/* Copyright (C) 2024 DorotaC
 * SPDX-License-Identifier: LGPL-2.1-or-later OR MPL-2.0
 */

/*! A wrapper around Linux Media device interface. */

#[allow(non_camel_case_types)]
#[allow(non_snake_case)]
pub mod sys;

use bitflags::bitflags;
use const_enum::const_enum;
use std::ffi::CStr;
use std::fmt;
use std::mem;
use std::str;
use sys::{media_v2_entity, media_v2_link};


pub trait Zeroed where Self: Sized {
    fn zeroed() -> Self {
        unsafe { mem::zeroed() }
    }
}

// I already did the work with nicely documenting this struct, so let it be.
/// https://kernel.org/doc/html/v6.2/userspace-api/media/mediactl/media-ioc-device-info.html
#[repr(C)]
#[repr(packed)]
pub struct MediaDeviceInfo {
    /// ASCII
    driver_name: [u8; 16],
    /// UTF-8
    device_name: [u8; 32],
    /// ASCII
    serial_number: [u8; 40],
    /// ASCII
    bus_info: [u8; 32],
    media_version: u32,
    hardware_device_version: u32,
    driver_version: u32,
    reserved: [u32; 31],
}


impl Zeroed for MediaDeviceInfo {}

impl fmt::Debug for MediaDeviceInfo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("MediaDeviceInfo")
            .field("driver", &self.get_driver())
            .field("device", &self.get_device())
            .finish()
    }
}

fn str_from_slice(s: &[u8]) -> &str {
    let full = str::from_utf8(s).unwrap();
    let end_byte = full.char_indices()
        .find(|(_i, c)| *c == '\0')
        .map(|(i, _c)| i)
        .unwrap_or(full.len());
    full.split_at(end_byte).0
}

impl MediaDeviceInfo {
    pub fn get_driver(&self) -> &str {
        str_from_slice(&self.driver_name)
    }
    pub fn get_device(&self) -> &str {
        str_from_slice(&self.device_name)
    }
}

// https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/media.h#L371
nix::ioctl_readwrite!(media_ioc_device_info, b'|', 0x00, MediaDeviceInfo);


/// https://docs.kernel.org/userspace-api/media/mediactl/media-ioc-g-topology.html
#[repr(C)]
#[repr(packed)]
#[derive(Debug)]
pub struct media_v2_topology {
    topology_version: u64,
	pub num_entities: u32,
    reserved1: u32,
    ptr_entities: u64,

    pub num_interfaces: u32,
    reserved2: u32,
    ptr_interfaces: u64,

    num_pads: u32,
    reserved3: u32,
    ptr_pads: u64,

    pub num_links: u32,
    reserved4: u32,
    pub ptr_links: u64,
}

impl Zeroed for media_v2_topology {}

impl media_v2_topology {
    pub fn set_entities(&mut self, entities: &mut Vec<media_v2_entity>) {
        self.num_entities = entities.len() as u32;
        self.ptr_entities = entities.as_mut_ptr() as u64;
    }
    pub fn set_interfaces(&mut self, arr: &mut Vec<media_v2_interface>) {
        self.num_interfaces = arr.len() as u32;
        self.ptr_interfaces = arr.as_mut_ptr() as u64;
    }
}


const_enum! {
    enum MediaEntF, sys, MEDIA_ENT_F_ {
        UNKNOWN,
        V4L2_SUBDEV_UNKNOWN,
        DTV_DEMOD,
        TS_DEMUX,
        DTV_CA,
        DTV_NET_DECAP,
        /// Data streaming input and/or output entity.
        IO_V4L,
        IO_DTV,
        IO_VBI,
        IO_SWRADIO,
        /// Camera video sensor entity.
        CAM_SENSOR,
        FLASH,
        LENS,
        TUNER,
        IF_VID_DECODER,
        IF_AUD_DECODER,
        AUDIO_CAPTURE,
        AUDIO_PLAYBACK,
        AUDIO_MIXER,
        PROC_VIDEO_COMPOSER,
        /// Video pixel encoding converter. An entity capable of pixel encoding conversion must have at least one sink pad and one source pad, and convert the encoding of pixels received on its sink pad(s) to a different encoding output on its source pad(s). Pixel encoding conversion includes but isn’t limited to RGB to/from HSV, RGB to/from YUV and CFA (Bayer) to RGB conversions.
        PROC_VIDEO_PIXEL_FORMATTER,
        PROC_VIDEO_PIXEL_ENC_CONV,
        PROC_VIDEO_LUT,
        PROC_VIDEO_SCALER,
        PROC_VIDEO_STATISTICS,
        PROC_VIDEO_ENCODER,
        PROC_VIDEO_DECODER,
        PROC_VIDEO_ISP,
        VID_MUX,
        VID_IF_BRIDGE,
        ATV_DECODER,
        DV_DECODER,
        DV_ENCODER,
    }
}

bitflags! {
    #[derive(Debug)]
    pub struct MediaEntFl: u32 {
        const DEFAULT = sys::MEDIA_ENT_FL_DEFAULT;
        const CONNECTOR = sys::MEDIA_ENT_FL_CONNECTOR;
    }
}

#[derive(Debug)]
pub struct MediaV2Entity {
    /// Unique ID for the entity. Do not expect that the ID will always be the same for each instance of the device. In other words, do not hardcode entity IDs in an application.
    pub id: u32,
    /// This name must be unique within the media topology.
    /// (In practice, this is false with my integrated USB camera with 2 interfaces called "Integrated Camera: Integrated C\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0".
    /// If the name can be expressed as a valid String, it will be. Otherwise, the raw form is used.
    pub name: Result<String, [::std::os::raw::c_char; 64usize]>,
    /// Main function of the entity
    pub function: MediaEntF, 
    pub flags: MediaEntFl,
}

impl From<media_v2_entity> for MediaV2Entity {
    fn from(v: media_v2_entity) -> Self {
        let name: &[u8; 64] = unsafe { mem::transmute(&v.name) };
        let name = CStr::from_bytes_until_nul(name).ok()
            .and_then(|name| name.to_str().ok())
            .map(String::from)
            .ok_or_else(|| v.name.clone());
        Self {
            id: v.id,
            name,
            function: v.function.into(),
            flags: MediaEntFl::from_bits_retain(v.flags),
        }
    }
}

impl Zeroed for media_v2_entity {}

#[repr(C)]
#[repr(packed)]
union MediaV2Interface_devnode {
    devnode: MediaV2IntfDevnode,
    raw: [u32; 16],
}

#[repr(C)]
#[repr(packed)]
pub struct media_v2_interface {
    id: u32,
    intf_type: u32,
    flags: u32,
    reserved: [u32; 9],
    devnode: MediaV2Interface_devnode,
}

const_enum! {
    enum MediaIntfT, sys, MEDIA_INTF_T_ {
        DVB_FE,
        DVB_DEMUX,
        DVB_DVR,
        DVB_CA,
        DVB_NET,
        /// Device node interface for video (V4L)
        /// typically, /dev/video?
        V4L_VIDEO,
        V4L_VBI,
        V4L_RADIO,
        /// Device node interface for a V4L subdevice
        /// typically, /dev/v4l-subdev?
        V4L_SUBDEV,
        V4L_SWRADIO,
        V4L_TOUCH,
        ALSA_PCM_CAPTURE,
        ALSA_PCM_PLAYBACK,
        ALSA_CONTROL,
    }
}

#[derive(Debug)]
pub struct MediaV2Interface {
    /// Unique ID for the interface. Do not expect that the ID will always be the same for each instance of the device. In other words, do not hardcode interface IDs in an application.
    pub id: u32,
    pub intf_type: MediaIntfT,
    /// Currently unused.
    pub flags: u32,
    /// Used only for device node interfaces
    pub devnode: MediaV2IntfDevnode,
}

impl From<&media_v2_interface> for MediaV2Interface {
    fn from(v: &media_v2_interface) -> Self {
        MediaV2Interface {
            id: v.id,
            intf_type: v.intf_type.into(),
            flags: v.flags,
            devnode: unsafe { v.devnode.devnode },
        }
    }
}

impl Zeroed for media_v2_interface {}

#[repr(C)]
#[repr(packed)]
#[derive(Clone, Copy, Debug)]
pub struct MediaV2IntfDevnode {
    pub major: u32,
    pub minor: u32,
}

#[derive(Debug)]
pub struct MediaV2Link {
    id: u32,
    source_id: u32,
    sink_id: u32,
    flags: MediaLnkFl,
}

bitflags! {
    #[derive(Debug)]
    pub struct MediaLnkFl: u32 {
        /// The link is enabled and can be used to transfer media data. When two or more links target a sink pad, only one of them can be enabled at a time.
        const ENABLED = sys::MEDIA_LNK_FL_ENABLED;
        /// The link enabled state can’t be modified at runtime. An immutable link is always enabled.
        const IMMUTABLE = sys::MEDIA_LNK_FL_IMMUTABLE;
        /// The link enabled state can be modified during streaming. This flag is set by drivers and is read-only for applications.
        const DYNAMIC = sys::MEDIA_LNK_FL_DYNAMIC;
        /// This is a bitmask that defines the type of the link.
        const LINK_TYPE = sys::MEDIA_LNK_FL_LINK_TYPE;
        /// links that represent a data connection between two pads.
        const DATA_LINK = sys::MEDIA_LNK_FL_DATA_LINK;
        /// links that associate an entity to its interface.
        const INTERFACE_LINK = sys::MEDIA_LNK_FL_INTERFACE_LINK;
        /// links that represent a physical relationship between two entities. The link may or may not be immutable, so applications must not assume either case.
        const ANCILLARY_LINK = sys::MEDIA_LNK_FL_ANCILLARY_LINK;
    }
}

impl From<media_v2_link> for MediaV2Link {
    fn from(v: media_v2_link) ->Self {
        Self {
            id: v.id,
            source_id: v.source_id,
            sink_id: v.sink_id,
            flags: MediaLnkFl::from_bits_retain(v.flags),
        }
    }
}

impl Zeroed for media_v2_link {}

// https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/media.h#L375
nix::ioctl_readwrite!(media_ioc_g_topology, b'|', 0x04, media_v2_topology);


#[cfg(test)]
mod test {
    use super::*;
    #[test]
    fn entity_bad_string() {
        // fill entity with garbage
        let v = [0xfeu8; mem::size_of::<media_v2_entity>()];
        dbg!(v.len());
        let entity: media_v2_entity = unsafe { mem::transmute_copy(&v) };
        let entity = MediaV2Entity::from(entity);
        match entity.name {
            Err(_) => {},
            Ok(_) => panic!("bad string should not get accepted"),
        }
    }
}