// Copyright 2020 ZomboDB, LLC <zombodb@gmail.com>. All rights reserved. Use of this source code is
// governed by the MIT license that can be found in the LICENSE file.

extern crate proc_macro;

mod rewriter;

use pgx_utils::*;
use proc_macro::TokenStream;
use proc_macro2::{Ident, Span};
use quote::{quote, quote_spanned};
use rewriter::*;
use std::collections::HashSet;
use syn::export::{ToTokens, TokenStream2};
use syn::spanned::Spanned;
use syn::{parse_macro_input, Attribute, Data, DeriveInput, Item, ItemFn};

/// Declare a function as `#[pg_guard]` to indcate that it is called from a Postgres `extern "C"`
/// function so that Rust `panic!()`s (and Postgres `elog(ERROR)`s) will be properly handled by `pgx`
#[proc_macro_attribute]
pub fn pg_guard(_attr: TokenStream, item: TokenStream) -> TokenStream {
    // get a usable token stream
    let ast = parse_macro_input!(item as syn::Item);

    let rewriter = PgGuardRewriter::new();

    match ast {
        // this is for processing the members of extern "C" { } blocks
        // functions inside the block get wrapped as public, top-level unsafe functions that are not "extern"
        Item::ForeignMod(block) => rewriter.extern_block(block).into(),

        // process top-level functions
        // these functions get wrapped as public extern "C" functions with #[no_mangle] so they
        // can also be called from C code
        Item::Fn(func) => rewriter.item_fn(func, false, false, false).0.into(),
        _ => {
            panic!("#[pg_guard] can only be applied to extern \"C\" blocks and top-level functions")
        }
    }
}

/// `#[pg_test]` functions are test functions (akin to `#[test]`), but they run in-process inside
/// Postgres during `cargo pgx test`.
#[proc_macro_attribute]
pub fn pg_test(attr: TokenStream, item: TokenStream) -> TokenStream {
    let mut stream = proc_macro2::TokenStream::new();
    let args = parse_extern_attributes(TokenStream2::from(attr.clone()));

    let mut expected_error = None;
    args.into_iter().for_each(|v| {
        if let ExternArgs::Error(message) = v {
            expected_error = Some(message)
        }
    });

    stream.extend(proc_macro2::TokenStream::from(pg_extern(
        attr,
        item.clone(),
    )));

    let expected_error = match expected_error {
        Some(msg) => quote! {Some(#msg)},
        None => quote! {None},
    };

    let ast = parse_macro_input!(item as syn::Item);
    match ast {
        Item::Fn(func) => {
            let sql_funcname = func.sig.ident.to_string();
            let test_func_name =
                Ident::new(&format!("pg_{}", func.sig.ident.to_string()), func.span());

            let attributes = func.attrs;
            let mut att_stream = proc_macro2::TokenStream::new();

            for a in attributes.iter() {
                let as_str = a.tokens.to_token_stream().to_string();
                att_stream.extend(quote! {
                    options.push(#as_str);
                });
            }

            stream.extend(quote! {
                #[test]
                fn #test_func_name() {
                    let mut options = Vec::new();
                    #att_stream

                    crate::pg_test::setup(options);
                    pgx_tests::run_test(#sql_funcname, #expected_error, crate::pg_test::postgresql_conf_options())
                }
            });
        }

        _ => panic!("#[pg_test] can only be applied to top-level functions"),
    }

    stream.into()
}

/// Associated macro for `#[pg_test]` to provide context back to your test framework to indicate
/// that the test system is being initialized
#[proc_macro_attribute]
pub fn initialize(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Declare a function as `#[pg_operator]` to indicate that it represents a Postgres operator
/// `cargo pgx schema` will automatically generate the underlying SQL
#[proc_macro_attribute]
pub fn pg_operator(attr: TokenStream, item: TokenStream) -> TokenStream {
    pg_extern(attr, item)
}

/// Used with `#[pg_operator]`.  1 value which is the operator name itself
#[proc_macro_attribute]
pub fn opname(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn commutator(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn negator(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn restrict(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn join(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  no values
#[proc_macro_attribute]
pub fn hashes(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  no values
#[proc_macro_attribute]
pub fn merges(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Declare a function as `#[pg_extern]` to indicate that it can be used by Postgres as a UDF
#[proc_macro_attribute]
pub fn pg_extern(attr: TokenStream, item: TokenStream) -> TokenStream {
    let args = parse_extern_attributes(TokenStream2::from(attr));
    let is_raw = args.contains(&ExternArgs::Raw);
    let no_guard = args.contains(&ExternArgs::NoGuard);

    let ast = parse_macro_input!(item as syn::Item);
    match ast {
        Item::Fn(func) => rewrite_item_fn(func, is_raw, no_guard).into(),
        _ => panic!("#[pg_extern] can only be applied to top-level functions"),
    }
}

fn rewrite_item_fn(mut func: ItemFn, is_raw: bool, no_guard: bool) -> proc_macro2::TokenStream {
    let finfo_name = syn::Ident::new(
        &format!("pg_finfo_{}_wrapper", func.sig.ident),
        Span::call_site(),
    );

    // use the PgGuardRewriter to go ahead and wrap the function here, rather than applying
    // a #[pg_guard] macro to the original function.  This is necessary so that compiler
    // errors/warnings indicate the proper line numbers
    let rewriter = PgGuardRewriter::new();

    // make the function 'extern "C"' because this is for the #[pg_extern[ macro
    func.sig.abi = Some(syn::parse_str("extern \"C\"").unwrap());
    let func_span = func.span();
    let (rewritten_func, need_wrapper) = rewriter.item_fn(func, true, is_raw, no_guard);

    if need_wrapper {
        quote_spanned! {func_span=>
            #[no_mangle]
            pub extern "C" fn #finfo_name() -> &'static pg_sys::Pg_finfo_record {
                const V1_API: pg_sys::Pg_finfo_record = pg_sys::Pg_finfo_record { api_version: 1 };
                &V1_API
            }

            #rewritten_func
        }
    } else {
        quote_spanned! {func_span=>#rewritten_func}
    }
}

#[proc_macro_derive(PostgresEnum)]
pub fn postgres_enum(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_postgres_enum(ast).into()
}

fn impl_postgres_enum(ast: DeriveInput) -> proc_macro2::TokenStream {
    let mut stream = proc_macro2::TokenStream::new();
    let enum_ident = ast.ident;
    let enum_name = enum_ident.to_string();

    // validate that we're only operating on an enum
    let enum_data = match ast.data {
        Data::Enum(e) => e,
        _ => panic!("#[derive(PostgresEnum)] can only be applied to enums"),
    };

    let mut from_datum = proc_macro2::TokenStream::new();
    let mut into_datum = proc_macro2::TokenStream::new();

    for d in enum_data.variants {
        let label_ident = &d.ident;
        let label_string = label_ident.to_token_stream().to_string();

        from_datum.extend(quote! { #label_string => Some(#enum_ident::#label_ident), });
        into_datum.extend(quote! { #enum_ident::#label_ident => Some(pgx::lookup_enum_by_label(#enum_name, #label_string)), });
    }

    stream.extend(quote! {
        impl pgx::FromDatum for #enum_ident {
            #[inline]
            unsafe fn from_datum(datum: pgx::pg_sys::Datum, is_null: bool, typeoid: pgx::pg_sys::Oid) -> Option<#enum_ident> {
                if is_null {
                    None
                } else {
                    let (name, _, _) = pgx::lookup_enum_by_oid(datum as pgx::pg_sys::Oid);
                    match name.as_str() {
                        #from_datum
                        _ => panic!("invalid enum value: {}", name)
                    }
                }
            }
        }

        impl pgx::IntoDatum for #enum_ident {
            #[inline]
            fn into_datum(self) -> Option<pgx::pg_sys::Datum> {
                match self {
                    #into_datum
                }
            }

            fn type_oid() -> pg_sys::Oid {
                unsafe {
                    pgx::direct_function_call::<pgx::pg_sys::Oid>(pgx::pg_sys::regtypein, vec![#enum_name.into_datum()])
                        .expect("failed to lookup typeoid")
                }
            }

        }
    });

    stream
}

#[proc_macro_derive(PostgresType, attributes(inoutfuncs))]
pub fn postgres_type(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_postgres_type(ast).into()
}

fn impl_postgres_type(ast: DeriveInput) -> proc_macro2::TokenStream {
    let name = &ast.ident;
    let generics = &ast.generics;
    let has_lifetimes = generics.lifetimes().next();
    let name_string = format!("{}", name);
    let funcname_in = Ident::new(&format!("{}_in", name).to_lowercase(), name.span());
    let funcname_out = Ident::new(&format!("{}_out", name).to_lowercase(), name.span());
    let mut args = parse_postgres_type_args(&ast.attrs);
    let mut stream = proc_macro2::TokenStream::new();

    // validate that we're only operating on a struct
    match ast.data {
        Data::Struct(_) => { /* this is okay */ }
        _ => panic!("#[derive(PostgresType)] can only be applied to structs"),
    }

    if args.is_empty() {
        // assume the user wants us to implement the InOutFuncs
        args.insert(PostgresTypeAttribute::Default);
    }

    let (from_varlena, to_varlena, lifetime) = match has_lifetimes {
        Some(lifetime) => (
            quote! {from_varlena_borrowed},
            quote! {to_varlena_borrowed},
            lifetime.to_token_stream(),
        ),
        None => (
            quote! {from_varlena_owned},
            quote! {to_varlena_owned},
            quote! {'static},
        ),
    };

    if args.contains(&PostgresTypeAttribute::Default) {
        let inout_generics = if has_lifetimes.is_some() {
            generics.to_token_stream()
        } else {
            quote! {<'_>}
        };

        stream.extend(quote! {
            impl #generics InOutFuncs #inout_generics for #name #generics {}
        });
    }

    stream.extend(quote! {

        impl #generics pgx::FromDatum for #name #generics {
            #[inline]
            unsafe fn from_datum(datum: pgx::pg_sys::Datum, is_null: bool, typoid: pgx::pg_sys::Oid) -> Option<#name #generics> {
                if is_null {
                    None
                } else if datum == 0 {
                    panic!("{} datum flagged non-null but its datum is zero", stringify!(#name));
                } else {
                    Some(pgx::#from_varlena(datum as *const pgx::pg_sys::varlena)
                        .expect(&format!("failed to deserialize a {}", stringify!(#name))))
                }
            }
        }

        impl #generics pgx::IntoDatum for #name #generics {
            #[inline]
            fn into_datum(self) -> Option<pgx::pg_sys::Datum> {
                Some(pgx::#to_varlena(&self).expect(&format!("failed to serialize a {}", stringify!(#name))) as pgx::pg_sys::Datum)
            }

            fn type_oid() -> pg_sys::Oid {
                unsafe {
                    pgx::direct_function_call::<pgx::pg_sys::Oid>(pgx::pg_sys::regtypein, vec![#name_string.into_datum()])
                        .expect("failed to lookup typeoid")
                }
            }
        }

        #[pg_extern(immutable)]
        pub fn #funcname_in #generics(input: &#lifetime std::ffi::CStr) -> #name #generics {
            #name::input(input.to_str().unwrap()).expect(&format!("failed to convert input to a {}", stringify!(#name)))
        }

        #[pg_extern(immutable)]
        pub fn #funcname_out #generics(input: #name #generics) -> &#lifetime std::ffi::CStr {
            let mut buffer = StringInfo::new();
            input.output(&mut buffer);
            buffer.into()
        }
    });

    stream
}

#[proc_macro_derive(PostgresGucEnum, attributes(hidden))]
pub fn postgres_guc_enum(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_guc_enum(ast).into()
}

fn impl_guc_enum(ast: DeriveInput) -> proc_macro2::TokenStream {
    let mut stream = proc_macro2::TokenStream::new();

    // validate that we're only operating on an enum
    let enum_data = match ast.data {
        Data::Enum(e) => e,
        _ => panic!("#[derive(PostgresGucEnum)] can only be applied to enums"),
    };
    let enum_name = ast.ident;
    let enum_len = enum_data.variants.len();

    let mut from_match_arms = proc_macro2::TokenStream::new();
    for (idx, e) in enum_data.variants.iter().enumerate() {
        let label = &e.ident;
        let idx = idx as i32;
        from_match_arms.extend(quote! { #idx => #enum_name::#label, })
    }
    from_match_arms.extend(quote! { _ => panic!("Unrecognized ordinal ")});

    let mut ordinal_match_arms = proc_macro2::TokenStream::new();
    for (idx, e) in enum_data.variants.iter().enumerate() {
        let label = &e.ident;
        let idx = idx as i32;
        ordinal_match_arms.extend(quote! { #enum_name::#label => #idx, });
    }

    let mut build_array_body = proc_macro2::TokenStream::new();
    for (idx, e) in enum_data.variants.iter().enumerate() {
        let label = e.ident.to_string();
        let mut hidden = false;

        for att in e.attrs.iter() {
            if att.to_token_stream().to_string() == "# [hidden]" {
                hidden = true;
                break;
            }
        }

        build_array_body.extend(quote! {
            pgx::PgBox::with(&mut slice[#idx], |v| {
                v.name = pgx::PgMemoryContexts::TopMemoryContext.pstrdup(#label);
                v.val = #idx as i32;
                v.hidden = #hidden;
            });
        });
    }

    stream.extend(quote! {
        impl pgx::GucEnum<#enum_name> for #enum_name {
            fn from_ordinal(ordinal: i32) -> #enum_name {
                match ordinal {
                    #from_match_arms
                }
            }

            fn to_ordinal(&self) -> i32 {
                match *self {
                    #ordinal_match_arms
                }
            }

            unsafe fn config_matrix(&self) -> *const pgx::pg_sys::config_enum_entry {
                let slice = pgx::PgMemoryContexts::TopMemoryContext.palloc0_slice::<pg_sys::config_enum_entry>(#enum_len + 1usize);

                #build_array_body

                slice.as_ptr()
            }
        }
    });

    stream
}

#[derive(Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
enum PostgresTypeAttribute {
    Custom,
    Default,
}

fn parse_postgres_type_args(attributes: &[Attribute]) -> HashSet<PostgresTypeAttribute> {
    let mut categorized_attributes = HashSet::new();

    for a in attributes {
        match a.path.to_token_stream().to_string().as_str() {
            "inoutfuncs" => match a.tokens.to_string().as_str() {
                "= \"Custom\"" => categorized_attributes.insert(PostgresTypeAttribute::Custom),

                "= \"Default\"" => categorized_attributes.insert(PostgresTypeAttribute::Default),

                _ => panic!("unrecognized PostgresType property: {}", a.tokens),
            },
            _ => panic!(
                "unrecognized PostgresType attribute: {}",
                a.path.to_token_stream().to_string()
            ),
        };
    }

    categorized_attributes
}

#[proc_macro]
pub fn extension_sql(_: TokenStream) -> TokenStream {
    // we don't want to output anything here
    TokenStream::new()
}