1 files changed, 166 insertions, 0 deletions
diff --git a/src/json/canonical.rs b/src/json/canonical.rs
new file mode 100644
index 0000000..6de9517
--- /dev/null
+++ b/src/json/canonical.rs
@@ -0,0 +1,166 @@
+// Copyright © 2022 Kim Altintop <kim@eagain.io>
+// SPDX-License-Identifier: GPL-2.0-only WITH openvpn-openssl-exception
+
+use std::{
+    collections::BTreeMap,
+    io::Write,
+};
+
+use unicode_normalization::{
+    is_nfc_quick,
+    IsNormalized,
+    UnicodeNormalization as _,
+};
+
+use crate::metadata;
+
+pub mod error {
+    use std::io;
+
+    use thiserror::Error;
+
+    #[derive(Debug, Error)]
+    pub enum Canonicalise {
+        #[error(transparent)]
+        Cjson(#[from] Float),
+
+        #[error(transparent)]
+        Json(#[from] serde_json::Error),
+
+        #[error(transparent)]
+        Io(#[from] io::Error),
+    }
+
+    #[derive(Debug, Error)]
+    #[error("cannot canonicalise floating-point number")]
+    pub struct Float;
+}
+
+pub(crate) enum Value {
+    Null,
+    Bool(bool),
+    Number(Number),
+    String(String),
+    Array(Vec<Value>),
+    Object(BTreeMap<String, Value>),
+}
+
+impl TryFrom<&serde_json::Value> for Value {
+    type Error = error::Float;
+
+    fn try_from(js: &serde_json::Value) -> Result<Self, Self::Error> {
+        match js {
+            serde_json::Value::Null => Ok(Self::Null),
+            serde_json::Value::Bool(b) => Ok(Self::Bool(*b)),
+            serde_json::Value::Number(n) => n
+                .as_i64()
+                .map(Number::I64)
+                .or_else(|| n.as_u64().map(Number::U64))
+                .map(Self::Number)
+                .ok_or(error::Float),
+            serde_json::Value::String(s) => Ok(Self::String(to_nfc(s))),
+            serde_json::Value::Array(v) => {
+                let mut out = Vec::with_capacity(v.len());
+                for w in v.iter().map(TryFrom::try_from) {
+                    out.push(w?);
+                }
+                Ok(Self::Array(out))
+            },
+            serde_json::Value::Object(m) => {
+                let mut out = BTreeMap::new();
+                for (k, v) in m {
+                    out.insert(to_nfc(k), Self::try_from(v)?);
+                }
+                Ok(Self::Object(out))
+            },
+        }
+    }
+}
+
+impl TryFrom<&metadata::Custom> for Value {
+    type Error = error::Float;
+
+    fn try_from(js: &metadata::Custom) -> Result<Self, Self::Error> {
+        let mut out = BTreeMap::new();
+        for (k, v) in js {
+            out.insert(to_nfc(k), Self::try_from(v)?);
+        }
+        Ok(Self::Object(out))
+    }
+}
+
+impl serde::Serialize for Value {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        match self {
+            Value::Null => serializer.serialize_unit(),
+            Value::Bool(b) => serializer.serialize_bool(*b),
+            Value::Number(n) => n.serialize(serializer),
+            Value::String(s) => serializer.serialize_str(s),
+            Value::Array(v) => v.serialize(serializer),
+            Value::Object(m) => {
+                use serde::ser::SerializeMap;
+
+                let mut map = serializer.serialize_map(Some(m.len()))?;
+                for (k, v) in m {
+                    map.serialize_entry(k, v)?;
+                }
+                map.end()
+            },
+        }
+    }
+}
+
+pub(crate) enum Number {
+    I64(i64),
+    U64(u64),
+}
+
+impl serde::Serialize for Number {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        match self {
+            Number::I64(n) => serializer.serialize_i64(*n),
+            Number::U64(n) => serializer.serialize_u64(*n),
+        }
+    }
+}
+
+fn to_nfc(s: &String) -> String {
+    match is_nfc_quick(s.chars()) {
+        IsNormalized::Yes => s.clone(),
+        IsNormalized::No | IsNormalized::Maybe => s.nfc().collect(),
+    }
+}
+
+pub fn to_writer<W, T>(out: W, v: T) -> Result<(), error::Canonicalise>
+where
+    W: Write,
+    T: serde::Serialize,
+{
+    let js = serde_json::to_value(v)?;
+    let cj = Value::try_from(&js)?;
+    serde_json::to_writer(out, &cj).map_err(|e| {
+        if e.is_io() {
+            error::Canonicalise::Io(e.into())
+        } else {
+            error::Canonicalise::Json(e)
+        }
+    })?;
+
+    Ok(())
+}
+
+pub fn to_vec<T>(v: T) -> Result<Vec<u8>, error::Canonicalise>
+where
+    T: serde::Serialize,
+{
+    let mut buf = Vec::new();
+    to_writer(&mut buf, v)?;
+
+    Ok(buf)
+}