/// Logging handle used to execute logging statements
///
/// Logger handles logging context (key-value list) and handles logging
/// statements.
///
/// Child loggers are build from existing loggers, and inherit existing
/// key-value pairs from their parents, which can be supplemented with
/// new ones.
///
/// Cloning existing loggers and creating new ones is cheap. Loggers can be
/// freely passed around the code.
#[derive(Clone)]
pub struct Logger {
    drain: Arc<Drain<Error=Never>+Send+Sync>,
    values: OwnedKeyValueList,
}

impl Logger {
    /// Build a root `Logger`
    ///
    /// All children and their children and so on form one hierarchy
    /// sharing a common drain.
    ///
    /// Root logger starts a new hierarchy associated with a given `Drain`. Root
    /// logger drain must return no errors. See `DrainExt::ignore_err()` and
    ///
    /// `DrainExt::fuse()`.
    /// Use `o!` macro to help build key-value pairs with a nicer syntax.
    ///
    /// ```
    /// #[macro_use]
    /// extern crate slog;
    ///
    /// fn main() {
    ///     let root = slog::Logger::root(
    ///         slog::Discard,
    ///         o!("key1" => "value1", "key2" => "value2"),
    ///     );
    /// }
    pub fn root<D: 'static + Drain<Error=Never> + Sized+Send+Sync>(d: D, values: Option<Box<ser::SyncMultiSerialize>>) -> Logger {
        Logger {
            drain: Arc::new(d),
            values: OwnedKeyValueList::root(values),
        }
    }

    /// Build a child logger
    ///
    /// Child logger inherits all existing key-value pairs from it's parent.
    ///
    /// All children, their children and so on, form one hierarchy sharing
    /// a common drain.
    ///
    /// Use `o!` macro to help build key value pairs using nicer syntax.
    ///
    /// ```
    /// #[macro_use]
    /// extern crate slog;
    ///
    /// fn main() {
    ///     let root = slog::Logger::root(slog::Discard,
    ///         o!("key1" => "value1", "key2" => "value2"));
    ///     let log = root.new(o!("key" => "value"));
    /// }
    pub fn new(&self, values: Option<Box<ser::SyncMultiSerialize>>) -> Logger {
        Logger {
            drain: self.drain.clone(),
            values: if let Some(v) = values {
                OwnedKeyValueList::new(v, self.values.clone())
            } else {
                self.values.clone()
            },
        }
    }

    /// Log one logging record
    ///
    /// Use specific logging functions instead. See `log!` macro
    /// documentation.
    #[inline]
    pub fn log(&self, record: &Record) {
        let _ = self.drain.log(&record, &self.values);
    }
}

impl fmt::Debug for Logger {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        try!(write!(f, "Logger("));
        for (i, (key, _)) in self.values.iter().enumerate() {
            if i != 0 {
                try!(write!(f, ", "));
            }

            try!(write!(f, "{}", key));
        }
        try!(write!(f, ")"));
        Ok(())
    }
}

#[doc(hidden)]
pub struct RecordStatic<'a> {
    /// Logging level
    pub level: Level,
    /// File
    pub file: &'static str,
    /// Line
    pub line: u32,
    /// Column (currently not implemented)
    pub column: u32,
    /// Function (currently not implemented)
    pub function: &'static str,
    /// Module
    pub module: &'static str,
    /// Target - for backward compatibility with `log`
    pub target: &'a str,
}

/// One logging record
///
/// Corresponds to one logging statement like `info!(...)` and carries all it's
/// data: eg. message, key-values, key-values of `Logger` used to execute it.
///
/// Record is passed to `Drain` associated with a given logger hierarchy.
pub struct Record<'a> {
    meta: &'a RecordStatic<'a>,
    msg: fmt::Arguments<'a>,
    values: &'a [BorrowedKeyValue<'a>],
}


impl<'a> Record<'a> {
    /// Create a new `Record`
    #[inline]
    #[doc(hidden)]
    pub fn new(
        s : &'a RecordStatic<'a>,
        msg: fmt::Arguments<'a>,
        values: &'a [BorrowedKeyValue<'a>],
        ) -> Self {
        Record {
            meta: s,
            msg: msg,
            values: values,
        }
    }

    /// Get a log record message
    pub fn msg(&self) -> fmt::Arguments {
        self.msg
    }

    /// Get record logging level
    pub fn level(&self) -> Level {
        self.meta.level
    }

    /// Get line number
    pub fn line(&self) -> u32 {
        self.meta.line
    }

    /// Get error column
    pub fn column(&self) -> u32 {
        self.meta.column
    }

    /// Get file path
    pub fn file(&self) -> &'static str {
        self.meta.file
    }

    /// Get target
    ///
    /// Mostly for backward compatibility with `log`
    pub fn target(&self) -> &str {
        self.meta.target
    }

    /// Get module
    pub fn module(&self) -> &'static str {
        self.meta.module
    }

    /// Get function
    pub fn function(&self) -> &'static str {
        self.meta.function
    }

    /// Get Record's key-value pairs
    pub fn values(&self) -> &'a [BorrowedKeyValue<'a>] {
        self.values
    }
}