//! Proc macro ABI

use proc_macro::bridge;
use proc_macro_api::ProcMacroKind;

use libloading::Library;

use crate::{dylib::LoadProcMacroDylibError, ProcMacroSrvSpan};

pub(crate) struct ProcMacros {
    exported_macros: Vec<bridge::client::ProcMacro>,
}

impl From<bridge::PanicMessage> for crate::PanicMessage {
    fn from(p: bridge::PanicMessage) -> Self {
        Self { message: p.as_str().map(|s| s.to_owned()) }
    }
}

impl ProcMacros {
    /// Load a new ABI.
    ///
    /// # Arguments
    ///
    /// *`lib` - The dynamic library containing the macro implementations
    /// *`symbol_name` - The symbol name the macros can be found attributes
    /// *`info` - RustCInfo about the compiler that was used to compile the
    ///           macro crate. This is the information we use to figure out
    ///           which ABI to return
    pub(crate) fn from_lib(
        lib: &Library,
        symbol_name: String,
        version_string: &str,
    ) -> Result<ProcMacros, LoadProcMacroDylibError> {
        if version_string == crate::RUSTC_VERSION_STRING {
            let macros =
                unsafe { lib.get::<&&[bridge::client::ProcMacro]>(symbol_name.as_bytes()) }?;

            return Ok(Self { exported_macros: macros.to_vec() });
        }
        Err(LoadProcMacroDylibError::AbiMismatch(version_string.to_owned()))
    }

    pub(crate) fn expand<S: ProcMacroSrvSpan>(
        &self,
        macro_name: &str,
        macro_body: tt::Subtree<S>,
        attributes: Option<tt::Subtree<S>>,
        def_site: S,
        call_site: S,
        mixed_site: S,
    ) -> Result<tt::Subtree<S>, crate::PanicMessage> {
        let parsed_body = crate::server_impl::TokenStream::with_subtree(macro_body);

        let parsed_attributes = attributes
            .map_or_else(crate::server_impl::TokenStream::new, |attr| {
                crate::server_impl::TokenStream::with_subtree(attr)
            });

        for proc_macro in &self.exported_macros {
            match proc_macro {
                bridge::client::ProcMacro::CustomDerive { trait_name, client, .. }
                    if *trait_name == macro_name =>
                {
                    let res = client.run(
                        &bridge::server::SameThread,
                        S::make_server(call_site, def_site, mixed_site),
                        parsed_body,
                        cfg!(debug_assertions),
                    );
                    return res
                        .map(|it| it.into_subtree(call_site))
                        .map_err(crate::PanicMessage::from);
                }
                bridge::client::ProcMacro::Bang { name, client } if *name == macro_name => {
                    let res = client.run(
                        &bridge::server::SameThread,
                        S::make_server(call_site, def_site, mixed_site),
                        parsed_body,
                        cfg!(debug_assertions),
                    );
                    return res
                        .map(|it| it.into_subtree(call_site))
                        .map_err(crate::PanicMessage::from);
                }
                bridge::client::ProcMacro::Attr { name, client } if *name == macro_name => {
                    let res = client.run(
                        &bridge::server::SameThread,
                        S::make_server(call_site, def_site, mixed_site),
                        parsed_attributes,
                        parsed_body,
                        cfg!(debug_assertions),
                    );
                    return res
                        .map(|it| it.into_subtree(call_site))
                        .map_err(crate::PanicMessage::from);
                }
                _ => continue,
            }
        }

        Err(bridge::PanicMessage::String(format!("proc-macro `{macro_name}` is missing")).into())
    }

    pub(crate) fn list_macros(&self) -> Vec<(String, ProcMacroKind)> {
        self.exported_macros
            .iter()
            .map(|proc_macro| match proc_macro {
                bridge::client::ProcMacro::CustomDerive { trait_name, .. } => {
                    (trait_name.to_string(), ProcMacroKind::CustomDerive)
                }
                bridge::client::ProcMacro::Bang { name, .. } => {
                    (name.to_string(), ProcMacroKind::Bang)
                }
                bridge::client::ProcMacro::Attr { name, .. } => {
                    (name.to_string(), ProcMacroKind::Attr)
                }
            })
            .collect()
    }
}
