use cosmwasm_std::testing::{digit_sum, riffle_shuffle};
use cosmwasm_std::{
    Addr, BlockInfo, Coin, ContractInfo, Env, MessageInfo, Timestamp, TransactionInfo,
};

use super::querier::MockQuerier;
use super::storage::MockStorage;
use crate::{Backend, BackendApi, BackendError, BackendResult, GasInfo};

pub const MOCK_CONTRACT_ADDR: &str = "cosmos2contract";
const GAS_COST_HUMANIZE: u64 = 44;
const GAS_COST_CANONICALIZE: u64 = 55;

/// All external requirements that can be injected for unit tests.
/// It sets the given balance for the contract itself, nothing else
pub fn mock_backend(contract_balance: &[Coin]) -> Backend<MockApi, MockStorage, MockQuerier> {
    Backend {
        api: MockApi::default(),
        storage: MockStorage::default(),
        querier: MockQuerier::new(&[(MOCK_CONTRACT_ADDR, contract_balance)]),
    }
}

/// Initializes the querier along with the mock_dependencies.
/// Sets all balances provided (yoy must explicitly set contract balance if desired)
pub fn mock_backend_with_balances(
    balances: &[(&str, &[Coin])],
) -> Backend<MockApi, MockStorage, MockQuerier> {
    Backend {
        api: MockApi::default(),
        storage: MockStorage::default(),
        querier: MockQuerier::new(balances),
    }
}

/// Length of canonical addresses created with this API. Contracts should not make any assumtions
/// what this value is.
/// The value here must be restorable with `SHUFFLES_ENCODE` + `SHUFFLES_DECODE` in-shuffles.
const CANONICAL_LENGTH: usize = 54;

const SHUFFLES_ENCODE: usize = 18;
const SHUFFLES_DECODE: usize = 2;

/// Zero-pads all human addresses to make them fit the canonical_length and
/// trims off zeros for the reverse operation.
/// This is not really smart, but allows us to see a difference (and consistent length for canonical adddresses).
#[derive(Copy, Clone)]
pub struct MockApi {
    /// Length of canonical addresses created with this API. Contracts should not make any assumtions
    /// what this value is.
    canonical_length: usize,
    /// When set, all calls to the API fail with BackendError::Unknown containing this message
    backend_error: Option<&'static str>,
}

impl MockApi {
    /// Read-only getter for `canonical_length`, which must not be changed by the caller.
    pub fn canonical_length(&self) -> usize {
        self.canonical_length
    }

    pub fn new_failing(backend_error: &'static str) -> Self {
        MockApi {
            backend_error: Some(backend_error),
            ..MockApi::default()
        }
    }
}

impl Default for MockApi {
    fn default() -> Self {
        MockApi {
            canonical_length: CANONICAL_LENGTH,
            backend_error: None,
        }
    }
}

impl BackendApi for MockApi {
    fn canonical_address(&self, human: &str) -> BackendResult<Vec<u8>> {
        let gas_info = GasInfo::with_cost(GAS_COST_CANONICALIZE);

        if let Some(backend_error) = self.backend_error {
            return (Err(BackendError::unknown(backend_error)), gas_info);
        }

        // Dummy input validation. This is more sophisticated for formats like bech32, where format and checksum are validated.
        if human.len() < 3 {
            return (
                Err(BackendError::user_err(
                    "Invalid input: human address too short",
                )),
                gas_info,
            );
        }
        if human.len() > self.canonical_length {
            return (
                Err(BackendError::user_err(
                    "Invalid input: human address too long",
                )),
                gas_info,
            );
        }

        let mut out = Vec::from(human);
        // pad to canonical length with NULL bytes
        out.resize(self.canonical_length, 0x00);
        // content-dependent rotate followed by shuffle to destroy
        // the most obvious structure (https://github.com/CosmWasm/cosmwasm/issues/552)
        let rotate_by = digit_sum(&out) % self.canonical_length;
        out.rotate_left(rotate_by);
        for _ in 0..SHUFFLES_ENCODE {
            out = riffle_shuffle(&out);
        }
        (Ok(out), gas_info)
    }

    fn human_address(&self, canonical: &[u8]) -> BackendResult<String> {
        let gas_info = GasInfo::with_cost(GAS_COST_HUMANIZE);

        if let Some(backend_error) = self.backend_error {
            return (Err(BackendError::unknown(backend_error)), gas_info);
        }

        if canonical.len() != self.canonical_length {
            return (
                Err(BackendError::user_err(
                    "Invalid input: canonical address length not correct",
                )),
                gas_info,
            );
        }

        let mut tmp: Vec<u8> = canonical.into();
        // Shuffle two more times which restored the original value (24 elements are back to original after 20 rounds)
        for _ in 0..SHUFFLES_DECODE {
            tmp = riffle_shuffle(&tmp);
        }
        // Rotate back
        let rotate_by = digit_sum(&tmp) % self.canonical_length;
        tmp.rotate_right(rotate_by);
        // Remove NULL bytes (i.e. the padding)
        let trimmed = tmp.into_iter().filter(|&x| x != 0x00).collect();

        let result = match String::from_utf8(trimmed) {
            Ok(human) => Ok(human),
            Err(err) => Err(err.into()),
        };
        (result, gas_info)
    }
}

/// Returns a default enviroment with height, time, chain_id, and contract address
/// You can submit as is to most contracts, or modify height/time if you want to
/// test for expiration.
///
/// This is intended for use in test code only.
pub fn mock_env() -> Env {
    Env {
        block: BlockInfo {
            height: 12_345,
            time: Timestamp::from_nanos(1_571_797_419_879_305_533),
            chain_id: "cosmos-testnet-14002".to_string(),
        },
        transaction: Some(TransactionInfo { index: 3 }),
        contract: ContractInfo {
            address: Addr::unchecked(MOCK_CONTRACT_ADDR),
        },
    }
}

/// Just set sender and funds for the message.
/// This is intended for use in test code only.
pub fn mock_info(sender: &str, funds: &[Coin]) -> MessageInfo {
    MessageInfo {
        sender: Addr::unchecked(sender),
        funds: funds.to_vec(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::BackendError;
    use cosmwasm_std::coins;

    #[test]
    fn mock_info_works() {
        let info = mock_info("my name", &coins(100, "atom"));
        assert_eq!(
            info,
            MessageInfo {
                sender: Addr::unchecked("my name"),
                funds: vec![Coin {
                    amount: 100u128.into(),
                    denom: "atom".into(),
                }]
            }
        );
    }

    #[test]
    fn canonicalize_and_humanize_restores_original() {
        let api = MockApi::default();

        let original = "shorty";
        let canonical = api.canonical_address(original).0.unwrap();
        let (recovered, _gas_cost) = api.human_address(&canonical);
        assert_eq!(recovered.unwrap(), original);
    }

    #[test]
    fn human_address_input_length() {
        let api = MockApi::default();
        let input = vec![61; 11];
        let (result, _gas_info) = api.human_address(&input);
        match result.unwrap_err() {
            BackendError::UserErr { .. } => {}
            err => panic!("Unexpected error: {:?}", err),
        }
    }

    #[test]
    fn canonical_address_min_input_length() {
        let api = MockApi::default();
        let human = "1";
        match api.canonical_address(human).0.unwrap_err() {
            BackendError::UserErr { .. } => {}
            err => panic!("Unexpected error: {:?}", err),
        }
    }

    #[test]
    fn canonical_address_max_input_length() {
        let api = MockApi::default();
        let human = "longer-than-the-address-length-supported-by-this-api-longer-than-54";
        match api.canonical_address(human).0.unwrap_err() {
            BackendError::UserErr { .. } => {}
            err => panic!("Unexpected error: {:?}", err),
        }
    }
}