IR.
    pub fn emit_complete_ir(&self, kind: RttiKind) -> String {
        let mut ir = String::new();

        // Emit the type_info name string in .rodata
        ir.push_str(&format!(
            "@{} = private unnamed_addr constant [{} x i8] c\"{}\\00\", align 1, section \".rodata\"\n",
            self.typeinfo_name_sym,
            self.class_name.len() + 1,
            self.class_name
        ));

        // Emit the type_info descriptor in .data.rel.ro
        let section = get_rtti_section(kind);
        match kind {
            RttiKind::Class | RttiKind::Fundamental | RttiKind::Enum => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr }} {{ ptr {}, ptr @{} }}, align 8, section \"{}\"\n",
                    self.typeinfo_sym,
                    self.vtable_sym,
                    self.typeinfo_name_sym,
                    section
                ));
            }
            RttiKind::SiClass => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, ptr }} {{ ptr {}, ptr @{}, ptr null }}, align 8, section \"{}\"\n",
                    self.typeinfo_sym,
                    self.vtable_sym,
                    self.typeinfo_name_sym,
                    section
                ));
            }
            RttiKind::VmiClass => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, i32, i32, [0 x {{ ptr, i64 }}] }} {{ ptr {}, ptr @{}, i32 0, i32 0, zeroinitializer }}, align 8, section \"{}\"\n",
                    self.typeinfo_sym,
                    self.vtable_sym,
                    self.typeinfo_name_sym,
                    section
                ));
            }
            RttiKind::Pointer => {
                ir.push_str(&format!(
                    "@{} = private constant {{ ptr, ptr, ptr }} {{ ptr {}, ptr @{}, ptr null }}, align 8, section \"{}\"\n",
                    self.typeinfo_sym,
                    self.vtable_sym,
                    self.typeinfo_name_sym,
                    section
                ));
            }
            _ => {}
        }

        ir
    }
}

/// Get the ELF section for a given RTTI kind.
fn get_rtti_section(kind: RttiKind) -> &'static str {
    match kind {
        RttiKind::Fundamental
        | RttiKind::Class
        | RttiKind::SiClass
        | RttiKind::VmiClass
        | RttiKind::Pointer
        | RttiKind::PointerToMember
        | RttiKind::Array
        | RttiKind::Function
        | RttiKind::Enum => ".data.rel.ro",
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// type_info Comparison Operator (before)
// ═══════════════════════════════════════════════════════════════════════════════

/// The `type_info::before()` comparison — orders type_info objects for use
/// in associative containers.
#[derive(Debug, Clone)]
pub struct TypeInfoOrdering {
    /// The first type_info symbol.
    pub lhs: String,
    /// The second type_info symbol.
    pub rhs: String,
    /// The comparison result.
    pub result: bool,
}

impl TypeInfoOrdering {
    pub fn new(lhs: &str, rhs: &str) -> Self {
        Self {
            lhs: lhs.to_string(),
            rhs: rhs.to_string(),
            result: false,
        }
    }

    /// Compare two type_info objects: returns `true` if `lhs` is before `rhs`.
    /// Per the Itanium ABI, the ordering is based on the mangled name string.
    pub fn compare(&mut self) -> bool {
        self.result = self.lhs < self.rhs;
        self.result
    }

    /// Generate the IR for `type_info::before(const type_info&) const`.
    pub fn gen_before_ir(&self) -> String {
        format!(
            r#"; type_info::before comparison
  %lhs.name.ptr = getelementptr inbounds {{ ptr, ptr }}, ptr %{}, i32 0, i32 1
  %lhs.name = load ptr, ptr %lhs.name.ptr
  %rhs.name.ptr = getelementptr inbounds {{ ptr, ptr }}, ptr %{}, i32 0, i32 1
  %rhs.name = load ptr, ptr %rhs.name.ptr
  %cmp = call i32 @strcmp(ptr %lhs.name, ptr %rhs.name)
  %result = icmp slt i32 %cmp, 0
  ret i1 %result
"#,
            self.lhs, self.rhs
        )
    }

    /// Generate the `operator==` comparison (simple pointer equality).
    pub fn gen_equals_ir(lhs: &str, rhs: &str) -> String {
        format!("  %eq = icmp eq ptr @{}, ptr @{}\n  ret i1 %eq\n", lhs, rhs)
    }

    /// Generate the `operator!=` comparison.
    pub fn gen_not_equals_ir(lhs: &str, rhs: &str) -> String {
        format!(
            "  %neq = icmp ne ptr @{}, ptr @{}\n  ret i1 %neq\n",
            lhs, rhs
        )
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// dynamic_cast Lowering
// ═══════════════════════════════════════════════════════════════════════════════

/// Lowering strategy for dynamic_cast operations.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DynCastStrategy {
    /// Same type — no conversion needed.
    Identity,
    /// Downcast — check type_info equality and adjust pointer.
    Downcast,
    /// Cross-cast — walk both hierarchies to find a common base.
    CrossCast,
    /// Cast to void* — return the most-derived object address.
    ToVoid,
}

/// Configuration for dynamic_cast lowering.
#[derive(Debug, Clone)]
pub struct DynCastLowering {
    /// The source type.
    pub source_type: String,
    /// The target type.
    pub target_type: String,
    /// The strategy to use.
    pub strategy: DynCastStrategy,
    /// Whether this is a reference cast (throws std::bad_cast on failure).
    pub is_ref_cast: bool,
    /// Class hierarchy depth for runtime walk.
    pub hierarchy_depth: usize,
}

impl DynCastLowering {
    pub fn new(source: &str, target: &str) -> Self {
        let strategy = if source == target {
            DynCastStrategy::Identity
        } else if target == "void" {
            DynCastStrategy::ToVoid
        } else {
            DynCastStrategy::Downcast
        };

        Self {
            source_type: source.to_string(),
            target_type: target.to_string(),
            strategy,
            is_ref_cast: false,
            hierarchy_depth: 0,
        }
    }

    /// Generate the IR for the dynamic_cast operation.
    pub fn gen_dynamic_cast_ir(&self, object: &str) -> String {
        match self.strategy {
            DynCastStrategy::Identity => {
                format!(
                    "  ; dynamic_cast: {} → {} (identity)\n  ret ptr {}\n",
                    self.source_type, self.target_type, object
                )
            }
            DynCastStrategy::ToVoid => {
                format!(
                    "  ; dynamic_cast: {} → void*\n  %vtable = load ptr, ptr {}\n  %offset = getelementptr inbounds i64, ptr %vtable, i64 -1\n  %offset.val = load i64, ptr %offset\n  %adj = getelementptr inbounds i8, ptr {}, i64 %offset.val\n  ret ptr %adj\n",
                    self.source_type, object, object
                )
            }
            DynCastStrategy::Downcast | DynCastStrategy::CrossCast => {
                if self.is_ref_cast {
                    format!(
                        r#"; dynamic_cast throw-on-fail: {} → {}
  %result = call ptr @__dynamic_cast(ptr {}, ptr @_ZTI{}, ptr @_ZTI{}, i64 0)
  %is_null = icmp eq ptr %result, null
  br i1 %is_null, label %throw_bad_cast, label %success
throw_bad_cast:
  call void @__cxa_bad_cast()
  unreachable
success:
  ret ptr %result
"#,
                        self.source_type,
                        self.target_type,
                        object,
                        self.source_type,
                        self.target_type
                    )
                } else {
                    format!(
                        "  %result = call ptr @__dynamic_cast(ptr {}, ptr @_ZTI{}, ptr @_ZTI{}, i64 0)\n  ret ptr %result\n",
                        object, self.source_type, self.target_type
                    )
                }
            }
        }
    }

    /// Check if the class hierarchy supports this cast.
    /// Walks the class hierarchy looking for the target type.
    pub fn check_hierarchy(source_hierarchy: &[String], target: &str) -> Option<DynCastStrategy> {
        if source_hierarchy.is_empty() {
            return None;
        }

        if source_hierarchy[0] == target || source_hierarchy.iter().any(|t| t == target) {
            // source is target or target is a base
            Some(if source_hierarchy[0] == target {
                DynCastStrategy::Identity
            } else {
                DynCastStrategy::Downcast
            })
        } else if target == "void" {
            Some(DynCastStrategy::ToVoid)
        } else {
            None
        }
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// typeid Operator
// ═══════════════════════════════════════════════════════════════════════════════

/// Represents the `typeid` operator evaluation.
#[derive(Debug, Clone)]
pub struct TypeidOperator {
    /// The type operand.
    pub type_name: String,
    /// Whether this is `typeid(type)` or `typeid(expr)`.
    pub is_type: bool,
    /// Whether the result is the dynamic type (for polymorphic objects).
    pub is_dynamic: bool,
}

impl TypeidOperator {
    pub fn new(type_name: &str) -> Self {
        Self {
            type_name: type_name.to_string(),
            is_type: true,
            is_dynamic: false,
        }
    }

    /// Create a dynamic typeid (for polymorphic expressions).
    pub fn dynamic(expr_type: &str) -> Self {
        Self {
            type_name: expr_type.to_string(),
            is_type: false,
            is_dynamic: true,
        }
    }

    /// Generate IR for `typeid(type)` — static type, returns type_info reference.
    pub fn gen_static_typeid_ir(&self) -> String {
        format!(
            "  ; typeid({})\n  ret ptr @_ZTI{}\n",
            self.type_name, self.type_name
        )
    }

    /// Generate IR for `typeid(expr)` — dynamic type, uses vtable lookup.
    pub fn gen_dynamic_typeid_ir(&self, object_ptr: &str) -> String {
        format!(
            r#"; typeid(dynamic expr of type {})
  %vtable = load ptr, ptr {}
  %typeinfo.ptr = getelementptr inbounds ptr, ptr %vtable, i64 -1
  %typeinfo = load ptr, ptr %typeinfo.ptr
  ret ptr %typeinfo
"#,
            self.type_name, object_ptr
        )
    }

    /// Check if typeid requires RTTI to be enabled.
    pub fn requires_rtti(&self) -> bool {
        true // typeid always requires RTTI
    }

    /// Generate the IR for a typeid comparison: `typeid(a) == typeid(b)`.
    pub fn gen_typeid_compare_ir(a_type: &str, b_type: &str) -> String {
        format!(
            "  %eq = icmp eq ptr @_ZTI{}, ptr @_ZTI{}\n  ret i1 %eq\n",
            a_type, b_type
        )
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Emission: Sections, VTable Pointer, Name String
// ═══════════════════════════════════════════════════════════════════════════════

/// Configures the emission of RTTI data.
#[derive(Debug, Clone)]
pub struct RttiEmissionConfig {
    /// The target triple (affects RTTI layout).
    pub target_triple: String,
    /// Whether to emit type_info in COMDAT groups.
    pub use_comdat: bool,
    /// The data section for type_info objects.
    pub data_section: String,
    /// Whether to emit vtable pointers inline or as references.
    pub inline_vtable_ptrs: bool,
    /// Whether RTTI is enabled at all.
    pub rtti_enabled: bool,
}

impl RttiEmissionConfig {
    pub fn new(target_triple: &str) -> Self {
        Self {
            target_triple: target_triple.to_string(),
            use_comdat: true,
            data_section: ".data.rel.ro".to_string(),
            inline_vtable_ptrs: false,
            rtti_enabled: true,
        }
    }

    /// Disable RTTI emission (equivalent to -fno-rtti).
    pub fn disable_rtti(mut self) -> Self {
        self.rtti_enabled = false;
        self
    }

    /// Emit a type_info global with proper linkage and section.
    pub fn emit_global_typeinfo(
        &self,
        sym: &str,
        vtable: &str,
        name_sym: &str,
        kind: RttiKind,
    ) -> String {
        if !self.rtti_enabled {
            return format!("; RTTI disabled, skipping type_info for '{}'\n", sym);
        }

        let linkage = if self.use_comdat {
            format!("linkonce_odr")
        } else {
            "private".to_string()
        };

        let section = &self.data_section;

        match kind {
            RttiKind::Class | RttiKind::Fundamental => {
                format!(
                    "@{} = {} constant {{ ptr, ptr }} {{ ptr {}, ptr @{} }}, align 8, section \"{}\"\n",
                    sym, linkage, vtable, name_sym, section
                )
            }
            RttiKind::SiClass => {
                format!(
                    "@{} = {} constant {{ ptr, ptr, ptr }} {{ ptr {}, ptr @{}, ptr null }}, align 8, section \"{}\"\n",
                    sym, linkage, vtable, name_sym, section
                )
            }
            _ => {
                format!(
                    "@{} = {} constant {{ ptr, ptr }} {{ ptr {}, ptr @{} }}, align 8, section \"{}\"\n",
                    sym, linkage, vtable, name_sym, section
                )
            }
        }
    }

    /// Emit the type_info name string (the demangled class name).
    pub fn emit_name_string(&self, sym: &str, class_name: &str) -> String {
        if !self.rtti_enabled {
            return String::new();
        }

        format!(
            "@{} = private unnamed_addr constant [{} x i8] c\"{}\\00\", align 1\n",
            sym,
            class_name.len() + 1,
            class_name
        )
    }

    /// Emit a vtable pointer reference for type_info.
    pub fn emit_vtable_ptr_decl(sym: &str) -> String {
        format!("@{} = external constant ptr ; type_info vtable\n", sym)
    }
}

impl Default for RttiEmissionConfig {
    fn default() -> Self {
        Self::new("x86_64-unknown-linux-gnu")
    }
}

/// Emit the complete RTTI for a translation unit as a combined LLVM IR module.
pub fn emit_rtti_module(
    config: &RttiEmissionConfig,
    types: &[(String, RttiKind, Option<String>)],
) -> String {
    let mut ir = String::new();
    ir.push_str("; RTTI Module\n");
    ir.push_str("; Target: ");
    ir.push_str(&config.target_triple);
    ir.push_str("\n\n");

    for (name, kind, vtable) in types {
        let name_sym = format!("_ZTS{}", name);
        let typeinfo_sym = format!("_ZTI{}", name);
        let vtable_sym = vtable.as_deref().unwrap_or("null");

        ir.push_str(&config.emit_name_string(&name_sym, name));
        ir.push_str(&config.emit_global_typeinfo(&typeinfo_sym, vtable_sym, &name_sym, *kind));
        ir.push('\n');
    }

    ir
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Class Hierarchy Walking
// ═══════════════════════════════════════════════════════════════════════════════

/// Walks the class hierarchy for dynamic_cast and typeid.
#[derive(Debug, Clone)]
pub struct ClassHierarchyWalker {
    /// The root class of the walk.
    pub root: String,
    /// All classes in the hierarchy.
    pub hierarchy: Vec<HierarchyEntry>,
    /// Depth of the deepest base.
    pub max_depth: usize,
}

/// An entry in the class hierarchy.
#[derive(Debug, Clone)]
pub struct HierarchyEntry {
    /// The class name.
    pub class_name: String,
    /// The RTTI descriptor.
    pub typeinfo: Option<String>,
    /// The base class name.
    pub base: Option<String>,
    /// Whether the base is virtual.
    pub is_virtual: bool,
    /// The offset from derived to base.
    pub offset: i64,
    /// Depth in the hierarchy.
    pub depth: usize,
}

impl ClassHierarchyWalker {
    pub fn new(root: &str) -> Self {
        Self {
            root: root.to_string(),
            hierarchy: vec![HierarchyEntry {
                class_name: root.to_string(),
                typeinfo: Some(format!("_ZTI{}", root)),
                base: None,
                is_virtual: false,
                offset: 0,
                depth: 0,
            }],
            max_depth: 0,
        }
    }

    /// Add a derived class with its base.
    pub fn add_derived(&mut self, class: &str, base: &str, is_virtual: bool, offset: i64) {
        let depth = self
            .hierarchy
            .iter()
            .find(|e| e.class_name == base)
            .map(|e| e.depth + 1)
            .unwrap_or(0);
        if depth > self.max_depth {
            self.max_depth = depth;
        }
        self.hierarchy.push(HierarchyEntry {
            class_name: class.to_string(),
            typeinfo: Some(format!("_ZTI{}", class)),
            base: Some(base.to_string()),
            is_virtual,
            offset,
            depth,
        });
    }

    /// Find the path from `derived` to `base` in the hierarchy.
    pub fn find_path(&self, derived: &str, base: &str) -> Option<Vec<String>> {
        if derived == base {
            return Some(vec![derived.to_string()]);
        }
        let mut current = derived;
        let mut path = vec![current.to_string()];
        let mut visited = std::collections::HashSet::new();
        visited.insert(current.to_string());

        while let Some(entry) = self.hierarchy.iter().find(|e| e.class_name == current) {
            if let Some(ref b) = entry.base {
                if b == base {
                    path.push(b.clone());
                    return Some(path);
                }
                if visited.contains(b.as_str()) {
                    return None; // cycle
                }
                visited.insert(b.clone());
                path.push(b.clone());
                current = b.as_str();
            } else {
                return None; // no base, path incomplete
            }
        }
        None
    }

    /// Calculate the total offset from derived to base.
    pub fn calculate_offset(&self, derived: &str, base: &str) -> Option<i64> {
        let mut total = 0i64;
        let mut current = derived;
        while let Some(entry) = self.hierarchy.iter().find(|e| e.class_name == current) {
            if entry.class_name == base {
                return Some(total);
            }
            if let Some(ref b) = entry.base {
                total += entry.offset;
                current = b;
            } else {
                return None;
            }
        }
        None
    }

    /// Generate the IR to walk the hierarchy at runtime for dynamic_cast.
    pub fn gen_hierarchy_walk_ir(&self, obj: &str, target_typeinfo: &str) -> String {
        let mut ir = String::new();
        ir.push_str(&format!("; Hierarchy walk from '{}'\n", self.root));

        for entry in &self.hierarchy {
            if let Some(ref ti) = entry.typeinfo {
                ir.push_str(&format!(
                    "  %check.{} = icmp eq ptr @{}, ptr @{}\n",
                    entry.class_name, ti, target_typeinfo
                ));
                ir.push_str(&format!(
                    "  br i1 %check.{}, label %found.{}, label %next.{}\n",
                    entry.class_name, entry.class_name, entry.class_name
                ));
                ir.push_str(&format!(
                    "found.{}:\n  ret ptr {}\n\n",
                    entry.class_name, obj
                ));
                ir.push_str(&format!("next.{}:\n", entry.class_name));
            }
        }

        ir.push_str("  ret ptr null ; cast failed\n");
        ir
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Linkonce ODR COMDAT Emission
// ═══════════════════════════════════════════════════════════════════════════════

/// Emits RTTI objects with linkonce_odr linkage and COMDAT grouping.
#[derive(Debug, Clone)]
pub struct ComdatRttiEmitter {
    /// The COMDAT key generator.
    pub comdat_counter: usize,
}

impl ComdatRttiEmitter {
    pub fn new() -> Self {
        Self { comdat_counter: 0 }
    }

    /// Emit a type_info with COMDAT support.
    pub fn emit_comdat_typeinfo(
        &mut self,
        type_name: &str,
        kind: RttiKind,
        vtable_sym: &str,
    ) -> String {
        self.comdat_counter += 1;
        let comdat_key = format!("__typeinfo_{}", type_name);
        let mut ir = String::new();

        ir.push_str(&format!("${} = comdat any\n", comdat_key));
        ir.push_str(&format!(
            "@_ZTI{} = linkonce_odr constant {{ ptr, ptr }} {{ ptr {}, ptr @_ZTS{} }}, comdat(${})\n",
            type_name, vtable_sym, type_name, comdat_key
        ));

        ir
    }

    /// Emit a type_info name string with COMDAT.
    pub fn emit_comdat_name_string(&mut self, type_name: &str) -> String {
        let comdat_key = format!("__typeinfo_name_{}", type_name);
        format!(
            "@_ZTS{} = linkonce_odr constant [{} x i8] c\"{}\\00\", comdat(${}), align 1\n",
            type_name,
            type_name.len() + 1,
            type_name,
            comdat_key
        )
    }

    /// Emit a complete type_info + name pair with COMDAT.
    pub fn emit_typeinfo_pair(
        &mut self,
        type_name: &str,
        kind: RttiKind,
        vtable_sym: &str,
    ) -> String {
        let mut ir = self.emit_comdat_name_string(type_name);
        ir.push_str(&self.emit_comdat_typeinfo(type_name, kind, vtable_sym));
        ir
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// RTTI Flags and Base-Class Encoding
// ═══════════════════════════════════════════════════════════════════════════════

/// RTTI flags for base class descriptors per Itanium ABI.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct RttiBaseFlags(u32);

impl RttiBaseFlags {
    /// No flags set.
    pub const NONE: Self = Self(0);
    /// Base is virtual.
    pub const VIRTUAL: Self = Self(1 << 0);
    /// Base is public.
    pub const PUBLIC: Self = Self(1 << 1);
    /// Base is protected.
    pub const PROTECTED: Self = Self(1 << 2);
    /// Base is private.
    pub const PRIVATE: Self = Self(1 << 3);

    /// Check if a flag is set.
    pub fn has(&self, flag: Self) -> bool {
        (self.0 & flag.0) != 0
    }

    /// Set a flag.
    pub fn set(&mut self, flag: Self) {
        self.0 |= flag.0;
    }

    /// Get the raw flags value.
    pub fn raw(&self) -> u32 {
        self.0
    }

    /// Parse from access specifier and virtual flag.
    pub fn from_access(is_virtual: bool, is_public: bool, is_protected: bool) -> Self {
        let mut flags = Self::NONE;
        if is_virtual {
            flags.set(Self::VIRTUAL);
        }
        if is_public {
            flags.set(Self::PUBLIC);
        } else if is_protected {
            flags.set(Self::PROTECTED);
        } else {
            flags.set(Self::PRIVATE);
        }
        flags
    }
}

/// Encodes base class information in __vmi_class_type_info.
#[derive(Debug, Clone)]
pub struct VmiBaseEncoder {
    /// The base classes.
    pub bases: Vec<VmiBaseEntry>,
    /// The vmi flags.
    pub flags: u32,
}

/// A base class entry in VMI.
#[derive(Debug, Clone)]
pub struct VmiBaseEntry {
    /// The base type_info.
    pub typeinfo: String,
    /// The offset flags.
    pub offset_flags: u32,
    /// The offset from derived to this base.
    pub offset: i64,
}

impl VmiBaseEncoder {
    pub fn new() -> Self {
        Self {
            bases: Vec::new(),
            flags: 0,
        }
    }

    /// Add a base class with its offset.
    pub fn add_base(&mut self, typeinfo: &str, offset: i64, is_virtual: bool, is_public: bool) {
        let flags = RttiBaseFlags::from_access(is_virtual, is_public, false);
        self.bases.push(VmiBaseEntry {
            typeinfo: typeinfo.to_string(),
            offset_flags: flags.raw(),
            offset,
        });
    }

    /// Generate the LLVM IR for the VMI base array.
    pub fn gen_base_array_ir(&self) -> String {
        let mut ir = String::new();
        ir.push_str(&format!("  [{} x {{ ptr, i64 }}] [\n", self.bases.len()));
        for (i, base) in self.bases.iter().enumerate() {
            if i > 0 {
                ir.push_str(",\n");
            }
            ir.push_str(&format!(
                "    {{ ptr @{}, i64 {} }}",
                base.typeinfo, base.offset
            ));
        }
        ir.push_str("\n  ]");
        ir
    }

    /// Generate the full __vmi_class_type_info descriptor.
    pub fn gen_vmi_typeinfo_ir(&self, sym: &str, name_sym: &str, vtable: &str) -> String {
        format!(
            "@{} = private constant {{ ptr, ptr, i32, i32, [{} x {{ ptr, i64 }}] }} {{ ptr {}, ptr @{}, i32 {}, i32 {}, {}\n}}, align 8\n",
            sym,
            self.bases.len(),
            vtable,
            name_sym,
            self.flags,
            self.bases.len(),
            self.gen_base_array_ir()
        )
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// Pointer-to-Member and Array Type Info
// ═══════════════════════════════════════════════════════════════════════════════

/// RTTI for pointer-to-member types.
#[derive(Debug, Clone)]
pub struct PointerToMemberTypeInfo {
    /// The class type for the pointer-to-member.
    pub class_type: String,
    /// The member type.
    pub member_type: String,
    /// The member type's typeinfo.
    pub member_typeinfo: Option<String>,
}

impl PointerToMemberTypeInfo {
    pub fn new(class_type: &str, member_type: &str) -> Self {
        Self {
            class_type: class_type.to_string(),
            member_type: member_type.to_string(),
            member_typeinfo: None,
        }
    }

    /// Emit the pointer-to-member RTTI descriptor.
    pub fn emit_ir(&self, sym: &str, name_sym: &str, vtable: &str) -> String {
        let member_ti = self.member_typeinfo.as_deref().unwrap_or("null");
        format!(
            "@{} = private constant {{ ptr, ptr, ptr, ptr }} {{ ptr {}, ptr @{}, ptr @_ZTI{}, ptr @{} }}\n",
            sym, vtable, name_sym, self.class_type, member_ti
        )
    }
}

/// RTTI for array types.
#[derive(Debug, Clone)]
pub struct ArrayTypeInfo {
    /// The element type info.
    pub element_type: String,
    /// The array bounds (None for unbounded).
    pub bounds: Option<usize>,
}

impl ArrayTypeInfo {
    pub fn new(element_type: &str) -> Self {
        Self {
            element_type: element_type.to_string(),
            bounds: None,
        }
    }

    /// Emit the array type RTTI descriptor.
    pub fn emit_ir(&self, sym: &str, name_sym: &str, vtable: &str) -> String {
        let bounds_str = self
            .bounds
            .map(|n| n.to_string())
            .unwrap_or_else(|| "0".to_string());
        format!(
            "@{} = private constant {{ ptr, ptr, ptr, i64 }} {{ ptr {}, ptr @{}, ptr @_ZTI{}, i64 {} }}, align 8\n",
            sym, vtable, name_sym, self.element_type, bounds_str
        )
    }
}

// ═══════════════════════════════════════════════════════════════════════════════
// Tests
// ═══════════════════════════════════════════════════════════════════════════════

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_rtti_kind_class_name() {
        assert_eq!(RttiKind::Fundamental.class_name(), "type_info");
        assert_eq!(RttiKind::Class.class_name(), "__class_type_info");
        assert_eq!(RttiKind::SiClass.class_name(), "__si_class_type_info");
        assert_eq!(RttiKind::VmiClass.class_name(), "__vmi_class_type_info");
        assert_eq!(RttiKind::Pointer.class_name(), "__pointer_type_info");
    }

    #[test]
    fn test_build_fundamental_rtti() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_fundamental_rtti("int");
        assert_eq!(desc.kind, RttiKind::Fundamental);
        assert!(desc.typeinfo_symbol.as_str().starts_with("_ZTI"));
        assert!(desc.typeinfo_name_symbol.as_str().starts_with("_ZTS"));
    }

    #[test]
    fn test_build_class_rtti_no_bases() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_class_rtti("MyClass", &[]);
        assert_eq!(desc.kind, RttiKind::Class);
        assert!(desc.name_string.contains("MyClass"));
    }

    #[test]
    fn test_build_class_rtti_single_base() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_class_rtti("Derived", &[("Base".into(), false, true)]);
        assert_eq!(desc.kind, RttiKind::SiClass);
        assert!(desc.base_type.is_some());
        assert_eq!(desc.base_type.as_ref().unwrap().type_name, "Base");
    }

    #[test]
    fn test_build_class_rtti_virtual_base() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_class_rtti(
            "Derived",
            &[("Base1".into(), false, true), ("Base2".into(), true, true)],
        );
        assert_eq!(desc.kind, RttiKind::VmiClass);
        assert_eq!(desc.base_info.len(), 2);
    }

    #[test]
    fn test_build_pointer_rtti() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_pointer_rtti("int");
        assert_eq!(desc.kind, RttiKind::Pointer);
        assert!(desc.pointee_type.is_some());
    }

    #[test]
    fn test_emit_rtti_ir() {
        let mut builder = RttiBuilder::new();
        builder.build_class_rtti("Foo", &[]);
        let ir = builder.emit_all_ir();
        assert!(ir.contains("_ZTS3Foo"));
        assert!(ir.contains("_ZTI3Foo"));
    }

    #[test]
    fn test_emit_name_ir() {
        let mut builder = RttiBuilder::new();
        let desc = builder.build_class_rtti("Bar", &[]);
        let ir = desc.emit_name_ir();
        assert!(ir.contains("Bar"));
        assert!(ir.contains("_ZTS"));
    }

    #[test]
    fn test_rtti_descriptor_clone() {
        let mut builder = RttiBuilder::new();
        builder.build_fundamental_rtti("double");
        let desc = builder.get_descriptor("double").unwrap();
        let cloned = desc.clone();
        assert_eq!(cloned.type_name, desc.type_name);
    }

    #[test]
    fn test_typeinfo_vtable_constants() {
        assert!(typeinfo_vtables::GCC_LINUX_TYPEINFO_VTABLE.contains("class_type_info"));
        assert!(typeinfo_vtables::GCC_LINUX_SI_CLASS_TYPEINFO_VTABLE.contains("si_class_type_info"));
    }
}