#![allow(dead_code)]

use proc_macro::TokenStream;
use quote::quote;
use syn::{DeriveInput, Ident, TypePath, parse_macro_input};

use crate::get_global_set;

/// Derive macro for `StructuralData`.
///
/// This marks a type as eligible for structured output (JSON / YAML / TOML / RON).
/// The type must also implement `serde::Serialize` — the generated `impl StructuralData`
/// will fail to compile if `Serialize` is not in scope or implemented.
///
/// Also registers the type name in the global `STRUCTURED_TYPES` registry so that
/// the `general_render` match arm is generated by `gen_program!()`.
pub(crate) fn derive_structural_data(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let type_name = input.ident;

    // Register in STRUCTURED_TYPES
    let type_name_str = type_name.to_string();
    get_global_set(&crate::STRUCTURED_TYPES)
        .lock()
        .unwrap()
        .insert(type_name_str);

    // Generate BOTH the sealed impl AND the StructuralData impl.
    // Users cannot implement StructuralDataSealed manually (it's #[doc(hidden)]),
    // so the only way to get StructuralData is through this derive macro.
    let expanded = quote! {
        impl ::mingling::__private::StructuralDataSealed for #type_name {}
        impl ::mingling::__private::StructuralData for #type_name {}
    };

    expanded.into()
}

/// `pack_structural!` — like `pack!` but also marks the type as supporting
/// structured output via `StructuralData`.
///
/// # Syntax
///
/// ```rust,ignore
/// pack_structural!(Info = (String, i32));
/// ```
///
/// This is equivalent to:
/// ```rust,ignore
/// pack!(Info = (String, i32));
/// impl ::mingling::StructuralData for Info {}
/// ```
pub(crate) fn pack_structural(input: TokenStream) -> TokenStream {
    // Parse same input format as `pack!`
    let input_parsed = syn::parse_macro_input!(input as PackStructuralInput);
    let type_name = input_parsed.type_name;
    let inner_type = input_parsed.inner_type;
    let attrs = input_parsed.attrs;
    let program_path = crate::default_program_path();

    // Register in STRUCTURED_TYPES
    let type_name_str = type_name.to_string();
    get_global_set(&crate::STRUCTURED_TYPES)
        .lock()
        .unwrap()
        .insert(type_name_str);

    // Struct definition (with Serialize derive, same as pack! under general_renderer)
    #[cfg(not(feature = "general_renderer"))]
    let struct_def = quote! {
        #(#attrs)*
        pub struct #type_name {
            pub inner: #inner_type,
        }
    };

    #[cfg(feature = "general_renderer")]
    let struct_def = quote! {
        #(#attrs)*
        #[derive(serde::Serialize)]
        pub struct #type_name {
            pub inner: #inner_type,
        }
    };

    // Helper impls (same as pack!)
    let new_impl = quote! {
        impl #type_name {
            pub fn new(inner: #inner_type) -> Self {
                Self { inner }
            }
        }
    };

    let from_into_impl = quote! {
        impl From<#inner_type> for #type_name {
            fn from(inner: #inner_type) -> Self {
                Self::new(inner)
            }
        }
        impl From<#type_name> for #inner_type {
            fn from(wrapper: #type_name) -> #inner_type {
                wrapper.inner
            }
        }
    };

    let as_ref_impl = quote! {
        impl ::std::convert::AsRef<#inner_type> for #type_name {
            fn as_ref(&self) -> &#inner_type {
                &self.inner
            }
        }
        impl ::std::convert::AsMut<#inner_type> for #type_name {
            fn as_mut(&mut self) -> &mut #inner_type {
                &mut self.inner
            }
        }
    };

    let deref_impl = quote! {
        impl ::std::ops::Deref for #type_name {
            type Target = #inner_type;
            fn deref(&self) -> &Self::Target {
                &self.inner
            }
        }
        impl ::std::ops::DerefMut for #type_name {
            fn deref_mut(&mut self) -> &mut Self::Target {
                &mut self.inner
            }
        }
    };

    let default_impl = quote! {
        impl ::std::default::Default for #type_name
        where
            #inner_type: ::std::default::Default,
        {
            fn default() -> Self {
                Self::new(::std::default::Default::default())
            }
        }
    };

    let register_impl = quote! {
        ::mingling::macros::register_type!(#type_name);
    };

    // StructuralData impl + sealed + registration
    let structural_impl = quote! {
        impl ::mingling::__private::StructuralDataSealed for #type_name {}
        impl ::mingling::__private::StructuralData for #type_name {}
    };

    let expanded = quote! {
        #struct_def

        #new_impl
        #from_into_impl
        #as_ref_impl
        #deref_impl
        #default_impl
        #register_impl
        #structural_impl

        impl Into<::mingling::AnyOutput<#program_path>> for #type_name {
            fn into(self) -> ::mingling::AnyOutput<#program_path> {
                ::mingling::AnyOutput::new(self)
            }
        }

        impl Into<::mingling::ChainProcess<#program_path>> for #type_name {
            fn into(self) -> ::mingling::ChainProcess<#program_path> {
                ::mingling::AnyOutput::new(self).route_chain()
            }
        }

        impl ::mingling::Groupped<#program_path> for #type_name {
            fn member_id() -> #program_path {
                #program_path::#type_name
            }
        }
    };

    expanded.into()
}

/// Input for `pack_structural!` — same format as `pack!`.
struct PackStructuralInput {
    attrs: Vec<syn::Attribute>,
    type_name: Ident,
    inner_type: syn::Type,
}

impl syn::parse::Parse for PackStructuralInput {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let attrs = input.call(syn::Attribute::parse_outer)?;
        let type_name: Ident = input.parse()?;
        input.parse::<syn::Token![=]>()?;
        let inner_type: syn::Type = input.parse()?;
        Ok(PackStructuralInput {
            attrs,
            type_name,
            inner_type,
        })
    }
}

/// `group_structural!` — like `group!` but also marks the type as supporting
/// structured output via `StructuralData`.
///
/// # Syntax
///
/// ```rust,ignore
/// group_structural!(Info = (String, i32));
/// ```
///
/// This is equivalent to:
/// ```rust,ignore
/// group!(Info = (String, i32));
/// impl ::mingling::StructuralData for Info {}
/// ```
pub(crate) fn group_structural(input: TokenStream) -> TokenStream {

    // Parse the same input as group!
    let input_parsed = syn::parse_macro_input!(input as GroupStructuralInput);

    let is_aliased = matches!(&input_parsed, GroupStructuralInput::Aliased { .. });

    let (type_path, type_name, alias_stmt) = match &input_parsed {
        GroupStructuralInput::Plain(type_path) => {
            let name = type_path
                .path
                .segments
                .last()
                .expect("TypePath must have at least one segment")
                .ident
                .clone();
            (type_path.clone(), name, quote! {})
        }
        GroupStructuralInput::Aliased { alias, type_path } => {
            let alias_stmt = quote! {
                pub(crate) type #alias = #type_path;
            };
            (type_path.clone(), alias.clone(), alias_stmt)
        }
    };

    let type_name_str = type_name.to_string();

    // Register in STRUCTURED_TYPES
    get_global_set(&crate::STRUCTURED_TYPES)
        .lock()
        .unwrap()
        .insert(type_name_str);

    let program_path = crate::default_program_path();

    // Generate unique module name
    let segments: Vec<String> = type_path
        .path
        .segments
        .iter()
        .map(|seg| seg.ident.to_string().to_lowercase())
        .collect();
    let module_name = Ident::new(
        &format!("internal_group_{}", segments.join("_")),
        proc_macro2::Span::call_site(),
    );

    // Generate the appropriate `use` statement
    let type_use = if type_path.path.segments.len() > 1 {
        quote! { #[allow(unused_imports)] use #type_path; }
    } else {
        let ident = &type_name;
        quote! { #[allow(unused_imports)] use super::#ident; }
    };

    let alias_use = if is_aliased {
        quote! { use super::#type_name; }
    } else {
        quote! {}
    };

    let expanded = quote! {
        #alias_stmt
        #[allow(non_camel_case_types)]
        mod #module_name {
            use #program_path as __MinglingProgram;
            #type_use
            #alias_use

            impl ::mingling::Groupped<__MinglingProgram> for #type_name {
                fn member_id() -> __MinglingProgram {
                    __MinglingProgram::#type_name
                }
            }

            impl ::mingling::__private::StructuralDataSealed for #type_name {}
            impl ::mingling::__private::StructuralData for #type_name {}

            ::mingling::macros::register_type!(#type_name);
        }
    };

    expanded.into()
}

/// Input for `group_structural!` — same format as `group!`.
enum GroupStructuralInput {
    Plain(TypePath),
    Aliased { alias: Ident, type_path: TypePath },
}

impl syn::parse::Parse for GroupStructuralInput {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let fork = input.fork();
        let _first: Ident = fork.parse()?;
        if fork.peek(syn::Token![=]) {
            let alias: Ident = input.parse()?;
            let _eq: syn::Token![=] = input.parse()?;
            let type_path: TypePath = input.parse()?;
            Ok(GroupStructuralInput::Aliased { alias, type_path })
        } else {
            let type_path: TypePath = input.parse()?;
            Ok(GroupStructuralInput::Plain(type_path))
        }
    }
}