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use crate::bytes_ext::{BytesExt, BytesMutExt, TryGetError};

use crate::inventory::ItemStack;

use crate::world::BlockPosition;

use bytes::{Buf, BytesMut};

use feather_items::{Item, ItemExt};

use serde::de::DeserializeOwned;

use serde::Serialize;

use std::io::Read;

use uuid::Uuid;

/// Identifies a type to which Minecraft-specific

/// types (`VarInt`, `VarLong`, etc.) can be written.

pub trait McTypeWrite {

/// Writes a `VarInt` to the object. See wiki.vg for

/// details on `VarInt`s and related types.

///

/// Returns the number of bytes used to encode this integer.

fn push_var_int(&mut self, x: i32) -> usize;

/// Writes a string to the object. This method

/// will first write the length of the string in bytes

/// encodes as a `VarInt` and will then write

/// the UTF-8 bytes of the string.

fn push_string(&mut self, x: &str);

fn push_position(&mut self, x: &BlockPosition);

fn push_bool(&mut self, x: bool);

fn push_uuid(&mut self, x: &Uuid);

fn push_nbt<T: Serialize>(&mut self, x: &T);

fn push_slot(&mut self, slot: Option<ItemStack>);

}

/// Identifies a type from which Minecraft-specified

/// types can be read.

pub trait McTypeRead {

/// Reads a `VarInt` from this object, returning

/// `Some(x)` if successful or `None` if the object

/// does not contain a valid `VarInt`.

fn try_get_var_int(&mut self) -> Result<i32, TryGetError>;

/// Reads a string from the object.

fn try_get_string(&mut self) -> Result<String, TryGetError>;

fn try_get_position(&mut self) -> Result<BlockPosition, TryGetError>;

fn try_get_bool(&mut self) -> Result<bool, TryGetError>;

fn try_get_uuid(&mut self) -> anyhow::Result<Uuid>;

fn try_get_nbt<T: DeserializeOwned>(&mut self) -> Result<T, nbt::Error>;

fn try_get_slot(&mut self) -> Result<Option<ItemStack>, TryGetError>;

}

impl McTypeWrite for BytesMut {

fn push_var_int(&mut self, mut x: i32) -> usize {

let mut bytes_written = 0;

loop {

let mut temp = (x & 0b0111_1111) as u8;

x >>= 7;

if x != 0 {

temp |= 0b1000_0000;

}

self.push_u8(temp);

bytes_written += 1;

if x == 0 {

break;

}

bytes_written

}

/// Writes a string to the object. This method

/// will first write the length of the string in bytes

/// encodes as a `VarInt` and will then write

/// the UTF-8 bytes of the string.

fn push_string(&mut self, x: &str) {

let bytes = x.as_bytes();

self.push_var_int(bytes.len() as i32);

self.extend_from_slice(bytes);

}

fn push_position(&mut self, x: &BlockPosition) {

let result: u64 = ((x.x as u64 & 0x03FF_FFFF) << 38)

| ((x.y as u64 & 0xFFF) << 26)

| (x.z as u64 & 0x03FF_FFFF);

self.push_u64(result);

}

fn push_bool(&mut self, x: bool) {

if x {

self.push_u8(1);

} else {

self.push_u8(0);

}

fn push_uuid(&mut self, x: &Uuid) {

self.extend_from_slice(&x.as_bytes()[..]);

}

fn push_nbt<T: Serialize>(&mut self, val: &T) {

// TODO: fix inefficient use of temp buf.

let mut temp = vec![];

nbt::to_writer(&mut temp, val, None).unwrap(); // Unwrap is safe because writing would only fail if a struct couldn't be written

self.extend_from_slice(&temp);

}

fn push_slot(&mut self, slot: Option<ItemStack>) {

self.push_bool(slot.is_some());

if let Some(slot) = slot.as_ref() {

self.push_var_int(slot.ty.native_protocol_id());

self.push_i8(slot.amount as i8);

self.push_i8(0x00); // TAG_End - TODO item NBT support

}

impl<B: Buf + Read> McTypeRead for B {

/// Reads a `VarInt` from this object, returning

/// `Some(x)` if successful or `None` if the object

/// does not contain a valid `VarInt`.

fn try_get_var_int(&mut self) -> Result<i32, TryGetError> {

let mut num_read = 0;

let mut result = 0;

loop {

if self.remaining() == 0 {

return Err(TryGetError::NotEnoughBytes);

}

let read = self.try_get_u8()?;

let value = i32::from(read & 0b0111_1111);

result |= value.overflowing_shl(7u32 * num_read).0;

num_read += 1;

if num_read > 5 {

return Err(TryGetError::NotEnoughBytes);

}

if read & 0b1000_0000 == 0 {

break;

}

Ok(result)

}

/// Reads a string from the object.

fn try_get_string(&mut self) -> Result<String, TryGetError> {

let len = self.try_get_var_int();

if let Ok(len) = len {

// Check that the client isn't trying

// to make the server allocate ridiculous

// amounts of memory

if len > 32767 {

return Err(TryGetError::ValueTooLarge);

}

let mut result = String::with_capacity(len as usize);

for _ in 0..len {

let res = self.try_get_i8()? as u8;

result.push(res as char);

}

return Ok(result);

}

Err(TryGetError::NotEnoughBytes)

}

fn try_get_position(&mut self) -> Result<BlockPosition, TryGetError> {

let val = self.try_get_i64()?;

let x = val >> 38;

let y = (val >> 26) & 0xFFF;

let z = val << 38 >> 38;

Ok(BlockPosition::new(x as i32, y as i32, z as i32))

}

fn try_get_bool(&mut self) -> Result<bool, TryGetError> {

let byte = self.try_get_i8()?;

match byte {

0 => Ok(false),

1 => Ok(true),

x => Err(TryGetError::InvalidValue(i32::from(x))),

}

fn try_get_uuid(&mut self) -> anyhow::Result<Uuid> {

let mut bytes = [0u8; 16];

self.read_exact(&mut bytes)?;

Ok(Uuid::from_bytes(bytes))

}

fn try_get_nbt<D: DeserializeOwned>(&mut self) -> Result<D, nbt::Error> {

nbt::from_reader(self)

}

fn try_get_slot(&mut self) -> Result<Option<ItemStack>, TryGetError> {

let present = self.try_get_bool()?;

if !present {

return Ok(None);

}

let id = self.try_get_var_int()?;

let ty = Item::from_native_protocol_id(id).ok_or(TryGetError::InvalidValue(id))?;

let amount = self.try_get_i8()? as u8;

// TODO NBT support

Ok(Some(ItemStack::new(ty, amount)))

}

#[cfg(test)]

mod tests {

use super::*;

use std::io::Cursor;

#[test]

fn test_read_var_int() {

// Examples from wiki.vg

let mut buf = BytesMut::new();

buf.extend_from_slice(&[0xff, 0x01]);

assert_eq!(Cursor::new(&buf).try_get_var_int(), Ok(255));

}

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