use crate::error::{FaxError, Result};
use crate::fax::class2::commands::{Class2Commands, DccParams, BR_V17_14400};
use crate::fax::encoder::MhEncoder;
use crate::modem::driver::ModemDriver;
use crate::document::convert::Page;

const DLE: u8 = 0x10;
const ETX: u8 = 0x03;
const DLE_ETX: [u8; 2] = [DLE, ETX];

/// Class 2 Fax Sender - simpler than Class 1
/// The modem handles T.30 protocol, HDLC framing, and negotiation automatically.
pub struct Class2Send<'a> {
    driver: &'a mut ModemDriver,
    station_id: String,
    header: String,
    params: DccParams,
}

impl<'a> Class2Send<'a> {
    pub fn new(driver: &'a mut ModemDriver) -> Self {
        Self {
            driver,
            station_id: "TELFAX".to_string(),
            header: "Telfax Fax Server".to_string(),
            params: DccParams::default(),
        }
    }

    pub fn with_station_id(mut self, id: &str) -> Self {
        self.station_id = id.to_string();
        self
    }

    pub fn with_header(mut self, header: &str) -> Self {
        self.header = header.to_string();
        self
    }

    pub fn with_params(mut self, params: DccParams) -> Self {
        self.params = params;
        self
    }

    fn at(&mut self) -> crate::modem::at::AtChannel<'_> {
        crate::modem::at::AtChannel::new(self.driver)
    }

    /// Send fax document using Class 2 protocol
    /// Pages should be pre-encoded in T.4 MH format
    pub fn send_fax(&mut self, number: &str, pages: &[Page]) -> Result<()> {
        tracing::info!("Starting Class 2 fax to {}", number);

        // Initialize modem first
        let _ = self.at().send_command("ATZ", 3000);
        std::thread::sleep(std::time::Duration::from_millis(1000));
        self.at().send_command("AT", 5000)?;
        self.at().send_command("ATE0", 5000)?;

        // Hardware flow control
        let _ = self.at().send_command("AT+IFC=2,2", 5000);

        // Enter Class 2 mode
        self.at().send_command(Class2Commands::ENTER_CLASS2, 5000)?;
        tracing::info!("Entered Class 2 mode");

        // Enable capabilities report (efax does this — required by many Class 2 modems)
        let _ = self.at().send_command("AT+FCR=1", 3000);

        // Set station ID
        let station_cmd = Class2Commands::set_station_id(&self.station_id);
        self.at().send_command(&station_cmd, 3000)?;
        tracing::info!("Station ID set: {}", self.station_id);

        // Set header - may not be supported on some modems
        let header_cmd = Class2Commands::set_header(&self.header);
        if self.at().send_command(&header_cmd, 3000).is_err() {
            tracing::warn!("Header command not supported, skipping");
        }

        // Set DCE capabilities (NOT FDIS!) using +FDCC per efax's approach.
        // +FDCC tells the modem what it CAN do; +FDIS sets session params.
        // Let the modem use its defaults — only override if explicitly configured.
        // efax: "+FDCC=%d,%d,%d,%d,%d,%d,%d,%d"
        let speed = if self.params.speed > 0 { self.params.speed } else { BR_V17_14400 };
        let vr = if self.params.resolution { 1 } else { 0 };
        let ec = if self.params.ecm { 1 } else { 0 };
        let fdcc_cmd = format!("AT+FDCC={},{},0,2,0,{},0,0", vr, speed, ec);
        tracing::info!("Setting DCE capabilities: {}", fdcc_cmd);
        if self.at().send_command(&fdcc_cmd, 3000).is_err() {
            tracing::warn!("FDCC command not supported, trying FDIS...");
            // Fallback: some modems only support FDIS
            let fdis_cmd = Class2Commands::set_dis_params(self.params.resolution, speed, self.params.ecm);
            let _ = self.at().send_command(&fdis_cmd, 3000);
        }

        // Dial
        self.dial(number)?;

        // Send pages
        for (i, page) in pages.iter().enumerate() {
            tracing::info!("Sending page {} of {}", i + 1, pages.len());
            self.send_page(page)?;
            
            let is_last = i == pages.len() - 1;
            self.end_page(is_last)?;
        }

        // Hang up
        self.hang_up()?;
        tracing::info!("Fax sent successfully");

        Ok(())
    }

    fn dial(&mut self, number: &str) -> Result<()> {
        self.driver.drain()?;
        let cmd = Class2Commands::dial(number);
        self.driver.write_raw(cmd.as_bytes())?;
        self.driver.write_raw(b"\r")?;
        self.driver.flush()?;
        tracing::info!("Dialing: {}", cmd);

        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(60);

        // Read lines until CONNECT or error
        while std::time::Instant::now() < deadline {
            let line = match self.driver.read_until(b"\r\n", 5000) {
                Ok(l) => l,
                Err(crate::error::FaxError::Timeout { .. }) => continue,
                Err(e) => return Err(e),
            };
            let text = String::from_utf8_lossy(&line).trim().to_string();

            if text.is_empty() {
                continue;
            }

            tracing::info!("Dial response: {}", text);

            // Skip command echo
            if text.starts_with("ATDT") || text.starts_with("ATD") {
                continue;
            }

            // Error conditions
            if text.contains("NO CARRIER") || text.contains("BUSY") {
                return Err(FaxError::NoCarrier);
            }
            if text.contains("ERROR") {
                return Err(FaxError::modem("Dial command failed"));
            }
            if text.contains("+FHNG:") {
                return Err(FaxError::protocol(format!("Fax hangup: {}", text)));
            }

            // Connection established
            if text.contains("CONNECT") {
                tracing::info!("Connected!");
                // Read remaining session info (e.g. +FCON)
                let extra = self.driver.read_all(2000)?;
                let extra_text = String::from_utf8_lossy(&extra);
                if !extra_text.trim().is_empty() {
                    tracing::info!("Session info: {}", extra_text);
                    if extra_text.contains("+FHNG:") {
                        return Err(FaxError::protocol(format!("Fax hangup: {}", extra_text.trim())));
                    }
                }
                return Ok(());
            }

            // Some modems send +FCON without CONNECT
            if text.contains("+FCON") {
                tracing::info!("Fax conference established");
                return Ok(());
            }
        }

        Err(FaxError::Timeout { ms: 60000 })
    }

    fn send_page(&mut self, page: &Page) -> Result<()> {
        // Start page transmission
        // efax uses TO_C2B = 450 (45 seconds) for FDT timeout
        self.driver.write_raw(b"AT+FDT\r")?;
        self.driver.flush()?;

        // Wait for CONNECT with 45s timeout (per efax TO_C2B)
        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(45);
        let mut got_connect = false;
        while std::time::Instant::now() < deadline {
            let response = match self.driver.read_until(b"\r\n", 5000) {
                Ok(r) => r,
                Err(crate::error::FaxError::Timeout { .. }) => {
                    continue;
                }
                Err(e) => return Err(e),
            };
            let text = String::from_utf8_lossy(&response);
            tracing::info!("FDT response: {}", text.trim());

            if text.contains("CONNECT") {
                got_connect = true;
                break;
            }
            if text.contains("ERROR") {
                return Err(FaxError::modem("FDT command failed"));
            }
            if text.contains("+FCON") {
                tracing::info!("Got +FCON instead of CONNECT for FDT");
                got_connect = true;
                break;
            }
            if text.contains("+FHNG:") {
                return Err(FaxError::protocol(format!("Fax hangup before page: {}", text.trim())));
            }
        }
        
        if !got_connect {
            return Err(FaxError::Timeout { ms: 45000 });
        }

        // Wait for XON/DC2 to begin data transfer (efax getstartc())
        // Class 2 modems send XON (0x11) or DC2 (0x12) when ready for data
        tracing::info!("Waiting for XON/DC2...");
        let xon_deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
        let mut got_xon = false;
        while std::time::Instant::now() < xon_deadline {
            match self.driver.read_byte(500) {
                Ok(b) => {
                    if b == 0x11 || b == 0x12 { // XON or DC2
                        tracing::info!("Got XON/DC2 (0x{:02X})", b);
                        got_xon = true;
                        break;
                    }
                    tracing::debug!("Pre-XON byte: 0x{:02X}", b);
                }
                Err(crate::error::FaxError::Timeout { .. }) => continue,
                Err(e) => return Err(e),
            }
        }
        if !got_xon {
            tracing::warn!("No XON/DC2 received, proceeding anyway");
        }

        // Encode pixel data to T.4 MH format
        tracing::info!("Encoding {}x{} pixels to T.4 MH...", page.width_pels, page.rows);
        let mh_data = MhEncoder::encode_page(page)?;
        tracing::info!("Encoded to {} bytes", mh_data.len());

        // Escape any DLE (0x10) bytes in the data by doubling them
        let escaped_data = self.escape_dle(&mh_data);
        
        self.driver.write_raw(&escaped_data)?;
        self.driver.write_raw(&DLE_ETX)?;
        self.driver.flush()?;

        // Wait for page confirmation — can take >60s at 4800 bps for large pages
        let result = self.driver.read_until(b"\r\n", 180000)?;
        let result_text = String::from_utf8_lossy(&result);
        tracing::info!("Page result: {}", result_text);

        // Check for errors
        if result_text.contains("ERROR") {
            return Err(FaxError::protocol("Page transmission failed"));
        }

        Ok(())
    }

    fn end_page(&mut self, last_page: bool) -> Result<()> {
        let cmd = Class2Commands::end_page(!last_page);
        self.driver.write_raw(cmd.as_bytes())?;
        self.driver.write_raw(b"\r")?;
        self.driver.flush()?;

        // Wait for final OK — the modem may send multiple lines (+FPTS, OK)
        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(15);
        while std::time::Instant::now() < deadline {
            let response = match self.driver.read_until(b"\r\n", 5000) {
                Ok(r) => r,
                Err(crate::error::FaxError::Timeout { .. }) => continue,
                Err(e) => return Err(e),
            };
            let text = String::from_utf8_lossy(&response).trim().to_string();
            tracing::debug!("End page response: {}", text);
            if text == "OK" || text == "OK\r" {
                break;
            }
            if text.contains("ERROR") || text.contains("+FHNG:") {
                return Err(FaxError::protocol(format!("End page failed: {}", text)));
            }
        }
        
        // Allow modem time to prepare for next page
        std::thread::sleep(std::time::Duration::from_millis(1500));
        self.driver.drain()?;

        Ok(())
    }

    fn hang_up(&mut self) -> Result<()> {
        self.driver.write_raw(b"AT+FHNG=0\r")?;
        std::thread::sleep(std::time::Duration::from_millis(500));
        self.driver.drain()?;
        
        // Also send ATH to ensure hangup
        self.driver.write_raw(b"ATH\r")?;
        self.driver.drain()?;
        
        Ok(())
    }

    /// Escape DLE characters in fax data (Class 2 requires DLE doubling)
    fn escape_dle(&self, data: &[u8]) -> Vec<u8> {
        let mut escaped = Vec::with_capacity(data.len() * 2);
        for &byte in data {
            if byte == DLE {
                escaped.push(DLE);
                escaped.push(DLE); // Double DLE to escape it
            } else {
                escaped.push(byte);
            }
        }
        escaped
    }
}