use crate::args;
use crate::utils::{check_reserved_name, get_crate_name};
use inflector::Inflector;
use proc_macro::TokenStream;
use quote::quote;
use syn::{Data, DeriveInput, Error, Fields, Result};

pub fn generate(object_args: &args::Object, input: &mut DeriveInput) -> Result<TokenStream> {
    let crate_name = get_crate_name(object_args.internal);
    let ident = &input.ident;
    let generics = &input.generics;
    let extends = object_args.extends;
    let s = match &mut input.data {
        Data::Struct(e) => e,
        _ => return Err(Error::new_spanned(input, "It should be a struct")),
    };
    let gql_typename = object_args
        .name
        .clone()
        .unwrap_or_else(|| ident.to_string());
    check_reserved_name(&gql_typename, object_args.internal)?;

    let desc = object_args
        .desc
        .as_ref()
        .map(|s| quote! { Some(#s) })
        .unwrap_or_else(|| quote! {None});

    let mut getters = Vec::new();
    let mut resolvers = Vec::new();
    let mut schema_fields = Vec::new();
    let fields = match &mut s.fields {
        Fields::Named(fields) => Some(fields),
        Fields::Unit => None,
        _ => return Err(Error::new_spanned(input, "All fields must be named.")),
    };

    if let Some(fields) = fields {
        for item in &mut fields.named {
            if let Some(field) = args::Field::parse(&item.attrs)? {
                let field_name = field
                    .name
                    .clone()
                    .unwrap_or_else(|| item.ident.as_ref().unwrap().to_string().to_camel_case());
                let field_desc = field
                    .desc
                    .as_ref()
                    .map(|s| quote! {Some(#s)})
                    .unwrap_or_else(|| quote! {None});
                let field_deprecation = field
                    .deprecation
                    .as_ref()
                    .map(|s| quote! {Some(#s)})
                    .unwrap_or_else(|| quote! {None});
                let external = field.external;
                let requires = match &field.requires {
                    Some(requires) => quote! { Some(#requires) },
                    None => quote! { None },
                };
                let provides = match &field.provides {
                    Some(provides) => quote! { Some(#provides) },
                    None => quote! { None },
                };
                let vis = &item.vis;
                let ty = &item.ty;

                let cache_control = {
                    let public = field.cache_control.public;
                    let max_age = field.cache_control.max_age;
                    quote! {
                        #crate_name::CacheControl {
                            public: #public,
                            max_age: #max_age,
                        }
                    }
                };

                schema_fields.push(quote! {
                    fields.insert(#field_name.to_string(), #crate_name::registry::Field {
                        name: #field_name.to_string(),
                        description: #field_desc,
                        args: Default::default(),
                        ty: <#ty as #crate_name::Type>::create_type_info(registry),
                        deprecation: #field_deprecation,
                        cache_control: #cache_control,
                        external: #external,
                        provides: #provides,
                        requires: #requires,
                    });
                });

                let ident = &item.ident;

                if field.is_ref {
                    getters.push(quote! {
                        #[inline]
                        #vis async fn #ident(&self) -> &#ty {
                            &self.#ident
                        }
                    });
                } else {
                    getters.push(quote! {
                        #[inline]
                        #vis async fn #ident(&self) -> #ty {
                            self.#ident.clone()
                        }
                    });
                }

                resolvers.push(quote! {
                    if ctx.name.as_str() == #field_name {
                        let ctx_obj = ctx.with_selection_set(&ctx.selection_set);
                        return #crate_name::OutputValueType::resolve(&self.#ident, &ctx_obj, ctx.position).await;
                    }
                });

                if let Some((idx, _)) = item
                    .attrs
                    .iter()
                    .enumerate()
                    .find(|(_, a)| a.path.is_ident("field"))
                {
                    item.attrs.remove(idx);
                }
            }
        }
    }

    let cache_control = {
        let public = object_args.cache_control.public;
        let max_age = object_args.cache_control.max_age;
        quote! {
            #crate_name::CacheControl {
                public: #public,
                max_age: #max_age,
            }
        }
    };

    let expanded = quote! {
        #input

        impl #generics #ident {
            #(#getters)*
        }

        impl #generics #crate_name::Type for #ident #generics {
            fn type_name() -> std::borrow::Cow<'static, str> {
                std::borrow::Cow::Borrowed(#gql_typename)
            }

            fn create_type_info(registry: &mut #crate_name::registry::Registry) -> String {
                registry.create_type::<Self, _>(|registry| #crate_name::registry::Type::Object {
                    name: #gql_typename.to_string(),
                    description: #desc,
                    fields: {
                        let mut fields = std::collections::HashMap::new();
                        #(#schema_fields)*
                        fields
                    },
                    cache_control: #cache_control,
                    extends: #extends,
                    keys: None,
                })
            }
        }

        #[#crate_name::async_trait::async_trait]
        impl #generics #crate_name::ObjectType for #ident #generics {
            async fn resolve_field(&self, ctx: &#crate_name::Context<'_>) -> #crate_name::Result<#crate_name::serde_json::Value> {
                #(#resolvers)*
                Err(#crate_name::QueryError::FieldNotFound {
                    field_name: ctx.name.clone(),
                    object: #gql_typename.to_string(),
                }.into_error(ctx.position))
            }
        }

        #[#crate_name::async_trait::async_trait]
        impl #generics #crate_name::OutputValueType for #ident #generics {
            async fn resolve(value: &Self, ctx: &#crate_name::ContextSelectionSet<'_>, _pos: #crate_name::Pos) -> #crate_name::Result<#crate_name::serde_json::Value> {
                #crate_name::do_resolve(ctx, value).await
            }
        }
    };
    Ok(expanded.into())
}