alef-codegen 0.3.4

use crate::generators::{AsyncPattern, RustBindingConfig};
use ahash::AHashSet;
use alef_core::ir::{ParamDef, TypeDef, TypeRef};
use std::fmt::Write;

/// Wrap a core-call result for opaque delegation methods.
///
/// - `TypeRef::Named(n)` where `n == type_name` → re-wrap in `Self { inner: Arc::new(...) }`
/// - `TypeRef::Named(n)` where `n` is another opaque type → wrap in `{n} { inner: Arc::new(...) }`
/// - `TypeRef::Named(n)` where `n` is a non-opaque type → `todo!()` placeholder (From may not exist)
/// - Everything else (primitives, String, Vec, etc.) → pass through unchanged
/// - `TypeRef::Unit` → pass through unchanged
///
/// When `returns_cow` is true the core method returns `Cow<'_, T>`. `.into_owned()` is emitted
/// before any further type conversion to obtain an owned `T`.
pub fn wrap_return(
    expr: &str,
    return_type: &TypeRef,
    type_name: &str,
    opaque_types: &AHashSet<String>,
    self_is_opaque: bool,
    returns_ref: bool,
    returns_cow: bool,
) -> String {
    match return_type {
        TypeRef::Named(n) if n == type_name && self_is_opaque => {
            if returns_cow {
                format!("Self {{ inner: Arc::new({expr}.into_owned()) }}")
            } else if returns_ref {
                format!("Self {{ inner: Arc::new({expr}.clone()) }}")
            } else {
                format!("Self {{ inner: Arc::new({expr}) }}")
            }
        }
        TypeRef::Named(n) if opaque_types.contains(n.as_str()) => {
            if returns_cow {
                format!("{n} {{ inner: Arc::new({expr}.into_owned()) }}")
            } else if returns_ref {
                format!("{n} {{ inner: Arc::new({expr}.clone()) }}")
            } else {
                format!("{n} {{ inner: Arc::new({expr}) }}")
            }
        }
        TypeRef::Named(_) => {
            // Non-opaque Named return type — use .into() for core→binding From conversion.
            // When the core returns a Cow, call .into_owned() first to get an owned T.
            // When the core returns a reference, clone first since From<&T> typically doesn't exist.
            if returns_cow {
                format!("{expr}.into_owned().into()")
            } else if returns_ref {
                format!("{expr}.clone().into()")
            } else {
                format!("{expr}.into()")
            }
        }
        // String/Bytes: only convert when the core returns a reference (&str→String, &[u8]→Vec<u8>).
        // When owned (returns_ref=false), both sides are already String/Vec<u8> — skip .into().
        TypeRef::String | TypeRef::Bytes => {
            if returns_ref {
                format!("{expr}.into()")
            } else {
                expr.to_string()
            }
        }
        // Path: PathBuf→String needs to_string_lossy, &Path→String too
        TypeRef::Path => format!("{expr}.to_string_lossy().to_string()"),
        // Duration: core returns std::time::Duration, binding uses u64 (millis)
        TypeRef::Duration => format!("{expr}.as_millis() as u64"),
        // Json: serde_json::Value needs serialization to string
        TypeRef::Json => format!("{expr}.to_string()"),
        // Optional: wrap inner conversion in .map(...)
        TypeRef::Optional(inner) => match inner.as_ref() {
            TypeRef::Named(n) if opaque_types.contains(n.as_str()) => {
                if returns_ref {
                    format!("{expr}.map(|v| {n} {{ inner: Arc::new(v.clone()) }})")
                } else {
                    format!("{expr}.map(|v| {n} {{ inner: Arc::new(v) }})")
                }
            }
            TypeRef::Named(_) => {
                if returns_ref {
                    format!("{expr}.map(|v| v.clone().into())")
                } else {
                    format!("{expr}.map(Into::into)")
                }
            }
            TypeRef::Path => {
                format!("{expr}.map(Into::into)")
            }
            TypeRef::String | TypeRef::Bytes => {
                if returns_ref {
                    format!("{expr}.map(Into::into)")
                } else {
                    expr.to_string()
                }
            }
            TypeRef::Duration => format!("{expr}.map(|d| d.as_millis() as u64)"),
            TypeRef::Json => format!("{expr}.map(ToString::to_string)"),
            _ => expr.to_string(),
        },
        // Vec: map each element through the appropriate conversion
        TypeRef::Vec(inner) => match inner.as_ref() {
            TypeRef::Named(n) if opaque_types.contains(n.as_str()) => {
                if returns_ref {
                    format!("{expr}.into_iter().map(|v| {n} {{ inner: Arc::new(v.clone()) }}).collect()")
                } else {
                    format!("{expr}.into_iter().map(|v| {n} {{ inner: Arc::new(v) }}).collect()")
                }
            }
            TypeRef::Named(_) => {
                if returns_ref {
                    format!("{expr}.into_iter().map(|v| v.clone().into()).collect()")
                } else {
                    format!("{expr}.into_iter().map(Into::into).collect()")
                }
            }
            TypeRef::Path => {
                format!("{expr}.into_iter().map(Into::into).collect()")
            }
            TypeRef::String | TypeRef::Bytes => {
                if returns_ref {
                    format!("{expr}.into_iter().map(Into::into).collect()")
                } else {
                    expr.to_string()
                }
            }
            _ => expr.to_string(),
        },
        _ => expr.to_string(),
    }
}

/// Unwrap a newtype return value when `return_newtype_wrapper` is set.
///
/// Core function returns a newtype (e.g. `NodeIndex(u32)`), but the binding return type
/// is the inner type (e.g. `u32`). Access `.0` to unwrap the newtype.
pub fn apply_return_newtype_unwrap(expr: &str, return_newtype_wrapper: &Option<String>) -> String {
    match return_newtype_wrapper {
        Some(_) => format!("({expr}).0"),
        None => expr.to_string(),
    }
}

/// Build call argument expressions from parameters.
/// - Opaque Named types: unwrap Arc wrapper via `(*param.inner).clone()`
/// - Non-opaque Named types: `.into()` for From conversion
/// - String/Path/Bytes: `&param` since core functions typically take `&str`/`&Path`/`&[u8]`
/// - Params with `newtype_wrapper` set: re-wrap the raw value in the newtype constructor
///   (e.g., `NodeIndex(parent)`) since the binding resolved `NodeIndex(u32)` → `u32`.
pub fn gen_call_args(params: &[ParamDef], opaque_types: &AHashSet<String>) -> String {
    params
        .iter()
        .enumerate()
        .map(|(idx, p)| {
            let promoted = crate::shared::is_promoted_optional(params, idx);
            // If a required param was promoted to optional, unwrap it before use
            let unwrap_suffix = if promoted {
                format!(".expect(\"'{}' is required\")", p.name)
            } else {
                String::new()
            };
            // If this param's type was resolved from a newtype (e.g. NodeIndex(u32) → u32),
            // re-wrap the raw value back into the newtype when calling core.
            if let Some(newtype_path) = &p.newtype_wrapper {
                return if p.optional {
                    format!("{}.map({newtype_path})", p.name)
                } else if promoted {
                    format!("{newtype_path}({}{})", p.name, unwrap_suffix)
                } else {
                    format!("{newtype_path}({})", p.name)
                };
            }
            match &p.ty {
                TypeRef::Named(name) if opaque_types.contains(name.as_str()) => {
                    // Opaque type: borrow through Arc to get &CoreType
                    if p.optional {
                        format!("{}.as_ref().map(|v| &v.inner)", p.name)
                    } else if promoted {
                        format!("{}{}.inner.as_ref()", p.name, unwrap_suffix)
                    } else {
                        format!("&{}.inner", p.name)
                    }
                }
                TypeRef::Named(_) => {
                    if p.optional {
                        format!("{}.map(Into::into)", p.name)
                    } else if promoted {
                        format!("{}{}.into()", p.name, unwrap_suffix)
                    } else {
                        format!("{}.into()", p.name)
                    }
                }
                // String → &str for core function calls when is_ref=true,
                // or pass owned when is_ref=false (core takes String/impl Into<String>).
                // For optional params: as_deref() when is_ref=true, pass owned when is_ref=false.
                TypeRef::String | TypeRef::Char => {
                    if p.optional {
                        if p.is_ref {
                            format!("{}.as_deref()", p.name)
                        } else {
                            p.name.clone()
                        }
                    } else if promoted {
                        if p.is_ref {
                            format!("&{}{}", p.name, unwrap_suffix)
                        } else {
                            format!("{}{}", p.name, unwrap_suffix)
                        }
                    } else if p.is_ref {
                        format!("&{}", p.name)
                    } else {
                        p.name.clone()
                    }
                }
                // Path → PathBuf/&Path for core function calls
                TypeRef::Path => {
                    if p.optional && p.is_ref {
                        format!("{}.as_deref().map(std::path::Path::new)", p.name)
                    } else if p.optional {
                        format!("{}.map(std::path::PathBuf::from)", p.name)
                    } else if promoted {
                        format!("std::path::PathBuf::from({}{})", p.name, unwrap_suffix)
                    } else if p.is_ref {
                        format!("std::path::Path::new(&{})", p.name)
                    } else {
                        format!("std::path::PathBuf::from({})", p.name)
                    }
                }
                TypeRef::Bytes => {
                    if p.optional {
                        if p.is_ref {
                            format!("{}.as_deref()", p.name)
                        } else {
                            p.name.clone()
                        }
                    } else if promoted {
                        format!("&{}{}", p.name, unwrap_suffix)
                    } else {
                        format!("&{}", p.name)
                    }
                }
                // Duration: binding uses u64 (millis), core uses std::time::Duration
                TypeRef::Duration => {
                    if p.optional {
                        format!("{}.map(std::time::Duration::from_millis)", p.name)
                    } else if promoted {
                        format!("std::time::Duration::from_millis({}{})", p.name, unwrap_suffix)
                    } else {
                        format!("std::time::Duration::from_millis({})", p.name)
                    }
                }
                _ => {
                    if promoted {
                        format!("{}{}", p.name, unwrap_suffix)
                    } else {
                        p.name.clone()
                    }
                }
            }
        })
        .collect::<Vec<_>>()
        .join(", ")
}

/// Build call argument expressions using pre-bound let bindings for non-opaque Named params.
/// Non-opaque Named params use `&{name}_core` references instead of `.into()`.
pub fn gen_call_args_with_let_bindings(params: &[ParamDef], opaque_types: &AHashSet<String>) -> String {
    params
        .iter()
        .enumerate()
        .map(|(idx, p)| {
            let promoted = crate::shared::is_promoted_optional(params, idx);
            let unwrap_suffix = if promoted {
                format!(".expect(\"'{}' is required\")", p.name)
            } else {
                String::new()
            };
            // If this param's type was resolved from a newtype, re-wrap when calling core.
            if let Some(newtype_path) = &p.newtype_wrapper {
                return if p.optional {
                    format!("{}.map({newtype_path})", p.name)
                } else if promoted {
                    format!("{newtype_path}({}{})", p.name, unwrap_suffix)
                } else {
                    format!("{newtype_path}({})", p.name)
                };
            }
            match &p.ty {
                TypeRef::Named(name) if opaque_types.contains(name.as_str()) => {
                    if p.optional {
                        format!("{}.as_ref().map(|v| &v.inner)", p.name)
                    } else if promoted {
                        format!("{}{}.inner.as_ref()", p.name, unwrap_suffix)
                    } else {
                        format!("&{}.inner", p.name)
                    }
                }
                TypeRef::Named(_) if p.is_ref => {
                    format!("&{}_core", p.name)
                }
                TypeRef::Named(_) => {
                    format!("{}_core", p.name)
                }
                TypeRef::String | TypeRef::Char => {
                    if p.optional {
                        if p.is_ref {
                            format!("{}.as_deref()", p.name)
                        } else {
                            p.name.clone()
                        }
                    } else if promoted {
                        if p.is_ref {
                            format!("&{}{}", p.name, unwrap_suffix)
                        } else {
                            format!("{}{}", p.name, unwrap_suffix)
                        }
                    } else if p.is_ref {
                        format!("&{}", p.name)
                    } else {
                        p.name.clone()
                    }
                }
                TypeRef::Path => {
                    if promoted {
                        format!("std::path::PathBuf::from({}{})", p.name, unwrap_suffix)
                    } else if p.optional && p.is_ref {
                        format!("{}.as_deref().map(std::path::Path::new)", p.name)
                    } else if p.optional {
                        format!("{}.map(std::path::PathBuf::from)", p.name)
                    } else if p.is_ref {
                        format!("std::path::Path::new(&{})", p.name)
                    } else {
                        format!("std::path::PathBuf::from({})", p.name)
                    }
                }
                TypeRef::Bytes => {
                    if p.optional {
                        if p.is_ref {
                            format!("{}.as_deref()", p.name)
                        } else {
                            p.name.clone()
                        }
                    } else if promoted {
                        format!("&{}{}", p.name, unwrap_suffix)
                    } else {
                        format!("&{}", p.name)
                    }
                }
                TypeRef::Duration => {
                    if p.optional {
                        format!("{}.map(std::time::Duration::from_millis)", p.name)
                    } else if promoted {
                        format!("std::time::Duration::from_millis({}{})", p.name, unwrap_suffix)
                    } else {
                        format!("std::time::Duration::from_millis({})", p.name)
                    }
                }
                _ => {
                    if promoted {
                        format!("{}{}", p.name, unwrap_suffix)
                    } else {
                        p.name.clone()
                    }
                }
            }
        })
        .collect::<Vec<_>>()
        .join(", ")
}

/// Generate let bindings for non-opaque Named params, converting them to core types.
pub fn gen_named_let_bindings_pub(params: &[ParamDef], opaque_types: &AHashSet<String>) -> String {
    gen_named_let_bindings(params, opaque_types)
}

pub(super) fn gen_named_let_bindings(params: &[ParamDef], opaque_types: &AHashSet<String>) -> String {
    let mut bindings = String::new();
    for (idx, p) in params.iter().enumerate() {
        if let TypeRef::Named(name) = &p.ty {
            if !opaque_types.contains(name.as_str()) {
                let promoted = crate::shared::is_promoted_optional(params, idx);
                if p.optional {
                    write!(bindings, "let {}_core = {}.map(Into::into);\n    ", p.name, p.name).ok();
                } else if promoted {
                    // Promoted-optional: unwrap then convert
                    write!(
                        bindings,
                        "let {}_core = {}.expect(\"'{}' is required\").into();\n    ",
                        p.name, p.name, p.name
                    )
                    .ok();
                } else {
                    write!(bindings, "let {}_core = {}.into();\n    ", p.name, p.name).ok();
                }
            }
        }
    }
    bindings
}

/// Generate serde-based let bindings for non-opaque Named params.
/// Serializes binding types to JSON and deserializes to core types.
/// Used when From impls don't exist (e.g., types with sanitized fields).
/// `indent` is the whitespace prefix for each generated line (e.g., "    " for functions, "        " for methods).
pub fn gen_serde_let_bindings(
    params: &[ParamDef],
    opaque_types: &AHashSet<String>,
    core_import: &str,
    err_conv: &str,
    indent: &str,
) -> String {
    let mut bindings = String::new();
    for p in params {
        if let TypeRef::Named(name) = &p.ty {
            if !opaque_types.contains(name.as_str()) {
                let core_path = format!("{}::{}", core_import, name);
                if p.optional {
                    write!(
                        bindings,
                        "let {name}_core: Option<{core_path}> = {name}.map(|v| {{\n\
                         {indent}    let json = serde_json::to_string(&v){err_conv}?;\n\
                         {indent}    serde_json::from_str(&json){err_conv}\n\
                         {indent}}}).transpose()?;\n{indent}",
                        name = p.name,
                        core_path = core_path,
                        err_conv = err_conv,
                        indent = indent,
                    )
                    .ok();
                } else {
                    write!(
                        bindings,
                        "let {name}_json = serde_json::to_string(&{name}){err_conv}?;\n\
                         {indent}let {name}_core: {core_path} = serde_json::from_str(&{name}_json){err_conv}?;\n{indent}",
                        name = p.name,
                        core_path = core_path,
                        err_conv = err_conv,
                        indent = indent,
                    )
                    .ok();
                }
            }
        }
    }
    bindings
}

/// Check if params contain any non-opaque Named types that need let bindings.
pub fn has_named_params(params: &[ParamDef], opaque_types: &AHashSet<String>) -> bool {
    params
        .iter()
        .any(|p| matches!(&p.ty, TypeRef::Named(name) if !opaque_types.contains(name.as_str())))
}

/// Check if a param type is safe for non-opaque delegation (no complex conversions needed).
/// Vec and Map params can cause type mismatches (e.g. Vec<String> vs &[&str]).
pub fn is_simple_non_opaque_param(ty: &TypeRef) -> bool {
    match ty {
        TypeRef::Primitive(_)
        | TypeRef::String
        | TypeRef::Char
        | TypeRef::Bytes
        | TypeRef::Path
        | TypeRef::Unit
        | TypeRef::Duration => true,
        TypeRef::Optional(inner) => is_simple_non_opaque_param(inner),
        _ => false,
    }
}

/// Generate a lossy binding→core struct literal for non-opaque delegation.
/// Sanitized fields use `Default::default()`, non-sanitized fields are cloned and converted.
/// Fields are accessed via `self.` (behind &self), so all non-Copy types need `.clone()`.
pub fn gen_lossy_binding_to_core_fields(typ: &TypeDef, core_import: &str) -> String {
    gen_lossy_binding_to_core_fields_inner(typ, core_import, false)
}

/// Same as `gen_lossy_binding_to_core_fields` but declares `core_self` as mutable.
pub fn gen_lossy_binding_to_core_fields_mut(typ: &TypeDef, core_import: &str) -> String {
    gen_lossy_binding_to_core_fields_inner(typ, core_import, true)
}

fn gen_lossy_binding_to_core_fields_inner(typ: &TypeDef, core_import: &str, needs_mut: bool) -> String {
    let core_path = crate::conversions::core_type_path(typ, core_import);
    let mut_kw = if needs_mut { "mut " } else { "" };
    let mut out = format!("let {mut_kw}core_self = {core_path} {{\n");
    for field in &typ.fields {
        let name = &field.name;
        if field.sanitized {
            writeln!(out, "            {name}: Default::default(),").ok();
        } else {
            let expr = match &field.ty {
                TypeRef::Primitive(_) => format!("self.{name}"),
                TypeRef::Duration => {
                    if field.optional {
                        format!("self.{name}.map(std::time::Duration::from_secs)")
                    } else {
                        format!("std::time::Duration::from_millis(self.{name})")
                    }
                }
                TypeRef::String | TypeRef::Char | TypeRef::Bytes => format!("self.{name}.clone()"),
                TypeRef::Path => {
                    if field.optional {
                        format!("self.{name}.clone().map(Into::into)")
                    } else {
                        format!("self.{name}.clone().into()")
                    }
                }
                TypeRef::Named(_) => {
                    if field.optional {
                        format!("self.{name}.clone().map(Into::into)")
                    } else {
                        format!("self.{name}.clone().into()")
                    }
                }
                TypeRef::Vec(inner) => match inner.as_ref() {
                    TypeRef::Named(_) => {
                        if field.optional {
                            // Option<Vec<Named(T)>>: map over the Option, then convert each element
                            format!("self.{name}.clone().map(|v| v.into_iter().map(Into::into).collect())")
                        } else {
                            format!("self.{name}.clone().into_iter().map(Into::into).collect()")
                        }
                    }
                    _ => format!("self.{name}.clone()"),
                },
                TypeRef::Optional(inner) => match inner.as_ref() {
                    TypeRef::Named(_) => {
                        format!("self.{name}.clone().map(Into::into)")
                    }
                    TypeRef::Vec(vi) if matches!(vi.as_ref(), TypeRef::Named(_)) => {
                        format!("self.{name}.clone().map(|v| v.into_iter().map(Into::into).collect())")
                    }
                    _ => format!("self.{name}.clone()"),
                },
                TypeRef::Map(_, v) => match v.as_ref() {
                    TypeRef::Json => {
                        // HashMap<String, String> (binding) → HashMap<String, Value> (core)
                        if field.optional {
                            format!(
                                "self.{name}.clone().map(|m| m.into_iter().map(|(k, v)| \
                                 (k, serde_json::from_str(&v).unwrap_or(serde_json::Value::String(v)))).collect())"
                            )
                        } else {
                            format!(
                                "self.{name}.clone().into_iter().map(|(k, v)| \
                                 (k, serde_json::from_str(&v).unwrap_or(serde_json::Value::String(v)))).collect()"
                            )
                        }
                    }
                    // Collect to handle HashMap↔BTreeMap conversion
                    _ => {
                        if field.optional {
                            format!("self.{name}.clone().map(|m| m.into_iter().collect())")
                        } else {
                            format!("self.{name}.clone().into_iter().collect()")
                        }
                    }
                },
                TypeRef::Unit => format!("self.{name}.clone()"),
                TypeRef::Json => {
                    // String (binding) → serde_json::Value (core)
                    if field.optional {
                        format!("self.{name}.as_ref().and_then(|s| serde_json::from_str(s).ok())")
                    } else {
                        format!("serde_json::from_str(&self.{name}).unwrap_or_default()")
                    }
                }
            };
            // Newtype wrapping: when the field was resolved from a newtype (e.g. NodeIndex → u32),
            // re-wrap the binding value into the newtype for the core struct literal.
            // When `optional=true` and `ty` is a plain Primitive (not TypeRef::Optional), the core
            // field is actually `Option<NewtypeT>`, so we must use `.map(NewtypeT)` not `NewtypeT(...)`.
            let expr = if let Some(newtype_path) = &field.newtype_wrapper {
                match &field.ty {
                    TypeRef::Optional(_) => format!("({expr}).map({newtype_path})"),
                    TypeRef::Vec(_) => format!("({expr}).into_iter().map({newtype_path}).collect()"),
                    _ if field.optional => format!("({expr}).map({newtype_path})"),
                    _ => format!("{newtype_path}({expr})"),
                }
            } else {
                expr
            };
            writeln!(out, "            {name}: {expr},").ok();
        }
    }
    // Use ..Default::default() to fill cfg-gated fields stripped from the IR
    if typ.has_stripped_cfg_fields {
        out.push_str("            ..Default::default()\n");
    }
    out.push_str("        };\n        ");
    out
}

/// Generate the body for an async call, unified across methods, static methods, and free functions.
///
/// - `core_call`: the expression to await, e.g. `inner.method(args)` or `CoreType::fn(args)`.
///   For Pyo3FutureIntoPy opaque methods this should reference `inner` (the Arc clone);
///   for all other patterns it may reference `self.inner` or a static call expression.
/// - `cfg`: binding configuration (determines which async pattern to emit)
/// - `has_error`: whether the core call returns a `Result`
/// - `return_wrap`: expression to produce the binding return value from `result`,
///   e.g. `"result"` or `"TypeName::from(result)"`
///
/// - `is_opaque`: whether the binding type is Arc-wrapped (affects TokioBlockOn wrapping)
/// - `inner_clone_line`: optional statement emitted before the pattern-specific body,
///   e.g. `"let inner = self.inner.clone();\n        "` for opaque instance methods, or `""`.
///   Required when `core_call` references `inner` (Pyo3FutureIntoPy opaque case).
pub fn gen_async_body(
    core_call: &str,
    cfg: &RustBindingConfig,
    has_error: bool,
    return_wrap: &str,
    is_opaque: bool,
    inner_clone_line: &str,
    is_unit_return: bool,
) -> String {
    let pattern_body = match cfg.async_pattern {
        AsyncPattern::Pyo3FutureIntoPy => {
            let result_handling = if has_error {
                format!(
                    "let result = {core_call}.await\n            \
                     .map_err(|e| PyErr::new::<PyRuntimeError, _>(e.to_string()))?;"
                )
            } else if is_unit_return {
                format!("{core_call}.await;")
            } else {
                format!("let result = {core_call}.await;")
            };
            let ok_expr = if is_unit_return && !has_error {
                "()"
            } else {
                return_wrap
            };
            format!(
                "pyo3_async_runtimes::tokio::future_into_py(py, async move {{\n            \
                 {result_handling}\n            \
                 Ok({ok_expr})\n        }})"
            )
        }
        AsyncPattern::WasmNativeAsync => {
            let result_handling = if has_error {
                format!(
                    "let result = {core_call}.await\n        \
                     .map_err(|e| JsValue::from_str(&e.to_string()))?;"
                )
            } else if is_unit_return {
                format!("{core_call}.await;")
            } else {
                format!("let result = {core_call}.await;")
            };
            let ok_expr = if is_unit_return && !has_error {
                "()"
            } else {
                return_wrap
            };
            format!(
                "{result_handling}\n        \
                 Ok({ok_expr})"
            )
        }
        AsyncPattern::NapiNativeAsync => {
            let result_handling = if has_error {
                format!(
                    "let result = {core_call}.await\n            \
                     .map_err(|e| napi::Error::new(napi::Status::GenericFailure, e.to_string()))?;"
                )
            } else if is_unit_return {
                format!("{core_call}.await;")
            } else {
                format!("let result = {core_call}.await;")
            };
            if !has_error && !is_unit_return {
                // No error type: return value directly without Ok() wrapper
                format!(
                    "{result_handling}\n            \
                     {return_wrap}"
                )
            } else {
                let ok_expr = if is_unit_return && !has_error {
                    "()"
                } else {
                    return_wrap
                };
                format!(
                    "{result_handling}\n            \
                     Ok({ok_expr})"
                )
            }
        }
        AsyncPattern::TokioBlockOn => {
            if has_error {
                if is_opaque {
                    format!(
                        "let rt = tokio::runtime::Runtime::new()?;\n        \
                         let result = rt.block_on(async {{ {core_call}.await.map_err(|e| e.into()) }})?;\n        \
                         {return_wrap}"
                    )
                } else {
                    format!(
                        "let rt = tokio::runtime::Runtime::new()?;\n        \
                         rt.block_on(async {{ {core_call}.await.map_err(|e| e.into()) }})"
                    )
                }
            } else if is_opaque {
                if is_unit_return {
                    format!(
                        "let rt = tokio::runtime::Runtime::new()?;\n        \
                         rt.block_on(async {{ {core_call}.await }});"
                    )
                } else {
                    format!(
                        "let rt = tokio::runtime::Runtime::new()?;\n        \
                         let result = rt.block_on(async {{ {core_call}.await }});\n        \
                         {return_wrap}"
                    )
                }
            } else {
                format!(
                    "let rt = tokio::runtime::Runtime::new()?;\n        \
                     rt.block_on(async {{ {core_call}.await }})"
                )
            }
        }
        AsyncPattern::None => "todo!(\"async not supported by backend\")".to_string(),
    };
    if inner_clone_line.is_empty() {
        pattern_body
    } else {
        format!("{inner_clone_line}{pattern_body}")
    }
}

/// Generate a compilable body for functions that can't be auto-delegated.
/// Returns a default value or error instead of `todo!()` which would panic.
pub fn gen_unimplemented_body(
    return_type: &TypeRef,
    fn_name: &str,
    has_error: bool,
    cfg: &RustBindingConfig,
    params: &[ParamDef],
) -> String {
    // Suppress unused_variables by binding all params to `_`
    let suppress = if params.is_empty() {
        String::new()
    } else {
        let names: Vec<&str> = params.iter().map(|p| p.name.as_str()).collect();
        if names.len() == 1 {
            format!("let _ = {};\n        ", names[0])
        } else {
            format!("let _ = ({});\n        ", names.join(", "))
        }
    };
    let err_msg = format!("Not implemented: {fn_name}");
    let body = if has_error {
        // Backend-specific error return
        match cfg.async_pattern {
            AsyncPattern::Pyo3FutureIntoPy => {
                format!("Err(pyo3::exceptions::PyNotImplementedError::new_err(\"{err_msg}\"))")
            }
            AsyncPattern::NapiNativeAsync => {
                format!("Err(napi::Error::new(napi::Status::GenericFailure, \"{err_msg}\"))")
            }
            AsyncPattern::WasmNativeAsync => {
                format!("Err(JsValue::from_str(\"{err_msg}\"))")
            }
            _ => format!("Err(\"{err_msg}\".to_string())"),
        }
    } else {
        // Return type-appropriate default
        match return_type {
            TypeRef::Unit => "()".to_string(),
            TypeRef::String | TypeRef::Char | TypeRef::Path => format!("String::from(\"[unimplemented: {fn_name}]\")"),
            TypeRef::Bytes => "Vec::new()".to_string(),
            TypeRef::Primitive(p) => match p {
                alef_core::ir::PrimitiveType::Bool => "false".to_string(),
                _ => "0".to_string(),
            },
            TypeRef::Optional(_) => "None".to_string(),
            TypeRef::Vec(_) => "Vec::new()".to_string(),
            TypeRef::Map(_, _) => "Default::default()".to_string(),
            TypeRef::Duration => "0".to_string(),
            TypeRef::Named(_) | TypeRef::Json => {
                // Named return without error type: can't return Err.
                // Emit compile_error so this is caught at build time rather than panicking at runtime.
                format!(
                    "compile_error!(\"alef: {fn_name} returns a Named/Json type but has no error variant — cannot auto-delegate\")"
                )
            }
        }
    };
    format!("{suppress}{body}")
}