//! An object that can be used to pass through a channel and be cloned. It can therefore be used
//! via the broadcast channel.

use parking_lot::Mutex;
use serde::ser::SerializeMap;
use serde::serde_if_integer128;
use serde::Serialize;
use slog::{BorrowedKV, Key, Level, OwnedKVList, Record, RecordStatic, Serializer, SingleKV, KV};
use std::cell::RefCell;
use std::fmt;
use std::fmt::Write;
use std::sync::Arc;
use take_mut::take;

thread_local! {
    static TL_BUF: RefCell<String> = RefCell::new(String::with_capacity(128))
}

/// Serialized record.
#[derive(Clone)]
pub struct AsyncRecord {
    msg: String,
    level: Level,
    location: Box<slog::RecordLocation>,
    tag: String,
    logger_values: OwnedKVList,
    kv: Arc<Mutex<dyn KV + Send>>,
}

impl AsyncRecord {
    /// Serializes a `Record` and an `OwnedKVList`.
    pub fn from(record: &Record, logger_values: &OwnedKVList) -> Self {
        let mut ser = ToSendSerializer::new();
        record
            .kv()
            .serialize(record, &mut ser)
            .expect("`ToSendSerializer` can't fail");

        AsyncRecord {
            msg: fmt::format(*record.msg()),
            level: record.level(),
            location: Box::new(*record.location()),
            tag: String::from(record.tag()),
            logger_values: logger_values.clone(),
            kv: Arc::new(Mutex::new(ser.finish())),
        }
    }

    pub fn to_json_string(&self) -> Result<String, String> {
        serde_json::to_string(&self).map_err(|e| format!("{:?}", e))
    }
}

pub struct ToSendSerializer {
    kv: Box<dyn KV + Send>,
}

impl ToSendSerializer {
    fn new() -> Self {
        ToSendSerializer { kv: Box::new(()) }
    }

    fn finish(self) -> Box<dyn KV + Send> {
        self.kv
    }
}

impl Serializer for ToSendSerializer {
    fn emit_bool(&mut self, key: Key, val: bool) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_unit(&mut self, key: Key) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, ()))));
        Ok(())
    }
    fn emit_none(&mut self, key: Key) -> slog::Result {
        let val: Option<()> = None;
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_char(&mut self, key: Key, val: char) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_u8(&mut self, key: Key, val: u8) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_i8(&mut self, key: Key, val: i8) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_u16(&mut self, key: Key, val: u16) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_i16(&mut self, key: Key, val: i16) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_u32(&mut self, key: Key, val: u32) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_i32(&mut self, key: Key, val: i32) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_f32(&mut self, key: Key, val: f32) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_u64(&mut self, key: Key, val: u64) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_i64(&mut self, key: Key, val: i64) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_f64(&mut self, key: Key, val: f64) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_u128(&mut self, key: Key, val: u128) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_i128(&mut self, key: Key, val: i128) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_usize(&mut self, key: Key, val: usize) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_isize(&mut self, key: Key, val: isize) -> slog::Result {
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_str(&mut self, key: Key, val: &str) -> slog::Result {
        let val = val.to_owned();
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
    fn emit_arguments(&mut self, key: Key, val: &fmt::Arguments) -> slog::Result {
        let val = fmt::format(*val);
        take(&mut self.kv, |kv| Box::new((kv, SingleKV(key, val))));
        Ok(())
    }
}

impl Serialize for AsyncRecord {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        // Get the current time
        let dt = chrono::Local::now().format("%b %e %T").to_string();

        let rs = RecordStatic {
            location: &self.location,
            level: self.level,
            tag: &self.tag,
        };
        let mut map_serializer = SerdeSerializer::new(serializer)?;

        // Serialize the time and log level first
        map_serializer.serialize_entry("time", &dt)?;
        map_serializer.serialize_entry("level", self.level.as_short_str())?;

        let kv = self.kv.lock();

        // Convoluted pattern to avoid binding `format_args!` to a temporary.
        // See: https://stackoverflow.com/questions/56304313/cannot-use-format-args-due-to-temporary-value-is-freed-at-the-end-of-this-state
        let mut f = |msg: std::fmt::Arguments| {
            map_serializer.serialize_entry("msg", msg.to_string())?;

            let record = Record::new(&rs, &msg, BorrowedKV(&(*kv)));
            self.logger_values
                .serialize(&record, &mut map_serializer)
                .map_err(serde::ser::Error::custom)?;
            record
                .kv()
                .serialize(&record, &mut map_serializer)
                .map_err(serde::ser::Error::custom)
        };
        f(format_args!("{}", self.msg))?;
        map_serializer.end()
    }
}

struct SerdeSerializer<S: serde::Serializer> {
    /// Current state of map serializing: `serde::Serializer::MapState`
    ser_map: S::SerializeMap,
}

impl<S: serde::Serializer> SerdeSerializer<S> {
    fn new(ser: S) -> Result<Self, S::Error> {
        let ser_map = ser.serialize_map(None)?;
        Ok(SerdeSerializer { ser_map })
    }

    fn serialize_entry<K, V>(&mut self, key: K, value: V) -> Result<(), S::Error>
    where
        K: serde::Serialize,
        V: serde::Serialize,
    {
        self.ser_map.serialize_entry(&key, &value)
    }

    /// Finish serialization, and return the serializer
    fn end(self) -> Result<S::Ok, S::Error> {
        self.ser_map.end()
    }
}

// NOTE: This is borrowed from slog_json
macro_rules! impl_m(
    ($s:expr, $key:expr, $val:expr) => ({
        let k_s:  &str = $key.as_ref();
        $s.ser_map.serialize_entry(k_s, $val)
             .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, format!("serde serialization error: {}", e)))?;
        Ok(())
    });
);

impl<S> slog::Serializer for SerdeSerializer<S>
where
    S: serde::Serializer,
{
    fn emit_bool(&mut self, key: Key, val: bool) -> slog::Result {
        impl_m!(self, key, &val)
    }

    fn emit_unit(&mut self, key: Key) -> slog::Result {
        impl_m!(self, key, &())
    }

    fn emit_char(&mut self, key: Key, val: char) -> slog::Result {
        impl_m!(self, key, &val)
    }

    fn emit_none(&mut self, key: Key) -> slog::Result {
        let val: Option<()> = None;
        impl_m!(self, key, &val)
    }
    fn emit_u8(&mut self, key: Key, val: u8) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_i8(&mut self, key: Key, val: i8) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_u16(&mut self, key: Key, val: u16) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_i16(&mut self, key: Key, val: i16) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_usize(&mut self, key: Key, val: usize) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_isize(&mut self, key: Key, val: isize) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_u32(&mut self, key: Key, val: u32) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_i32(&mut self, key: Key, val: i32) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_f32(&mut self, key: Key, val: f32) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_u64(&mut self, key: Key, val: u64) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_i64(&mut self, key: Key, val: i64) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_f64(&mut self, key: Key, val: f64) -> slog::Result {
        impl_m!(self, key, &val)
    }
    serde_if_integer128! {
        fn emit_u128(&mut self, key: Key, val: u128) -> slog::Result {
            impl_m!(self, key, &val)
        }
        fn emit_i128(&mut self, key: Key, val: i128) -> slog::Result {
            impl_m!(self, key, &val)
        }
    }
    fn emit_str(&mut self, key: Key, val: &str) -> slog::Result {
        impl_m!(self, key, &val)
    }
    fn emit_arguments(&mut self, key: Key, val: &fmt::Arguments) -> slog::Result {
        TL_BUF.with(|buf| {
            let mut buf = buf.borrow_mut();

            buf.write_fmt(*val).unwrap();

            let res = { || impl_m!(self, key, &*buf) }();
            buf.clear();
            res
        })
    }
}