use std::collections::{HashMap, HashSet, VecDeque};

use borsh::{BorshDeserialize, BorshSerialize};
use log::debug;
use nssa_core::{
    BlockId, Timestamp,
    account::{Account, AccountId, AccountWithMetadata},
    program::{ChainedCall, Claim, DEFAULT_PROGRAM_ID, validate_execution},
};
use sha2::{Digest as _, digest::FixedOutput as _};

use crate::{
    V03State, ensure,
    error::NssaError,
    public_transaction::{Message, WitnessSet},
    state::MAX_NUMBER_CHAINED_CALLS,
};

#[derive(Debug, Clone, PartialEq, Eq, BorshSerialize, BorshDeserialize)]
pub struct PublicTransaction {
    pub message: Message,
    pub witness_set: WitnessSet,
}

impl PublicTransaction {
    #[must_use]
    pub const fn new(message: Message, witness_set: WitnessSet) -> Self {
        Self {
            message,
            witness_set,
        }
    }

    #[must_use]
    pub const fn message(&self) -> &Message {
        &self.message
    }

    #[must_use]
    pub const fn witness_set(&self) -> &WitnessSet {
        &self.witness_set
    }

    pub(crate) fn signer_account_ids(&self) -> Vec<AccountId> {
        self.witness_set
            .signatures_and_public_keys()
            .iter()
            .map(|(_, public_key)| AccountId::from(public_key))
            .collect()
    }

    #[must_use]
    pub fn affected_public_account_ids(&self) -> Vec<AccountId> {
        let mut acc_set = self
            .signer_account_ids()
            .into_iter()
            .collect::<HashSet<_>>();
        acc_set.extend(&self.message.account_ids);

        acc_set.into_iter().collect()
    }

    #[must_use]
    pub fn hash(&self) -> [u8; 32] {
        let bytes = self.to_bytes();
        let mut hasher = sha2::Sha256::new();
        hasher.update(&bytes);
        hasher.finalize_fixed().into()
    }

    pub(crate) fn validate_and_produce_public_state_diff(
        &self,
        state: &V03State,
        block_id: BlockId,
        timestamp: Timestamp,
    ) -> Result<HashMap<AccountId, Account>, NssaError> {
        let message = self.message();
        let witness_set = self.witness_set();

        // All account_ids must be different
        ensure!(
            message.account_ids.iter().collect::<HashSet<_>>().len() == message.account_ids.len(),
            NssaError::InvalidInput("Duplicate account_ids found in message".into(),)
        );

        // Check exactly one nonce is provided for each signature
        ensure!(
            message.nonces.len() == witness_set.signatures_and_public_keys.len(),
            NssaError::InvalidInput(
                "Mismatch between number of nonces and signatures/public keys".into(),
            )
        );

        // Check the signatures are valid
        ensure!(
            witness_set.is_valid_for(message),
            NssaError::InvalidInput("Invalid signature for given message and public key".into())
        );

        let signer_account_ids = self.signer_account_ids();
        // Check nonces corresponds to the current nonces on the public state.
        for (account_id, nonce) in signer_account_ids.iter().zip(&message.nonces) {
            let current_nonce = state.get_account_by_id(*account_id).nonce;
            ensure!(
                current_nonce == *nonce,
                NssaError::InvalidInput("Nonce mismatch".into())
            );
        }

        // Build pre_states for execution
        let input_pre_states: Vec<_> = message
            .account_ids
            .iter()
            .map(|account_id| {
                AccountWithMetadata::new(
                    state.get_account_by_id(*account_id),
                    signer_account_ids.contains(account_id),
                    *account_id,
                )
            })
            .collect();

        let mut state_diff: HashMap<AccountId, Account> = HashMap::new();

        let initial_call = ChainedCall {
            program_id: message.program_id,
            instruction_data: message.instruction_data.clone(),
            pre_states: input_pre_states,
            pda_seeds: vec![],
        };

        let mut chained_calls = VecDeque::from_iter([(initial_call, None)]);
        let mut chain_calls_counter = 0;

        while let Some((chained_call, caller_program_id)) = chained_calls.pop_front() {
            ensure!(
                chain_calls_counter <= MAX_NUMBER_CHAINED_CALLS,
                NssaError::MaxChainedCallsDepthExceeded
            );

            // Check that the `program_id` corresponds to a deployed program
            let Some(program) = state.programs().get(&chained_call.program_id) else {
                return Err(NssaError::InvalidInput("Unknown program".into()));
            };

            debug!(
                "Program {:?} pre_states: {:?}, instruction_data: {:?}",
                chained_call.program_id, chained_call.pre_states, chained_call.instruction_data
            );
            let mut program_output =
                program.execute(&chained_call.pre_states, &chained_call.instruction_data)?;
            debug!(
                "Program {:?} output: {:?}",
                chained_call.program_id, program_output
            );

            let authorized_pdas = nssa_core::program::compute_authorized_pdas(
                caller_program_id,
                &chained_call.pda_seeds,
            );

            let is_authorized = |account_id: &AccountId| {
                signer_account_ids.contains(account_id) || authorized_pdas.contains(account_id)
            };

            for pre in &program_output.pre_states {
                let account_id = pre.account_id;
                // Check that the program output pre_states coincide with the values in the public
                // state or with any modifications to those values during the chain of calls.
                let expected_pre = state_diff
                    .get(&account_id)
                    .cloned()
                    .unwrap_or_else(|| state.get_account_by_id(account_id));
                ensure!(
                    pre.account == expected_pre,
                    NssaError::InvalidProgramBehavior
                );

                // Check that authorization flags are consistent with the provided ones or
                // authorized by program through the PDA mechanism
                ensure!(
                    pre.is_authorized == is_authorized(&account_id),
                    NssaError::InvalidProgramBehavior
                );
            }

            // Verify that the program output's self_program_id matches the expected program ID.
            ensure!(
                program_output.self_program_id == chained_call.program_id,
                NssaError::InvalidProgramBehavior
            );

            // Verify execution corresponds to a well-behaved program.
            // See the # Programs section for the definition of the `validate_execution` method.
            ensure!(
                validate_execution(
                    &program_output.pre_states,
                    &program_output.post_states,
                    chained_call.program_id,
                ),
                NssaError::InvalidProgramBehavior
            );

            // Verify validity window
            ensure!(
                program_output.block_validity_window.is_valid_for(block_id)
                    && program_output
                        .timestamp_validity_window
                        .is_valid_for(timestamp),
                NssaError::OutOfValidityWindow
            );

            for (i, post) in program_output.post_states.iter_mut().enumerate() {
                let Some(claim) = post.required_claim() else {
                    continue;
                };
                // The invoked program can only claim accounts with default program id.
                ensure!(
                    post.account().program_owner == DEFAULT_PROGRAM_ID,
                    NssaError::InvalidProgramBehavior
                );

                let account_id = program_output.pre_states[i].account_id;

                match claim {
                    Claim::Authorized => {
                        // The program can only claim accounts that were authorized by the signer.
                        ensure!(
                            is_authorized(&account_id),
                            NssaError::InvalidProgramBehavior
                        );
                    }
                    Claim::Pda(seed) => {
                        // The program can only claim accounts that correspond to the PDAs it is
                        // authorized to claim.
                        let pda = AccountId::from((&chained_call.program_id, &seed));
                        ensure!(account_id == pda, NssaError::InvalidProgramBehavior);
                    }
                }

                post.account_mut().program_owner = chained_call.program_id;
            }

            // Update the state diff
            for (pre, post) in program_output
                .pre_states
                .iter()
                .zip(program_output.post_states.iter())
            {
                state_diff.insert(pre.account_id, post.account().clone());
            }

            for new_call in program_output.chained_calls.into_iter().rev() {
                chained_calls.push_front((new_call, Some(chained_call.program_id)));
            }

            chain_calls_counter = chain_calls_counter
                .checked_add(1)
                .expect("we check the max depth at the beginning of the loop");
        }

        // Check that all modified uninitialized accounts where claimed
        for post in state_diff.iter().filter_map(|(account_id, post)| {
            let pre = state.get_account_by_id(*account_id);
            if pre.program_owner != DEFAULT_PROGRAM_ID {
                return None;
            }
            if pre == *post {
                return None;
            }
            Some(post)
        }) {
            ensure!(
                post.program_owner != DEFAULT_PROGRAM_ID,
                NssaError::InvalidProgramBehavior
            );
        }

        Ok(state_diff)
    }
}

#[cfg(test)]
pub mod tests {
    use sha2::{Digest as _, digest::FixedOutput as _};

    use crate::{
        AccountId, PrivateKey, PublicKey, PublicTransaction, Signature, V03State,
        error::NssaError,
        program::Program,
        public_transaction::{Message, WitnessSet},
    };

    fn keys_for_tests() -> (PrivateKey, PrivateKey, AccountId, AccountId) {
        let key1 = PrivateKey::try_new([1; 32]).unwrap();
        let key2 = PrivateKey::try_new([2; 32]).unwrap();
        let addr1 = AccountId::from(&PublicKey::new_from_private_key(&key1));
        let addr2 = AccountId::from(&PublicKey::new_from_private_key(&key2));
        (key1, key2, addr1, addr2)
    }

    fn state_for_tests() -> V03State {
        let (_, _, addr1, addr2) = keys_for_tests();
        let initial_data = [(addr1, 10000), (addr2, 20000)];
        V03State::new_with_genesis_accounts(&initial_data, &[])
    }

    fn transaction_for_tests() -> PublicTransaction {
        let (key1, key2, addr1, addr2) = keys_for_tests();
        let nonces = vec![0_u128.into(), 0_u128.into()];
        let instruction = 1337;
        let message = Message::try_new(
            Program::authenticated_transfer_program().id(),
            vec![addr1, addr2],
            nonces,
            instruction,
        )
        .unwrap();

        let witness_set = WitnessSet::for_message(&message, &[&key1, &key2]);
        PublicTransaction::new(message, witness_set)
    }

    #[test]
    fn new_constructor() {
        let tx = transaction_for_tests();
        let message = tx.message().clone();
        let witness_set = tx.witness_set().clone();
        let tx_from_constructor = PublicTransaction::new(message.clone(), witness_set.clone());
        assert_eq!(tx_from_constructor.message, message);
        assert_eq!(tx_from_constructor.witness_set, witness_set);
    }

    #[test]
    fn message_getter() {
        let tx = transaction_for_tests();
        assert_eq!(&tx.message, tx.message());
    }

    #[test]
    fn witness_set_getter() {
        let tx = transaction_for_tests();
        assert_eq!(&tx.witness_set, tx.witness_set());
    }

    #[test]
    fn signer_account_ids() {
        let tx = transaction_for_tests();
        let expected_signer_account_ids = vec![
            AccountId::new([
                148, 179, 206, 253, 199, 51, 82, 86, 232, 2, 152, 122, 80, 243, 54, 207, 237, 112,
                83, 153, 44, 59, 204, 49, 128, 84, 160, 227, 216, 149, 97, 102,
            ]),
            AccountId::new([
                30, 145, 107, 3, 207, 73, 192, 230, 160, 63, 238, 207, 18, 69, 54, 216, 103, 244,
                92, 94, 124, 248, 42, 16, 141, 19, 119, 18, 14, 226, 140, 204,
            ]),
        ];
        let signer_account_ids = tx.signer_account_ids();
        assert_eq!(signer_account_ids, expected_signer_account_ids);
    }

    #[test]
    fn public_transaction_encoding_bytes_roundtrip() {
        let tx = transaction_for_tests();
        let bytes = tx.to_bytes();
        let tx_from_bytes = PublicTransaction::from_bytes(&bytes).unwrap();
        assert_eq!(tx, tx_from_bytes);
    }

    #[test]
    fn hash_is_sha256_of_transaction_bytes() {
        let tx = transaction_for_tests();
        let hash = tx.hash();
        let expected_hash: [u8; 32] = {
            let bytes = tx.to_bytes();
            let mut hasher = sha2::Sha256::new();
            hasher.update(&bytes);
            hasher.finalize_fixed().into()
        };
        assert_eq!(hash, expected_hash);
    }

    #[test]
    fn account_id_list_cant_have_duplicates() {
        let (key1, _, addr1, _) = keys_for_tests();
        let state = state_for_tests();
        let nonces = vec![0_u128.into(), 0_u128.into()];
        let instruction = 1337;
        let message = Message::try_new(
            Program::authenticated_transfer_program().id(),
            vec![addr1, addr1],
            nonces,
            instruction,
        )
        .unwrap();

        let witness_set = WitnessSet::for_message(&message, &[&key1, &key1]);
        let tx = PublicTransaction::new(message, witness_set);
        let result = tx.validate_and_produce_public_state_diff(&state, 1, 0);
        assert!(matches!(result, Err(NssaError::InvalidInput(_))));
    }

    #[test]
    fn number_of_nonces_must_match_number_of_signatures() {
        let (key1, key2, addr1, addr2) = keys_for_tests();
        let state = state_for_tests();
        let nonces = vec![0_u128.into()];
        let instruction = 1337;
        let message = Message::try_new(
            Program::authenticated_transfer_program().id(),
            vec![addr1, addr2],
            nonces,
            instruction,
        )
        .unwrap();

        let witness_set = WitnessSet::for_message(&message, &[&key1, &key2]);
        let tx = PublicTransaction::new(message, witness_set);
        let result = tx.validate_and_produce_public_state_diff(&state, 1, 0);
        assert!(matches!(result, Err(NssaError::InvalidInput(_))));
    }

    #[test]
    fn all_signatures_must_be_valid() {
        let (key1, key2, addr1, addr2) = keys_for_tests();
        let state = state_for_tests();
        let nonces = vec![0_u128.into(), 0_u128.into()];
        let instruction = 1337;
        let message = Message::try_new(
            Program::authenticated_transfer_program().id(),
            vec![addr1, addr2],
            nonces,
            instruction,
        )
        .unwrap();

        let mut witness_set = WitnessSet::for_message(&message, &[&key1, &key2]);
        witness_set.signatures_and_public_keys[0].0 = Signature::new_for_tests([1; 64]);
        let tx = PublicTransaction::new(message, witness_set);
        let result = tx.validate_and_produce_public_state_diff(&state, 1, 0);
        assert!(matches!(result, Err(NssaError::InvalidInput(_))));
    }

    #[test]
    fn nonces_must_match_the_state_current_nonces() {
        let (key1, key2, addr1, addr2) = keys_for_tests();
        let state = state_for_tests();
        let nonces = vec![0_u128.into(), 1_u128.into()];
        let instruction = 1337;
        let message = Message::try_new(
            Program::authenticated_transfer_program().id(),
            vec![addr1, addr2],
            nonces,
            instruction,
        )
        .unwrap();

        let witness_set = WitnessSet::for_message(&message, &[&key1, &key2]);
        let tx = PublicTransaction::new(message, witness_set);
        let result = tx.validate_and_produce_public_state_diff(&state, 1, 0);
        assert!(matches!(result, Err(NssaError::InvalidInput(_))));
    }

    #[test]
    fn program_id_must_belong_to_bulitin_program_ids() {
        let (key1, key2, addr1, addr2) = keys_for_tests();
        let state = state_for_tests();
        let nonces = vec![0_u128.into(), 0_u128.into()];
        let instruction = 1337;
        let unknown_program_id = [0xdead_beef; 8];
        let message =
            Message::try_new(unknown_program_id, vec![addr1, addr2], nonces, instruction).unwrap();

        let witness_set = WitnessSet::for_message(&message, &[&key1, &key2]);
        let tx = PublicTransaction::new(message, witness_set);
        let result = tx.validate_and_produce_public_state_diff(&state, 1, 0);
        assert!(matches!(result, Err(NssaError::InvalidInput(_))));
    }
}