rustis 0.22.0

#[cfg(test)]
use crate::resp::next_sequence_counter;
use crate::resp::{ArgLayout, ArgsLayout, Command, cmd};
use bytes::{BufMut, BytesMut};
use dtoa::Float;
use itoa::Integer;
use serde::{Serialize, Serializer, ser};
use smallvec::SmallVec;
use std::{fmt::Error, ops::Range};

pub struct FastPathCommandBuilder {
    buffer: BytesMut,
    name_layout: (usize, usize),
    args_layout: ArgsLayout,
    is_readonly: bool,
}

impl FastPathCommandBuilder {
    #[inline(always)]
    pub fn new(header: &[u8], name_layout: (usize, usize)) -> Self {
        let mut buffer = BytesMut::with_capacity(128);
        buffer.put_slice(header);

        FastPathCommandBuilder {
            buffer,
            name_layout,
            args_layout: SmallVec::new(),
            is_readonly: false,
        }
    }

    /// Declares the command as read-only, like [`CommandBuilder::readonly`](crate::resp::CommandBuilder::readonly).
    #[inline(always)]
    fn readonly(mut self) -> Self {
        self.is_readonly = true;
        self
    }

    /// Serializes `arg` onto the fast path, returning the builder on success or
    /// `Err` on any non-primitive. The caller falls back to the generic builder
    /// rather than panicking.
    #[inline(always)]
    fn try_arg(mut self, arg: impl Serialize) -> Result<Self, Error> {
        let mut serializer = FastPathRespSerializer::new(&mut self.buffer);
        let range = arg.serialize(&mut serializer)?;

        self.args_layout.push(ArgLayout::arg(range));
        Ok(self)
    }

    /// Same as [`Self::try_arg`] for a key, marking it for Cluster routing. The
    /// CRC16 slot is computed later by [`Command::compute_slots`], on the caller
    /// thread and only in Cluster mode.
    #[inline(always)]
    fn try_key(mut self, key: impl Serialize) -> Result<Self, Error> {
        let mut serializer = FastPathRespSerializer::new(&mut self.buffer);
        let range = key.serialize(&mut serializer)?;

        self.args_layout.push(ArgLayout::key(range));
        Ok(self)
    }

    #[inline(always)]
    pub fn build(self) -> Command {
        Command::new(
            self.buffer.freeze(),
            self.name_layout,
            self.args_layout,
            #[cfg(test)]
            0,
            #[cfg(test)]
            0,
            #[cfg(test)]
            next_sequence_counter(),
            None,
            None,
            0,
            self.is_readonly,
        )
    }

    #[inline(always)]
    pub fn get(key: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*2\r\n$3\r\nGET\r\n", (8, 3)).try_key(&key) {
            Ok(builder) => builder.readonly().build(),
            Err(_) => cmd("GET").key(key).readonly().into(),
        }
    }

    #[inline(always)]
    pub fn set(key: impl Serialize, value: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$3\r\nSET\r\n", (8, 3))
            .try_key(&key)
            .and_then(|b| b.try_arg(&value))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("SET").key(key).arg(value).into(),
        }
    }

    #[inline(always)]
    pub fn expire(key: impl Serialize, seconds: u64) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$6\r\nEXPIRE\r\n", (8, 6))
            .try_key(&key)
            .and_then(|b| b.try_arg(seconds))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("EXPIRE").key(key).arg(seconds).into(),
        }
    }

    #[inline(always)]
    pub fn hget(key: impl Serialize, field: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$4\r\nHGET\r\n", (8, 4))
            .try_key(&key)
            .and_then(|b| b.try_arg(&field))
        {
            Ok(builder) => builder.readonly().build(),
            Err(_) => cmd("HGET").key(key).arg(field).readonly().into(),
        }
    }

    #[inline(always)]
    pub fn hincrby(key: impl Serialize, field: impl Serialize, increment: i64) -> Command {
        match FastPathCommandBuilder::new(b"*4\r\n$7\r\nHINCRBY\r\n", (8, 7))
            .try_key(&key)
            .and_then(|b| b.try_arg(&field))
            .and_then(|b| b.try_arg(increment))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("HINCRBY").key(key).arg(field).arg(increment).into(),
        }
    }

    #[inline(always)]
    pub fn sismember(key: impl Serialize, member: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$9\r\nSISMEMBER\r\n", (8, 9))
            .try_key(&key)
            .and_then(|b| b.try_arg(&member))
        {
            Ok(builder) => builder.readonly().build(),
            Err(_) => cmd("SISMEMBER").key(key).arg(member).readonly().into(),
        }
    }

    #[inline(always)]
    pub fn zincrby(key: impl Serialize, increment: f64, member: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*4\r\n$7\r\nZINCRBY\r\n", (8, 7))
            .try_key(&key)
            .and_then(|b| b.try_arg(increment))
            .and_then(|b| b.try_arg(&member))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("ZINCRBY").key(key).arg(increment).arg(member).into(),
        }
    }

    #[inline(always)]
    pub fn publish(channel: impl Serialize, message: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$7\r\nPUBLISH\r\n", (8, 7))
            .try_arg(&channel)
            .and_then(|b| b.try_arg(&message))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("PUBLISH").arg(channel).arg(message).into(),
        }
    }

    #[inline(always)]
    pub fn lpush(key: impl Serialize, element: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$5\r\nLPUSH\r\n", (8, 5))
            .try_key(&key)
            .and_then(|b| b.try_arg(&element))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("LPUSH").key(key).arg(element).into(),
        }
    }

    #[inline(always)]
    pub fn rpush(key: impl Serialize, element: impl Serialize) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$5\r\nRPUSH\r\n", (8, 5))
            .try_key(&key)
            .and_then(|b| b.try_arg(&element))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("RPUSH").key(key).arg(element).into(),
        }
    }

    #[inline(always)]
    pub fn lpop(key: impl Serialize, count: u32) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$4\r\nLPOP\r\n", (8, 4))
            .try_key(&key)
            .and_then(|b| b.try_arg(count))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("LPOP").key(key).arg(count).into(),
        }
    }

    #[inline(always)]
    pub fn rpop(key: impl Serialize, count: u32) -> Command {
        match FastPathCommandBuilder::new(b"*3\r\n$4\r\nRPOP\r\n", (8, 4))
            .try_key(&key)
            .and_then(|b| b.try_arg(count))
        {
            Ok(builder) => builder.build(),
            Err(_) => cmd("RPOP").key(key).arg(count).into(),
        }
    }
}

struct FastPathRespSerializer<'a> {
    buffer: &'a mut BytesMut,
}

impl<'a> FastPathRespSerializer<'a> {
    #[inline(always)]
    pub(crate) fn new(buffer: &'a mut BytesMut) -> Self {
        FastPathRespSerializer { buffer }
    }

    #[inline(always)]
    fn serialize_integer<I: Integer>(&mut self, i: I) -> Range<usize> {
        let mut buf = itoa::Buffer::new();
        self.write_arg(buf.format(i).as_bytes())
    }

    #[inline(always)]
    fn serialize_float<F: Float>(&mut self, f: F) -> Range<usize> {
        let mut buf = dtoa::Buffer::new();
        self.write_arg(buf.format(f).as_bytes())
    }

    /// Serializes a raw argument into the buffer using RESP format (BulkString).
    ///
    /// # Format
    /// `$Length\r\nData\r\n`
    #[inline]
    #[expect(
        clippy::arithmetic_side_effects,
        reason = "the header adds a fixed handful of bytes to the length of a slice \
                  that is already allocated, and the payload range ends where the \
                  bytes just written end."
    )]
    pub(crate) fn write_arg(&mut self, data: &[u8]) -> Range<usize> {
        // 1. Write the RESP BulkString header ($Len\r\n)
        let data_len = data.len();
        let mut len_buf = itoa::Buffer::new();
        let len_str = len_buf.format(data_len);
        let len_bytes = len_str.as_bytes();
        let total_size = 1 + len_bytes.len() + 2 + data_len + 2;
        self.buffer.reserve(total_size);
        self.buffer.put_u8(b'$');
        self.buffer.put_slice(len_bytes);
        self.buffer.put_slice(b"\r\n");

        // 2. Capture the absolute position of the data for the index
        let start_pos = self.buffer.len();

        // 3. Write the actual data
        self.buffer.put_slice(data);
        self.buffer.put_slice(b"\r\n");

        // 4. return the layout range
        start_pos..start_pos + data_len
    }
}

impl<'a> Serializer for &'a mut FastPathRespSerializer<'a> {
    type Ok = Range<usize>;
    type Error = Error;
    type SerializeSeq = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTuple = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTupleStruct = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTupleVariant = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeMap = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStruct = ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStructVariant = ser::Impossible<Self::Ok, Self::Error>;

    #[inline(always)]
    fn serialize_bool(self, v: bool) -> Result<Self::Ok, Self::Error> {
        Ok(self.write_arg(if v { b"1" } else { b"0" }))
    }

    #[inline(always)]
    fn serialize_i8(self, v: i8) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_i16(self, v: i16) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_i32(self, v: i32) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_u8(self, v: u8) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_u16(self, v: u16) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_u32(self, v: u32) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_integer(v))
    }

    #[inline(always)]
    fn serialize_f32(self, v: f32) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_float(v))
    }

    #[inline(always)]
    fn serialize_f64(self, v: f64) -> Result<Self::Ok, Self::Error> {
        Ok(self.serialize_float(v))
    }

    #[inline(always)]
    fn serialize_char(self, v: char) -> Result<Self::Ok, Self::Error> {
        let mut buf = [0; 4];
        let str = v.encode_utf8(&mut buf);
        Ok(self.write_arg(str.as_bytes()))
    }

    #[inline(always)]
    fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error> {
        Ok(self.write_arg(v.as_bytes()))
    }

    #[inline(always)]
    fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok, Self::Error> {
        Ok(self.write_arg(v))
    }

    #[inline(always)]
    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    #[inline(always)]
    fn serialize_some<T: ?Sized + Serialize>(self, value: &T) -> Result<Self::Ok, Self::Error> {
        value.serialize(self)
    }

    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<Self::Ok, Self::Error> {
        self.serialize_str(variant)
    }

    fn serialize_newtype_struct<T: ?Sized + Serialize>(
        self,
        _name: &'static str,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        value.serialize(self)
    }

    fn serialize_newtype_variant<T>(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _value: &T,
    ) -> Result<Self::Ok, Self::Error>
    where
        T: ?Sized + Serialize,
    {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStruct, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }

    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant, Self::Error> {
        Err(ser::Error::custom("FastPath only supports primitives"))
    }
}

#[cfg(test)]
mod tests {
    #![allow(
        clippy::unwrap_used,
        clippy::expect_used,
        clippy::panic,
        clippy::unreachable,
        clippy::indexing_slicing,
        reason = "test code: a panic is how a test reports failure"
    )]
    use super::FastPathCommandBuilder;

    #[test]
    fn primitive_args_stay_on_the_fast_path() {
        // Regression guard: the common primitive case must keep working exactly
        // as before the fallback was added.
        let command = FastPathCommandBuilder::set("key", "value");
        assert_eq!(b"SET", command.name());
        assert_eq!(2, command.num_args());
        assert_eq!(Some(&b"key"[..]), command.get_arg(0).as_deref());
        assert_eq!(Some(&b"value"[..]), command.get_arg(1).as_deref());
    }

    #[test]
    fn none_argument_falls_back_instead_of_panicking() {
        // `set(key, None::<String>)` used to panic the caller thread. It must now
        // fall back to the generic builder, which drops the None as a no-op (a
        // caller-visible arity error from Redis, not a panic).
        let command = FastPathCommandBuilder::set("key", None::<String>);
        assert_eq!(b"SET", command.name());
        assert_eq!(1, command.num_args());
        assert_eq!(Some(&b"key"[..]), command.get_arg(0).as_deref());
        assert_eq!(None, command.get_arg(1));
    }

    #[test]
    fn collection_argument_falls_back_to_a_flattened_command() {
        // `lpush(key, vec!["a","b"])` used to panic. The generic builder
        // flattens the sequence into a correct multi-element LPUSH.
        let command = FastPathCommandBuilder::lpush("key", vec!["a", "b"]);
        assert_eq!(b"LPUSH", command.name());
        assert_eq!(3, command.num_args());
        assert_eq!(Some(&b"key"[..]), command.get_arg(0).as_deref());
        assert_eq!(Some(&b"a"[..]), command.get_arg(1).as_deref());
        assert_eq!(Some(&b"b"[..]), command.get_arg(2).as_deref());
    }

    #[test]
    fn some_primitive_still_serializes_on_the_fast_path() {
        // `serialize_some` delegates, so `Some(primitive)` stays on the fast
        // path — only `None` degrades.
        let command = FastPathCommandBuilder::set("key", Some("value"));
        assert_eq!(2, command.num_args());
        assert_eq!(Some(&b"value"[..]), command.get_arg(1).as_deref());
    }
}