//! Consensus parameters for each Zcash network.

use std::{fmt, str::FromStr};

use thiserror::Error;

use crate::{
    block::{Height, HeightDiff},
    parameters::NetworkUpgrade::Canopy,
};

#[cfg(any(test, feature = "proptest-impl"))]
use proptest_derive::Arbitrary;

#[cfg(test)]
mod tests;

/// The ZIP-212 grace period length after the Canopy activation height.
///
/// # Consensus
///
/// ZIP-212 requires Zcash nodes to validate that Sapling spends and Orchard actions follows a
/// specific plaintext format after Canopy's activation.
///
/// > [Heartwood onward] All Sapling and Orchard outputs in coinbase transactions MUST decrypt to a
/// > note plaintext , i.e. the procedure in § 4.19.3 ‘Decryption using a Full Viewing Key (Sapling
/// > and Orchard)’ on p. 67 does not return ⊥, using a sequence of 32 zero bytes as the outgoing
/// > viewing key . (This implies that before Canopy activation, Sapling outputs of a coinbase
/// > transaction MUST have note plaintext lead byte equal to 0x01.)
///
/// > [Canopy onward] Any Sapling or Orchard output of a coinbase transaction decrypted to a note
/// > plaintext according to the preceding rule MUST have note plaintext lead byte equal to 0x02.
/// > (This applies even during the “grace period” specified in [ZIP-212].)
///
/// <https://zips.z.cash/protocol/protocol.pdf#txnencodingandconsensus>
///
/// Wallets have a grace period of 32,256 blocks after Canopy's activation to validate those blocks,
/// but nodes do not.
///
/// > There is a "grace period" of 32256 blocks starting from the block at which this ZIP activates,
/// > during which note plaintexts with lead byte 0x01 MUST still be accepted [by wallets].
/// >
/// > Let ActivationHeight be the activation height of this ZIP, and let GracePeriodEndHeight be
/// > ActivationHeight + 32256.
///
/// <https://zips.z.cash/zip-0212#changes-to-the-process-of-receiving-sapling-or-orchard-notes>
///
/// Zebra uses `librustzcash` to validate that rule, but it won't validate it during the grace
/// period. Therefore Zebra must validate those blocks during the grace period using checkpoints.
/// Therefore the mandatory checkpoint height ([`Network::mandatory_checkpoint_height`]) must be
/// after the grace period.
const ZIP_212_GRACE_PERIOD_DURATION: HeightDiff = 32_256;

/// An enum describing the possible network choices.
#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, Hash, Serialize, Deserialize)]
#[cfg_attr(any(test, feature = "proptest-impl"), derive(Arbitrary))]
pub enum Network {
    /// The production mainnet.
    #[default]
    Mainnet,

    /// The oldest public test network.
    Testnet,
}

impl From<Network> for &'static str {
    fn from(network: Network) -> &'static str {
        match network {
            Network::Mainnet => "Mainnet",
            Network::Testnet => "Testnet",
        }
    }
}

impl From<&Network> for &'static str {
    fn from(network: &Network) -> &'static str {
        (*network).into()
    }
}

impl fmt::Display for Network {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.into())
    }
}

impl Network {
    /// Get the default port associated to this network.
    pub fn default_port(&self) -> u16 {
        match self {
            Network::Mainnet => 8233,
            Network::Testnet => 18233,
        }
    }

    /// Get the mandatory minimum checkpoint height for this network.
    ///
    /// Mandatory checkpoints are a Zebra-specific feature.
    /// If a Zcash consensus rule only applies before the mandatory checkpoint,
    /// Zebra can skip validation of that rule.
    pub fn mandatory_checkpoint_height(&self) -> Height {
        // Currently this is after the ZIP-212 grace period.
        //
        // See the `ZIP_212_GRACE_PERIOD_DOCUMENTATION` for more information.

        let canopy_activation = Canopy
            .activation_height(*self)
            .expect("Canopy activation height must be present for both networks");

        (canopy_activation + ZIP_212_GRACE_PERIOD_DURATION)
            .expect("ZIP-212 grace period ends at a valid block height")
    }

    /// Return the network name as defined in
    /// [BIP70](https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki#paymentdetailspaymentrequest)
    pub fn bip70_network_name(&self) -> String {
        match self {
            Network::Mainnet => "main".to_string(),
            Network::Testnet => "test".to_string(),
        }
    }

    /// Return the lowercase network name.
    pub fn lowercase_name(&self) -> String {
        self.to_string().to_ascii_lowercase()
    }

    /// Returns `true` if this network is a testing network.
    pub fn is_a_test_network(&self) -> bool {
        *self != Network::Mainnet
    }
}

impl FromStr for Network {
    type Err = InvalidNetworkError;

    fn from_str(string: &str) -> Result<Self, Self::Err> {
        match string.to_lowercase().as_str() {
            "mainnet" => Ok(Network::Mainnet),
            "testnet" => Ok(Network::Testnet),
            _ => Err(InvalidNetworkError(string.to_owned())),
        }
    }
}

#[derive(Clone, Debug, Error)]
#[error("Invalid network: {0}")]
pub struct InvalidNetworkError(String);