use std::ffi::{CStr, CString};
use std::fmt;
use std::fs;
use std::io::Write;
use std::mem;
use std::ptr;
use std::slice;

use log::*;

use libv4l_sys as v4l;

macro_rules! errno {
    () => {
        unsafe { *libc::__errno_location() }
    };
}

#[derive(Debug, Clone)]
struct Framesize {
    pub width: u32,
    pub height: u32,
}

impl fmt::Display for Framesize {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}x{}", self.width, self.height)
    }
}

#[derive(Debug)]
struct Buffer {
    start: *mut libc::c_void,
    length: libc::size_t,
}

fn strerror() -> String {
    let errno = errno!();
    unsafe { CStr::from_ptr(libc::strerror(errno)) }
        .to_string_lossy()
        .into()
}

fn rioctl(fd: libc::c_int, request: libc::c_ulong, arg: *mut libc::c_void) -> libc::c_int {
    let mut r;

    loop {
        r = unsafe { v4l::v4l2_ioctl(fd, request, arg) };
        if r == -1 && ((errno!() == libc::EINTR) || (errno!() == libc::EAGAIN)) {
            continue;
        } else {
            break;
        }
    }
    r
}

fn xioctl(fd: libc::c_int, request: libc::c_ulong, arg: *mut libc::c_void) {
    if rioctl(fd, request, arg) == -1 {
        error!("error {}, {}", errno!(), strerror());
        panic!()
    }
}

fn main() {
    println!("v4l2grab");
    env_logger::init();

    let dev_name = CString::new("/dev/video0").unwrap();

    let fd = unsafe {
        let fd = v4l::v4l2_open(dev_name.as_ptr(), libc::O_RDWR | libc::O_NONBLOCK, 0);
        if fd == -1 {
            error!("open device error: {}: {}", fd, strerror());
            panic!()
        }
        fd
    };

    let fmt = unsafe {
        let mut fmt: v4l::v4l2_format = mem::zeroed();
        fmt.type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
        fmt.fmt.pix.width = 320;
        fmt.fmt.pix.height = 240;
        fmt.fmt.pix.pixelformat = v4l::pixel_format::V4L2_PIX_FMT_RGB24;
        fmt.fmt.pix.field = v4l::v4l2_field_V4L2_FIELD_INTERLACED;

        xioctl(
            fd,
            v4l::codes::VIDIOC_S_FMT,
            &mut fmt as *mut _ as *mut libc::c_void,
        );
        if fmt.fmt.pix.pixelformat != v4l::pixel_format::V4L2_PIX_FMT_RGB24 {
            println!("Libv4l didn't accept RGB24 format. Can't proceed.");
            panic!()
        }
        if (fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480) {
            println!(
                "Warning: driver is sending image at {}x{}",
                fmt.fmt.pix.width, fmt.fmt.pix.height
            );
        }
        fmt
    };

    let mut req = unsafe {
        let mut req: v4l::v4l2_requestbuffers = mem::zeroed();
        req.count = 2;
        req.type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
        req.memory = v4l::v4l2_memory_V4L2_MEMORY_MMAP;
        req
    };

    xioctl(
        fd,
        v4l::codes::VIDIOC_REQBUFS,
        &mut req as *mut _ as *mut libc::c_void,
    );

    let mut buffers = Vec::new();
    for n_buffers in 0..req.count {
        let mut buf = unsafe {
            let mut buf: v4l::v4l2_buffer = mem::zeroed();
            buf.type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = v4l::v4l2_memory_V4L2_MEMORY_MMAP;
            buf.index = n_buffers;
            buf
        };

        xioctl(
            fd,
            v4l::codes::VIDIOC_QUERYBUF,
            &mut buf as *mut _ as *mut libc::c_void,
        );
        let buffer = unsafe {
            Buffer {
                start: v4l::v4l2_mmap(
                    ptr::null_mut(),
                    buf.length.try_into().unwrap(),
                    libc::PROT_READ | libc::PROT_WRITE,
                    libc::MAP_SHARED,
                    fd,
                    buf.m.offset as i64,
                ),
                length: buf.length as libc::size_t,
            }
        };

        if libc::MAP_FAILED == buffer.start {
            error!("mmap");
            panic!()
        }
        buffers.push(buffer);
    }

    for i in 0..buffers.len() {
        let mut buf = unsafe {
            let mut buf: v4l::v4l2_buffer = mem::zeroed();
            buf.type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = v4l::v4l2_memory_V4L2_MEMORY_MMAP;
            buf.index = i as u32;
            buf
        };

        xioctl(
            fd,
            v4l::codes::VIDIOC_QBUF,
            &mut buf as *mut _ as *mut libc::c_void,
        );
    }

    let mut type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
    xioctl(
        fd,
        v4l::codes::VIDIOC_STREAMON,
        &mut type_ as *mut _ as *mut libc::c_void,
    );

    for i in 0..20 {
        debug!("0..20: {}", i);

        unsafe {
            let mut fds: libc::fd_set = mem::zeroed();
            loop {
                libc::FD_ZERO(&mut fds);
                libc::FD_SET(fd, &mut fds);
                let mut tv = libc::timeval {
                    tv_sec: 2,
                    tv_usec: 0,
                };
                let r = libc::select(fd + 1, &mut fds, ptr::null_mut(), ptr::null_mut(), &mut tv);
                if !(r == -1 && (errno!() == libc::EINTR)) {
                    if cfg!(target_os = "linux") {
                        debug!("time left: {}.{:06}", tv.tv_sec, tv.tv_usec);
                    }
                    break;
                }
                if r == -1 {
                    error!("select error {}, {}", errno!(), strerror());
                    panic!()
                }
            }
        }

        let mut buf = unsafe {
            let mut buf: v4l::v4l2_buffer = mem::zeroed();
            buf.type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = v4l::v4l2_memory_V4L2_MEMORY_MMAP;
            buf
        };

        debug!("VIDIOC_DQBUF");
        xioctl(
            fd,
            v4l::codes::VIDIOC_DQBUF,
            &mut buf as *mut _ as *mut libc::c_void,
        );

        {
            let mut fout = fs::File::create(&format!("out{:03}.ppm", i)).unwrap();
            write!(
                fout,
                "P6\n{} {} 255\n",
                unsafe { fmt.fmt.pix.width },
                unsafe { fmt.fmt.pix.height }
            )
            .unwrap();

            unsafe {
                fout.write_all(slice::from_raw_parts(
                    buffers[buf.index as usize].start as *const u8,
                    buf.bytesused as usize,
                ))
                .unwrap();
            }
        }

        debug!("VIDIOC_QBUF");
        xioctl(
            fd,
            v4l::codes::VIDIOC_QBUF,
            &mut buf as *mut _ as *mut libc::c_void,
        );
    }

    let mut type_ = v4l::v4l2_buf_type_V4L2_BUF_TYPE_VIDEO_CAPTURE;
    debug!("VIDIOC_STREAMOFF");
    xioctl(
        fd,
        v4l::codes::VIDIOC_STREAMOFF,
        &mut type_ as *mut _ as *mut libc::c_void,
    );

    unsafe {
        for buf in buffers {
            v4l::v4l2_munmap(buf.start, buf.length);
        }
        v4l::v4l2_close(fd);
    }
}