//LICENSE Portions Copyright 2019-2021 ZomboDB, LLC.
//LICENSE
//LICENSE Portions Copyright 2021-2023 Technology Concepts & Design, Inc.
//LICENSE
//LICENSE Portions Copyright 2023-2023 PgCentral Foundation, Inc. <contact@pgcentral.org>
//LICENSE
//LICENSE All rights reserved.
//LICENSE
//LICENSE Use of this source code is governed by the MIT license that can be found in the LICENSE file.
/*!

`#[derive(PostgresEnum)]` related macro expansion for Rust to SQL translation

> Like all of the [`sql_entity_graph`][crate::pgrx_sql_entity_graph] APIs, this is considered **internal**
to the `pgrx` framework and very subject to change between versions. While you may use this, please do it with caution.

*/
pub mod entity;

use crate::enrich::{ToEntityGraphTokens, ToRustCodeTokens};
use crate::{CodeEnrichment, ToSqlConfig};
use proc_macro2::{Span, TokenStream as TokenStream2};
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::{DeriveInput, Generics, Ident, ItemEnum, Token};

/// A parsed `#[derive(PostgresEnum)]` item.
///
/// It should be used with [`syn::parse::Parse`] functions.
///
/// Using [`quote::ToTokens`] will output the declaration for a `pgrx::datum::pgrx_sql_entity_graph::PostgresEnumEntity`.
///
/// ```rust
/// use syn::{Macro, parse::Parse, parse_quote, parse};
/// use quote::{quote, ToTokens};
/// use pgrx_sql_entity_graph::PostgresEnum;
///
/// # fn main() -> eyre::Result<()> {
/// use pgrx_sql_entity_graph::CodeEnrichment;
/// let parsed: CodeEnrichment<PostgresEnum> = parse_quote! {
///     #[derive(PostgresEnum)]
///     enum Demo {
///         Example,
///     }
/// };
/// let sql_graph_entity_tokens = parsed.to_token_stream();
/// # Ok(())
/// # }
/// ```
#[derive(Debug, Clone)]
pub struct PostgresEnum {
    name: Ident,
    generics: Generics,
    variants: Punctuated<syn::Variant, Token![,]>,
    to_sql_config: ToSqlConfig,
}

impl PostgresEnum {
    pub fn new(
        name: Ident,
        generics: Generics,
        variants: Punctuated<syn::Variant, Token![,]>,
        to_sql_config: ToSqlConfig,
    ) -> Result<CodeEnrichment<Self>, syn::Error> {
        if !to_sql_config.overrides_default() {
            crate::ident_is_acceptable_to_postgres(&name)?;
        }

        Ok(CodeEnrichment(Self { name, generics, variants, to_sql_config }))
    }

    pub fn from_derive_input(
        derive_input: DeriveInput,
    ) -> Result<CodeEnrichment<Self>, syn::Error> {
        let to_sql_config =
            ToSqlConfig::from_attributes(derive_input.attrs.as_slice())?.unwrap_or_default();
        let data_enum = match derive_input.data {
            syn::Data::Enum(data_enum) => data_enum,
            syn::Data::Union(_) | syn::Data::Struct(_) => {
                return Err(syn::Error::new(derive_input.ident.span(), "expected enum"))
            }
        };
        Self::new(derive_input.ident, derive_input.generics, data_enum.variants, to_sql_config)
    }
}

impl ToEntityGraphTokens for PostgresEnum {
    fn to_entity_graph_tokens(&self) -> TokenStream2 {
        // It's important we remap all lifetimes we spot to `'static` so they can be used during inventory submission.
        let name = self.name.clone();
        let mut static_generics = self.generics.clone();
        static_generics.params = static_generics
            .params
            .clone()
            .into_iter()
            .flat_map(|param| match param {
                item @ syn::GenericParam::Type(_) | item @ syn::GenericParam::Const(_) => {
                    Some(item)
                }
                syn::GenericParam::Lifetime(mut lifetime) => {
                    lifetime.lifetime.ident = Ident::new("static", Span::call_site());
                    Some(syn::GenericParam::Lifetime(lifetime))
                }
            })
            .collect();
        let mut staticless_generics = self.generics.clone();
        staticless_generics.params = static_generics
            .params
            .clone()
            .into_iter()
            .flat_map(|param| match param {
                item @ syn::GenericParam::Type(_) | item @ syn::GenericParam::Const(_) => {
                    Some(item)
                }
                syn::GenericParam::Lifetime(_) => None,
            })
            .collect();
        let (staticless_impl_generics, _staticless_ty_generics, _staticless_where_clauses) =
            staticless_generics.split_for_impl();
        let (_static_impl_generics, static_ty_generics, static_where_clauses) =
            static_generics.split_for_impl();

        let variants = self.variants.iter().map(|variant| variant.ident.clone());
        let sql_graph_entity_fn_name =
            syn::Ident::new(&format!("__pgrx_internals_enum_{}", name), Span::call_site());

        let to_sql_config = &self.to_sql_config;

        quote! {
            unsafe impl #staticless_impl_generics ::pgrx::pgrx_sql_entity_graph::metadata::SqlTranslatable for #name #static_ty_generics #static_where_clauses {
                fn argument_sql() -> core::result::Result<::pgrx::pgrx_sql_entity_graph::metadata::SqlMapping, ::pgrx::pgrx_sql_entity_graph::metadata::ArgumentError> {
                    Ok(::pgrx::pgrx_sql_entity_graph::metadata::SqlMapping::As(String::from(stringify!(#name))))
                }

                fn return_sql() -> core::result::Result<::pgrx::pgrx_sql_entity_graph::metadata::Returns, ::pgrx::pgrx_sql_entity_graph::metadata::ReturnsError> {
                    Ok(::pgrx::pgrx_sql_entity_graph::metadata::Returns::One(::pgrx::pgrx_sql_entity_graph::metadata::SqlMapping::As(String::from(stringify!(#name)))))
                }
            }

            #[no_mangle]
            #[doc(hidden)]
            #[allow(unknown_lints, clippy::no_mangle_with_rust_abi)]
            pub extern "Rust" fn  #sql_graph_entity_fn_name() -> ::pgrx::pgrx_sql_entity_graph::SqlGraphEntity {
                extern crate alloc;
                use alloc::vec::Vec;
                use alloc::vec;
                use ::pgrx::datum::WithTypeIds;

                let mut mappings = Default::default();
                <#name #static_ty_generics as ::pgrx::datum::WithTypeIds>::register_with_refs(&mut mappings, stringify!(#name).to_string());
                ::pgrx::datum::WithSizedTypeIds::<#name #static_ty_generics>::register_sized_with_refs(&mut mappings, stringify!(#name).to_string());
                ::pgrx::datum::WithArrayTypeIds::<#name #static_ty_generics>::register_array_with_refs(&mut mappings, stringify!(#name).to_string());
                ::pgrx::datum::WithVarlenaTypeIds::<#name #static_ty_generics>::register_varlena_with_refs(&mut mappings, stringify!(#name).to_string());

                let submission = ::pgrx::pgrx_sql_entity_graph::PostgresEnumEntity {
                    name: stringify!(#name),
                    file: file!(),
                    line: line!(),
                    module_path: module_path!(),
                    full_path: core::any::type_name::<#name #static_ty_generics>(),
                    mappings: mappings.into_iter().collect(),
                    variants: vec![ #(  stringify!(#variants)  ),* ],
                    to_sql_config: #to_sql_config,
                };
                ::pgrx::pgrx_sql_entity_graph::SqlGraphEntity::Enum(submission)
            }
        }
    }
}

impl ToRustCodeTokens for PostgresEnum {}

impl Parse for CodeEnrichment<PostgresEnum> {
    fn parse(input: ParseStream) -> Result<Self, syn::Error> {
        let parsed: ItemEnum = input.parse()?;
        let to_sql_config =
            ToSqlConfig::from_attributes(parsed.attrs.as_slice())?.unwrap_or_default();
        PostgresEnum::new(parsed.ident, parsed.generics, parsed.variants, to_sql_config)
    }
}