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|
use dhall_core::*;
use itertools::*;
use serde_cbor::value::value as cbor;
type ParsedExpr = Expr<X, Import>;
#[derive(Debug)]
pub enum DecodeError {
CBORError(serde_cbor::error::Error),
WrongFormatError,
}
pub fn decode(data: &[u8]) -> Result<ParsedExpr, DecodeError> {
match serde_cbor::de::from_slice(data) {
Ok(v) => cbor_value_to_dhall(&v),
Err(e) => Err(DecodeError::CBORError(e)),
}
}
fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
use cbor::Value::*;
use dhall_core::{BinOp, Builtin, Const};
use Expr::*;
match data {
String(s) => match Builtin::parse(s) {
Some(b) => Ok(Expr::Builtin(b)),
None => match s.as_str() {
"True" => Ok(Expr::BoolLit(true)),
"False" => Ok(Expr::BoolLit(false)),
"Type" => Ok(Expr::Const(Const::Type)),
"Kind" => Ok(Expr::Const(Const::Kind)),
s => Ok(Expr::Var(V(Label::from(s), 0))),
},
},
U64(n) => Ok(Expr::Var(V(Label::from("_"), *n as usize))),
F64(x) => Ok(DoubleLit(*x)),
Bool(b) => Ok(BoolLit(*b)),
Array(vec) => match vec.as_slice() {
[String(l), U64(n)] => {
let l = Label::from(l.as_str());
Ok(Expr::Var(V(l, *n as usize)))
}
[U64(0), f, args..] => {
let f = cbor_value_to_dhall(&f)?;
let args = args
.iter()
.map(cbor_value_to_dhall)
.collect::<Result<Vec<_>, _>>()?;
Ok(args
.into_iter()
.fold(f, |acc, e| (Expr::App(bx(acc), bx(e)))))
}
[U64(1), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
Ok(Lam(Label::from("_"), x, y))
}
[U64(1), String(l), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
let l = Label::from(l.as_str());
Ok(Lam(l, x, y))
}
[U64(2), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
Ok(Pi(Label::from("_"), x, y))
}
[U64(2), String(l), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
let l = Label::from(l.as_str());
Ok(Pi(l, x, y))
}
[U64(3), U64(n), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
use BinOp::*;
let op = match n {
0 => BoolOr,
1 => BoolAnd,
2 => BoolEQ,
3 => BoolNE,
4 => NaturalPlus,
5 => NaturalTimes,
6 => TextAppend,
7 => ListAppend,
8 => Combine,
9 => Prefer,
10 => CombineTypes,
11 => ImportAlt,
_ => Err(DecodeError::WrongFormatError)?,
};
Ok(BinOp(op, x, y))
}
[U64(4), t] => {
let t = bx(cbor_value_to_dhall(&t)?);
Ok(ListLit(Some(t), vec![]))
}
[U64(4), Null, rest..] => {
let rest = rest
.iter()
.map(cbor_value_to_dhall)
.collect::<Result<Vec<_>, _>>()?;
Ok(ListLit(None, rest))
}
[U64(5), t] => {
let t = bx(cbor_value_to_dhall(&t)?);
Ok(OptionalLit(Some(t), vec![]))
}
[U64(5), Null, x] => {
let x = cbor_value_to_dhall(&x)?;
Ok(OptionalLit(None, vec![x]))
}
[U64(5), t, x] => {
let x = cbor_value_to_dhall(&x)?;
let t = bx(cbor_value_to_dhall(&t)?);
Ok(OptionalLit(Some(t), vec![x]))
}
[U64(6), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
Ok(Merge(x, y, None))
}
[U64(6), x, y, z] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
let z = bx(cbor_value_to_dhall(&z)?);
Ok(Merge(x, y, Some(z)))
}
[U64(7), Object(map)] => {
let map = cbor_map_to_dhall_map(map)?;
Ok(Record(map))
}
[U64(8), Object(map)] => {
let map = cbor_map_to_dhall_map(map)?;
Ok(RecordLit(map))
}
[U64(9), x, String(l)] => {
let x = bx(cbor_value_to_dhall(&x)?);
let l = Label::from(l.as_str());
Ok(Field(x, l))
}
[U64(11), Object(map)] => {
let map = cbor_map_to_dhall_map(map)?;
Ok(Union(map))
}
[U64(12), String(l), x, Object(map)] => {
let map = cbor_map_to_dhall_map(map)?;
let x = bx(cbor_value_to_dhall(&x)?);
let l = Label::from(l.as_str());
Ok(UnionLit(l, x, map))
}
[U64(14), x, y, z] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
let z = bx(cbor_value_to_dhall(&z)?);
Ok(BoolIf(x, y, z))
}
[U64(15), U64(x)] => Ok(NaturalLit(*x as Natural)),
[U64(16), U64(x)] => Ok(IntegerLit(*x as Integer)),
[U64(16), I64(x)] => Ok(IntegerLit(*x as Integer)),
[U64(18), String(first), _rest..] => {
// TODO: interpolated string
Ok(TextLit(first.clone()))
}
[U64(25), bindings..] => {
let mut tuples = bindings.iter().tuples();
let bindings = (&mut tuples)
.map(|(x, t, v)| {
let x = match x {
String(s) => Label::from(s.as_str()),
_ => Err(DecodeError::WrongFormatError)?,
};
let t = match t {
Null => None,
t => Some(bx(cbor_value_to_dhall(&t)?)),
};
let v = bx(cbor_value_to_dhall(&v)?);
Ok((x, t, v))
})
.collect::<Result<Vec<_>, _>>()?;
let expr = tuples
.into_buffer()
.next()
.ok_or(DecodeError::WrongFormatError)?;
let expr = cbor_value_to_dhall(expr)?;
Ok(bindings
.into_iter()
.fold(expr, |acc, (x, t, v)| Let(x, t, v, bx(acc))))
}
[U64(26), x, y] => {
let x = bx(cbor_value_to_dhall(&x)?);
let y = bx(cbor_value_to_dhall(&y)?);
Ok(Annot(x, y))
}
_ => Err(DecodeError::WrongFormatError),
},
_ => Err(DecodeError::WrongFormatError),
}
}
fn cbor_map_to_dhall_map(
map: &std::collections::BTreeMap<cbor::ObjectKey, cbor::Value>,
) -> Result<std::collections::BTreeMap<Label, ParsedExpr>, DecodeError> {
map.iter()
.map(|(k, v)| -> Result<(_, _), _> {
let k = k.as_string().ok_or(DecodeError::WrongFormatError)?;
let v = cbor_value_to_dhall(v)?;
Ok((Label::from(k.as_ref()), v))
})
.collect::<Result<_, _>>()
}
|
