//! Helper utility to configure a specific modem context.
use core::net::IpAddr;
use core::str::FromStr;

use at_commands::builder::CommandBuilder;
use at_commands::parser::CommandParser;
use embassy_time::{Duration, Timer};
use heapless::Vec;

/// Provides a higher level API for controlling a given context.
pub struct Control<'a> {
    control: crate::Control<'a>,
    cid: u8,
}

/// Configuration for a given context
pub struct Config<'a> {
    /// Desired APN address.
    pub apn: &'a [u8],
    /// Desired authentication protocol.
    pub auth_prot: AuthProt,
    /// Credentials.
    pub auth: Option<(&'a [u8], &'a [u8])>,
    /// SIM pin
    pub pin: Option<&'a [u8]>,
}

/// Authentication protocol.
#[derive(Clone, Copy, PartialEq, Debug)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
#[repr(u8)]
pub enum AuthProt {
    /// No authentication.
    None = 0,
    /// PAP authentication.
    Pap = 1,
    /// CHAP authentication.
    Chap = 2,
}

/// Error returned by control.
#[derive(Clone, Copy, PartialEq, Debug)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub enum Error {
    /// Not enough space for command.
    BufferTooSmall,
    /// Error parsing response from modem.
    AtParseError,
    /// Error parsing IP addresses.
    AddrParseError,
}

impl From<at_commands::parser::ParseError> for Error {
    fn from(_: at_commands::parser::ParseError) -> Self {
        Self::AtParseError
    }
}

/// Status of a given context.
#[derive(PartialEq, Debug)]
pub struct Status {
    /// Attached to APN or not.
    pub attached: bool,
    /// IP if assigned.
    pub ip: Option<IpAddr>,
    /// Gateway if assigned.
    pub gateway: Option<IpAddr>,
    /// DNS servers if assigned.
    pub dns: Vec<IpAddr, 2>,
}

#[cfg(feature = "defmt")]
impl defmt::Format for Status {
    fn format(&self, f: defmt::Formatter<'_>) {
        defmt::write!(f, "attached: {}", self.attached);
        if let Some(ip) = &self.ip {
            defmt::write!(f, ", ip: {}", defmt::Debug2Format(&ip));
        }
    }
}

impl<'a> Control<'a> {
    /// Create a new instance of a control handle for a given context.
    ///
    /// Will wait for the modem to be initialized if not.
    pub async fn new(control: crate::Control<'a>, cid: u8) -> Self {
        control.wait_init().await;
        Self { control, cid }
    }

    /// Perform a raw AT command
    pub async fn at_command(&self, req: &[u8], resp: &mut [u8]) -> usize {
        self.control.at_command(req, resp).await
    }

    /// Configures the modem with the provided config.
    ///
    /// NOTE: This will disconnect the modem from any current APN and should not
    /// be called if the configuration has not been changed.
    ///
    /// After configuring, invoke [`enable()`] to activate the configuration.
    pub async fn configure(&self, config: &Config<'_>) -> Result<(), Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CFUN")
            .with_int_parameter(0)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGDCONT")
            .with_int_parameter(self.cid)
            .with_string_parameter("IP")
            .with_string_parameter(config.apn)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        // info!("RES1: {}", unsafe { core::str::from_utf8_unchecked(&buf[..n]) });
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;

        let mut op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGAUTH")
            .with_int_parameter(self.cid)
            .with_int_parameter(config.auth_prot as u8);
        if let Some((username, password)) = config.auth {
            op = op.with_string_parameter(username).with_string_parameter(password);
        }
        let op = op.finish().map_err(|_| Error::BufferTooSmall)?;

        let n = self.control.at_command(op, &mut buf).await;
        // info!("RES2: {}", unsafe { core::str::from_utf8_unchecked(&buf[..n]) });
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;

        if let Some(pin) = config.pin {
            let op = CommandBuilder::create_set(&mut cmd, true)
                .named("+CPIN")
                .with_string_parameter(pin)
                .finish()
                .map_err(|_| Error::BufferTooSmall)?;
            let _ = self.control.at_command(op, &mut buf).await;
            // Ignore ERROR which means no pin required
        }

        Ok(())
    }

    /// Attach to the PDN
    pub async fn attach(&self) -> Result<(), Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];
        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGATT")
            .with_int_parameter(1)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
        Ok(())
    }

    /// Read current connectivity status for modem.
    pub async fn detach(&self) -> Result<(), Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];
        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGATT")
            .with_int_parameter(0)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
        Ok(())
    }

    async fn attached(&self) -> Result<bool, Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];

        let op = CommandBuilder::create_query(&mut cmd, true)
            .named("+CGATT")
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        let (res,) = CommandParser::parse(&buf[..n])
            .expect_identifier(b"+CGATT: ")
            .expect_int_parameter()
            .expect_identifier(b"\r\nOK")
            .finish()?;
        Ok(res == 1)
    }

    /// Read current connectivity status for modem.
    pub async fn status(&self) -> Result<Status, Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];

        let op = CommandBuilder::create_query(&mut cmd, true)
            .named("+CGATT")
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        let (res,) = CommandParser::parse(&buf[..n])
            .expect_identifier(b"+CGATT: ")
            .expect_int_parameter()
            .expect_identifier(b"\r\nOK")
            .finish()?;
        let attached = res == 1;
        if !attached {
            return Ok(Status {
                attached,
                ip: None,
                gateway: None,
                dns: Vec::new(),
            });
        }

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGPADDR")
            .with_int_parameter(self.cid)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        let (_, ip1, _ip2) = CommandParser::parse(&buf[..n])
            .expect_identifier(b"+CGPADDR: ")
            .expect_int_parameter()
            .expect_optional_string_parameter()
            .expect_optional_string_parameter()
            .expect_identifier(b"\r\nOK")
            .finish()?;

        let ip = if let Some(ip) = ip1 {
            let ip = IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?;
            Some(ip)
        } else {
            None
        };

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CGCONTRDP")
            .with_int_parameter(self.cid)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        let (_cid, _bid, _apn, _mask, gateway, dns1, dns2, _, _, _, _, _mtu) = CommandParser::parse(&buf[..n])
            .expect_identifier(b"+CGCONTRDP: ")
            .expect_int_parameter()
            .expect_optional_int_parameter()
            .expect_optional_string_parameter()
            .expect_optional_string_parameter()
            .expect_optional_string_parameter()
            .expect_optional_string_parameter()
            .expect_optional_string_parameter()
            .expect_optional_int_parameter()
            .expect_optional_int_parameter()
            .expect_optional_int_parameter()
            .expect_optional_int_parameter()
            .expect_optional_int_parameter()
            .expect_identifier(b"\r\nOK")
            .finish()?;

        let gateway = if let Some(ip) = gateway {
            if ip.is_empty() {
                None
            } else {
                Some(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?)
            }
        } else {
            None
        };

        let mut dns = Vec::new();
        if let Some(ip) = dns1 {
            dns.push(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?)
                .unwrap();
        }

        if let Some(ip) = dns2 {
            dns.push(IpAddr::from_str(ip).map_err(|_| Error::AddrParseError)?)
                .unwrap();
        }

        Ok(Status {
            attached,
            ip,
            gateway,
            dns,
        })
    }

    async fn wait_attached(&self) -> Result<Status, Error> {
        while !self.attached().await? {
            Timer::after(Duration::from_secs(1)).await;
        }
        let status = self.status().await?;
        Ok(status)
    }

    /// Disable modem
    pub async fn disable(&self) -> Result<(), Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CFUN")
            .with_int_parameter(0)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;

        Ok(())
    }

    /// Enable modem
    pub async fn enable(&self) -> Result<(), Error> {
        let mut cmd: [u8; 256] = [0; 256];
        let mut buf: [u8; 256] = [0; 256];

        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("+CFUN")
            .with_int_parameter(1)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;

        // Make modem survive PDN detaches
        let op = CommandBuilder::create_set(&mut cmd, true)
            .named("%XPDNCFG")
            .with_int_parameter(1)
            .finish()
            .map_err(|_| Error::BufferTooSmall)?;
        let n = self.control.at_command(op, &mut buf).await;
        CommandParser::parse(&buf[..n]).expect_identifier(b"OK").finish()?;
        Ok(())
    }

    /// Run a control loop for this context, ensuring that reaattach is handled.
    pub async fn run<F: Fn(&Status)>(&self, reattach: F) -> Result<(), Error> {
        self.enable().await?;
        let status = self.wait_attached().await?;
        let mut fd = self.control.open_raw_socket().await;
        reattach(&status);

        loop {
            if !self.attached().await? {
                trace!("detached");

                self.control.close_raw_socket(fd).await;
                let status = self.wait_attached().await?;
                trace!("attached");
                fd = self.control.open_raw_socket().await;
                reattach(&status);
            }
            Timer::after(Duration::from_secs(10)).await;
        }
    }
}