// Copyright 2019-2023 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

//! Generate code for submitting extrinsics and query storage of a Substrate runtime.

mod calls;
mod constants;
mod custom_values;
mod errors;
mod events;
mod runtime_apis;
mod storage;

use subxt_metadata::Metadata;

use super::DerivesRegistry;
use crate::api::custom_values::generate_custom_values;
use crate::error::CodegenError;
use crate::{
    ir,
    types::{CompositeDef, CompositeDefFields, TypeGenerator, TypeSubstitutes},
    utils::{fetch_metadata_bytes_blocking, MetadataVersion, Url},
    CratePath,
};
use codec::Decode;
use heck::ToSnakeCase as _;
use proc_macro2::TokenStream as TokenStream2;
use quote::{format_ident, quote};
use std::{collections::HashMap, fs, io::Read, path, string::ToString};
use syn::parse_quote;

/// Generate the runtime API for interacting with a substrate runtime.
pub struct GenerateRuntimeApi {
    item_mod: syn::ItemMod,
    derives: DerivesRegistry,
    type_substitutes: TypeSubstitutes,
    crate_path: CratePath,
    should_gen_docs: bool,
    runtime_types_only: bool,
    unstable_metadata: bool,
}

impl GenerateRuntimeApi {
    /// Construct a new [`GenerateRuntimeApi`].
    pub fn new(item_mod: syn::ItemMod, crate_path: CratePath) -> Self {
        GenerateRuntimeApi {
            item_mod,
            derives: DerivesRegistry::new(),
            type_substitutes: TypeSubstitutes::new(),
            crate_path,
            should_gen_docs: false,
            runtime_types_only: false,
            unstable_metadata: false,
        }
    }

    /// Provide custom derives for the generated types.
    ///
    /// Default is no derives.
    pub fn derives_registry(mut self, derives: DerivesRegistry) -> Self {
        self.derives = derives;
        self
    }

    /// Provide custom type substitutes.
    ///
    /// Default is no substitutes.
    pub fn type_substitutes(mut self, type_substitutes: TypeSubstitutes) -> Self {
        self.type_substitutes = type_substitutes;
        self
    }

    /// True if the generated API contains the documentation from the metadata.
    ///
    /// Default: false.
    pub fn generate_docs(mut self, should_gen_docs: bool) -> Self {
        self.should_gen_docs = should_gen_docs;
        self
    }

    /// Whether to limit code generation to only runtime types.
    ///
    /// Default: false.
    pub fn runtime_types_only(mut self, runtime_types_only: bool) -> Self {
        self.runtime_types_only = runtime_types_only;
        self
    }

    /// Whether to fetch the unstable metadata first.
    ///
    /// # Note
    ///
    /// This takes effect only if the API is generated from URL.
    ///
    /// Default: false.
    pub fn unstable_metadata(mut self, unstable_metadata: bool) -> Self {
        self.unstable_metadata = unstable_metadata;
        self
    }

    /// Generate the runtime API from path.
    pub fn generate_from_path<P>(self, path: P) -> Result<TokenStream2, CodegenError>
    where
        P: AsRef<path::Path>,
    {
        let to_err = |err| CodegenError::Io(path.as_ref().to_string_lossy().into(), err);

        let mut file = fs::File::open(&path).map_err(to_err)?;
        let mut bytes = Vec::new();
        file.read_to_end(&mut bytes).map_err(to_err)?;

        let metadata = Metadata::decode(&mut &bytes[..])?;

        generate_runtime_api_with_metadata(
            self.item_mod,
            metadata,
            self.derives,
            self.type_substitutes,
            self.crate_path,
            self.should_gen_docs,
            self.runtime_types_only,
        )
    }

    /// Generate the runtime API from the provided metadata bytes.
    pub fn generate_from_bytes(self, bytes: &[u8]) -> Result<TokenStream2, CodegenError> {
        let metadata = Metadata::decode(&mut &bytes[..])?;

        generate_runtime_api_with_metadata(
            self.item_mod,
            metadata,
            self.derives,
            self.type_substitutes,
            self.crate_path,
            self.should_gen_docs,
            self.runtime_types_only,
        )
    }

    /// Generate the runtime API from URL.
    ///
    /// The metadata will be downloaded from a node at the provided URL.
    /// This function blocks while retrieving the metadata.
    ///
    /// # Warning
    ///
    /// Not recommended to be used in production environments.
    pub fn generate_from_url(self, url: Url) -> Result<TokenStream2, CodegenError> {
        fn fetch_metadata(url: Url, version: MetadataVersion) -> Result<Metadata, CodegenError> {
            let bytes = fetch_metadata_bytes_blocking(url, version)?;
            Ok(Metadata::decode(&mut &bytes[..])?)
        }

        let metadata = self
            .unstable_metadata
            .then(|| fetch_metadata(url.clone(), MetadataVersion::Unstable).ok())
            .flatten();

        let metadata = if let Some(unstable) = metadata {
            unstable
        } else {
            match fetch_metadata(url.clone(), MetadataVersion::Version(15)) {
                Ok(metadata) => metadata,
                Err(_) => fetch_metadata(url, MetadataVersion::Version(14))?,
            }
        };

        generate_runtime_api_with_metadata(
            self.item_mod,
            metadata,
            self.derives,
            self.type_substitutes,
            self.crate_path,
            self.should_gen_docs,
            self.runtime_types_only,
        )
    }
}

/// Generates the API for interacting with a substrate runtime, using the `subxt::Metadata`.
fn generate_runtime_api_with_metadata(
    item_mod: syn::ItemMod,
    metadata: Metadata,
    derives: DerivesRegistry,
    type_substitutes: TypeSubstitutes,
    crate_path: CratePath,
    should_gen_docs: bool,
    runtime_types_only: bool,
) -> Result<TokenStream2, CodegenError> {
    let generator = RuntimeGenerator::new(metadata);
    if runtime_types_only {
        generator.generate_runtime_types(
            item_mod,
            derives,
            type_substitutes,
            crate_path,
            should_gen_docs,
        )
    } else {
        generator.generate_runtime(
            item_mod,
            derives,
            type_substitutes,
            crate_path,
            should_gen_docs,
        )
    }
}

/// Create the API for interacting with a Substrate runtime.
pub struct RuntimeGenerator {
    metadata: Metadata,
}

impl RuntimeGenerator {
    /// Create a new runtime generator from the provided metadata.
    ///
    /// **Note:** If you have the metadata path, URL or bytes to hand, prefer to use
    /// `GenerateRuntimeApi` for generating the runtime API from that.
    ///
    /// # Panics
    ///
    /// Panics if the runtime metadata version is not supported.
    ///
    /// Supported versions: v14 and v15.
    pub fn new(mut metadata: Metadata) -> Self {
        Self::ensure_unique_type_paths(&mut metadata);
        RuntimeGenerator { metadata }
    }

    /// Ensure that every unique type we'll be generating or referring to also has a
    /// unique path, so that types with matching paths don't end up overwriting each other
    /// in the codegen. We ignore any types with generics; Subxt actually endeavours to
    /// de-duplicate those into single types with a generic.
    fn ensure_unique_type_paths(metadata: &mut Metadata) {
        let mut visited_path_counts = HashMap::<Vec<String>, usize>::new();
        for ty in metadata.types_mut().types.iter_mut() {
            // Ignore types without a path (ie prelude types).
            if ty.ty.path.namespace().is_empty() {
                continue;
            }

            let has_valid_type_params = ty.ty.type_params.iter().any(|tp| tp.ty.is_some());

            // Ignore types which have generic params that the type generation will use.
            // Ordinarily we'd expect that any two types with identical paths must be parameterized
            // in order to share the path. However scale-info doesn't understand all forms of generics
            // properly I think (eg generics that have associated types that can differ), and so in
            // those cases we need to fix the paths for Subxt to generate correct code.
            if has_valid_type_params {
                continue;
            }

            // Count how many times we've seen the same path already.
            let visited_count = visited_path_counts
                .entry(ty.ty.path.segments.clone())
                .or_default();
            *visited_count += 1;

            // alter the type so that if it's been seen more than once, we append a number to
            // its name to ensure that every unique type has a unique path, too.
            if *visited_count > 1 {
                if let Some(name) = ty.ty.path.segments.last_mut() {
                    *name = format!("{name}{visited_count}");
                }
            }
        }
    }

    /// Generate the API for interacting with a Substrate runtime.
    ///
    /// # Arguments
    ///
    /// * `item_mod` - The module declaration for which the API is implemented.
    /// * `derives` - Provide custom derives for the generated types.
    /// * `type_substitutes` - Provide custom type substitutes.
    /// * `crate_path` - Path to the `subxt` crate.
    /// * `should_gen_docs` - True if the generated API contains the documentation from the metadata.
    pub fn generate_runtime_types(
        &self,
        item_mod: syn::ItemMod,
        derives: DerivesRegistry,
        type_substitutes: TypeSubstitutes,
        crate_path: CratePath,
        should_gen_docs: bool,
    ) -> Result<TokenStream2, CodegenError> {
        let item_mod_attrs = item_mod.attrs.clone();

        let item_mod_ir = ir::ItemMod::try_from(item_mod)?;
        let mod_ident = &item_mod_ir.ident;
        let rust_items = item_mod_ir.rust_items();

        let type_gen = TypeGenerator::new(
            self.metadata.types(),
            "runtime_types",
            type_substitutes,
            derives,
            crate_path,
            should_gen_docs,
        );
        let types_mod = type_gen.generate_types_mod()?;

        Ok(quote! {
            #( #item_mod_attrs )*
            #[allow(dead_code, unused_imports, non_camel_case_types)]
            #[allow(clippy::all)]
            #[allow(rustdoc::broken_intra_doc_links)]
            pub mod #mod_ident {
                // Preserve any Rust items that were previously defined in the adorned module
                #( #rust_items ) *

                // Make it easy to access the root items via `root_mod` at different levels
                // without reaching out of this module.
                #[allow(unused_imports)]
                mod root_mod {
                    pub use super::*;
                }

                #types_mod
            }
        })
    }

    /// Generate the API for interacting with a Substrate runtime.
    ///
    /// # Arguments
    ///
    /// * `item_mod` - The module declaration for which the API is implemented.
    /// * `derives` - Provide custom derives for the generated types.
    /// * `type_substitutes` - Provide custom type substitutes.
    /// * `crate_path` - Path to the `subxt` crate.
    /// * `should_gen_docs` - True if the generated API contains the documentation from the metadata.
    pub fn generate_runtime(
        &self,
        item_mod: syn::ItemMod,
        derives: DerivesRegistry,
        type_substitutes: TypeSubstitutes,
        crate_path: CratePath,
        should_gen_docs: bool,
    ) -> Result<TokenStream2, CodegenError> {
        let item_mod_attrs = item_mod.attrs.clone();
        let item_mod_ir = ir::ItemMod::try_from(item_mod)?;

        let type_gen = TypeGenerator::new(
            self.metadata.types(),
            "runtime_types",
            type_substitutes,
            derives,
            crate_path.clone(),
            should_gen_docs,
        );
        let types_mod = type_gen.generate_types_mod()?;
        let types_mod_ident = types_mod.ident();
        let pallets_with_mod_names = self
            .metadata
            .pallets()
            .map(|pallet| {
                (
                    pallet,
                    format_ident!("{}", pallet.name().to_string().to_snake_case()),
                )
            })
            .collect::<Vec<_>>();

        // Pallet names and their length are used to create PALLETS array.
        // The array is used to identify the pallets composing the metadata for
        // validation of just those pallets.
        let pallet_names: Vec<_> = self
            .metadata
            .pallets()
            .map(|pallet| pallet.name())
            .collect();
        let pallet_names_len = pallet_names.len();

        let runtime_api_names: Vec<_> = self
            .metadata
            .runtime_api_traits()
            .map(|api| api.name().to_string())
            .collect();
        let runtime_api_names_len = runtime_api_names.len();

        let metadata_hash = self.metadata.hasher().hash();

        let modules = pallets_with_mod_names
            .iter()
            .map(|(pallet, mod_name)| {
                let calls = calls::generate_calls(
                    &type_gen,
                    pallet,
                    types_mod_ident,
                    &crate_path,
                    should_gen_docs,
                )?;

                let event = events::generate_events(
                    &type_gen,
                    pallet,
                    types_mod_ident,
                    &crate_path,
                    should_gen_docs,
                )?;

                let storage_mod = storage::generate_storage(
                    &type_gen,
                    pallet,
                    types_mod_ident,
                    &crate_path,
                    should_gen_docs,
                )?;

                let constants_mod = constants::generate_constants(
                    &type_gen,
                    pallet,
                    types_mod_ident,
                    &crate_path,
                    should_gen_docs,
                )?;

                let errors = errors::generate_error_type_alias(&type_gen, pallet, should_gen_docs)?;

                Ok(quote! {
                    pub mod #mod_name {
                        use super::root_mod;
                        use super::#types_mod_ident;
                        #errors
                        #calls
                        #event
                        #storage_mod
                        #constants_mod
                    }
                })
            })
            .collect::<Result<Vec<_>, CodegenError>>()?;

        let mod_ident = &item_mod_ir.ident;
        let pallets_with_constants: Vec<_> = pallets_with_mod_names
            .iter()
            .filter_map(|(pallet, pallet_mod_name)| {
                pallet
                    .constants()
                    .next()
                    .is_some()
                    .then_some(pallet_mod_name)
            })
            .collect();

        let pallets_with_storage: Vec<_> = pallets_with_mod_names
            .iter()
            .filter_map(|(pallet, pallet_mod_name)| pallet.storage().map(|_| pallet_mod_name))
            .collect();

        let pallets_with_calls: Vec<_> = pallets_with_mod_names
            .iter()
            .filter_map(|(pallet, pallet_mod_name)| pallet.call_ty_id().map(|_| pallet_mod_name))
            .collect();

        let rust_items = item_mod_ir.rust_items();

        let apis_mod = runtime_apis::generate_runtime_apis(
            &self.metadata,
            &type_gen,
            types_mod_ident,
            &crate_path,
            should_gen_docs,
        )?;

        // Fetch the paths of the outer enums.
        // Substrate exposes those under `kitchensink_runtime`, while Polkadot under `polkadot_runtime`.
        let call_path = type_gen.resolve_type_path(self.metadata.outer_enums().call_enum_ty());
        let event_path = type_gen.resolve_type_path(self.metadata.outer_enums().event_enum_ty());
        let error_path = type_gen.resolve_type_path(self.metadata.outer_enums().error_enum_ty());

        let custom_values = generate_custom_values(&self.metadata, &type_gen, &crate_path);

        Ok(quote! {
            #( #item_mod_attrs )*
            #[allow(dead_code, unused_imports, non_camel_case_types)]
            #[allow(clippy::all)]
            #[allow(rustdoc::broken_intra_doc_links)]
            pub mod #mod_ident {
                // Preserve any Rust items that were previously defined in the adorned module.
                #( #rust_items ) *

                // Make it easy to access the root items via `root_mod` at different levels
                // without reaching out of this module.
                #[allow(unused_imports)]
                mod root_mod {
                    pub use super::*;
                }

                // Identify the pallets composing the static metadata by name.
                pub static PALLETS: [&str; #pallet_names_len] = [ #(#pallet_names,)* ];

                // Runtime APIs in the metadata by name.
                pub static RUNTIME_APIS: [&str; #runtime_api_names_len] = [ #(#runtime_api_names,)* ];

                /// The error type returned when there is a runtime issue.
                pub type DispatchError = #types_mod_ident::sp_runtime::DispatchError;

                /// The outer event enum.
                pub type Event = #event_path;

                /// The outer extrinsic enum.
                pub type Call = #call_path;

                /// The outer error enum representing the DispatchError's Module variant.
                pub type Error = #error_path;

                pub fn constants() -> ConstantsApi {
                    ConstantsApi
                }

                pub fn storage() -> StorageApi {
                    StorageApi
                }

                pub fn tx() -> TransactionApi {
                    TransactionApi
                }

                pub fn apis() -> runtime_apis::RuntimeApi {
                    runtime_apis::RuntimeApi
                }

                #apis_mod

                pub fn custom() -> CustomValuesApi {
                    CustomValuesApi
                }

                #custom_values

                pub struct ConstantsApi;
                impl ConstantsApi {
                    #(
                        pub fn #pallets_with_constants(&self) -> #pallets_with_constants::constants::ConstantsApi {
                            #pallets_with_constants::constants::ConstantsApi
                        }
                    )*
                }

                pub struct StorageApi;
                impl StorageApi {
                    #(
                        pub fn #pallets_with_storage(&self) -> #pallets_with_storage::storage::StorageApi {
                            #pallets_with_storage::storage::StorageApi
                        }
                    )*
                }

                pub struct TransactionApi;
                impl TransactionApi {
                    #(
                        pub fn #pallets_with_calls(&self) -> #pallets_with_calls::calls::TransactionApi {
                            #pallets_with_calls::calls::TransactionApi
                        }
                    )*
                }

                /// check whether the metadata provided is aligned with this statically generated code.
                pub fn is_codegen_valid_for(metadata: &#crate_path::Metadata) -> bool {
                    let runtime_metadata_hash = metadata
                        .hasher()
                        .only_these_pallets(&PALLETS)
                        .only_these_runtime_apis(&RUNTIME_APIS)
                        .hash();
                    runtime_metadata_hash == [ #(#metadata_hash,)* ]
                }

                #( #modules )*
                #types_mod
            }
        })
    }
}

/// Return a vector of tuples of variant names and corresponding struct definitions.
pub fn generate_structs_from_variants<F>(
    type_gen: &TypeGenerator,
    type_id: u32,
    variant_to_struct_name: F,
    error_message_type_name: &str,
    crate_path: &CratePath,
    should_gen_docs: bool,
) -> Result<Vec<(String, CompositeDef)>, CodegenError>
where
    F: Fn(&str) -> std::borrow::Cow<str>,
{
    let ty = type_gen.resolve_type(type_id);

    let scale_info::TypeDef::Variant(variant) = &ty.type_def else {
        return Err(CodegenError::InvalidType(error_message_type_name.into()));
    };

    variant
        .variants
        .iter()
        .map(|var| {
            let struct_name = variant_to_struct_name(&var.name);

            let fields = CompositeDefFields::from_scale_info_fields(
                struct_name.as_ref(),
                &var.fields,
                &[],
                type_gen,
            )?;

            let docs = should_gen_docs.then_some(&*var.docs).unwrap_or_default();
            let struct_def = CompositeDef::struct_def(
                &ty,
                struct_name.as_ref(),
                Default::default(),
                fields,
                Some(parse_quote!(pub)),
                type_gen,
                docs,
                crate_path,
            )?;

            Ok((var.name.to_string(), struct_def))
        })
        .collect()
}