// Copyright 2019-2021 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any
// person obtaining a copy of this software and associated
// documentation files (the "Software"), to deal in the
// Software without restriction, including without
// limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software
// is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice
// shall be included in all copies or substantial portions
// of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use std::collections::HashSet;
use std::str::FromStr;

use super::RpcDescription;
use crate::{
	helpers::{generate_where_clause, is_option},
	rpc_macro::RpcFnArg,
};
use proc_macro2::{Span, TokenStream as TokenStream2};
use quote::{quote, quote_spanned};
use syn::Attribute;

impl RpcDescription {
	pub(super) fn render_server(&self) -> Result<TokenStream2, syn::Error> {
		let trait_name = quote::format_ident!("{}Server", &self.trait_def.ident);
		let generics = self.trait_def.generics.clone();
		let (impl_generics, _, where_clause) = generics.split_for_impl();

		let method_impls = self.render_methods()?;
		let into_rpc_impl = self.render_into_rpc()?;
		let async_trait = self.jrps_server_item(quote! { core::__reexports::async_trait });

		// Doc-comment to be associated with the server.
		let doc_comment = format!("Server trait implementation for the `{}` RPC API.", &self.trait_def.ident);

		let trait_impl = quote! {
			#[#async_trait]
			#[doc = #doc_comment]
			pub trait #trait_name #impl_generics: Sized + Send + Sync + 'static #where_clause {
				#method_impls
				#into_rpc_impl
			}
		};

		Ok(trait_impl)
	}

	fn render_methods(&self) -> Result<TokenStream2, syn::Error> {
		let methods = self.methods.iter().map(|method| {
			let docs = &method.docs;
			let mut method_sig = method.signature.clone();

			if method.with_extensions {
				let ext_ty = self.jrps_server_item(quote! { Extensions });
				// Add `Extension` as the second parameter to the signature.
				let ext: syn::FnArg = syn::parse_quote!(ext: &#ext_ty);
				method_sig.sig.inputs.insert(1, ext);
			}

			quote! {
				#docs
				#method_sig
			}
		});

		let subscriptions = self.subscriptions.iter().map(|sub| {
			let docs = &sub.docs;
			let subscription_sink_ty = self.jrps_server_item(quote! { PendingSubscriptionSink });

			// Add `SubscriptionSink` as the second input parameter to the signature.
			let subscription_sink: syn::FnArg = syn::parse_quote!(subscription_sink: #subscription_sink_ty);
			let mut sub_sig = sub.signature.clone();
			sub_sig.sig.inputs.insert(1, subscription_sink);

			if sub.with_extensions {
				let ext_ty = self.jrps_server_item(quote! { Extensions });
				// Add `Extension` as the third parameter to the signature.
				let ext: syn::FnArg = syn::parse_quote!(ext: &#ext_ty);
				sub_sig.sig.inputs.insert(2, ext);
			}

			quote! {
				#docs
				#sub_sig
			}
		});

		Ok(quote! {
			#(#methods)*
			#(#subscriptions)*
		})
	}

	/// Helper that will ignore results of `register_*` method calls, and panic if there have been
	/// any errors in debug builds.
	///
	/// The debug assert is a safeguard should the contract that guarantees the method names to
	/// never conflict in the macro be broken in the future.
	fn handle_register_result(&self, tokens: TokenStream2) -> TokenStream2 {
		let reexports = self.jrps_server_item(quote! { core::__reexports });
		quote! {{
			let _res = #tokens;
			#[cfg(debug_assertions)]
			if _res.is_err() {
				#reexports::panic_fail_register();
			}
		}}
	}

	fn render_into_rpc(&self) -> Result<TokenStream2, syn::Error> {
		let rpc_module = self.jrps_server_item(quote! { RpcModule });

		let mut registered = HashSet::new();
		let mut errors = Vec::new();
		let mut check_name = |name: &str, span: Span| {
			if registered.contains(name) {
				let message = format!("{name:?} is already defined");
				errors.push(quote_spanned!(span => compile_error!(#message);));
			} else {
				registered.insert(name.to_string());
			}
		};

		let methods = self
			.methods
			.iter()
			.map(|method| {
				// Rust method to invoke (e.g. `self.<foo>(...)`).
				let rust_method_name = &method.signature.sig.ident;
				// Name of the RPC method (e.g. `foo_makeSpam`).
				let rpc_method_name = self.rpc_identifier(&method.name);
				// `parsing` is the code associated with parsing structure from the
				// provided `Params` object.
				// `params_seq` is the comma-delimited sequence of parameters we're passing to the rust function
				// called..
				let (parsing, params_seq) = self.render_params_decoding(&method.params, None);

				let into_response = self.jrps_server_item(quote! { IntoResponse });

				check_name(&rpc_method_name, rust_method_name.span());

				if method.signature.sig.asyncness.is_some() {
					if method.with_extensions {
						self.handle_register_result(quote! {
							rpc.register_async_method(#rpc_method_name, |params, context, ext| async move {
								#parsing
								#into_response::into_response(context.as_ref().#rust_method_name(&ext, #params_seq).await)
							})
						})
					} else {
						self.handle_register_result(quote! {
							rpc.register_async_method(#rpc_method_name, |params, context, _| async move {
								#parsing
								#into_response::into_response(context.as_ref().#rust_method_name(#params_seq).await)
							})
						})
					}
				} else {
					let register_kind =
						if method.blocking { quote!(register_blocking_method) } else { quote!(register_method) };

					if method.with_extensions {
						self.handle_register_result(quote! {
							rpc.#register_kind(#rpc_method_name, |params, context, ext| {
								#parsing
								#into_response::into_response(context.#rust_method_name(&ext, #params_seq))
							})
						})
					} else {
						self.handle_register_result(quote! {
							rpc.#register_kind(#rpc_method_name, |params, context, _| {
								#parsing
								#into_response::into_response(context.#rust_method_name(#params_seq))
							})
						})
					}
				}
			})
			.collect::<Vec<_>>();

		let subscriptions = self
			.subscriptions
			.iter()
			.map(|sub| {
				// Rust method to invoke (e.g. `self.<foo>(...)`).
				let rust_method_name = &sub.signature.sig.ident;
				// Name of the RPC method to subscribe to (e.g. `foo_sub`).
				let rpc_sub_name = self.rpc_identifier(&sub.name);
				// Name of `method` in the subscription response.
				let rpc_notif_name_override = sub.notif_name_override.as_ref().map(|m| self.rpc_identifier(m));
				// Name of the RPC method to unsubscribe (e.g. `foo_sub`).
				let rpc_unsub_name = self.rpc_identifier(&sub.unsubscribe);
				// `parsing` is the code associated with parsing structure from the
				// provided `Params` object.
				// `params_seq` is the comma-delimited sequence of parameters.
				let pending = proc_macro2::Ident::new("pending", rust_method_name.span());
				let (parsing, params_seq) = self.render_params_decoding(&sub.params, Some(pending));
				let sub_err = self.jrps_server_item(quote! { SubscriptionCloseResponse });
				let into_sub_response = self.jrps_server_item(quote! { IntoSubscriptionCloseResponse });

				check_name(&rpc_sub_name, rust_method_name.span());
				check_name(&rpc_unsub_name, rust_method_name.span());

				let rpc_notif_name = match rpc_notif_name_override {
					Some(notif) => {
						check_name(&notif, rust_method_name.span());
						notif
					}
					None => rpc_sub_name.clone(),
				};

				if sub.signature.sig.asyncness.is_some() {
					if sub.with_extensions {
						self.handle_register_result(quote! {
							rpc.register_subscription(#rpc_sub_name, #rpc_notif_name, #rpc_unsub_name, |params, mut pending, context, ext| async move {
								#parsing
								#into_sub_response::into_response(context.as_ref().#rust_method_name(pending, &ext, #params_seq).await)
							})
						})
					} else {
						self.handle_register_result(quote! {
							rpc.register_subscription(#rpc_sub_name, #rpc_notif_name, #rpc_unsub_name, |params, mut pending, context, _| async move {
								#parsing
								#into_sub_response::into_response(context.as_ref().#rust_method_name(pending, #params_seq).await)
							})
						})
					}
				} else if sub.with_extensions {
					self.handle_register_result(quote! {
						rpc.register_subscription_raw(#rpc_sub_name, #rpc_notif_name, #rpc_unsub_name, |params, mut pending, context, ext| {
							#parsing
							let _ = context.as_ref().#rust_method_name(pending, &ext, #params_seq);
							#sub_err::None
						})
					})
				} else {
					self.handle_register_result(quote! {
						rpc.register_subscription_raw(#rpc_sub_name, #rpc_notif_name, #rpc_unsub_name, |params, mut pending, context, _| {
							#parsing
							let _ = context.as_ref().#rust_method_name(pending, #params_seq);
							#sub_err::None
						})
					})
				}
			})
			.collect::<Vec<_>>();

		let method_aliases = self
			.methods
			.iter()
			.map(|method| {
				let rpc_name = self.rpc_identifier(&method.name);
				let rust_method_name = &method.signature.sig.ident;

				// Rust method to invoke (e.g. `self.<foo>(...)`).
				let aliases: Vec<TokenStream2> = method
					.aliases
					.iter()
					.map(|alias| {
						check_name(alias, rust_method_name.span());
						self.handle_register_result(quote! {
							rpc.register_alias(#alias, #rpc_name)
						})
					})
					.collect();

				quote!( #(#aliases)* )
			})
			.collect::<Vec<_>>();

		let subscription_aliases = self
			.subscriptions
			.iter()
			.map(|method| {
				let sub_name = self.rpc_identifier(&method.name);
				let unsub_name = self.rpc_identifier(&method.unsubscribe);
				let rust_method_name = &method.signature.sig.ident;

				let sub: Vec<TokenStream2> = method
					.aliases
					.iter()
					.map(|alias| {
						check_name(alias, rust_method_name.span());
						self.handle_register_result(quote! {
							rpc.register_alias(#alias, #sub_name)
						})
					})
					.collect();
				let unsub: Vec<TokenStream2> = method
					.unsubscribe_aliases
					.iter()
					.map(|alias| {
						check_name(alias, rust_method_name.span());
						self.handle_register_result(quote! {
							rpc.register_alias(#alias, #unsub_name)
						})
					})
					.collect();

				quote! (
					#(#sub)*
					#(#unsub)*
				)
			})
			.collect::<Vec<_>>();

		let doc_comment = "Collects all the methods and subscriptions defined in the trait \
								and adds them into a single `RpcModule`.";

		let sub_tys: Vec<syn::Type> = self.subscriptions.clone().into_iter().map(|s| s.item).collect();
		let where_clause = generate_where_clause(&self.trait_def, &sub_tys, false, self.server_bounds.as_ref());

		// NOTE(niklasad1): empty where clause is valid rust syntax.
		Ok(quote! {
			#[doc = #doc_comment]
			fn into_rpc(self) -> #rpc_module<Self> where #(#where_clause,)* {
				let mut rpc = #rpc_module::new(self);

				#(#errors)*
				#(#methods)*
				#(#subscriptions)*
				#(#method_aliases)*
				#(#subscription_aliases)*

				rpc
			}
		})
	}

	fn render_params_decoding(
		&self,
		params: &[RpcFnArg],
		sub: Option<proc_macro2::Ident>,
	) -> (TokenStream2, TokenStream2) {
		if params.is_empty() {
			return (TokenStream2::default(), TokenStream2::default());
		}

		let params_fields_seq = params.iter().map(RpcFnArg::arg_pat);
		let params_fields = quote! { #(#params_fields_seq),* };

		let reexports = self.jrps_server_item(quote! { core::__reexports });

		let error_ret = if let Some(pending) = &sub {
			let tokio = quote! { #reexports::tokio };
			let sub_err = self.jrps_server_item(quote! { SubscriptionCloseResponse });
			quote! {
				#tokio::spawn(#pending.reject(e));
				return #sub_err::None;
			}
		} else {
			let response_payload = self.jrps_server_item(quote! { ResponsePayload });
			quote! {
				return #response_payload::error(e);
			}
		};

		// Code to decode sequence of parameters from a JSON array.
		let decode_array = {
			let decode_fields = params.iter().map(|RpcFnArg { arg_pat, ty, .. }| {
				let is_option = is_option(ty);
				let next_method = if is_option { quote!(optional_next) } else { quote!(next) };
				quote! {
					let #arg_pat: #ty = match seq.#next_method() {
						Ok(v) => v,
						Err(e) => {
							#reexports::log_fail_parse(stringify!(#arg_pat), stringify!(#ty), &e, #is_option);
							#error_ret
						}
					};
				}
			});

			quote! {
				let mut seq = params.sequence();
				#(#decode_fields);*
				(#params_fields)
			}
		};

		// Code to decode sequence of parameters from a JSON object (aka map).
		let decode_map = {
			let generics = (0..params.len()).map(|n| quote::format_ident!("G{}", n));

			let serde = self.jrps_server_item(quote! { core::__reexports::serde });
			let serde_crate = serde.to_string();

			let fields = params.iter().zip(generics.clone()).map(|(fn_arg, ty)| {
				let arg_pat = fn_arg.arg_pat();
				let name = fn_arg.name();

				let mut alias_vals = String::new();
				alias_vals.push_str(&format!(r#"alias = "{}""#, heck::ToSnakeCase::to_snake_case(name.as_str())));
				alias_vals.push(',');
				alias_vals
					.push_str(&format!(r#"alias = "{}""#, heck::ToLowerCamelCase::to_lower_camel_case(name.as_str())));

				let serde_rename = quote!(#[serde(rename = #name)]);

				let alias = TokenStream2::from_str(alias_vals.as_str()).unwrap();

				let serde_alias: Attribute = syn::parse_quote! {
					#[serde(#alias)]
				};

				quote! {
					#serde_alias
					#serde_rename
					#arg_pat: #ty,
				}
			});
			let destruct = params.iter().map(RpcFnArg::arg_pat).map(|a| quote!(parsed.#a));
			let types = params.iter().map(RpcFnArg::ty);

			quote! {
				#[derive(#serde::Deserialize)]
				#[serde(crate = #serde_crate)]
				struct ParamsObject<#(#generics,)*> {
					#(#fields)*
				}

				let parsed: ParamsObject<#(#types,)*> = match params.parse() {
					Ok(p) => p,
					Err(e) => {
						#reexports::log_fail_parse_as_object(&e);
						#error_ret
					}
				};

				(#(#destruct),*)
			}
		};

		let parsing = quote! {
			let (#params_fields) = if params.is_object() {
				#decode_map
			} else {
				#decode_array
			};
		};

		(parsing, params_fields)
	}
}