//! Enables base64'd output anywhere you might use a `Display` implementation, like a format string.

//!

//! ```

//! use base64::{display::Base64Display, engine::general_purpose::STANDARD};

//!

//! let data = vec![0x0, 0x1, 0x2, 0x3];

//! let wrapper = Base64Display::new(&data, &STANDARD);

//!

//! assert_eq!("base64: AAECAw==", format!("base64: {}", wrapper));

//! ```

use super::chunked_encoder::ChunkedEncoder;

use crate::engine::Engine;

use core::fmt::{Display, Formatter};

use core::{fmt, str};

/// A convenience wrapper for base64'ing bytes into a format string without heap allocation.

pub struct Base64Display<'a, 'e, E: Engine> {

    bytes: &'a [u8],

    chunked_encoder: ChunkedEncoder<'e, E>,

}

impl<'a, 'e, E: Engine> Base64Display<'a, 'e, E> {

    /// Create a `Base64Display` with the provided engine.

    pub fn new(bytes: &'a [u8], engine: &'e E) -> Base64Display<'a, 'e, E> {

        Base64Display {

            bytes,

            chunked_encoder: ChunkedEncoder::new(engine),

        }

    }

}

impl<'a, 'e, E: Engine> Display for Base64Display<'a, 'e, E> {

    fn fmt(&self, formatter: &mut Formatter) -> Result<(), fmt::Error> {

        let mut sink = FormatterSink { f: formatter };

        self.chunked_encoder.encode(self.bytes, &mut sink)

    }

}

struct FormatterSink<'a, 'b: 'a> {

    f: &'a mut Formatter<'b>,

}

impl<'a, 'b: 'a> super::chunked_encoder::Sink for FormatterSink<'a, 'b> {

    type Error = fmt::Error;

    fn write_encoded_bytes(&mut self, encoded: &[u8]) -> Result<(), Self::Error> {

        // Avoid unsafe. If max performance is needed, write your own display wrapper that uses

        // unsafe here to gain about 10-15%.

        self.f

            .write_str(str::from_utf8(encoded).expect("base64 data was not utf8"))

    }

}

#[cfg(test)]

mod tests {

    use super::super::chunked_encoder::tests::{

        chunked_encode_matches_normal_encode_random, SinkTestHelper,

    };

    use super::*;

    use crate::engine::general_purpose::STANDARD;

    #[test]

    fn basic_display() {

        assert_eq!(

            "~$Zm9vYmFy#*",

            format!("~${}#*", Base64Display::new(b"foobar", &STANDARD))

        );

        assert_eq!(

            "~$Zm9vYmFyZg==#*",

            format!("~${}#*", Base64Display::new(b"foobarf", &STANDARD))

        );

    }

    #[test]

    fn display_encode_matches_normal_encode() {

        let helper = DisplaySinkTestHelper;

        chunked_encode_matches_normal_encode_random(&helper);

    }

    struct DisplaySinkTestHelper;

    impl SinkTestHelper for DisplaySinkTestHelper {

        fn encode_to_string<E: Engine>(&self, engine: &E, bytes: &[u8]) -> String {

            format!("{}", Base64Display::new(bytes, engine))

        }

    }

}