use std::ffi::{CString, OsStr};
use std::io::{self, Write};
use std::os::unix::prelude::OsStrExt;
use std::os::unix::process::CommandExt;
use std::path::PathBuf;
use std::process::{Command, Stdio};
use std::ptr::null_mut;
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;
use std::time::Duration;

use anyhow::{ensure, Context};
use directories::UserDirs;
use smithay::reexports::rustix::time::{clock_gettime, ClockId};
use smithay::utils::{Logical, Point, Rectangle};

use crate::config::Config;

pub fn get_monotonic_time() -> Duration {
    let ts = clock_gettime(ClockId::Monotonic);
    Duration::new(ts.tv_sec as u64, ts.tv_nsec as u32)
}

pub fn center(rect: Rectangle<i32, Logical>) -> Point<i32, Logical> {
    rect.loc + rect.size.downscale(2).to_point()
}

pub fn make_screenshot_path(config: &Config) -> anyhow::Result<Option<PathBuf>> {
    let Some(path) = &config.screenshot_path else {
        return Ok(None);
    };

    let format = CString::new(path.clone()).context("path must not contain nul bytes")?;

    let mut buf = [0u8; 2048];
    let mut path;
    unsafe {
        let time = libc::time(null_mut());
        ensure!(time != -1, "error in time()");

        let tm = libc::localtime(&time);
        ensure!(!tm.is_null(), "error in localtime()");

        let rv = libc::strftime(buf.as_mut_ptr().cast(), buf.len(), format.as_ptr(), tm);
        ensure!(rv != 0, "error formatting time");

        path = PathBuf::from(OsStr::from_bytes(&buf[..rv]));
    }

    if let Ok(rest) = path.strip_prefix("~") {
        let dirs = UserDirs::new().context("error retrieving home directory")?;
        path = [dirs.home_dir(), rest].iter().collect();
    }

    Ok(Some(path))
}

pub static REMOVE_ENV_RUST_BACKTRACE: AtomicBool = AtomicBool::new(false);
pub static REMOVE_ENV_RUST_LIB_BACKTRACE: AtomicBool = AtomicBool::new(false);

/// Spawns the command to run independently of the compositor.
pub fn spawn<T: AsRef<OsStr> + Send + 'static>(command: Vec<T>) {
    let _span = tracy_client::span!();

    if command.is_empty() {
        return;
    }

    // Spawning and waiting takes some milliseconds, so do it in a thread.
    let res = thread::Builder::new()
        .name("Command Spawner".to_owned())
        .spawn(move || {
            let (command, args) = command.split_first().unwrap();
            spawn_sync(command, args);
        });

    if let Err(err) = res {
        warn!("error spawning a thread to spawn the command: {err:?}");
    }
}

fn spawn_sync(command: impl AsRef<OsStr>, args: impl IntoIterator<Item = impl AsRef<OsStr>>) {
    let _span = tracy_client::span!();

    let command = command.as_ref();

    let mut process = Command::new(command);
    process
        .args(args)
        .stdin(Stdio::null())
        .stdout(Stdio::null())
        .stderr(Stdio::null());

    // Remove RUST_BACKTRACE and RUST_LIB_BACKTRACE from the environment if needed.
    if REMOVE_ENV_RUST_BACKTRACE.load(Ordering::Relaxed) {
        process.env_remove("RUST_BACKTRACE");
    }
    if REMOVE_ENV_RUST_LIB_BACKTRACE.load(Ordering::Relaxed) {
        process.env_remove("RUST_LIB_BACKTRACE");
    }

    // Double-fork to avoid having to waitpid the child.
    unsafe {
        process.pre_exec(|| {
            match libc::fork() {
                -1 => return Err(io::Error::last_os_error()),
                0 => (),
                _ => libc::_exit(0),
            }

            Ok(())
        });
    }

    let mut child = match process.spawn() {
        Ok(child) => child,
        Err(err) => {
            warn!("error spawning {command:?}: {err:?}");
            return;
        }
    };

    match child.wait() {
        Ok(status) => {
            if !status.success() {
                warn!("child did not exit successfully: {status:?}");
            }
        }
        Err(err) => {
            warn!("error waiting for child: {err:?}");
        }
    }
}

pub fn write_png_rgba8(
    w: impl Write,
    width: u32,
    height: u32,
    pixels: &[u8],
) -> Result<(), png::EncodingError> {
    let mut encoder = png::Encoder::new(w, width, height);
    encoder.set_color(png::ColorType::Rgba);
    encoder.set_depth(png::BitDepth::Eight);

    let mut writer = encoder.write_header()?;
    writer.write_image_data(pixels)
}

#[cfg(feature = "dbus")]
pub fn show_screenshot_notification(image_path: Option<PathBuf>) {
    let mut notification = notify_rust::Notification::new();
    notification
        .summary("Screenshot captured")
        .body("You can paste the image from the clipboard.")
        .urgency(notify_rust::Urgency::Normal)
        .hint(notify_rust::Hint::Transient(true));

    // Try to add the screenshot as an image if possible.
    if let Some(path) = image_path {
        match path.canonicalize() {
            Ok(path) => match url::Url::from_file_path(path) {
                Ok(url) => {
                    notification.image_path(url.as_str());
                }
                Err(err) => {
                    warn!("error converting screenshot path to file url: {err:?}");
                }
            },
            Err(err) => {
                warn!("error canonicalizing screenshot path: {err:?}");
            }
        }
    }

    if let Err(err) = notification.show() {
        warn!("error showing screenshot notification: {err:?}");
    }
}