ptero-cli 0.4.2

//! # Description
//!
//! This method implements the *Extended Line* steganography algorithm. It consist of three
//! simpler methods:
//! * [RandomWhitespaceMethod](crate::method::random_whitespace::RandomWhitespaceMethod),
//! * [LineExtendMethod](crate::method::line_extend::LineExtendMethod),
//! * [TrailingWhitespaceMethod](crate::trailing_whitespace::TrailingWhitespaceMethod).
//!
//! For more info read docs on each one of the above encoders.

use crate::{
    context::{PivotByLineContext, PivotByRawLineContext},
    impl_complex_decoder, impl_complex_encoder,
    method::{line_extend, random_whitespace, trailing_whitespace, Method},
};

type ExtendedLineSubmethod = Box<dyn Method<PivotByLineContext, PivotByRawLineContext>>;

/// Structure representing the Extended Line algorithm.
/// Contains the vector of used methods. Uses macros to implement the required traits.
pub struct ExtendedLineMethod {
    methods: Vec<ExtendedLineSubmethod>,
}

impl Default for ExtendedLineMethod {
    fn default() -> Self {
        ExtendedLineMethodBuilder::new().build()
    }
}

#[derive(Debug, PartialEq)]
pub enum ExtendedLineMethodVariant {
    Variant1,
    Variant2,
    Variant3,
}

pub struct ExtendedLineMethodBuilder {
    variant: ExtendedLineMethodVariant,
}

impl ExtendedLineMethodBuilder {
    pub fn new() -> Self {
        ExtendedLineMethodBuilder {
            variant: ExtendedLineMethodVariant::Variant1,
        }
    }

    pub fn variant(mut self, variant: ExtendedLineMethodVariant) -> Self {
        self.variant = variant;
        self
    }

    fn select_methods(&self) -> Vec<ExtendedLineSubmethod> {
        let indices = match self.variant {
            ExtendedLineMethodVariant::Variant1 => &[0, 1, 2],
            ExtendedLineMethodVariant::Variant2 => &[1, 0, 2],
            ExtendedLineMethodVariant::Variant3 => &[1, 2, 0],
        };

        indices
            .iter()
            .map(|i| {
                let method: ExtendedLineSubmethod = match i {
                    0 => Box::new(random_whitespace::RandomWhitespaceMethod::default()),
                    1 => Box::new(line_extend::LineExtendMethod::default()),
                    _ => Box::new(trailing_whitespace::TrailingWhitespaceMethod::default()),
                };
                method
            })
            .collect()
    }

    pub fn build(&self) -> ExtendedLineMethod {
        ExtendedLineMethod {
            methods: self.select_methods(),
        }
    }
}

impl_complex_encoder!(ExtendedLineMethod, PivotByLineContext);
impl_complex_decoder!(ExtendedLineMethod, PivotByRawLineContext);

impl Method<PivotByLineContext, PivotByRawLineContext> for ExtendedLineMethod {
    fn method_name(&self) -> String {
        format!(
            "ExtendedLineMethod({},{},{})",
            self.methods[0].method_name(),
            self.methods[1].method_name(),
            self.methods[2].method_name(),
        )
    }
}

#[allow(unused_imports)]
mod test {
    use std::error::Error;

    use crate::{
        binary::BitIterator,
        context::{PivotByLineContext, PivotByRawLineContext},
        decoder::Decoder,
        encoder::Encoder,
        method::Method,
    };

    use super::{ExtendedLineMethod, ExtendedLineMethodBuilder, ExtendedLineMethodVariant};

    #[test]
    fn encodes_text_data() -> Result<(), Box<dyn Error>> {
        let cover_input = "a b c".repeat(5);
        let data_input = "a";
        let pivot: usize = 4;

        let mut data_iterator = BitIterator::new(&data_input.as_bytes());
        let method = ExtendedLineMethod::default();
        let mut context = PivotByLineContext::new(&cover_input, pivot);
        let stego_text = method.encode(&mut context, &mut data_iterator, None)?;

        assert_eq!(&stego_text, "a b ca \nb ca\nb ca b\nca b\nc \n");
        Ok(())
    }

    #[test]
    fn encodes_binary_data() -> Result<(), Box<dyn Error>> {
        let cover_input = "a b c ".repeat(5);
        let data_input: Vec<u8> = vec![0b11111111];
        let pivot: usize = 3;

        let mut data_iterator = BitIterator::new(&data_input);
        let method = ExtendedLineMethod::default();
        let mut context = PivotByLineContext::new(&cover_input, pivot);
        let stego_text = method.encode(&mut context, &mut data_iterator, None)?;

        assert_eq!(&stego_text, "a  b c \na  b c \na  b c\na b\nc a\nb c \n");
        Ok(())
    }

    #[test]
    fn decodes_binary_data() -> Result<(), Box<dyn Error>> {
        let stego_text = "a  bc\na bcd\na  b d \n";
        let pivot: usize = 4;

        let method = ExtendedLineMethod::default();
        let mut context = PivotByRawLineContext::new(&stego_text, pivot);
        let secret_data = method.decode(&mut context, None)?;

        assert_eq!(&secret_data, &[0b100_010_11, 0b100_000_00]);
        Ok(())
    }

    #[test]
    fn decodes_zeroes_if_no_data_encoded() -> Result<(), Box<dyn Error>> {
        let stego_text = "a\n".repeat(5);
        let pivot: usize = 4;

        let method = ExtendedLineMethod::default();
        let mut context = PivotByRawLineContext::new(&stego_text, pivot);
        let secret_data = method.decode(&mut context, None)?;

        assert_eq!(&secret_data, &[0, 0]);
        Ok(())
    }

    #[test]
    fn default_method_is_variant_1() -> Result<(), Box<dyn Error>> {
        assert_eq!(
            ExtendedLineMethod::default().method_name(),
            "ExtendedLineMethod(RandomWhitespaceMethod,LineExtendMethod,TrailingWhitespaceMethod)"
        );
        Ok(())
    }

    #[test]
    fn builder_properly_constructs_variants() -> Result<(), Box<dyn Error>> {
        assert_eq!(
            ExtendedLineMethodBuilder::new()
                .variant(ExtendedLineMethodVariant::Variant1)
                .build()
                .method_name(),
            "ExtendedLineMethod(RandomWhitespaceMethod,LineExtendMethod,TrailingWhitespaceMethod)"
        );
        assert_eq!(
            ExtendedLineMethodBuilder::new()
                .variant(ExtendedLineMethodVariant::Variant2)
                .build()
                .method_name(),
            "ExtendedLineMethod(LineExtendMethod,RandomWhitespaceMethod,TrailingWhitespaceMethod)"
        );
        assert_eq!(
            ExtendedLineMethodBuilder::new()
                .variant(ExtendedLineMethodVariant::Variant3)
                .build()
                .method_name(),
            "ExtendedLineMethod(LineExtendMethod,TrailingWhitespaceMethod,RandomWhitespaceMethod)"
        );
        Ok(())
    }
}