/// Utilities to write SDP offers and answers using Janus's SDP parsing machinery.

use glib_sys;
use libc;
use janus_plugin_sys as ffi;
use serde::de::{self, Deserialize, Deserializer, Unexpected, Visitor};
use serde::ser::{Serialize, Serializer};
pub use ffi::sdp::janus_sdp_generate_answer as generate_answer;
pub use ffi::sdp::janus_sdp_generate_offer as generate_offer;
use std::collections::HashMap;
use std::error::Error;
use std::fmt;
use std::ffi::{CStr, CString};
use std::ops::Deref;
use std::str;
use crate::utils::GLibString;

pub type RawSdp = ffi::sdp::janus_sdp;
pub type RawMLine = ffi::sdp::janus_sdp_mline;
pub type RawAttribute = ffi::sdp::janus_sdp_attribute;
pub use ffi::sdp::janus_sdp_mtype as MediaType;
pub use ffi::sdp::janus_sdp_mdirection as MediaDirection;

// courtesy of c_string crate, which also has some other stuff we aren't interested in
// taking in as a dependency here.
macro_rules! c_str {
    ($lit:expr) => {
        unsafe {
            ::std::ffi::CStr::from_ptr(concat!($lit, "\0").as_ptr() as *const ::std::os::raw::c_char)
        }
    }
}

/// SDP attributes which may refer to a specific RTP payload type.
static MEDIA_PAYLOAD_ATTRIBUTES: [&str; 3] = ["rtpmap", "fmtp", "rtcp-fb"];

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
/// Available Janus audio codecs. See utils.c.
pub enum AudioCodec {
    Opus,
    Pcmu,
    Pcma,
    G722,
    Isac16,
    Isac32,
}

impl AudioCodec {
    pub fn to_str(self) -> &'static str {
        self.to_cstr().to_str().unwrap()
    }
    pub fn to_cstr(self) -> &'static CStr {
        match self {
            AudioCodec::Opus => c_str!("opus"),
            AudioCodec::Pcmu => c_str!("pcmu"),
            AudioCodec::Pcma => c_str!("pcma"),
            AudioCodec::G722 => c_str!("g722"),
            AudioCodec::Isac16 => c_str!("isac16"),
            AudioCodec::Isac32 => c_str!("isac32"),
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
/// Available Janus video codecs. See utils.c.
pub enum VideoCodec {
    Vp8,
    Vp9,
    H264,
}

impl VideoCodec {
    pub fn to_str(self) -> &'static str {
        self.to_cstr().to_str().unwrap()
    }
    pub fn to_cstr(self) -> &'static CStr {
        match self {
            VideoCodec::Vp8 => c_str!("vp8"),
            VideoCodec::Vp9 => c_str!("vp9"),
            VideoCodec::H264 => c_str!("h264"),
        }
    }
}

#[repr(i32)]
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
/// Parameters controlling SDP offer answering behavior. Used as keys in the parameter list
/// for `janus_sdp_generate_answer`. See sdp-utils.h in the Janus source for more details.
pub enum OfferAnswerParameters {
    /// Used to signal the end of the offer-answer parameter list.
    Done = 0,
    /// Whether to accept or reject audio.
    Audio = 1,
    /// Whether to accept or reject video.
    Video = 2,
    /// Whether to accept or reject data.
    Data = 3,
    /// The MediaDirection for the audio stream.
    AudioDirection = 4,
    /// The MediaDirection for the video stream.
    VideoDirection = 5,
    /// The AudioCodec for the audio stream.
    AudioCodec = 6,
    /// The VideoCodec for the video stream.
    VideoCodec = 7,
    /// The payload type for the audio stream.
    AudioPayloadType = 8,
    /// The payload type for the video stream.
    VideoPayloadType = 9,
    /// Whether to negotiate telephone events.
    AudioDtmf = 10,
    /// Whether to add RTCP-FB attributes.
    VideoRtcpfbDefaults = 11,
    /// Whether to add attributes for H.264 video.
    VideoH264Fmtp = 12,
}

/// An SDP session description.
pub struct Sdp {
    pub ptr: *mut RawSdp, // annoyingly pub because of answer_sdp macro
}

/// An error indicating that we failed to parse an SDP for some reason.
#[derive(Debug, Clone)]
pub struct SdpParseError {
    buffer: Vec<u8>
}

impl Error for SdpParseError {
    fn description(&self) -> &str {
        str::from_utf8(&self.buffer).unwrap_or("SDP parsing failed, but the error was not valid UTF-8 :(")
    }
}

impl fmt::Display for SdpParseError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(self.description())
    }
}

impl Sdp {
    pub unsafe fn new(ptr: *mut RawSdp) -> Option<Self> {
        ptr.as_mut().map(|p| Self { ptr: p })
    }

    /// Parses an SDP offer string from a client into a structured SDP object.
    pub fn parse(offer: &CStr) -> Result<Self, SdpParseError> {
        let mut error_buffer = Vec::with_capacity(512);
        let error_ptr = error_buffer.as_mut_ptr() as *mut _;
        unsafe {
            let result = ffi::sdp::janus_sdp_parse(offer.as_ptr(), error_ptr, error_buffer.capacity());
            Sdp::new(result).ok_or_else(|| {
                error_buffer.set_len(libc::strlen(error_ptr));
                SdpParseError { buffer: error_buffer }
            })
        }
    }

    /// Gets the payload type number for a codec in this SDP, or None if the codec isn't present.
    pub fn get_payload_type(&self, codec_name: &CStr) -> Option<i32> {
        unsafe {
            match ffi::sdp::janus_sdp_get_codec_pt(self.ptr, codec_name.as_ptr()) {
                err if err < 0 => None,
                n => Some(n),
            }
        }
    }

    /// Adds an attribute for the m-line with the given payload type.
    pub fn add_attribute(&mut self, pt: i32, name: &CStr, contents: &CStr) {
        for (_media, m_lines) in self.get_mlines() {
            unsafe {
                for m_line in m_lines {
                    if !glib_sys::g_list_find(m_line.ptypes, pt as *const _).is_null() {
                        let attr = ffi::sdp::janus_sdp_attribute_create(name.as_ptr(), contents.as_ptr());
                        ffi::sdp::janus_sdp_attribute_add_to_mline(m_line as *mut _, attr as *mut _);
                    }
                }
            }
        }
    }

    /// Rewrites any references from one dynamically assigned payload type in this SDP to another dynamically assigned
    /// payload type.
    pub fn rewrite_payload_type(&mut self, from: i32, to: i32) {
        let from_pt_string = from.to_string();
        let to_pt_string = to.to_string();
        for (_media, m_lines) in self.get_mlines() {
            unsafe {
                for m_line in m_lines {
                    // 1. replace the payload type ID in this media line's payload type list
                    if !glib_sys::g_list_find(m_line.ptypes, from as *const _).is_null() {
                        // payload type data in the list is cast to pointers
                        m_line.ptypes = glib_sys::g_list_remove(m_line.ptypes, from as *const _);
                        m_line.ptypes = glib_sys::g_list_prepend(m_line.ptypes, to as *mut _);
                    }
                    // 2. rewrite the values of attribute lines with the old payload type to have the new payload type
                    let mut attr_node = m_line.attributes;
                    while let Some(node) = attr_node.as_ref() {
                        let next = node.next; // we might delete this link, so grab next now!
                        let data = node.data as *mut RawAttribute;
                        let attr = data.as_ref().expect("Null data in SDP attribute node :(");
                        let name = CStr::from_ptr(attr.name).to_str().expect("Invalid attribute name in SDP :(");
                        if MEDIA_PAYLOAD_ATTRIBUTES.contains(&name) {
                            // each of the attributes with payload types in the values look like "$pt $stuff"
                            // where $stuff is specifying payload-type-specfic options; just rewrite $pt
                            let value = CStr::from_ptr(attr.value).to_str().expect("Invalid attribute value in SDP :(");
                            if value.starts_with(&from_pt_string) {
                                // value string is copied into the attribute
                                let new_val = CString::new(value.replacen(&from_pt_string, &to_pt_string, 1)).unwrap();
                                let new_attr = ffi::sdp::janus_sdp_attribute_create(attr.name, new_val.as_ptr());
                                m_line.attributes = glib_sys::g_list_prepend(m_line.attributes, new_attr as *mut _);
                                m_line.attributes = glib_sys::g_list_delete_link(m_line.attributes, attr_node);
                                ffi::sdp::janus_sdp_attribute_destroy(data);
                            }
                        }
                        attr_node = next;
                    }
                }
            }
        }
    }

    /// Returns a map of all the SDP media lines per SDP media type.
    pub fn get_mlines(&self) -> HashMap<MediaType, Vec<&mut RawMLine>> {
        let mut result = HashMap::new();
        unsafe {
            let mut ml_node = (*self.ptr).m_lines;
            while let Some(node) = ml_node.as_ref() {
                let ml = (node.data as *mut RawMLine).as_mut().expect("Null data in SDP media node :(");
                result.entry(ml.type_).or_insert_with(Vec::new).push(ml);
                ml_node = node.next;
            }
            result
        }
    }

    /// Writes this SDP into an owned C-style string.
    pub fn to_glibstring(&self) -> GLibString {
        unsafe {
            let sdp = ffi::sdp::janus_sdp_write(self.ptr);
            GLibString::from_chars(sdp).expect("Mysterious error writing SDP to string :(")
        }
    }
}

impl Deref for Sdp {
    type Target = RawSdp;

    fn deref(&self) -> &RawSdp {
        unsafe { &*self.ptr }
    }
}

impl Drop for Sdp {
    fn drop(&mut self) {
        unsafe {
            ffi::sdp::janus_sdp_destroy(self.ptr);
        }
    }
}

impl fmt::Debug for Sdp {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Sdp {{ {} }}", self.to_glibstring().to_string_lossy())
    }
}

impl Serialize for Sdp {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer {
        self.to_glibstring().serialize(serializer)
    }
}

impl<'de> Deserialize<'de> for Sdp {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer<'de> {
        struct SdpVisitor;
        impl<'de> Visitor<'de> for SdpVisitor {
            type Value = Sdp;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("an SDP string")
            }

            fn visit_str<E>(self, value: &str) -> Result<Sdp, E> where E: de::Error {
                if let Ok(cs_value) = CString::new(value) {
                    if let Ok(sdp) = Sdp::parse(&cs_value) {
                        return Ok(sdp)
                    }
                }
                Err(E::invalid_value(Unexpected::Str(value), &self))
            }
        }
        deserializer.deserialize_str(SdpVisitor)
    }
}

unsafe impl Send for Sdp {}

#[macro_export]
/// Given an SDP offer from a client, generates an SDP answer.
/// (This has to be a macro because `generate_answer` is variadic.)
macro_rules! answer_sdp {
    ($sdp:expr $(, $param:expr, $value:expr)* $(,)*) => {
        unsafe {
            let result = $crate::sdp::generate_answer(
                $sdp.ptr,
                $($param, $value,)*
                $crate::sdp::OfferAnswerParameters::Done
            );
            $crate::sdp::Sdp::new(result).expect("Mysterious error generating SDP answer :(")
        }
    }
}

#[macro_export]
/// Generates an SDP offer given some parameters.
/// (This has to be a macro because `generate_offer` is variadic.)
macro_rules! offer_sdp {
    ($name:expr, $address:expr $(, $param:expr, $value:expr)* $(,)*) => {
        unsafe {
            let result = $crate::sdp::generate_offer(
                $name,
                $address,
                $($param, $value,)*
                $crate::sdp::OfferAnswerParameters::Done
            );
            $crate::sdp::Sdp::new(result).expect("Mysterious error generating SDP offer :(")
        }
    }
}