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use crate::{Encoding, Utf8Encoding, Windows1252Encoding};

/// Trait customizing decoding values from binary data
pub trait BinaryFlavor: Sized + Encoding {
    /// Decode a f32 from 4 bytes of data
    fn visit_f32(&self, data: [u8; 4]) -> f32;

    /// Decode a f64 from 8 bytes of data
    fn visit_f64(&self, data: [u8; 8]) -> f64;
}

impl<T: BinaryFlavor> BinaryFlavor for &'_ T {
    fn visit_f32(&self, data: [u8; 4]) -> f32 {
        (**self).visit_f32(data)
    }

    fn visit_f64(&self, data: [u8; 8]) -> f64 {
        (**self).visit_f64(data)
    }
}

/// The eu4 binary flavor
#[derive(Debug, Default)]
pub struct Eu4Flavor(Windows1252Encoding);

impl Eu4Flavor {
    /// Creates a new eu4 flavor
    pub fn new() -> Self {
        Eu4Flavor(Windows1252Encoding::new())
    }
}

impl Encoding for Eu4Flavor {
    fn decode<'a>(&self, data: &'a [u8]) -> std::borrow::Cow<'a, str> {
        self.0.decode(data)
    }
}

impl BinaryFlavor for Eu4Flavor {
    fn visit_f32(&self, data: [u8; 4]) -> f32 {
        // First encoding is an i32 that has a fixed point offset of 3 decimal digits
        i32::from_le_bytes(data) as f32 / 1000.0
    }

    fn visit_f64(&self, data: [u8; 8]) -> f64 {
        // Second encoding is Q49.15 with 5 fractional digits
        // https://en.wikipedia.org/wiki/Q_(number_format)
        let val = i64::from_le_bytes(data) as f64 / 32768.0;
        (val * 10_0000.0).round() / 10_0000.0
    }
}

/// The ck3 binary flavor
#[derive(Debug, Default)]
pub struct Ck3Flavor(Utf8Encoding);

impl Ck3Flavor {
    /// Creates a new ck3 flavor
    pub fn new() -> Self {
        Ck3Flavor(Utf8Encoding::new())
    }
}

impl Encoding for Ck3Flavor {
    fn decode<'a>(&self, data: &'a [u8]) -> std::borrow::Cow<'a, str> {
        self.0.decode(data)
    }
}

impl BinaryFlavor for Ck3Flavor {
    fn visit_f32(&self, data: [u8; 4]) -> f32 {
        f32::from_bits(u32::from_le_bytes(data))
    }

    fn visit_f64(&self, data: [u8; 8]) -> f64 {
        i64::from_le_bytes(data) as f64 / 1000.0
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn eu4_flavor_f64_rounding() {
        // This test was taken by running an observer game (plaintext)
        // with cloud auto save (binary) and comparing the two and
        // noticing that truncation instead of rounding would yield
        // `2.49859` instead of the expected `2.49860`
        let flavor = Eu4Flavor(Windows1252Encoding::new());
        let data: [u8; 8] = [210, 63, 1, 0, 0, 0, 0, 0];
        let actual = flavor.visit_f64(data);
        assert_eq!(actual, 2.49860);
    }
}