// Copyright 2024 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

use std::{borrow::Cow, path::Path};

use codec::Decode;
use polkadot_sdk::{
    sc_executor::{self, WasmExecutionMethod, WasmExecutor},
    sc_executor_common::runtime_blob::RuntimeBlob,
    sp_io,
    sp_maybe_compressed_blob::{self, CODE_BLOB_BOMB_LIMIT},
    sp_state_machine,
};
use subxt_codegen::{fetch_metadata::fetch_metadata_from_file_blocking, CodegenError, Metadata};

/// Result type shorthand
pub type WasmMetadataResult<A> = Result<A, CodegenError>;

/// Uses wasm artifact produced by compiling the runtime to generate metadata
pub fn from_wasm_file(wasm_file_path: &Path) -> WasmMetadataResult<Metadata> {
    let wasm_file = fetch_metadata_from_file_blocking(wasm_file_path)
        .map_err(Into::<CodegenError>::into)
        .and_then(maybe_decompress)?;
    call_and_decode(wasm_file)
}

fn call_and_decode(wasm_file: Vec<u8>) -> WasmMetadataResult<Metadata> {
    let mut ext: sp_state_machine::BasicExternalities = Default::default();

    let executor: WasmExecutor<sp_io::SubstrateHostFunctions> = WasmExecutor::builder()
        .with_execution_method(WasmExecutionMethod::default())
        .with_offchain_heap_alloc_strategy(sc_executor::HeapAllocStrategy::Dynamic {
            maximum_pages: Some(64),
        })
        .with_max_runtime_instances(1)
        .with_runtime_cache_size(1)
        .build();

    let runtime_blob =
        RuntimeBlob::new(&wasm_file).map_err(|e| CodegenError::Wasm(e.to_string()))?;
    let metadata_encoded = executor
        .uncached_call(runtime_blob, &mut ext, true, "Metadata_metadata", &[])
        .map_err(|_| CodegenError::Wasm("method \"Metadata_metadata\" doesnt exist".to_owned()))?;

    let metadata = <Vec<u8>>::decode(&mut &metadata_encoded[..]).map_err(CodegenError::Decode)?;

    decode(metadata)
}

fn decode(encoded_metadata: Vec<u8>) -> WasmMetadataResult<Metadata> {
    Metadata::decode(&mut encoded_metadata.as_ref()).map_err(Into::into)
}

fn maybe_decompress(file_contents: Vec<u8>) -> WasmMetadataResult<Vec<u8>> {
    sp_maybe_compressed_blob::decompress(file_contents.as_ref(), CODE_BLOB_BOMB_LIMIT)
        .map_err(|e| CodegenError::Wasm(e.to_string()))
        .map(Cow::into_owned)
}