iscsi-client-rs 0.0.4

use anyhow::{Result, bail};

use crate::{
    client::pdu_connection::FromBytes,
    models::{
        command::common::{ScsiCommandRequestFlags, TaskAttribute},
        common::{BasicHeaderSegment, HEADER_LEN, SendingData},
        opcode::{BhsOpcode, IfFlags, Opcode},
    },
};

/// BHS for ScsiCommandRequest PDU
#[repr(C)]
#[derive(Debug, Default, PartialEq)]
pub struct ScsiCommandRequest {
    pub opcode: BhsOpcode,                  // 0
    pub flags: ScsiCommandRequestFlags,     // 1
    reserved1: [u8; 2],                     // 2..4
    pub total_ahs_length: u8,               // 4
    pub data_segment_length: [u8; 3],       // 5..8
    pub lun: [u8; 8],                       // 8..16
    pub initiator_task_tag: u32,            // 16..20
    pub expected_data_transfer_length: u32, // 20..24
    pub cmd_sn: u32,                        // 24..28
    pub exp_stat_sn: u32,                   // 28..32
    pub scsi_descriptor_block: [u8; 16],    // 32..48
}

impl ScsiCommandRequest {
    pub const DEFAULT_TAG: u32 = 0xffffffff_u32;

    /// Serialize BHS in 48 bytes
    pub fn to_bhs_bytes(&self) -> [u8; HEADER_LEN] {
        let mut buf = [0u8; HEADER_LEN];
        buf[0] = (&self.opcode).into();
        buf[1] = self.flags.bits();
        buf[2..4].copy_from_slice(&self.reserved1);
        buf[4] = self.total_ahs_length;
        buf[5..8].copy_from_slice(&self.data_segment_length);
        buf[8..16].copy_from_slice(&self.lun);
        buf[16..20].copy_from_slice(&self.initiator_task_tag.to_be_bytes());
        buf[20..24].copy_from_slice(&self.expected_data_transfer_length.to_be_bytes());
        buf[24..28].copy_from_slice(&self.cmd_sn.to_be_bytes());
        buf[28..32].copy_from_slice(&self.exp_stat_sn.to_be_bytes());
        buf[32..48].copy_from_slice(&self.scsi_descriptor_block);
        buf
    }

    pub fn from_bhs_bytes(buf: &[u8]) -> Result<Self> {
        if buf.len() < HEADER_LEN {
            bail!("buffer too small");
        }
        let opcode = BhsOpcode::try_from(buf[0])?;
        if opcode.opcode != Opcode::ScsiCommandReq {
            bail!("ScsiCommandReq invalid opcode: {:?}", opcode.opcode);
        }
        let flags = ScsiCommandRequestFlags::try_from(buf[1])?;
        let total_ahs_length = buf[4];
        let data_segment_length = [buf[5], buf[6], buf[7]];
        let mut lun = [0u8; 8];
        lun.clone_from_slice(&buf[8..16]);
        let initiator_task_tag = u32::from_be_bytes(buf[16..20].try_into()?);
        let expected_data_transfer_length = u32::from_be_bytes(buf[20..24].try_into()?);
        let cmd_sn = u32::from_be_bytes(buf[24..28].try_into()?);
        let exp_stat_sn = u32::from_be_bytes(buf[28..32].try_into()?);
        let mut scsi_descriptor_block = [0u8; 16];
        scsi_descriptor_block.clone_from_slice(&buf[32..48]);

        Ok(ScsiCommandRequest {
            opcode,
            flags,
            reserved1: [0u8; 2],
            total_ahs_length,
            lun,
            data_segment_length,
            initiator_task_tag,
            expected_data_transfer_length,
            cmd_sn,
            exp_stat_sn,
            scsi_descriptor_block,
        })
    }
}

/// Builder for **SCSI Command** PDUs (opcode `0x01`).
///
/// This helper constructs the Basic Header Segment (BHS) for a SCSI command
/// sent over iSCSI. It lets you set the common fields (LUN, ITT, CmdSN,
/// ExpStatSN, 16-byte CDB, task attributes, and READ/WRITE/Immediate flags)
/// and, when needed, request header/data digests for serialization.
///
/// Notes & conventions:
/// - The 16-byte **CDB** is copied verbatim into the header. For READ(10) or
///   WRITE(10) you typically pad your 10-byte CDB to 16 bytes.
/// - **expected_data_transfer_length** is the total payload you expect to move:
///   * For **Data-Out** (WRITE) it should match the number of bytes you will
///     actually send in subsequent Data-Out PDUs (unsolicited or per R2T).
///   * For **Data-In** (READ) it announces how many bytes you expect to receive
///     and is used for residual accounting by the target.
/// - **Immediate (I)** sets bit 6 in the opcode byte. Whether the target
///   processes immediate commands depends on negotiated parameters.
/// - **TaskAttribute** encodes SIMPLE/ORDERED/HEAD_OF_QUEUE/ACA into the low
///   bits of the flags field (per SPC/SAM).
/// - Enabling **Header/Data Digest** here only toggles intent for the
///   serialization layer; it does not modify BHS fields directly.
#[derive(Debug, Default, PartialEq)]
pub struct ScsiCommandRequestBuilder {
    pub header: ScsiCommandRequest,
    enable_header_digest: bool,
    enable_data_digest: bool,
}

impl ScsiCommandRequestBuilder {
    pub fn new() -> Self {
        ScsiCommandRequestBuilder {
            header: ScsiCommandRequest {
                opcode: BhsOpcode {
                    flags: IfFlags::empty(),
                    opcode: Opcode::ScsiCommandReq,
                },
                ..Default::default()
            },
            enable_data_digest: false,
            enable_header_digest: false,
        }
    }

    /// Set Immediate bit (Immediate = bit6)
    pub fn immediate(mut self) -> Self {
        self.header.opcode.flags.insert(IfFlags::I);
        self
    }

    /// Set Read bit
    pub fn read(mut self) -> Self {
        self.header.flags.insert(ScsiCommandRequestFlags::READ);
        self
    }

    /// Set Read bit
    pub fn write(mut self) -> Self {
        self.header.flags.insert(ScsiCommandRequestFlags::WRITE);
        self
    }

    /// Set TaskTag bits
    pub fn task_attribute(mut self, task: TaskAttribute) -> Self {
        let raw_attr: u8 = task.into();
        let old = self.header.flags.bits();
        let cleared = old & !ScsiCommandRequestFlags::ATTR_MASK.bits();
        let new_bits = cleared | (raw_attr & ScsiCommandRequestFlags::ATTR_MASK.bits());
        self.header.flags = ScsiCommandRequestFlags::from_bits_truncate(new_bits);
        self
    }

    /// Enable HeaderDigest in NOP-Out.
    pub fn with_header_digest(mut self) -> Self {
        self.enable_header_digest = true;
        self
    }

    /// Enable DataDigest in NOP-Out.
    pub fn with_data_digest(mut self) -> Self {
        self.enable_data_digest = true;
        self
    }

    /// Sets the initiator task tag, a unique identifier for this command.
    pub fn initiator_task_tag(mut self, tag: u32) -> Self {
        self.header.initiator_task_tag = tag;
        self
    }

    /// Sets the expected_data_length, a length off all parts of data.
    pub fn expected_data_transfer_length(mut self, expected_data_length: u32) -> Self {
        self.header.expected_data_transfer_length = expected_data_length;
        self
    }

    /// Sets the command sequence number (CmdSN) for this request.
    pub fn cmd_sn(mut self, sn: u32) -> Self {
        self.header.cmd_sn = sn;
        self
    }

    /// Sets the expected status sequence number (ExpStatSN) from the target.
    pub fn exp_stat_sn(mut self, sn: u32) -> Self {
        self.header.exp_stat_sn = sn;
        self
    }

    /// Set the 8-byte Logical Unit Number (LUN) in the BHS header.
    pub fn lun(mut self, lun: &[u8; 8]) -> Self {
        self.header.lun.clone_from_slice(lun);
        self
    }

    /// Set the 16-byte SCSI Command Descriptor Block (CDB) in the BHS header.
    pub fn scsi_descriptor_block(mut self, scsi_descriptor_block: &[u8; 16]) -> Self {
        self.header
            .scsi_descriptor_block
            .clone_from_slice(scsi_descriptor_block);
        self
    }
}

impl SendingData for ScsiCommandRequest {
    fn get_final_bit(&self) -> bool {
        self.flags.contains(ScsiCommandRequestFlags::FINAL)
    }

    fn set_final_bit(&mut self) {
        self.flags.insert(ScsiCommandRequestFlags::FINAL);
    }

    fn get_continue_bit(&self) -> bool {
        !self.flags.contains(ScsiCommandRequestFlags::FINAL)
    }

    fn set_continue_bit(&mut self) {
        self.flags.remove(ScsiCommandRequestFlags::FINAL);
    }
}

impl FromBytes for ScsiCommandRequest {
    fn from_bhs_bytes(bytes: &[u8]) -> Result<Self> {
        Self::from_bhs_bytes(bytes)
    }
}

impl BasicHeaderSegment for ScsiCommandRequest {
    fn to_bhs_bytes(&self) -> Result<[u8; HEADER_LEN]> {
        Ok(self.to_bhs_bytes())
    }

    fn get_opcode(&self) -> &BhsOpcode {
        &self.opcode
    }

    fn get_initiator_task_tag(&self) -> u32 {
        self.initiator_task_tag
    }

    fn get_ahs_length_bytes(&self) -> usize {
        (self.total_ahs_length as usize) * 4
    }

    fn set_ahs_length_bytes(&mut self, len: u8) {
        self.total_ahs_length = len >> 2;
    }

    fn get_data_length_bytes(&self) -> usize {
        u32::from_be_bytes([
            0,
            self.data_segment_length[0],
            self.data_segment_length[1],
            self.data_segment_length[2],
        ]) as usize
    }

    fn set_data_length_bytes(&mut self, len: u32) {
        let be = len.to_be_bytes();
        self.data_segment_length = [be[1], be[2], be[3]];
    }
}