/*!
    SII (Slave Information Interface) allows to retreive from EEPROM declarative informations about a slave (like a manifest) like product code, vendor, etc as well as slave boot-up configs.

    The EEPROM can also store configurations variables for the specific slaves purpose (like control loop coefficients, safety settings, etc) but these values are vendor-specific and often now meant for user inspection through the SII. They are still accessible using the tools provided here, but not structure is provided to interpret them.

    ETG.1000.4.6.6.4, ETG.2010

    This module features [Sii] and [SiiCursor] in order to read/write and parse the eeprom data

    The EEPROM has 2 regions of data:

    - EEPROM registers: fixed addresses, described in [eeprom] and accessed by [`Sii`]
    - EEPROM categories: contiguous data blocks, described by [`Category`] and accessed by [`SiiCursor`]

    Here is how to use registers:
    ```ignore
    sii.acquire().await?;
    let vendor = sii.read(eeprom::device::vendor).await?;
    let alias = sii.read(eeprom::address_alias).await?;
    sii.release().await?;
    ```

    Here is how to parse the categories:
    ```ignore
    sii.acquire().await?;
    let mut categories = sii.categories();
    let general = loop {
        let category = categories.unpack::<Category>().await?;
        // we got our desired category, do something with it
        if category.ty() == CategoryType::General {
            // we can then read the category (or at least its header) as a register
            break Ok(categories.unpack::<General>().await?)
        }
        // end of eeprom reached
        else if category.ty() == CategoryType::End {
            break Err(EthercatError::Master("no general category in EEPROM"))
        }
        // or squeeze the current category
        else {
            categories.advance(WORD*category.size());
        }
    };
    sii.release().await?;
    ```
*/

use crate::{
    error::{EthercatError, EthercatResult},
    data::{self, PduData, Storage, Field, Cursor},
    rawmaster::{RawMaster, SlaveAddress},
    registers,
    eeprom,
    };
use std::sync::Arc;
use bilge::prelude::*;


pub const WORD: u16 = eeprom::WORD as _;


/**
    implementation of the Slave Information Interface (SII) to communicate with a slave's EEPROM memory

    The EEPROM has 2 regions of data:

    - EEPROM registers: at fixed addresses, described in [eeprom]
    - EEPROM categories: as contiguous data blocks, starting from fixed address [eeprom::categories]

    This struct is providing access to both, but only works with fixed addresses. To parse the categories, use a cursor returned by [Self::categories] then parse the structures iteratively.

    A `Sii` instance is generally obtained from [Slave::sii](crate::Slave::sii)
*/
pub struct Sii {
    master: Arc<RawMaster>,
    slave: SlaveAddress,
    /// address mask (part of the address actually used by the slave)
    mask: u16,
    /// whether the EEPROM is writable through the SII
    writable: bool,
    /// whether the master owns access to the SII (and EEPROM)
    locked: bool,
}
impl Sii {
    /**
        create an instance of this struct to use the SII of the given slave

        to stay protocol-safe, one instance of this struct only should exist per slave.

        At contrary to the EEPROM addresses used at the ethercat communication level, this struct and its methods only use byte addresses, write requests should be word-aligned.
    */
    pub async fn new(master: Arc<RawMaster>, slave: SlaveAddress) -> EthercatResult<Sii, SiiError> {
        let status = master.read(slave, registers::sii::control).await.one()?;
        let mask = match status.address_unit() {
            registers::SiiUnit::Byte => 0xff,
            registers::SiiUnit::Word => 0xffff,
        };
        if status.checksum_error()
            {return Err(EthercatError::Slave(slave, SiiError::Checksum))};
        Ok(Self {
            master,
            slave,
            mask,
            writable: status.write_access(),
            locked: false,
            })
    }
    /// tells if the EEPROM is writable through the SII
    pub fn writable(&self) -> bool {self.writable}

    /**
        acquire the SII so we can use it through the registers

        The access to the EEPROM is always made through the SII, even internally for the slave, which mean for the slave to access its EEPROM, the master should not have it.

        the access need to be acquired by the master before it to read or write to the EEPROM. Any attempt without acquiring it will fail
    */
    pub async fn acquire(&mut self) -> EthercatResult {
        if ! self.locked {
            self.locked = true;
            self.master.write(self.slave, registers::sii::access, {
                let mut config = registers::SiiAccess::default();
                config.set_owner(registers::SiiOwner::EthercatDL);
                config
                }).await.one()?;
        }
        Ok(())
    }
    /**
        release the SII to the device internal control

        The access to the EEPROM usually needs to be released during slave initialization steps (meaning for state transitions). Most attempt to initialize without releasing will certainly fail.
    */
    pub async fn release(&mut self) -> EthercatResult {
        if self.locked {
            self.locked = false;
            self.master.write(self.slave, registers::sii::access, {
                let mut config = registers::SiiAccess::default();
                config.set_owner(registers::SiiOwner::Pdi);
                config
                }).await.one()?;
        }
        Ok(())
    }
    
    /// read data from the slave's EEPROM using the SII
    pub async fn read<T: PduData>(&mut self, field: Field<T>) -> EthercatResult<T, SiiError> {
        let mut buffer = T::Packed::uninit();
        self.read_slice(field.byte as _, buffer.as_mut()).await?;
        Ok(T::unpack(buffer.as_ref())?)
    }
    /// read a slice of the slave's EEPROM memory
    pub async fn read_slice<'b>(&mut self, address: u16, value: &'b mut [u8]) -> EthercatResult<&'b [u8], SiiError> {
        // some slaves use 2 byte addresses but declare they are using 1 only, so disable this check for now
        if address & !self.mask != 0
            {return Err(EthercatError::Master("wrong EEPROM address: address range is 1 byte only"))}

        let mut start = (address % WORD) as usize;
        let mut cursor = Cursor::new(value.as_mut());
        while cursor.remain().len() != 0 {
            // send request
            self.master.write(self.slave, registers::sii::control_address, registers::SiiControlAddress {
                control: {
                    let mut control = registers::SiiControl::default();
                    control.set_read_operation(true);
                    control
                },
                address: (address + cursor.position() as u16) / WORD,
            }).await.one()?;
            // wait for interface to become available
            let status = loop {
                if let Ok(answer) = self.master.read(self.slave, registers::sii::control).await.one() {
                    if ! answer.busy()  && ! answer.read_operation()
                        {break answer}
                }
            };
            // check for errors
            if status.command_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::Command))}
            if status.device_info_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::DeviceInfo))}

            // buffer the result
            let size = match status.read_size() {
                registers::SiiTransaction::Bytes4 => 4,
                registers::SiiTransaction::Bytes8 => 8,
                }.min(start + cursor.remain().len());
            let data = self.master.read(self.slave, registers::sii::data).await.one()?;
            cursor.write(&data[start .. size]).unwrap();
            start = 0;
        }
        Ok(value)
    }

    /**
        write data to the slave's EEPROM using the SII

        this will only work if [Self::writable], else will raise an error
    */
    pub async fn write<T: PduData>(&mut self, field: Field<T>, value: &T) -> EthercatResult<(), SiiError> {
        let mut buffer = T::Packed::uninit();
        value.pack(buffer.as_mut()).unwrap();
        self.write_slice(field.byte as _, buffer.as_ref()).await
    }
    /**
        write the given slice of data in the slave's EEPROM

        this will only work if [Self::writable], else will raise an error
    */
    pub async fn write_slice(&mut self, address: u16, value: &[u8]) -> EthercatResult<(), SiiError> {
        if address % WORD != 0
            {return Err(EthercatError::Master("address must be word-aligned"))}
        // some slaves use 2 byte addresses but declare they are using 1 only, so disable this check for now
//         if address & !self.mask != 0
//             {return Err(EthercatError::Master("wrong EEPROM address: address range is 1 byte only"))}

        let mut cursor = Cursor::new(value.as_ref());
        while cursor.remain().len() != 0 {
            // write operation is forced to be 2 bytes (ETG.1000.4 6.4.5)
            // send request
            self.master.write(self.slave, registers::sii::control_address_data, registers::SiiControlAddressData {
                control: {
                    let mut control = registers::SiiControl::default();
                    control.set_write_operation(true);
                    control
                },
                address: (address + cursor.position() as u16) / WORD,
                reserved: 0,
                data: cursor.unpack().unwrap(),
            }).await.one()?;

            // wait for interface to become available
            let status = loop {
                if let Ok(answer) = self.master.read(self.slave, registers::sii::control).await.one() {
                    if ! answer.busy()  && ! answer.write_operation()
                        {break answer}
                }
            };
            // check for errors
            if status.command_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::Command))}
            if status.write_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::Write))}
        }
        Ok(())
    }

    /// reload first 128 bits of data from the EEPROM
    pub async fn reload(&mut self) -> EthercatResult<(), SiiError> {
        self.master.write(self.slave, registers::sii::control, {
            let mut control = registers::SiiControl::default();
            control.set_reload_operation(true);
            control
        }).await.one()?;

        // wait for interface to become available
        let status = loop {
            if let Ok(answer) = self.master.read(self.slave, registers::sii::control).await.one() {
                if ! answer.busy() && ! answer.reload_operation()
                    {break answer}
            }
        };
        // check for errors
        if status.command_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::Command))}
        if status.checksum_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::Checksum))}
        if status.device_info_error()
                {return Err(EthercatError::Slave(self.slave, SiiError::DeviceInfo))}
        Ok(())
    }
    
    /// cursor pointing at the start of categories. See [Category]
    pub fn categories(&mut self) -> SiiCursor<'_> {
        SiiCursor::new(self, eeprom::categories)
    }

    /**
        read the strings category of the EEPROM, and return its content as rust datatype

        these strings are usually pointed to by sdo values or other fields in the EEPROM's categories
    */
    pub async fn strings(&mut self) -> EthercatResult<Vec<String>, SiiError> {
        let mut categories = self.categories();
        loop {
            let category = categories.unpack::<Category>().await?;
            if category.ty() == CategoryType::Strings {
                let num = categories.unpack::<u8>().await?;
                let mut strings = Vec::with_capacity(num as _);

                for _ in 0 .. num {
                    // string length in byte
                    let len = categories.unpack::<u8>().await?;
                    // read string
                    let mut buffer = vec![0; len as _];
                    categories.read(&mut buffer).await?;
                    strings.push(String::from_utf8(buffer)
                        .map_err(|_|  EthercatError::<SiiError>::Master("strings in EEPROM are not UTF8"))?
                        );
                }

                return Ok(strings)
            }
            else if category.ty() == CategoryType::End {
                return Err(EthercatError::Master("no strings category in EEPROM"))
            }
            else {
                categories.advance(WORD*category.size());
            }
        }
    }

    /// readthe general informations category of the EEPROM and return its content
    pub async fn generals(&mut self) -> EthercatResult<General, SiiError> {
        let mut categories = self.categories();
        loop {
            let category = categories.unpack::<Category>().await?;
            if category.ty() == CategoryType::General {
                return categories.unpack::<General>().await
            }
            else if category.ty() == CategoryType::End {
                return Err(EthercatError::Master("no general category in EEPROM"))
            }
            else {
                categories.advance(WORD*category.size());
            }
        }
    }
}

/**
    Helper for parsing the category of the eeprom through the SII

    It is inspired from [data::Cursor] but this one directly reads into the EEPROM rather than in a local buffer
*/
pub struct SiiCursor<'a> {
    sii: &'a mut Sii,
    position: u16,
    end: u16,
}
impl<'a> SiiCursor<'a> {
    /// initialize at the given byte position in the EEPROM
    pub fn new(sii: &'a mut Sii, position: u16) -> Self
        {Self {sii, position, end: u16::MAX}}
    /// byte position in the EEPROM
    pub fn position(&self) -> u16
        {self.position}
    /// number of bytes remaining before region end
    pub fn remain(&self) -> u16
        {self.end.max(self.position) - self.position}

    /// create a new instance of cursor at the same location, it is only meant to ease practice of parsing multiple time the same region
    pub fn shadow(&mut self) -> SiiCursor<'_> {
        SiiCursor {
            sii: self.sii,
            position: self.position,
            end: self.end,
            }
    }
    /// create a new instance of cursor at the same location but ending after size, moving the the current cursor after size. it is only meant to ease preactice of isolating parsing a section from a parent section
    pub fn sub(&mut self, size: u16) -> SiiCursor<'_> {
        let position = self.position;
        self.position += size;
        SiiCursor {
            sii: self.sii,
            position,
            end: self.position,
            }
    }
    /// advance byte position of the given increment
    pub fn advance(&mut self, increment: u16) {
        self.position += increment;
    }
    /// read bytes filling the given slice and advance the position
    pub async fn read(&mut self, dst: &mut [u8]) -> EthercatResult<(), SiiError> {
        self.sii.read_slice(self.position, dst).await?;
        self.position += dst.len() as u16;
        Ok(())
    }
    /// read the given data and advance the position
    pub async fn unpack<T: PduData>(&mut self) -> EthercatResult<T, SiiError> {
        let mut buffer = T::Packed::uninit();
        self.read(buffer.as_mut()).await?;
        Ok(T::unpack(buffer.as_ref())?)
    }
    /// write the given bytes and advance the position
    pub async fn write(&mut self, dst: &[u8]) -> EthercatResult<(), SiiError> {
        self.sii.write_slice(self.position, dst).await?;
        self.position += dst.len() as u16;
        Ok(())
    }
    /// write the given data and advance the position
    pub async fn pack<T: PduData>(&mut self, value: T) -> EthercatResult<(), SiiError> {
        let mut buffer = T::Packed::uninit();
        value.pack(buffer.as_mut()).unwrap();
        self.write(buffer.as_ref()).await
    }
}

/// error raised by the SII of a slave
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum SiiError {
    /// bad SII command
    Command,
    /// EEPROM data has been corrupted
    Checksum,
    /// bad data in device info section
    DeviceInfo,
    /// cannot write the requested location in EEPROM
    Write,
}

impl From<EthercatError<()>> for EthercatError<SiiError> {
    fn from(src: EthercatError<()>) -> Self {src.upgrade()}
}


/**
    header for a SII category
    
    ETG.1000.6 table 17

    A Category is an any-length data section starting by this struct as header.
    The category can be squeezed to read the next one by using its [size](Self::size), its content is idnetified by its [type](Self::ty)
*/
#[bitsize(32)]
#[derive(TryFromBits, DebugBits, Copy, Clone)]
pub struct Category {
    /// category type as defined in ETG.1000.6 Table 19
    pub ty: CategoryType,
    /// size in word of the category
    pub size: u16,
}
data::bilge_pdudata!(Category, u32);

/**
    type of category in the SII

    ETG.1000.6 table 19
*/
#[bitsize(16)]
#[derive(FromBits, Debug, Copy, Clone, Eq, PartialEq)]
pub enum CategoryType {
    Nop = 0,
    /**
        String repository for other Categories structure of this category data
        see ETG.1000.6 Table 20

        **section content:**

        ```ignore
            [num of strings: u8] ([byte length][bytes]) ([byte length][bytes]) ...
        ```
    */
    Strings = 10,
    /// Data Types for future use
    DataTypes = 20,
    /**
        General information structure of this category data. see ETG.1000.6 Table 21

        **section content:**  [`General`]
    */
    General = 30,
    /**
        FMMUs to be used structure of this category data. see ETG.1000.6 Table 23

        **section content:**  [`[FmmuUsage; _]`](FmmuUsage)
    */
    Fmmu = 40,
    /**
        second FMMU category added by ETG.2010 table 1

        **section content:**  [`[FmmuExtension; _]`](FmmuExtension)
    */
    FmmuExtension = 42,
    /**
        Sync Manager Configuration structure of this category data. see ETG.1000.6 Table 24

        **section content:**  [`[SyncManager; _]`](SyncManager)
    */
    SyncManager = 41,
    /**
        second sync manager category added by ETG.2010 table 1

        **section content:**  [`[SyncUnit; _]`](SyncUnit)
    */
    SyncUnit = 43,
    /**
        TxPDO description structure of this category data. see ETG.1000.6 Table 25

        **section content:**  [`[[Pdo][entries]; _]`](Pdo)
    */
    PdoWrite = 50,
    /**
        RxPDO description structure of this category data. see ETG.1000.6 Table 25

        **section content:**  [`[[Pdo][entries]; _]`](Pdo)
    */
    PdoRead = 51,
    /**
        Distributed Clock for future use

        **section content:**  [`DistributedClock`]
    */
    Dc = 60,

    #[fallback]
    Unsupported = 0x0800,

    /// mark the end of SII categories
    End = 0xffff,
}

/// ETG.1000.6 table 21
#[repr(packed)]
#[derive(Clone, Eq, PartialEq, Debug)]
pub struct General {
    /// Group Information (Vendor specific) - Index to STRINGS
    pub group: u8,
    /// Image Name (Vendor specific) - Index to STRINGS
    pub image: u8,
    /// Device Order Number (Vendor specific) - Index to STRINGS
    pub order: u8,
    /// Device Name Information (Vendor specific) - Index to STRINGS
    pub name: u8,
    _reserved0: u8,
    /// supported CoE features
    pub coe: CoeDetails,
    /// supported FoE features
    pub foe: FoeDetails,
    /// supported EoE features
    pub eoe: EoeDetails,
    _reserved1: [u8;3],
    pub flags: GeneralFlags,
    /// EBus Current Consumption in mA, negative Values means feeding in current feed in sets the available current value to the given value
    pub ebus_current: i16,
    /// Index to Strings – duplicate for compatibility reasons
    pub group2: u8,
    _reserved2: u8,
    /// Description of Physical Ports
    pub ports: PhysicialPorts,
    /// Element defines the ESC memory address where the Identification ID is saved if Identification Method = IdentPhyM
    pub identification_address: u16,
}
data::packed_pdudata!(General);

/// supported CoE features
#[bitsize(8)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct CoeDetails {
    pub sdo: bool,
    pub sdo_info: bool,
    pub pdo_assign: bool,
    pub pdo_config: bool,
    pub startup_upload: bool,
    pub sdo_complete: bool,
    _reserved: u2,
}
#[bitsize(8)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct FoeDetails {
    // protocol supported
    pub enable: bool,
    reserved: u7,
}
#[bitsize(8)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct EoeDetails {
    // protocol supported
    pub enable: bool,
    reserved: u7,
}
#[bitsize(8)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct GeneralFlags {
    pub enable_safeop: bool,
    pub enable_notlrw: bool,
    pub mbox_dll: bool,
    /// ID selector mirrored in AL Statud Code
    pub ident_alsts: bool,
    /// ID selector value mirrored in specific physical memory as deonted by the parameter “Physical Memory Address”
    pub ident_phym: bool,
    reserved: u3,
}

#[bitsize(16)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct PhysicialPorts {
    pub ports: [PhysicalPort; 4],
}
#[bitsize(4)]
#[derive(FromBits, Debug, Copy, Clone, Eq, PartialEq)]
pub enum PhysicalPort {
    #[fallback]
    Disabled = 0x0,
    /// media independent interface
    Mii = 0x1,
    Reserved = 0x2,
    Ebus = 0x3,
    /// NOTE: Fast Hot Connect means a Port with Ethernet Physical Layer and Autonegotiation off (100Mbps fullduplex)
    FastHotconnect = 0x4,
}

/// ETG.1000.6 table 23, ETG.2010 tablee 9
#[bitsize(8)]
#[derive(FromBits, Debug, Copy, Clone, Eq, PartialEq)]
pub enum FmmuUsage {
    #[fallback]
    Disabled = 0,
    Outputs = 1,
    Inputs = 2,
    SyncManagerStatus = 3,
}
data::bilge_pdudata!(FmmuUsage, u8);

/// ETG.2010 table 10
#[bitsize(24)]
#[derive(TryFromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct FmmuExtension {
    /**
        As SM.OpOnly obsolete

        Esi:DeviceType:Fmmu:OpOnly
    */
    pub op_only: bool,
    /**
        Mandatory if more than one FMMU for the same direction is used to map data to non-consecutive memory areas

        Assigns this FMMU to a SyncManager

        Esi: DeviceType:Fmmu:Sm
    */
    pub sm_defined: bool,
    /// Esi: DeviceType:Fmmu:Su
    pub su_defined: bool,
    reserved: u5,
    /**
        Assigns this FMMU to a SyncManager

        Esi: DeviceType:Fmmu:Sm
    */
    pub sm: u8,
    /// Esi: DeviceType:Fmmu:Su
    pub su: u8,
}
data::bilge_pdudata!(FmmuExtension, u24);

/// ETG.1000.6 table 24
#[bitsize(64)]
#[derive(TryFromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct SyncManager {
    /// Origin of Data (see Physical Start Address of SyncM)
    pub address: u16,
    pub length: u16,
    /// Defines Mode of Operation (see Control Register of SyncM)
    pub control: u8,
    /// don't care
    pub status: u8,
    pub enable: SyncManagerEnable,
    pub usage: SyncManagerUsage,
}
data::bilge_pdudata!(SyncManager, u64);

/// ETG.1000.6 table 24
#[bitsize(8)]
#[derive(FromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct SyncManagerEnable {
    pub enable: bool,
    /// fixed content (info for config tool –SyncMan has fixed content)
    pub fixed_content: bool,
    /// virtual SyncManager (virtual SyncMan – no hardware resource used)
    pub virtual_sync_manager: bool,
    /// opOnly (SyncMan should be enabled only in OP state)
    pub oponly: bool,
    _reserved: u4,
}

/// ETG.1000.6 table 24
#[bitsize(8)]
#[derive(TryFromBits, Debug, Copy, Clone, Eq, PartialEq)]
pub enum SyncManagerUsage {
    Disabled = 0x0,
    MailboxOut = 0x1,
    MailboxIn = 0x2,
    ProcessOut = 0x3,
    ProcessIn = 0x4,
}

#[repr(packed)]
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct DistributedClock {
    pub period: u32,
    pub shift0: u32,
    pub shift1: u32,
    pub sync1_period_factor: i16,
    pub assign_activate: u16,
    pub sync0_period_factor: i16,
    pub name: u8,
    pub description: u8,
    pub _reserved0: [u8;4],
}
data::packed_pdudata!(DistributedClock);

#[bitsize(8)]
#[derive(TryFromBits, DebugBits, Copy, Clone, Eq, PartialEq)]
pub struct SyncUnit {
    pub separate_su: bool,
    pub separate_frame: bool,
    pub depend_on_input_state: bool,
    pub frame_repeat_support: bool,
    reserved: u4,
}
data::bilge_pdudata!(SyncUnit, u8);

/**
    header for category describing a reading or writing PDO

    ETG.1000.6 table 25

    following data is [`[PdoEntry; _]`](PdoEntry)
*/
#[repr(packed)]
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Pdo {
    /// index of SDO configuring the PDO
    pub index: u16,
    /// number of entries in the PDO
    pub entries: u8,
    /// reference to DC-sync
    pub synchronization: u8,
    /// name of the PDO object (reference to category strings)
    pub name: u8,
    /// for future use
    pub flags: u16,
}
data::packed_pdudata!(Pdo);

/**
    structure describing an entry in a PDO

    ETG.1000.6 table 26
*/
#[repr(packed)]
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct PdoEntry {
    /// index of the SDO
    pub index: u16,
    /// index of field in the SDO (or 0 if complete SDO)
    pub sub: u8,
    /// name of this SDO
    pub name: u8,
    /// data type of the entry
    pub dtype: u8,
    /// data length of the entry
    pub bitlen: u8,
    /// for future use
    pub flags: u16,
}
data::packed_pdudata!(PdoEntry);