// Copyright (C) Parity Technologies (UK) Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Types for the default environment.
//!
//! These are simple mirrored types from the default substrate FRAME configuration.
//! Their interfaces and functionality might not be complete.
//!
//! Users are required to provide their own type definitions and `Environment`
//! implementations in order to write ink! contracts for other chain configurations.
//!
//! # Note
//!
//! When authoring a contract, the concrete `Environment` are available via aliases
//! generated by the `lang` macro. Therefore all functionality of the concrete
//! types is accessible in the contract, not constrained by the required trait
//! bounds.
//!
//! Outside the contract and its tests (e.g. in the off-chain environment), where
//! there is no knowledge of the concrete types, the functionality is restricted to
//! the trait bounds on the `Environment` trait types.

use super::arithmetic::AtLeast32BitUnsigned;
use ink_primitives::{
    AccountId,
    Clear,
    Hash,
};
#[cfg(feature = "std")]
use scale_info::TypeInfo;

/// Allows to instantiate a type from its little-endian bytes representation.
pub trait FromLittleEndian {
    /// The little-endian bytes representation.
    type Bytes: Default + AsRef<[u8]> + AsMut<[u8]>;

    /// Create a new instance from the little-endian bytes representation.
    fn from_le_bytes(bytes: Self::Bytes) -> Self;
}

impl FromLittleEndian for u8 {
    type Bytes = [u8; 1];

    #[inline]
    fn from_le_bytes(bytes: Self::Bytes) -> Self {
        u8::from_le_bytes(bytes)
    }
}

impl FromLittleEndian for u16 {
    type Bytes = [u8; 2];

    #[inline]
    fn from_le_bytes(bytes: Self::Bytes) -> Self {
        u16::from_le_bytes(bytes)
    }
}

impl FromLittleEndian for u32 {
    type Bytes = [u8; 4];

    #[inline]
    fn from_le_bytes(bytes: Self::Bytes) -> Self {
        u32::from_le_bytes(bytes)
    }
}

impl FromLittleEndian for u64 {
    type Bytes = [u8; 8];

    #[inline]
    fn from_le_bytes(bytes: Self::Bytes) -> Self {
        u64::from_le_bytes(bytes)
    }
}

impl FromLittleEndian for u128 {
    type Bytes = [u8; 16];

    #[inline]
    fn from_le_bytes(bytes: Self::Bytes) -> Self {
        u128::from_le_bytes(bytes)
    }
}

/// A trait to enforce that a type should be an [`Environment::AccountId`].
///
/// If you have an [`Environment`] which uses an [`Environment::AccountId`] type other
/// than the ink! provided [`AccountId`](https://docs.rs/ink_primitives/latest/ink_primitives/struct.AccountId.html)
/// you will need to implement this trait for your [`Environment::AccountId`] concrete
/// type.
pub trait AccountIdGuard {}

/// The ink! provided [`AccountId`](https://docs.rs/ink_primitives/latest/ink_primitives/struct.AccountId.html)
/// used in the [`DefaultEnvironment`].
impl AccountIdGuard for AccountId {}

cfg_if::cfg_if! {
    if #[cfg(feature = "std")] {
        pub trait CodecAsType: scale_decode::DecodeAsType + scale_encode::EncodeAsType {}
        impl<T: scale_decode::DecodeAsType + scale_encode::EncodeAsType> CodecAsType for T {}
    } else {
        pub trait CodecAsType {}
        impl<T> CodecAsType for T {}
    }
}

/// The environmental types usable by contracts defined with ink!.
pub trait Environment: Clone {
    /// The maximum number of supported event topics provided by the runtime.
    ///
    /// The value must match the maximum number of supported event topics of the used
    /// runtime.
    const MAX_EVENT_TOPICS: usize;

    /// The account id type.
    type AccountId: 'static
        + scale::Codec
        + scale::MaxEncodedLen
        + CodecAsType
        + Clone
        + PartialEq
        + Eq
        + Ord
        + AsRef<[u8]>
        + AsMut<[u8]>;

    /// The type of balances.
    type Balance: 'static
        + scale::Codec
        + CodecAsType
        + Copy
        + Clone
        + PartialEq
        + Eq
        + AtLeast32BitUnsigned
        + FromLittleEndian;

    /// The type of hash.
    type Hash: 'static
        + scale::Codec
        + scale::MaxEncodedLen
        + CodecAsType
        + Copy
        + Clone
        + Clear
        + PartialEq
        + Eq
        + Ord
        + AsRef<[u8]>
        + AsMut<[u8]>;

    /// The type of a timestamp.
    type Timestamp: 'static
        + scale::Codec
        + CodecAsType
        + Copy
        + Clone
        + PartialEq
        + Eq
        + AtLeast32BitUnsigned
        + FromLittleEndian;

    /// The type of block number.
    type BlockNumber: 'static
        + scale::Codec
        + CodecAsType
        + Copy
        + Clone
        + PartialEq
        + Eq
        + AtLeast32BitUnsigned
        + FromLittleEndian;

    /// The chain extension for the environment.
    ///
    /// This is a type that is defined through the `#[ink::chain_extension]` procedural
    /// macro. For more information about usage and definition click
    /// [this][chain_extension] link.
    ///
    /// [chain_extension]: https://paritytech.github.io/ink/ink/attr.chain_extension.html
    type ChainExtension;
}

/// Placeholder for chains that have no defined chain extension.
#[cfg_attr(feature = "std", derive(TypeInfo))]
pub enum NoChainExtension {}

/// The fundamental types of the default configuration.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "std", derive(TypeInfo))]
pub enum DefaultEnvironment {}

impl Environment for DefaultEnvironment {
    const MAX_EVENT_TOPICS: usize = 4;

    type AccountId = AccountId;
    type Balance = Balance;
    type Hash = Hash;
    type Timestamp = Timestamp;
    type BlockNumber = BlockNumber;
    type ChainExtension = NoChainExtension;
}

/// The default balance type.
pub type Balance = u128;

/// The default timestamp type.
pub type Timestamp = u64;

/// The default gas type.
pub type Gas = u64;

/// The default block number type.
pub type BlockNumber = u32;