use std::iter;
use proc_macro::TokenStream;
use quote::quote;
use darling::FromField;

/// (**Required** Callback) Called when the plugin is being uninitialized
///
///### Example
///
/// ```rust
///use panda::PluginHandle;
///
/// #[panda::init]
/// fn start(_: &mut PluginHandle) {
///     println!("Plugin started up!");
/// }
/// ```
#[proc_macro_attribute]
pub fn init(_: TokenStream, function: TokenStream) -> TokenStream {
    let func = syn::parse_macro_input!(function as syn::ItemFn);

    let args = if func.sig.inputs.is_empty() {
        None
    } else {
        Some(quote!( unsafe { &mut *plugin } ))
    };

    let func_name = &func.sig.ident;

    quote!(
        mod __panda_internal {
            use super::*;

            #[no_mangle]
            unsafe extern "C" fn init_plugin(plugin: *mut ::panda::PluginHandle) {
                for cb in ::panda::inventory::iter::<::panda::Callback> {
                    ::panda::sys::panda_register_callback(plugin as _, cb.cb_type, ::core::mem::transmute(cb.fn_pointer));
                }

                for cb in ::panda::inventory::iter::<::panda::PPPCallbackSetup> {
                    cb.0();
                }

                #func_name(#args);
            }
            
            #[no_mangle]
            unsafe extern "C" fn uninit_plugin(plugin: *mut ::panda::PluginHandle) {
                for cb in ::panda::inventory::iter::<::panda::UninitCallback> {
                    cb.0(unsafe { &mut *plugin });
                }
            }
        }

        #func
    ).into()
}

/// (Callback) Called when the plugin is being uninitialized
#[proc_macro_attribute]
pub fn uninit(_: TokenStream, function: TokenStream) -> TokenStream {
    let func = syn::parse_macro_input!(function as syn::ItemFn);
    let func_name = &func.sig.ident;

    quote!(
        ::panda::inventory::submit! {
            #![crate = ::panda]
            ::panda::UninitCallback(#func_name)
        }

        #func
    ).into()
}

#[derive(FromField)]
#[darling(attributes(arg))]
struct DeriveArgs {
    #[darling(default)]
    about: Option<String>,
    #[darling(default)]
    default: Option<syn::Lit>,
    #[darling(default)]
    required: bool,
    ident: Option<syn::Ident>,
    ty: syn::Type,
}

fn derive_args_to_mappings(
    DeriveArgs { about, default, ident, ty, required }: DeriveArgs
) -> (syn::Stmt, syn::Ident) {
    let name = &ident;
    let default = if let Some(default) = default {
        match default {
            syn::Lit::Str(string) => quote!(::std::string::String::from(#string)),
            default => quote!(#default)
        }
    } else {
        quote!(Default::default())
    };
    let about = about.unwrap_or_default();
    (
        syn::parse_quote!(
            let #name = <#ty as ::panda::panda_arg::GetPandaArg>::get_panda_arg(
                __args_ptr,
                stringify!(#name),
                #default,
                #about,
                #required
            );
        ),
        ident.unwrap()
    )
}

fn get_field_statements(fields: &syn::Fields) -> Result<(Vec<syn::Stmt>, Vec<syn::Ident>), darling::Error> {
    Ok(fields
        .iter()
        .map(DeriveArgs::from_field)
        .collect::<Result<Vec<_>, _>>()?
        .into_iter()
        .map(derive_args_to_mappings)
        .unzip())
}

fn get_name(attrs: &[syn::Attribute]) -> Option<String> {
    attrs.iter()
        .find(|attr| attr.path.get_ident().map(|x| x.to_string() == "name").unwrap_or(false))
        .map(|attr| attr.parse_meta().ok())
        .flatten()
        .map(|meta| if let syn::Meta::NameValue(syn::MetaNameValue { lit: syn::Lit::Str(s), .. }) = meta {
            Some(s.value())
        } else {
            None
        })
        .flatten()
}

#[proc_macro_derive(PandaArgs, attributes(name, arg))]
pub fn derive_panda_args(input: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(input as syn::ItemStruct);

    let name = match get_name(&input.attrs) {
        Some(name) => name,
        None => return quote!(compiler_error!("Missing plugin name, add `#[name = ...]` above struct")).into()
    };

    let ident = &input.ident;

    match get_field_statements(&input.fields) {
        Ok((statements, fields)) => {
            let format_args =
                iter::repeat("{}={}")
                    .take(statements.len())
                    .collect::<Vec<_>>()
                    .join(",");
            quote!(
                impl ::panda::PandaArgs for #ident {
                    fn from_panda_args() -> Self {
                        let name = ::std::ffi::CString::new(#name).unwrap();
                        
                        unsafe {
                            let __args_ptr = ::panda::sys::panda_get_args(name.as_ptr());

                            #(
                                #statements
                            )*
                            
                            ::panda::sys::panda_free_args(__args_ptr);

                            Self {
                                #(#fields),*
                            }
                        }
                    }

                    fn to_panda_args_str(&self) -> ::std::string::String {
                        format!(
                            concat!(#name, ":", #format_args),
                            #(
                                stringify!(#fields), self.#fields
                            ),*
                       )
                    }
                }
            )
        },
        Err(err) => err.write_errors()
    }.into()
}

struct Idents(syn::Ident, syn::Ident);

impl syn::parse::Parse for Idents {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        Ok(Idents(
            input.parse()?,
            input.parse()?
        ))
    }
}

fn get_cfg_attrs(func: &syn::ItemFn) -> Vec<syn::Attribute> {
    func.attrs.iter()
        .filter(|attr| attr.path.get_ident().map(|x| x.to_string() == "cfg").unwrap_or(false))
        .map(|attr| attr.clone())
        .collect()
}

macro_rules! define_callback_attributes {
    ($(
        $($doc:literal)*
        ($attr_name:ident, $const_name:ident, ($($arg:ty),*) $(-> $ret:ty)?)
    ),*) => {
        $(
            doc_comment::doc_comment!{
                concat!(
                    "(Callback) ",
                    $($doc, "\n",)*
                    "\n\nCallback arguments: (",
                    $("`", stringify!($arg), "`, ",)*
                    ")\n### Example\n```rust\nuse panda::prelude::*;\n\n#[panda::",
                    stringify!($attr_name),
                    "]\nfn callback(",
                    $("_: ", stringify!($arg), ", ", )* ")",
                    $(" -> ", stringify!($ret),)?
                    " {\n    // do stuff\n}\n```"),
                #[proc_macro_attribute]
                pub fn $attr_name(_: TokenStream, function: TokenStream) -> TokenStream {
                    let mut function = syn::parse_macro_input!(function as syn::ItemFn);
                    function.sig.abi = Some(syn::parse_quote!(extern "C"));
                    let func = &function.sig.ident;
                    let cfgs = crate::get_cfg_attrs(&function);

                    quote!(
                        #(
                            #cfgs
                         )*
                        const _: fn() = || {
                            use ::panda::sys::*;
                            fn assert_callback_arg_types(_ : extern "C" fn($($arg),*) $(-> $ret)?) {}

                            assert_callback_arg_types(#func);
                        };

                        ::panda::inventory::submit! {
                            #![crate = ::panda]
                            ::panda::Callback::new(
                                ::panda::sys::$const_name,
                                #func as *const ()
                            )
                        }

                        #function
                    ).into()
                }
            }
        )*
    }
}

macro_rules! define_syscalls_callbacks {
    ($(
        $($doc:literal)*
        ($attr_name:ident, $cb_name:ident, ($($arg_name:ident : $arg:ty),*))
    ),*) => {
        $(
            doc_comment::doc_comment!{
                concat!("(Callback) ", $($doc, "\n",)* "\n\nCallback arguments: (`&mut CPUState`, `target_ulong`", $(", `", stringify!($arg), "`",)* ")\n### Example\n```rust\nuse panda::prelude::*;\n\n#[panda::", stringify!($attr_name),"]\nfn callback(cpu: &mut CPUState, pc: target_ulong", $(", _: ", stringify!($arg), )* ") {\n    // do stuff\n}\n```"),
                #[proc_macro_attribute]
                pub fn $attr_name(_: TokenStream, function: TokenStream) -> TokenStream {
                    let mut function = syn::parse_macro_input!(function as syn::ItemFn);
                    function.sig.abi = Some(syn::parse_quote!(extern "C"));
                    let func = &function.sig.ident;
                    let cfgs = crate::get_cfg_attrs(&function);

                    quote!(
                        #(
                            #cfgs
                         )*
                        ::panda::inventory::submit! {
                            #![crate = ::panda]
                            ::panda::PPPCallbackSetup(
                                || {
                                    ::panda::plugins::syscalls2::SYSCALLS.$cb_name(#func);
                                }
                            )
                        }

                        #function
                    ).into()
                }
            }
        )*

        /// For internal use only
        #[proc_macro]
        pub fn generate_syscalls_callbacks(_: TokenStream) -> TokenStream {
            quote!(
                plugin_import!{
                    static SYSCALLS: Syscalls2 = extern "syscalls2" {
                        callbacks {
                            $(
                                fn $attr_name(
                                    cpu: &mut crate::sys::CPUState,
                                    pc: crate::sys::target_ulong,
                                    $($arg_name : $arg),*
                                );
                            )*
                            //fn on_sys_read_enter(fd: target_ulong, buf: target_ptr_t, count: target_ulong);
                            //fn on_sys_write_enter(fd: target_ulong, buf: target_ptr_t, count: target_ulong);
                        }
                    };
                }
            ).into()
        }
    };
}

macro_rules! define_hooks2_callbacks {
    ($(
        $($doc:literal)*
        fn($cb_name:ident) $attr_name:ident ($($arg_name:ident : $arg:ty),* $(,)?);
    )*) => {
        $(
            doc_comment::doc_comment!{
                concat!("(Callback) ", $($doc, "\n",)* "\n\nCallback arguments: ("$(, "`", stringify!($arg), "`")*, ")\n### Example\n```rust\nuse panda::prelude::*;\n\n#[panda::", stringify!($attr_name),"]\nfn callback(", $(", _: ", stringify!($arg), )* ") {\n    // do stuff\n}\n```"),
                #[proc_macro_attribute]
                pub fn $attr_name(_: TokenStream, function: TokenStream) -> TokenStream {
                    let mut function = syn::parse_macro_input!(function as syn::ItemFn);
                    function.sig.abi = Some(syn::parse_quote!(extern "C"));
                    let func = &function.sig.ident;
                    let cfgs = crate::get_cfg_attrs(&function);

                    quote!(
                        #(
                            #cfgs
                         )*
                        ::panda::inventory::submit! {
                            #![crate = ::panda]
                            ::panda::PPPCallbackSetup(
                                || {
                                    ::panda::plugins::hooks2::HOOKS.$cb_name(#func);
                                }
                            )
                        }

                        #function
                    ).into()
                }
            }
        )*

        /// For internal use only
        #[proc_macro]
        pub fn generate_hooks2_callbacks(_: TokenStream) -> TokenStream {
            quote!(

                plugin_import!{
                    static HOOKS: Hooks2 = extern "hooks2" {
                        callbacks {
                            $(
                                fn $attr_name(
                                    $($arg_name : $arg),*
                                );
                            )*
                        }
                    };
                }
            ).into()
        }
    };
}

include!("base_callbacks.rs");
include!("syscalls.rs");
include!("hooks2.rs");