// Rust Bitcoin Library
// Written in 2014 by
//     Andrew Poelstra <apoelstra@wpsoftware.net>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! Miscellaneous functions
//!
//! Various utility functions

use hashes::{sha256d, Hash, HashEngine};
use blockdata::opcodes;
use consensus::{encode, Encodable};

static MSG_SIGN_PREFIX: &[u8] = b"\x18Bitcoin Signed Message:\n";

/// Search for `needle` in the vector `haystack` and remove every
/// instance of it, returning the number of instances removed.
/// Loops through the vector opcode by opcode, skipping pushed data.
pub fn script_find_and_remove(haystack: &mut Vec<u8>, needle: &[u8]) -> usize {
    if needle.len() > haystack.len() { return 0; }
    if needle.is_empty() { return 0; }

    let mut top = haystack.len() - needle.len();
    let mut n_deleted = 0;

    let mut i = 0;
    while i <= top {
        if &haystack[i..(i + needle.len())] == needle {
            for j in i..top {
                haystack.swap(j + needle.len(), j);
            }
            n_deleted += 1;
            // This is ugly but prevents infinite loop in case of overflow
            let overflow = top < needle.len();
            top = top.wrapping_sub(needle.len());
            if overflow { break; }
        } else {
            i += match opcodes::All::from((*haystack)[i]).classify() {
                opcodes::Class::PushBytes(n) => n as usize + 1,
                opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA1) => 2,
                opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA2) => 3,
                opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA4) => 5,
                _ => 1
            };
        }
    }
    haystack.truncate(top.wrapping_add(needle.len()));
    n_deleted
}

/// Hash message for signature using Bitcoin's message signing format
pub fn signed_msg_hash(msg: &str) -> sha256d::Hash {

    let mut engine = sha256d::Hash::engine();
    engine.input(MSG_SIGN_PREFIX);
    let msg_len = encode::VarInt(msg.len() as u64);
    msg_len.consensus_encode(&mut engine).unwrap();
    engine.input(msg.as_bytes());

    sha256d::Hash::from_engine(engine)
}

#[cfg(test)]
mod tests {
    use hashes::hex::ToHex;
    use super::script_find_and_remove;
    use super::signed_msg_hash;

    #[test]
    fn test_script_find_and_remove() {
        let mut v = vec![101u8, 102, 103, 104, 102, 103, 104, 102, 103, 104, 105, 106, 107, 108, 109];

        assert_eq!(script_find_and_remove(&mut v, &[]), 0);
        assert_eq!(script_find_and_remove(&mut v, &[105, 105, 105]), 0);
        assert_eq!(v, vec![101, 102, 103, 104, 102, 103, 104, 102, 103, 104, 105, 106, 107, 108, 109]);

        assert_eq!(script_find_and_remove(&mut v, &[105, 106, 107]), 1);
        assert_eq!(v, vec![101, 102, 103, 104, 102, 103, 104, 102, 103, 104, 108, 109]);

        assert_eq!(script_find_and_remove(&mut v, &[104, 108, 109]), 1);
        assert_eq!(v, vec![101, 102, 103, 104, 102, 103, 104, 102, 103]);

        assert_eq!(script_find_and_remove(&mut v, &[101]), 1);
        assert_eq!(v, vec![102, 103, 104, 102, 103, 104, 102, 103]);

        assert_eq!(script_find_and_remove(&mut v, &[102]), 3);
        assert_eq!(v, vec![103, 104, 103, 104, 103]);

        assert_eq!(script_find_and_remove(&mut v, &[103, 104]), 2);
        assert_eq!(v, vec![103]);

        assert_eq!(script_find_and_remove(&mut v, &[105, 105, 5]), 0);
        assert_eq!(script_find_and_remove(&mut v, &[105]), 0);
        assert_eq!(script_find_and_remove(&mut v, &[103]), 1);
        assert_eq!(v, Vec::<u8>::new());

        assert_eq!(script_find_and_remove(&mut v, &[105, 105, 5]), 0);
        assert_eq!(script_find_and_remove(&mut v, &[105]), 0);
    }

    #[test]
    fn test_script_codesep_remove() {
        let mut s = vec![33u8, 3, 132, 121, 160, 250, 153, 140, 211, 82, 89, 162, 239, 10, 122, 92, 104, 102, 44, 20, 116, 248, 140, 203, 109, 8, 167, 103, 123, 190, 199, 242, 32, 65, 173, 171, 33, 3, 132, 121, 160, 250, 153, 140, 211, 82, 89, 162, 239, 10, 122, 92, 104, 102, 44, 20, 116, 248, 140, 203, 109, 8, 167, 103, 123, 190, 199, 242, 32, 65, 173, 171, 81];
        assert_eq!(script_find_and_remove(&mut s, &[171]), 2);
        assert_eq!(s, vec![33, 3, 132, 121, 160, 250, 153, 140, 211, 82, 89, 162, 239, 10, 122, 92, 104, 102, 44, 20, 116, 248, 140, 203, 109, 8, 167, 103, 123, 190, 199, 242, 32, 65, 173, 33, 3, 132, 121, 160, 250, 153, 140, 211, 82, 89, 162, 239, 10, 122, 92, 104, 102, 44, 20, 116, 248, 140, 203, 109, 8, 167, 103, 123, 190, 199, 242, 32, 65, 173, 81]);
    }

    #[test]
    fn test_signed_msg_hash() {
        let hash = signed_msg_hash("test");
        assert_eq!(hash.to_hex(), "a6f87fe6d58a032c320ff8d1541656f0282c2c7bfcc69d61af4c8e8ed528e49c");
    }
}