use crate::{

    StorageSlot,

    Transaction,

    ValidityError,

};

use derivative::Derivative;

use fuel_crypto::Hasher;

use fuel_merkle::{

    binary::root_calculator::MerkleRootCalculator as BinaryMerkleTree,

    sparse::{

        in_memory::MerkleTree as SparseMerkleTree,

        MerkleTreeKey,

    },

};

use fuel_types::{

    fmt_truncated_hex,

    Bytes32,

    ContractId,

    Salt,

};

use alloc::vec::Vec;

use core::iter;

/// The target size of Merkle tree leaves in bytes. Contract code will will be divided

/// into chunks of this size and pushed to the Merkle tree.

///

/// See https://github.com/FuelLabs/fuel-specs/blob/master/src/identifiers/contract-id.md

const LEAF_SIZE: usize = 16 * 1024;

/// In the event that contract code cannot be divided evenly by the `LEAF_SIZE`, the

/// remainder must be padded to the nearest multiple of 8 bytes. Padding is achieved by

/// repeating the `PADDING_BYTE`.

const PADDING_BYTE: u8 = 0u8;

const MULTIPLE: usize = 8;

#[derive(Default, Derivative, Clone, PartialEq, Eq, Hash)]

#[derivative(Debug)]

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]

#[derive(fuel_types::canonical::Deserialize, fuel_types::canonical::Serialize)]

/// Deployable representation of a contract code.

pub struct Contract(

    #[derivative(Debug(format_with = "fmt_truncated_hex::<16>"))] Vec<u8>,

);

impl Contract {

    /// The `ContractId` of the contract with empty bytecode, zero salt, and empty state

    /// root.

    pub const EMPTY_CONTRACT_ID: ContractId = ContractId::new([

        55, 187, 13, 108, 165, 51, 58, 230, 74, 109, 215, 229, 33, 69, 82, 120, 81, 4,

        85, 54, 172, 30, 84, 115, 226, 164, 0, 99, 103, 189, 154, 243,

    ]);

    /// Number of bytes in the contract's bytecode

    pub fn len(&self) -> usize {

        self.0.len()

    }

    /// Check if the contract's bytecode is empty

    pub fn is_empty(&self) -> bool {

        self.0.is_empty()

    }

    /// Calculate the code root of the contract, using [`Self::root_from_code`].

    pub fn root(&self) -> Bytes32 {

        Self::root_from_code(self)

    }

    /// Calculate the code root from a contract.

    ///

    /// <https://github.com/FuelLabs/fuel-specs/blob/master/src/identifiers/contract-id.md>

    pub fn root_from_code<B>(bytes: B) -> Bytes32

    where

        B: AsRef<[u8]>,

    {

        let mut tree = BinaryMerkleTree::new();

        bytes.as_ref().chunks(LEAF_SIZE).for_each(|leaf| {

            // If the bytecode is not a multiple of LEAF_SIZE, the final leaf

            // should be zero-padded rounding up to the nearest multiple of 8

            // bytes.

            let len = leaf.len();

            if len == LEAF_SIZE || 
len % MULTIPLE == 05.74k
 {

  Branch (82:16): [True: 26, False: 1.12k]
  Branch (82:36): [True: 62, False: 1.06k]
  Branch (82:16): [True: 8, False: 353]
  Branch (82:36): [True: 67, False: 286]
  Branch (82:16): [True: 0, False: 2.48k]
  Branch (82:36): [True: 2.37k, False: 117]

  Branch (82:16): [True: 0, False: 1.09k]
  Branch (82:36): [True: 419, False: 678]
  Branch (82:16): [True: 0, False: 634]
  Branch (82:36): [True: 315, False: 319]
  Branch (82:16): [True: 0, False: 46]
  Branch (82:36): [True: 19, False: 27]

                tree.push(leaf);

            } else {

                let padding_size = len.next_multiple_of(MULTIPLE);

                let mut padded_leaf = [PADDING_BYTE; LEAF_SIZE];

                padded_leaf[0..len].clone_from_slice(leaf);

                tree.push(padded_leaf[..padding_size].as_ref());

            }

        });

        tree.root().into()

    }

    /// Calculate the root of the initial storage slots for this contract

    pub fn initial_state_root<'a, I>(storage_slots: I) -> Bytes32

    where

        I: Iterator<Item = &'a StorageSlot>,

    {

        let storage_slots = storage_slots

            .map(|slot| (*slot.key(), slot.value()))

            .map(|(key, data)| (MerkleTreeKey::new(key), data));

        let root = SparseMerkleTree::root_from_set(storage_slots);

        root.into()

    }

    /// The default state root value without any entries

    pub fn default_state_root() -> Bytes32 {

        Self::initial_state_root(iter::empty())

    }

    /// Calculate and return the contract id, provided a salt, code root and state root.

    ///

    /// <https://github.com/FuelLabs/fuel-specs/blob/master/src/identifiers/contract-id.md>

    pub fn id(&self, salt: &Salt, root: &Bytes32, state_root: &Bytes32) -> ContractId {

        let mut hasher = Hasher::default();

        hasher.input(ContractId::SEED);

        hasher.input(salt);

        hasher.input(root);

        hasher.input(state_root);

        ContractId::from(*hasher.digest())

    }

}

impl From<Vec<u8>> for Contract {

    fn from(c: Vec<u8>) -> Self {

        Self(c)

    }

}

impl From<&[u8]> for Contract {

    fn from(c: &[u8]) -> Self {

        Self(c.into())

    }

}

impl From<&mut [u8]> for Contract {

    fn from(c: &mut [u8]) -> Self {

        Self(c.into())

    }

}

impl From<Contract> for Vec<u8> {

    fn from(c: Contract) -> Vec<u8> {

        c.0

    }

}

impl AsRef<[u8]> for Contract {

    fn as_ref(&self) -> &[u8] {

        self.0.as_ref()

    }

}

impl AsMut<[u8]> for Contract {

    fn as_mut(&mut self) -> &mut [u8] {

        self.0.as_mut()

    }

}

impl TryFrom<&Transaction> for Contract {

    type Error = ValidityError;

    fn try_from(tx: &Transaction) -> Result<Self, Self::Error> {

        match tx {

            Transaction::Create(create) => TryFrom::try_from(create),

            _ => {

                Err(ValidityError::TransactionOutputContainsContractCreated { index: 0 })

            }

        }

    }

}

#[allow(clippy::arithmetic_side_effects, clippy::cast_possible_truncation)]

#[cfg(test)]

mod tests {

    use super::*;

    use fuel_types::{

        bytes::WORD_SIZE,

        Bytes64,

    };

    use itertools::Itertools;

    use quickcheck_macros::quickcheck;

    use rand::{

        rngs::StdRng,

        RngCore,

        SeedableRng,

    };

    use rstest::rstest;

    // safe-guard against breaking changes to the code root calculation for valid

    // sizes of bytecode (multiples of instruction size in bytes (half-word))

    #[rstest]

    fn code_root_snapshot(

        #[values(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100)] instructions: usize,

    ) {

        let mut rng = StdRng::seed_from_u64(100);

        let code_len = instructions * WORD_SIZE / 2;

        let mut code = alloc::vec![0u8; code_len];

        rng.fill_bytes(code.as_mut_slice());

        // compute root

        let root = Contract::root_from_code(code);

        // take root snapshot

        insta::with_settings!(

            {snapshot_suffix => format!("instructions-{instructions}")},

            {

                insta::assert_debug_snapshot!(root);

            }

        );

    }

    // validate code_root is always equivalent to contract.root

    #[quickcheck]

    fn contract_root_matches_code_root(instructions: u8) -> bool {

        let mut rng = StdRng::seed_from_u64(100);

        let code_len = instructions as usize * WORD_SIZE / 2;

        let mut code = alloc::vec![0u8; code_len];

        rng.fill_bytes(code.as_mut_slice());

        let contract = Contract::from(code.clone());

        // compute root

        let code_root = Contract::root_from_code(code);

        let contract_root = contract.root();

        code_root == contract_root

    }

    #[rstest]

    fn state_root_snapshot(

        #[values(Vec::new(), vec![Bytes64::new([1u8; 64])])] state_slot_bytes: Vec<

            Bytes64,

        >,

    ) {

        let slots: Vec<StorageSlot> =

            state_slot_bytes.iter().map(Into::into).collect_vec();

        let state_root = Contract::initial_state_root(&mut slots.iter());

        // take root snapshot

        insta::with_settings!(

            {snapshot_suffix => format!("state-root-{}", slots.len())},

            {

                insta::assert_debug_snapshot!(state_root);

            }

        );

    }

    #[test]

    fn default_state_root_snapshot() {

        let default_root = Contract::default_state_root();

        insta::assert_debug_snapshot!(default_root);

    }

    #[test]

    fn multi_leaf_state_root_snapshot() {

        let mut rng = StdRng::seed_from_u64(0xF00D);

        // 5 full leaves and a partial 6th leaf with 4 bytes of data

        let partial_leaf_size = 4;

        let code_len = 5 * LEAF_SIZE + partial_leaf_size;

        let mut code = alloc::vec![0u8; code_len];

        rng.fill_bytes(code.as_mut_slice());

        // compute root

        let root = Contract::root_from_code(code);

        // take root snapshot

        insta::with_settings!(

            {snapshot_suffix => "multi-leaf-state-root"},

            {

                insta::assert_debug_snapshot!(root);

            }

        );

    }

    #[rstest]

    #[case(0)]

    #[case(1)]

    #[case(8)]

    #[case(500)]

    #[case(1000)]

    #[case(1024)]

    #[case(1025)]

    fn partial_leaf_state_root(#[case] partial_leaf_size: usize) {

        let mut rng = StdRng::seed_from_u64(0xF00D);

        let code_len = partial_leaf_size;

        let mut code = alloc::vec![0u8; code_len];

        rng.fill_bytes(code.as_mut_slice());

        // Compute root

        let root = Contract::root_from_code(code.clone());

        // Compute expected root

        let expected_root = {

            let mut tree = BinaryMerkleTree::new();

            // Push partial leaf with manual padding.

            // We start by generating an n-byte array, where n is the code

            // length rounded to the nearest multiple of 8, and each byte is the

            // PADDING_BYTE by default. The leaf is generated by copying the

            // remaining data bytes into the start of this array.

            let sz = partial_leaf_size.next_multiple_of(8);

            if sz > 0 {

  Branch (302:16): [True: 6, False: 1]

                let mut padded_leaf = vec![PADDING_BYTE; sz];

                padded_leaf[0..code_len].clone_from_slice(&code);

                tree.push(&padded_leaf);

            }
1

            tree.root().into()

        };

        assert_eq!(root, expected_root);

    }

    #[rstest]

    #[case(0)]

    #[case(1)]

    #[case(8)]

    #[case(500)]

    #[case(1000)]

    #[case(1024)]

    #[case(1025)]

    fn multi_leaf_state_root(#[case] partial_leaf_size: usize) {

        let mut rng = StdRng::seed_from_u64(0xF00D);

        // 3 full leaves and a partial 4th leaf

        let code_len = 3 * LEAF_SIZE + partial_leaf_size;

        let mut code = alloc::vec![0u8; code_len];

        rng.fill_bytes(code.as_mut_slice());

        // Compute root

        let root = Contract::root_from_code(code.clone());

        // Compute expected root

        let expected_root = {

            let mut tree = BinaryMerkleTree::new();

            let leaves = code.chunks(LEAF_SIZE).collect::<Vec<_>>();

            tree.push(leaves[0]);

            tree.push(leaves[1]);

            tree.push(leaves[2]);

            // Push partial leaf with manual padding.

            // We start by generating an n-byte array, where n is the code

            // length rounded to the nearest multiple of 8, and each byte is the

            // PADDING_BYTE by default. The leaf is generated by copying the

            // remaining data bytes into the start of this array.

            let sz = partial_leaf_size.next_multiple_of(8);

            if sz > 0 {

  Branch (346:16): [True: 6, False: 1]

                let mut padded_leaf = vec![PADDING_BYTE; sz];

                padded_leaf[0..partial_leaf_size].clone_from_slice(leaves[3]);

                tree.push(&padded_leaf);

            }
1

            tree.root().into()

        };

        assert_eq!(root, expected_root);

    }

    #[test]

    fn empty_contract_id() {

        let contract = Contract::from(vec![]);

        let salt = Salt::zeroed();

        let root = contract.root();

        let state_root = Contract::default_state_root();

        let calculated_id = contract.id(&salt, &root, &state_root);

        assert_eq!(calculated_id, Contract::EMPTY_CONTRACT_ID)

    }

}