//! A `MakeVisitor` wrapper that separates formatted fields with a delimiter.

use super::{MakeVisitor, VisitFmt, VisitOutput};

use core::fmt;

use tracing_core::field::{Field, Visit};

/// A `MakeVisitor` wrapper that wraps a visitor that writes formatted output so

/// that a delimiter is inserted between writing formatted field values.

#[derive(Debug, Clone)]

pub struct Delimited<D, V> {

    delimiter: D,

    inner: V,

}

/// A visitor wrapper that inserts a delimiter after the wrapped visitor formats

/// a field value.

#[derive(Debug)]

pub struct VisitDelimited<D, V> {

    delimiter: D,

    seen: bool,

    inner: V,

    err: fmt::Result,

}

// === impl Delimited ===

impl<D, V, T> MakeVisitor<T> for Delimited<D, V>

where

    D: AsRef<str> + Clone,

    V: MakeVisitor<T>,

    V::Visitor: VisitFmt,

{

    type Visitor = VisitDelimited<D, V::Visitor>;

    fn make_visitor(&self, target: T) -> Self::Visitor {

        let inner = self.inner.make_visitor(target);

        VisitDelimited::new(self.delimiter.clone(), inner)

    }

}

impl<D, V> Delimited<D, V> {

    /// Returns a new [`MakeVisitor`] implementation that wraps `inner` so that

    /// it will format each visited field separated by the provided `delimiter`.

    ///

    /// [`MakeVisitor`]: super::MakeVisitor

    pub fn new(delimiter: D, inner: V) -> Self {

        Self { delimiter, inner }

    }

}

// === impl VisitDelimited ===

impl<D, V> VisitDelimited<D, V> {

    /// Returns a new [`Visit`] implementation that wraps `inner` so that

    /// each formatted field is separated by the provided `delimiter`.

    ///

    /// [`Visit`]: tracing_core::field::Visit

    pub fn new(delimiter: D, inner: V) -> Self {

        Self {

            delimiter,

            inner,

            seen: false,

            err: Ok(()),

        }

    }

    fn delimit(&mut self)

    where

        V: VisitFmt,

        D: AsRef<str>,

    {

        if self.err.is_err() {

            return;

        }

        if self.seen {

            self.err = self.inner.writer().write_str(self.delimiter.as_ref());

        }

        self.seen = true;

    }

}

impl<D, V> Visit for VisitDelimited<D, V>

where

    V: VisitFmt,

    D: AsRef<str>,

{

    fn record_i64(&mut self, field: &Field, value: i64) {

        self.delimit();

        self.inner.record_i64(field, value);

    }

    fn record_u64(&mut self, field: &Field, value: u64) {

        self.delimit();

        self.inner.record_u64(field, value);

    }

    fn record_bool(&mut self, field: &Field, value: bool) {

        self.delimit();

        self.inner.record_bool(field, value);

    }

    fn record_str(&mut self, field: &Field, value: &str) {

        self.delimit();

        self.inner.record_str(field, value);

    }

    fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {

        self.delimit();

        self.inner.record_debug(field, value);

    }

}

impl<D, V> VisitOutput<fmt::Result> for VisitDelimited<D, V>

where

    V: VisitFmt,

    D: AsRef<str>,

{

    fn finish(self) -> fmt::Result {

        self.err?;

        self.inner.finish()

    }

}

impl<D, V> VisitFmt for VisitDelimited<D, V>

where

    V: VisitFmt,

    D: AsRef<str>,

{

    fn writer(&mut self) -> &mut dyn fmt::Write {

        self.inner.writer()

    }

}

#[cfg(test)]

#[cfg(all(test, feature = "alloc"))]

mod test {

    use super::*;

    use crate::field::test_util::*;

    #[test]

    fn delimited_visitor() {

        let mut s = String::new();

        let visitor = DebugVisitor::new(&mut s);

        let mut visitor = VisitDelimited::new(", ", visitor);

        TestAttrs1::with(|attrs| attrs.record(&mut visitor));

        visitor.finish().unwrap();

        assert_eq!(

            s.as_str(),

            "question=\"life, the universe, and everything\", tricky=true, can_you_do_it=true"

        );

    }

    #[test]

    fn delimited_new_visitor() {

        let make = Delimited::new("; ", MakeDebug);

        TestAttrs1::with(|attrs| {

            let mut s = String::new();

            {

                let mut v = make.make_visitor(&mut s);

                attrs.record(&mut v);

            }

            assert_eq!(

                s.as_str(),

                "question=\"life, the universe, and everything\"; tricky=true; can_you_do_it=true"

            );

        });

        TestAttrs2::with(|attrs| {

            let mut s = String::new();

            {

                let mut v = make.make_visitor(&mut s);

                attrs.record(&mut v);

            }

            assert_eq!(

                s.as_str(),

                "question=None; question.answer=42; tricky=true; can_you_do_it=false"

            );

        });

    }

}