use crate::args;
use crate::output_type::OutputType;
use crate::utils::{build_value_repr, check_reserved_name, get_crate_name};
use inflector::Inflector;
use proc_macro::TokenStream;
use quote::quote;
use syn::{Error, FnArg, ImplItem, ItemImpl, Pat, Result, ReturnType, Type, TypeReference};

pub fn generate(object_args: &args::Object, item_impl: &mut ItemImpl) -> Result<TokenStream> {
    let crate_name = get_crate_name(object_args.internal);
    let (self_ty, self_name) = match item_impl.self_ty.as_ref() {
        Type::Path(path) => (
            path,
            path.path
                .segments
                .last()
                .map(|s| s.ident.to_string())
                .unwrap(),
        ),
        _ => return Err(Error::new_spanned(&item_impl.self_ty, "Invalid type")),
    };
    let generics = &item_impl.generics;

    let gql_typename = object_args
        .name
        .clone()
        .unwrap_or_else(|| self_name.clone());
    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 resolvers = Vec::new();
    let mut schema_fields = Vec::new();

    for item in &mut item_impl.items {
        if let ImplItem::Method(method) = item {
            if let Some(field) = args::Field::parse(&method.attrs)? {
                let field_name = field
                    .name
                    .clone()
                    .unwrap_or_else(|| method.sig.ident.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 ty = match &method.sig.output {
                    ReturnType::Type(_, ty) => OutputType::parse(ty)?,
                    ReturnType::Default => {
                        return Err(Error::new_spanned(&method.sig.output, "Missing type"))
                    }
                };

                let mut arg_ctx = false;
                let mut args = Vec::new();

                for (idx, arg) in method.sig.inputs.iter_mut().enumerate() {
                    if let FnArg::Receiver(receiver) = arg {
                        if idx != 0 {
                            return Err(Error::new_spanned(
                                receiver,
                                "The self receiver must be the first parameter.",
                            ));
                        }
                    } else if let FnArg::Typed(pat) = arg {
                        if idx == 0 {
                            return Err(Error::new_spanned(
                                pat,
                                "The self receiver must be the first parameter.",
                            ));
                        }

                        match (&*pat.pat, &*pat.ty) {
                            (Pat::Ident(arg_ident), Type::Path(arg_ty)) => {
                                args.push((
                                    arg_ident,
                                    arg_ty,
                                    args::Argument::parse(&crate_name, &pat.attrs)?,
                                ));
                                pat.attrs.clear();
                            }
                            (_, Type::Reference(TypeReference { elem, .. })) => {
                                if let Type::Path(path) = elem.as_ref() {
                                    if idx != 1
                                        || path.path.segments.last().unwrap().ident != "Context"
                                    {
                                        return Err(Error::new_spanned(
                                            arg,
                                            "The Context must be the second argument.",
                                        ));
                                    }
                                    arg_ctx = true;
                                }
                            }
                            _ => return Err(Error::new_spanned(arg, "Invalid argument type.")),
                        }
                    }
                }

                let mut schema_args = Vec::new();
                let mut use_params = Vec::new();
                let mut get_params = Vec::new();

                for (
                    ident,
                    ty,
                    args::Argument {
                        name,
                        desc,
                        default,
                        validators,
                    },
                ) in args
                {
                    let name = name
                        .clone()
                        .unwrap_or_else(|| ident.ident.to_string().to_camel_case());
                    let desc = desc
                        .as_ref()
                        .map(|s| quote! {Some(#s)})
                        .unwrap_or_else(|| quote! {None});
                    let schema_default = default
                        .as_ref()
                        .map(|v| {
                            let s = v.to_string();
                            quote! {Some(#s)}
                        })
                        .unwrap_or_else(|| quote! {None});

                    schema_args.push(quote! {
                        args.insert(#name, #crate_name::registry::InputValue {
                            name: #name,
                            description: #desc,
                            ty: <#ty as #crate_name::Type>::create_type_info(registry),
                            default_value: #schema_default,
                            validators: #validators,
                        });
                    });

                    use_params.push(quote! { #ident });

                    let default = match &default {
                        Some(default) => {
                            let repr = build_value_repr(&crate_name, &default);
                            quote! {|| #repr }
                        }
                        None => quote! { || #crate_name::Value::Null },
                    };

                    get_params.push(quote! {
                        let #ident: #ty = ctx.param_value(#name, #default)?;
                    });
                }

                let schema_ty = ty.value_type();
                schema_fields.push(quote! {
                    fields.insert(#field_name.to_string(), #crate_name::registry::Field {
                        name: #field_name.to_string(),
                        description: #field_desc,
                        args: {
                            let mut args = std::collections::HashMap::new();
                            #(#schema_args)*
                            args
                        },
                        ty: <#schema_ty as #crate_name::Type>::create_type_info(registry),
                        deprecation: #field_deprecation,
                    });
                });

                let ctx_field = if arg_ctx {
                    quote! { &ctx, }
                } else {
                    quote! {}
                };

                let field_ident = &method.sig.ident;
                let resolve_obj = match &ty {
                    OutputType::Value(_) => quote! {
                        self.#field_ident(#ctx_field #(#use_params),*).await
                    },
                    OutputType::Result(_, _) => {
                        quote! {
                            self.#field_ident(#ctx_field #(#use_params),*).await.
                                map_err(|err| err.with_position(field.position))?
                        }
                    }
                };

                resolvers.push(quote! {
                    if field.name.as_str() == #field_name {
                        #(#get_params)*
                        let ctx_obj = ctx.with_item(&field.selection_set);
                        return #crate_name::OutputValueType::resolve(&#resolve_obj, &ctx_obj).await.
                            map_err(|err| err.with_position(field.position).into());
                    }
                });

                method.attrs.clear();
            }
        }
    }

    let expanded = quote! {
        #item_impl

        impl #generics #crate_name::Type for #self_ty {
            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
                    },
                })
            }
        }

        #[#crate_name::async_trait::async_trait]
        impl#generics #crate_name::ObjectType for #self_ty {
            async fn resolve_field(&self, ctx: &#crate_name::Context<'_>, field: &#crate_name::graphql_parser::query::Field) -> #crate_name::Result<#crate_name::serde_json::Value> {
                use #crate_name::ErrorWithPosition;

                #(#resolvers)*

                #crate_name::anyhow::bail!(#crate_name::QueryError::FieldNotFound {
                    field_name: field.name.clone(),
                    object: #gql_typename.to_string(),
                }
                .with_position(field.position));
            }

            async fn resolve_inline_fragment(&self, name: &str, ctx: &#crate_name::ContextSelectionSet<'_>, result: &mut #crate_name::serde_json::Map<String, #crate_name::serde_json::Value>) -> #crate_name::Result<()> {
                #crate_name::anyhow::bail!(#crate_name::QueryError::UnrecognizedInlineFragment {
                    object: #gql_typename.to_string(),
                    name: name.to_string(),
                });
            }
        }

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