1 files changed, 154 insertions, 0 deletions
diff --git a/formatable-float/src/lib.rs b/formatable-float/src/lib.rs
new file mode 100644
index 0000000..7b1db21
--- /dev/null
+++ b/formatable-float/src/lib.rs
@@ -0,0 +1,154 @@
+use serde::{Serialize,Deserialize,Serializer,Deserializer};
+use serde::de::Error as DeError;
+use serde::de::Unexpected as DeUnexpect;
+use std::collections::BTreeMap;
+use std::ops::{Add, Sub};
+use std::str::FromStr;
+use std::num::{ParseIntError,IntErrorKind};
+
+#[derive(Serialize, Deserialize)]
+#[serde(tag = "Format")]
+pub enum FormatableFloatValue<KeyTypeMetadata : KeyBackingTypeMetadata> {
+    Off,
+    Numeric {
+        #[serde(rename = "Label")]
+        label : String,
+        #[serde(rename = "DecimalDigits")]
+        digits : u8
+    },
+    Binned {
+        #[serde(rename = "Label")]
+        label: String,
+        #[serde(rename = "PercentToSymbolMap")]
+        bin_symbol_map : BTreeMap<FormatableFloatKey<KeyTypeMetadata>,String>
+    }
+}
+
+#[derive(Debug)]
+pub enum FormattingError {
+    EmptyMap {
+        numeric_fallback : String
+    }
+}
+impl std::fmt::Display for FormattingError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            FormattingError::EmptyMap{numeric_fallback} => { write!(f, "Formatting failed. Empty PercentToSymbolMap. Numeric value: {}", numeric_fallback) }
+        }
+    }
+}
+impl std::error::Error for FormattingError {}
+
+impl<KeyTypeMetadata : KeyBackingTypeMetadata> FormatableFloatValue<KeyTypeMetadata> {
+    pub fn format_float(&self, float : f32) -> Result<Option<String>, FormattingError> {
+        match self {
+            FormatableFloatValue::Numeric{ label, digits } => { Ok(Some(Self::format_float_numeric(float, label, *digits))) }
+            FormatableFloatValue::Binned{ label, bin_symbol_map } => { Some(Self::format_float_binned(float, label, bin_symbol_map)).transpose()}
+            FormatableFloatValue::Off => {Ok(None)}
+        }
+    }
+    pub fn format_float_binned(float : f32, label : &str, bin_symbol_map : &BTreeMap<FormatableFloatKey<KeyTypeMetadata>, String>) -> Result<String,FormattingError> {
+        let value_to_match = FormatableFloatKey::<KeyTypeMetadata>::match_float(float);
+        //first try to find the next lower value.
+        if let Some((_,msg)) = bin_symbol_map.range(..=value_to_match).next_back() {
+            Ok(format!("{}{}",label,msg))
+        }
+        else if let Some((_,msg)) = bin_symbol_map.iter().next() {
+            Ok(format!("{}{}",label,msg))
+        }
+        else {
+            Err(FormattingError::EmptyMap{numeric_fallback : Self::format_float_numeric(float, label, 0) })
+        }
+    }
+    pub fn format_float_numeric(float : f32, label : &str, digits : u8) -> String {
+        let percentage = 100.0*float;
+        format!("{}{:.*}%", label, digits as usize, percentage)
+    }
+}
+
+///Helper trait for conversion from float to integer backing type for binning keys.
+///Needed because Rust seems not to offer a trait that indicates "can be rounded from float"
+///in the standard library. There are thir-party crates that do this, but using a full crate
+///for a few lines of code sounds a bit excessive...
+pub trait BackingTypeFromFloat {
+    fn round_from_float(float : f32) -> Self;
+}
+
+///Metadata description for Keys. Basically a workaround for Rust's lack of
+///constant generics. Having Ord as supertrait is because of the BTreeMap's trait
+///bounds.
+pub trait KeyBackingTypeMetadata : Ord {
+    type BackingType 
+        : Ord
+        + Add<Output = Self::BackingType>
+        + Sub<Output = Self::BackingType>
+        + Into<f32>
+        + BackingTypeFromFloat
+        + ToString //TOML needs map keys to be strings...
+        + FromStr<Err = ParseIntError>
+        + std::fmt::Display;
+    const MIN : Self::BackingType;
+    const MAX : Self::BackingType;
+    const FLOAT_MIN : f32;
+    const FLOAT_MAX : f32;
+}
+
+#[derive(Debug,PartialEq,Eq,PartialOrd,Ord)]
+pub struct FormatableFloatKey<BackingType : KeyBackingTypeMetadata>(pub BackingType::BackingType);
+
+impl<BackingType : KeyBackingTypeMetadata> FormatableFloatKey<BackingType> {
+    fn match_float(float : f32) -> Self {
+        let x = (float - BackingType::FLOAT_MIN) / (BackingType::FLOAT_MAX - BackingType::FLOAT_MIN);
+        let cx = x.clamp(0.0,1.0);
+        let interval = BackingType::MAX.into() - BackingType::MIN.into();
+        let offset = interval * cx;
+        let result = BackingType::BackingType::round_from_float(offset) + BackingType::MIN;
+        Self(result)
+    }
+
+}
+/// Custom serializer, as TOML only supports string map keys.
+impl<Metadata : KeyBackingTypeMetadata> Serialize for FormatableFloatKey<Metadata> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S : Serializer 
+    {
+        let string = self.0.to_string();
+        serializer.serialize_str(&string)
+    }
+}
+impl<'de, Metadata> Deserialize<'de> for FormatableFloatKey<Metadata>
+    where Metadata : KeyBackingTypeMetadata,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        let a = String::deserialize(deserializer)?;
+        match a.parse() {
+            Ok(x) => { 
+                if x >= Metadata::MIN && x <= Metadata::MAX {
+                    Ok(Self(x)) 
+                }
+                else {
+                    Err(DeError::invalid_value(DeUnexpect::Str(&a), &&*format!("an integer equal or larger {} and equal or smaller {}", Metadata::MIN, Metadata::MAX)))
+                }
+            }
+            Err(e) => {
+                match e.kind() {
+                    IntErrorKind::Empty => { Err(DeError::missing_field("Bin Map Key")) }
+                    IntErrorKind::InvalidDigit => { Err(DeError::invalid_type(DeUnexpect::Str(&a), &"an integer value")) }
+                    IntErrorKind::NegOverflow | IntErrorKind::PosOverflow => { Err(DeError::invalid_value(DeUnexpect::Str(&a), &&*format!("an integer equal or larger {} and equal or smaller {}", Metadata::MIN, Metadata::MAX))) }
+                    IntErrorKind::Zero => { Err(DeError::invalid_value(DeUnexpect::Str(&a), &&*format!("a nonzero integer between {} and {}", Metadata::MIN, Metadata::MAX)))}
+                    _ => { Err(DeError::custom("Value could not be parsed")) }
+                }
+            }
+        }
+    }
+}
+macro_rules! impl_key_backing_type_from_float_for {
+    ($( $t:ty ), *) => {
+        $( impl BackingTypeFromFloat for $t {
+            fn round_from_float(float : f32) -> $t { float.round() as $t }
+        } )*
+    }
+}
+impl_key_backing_type_from_float_for!(i8, u8, i16, u16, i32, u32, i64, u64, isize, usize, i128, u128);