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extern crate proc_macro;

/// Derive-related code. This will be moved into graphql_query_derive.
mod attributes;

use failure::ResultExt;
use graphql_client_codegen::{
    generate_module_token_stream, CodegenMode, GraphQLClientCodegenOptions,
};
use std::path::{Path, PathBuf};

use proc_macro2::TokenStream;

#[proc_macro_derive(GraphQLQuery, attributes(graphql))]
pub fn derive_graphql_query(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    match graphql_query_derive_inner(input) {
        Ok(ts) => ts,
        Err(err) => panic!(
            "{}",
            err.iter_chain()
                .fold(String::new(), |mut acc, item| {
                    acc.push_str(&format!("{}\n", item));
                    acc
                })
                .trim_end_matches('\n')
        ),
    }
}

fn graphql_query_derive_inner(
    input: proc_macro::TokenStream,
) -> Result<proc_macro::TokenStream, failure::Error> {
    let input = TokenStream::from(input);
    let ast = syn::parse2(input).context("Derive input parsing.")?;
    let (query_path, schema_path) = build_query_and_schema_path(&ast)?;
    let options = build_graphql_client_derive_options(&ast, query_path.to_path_buf())?;
    Ok(
        generate_module_token_stream(query_path, &schema_path, options)
            .map(Into::into)
            .context("Code generation failed.")?,
    )
}

fn build_query_and_schema_path(
    input: &syn::DeriveInput,
) -> Result<(PathBuf, PathBuf), failure::Error> {
    let cargo_manifest_dir = ::std::env::var("CARGO_MANIFEST_DIR")
        .context("Checking that the CARGO_MANIFEST_DIR env variable is defined.")?;

    let query_path =
        attributes::extract_attr(input, "query_path").context("Extracting query path.")?;
    let query_path = format!("{}/{}", cargo_manifest_dir, query_path);
    let query_path = Path::new(&query_path).to_path_buf();
    let schema_path =
        attributes::extract_attr(input, "schema_path").context("Extracting schema path.")?;
    let schema_path = Path::new(&cargo_manifest_dir).join(schema_path);
    Ok((query_path, schema_path))
}

fn build_graphql_client_derive_options(
    input: &syn::DeriveInput,
    query_path: PathBuf,
) -> Result<GraphQLClientCodegenOptions, failure::Error> {
    let response_derives = attributes::extract_attr(input, "response_derives").ok();

    let mut options = GraphQLClientCodegenOptions::new(CodegenMode::Derive);
    options.set_query_file(query_path);

    if let Some(response_derives) = response_derives {
        options.set_additional_derives(response_derives);
    };

    // The user can determine what to do about deprecations.
    if let Ok(deprecation_strategy) = attributes::extract_deprecation_strategy(input) {
        options.set_deprecation_strategy(deprecation_strategy);
    };

    options.set_struct_ident(input.ident.clone());
    options.set_module_visibility(input.vis.clone());
    options.set_operation_name(input.ident.to_string());

    Ok(options)
}