use std::{
    fs,
    io::{ErrorKind, Read, Write},
    net::{TcpListener, TcpStream},
    path::PathBuf,
    sync::{
        atomic::{AtomicBool, Ordering},
        Arc,
    },
    thread::{self, JoinHandle},
    time::Duration,
};

#[cfg(target_os = "linux")]
use std::process::{Command, Stdio};

use anyhow::{anyhow, Context, Result};
use tauri::AppHandle;
use uuid::Uuid;

use crate::{
    model::{AppConfig, CaptureMode, JobSummary},
    state::SharedState,
    zpl::extract_barcodes,
};

#[cfg(target_os = "linux")]
const SYSTEM_CUPS_SPOOL_DIR: &str = "/var/spool/fieldlens-print";

pub struct CaptureRuntime {
    stop: Arc<AtomicBool>,
    handles: Vec<JoinHandle<()>>,
}

impl CaptureRuntime {
    pub fn stop(mut self) {
        self.stop.store(true, Ordering::SeqCst);
        for handle in self.handles.drain(..) {
            let _ = handle.join();
        }
    }
}

pub fn start(config: AppConfig, state: SharedState, app: AppHandle) -> Result<CaptureRuntime> {
    let stop = Arc::new(AtomicBool::new(false));
    let mut handles = Vec::new();

    if matches!(config.mode, CaptureMode::RawProxy | CaptureMode::Both) {
        let listener = TcpListener::bind(&config.listen_addr)
            .with_context(|| format!("bind RAW capture listener {}", config.listen_addr))?;
        listener.set_nonblocking(true)?;

        let worker_stop = stop.clone();
        let worker_state = state.clone();
        let worker_app = app.clone();
        let worker_config = config.clone();
        handles.push(thread::spawn(move || {
            raw_proxy_loop(listener, worker_config, worker_state, worker_app, worker_stop)
        }));
    }

    if matches!(config.mode, CaptureMode::SpoolFolder | CaptureMode::Both) {
        let spool_dir = PathBuf::from(&config.spool_dir);
        fs::create_dir_all(&spool_dir)
            .with_context(|| format!("create spool capture directory {}", spool_dir.display()))?;

        let worker_stop = stop.clone();
        let worker_state = state.clone();
        let worker_app = app.clone();
        let worker_config = config.clone();
        handles.push(thread::spawn(move || {
            spool_folder_loop(
                worker_config,
                worker_state,
                worker_app,
                worker_stop,
                None,
                "spool-folder",
                false,
            )
        }));
    }

    #[cfg(target_os = "linux")]
    {
        let system_spool = PathBuf::from(SYSTEM_CUPS_SPOOL_DIR);
        if system_spool.is_dir() && system_spool != PathBuf::from(&config.spool_dir) {
            let worker_stop = stop.clone();
            let worker_state = state.clone();
            let worker_app = app.clone();
            let worker_config = config.clone();
            handles.push(thread::spawn(move || {
                spool_folder_loop(
                    worker_config,
                    worker_state,
                    worker_app,
                    worker_stop,
                    Some(system_spool),
                    "cups-original",
                    true,
                )
            }));
        }
    }

    if handles.is_empty() {
        return Err(anyhow!("no capture route enabled"));
    }

    Ok(CaptureRuntime { stop, handles })
}

fn raw_proxy_loop(
    listener: TcpListener,
    config: AppConfig,
    state: SharedState,
    app: AppHandle,
    stop: Arc<AtomicBool>,
) {
    while !stop.load(Ordering::SeqCst) {
        match listener.accept() {
            Ok((stream, peer)) => {
                let state = state.clone();
                let app = app.clone();
                let config = config.clone();
                let label = peer.to_string();
                thread::spawn(move || handle_raw_connection(stream, &config, &state, &app, label));
            }
            Err(error) if error.kind() == ErrorKind::WouldBlock => {
                thread::sleep(Duration::from_millis(80));
            }
            Err(error) => {
                let job = JobSummary {
                    id: Uuid::new_v4().to_string(),
                    source: "raw-proxy".into(),
                    label: "listener".into(),
                    bytes: 0,
                    barcodes: vec![],
                    captured_at: chrono::Utc::now().to_rfc3339(),
                    forwarded: false,
                    error: Some(format!("accept failed: {error}")),
                };
                state.push_job(&app, job);
                thread::sleep(Duration::from_millis(500));
            }
        }
    }
}

fn handle_raw_connection(
    mut source: TcpStream,
    config: &AppConfig,
    state: &SharedState,
    app: &AppHandle,
    label: String,
) {
    let _ = source.set_read_timeout(Some(Duration::from_millis(750)));
    let mut forward_error: Option<String> = None;
    let mut destination = if config.forward_addr.trim().is_empty() {
        None
    } else {
        match config.forward_addr.parse() {
            Ok(addr) => match TcpStream::connect_timeout(&addr, Duration::from_secs(3)) {
                Ok(stream) => Some(stream),
                Err(error) => {
                    forward_error = Some(format!("forward connect failed: {error}"));
                    None
                }
            },
            Err(error) => {
                forward_error = Some(format!("invalid forward address: {error}"));
                None
            }
        }
    };

    let mut bytes = Vec::new();
    let mut buffer = [0u8; 16 * 1024];

    loop {
        match source.read(&mut buffer) {
            Ok(0) => break,
            Ok(read) => {
                let chunk = &buffer[..read];
                bytes.extend_from_slice(chunk);
                if let Some(target) = destination.as_mut() {
                    if let Err(error) = target.write_all(chunk) {
                        forward_error = Some(format!("forward write failed: {error}"));
                        destination = None;
                    }
                }
            }
            Err(error) if matches!(error.kind(), ErrorKind::WouldBlock | ErrorKind::TimedOut) => {
                if !bytes.is_empty() {
                    break;
                }
            }
            Err(error) => {
                forward_error = Some(format!("capture read failed: {error}"));
                break;
            }
        }
    }

    if bytes.is_empty() && forward_error.is_none() {
        return;
    }

    let tcp_requested = !config.forward_addr.trim().is_empty();
    let (forwarded, final_error) = if forward_error.is_some() {
        (false, forward_error)
    } else if tcp_requested {
        (true, None)
    } else if !config.forward_printer.trim().is_empty() {
        forward_to_system_printer(&config.forward_printer, &bytes)
    } else {
        (false, None)
    };

    process_payload(
        state,
        app,
        "raw-proxy",
        label,
        bytes,
        forwarded,
        final_error,
    );
}

fn spool_folder_loop(
    config: AppConfig,
    state: SharedState,
    app: AppHandle,
    stop: Arc<AtomicBool>,
    spool_override: Option<PathBuf>,
    source: &'static str,
    already_forwarded: bool,
) {
    let spool_dir = spool_override.unwrap_or_else(|| PathBuf::from(&config.spool_dir));
    let processed_dir = spool_dir.join("processed");
    let _ = fs::create_dir_all(&processed_dir);
    while !stop.load(Ordering::SeqCst) {
        let entries = match fs::read_dir(&spool_dir) {
            Ok(entries) => entries,
            Err(error) => {
                state.push_job(
                    &app,
                    JobSummary {
                        id: Uuid::new_v4().to_string(),
                        source: "spool-folder".into(),
                        label: spool_dir.display().to_string(),
                        bytes: 0,
                        barcodes: vec![],
                        captured_at: chrono::Utc::now().to_rfc3339(),
                        forwarded: false,
                        error: Some(format!("spool read failed: {error}")),
                    },
                );
                thread::sleep(Duration::from_secs(1));
                continue;
            }
        };

        for entry in entries.flatten() {
            let path = entry.path();
            if path.is_dir() || !is_supported_drop(&path) {
                continue;
            }

            let stable = entry
                .metadata()
                .ok()
                .and_then(|metadata| metadata.modified().ok())
                .and_then(|modified| modified.elapsed().ok())
                .map(|age| age >= Duration::from_millis(500))
                .unwrap_or(false);
            if !stable {
                continue;
            }

            let label = path
                .file_name()
                .and_then(|value| value.to_str())
                .unwrap_or("spool-job")
                .to_string();

            match fs::read(&path) {
                Ok(bytes) => {
                    let (forwarded, error) = if already_forwarded {
                        (true, None)
                    } else {
                        forward_payload(&config, &bytes)
                    };
                    process_payload(
                        &state,
                        &app,
                        source,
                        label.clone(),
                        bytes,
                        forwarded,
                        error,
                    );

                    let target = unique_processed_path(&processed_dir, &label);
                    let _ = fs::rename(&path, target);
                }
                Err(error) => process_payload(
                    &state,
                    &app,
                    source,
                    label,
                    vec![],
                    false,
                    Some(format!("spool file read failed: {error}")),
                ),
            }
        }

        thread::sleep(Duration::from_millis(350));
    }
}

fn is_supported_drop(path: &std::path::Path) -> bool {
    matches!(
        path.extension()
            .and_then(|value| value.to_str())
            .map(|value| value.to_ascii_lowercase())
            .as_deref(),
        Some("zpl" | "raw" | "prn" | "spl" | "pdf" | "ps" | "png" | "jpg" | "jpeg")
    )
}

fn unique_processed_path(dir: &std::path::Path, filename: &str) -> PathBuf {
    let safe = filename.replace('/', "_").replace('\\', "_");
    dir.join(format!(
        "{}-{}-{}",
        chrono::Utc::now().format("%Y%m%dT%H%M%S%.3fZ"),
        Uuid::new_v4(),
        safe
    ))
}

fn forward_payload(config: &AppConfig, bytes: &[u8]) -> (bool, Option<String>) {
    if !config.forward_addr.trim().is_empty() {
        return forward_all(&config.forward_addr, bytes);
    }
    if !config.forward_printer.trim().is_empty() {
        return forward_to_system_printer(&config.forward_printer, bytes);
    }
    (false, None)
}

fn forward_all(address: &str, bytes: &[u8]) -> (bool, Option<String>) {
    if address.trim().is_empty() {
        return (false, None);
    }

    let socket = match address.parse() {
        Ok(value) => value,
        Err(error) => return (false, Some(format!("invalid forward address: {error}"))),
    };

    match TcpStream::connect_timeout(&socket, Duration::from_secs(3)) {
        Ok(mut stream) => match stream.write_all(bytes) {
            Ok(()) => (true, None),
            Err(error) => (false, Some(format!("forward write failed: {error}"))),
        },
        Err(error) => (false, Some(format!("forward connect failed: {error}"))),
    }
}

#[cfg(target_os = "linux")]
fn forward_to_system_printer(printer: &str, bytes: &[u8]) -> (bool, Option<String>) {
    let mut child = match Command::new("lp")
        .args(["-d", printer, "-o", "raw", "-t", "FieldLens Print"])
        .stdin(Stdio::piped())
        .stdout(Stdio::null())
        .stderr(Stdio::piped())
        .spawn()
    {
        Ok(child) => child,
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {
            return (
                false,
                Some("CUPS client tools are missing; install cups-client".into()),
            )
        }
        Err(error) => {
            return (false, Some(format!("forward to CUPS printer failed: {error}")))
        }
    };

    if let Some(mut stdin) = child.stdin.take() {
        if let Err(error) = stdin.write_all(bytes) {
            let _ = child.kill();
            return (false, Some(format!("forward to CUPS printer failed: {error}")));
        }
    }

    match child.wait_with_output() {
        Ok(output) if output.status.success() => (true, None),
        Ok(output) => (
            false,
            Some(format!(
                "CUPS forward failed: {}",
                String::from_utf8_lossy(&output.stderr).trim()
            )),
        ),
        Err(error) => (false, Some(format!("CUPS forward failed: {error}"))),
    }
}

#[cfg(not(target_os = "linux"))]
fn forward_to_system_printer(printer: &str, _bytes: &[u8]) -> (bool, Option<String>) {
    (
        false,
        Some(format!(
            "installed-printer RAW forwarding is not available for '{printer}' without a network RAW/TCP address"
        )),
    )
}

fn process_payload(
    state: &SharedState,
    app: &AppHandle,
    source: &str,
    label: String,
    bytes: Vec<u8>,
    forwarded: bool,
    error: Option<String>,
) {
    let id = Uuid::new_v4().to_string();
    let (barcodes, parse_error) = match std::panic::catch_unwind(|| extract_barcodes(&bytes)) {
        Ok(found) => (found, None),
        Err(_) => (
            Vec::new(),
            Some("barcode parser failed; print bytes were still captured and forwarded".to_string()),
        ),
    };
    let error = error.or(parse_error);

    for barcode in &barcodes {
        state.queue_scan(
            barcode.value.clone(),
            barcode.format.clone(),
            "print".into(),
            &id,
            &label,
        );
    }

    state.push_job(
        app,
        JobSummary {
            id,
            source: source.into(),
            label,
            bytes: bytes.len(),
            barcodes,
            captured_at: chrono::Utc::now().to_rfc3339(),
            forwarded,
            error,
        },
    );
}