//! Newtype wrappers for primitive data types with semantic meaning.

use std::{
    fmt,
    io::{self, Read},
};

use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
use chrono::{DateTime, TimeZone, Utc};

#[cfg(test)]
use proptest_derive::Arbitrary;

use crate::serialization::{
    ReadZcashExt, SerializationError, WriteZcashExt, ZcashDeserialize, ZcashSerialize,
};

pub mod amount;

/// A u32 which represents a block height value.
///
/// # Invariants
///
/// Users should not construct block heights greater than or equal to `500_000_000`.
#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct BlockHeight(pub u32);

#[cfg(test)]
impl Arbitrary for BlockHeight {
    type Parameters = ();

    fn arbitrary_with(_args: ()) -> Self::Strategy {
        (0u32..500_000_000_u32).prop_map(BlockHeight).boxed()
    }

    type Strategy = BoxedStrategy<Self>;
}

/// A Bitcoin-style `locktime`, representing either a block height or an epoch
/// time.
///
/// # Invariants
///
/// Users should not construct a `LockTime` with `BlockHeight` greater than or
/// equal to `500_000_000` or a timestamp before 4 November 1985 (Unix timestamp
/// less than `500_000_000`).
#[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum LockTime {
    /// Unlock at a particular block height.
    Height(BlockHeight),
    /// Unlock at a particular time.
    Time(DateTime<Utc>),
}

impl ZcashSerialize for LockTime {
    fn zcash_serialize<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
        // This implementation does not check the invariants on `LockTime` so that the
        // serialization is fallible only if the underlying writer is. This ensures that
        // we can always compute a hash of a transaction object.
        use LockTime::*;
        match self {
            Height(BlockHeight(n)) => writer.write_u32::<LittleEndian>(*n)?,
            Time(t) => writer.write_u32::<LittleEndian>(t.timestamp() as u32)?,
        }
        Ok(())
    }
}

impl ZcashDeserialize for LockTime {
    fn zcash_deserialize<R: io::Read>(mut reader: R) -> Result<Self, SerializationError> {
        let n = reader.read_u32::<LittleEndian>()?;
        if n < 500_000_000 {
            Ok(LockTime::Height(BlockHeight(n)))
        } else {
            Ok(LockTime::Time(Utc.timestamp(n as i64, 0)))
        }
    }
}

#[cfg(test)]
impl Arbitrary for LockTime {
    type Parameters = ();

    fn arbitrary_with(_args: ()) -> Self::Strategy {
        prop_oneof![
            (0u32..500_000_000_u32).prop_map(|n| LockTime::Height(BlockHeight(n))),
            // XXX Setting max to i64::MAX doesn't work, this is 2**32.
            (500_000_000i64..4_294_967_296).prop_map(|n| { LockTime::Time(Utc.timestamp(n, 0)) })
        ]
        .boxed()
    }

    type Strategy = BoxedStrategy<Self>;
}

/// An encoding of a Bitcoin script.
#[derive(Clone, Eq, PartialEq, Serialize, Deserialize)]
#[cfg_attr(test, derive(Arbitrary))]
pub struct Script(pub Vec<u8>);

impl fmt::Debug for Script {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_tuple("Script")
            .field(&hex::encode(&self.0))
            .finish()
    }
}

impl ZcashSerialize for Script {
    fn zcash_serialize<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
        writer.write_compactsize(self.0.len() as u64)?;
        writer.write_all(&self.0[..])?;
        Ok(())
    }
}

impl ZcashDeserialize for Script {
    fn zcash_deserialize<R: io::Read>(mut reader: R) -> Result<Self, SerializationError> {
        // XXX what is the max length of a script?
        let len = reader.read_compactsize()?;
        let mut bytes = Vec::new();
        reader.take(len).read_to_end(&mut bytes)?;
        Ok(Script(bytes))
    }
}

/// A 4-byte checksum using truncated double-SHA256 (two rounds of SHA256).
#[derive(Copy, Clone, Eq, PartialEq)]
pub struct Sha256dChecksum(pub [u8; 4]);

impl<'a> From<&'a [u8]> for Sha256dChecksum {
    fn from(bytes: &'a [u8]) -> Self {
        use sha2::{Digest, Sha256};
        let hash1 = Sha256::digest(bytes);
        let hash2 = Sha256::digest(&hash1);
        let mut checksum = [0u8; 4];
        checksum[0..4].copy_from_slice(&hash2[0..4]);
        Self(checksum)
    }
}

impl fmt::Debug for Sha256dChecksum {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_tuple("Sha256dChecksum")
            .field(&hex::encode(&self.0))
            .finish()
    }
}

#[cfg(test)]
use proptest::prelude::*;

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn sha256d_checksum() {
        // https://en.bitcoin.it/wiki/Protocol_documentation#Hashes
        let input = b"hello";
        let checksum = Sha256dChecksum::from(&input[..]);
        let expected = Sha256dChecksum([0x95, 0x95, 0xc9, 0xdf]);
        assert_eq!(checksum, expected);
    }

    #[test]
    fn sha256d_checksum_debug() {
        let input = b"hello";
        let checksum = Sha256dChecksum::from(&input[..]);

        assert_eq!(format!("{:?}", checksum), "Sha256dChecksum(\"9595c9df\")");
    }
}

#[cfg(test)]
mod proptests {

    use std::io::Cursor;

    use proptest::prelude::*;

    use super::{LockTime, Script};
    use crate::serialization::{ZcashDeserialize, ZcashSerialize};

    proptest! {

        #[test]
        fn locktime_roundtrip(locktime in any::<LockTime>()) {
            let mut bytes = Cursor::new(Vec::new());
            locktime.zcash_serialize(&mut bytes)?;

            bytes.set_position(0);
            let other_locktime = LockTime::zcash_deserialize(&mut bytes)?;

            prop_assert_eq![locktime, other_locktime];
        }

        #[test]
        fn script_roundtrip(script in any::<Script>()) {
            let mut bytes = Cursor::new(Vec::new());
            script.zcash_serialize(&mut bytes)?;

            bytes.set_position(0);
            let other_script = Script::zcash_deserialize(&mut bytes)?;

            prop_assert_eq![script, other_script];
        }

    }
}