//! Contains structs and traits closely related to D-Bus messages.

use std::{fmt, ptr};
use super::{ffi, Error, libc, init_dbus};
use crate::strings::{BusName, Path, Interface, Member, ErrorName};
use std::ffi::CStr;

use super::arg::{Append, AppendAll, IterAppend, ReadAll, Get, Iter, Arg, RefArg, TypeMismatchError};

#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Hash)]
/// One of the four different message types.
pub enum MessageType {
    /// This is a method call D-Bus message
    MethodCall = 1,
    /// This is a method return Ok D-Bus message, used when the method call message was successfully processed
    MethodReturn = 2,
    /// This is a method return with error D-Bus message, used when the method call message could not be handled
    Error = 3,
    /// This is a signal, usually sent to whoever wants to listen
    Signal = 4,
}

mod signalargs;
pub use self::signalargs::SignalArgs;

mod matchrule;
pub use self::matchrule::MatchRule;


/// A D-Bus message. A message contains headers - usually destination address, path, interface and member,
/// and a list of arguments.
pub struct Message {
    msg: *mut ffi::DBusMessage,
}

unsafe impl Send for Message {}

impl Message {
    /// Creates a new method call message.
    pub fn new_method_call<'d, 'p, 'i, 'm, D, P, I, M>(destination: D, path: P, iface: I, method: M) -> Result<Message, String>
    where D: Into<BusName<'d>>, P: Into<Path<'p>>, I: Into<Interface<'i>>, M: Into<Member<'m>> {
        init_dbus();
        let (d, p, i, m) = (destination.into(), path.into(), iface.into(), method.into());
        let ptr = unsafe {
            ffi::dbus_message_new_method_call(d.as_ptr(), p.as_ptr(), i.as_ptr(), m.as_ptr())
        };
        if ptr.is_null() { Err("D-Bus error: dbus_message_new_method_call failed".into()) }
        else { Ok(Message { msg: ptr}) }
    }

    /// Creates a new method call message.
    pub fn method_call(destination: &BusName, path: &Path, iface: &Interface, name: &Member) -> Message {
        init_dbus();
        let ptr = unsafe {
            ffi::dbus_message_new_method_call(destination.as_ptr(), path.as_ptr(),
                iface.as_ptr(), name.as_ptr())
        };
        if ptr.is_null() { panic!("D-Bus error: dbus_message_new_method_call failed") }
        Message { msg: ptr}
    }

    /// Creates a new method call message.
    pub fn call_with_args<'d, 'p, 'i, 'm, A, D, P, I, M>(destination: D, path: P, iface: I, method: M, args: A) -> Message
    where D: Into<BusName<'d>>, P: Into<Path<'p>>, I: Into<Interface<'i>>, M: Into<Member<'m>>, A: AppendAll {
        let mut msg = Message::method_call(&destination.into(), &path.into(), &iface.into(), &method.into());
        msg.append_all(args);
        msg
    }

    /// Creates a new signal message.
    pub fn new_signal<P, I, M>(path: P, iface: I, name: M) -> Result<Message, String>
    where P: Into<String>, I: Into<String>, M: Into<String> {
        init_dbus();

        let p = Path::new(path)?;
        let i = Interface::new(iface)?;
        let m = Member::new(name)?;

        let ptr = unsafe {
            ffi::dbus_message_new_signal(p.as_ptr(), i.as_ptr(), m.as_ptr())
        };
        if ptr.is_null() { Err("D-Bus error: dbus_message_new_signal failed".into()) }
        else { Ok(Message { msg: ptr}) }
    }

    /// Creates a new signal message.
    pub fn signal(path: &Path, iface: &Interface, name: &Member) -> Message {
        init_dbus();
        let ptr = unsafe {
            ffi::dbus_message_new_signal(path.as_ptr(), iface.as_ptr(), name.as_ptr())
        };
        if ptr.is_null() { panic!("D-Bus error: dbus_message_new_signal failed") }
        Message { msg: ptr}
    }

    /// Creates a method reply for this method call.
    pub fn new_method_return(m: &Message) -> Option<Message> {
        let ptr = unsafe { ffi::dbus_message_new_method_return(m.msg) };
        if ptr.is_null() { None } else { Some(Message { msg: ptr} ) }
    }

    /// Creates a method return (reply) for this method call.
    pub fn method_return(&self) -> Message {
        let ptr = unsafe { ffi::dbus_message_new_method_return(self.msg) };
        if ptr.is_null() { panic!("D-Bus error: dbus_message_new_method_return failed") }
        Message {msg: ptr}
    }

    /// Creates a reply for a method call message.
    ///
    /// Panics if called for a message which is not a method call.
    pub fn return_with_args<A: AppendAll>(&self, args: A) -> Message {
        let mut m = self.method_return();
        m.append_all(args);
        m
    }

    /// Creates a new error reply
    pub fn error(&self, error_name: &ErrorName, error_message: &CStr) -> Message {
        let ptr = unsafe { ffi::dbus_message_new_error(self.msg, error_name.as_ptr(), error_message.as_ptr()) };
        if ptr.is_null() { panic!("D-Bus error: dbus_message_new_error failed") }
        Message { msg: ptr}
    }

    /// Get the MessageItems that make up the message.
    ///
    /// Note: use `iter_init` or `get1`/`get2`/etc instead for faster access to the arguments.
    /// This method is provided for backwards compatibility.
    pub fn get_items(&self) -> Vec<crate::arg::messageitem::MessageItem> {
        let mut i = self.iter_init();
        let mut v = vec!();
        while let Some(z) = crate::arg::messageitem::MessageItem::get(&mut i) { v.push(z); i.next(); }
        v
    }

    /// Get the D-Bus serial of a message, if one was specified.
    pub fn get_serial(&self) -> Option<u32> {
        let x = unsafe { ffi::dbus_message_get_serial(self.msg) };
        if x == 0 { None } else { Some(x) }
    }

    /// Get the serial of the message this message is a reply to, if present.
    pub fn get_reply_serial(&self) -> Option<u32> {
        let s = unsafe { ffi::dbus_message_get_reply_serial(self.msg) };
        if s == 0 { None } else { Some(s) }
    }

    /// Returns true if the message does not expect a reply.
    pub fn get_no_reply(&self) -> bool { unsafe { ffi::dbus_message_get_no_reply(self.msg) != 0 } }

    /// Set whether or not the message expects a reply.
    ///
    /// Set to true if you send a method call and do not want a reply.
    pub fn set_no_reply(&mut self, v: bool) {
        unsafe { ffi::dbus_message_set_no_reply(self.msg, if v { 1 } else { 0 }) }
    }

    /// Returns true if the message can cause a service to be auto-started.
    pub fn get_auto_start(&self) -> bool { unsafe { ffi::dbus_message_get_auto_start(self.msg) != 0 } }

    /// Sets whether or not the message can cause a service to be auto-started.
    ///
    /// Defaults to true.
    pub fn set_auto_start(&mut self, v: bool) {
        unsafe { ffi::dbus_message_set_auto_start(self.msg, if v { 1 } else { 0 }) }
    }

    /// Add one or more MessageItems to this Message.
    ///
    /// Note: using `append1`, `append2` or `append3` might be faster, especially for large arrays.
    /// This method is provided for backwards compatibility.
    pub fn append_items(&mut self, v: &[crate::arg::messageitem::MessageItem]) {
        let mut ia = IterAppend::new(self);
        for a in v { a.append_by_ref(&mut ia); }
    }

    /// Appends one argument to this message.
    /// Use in builder style: e g `m.method_return().append1(7i32)`
    pub fn append1<A: Append>(mut self, a: A) -> Self {
        {
            let mut m = IterAppend::new(&mut self);
            m.append(a);
        }
        self
    }

    /// Appends two arguments to this message.
    /// Use in builder style: e g `m.method_return().append2(7i32, 6u8)`
    pub fn append2<A1: Append, A2: Append>(mut self, a1: A1, a2: A2) -> Self {
        {
            let mut m = IterAppend::new(&mut self);
            m.append(a1); m.append(a2);
        }
        self
    }

    /// Appends three arguments to this message.
    /// Use in builder style: e g `m.method_return().append3(7i32, 6u8, true)`
    pub fn append3<A1: Append, A2: Append, A3: Append>(mut self, a1: A1, a2: A2, a3: A3) -> Self {
        {
            let mut m = IterAppend::new(&mut self);
            m.append(a1); m.append(a2); m.append(a3);
        }
        self
    }

    /// Appends RefArgs to this message.
    /// Use in builder style: e g `m.method_return().append_ref(&[7i32, 6u8, true])`
    pub fn append_ref<A: RefArg>(mut self, r: &[A]) -> Self {
        {
            let mut m = IterAppend::new(&mut self);
            for rr in r {
                rr.append(&mut m);
            }
        }
        self
    }

    /// Appends arguments to a message.
    pub fn append_all<A: AppendAll>(&mut self, a: A) {
        let mut m = IterAppend::new(self);
        a.append(&mut m);
    }

    /// Gets the first argument from the message, if that argument is of type G1.
    /// Returns None if there are not enough arguments, or if types don't match.
    pub fn get1<'a, G1: Get<'a>>(&'a self) -> Option<G1> {
        let mut i = Iter::new(&self);
        i.get()
    }

    /// Gets the first two arguments from the message, if those arguments are of type G1 and G2.
    /// Returns None if there are not enough arguments, or if types don't match.
    pub fn get2<'a, G1: Get<'a>, G2: Get<'a>>(&'a self) -> (Option<G1>, Option<G2>) {
        let mut i = Iter::new(&self);
        let g1 = i.get();
        if !i.next() { return (g1, None); }
        (g1, i.get())
    }

    /// Gets the first three arguments from the message, if those arguments are of type G1, G2 and G3.
    /// Returns None if there are not enough arguments, or if types don't match.
    pub fn get3<'a, G1: Get<'a>, G2: Get<'a>, G3: Get<'a>>(&'a self) -> (Option<G1>, Option<G2>, Option<G3>) {
        let mut i = Iter::new(&self);
        let g1 = i.get();
        if !i.next() { return (g1, None, None) }
        let g2 = i.get();
        if !i.next() { return (g1, g2, None) }
        (g1, g2, i.get())
    }

    /// Gets the first four arguments from the message, if those arguments are of type G1, G2, G3 and G4.
    /// Returns None if there are not enough arguments, or if types don't match.
    pub fn get4<'a, G1: Get<'a>, G2: Get<'a>, G3: Get<'a>, G4: Get<'a>>(&'a self) -> (Option<G1>, Option<G2>, Option<G3>, Option<G4>) {
        let mut i = Iter::new(&self);
        let g1 = i.get();
        if !i.next() { return (g1, None, None, None) }
        let g2 = i.get();
        if !i.next() { return (g1, g2, None, None) }
        let g3 = i.get();
        if !i.next() { return (g1, g2, g3, None) }
        (g1, g2, g3, i.get())
    }

    /// Gets the first five arguments from the message, if those arguments are of type G1, G2, G3 and G4.
    /// Returns None if there are not enough arguments, or if types don't match.
    /// Note: If you need more than five arguments, use `iter_init` instead.
    pub fn get5<'a, G1: Get<'a>, G2: Get<'a>, G3: Get<'a>, G4: Get<'a>, G5: Get<'a>>(&'a self) -> (Option<G1>, Option<G2>, Option<G3>, Option<G4>, Option<G5>) {
        let mut i = Iter::new(&self);
        let g1 = i.get();
        if !i.next() { return (g1, None, None, None, None) }
        let g2 = i.get();
        if !i.next() { return (g1, g2, None, None, None) }
        let g3 = i.get();
        if !i.next() { return (g1, g2, g3, None, None) }
        let g4 = i.get();
        if !i.next() { return (g1, g2, g3, g4, None) }
        (g1, g2, g3, g4, i.get())
    }

    /// Gets the first argument from the message, if that argument is of type G1.
    ///
    /// Returns a TypeMismatchError if there are not enough arguments, or if types don't match.
    pub fn read1<'a, G1: Arg + Get<'a>>(&'a self) -> Result<G1, TypeMismatchError> {
        let mut i = Iter::new(&self);
        i.read()
    }

    /// Gets the first two arguments from the message, if those arguments are of type G1 and G2.
    ///
    /// Returns a TypeMismatchError if there are not enough arguments, or if types don't match.
    pub fn read2<'a, G1: Arg + Get<'a>, G2: Arg + Get<'a>>(&'a self) -> Result<(G1, G2), TypeMismatchError> {
        let mut i = Iter::new(&self);
        Ok((i.read()?, i.read()?))
    }

    /// Gets the first three arguments from the message, if those arguments are of type G1, G2 and G3.
    ///
    /// Returns a TypeMismatchError if there are not enough arguments, or if types don't match.
    pub fn read3<'a, G1: Arg + Get<'a>, G2: Arg + Get<'a>, G3: Arg + Get<'a>>(&'a self) ->
        Result<(G1, G2, G3), TypeMismatchError> {
        let mut i = Iter::new(&self);
        Ok((i.read()?, i.read()?, i.read()?))
    }

    /// Gets the first four arguments from the message, if those arguments are of type G1, G2, G3 and G4.
    ///
    /// Returns a TypeMismatchError if there are not enough arguments, or if types don't match.
    pub fn read4<'a, G1: Arg + Get<'a>, G2: Arg + Get<'a>, G3: Arg + Get<'a>, G4: Arg + Get<'a>>(&'a self) ->
        Result<(G1, G2, G3, G4), TypeMismatchError> {
        let mut i = Iter::new(&self);
        Ok((i.read()?, i.read()?, i.read()?, i.read()?))
    }

    /// Gets the first five arguments from the message, if those arguments are of type G1, G2, G3, G4 and G5.
    ///
    /// Returns a TypeMismatchError if there are not enough arguments, or if types don't match.
    /// Note: If you need more than five arguments, use `iter_init` instead.
    pub fn read5<'a, G1: Arg + Get<'a>, G2: Arg + Get<'a>, G3: Arg + Get<'a>, G4: Arg + Get<'a>, G5: Arg + Get<'a>>(&'a self) ->
        Result<(G1, G2, G3, G4, G5), TypeMismatchError> {
        let mut i = Iter::new(&self);
        Ok((i.read()?, i.read()?, i.read()?, i.read()?, i.read()?))
    }

    /// Gets arguments from a message.
    ///
    /// If this was an error reply or if types mismatch, an error is returned.
    pub fn read_all<R: ReadAll>(&self) -> Result<R, Error> {
        self.set_error_from_msg()?;
        Ok(R::read(&mut self.iter_init())?)
    }

    /// Returns a struct for retreiving the arguments from a message. Supersedes get_items().
    pub fn iter_init(&self) -> Iter { Iter::new(&self) }

    /// Gets the MessageType of the Message.
    pub fn msg_type(&self) -> MessageType {
        match unsafe { ffi::dbus_message_get_type(self.msg) } {
            1 => MessageType::MethodCall,
            2 => MessageType::MethodReturn,
            3 => MessageType::Error,
            4 => MessageType::Signal,
            x => panic!("Invalid message type {}", x),
        }
    }

    fn msg_internal_str<'a>(&'a self, c: *const libc::c_char) -> Option<&'a str> {
        if c.is_null() { return None };
        let cc = unsafe { CStr::from_ptr(c) };
        std::str::from_utf8(cc.to_bytes_with_nul()).ok()
    }

    /// Gets the name of the connection that originated this message.
    pub fn sender(&self) -> Option<BusName> {
        self.msg_internal_str(unsafe { ffi::dbus_message_get_sender(self.msg) })
            .map(|s| unsafe { BusName::from_slice_unchecked(s) })
    }

    /// Gets the object path this Message is being sent to.
    pub fn path(&self) -> Option<Path> {
        self.msg_internal_str(unsafe { ffi::dbus_message_get_path(self.msg) })
            .map(|s| unsafe { Path::from_slice_unchecked(s) })
    }

    /// Gets the destination this Message is being sent to.
    pub fn destination(&self) -> Option<BusName> {
        self.msg_internal_str(unsafe { ffi::dbus_message_get_destination(self.msg) })
            .map(|s| unsafe { BusName::from_slice_unchecked(s) })
    }

    /// Sets the destination of this Message
    ///
    /// If dest is none, that means broadcast to all relevant destinations.
    pub fn set_destination(&mut self, dest: Option<BusName>) {
        let c_dest = dest.as_ref().map(|d| d.as_cstr().as_ptr()).unwrap_or(ptr::null());
        assert!(unsafe { ffi::dbus_message_set_destination(self.msg, c_dest) } != 0);
    }

    /// Gets the interface this Message is being sent to.
    pub fn interface(&self) -> Option<Interface> {
        self.msg_internal_str(unsafe { ffi::dbus_message_get_interface(self.msg) })
            .map(|s| unsafe { Interface::from_slice_unchecked(s) })
    }

    /// Gets the interface member being called.
    pub fn member(&self) -> Option<Member> {
        self.msg_internal_str(unsafe { ffi::dbus_message_get_member(self.msg) })
            .map(|s| unsafe { Member::from_slice_unchecked(s) })
    }

    /// When the remote end returns an error, the message itself is
    /// correct but its contents is an error. This method will
    /// transform such an error to a D-Bus Error or otherwise return
    /// the original message.
    pub fn as_result(&mut self) -> Result<&mut Message, Error> {
        self.set_error_from_msg().map(|_| self)
    }

    pub (crate) fn set_error_from_msg(&self) -> Result<(), Error> {
        let mut e = Error::empty();
        if unsafe { ffi::dbus_set_error_from_message(e.get_mut(), self.msg) } != 0 { Err(e) }
        else { Ok(()) }
    }

    pub (crate) fn ptr(&self) -> *mut ffi::DBusMessage { self.msg }

    pub (crate) fn from_ptr(ptr: *mut ffi::DBusMessage, add_ref: bool) -> Message {
        if add_ref {
            unsafe { ffi::dbus_message_ref(ptr) };
        }
        Message { msg: ptr }
    }

    /// Sets serial number manually - mostly for internal use
    ///
    /// When sending a message, a serial will be automatically assigned, so you don't need to call
    /// this method. However, it can be very useful in test code that is supposed to handle a method call.
    /// This way, you can create a method call and handle it without sending it to a real D-Bus instance.
    pub fn set_serial(&mut self, val: u32) {
        unsafe { ffi::dbus_message_set_serial(self.msg, val) };
    }

    /// Marshals a message - mostly for internal use
    ///
    /// The function f will be called one or more times with bytes to be written somewhere.
    /// You should call set_serial to manually set a serial number before calling this function
    pub fn marshal<E, F: FnMut(&[u8]) -> Result<(), E>>(&self, mut f: F) -> Result<(), E> {
        let mut len = 0;
        let mut data = ptr::null_mut();
        if unsafe { ffi::dbus_message_marshal(self.msg, &mut data, &mut len) } == 0 {
            panic!("out of memory");
        }
        let s = unsafe { std::slice::from_raw_parts(data as *mut u8 as *const u8, len as usize) };
        let r = f(s);
        unsafe { ffi::dbus_free(data as *mut _) };
        r
    }

    /// Demarshals a message - mostly for internal use
    pub fn demarshal(data: &[u8]) -> Result<Self, Error> {
        let mut e = Error::empty();
        let p = unsafe { ffi::dbus_message_demarshal(data.as_ptr() as *const _, data.len() as _, e.get_mut()) };
        if p == ptr::null_mut() {
            Err(e)
        } else {
            Ok(Self::from_ptr(p, false))
        }
    }

    /// Returns the size of the message - mostly for internal use
    ///
    /// Returns Err(()) on protocol errors. Make sure you have at least 16 bytes in the buffer
    /// before calling this method.
    pub fn demarshal_bytes_needed(data: &[u8]) -> Result<usize, ()> {
        const MIN_HEADER: usize = 16;
        if data.len() < MIN_HEADER { return Ok(MIN_HEADER); }
        let x = unsafe { ffi::dbus_message_demarshal_bytes_needed(data.as_ptr() as *const _, data.len() as _) };
        if x < MIN_HEADER as _ { Err(()) } else { Ok(x as usize) }
    }

}

impl Drop for Message {
    fn drop(&mut self) {
        unsafe {
            ffi::dbus_message_unref(self.msg);
        }
    }
}

impl fmt::Debug for Message {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        let mut x = f.debug_struct("Message");
        x.field("Type", &self.msg_type());
        // The &&** derefs to a &&str, which implements &dyn Debug
        if let Some(ref path) = self.path() { x.field("Path", &&**path); }
        if let Some(ref iface) = self.interface() { x.field("Interface", &&**iface); }
        if let Some(ref member) = self.member() { x.field("Member", &&**member); }
        if let Some(ref sender) = self.sender() { x.field("Sender", &&**sender); }
        if let Some(ref dest) = self.destination() { x.field("Destination", &&**dest); }
        if let Some(ref serial) = self.get_serial() { x.field("Serial", serial); }
        if let Some(ref rs) = self.get_reply_serial() { x.field("ReplySerial", rs); }
        let mut args = vec!();
        let mut iter = self.iter_init();
        while let Some(a) = iter.get_refarg() {
            args.push(a);
            iter.next();
        }
        let args2: &[_] = &args;
        x.field("Args", &args2);
        x.finish()
    }
}

#[cfg(test)]
mod test {
    use crate::{Message};
    use crate::strings::BusName;

    #[test]
    fn set_valid_destination() {
        let mut m = Message::new_method_call("org.test.rust", "/", "org.test.rust", "Test").unwrap();
        let d = Some(BusName::new(":1.14").unwrap());
        m.set_destination(d);

        assert!(!m.get_no_reply());
        m.set_no_reply(true);
        assert!(m.get_no_reply());
    }

    #[test]
    fn marshal() {
        let mut m = Message::new_method_call("org.freedesktop.DBus", "/org/freedesktop/DBus", "org.freedesktop.DBus", "Hello").unwrap();
        m.set_serial(1);
        let r = m.marshal(|d| {
            let m2 = Message::demarshal(d).unwrap();
            assert_eq!(&*m2.path().unwrap(), "/org/freedesktop/DBus");
            Err(45)
        });
        assert_eq!(45, r.unwrap_err());
    }
}