// Copyright 2017-2019 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Substrate is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

#[doc(hidden)]
pub use rstd;
pub use rstd::{mem, slice};

use core::{intrinsics, panic::PanicInfo};
use rstd::{vec::Vec, cell::Cell};
use primitives::Blake2Hasher;

#[cfg(not(feature = "no_panic_handler"))]
#[panic_handler]
#[no_mangle]
pub fn panic(info: &PanicInfo) -> ! {
	unsafe {
		#[cfg(feature = "wasm-nice-panic-message")]
		{
			let message = rstd::alloc::format!("{}", info);
			extern_functions_host_impl::ext_print_utf8(message.as_ptr() as *const u8, message.len() as u32);
		}
		#[cfg(not(feature = "wasm-nice-panic-message"))]
		{
			if let Some(loc) = info.location() {
				extern_functions_host_impl::ext_print_utf8(loc.file().as_ptr() as *const u8, loc.file().len() as u32);
				extern_functions_host_impl::ext_print_num(loc.line() as u64);
				extern_functions_host_impl::ext_print_num(loc.column() as u64);
			}
		}
		intrinsics::abort()
	}
}

#[cfg(not(feature = "no_oom"))]
#[alloc_error_handler]
pub extern fn oom(_: ::core::alloc::Layout) -> ! {
	static OOM_MSG: &str = "Runtime memory exhausted. Aborting";

	unsafe {
		extern_functions_host_impl::ext_print_utf8(OOM_MSG.as_ptr(), OOM_MSG.len() as u32);
		intrinsics::abort();
	}
}

/// External (Host) APIs
pub mod ext {
	use super::*;

	/// The state of an exchangeable function.
	#[derive(Clone, Copy)]
	enum ExchangeableFunctionState {
		/// Original function is present
		Original,
		/// The function has been replaced.
		Replaced,
	}

	/// A function which implementation can be exchanged.
	///
	/// Internally this works by swapping function pointers.
	pub struct ExchangeableFunction<T>(Cell<(T, ExchangeableFunctionState)>);

	impl<T> ExchangeableFunction<T> {
		/// Create a new instance of `ExchangeableFunction`.
		pub const fn new(impl_: T) -> Self {
			Self(Cell::new((impl_, ExchangeableFunctionState::Original)))
		}
	}

	impl<T: Copy> ExchangeableFunction<T> {
		/// Replace the implementation with `new_impl`.
		///
		/// # Panics
		///
		/// Panics when trying to replace an already replaced implementation.
		///
		/// # Returns
		///
		/// Returns the original implementation wrapped in [`RestoreImplementation`].
		pub fn replace_implementation(&'static self, new_impl: T)  -> RestoreImplementation<T> {
			if let ExchangeableFunctionState::Replaced = self.0.get().1 {
				panic!("Trying to replace an already replaced implementation!")
			}

			let old = self.0.replace((new_impl, ExchangeableFunctionState::Replaced));

			RestoreImplementation(self, Some(old.0))
		}

		/// Restore the original implementation.
		fn restore_orig_implementation(&self, orig: T) {
			self.0.set((orig, ExchangeableFunctionState::Original));
		}

		/// Returns the internal function pointer.
		pub fn get(&self) -> T {
			self.0.get().0
		}
	}

	// WASM does not support threads, so this is safe; qed.
	unsafe impl<T> Sync for ExchangeableFunction<T> {}

	/// Restores a function implementation on drop.
	///
	/// Stores a static reference to the function object and the original implementation.
	pub struct RestoreImplementation<T: 'static + Copy>(&'static ExchangeableFunction<T>, Option<T>);

	impl<T: Copy> Drop for RestoreImplementation<T> {
		fn drop(&mut self) {
			self.0.restore_orig_implementation(self.1.take().expect("Value is only taken on drop; qed"));
		}
	}

	/// Ensures we use the right crypto when calling into native
	pub trait ExternTrieCrypto: Hasher {
		/// Calculate enumerated trie root.
		fn enumerated_trie_root(values: &[&[u8]]) -> Self::Out;
	}

	/// Additional bounds for Hasher trait for without_std.
	pub trait HasherBounds: ExternTrieCrypto {}
	impl<T: ExternTrieCrypto + Hasher> HasherBounds for T {}

	// Ensures we use a Blake2_256-flavored Hasher when calling into native
	impl ExternTrieCrypto for Blake2Hasher {
		fn enumerated_trie_root(values: &[&[u8]]) -> Self::Out {
			let lengths = values.iter().map(|v| (v.len() as u32).to_le()).collect::<Vec<_>>();
			let values = values.iter().fold(Vec::new(), |mut acc, sl| { acc.extend_from_slice(sl); acc });
			let mut result: [u8; 32] = Default::default();
			unsafe {
				ext_blake2_256_enumerated_trie_root.get()(
					values.as_ptr(),
					lengths.as_ptr(),
					lengths.len() as u32,
					result.as_mut_ptr()
				);
			}
			result.into()
		}
	}

	/// Declare extern functions
	macro_rules! extern_functions {
		(
			$(
				$( #[$attr:meta] )*
				fn $name:ident ( $( $arg:ident : $arg_ty:ty ),* ) $( -> $ret:ty )?;
			)*
		) => {
			$(
				$( #[$attr] )*
				#[allow(non_upper_case_globals)]
				pub static $name: ExchangeableFunction<unsafe fn ( $( $arg_ty ),* ) $( -> $ret )?> =
					ExchangeableFunction::new(extern_functions_host_impl::$name);
			)*

			/// The exchangeable extern functions host implementations.
			pub(crate) mod extern_functions_host_impl {
				$(
					pub unsafe fn $name ( $( $arg : $arg_ty ),* ) $( -> $ret )? {
						implementation::$name ( $( $arg ),* )
					}
				)*

				mod implementation {
					extern "C" {
						$(
							pub fn $name ( $( $arg : $arg_ty ),* ) $( -> $ret )?;
						)*
					}
				}
			}
		};
	}

	/// Host functions, provided by the executor.
	/// A WebAssembly runtime module would "import" these to access the execution environment
	/// (most importantly, storage) or perform heavy hash calculations.
	/// See also "ext_" functions in sr-sandbox and sr-std
	extern_functions! {
		/// Host functions for printing, useful for debugging.
		fn ext_print_utf8(utf8_data: *const u8, utf8_len: u32);
		/// Print data as hex.
		fn ext_print_hex(data: *const u8, len: u32);
		/// Print a number
		fn ext_print_num(value: u64);

		/// Set value for key in storage.
		fn ext_set_storage(key_data: *const u8, key_len: u32, value_data: *const u8, value_len: u32);
		/// Remove key and value from storage.
		fn ext_clear_storage(key_data: *const u8, key_len: u32);
		/// Checks if the given key exists in the storage.
		///
		/// # Returns
		///
		/// - `1` if the value exists.
		/// - `0` if the value does not exists.
		fn ext_exists_storage(key_data: *const u8, key_len: u32) -> u32;
		/// Remove storage entries which key starts with given prefix.
		fn ext_clear_prefix(prefix_data: *const u8, prefix_len: u32);
		/// Gets the value of the given key from storage.
		///
		/// The host allocates the memory for storing the value.
		///
		/// # Returns
		///
		/// - `0` if no value exists to the given key. `written_out` is set to `u32::max_value()`.
		///
		/// - Otherwise, pointer to the value in memory. `written_out` contains the length of the value.
		fn ext_get_allocated_storage(key_data: *const u8, key_len: u32, written_out: *mut u32) -> *mut u8;
		/// Gets the value of the given key from storage.
		///
		/// The value is written into `value` starting at `value_offset`.
		///
		/// If the value length is greater than `value_len - value_offset`, the value is written partially.
		///
		/// # Returns
		///
		/// - `u32::max_value()` if the value does not exists.
		///
		/// - Otherwise, the number of bytes written for value.
		fn ext_get_storage_into(key_data: *const u8, key_len: u32, value_data: *mut u8, value_len: u32, value_offset: u32) -> u32;
		/// Gets the trie root of the storage.
		fn ext_storage_root(result: *mut u8);
		/// Get the change trie root of the current storage overlay at a block with given parent.
		///
		/// # Returns
		///
		/// - `1` if the change trie root was found.
		/// - `0` if the change trie root was not found.
		fn ext_storage_changes_root(parent_hash_data: *const u8, parent_hash_len: u32, result: *mut u8) -> u32;

		/// A child storage function.
		///
		/// See [`ext_set_storage`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_set_child_storage(storage_key_data: *const u8, storage_key_len: u32, key_data: *const u8, key_len: u32, value_data: *const u8, value_len: u32);
		/// A child storage function.
		///
		/// See [`ext_clear_storage`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_clear_child_storage(storage_key_data: *const u8, storage_key_len: u32, key_data: *const u8, key_len: u32);
		/// A child storage function.
		///
		/// See [`ext_exists_storage`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_exists_child_storage(storage_key_data: *const u8, storage_key_len: u32, key_data: *const u8, key_len: u32) -> u32;
		/// A child storage function.
		///
		/// See [`ext_kill_storage`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_kill_child_storage(storage_key_data: *const u8, storage_key_len: u32);
		/// A child storage function.
		///
		/// See [`ext_get_allocated_storage`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_get_allocated_child_storage(
			storage_key_data: *const u8,
			storage_key_len: u32,
			key_data: *const u8,
			key_len: u32,
			written_out: *mut u32
		) -> *mut u8;
		/// A child storage function.
		///
		/// See [`ext_get_storage_into`] for details.
		///
		/// A child storage is used e.g. by a contract.
		fn ext_get_child_storage_into(
			storage_key_data: *const u8,
			storage_key_len: u32,
			key_data: *const u8,
			key_len: u32,
			value_data: *mut u8,
			value_len: u32,
			value_offset: u32
		) -> u32;
		/// Commits all changes and calculates the child-storage root.
		///
		/// A child storage is used e.g. by a contract.
		///
		/// # Returns
		///
		/// - The pointer to the result vector and `written_out` contains its length.
		fn ext_child_storage_root(storage_key_data: *const u8, storage_key_len: u32, written_out: *mut u32) -> *mut u8;

		/// The current relay chain identifier.
		fn ext_chain_id() -> u64;

		/// Calculate a blake2_256 merkle trie root.
		fn ext_blake2_256_enumerated_trie_root(values_data: *const u8, lens_data: *const u32, lens_len: u32, result: *mut u8);
		/// BLAKE2_128 hash
		fn ext_blake2_128(data: *const u8, len: u32, out: *mut u8);
		/// BLAKE2_256 hash
		fn ext_blake2_256(data: *const u8, len: u32, out: *mut u8);
		/// XX64 hash
		fn ext_twox_64(data: *const u8, len: u32, out: *mut u8);
		/// XX128 hash
		fn ext_twox_128(data: *const u8, len: u32, out: *mut u8);
		/// XX256 hash
		fn ext_twox_256(data: *const u8, len: u32, out: *mut u8);
		/// Keccak256 hash
		fn ext_keccak_256(data: *const u8, len: u32, out: *mut u8);
		/// Note: ext_ed25519_verify returns 0 if the signature is correct, nonzero otherwise.
		fn ext_ed25519_verify(msg_data: *const u8, msg_len: u32, sig_data: *const u8, pubkey_data: *const u8) -> u32;
		/// Note: ext_sr25519_verify returns 0 if the signature is correct, nonzero otherwise.
		fn ext_sr25519_verify(msg_data: *const u8, msg_len: u32, sig_data: *const u8, pubkey_data: *const u8) -> u32;
		/// Note: ext_secp256k1_ecdsa_recover returns 0 if the signature is correct, nonzero otherwise.
		fn ext_secp256k1_ecdsa_recover(msg_data: *const u8, sig_data: *const u8, pubkey_data: *mut u8) -> u32;

		//================================
		// Offchain-worker Context
		//================================

		/// Submit extrinsic.
		fn ext_submit_extrinsic(data: *const u8, len: u32);
	}
}

pub use self::ext::*;

impl StorageApi for () {
	fn storage(key: &[u8]) -> Option<Vec<u8>> {
		let mut length: u32 = 0;
		unsafe {
			let ptr = ext_get_allocated_storage.get()(key.as_ptr(), key.len() as u32, &mut length);
			if length == u32::max_value() {
				None
			} else {
				// Invariants required by Vec::from_raw_parts are not formally fulfilled.
				// We don't allocate via String/Vec<T>, but use a custom allocator instead.
				// See #300 for more details.
				Some(<Vec<u8>>::from_raw_parts(ptr, length as usize, length as usize))
			}
		}
	}

	fn child_storage(storage_key: &[u8], key: &[u8]) -> Option<Vec<u8>> {
		let mut length: u32 = 0;
		unsafe {
			let ptr = ext_get_allocated_child_storage.get()(
				storage_key.as_ptr(),
				storage_key.len() as u32,
				key.as_ptr(),
				key.len() as u32,
				&mut length
			);
			if length == u32::max_value() {
				None
			} else {
				// Invariants required by Vec::from_raw_parts are not formally fulfilled.
				// We don't allocate via String/Vec<T>, but use a custom allocator instead.
				// See #300 for more details.
				Some(<Vec<u8>>::from_raw_parts(ptr, length as usize, length as usize))
			}
		}
	}

	fn read_storage(key: &[u8], value_out: &mut [u8], value_offset: usize) -> Option<usize> {
		unsafe {
			match ext_get_storage_into.get()(
				key.as_ptr(),
				key.len() as u32,
				value_out.as_mut_ptr(),
				value_out.len() as u32,
				value_offset as u32,
			) {
				none if none == u32::max_value() => None,
				length => Some(length as usize),
			}
		}
	}

	fn read_child_storage(storage_key: &[u8], key: &[u8], value_out: &mut [u8], value_offset: usize) -> Option<usize> {
		unsafe {
			match ext_get_child_storage_into.get()(
				storage_key.as_ptr(), storage_key.len() as u32,
				key.as_ptr(), key.len() as u32,
				value_out.as_mut_ptr(), value_out.len() as u32,
				value_offset as u32
			) {
				none if none == u32::max_value() => None,
				length => Some(length as usize),
			}
		}
	}

	fn set_storage(key: &[u8], value: &[u8]) {
		unsafe {
			ext_set_storage.get()(
				key.as_ptr(), key.len() as u32,
				value.as_ptr(), value.len() as u32
			);
		}
	}

	fn set_child_storage(storage_key: &[u8], key: &[u8], value: &[u8]) {
		unsafe {
			ext_set_child_storage.get()(
				storage_key.as_ptr(), storage_key.len() as u32,
				key.as_ptr(), key.len() as u32,
				value.as_ptr(), value.len() as u32
			);
		}
	}

	fn clear_storage(key: &[u8]) {
		unsafe {
			ext_clear_storage.get()(
				key.as_ptr(), key.len() as u32
			);
		}
	}

	fn clear_child_storage(storage_key: &[u8], key: &[u8]) {
		unsafe {
			ext_clear_child_storage.get()(
				storage_key.as_ptr(), storage_key.len() as u32,
				key.as_ptr(), key.len() as u32
			);
		}
	}

	fn exists_storage(key: &[u8]) -> bool {
		unsafe {
			ext_exists_storage.get()(
				key.as_ptr(), key.len() as u32
			) != 0
		}
	}

	fn exists_child_storage(storage_key: &[u8], key: &[u8]) -> bool {
		unsafe {
			ext_exists_child_storage.get()(
				storage_key.as_ptr(), storage_key.len() as u32,
				key.as_ptr(), key.len() as u32
			) != 0
		}
	}

	fn clear_prefix(prefix: &[u8]) {
		unsafe {
			ext_clear_prefix.get()(
				prefix.as_ptr(),
				prefix.len() as u32
			);
		}
	}

	fn kill_child_storage(storage_key: &[u8]) {
		unsafe {
			ext_kill_child_storage.get()(
				storage_key.as_ptr(),
				storage_key.len() as u32
			);
		}
	}

	fn storage_root() -> [u8; 32] {
		let mut result: [u8; 32] = Default::default();
		unsafe {
			ext_storage_root.get()(result.as_mut_ptr());
		}
		result
	}

	fn child_storage_root(storage_key: &[u8]) -> Vec<u8> {
		let mut length: u32 = 0;
		unsafe {
			let ptr = ext_child_storage_root.get()(
				storage_key.as_ptr(),
				storage_key.len() as u32,
				&mut length
			);
			// Invariants required by Vec::from_raw_parts are not formally fulfilled.
			// We don't allocate via String/Vec<T>, but use a custom allocator instead.
			// See #300 for more details.
			<Vec<u8>>::from_raw_parts(ptr, length as usize, length as usize)
		}
	}

	fn storage_changes_root(parent_hash: [u8; 32]) -> Option<[u8; 32]> {
		let mut result: [u8; 32] = Default::default();
		let is_set = unsafe {
			ext_storage_changes_root.get()(parent_hash.as_ptr(), parent_hash.len() as u32, result.as_mut_ptr())
		};

		if is_set != 0 {
			Some(result)
		} else {
			None
		}
	}

	fn enumerated_trie_root<H: Hasher + ExternTrieCrypto>(values: &[&[u8]]) -> H::Out {
		H::enumerated_trie_root(values)
	}

	fn trie_root<
		H: Hasher + ExternTrieCrypto,
		I: IntoIterator<Item = (A, B)>,
		A: AsRef<[u8]> + Ord,
		B: AsRef<[u8]>,
	>(_input: I) -> H::Out {
		unimplemented!()
	}

	fn ordered_trie_root<
		H: Hasher + ExternTrieCrypto,
		I: IntoIterator<Item = A>,
		A: AsRef<[u8]>
	>(_input: I) -> H::Out {
		unimplemented!()
	}
}

impl OtherApi for () {
	fn chain_id() -> u64 {
		unsafe {
			ext_chain_id.get()()
		}
	}

	fn print<T: Printable + Sized>(value: T) {
		value.print()
	}

}

impl HashingApi for () {
	fn keccak_256(data: &[u8]) -> [u8; 32] {
		let mut result: [u8; 32] = Default::default();
		unsafe {
			ext_keccak_256.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}

	fn blake2_128(data: &[u8]) -> [u8; 16] {
		let mut result: [u8; 16] = Default::default();
		unsafe {
			ext_blake2_128.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}

	fn blake2_256(data: &[u8]) -> [u8; 32] {
		let mut result: [u8; 32] = Default::default();
		unsafe {
			ext_blake2_256.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}

	fn twox_256(data: &[u8]) -> [u8; 32] {
		let mut result: [u8; 32] = Default::default();
		unsafe {
			ext_twox_256.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}

	fn twox_128(data: &[u8]) -> [u8; 16] {
		let mut result: [u8; 16] = Default::default();
		unsafe {
			ext_twox_128.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}

	fn twox_64(data: &[u8]) -> [u8; 8] {
		let mut result: [u8; 8] = Default::default();
		unsafe {
			ext_twox_64.get()(data.as_ptr(), data.len() as u32, result.as_mut_ptr());
		}
		result
	}
}

impl CryptoApi for () {
	fn ed25519_verify<P: AsRef<[u8]>>(sig: &[u8; 64], msg: &[u8], pubkey: P) -> bool {
		unsafe {
			ext_ed25519_verify.get()(msg.as_ptr(), msg.len() as u32, sig.as_ptr(), pubkey.as_ref().as_ptr()) == 0
		}
	}

	fn sr25519_verify<P: AsRef<[u8]>>(sig: &[u8; 64], msg: &[u8], pubkey: P) -> bool {
		unsafe {
			ext_sr25519_verify.get()(msg.as_ptr(), msg.len() as u32, sig.as_ptr(), pubkey.as_ref().as_ptr()) == 0
		}
	}

	fn secp256k1_ecdsa_recover(sig: &[u8; 65], msg: &[u8; 32]) -> Result<[u8; 64], EcdsaVerifyError> {
		let mut pubkey = [0u8; 64];
		match unsafe {
			ext_secp256k1_ecdsa_recover.get()(msg.as_ptr(), sig.as_ptr(), pubkey.as_mut_ptr())
		} {
			0 => Ok(pubkey),
			1 => Err(EcdsaVerifyError::BadRS),
			2 => Err(EcdsaVerifyError::BadV),
			3 => Err(EcdsaVerifyError::BadSignature),
			_ => unreachable!("`ext_secp256k1_ecdsa_recover` only returns 0, 1, 2 or 3; qed"),
		}
	}
}

impl OffchainApi for () {
	fn submit_extrinsic<T: codec::Encode>(data: &T) {
		let encoded_data = codec::Encode::encode(data);
		unsafe {
			ext_submit_extrinsic.get()(encoded_data.as_ptr(), encoded_data.len() as u32)
		}
	}
}

impl Api for () {}

impl<'a> Printable for &'a [u8] {
	fn print(self) {
		unsafe {
			ext_print_hex.get()(self.as_ptr(), self.len() as u32);
		}
	}
}

impl<'a> Printable for &'a str {
	fn print(self) {
		unsafe {
			ext_print_utf8.get()(self.as_ptr() as *const u8, self.len() as u32);
		}
	}
}

impl Printable for u64 {
	fn print(self) {
		unsafe { ext_print_num.get()(self); }
	}
}