preserves/implementations/rust/preserves/src/value/reader.rs

use crate::error::{self, ExpectedKind, io_eof};

use std::borrow::Cow;
use std::io;
use std::marker::PhantomData;

use super::CompoundClass;
use super::DomainDecode;
use super::Double;
use super::DummyValue;
use super::Float;
use super::IOValue;
use super::IOValueDomainCodec;
use super::NestedValue;
use super::boundary as B;
use super::signed_integer::SignedInteger;

pub type ReaderResult<T> = std::result::Result<T, error::Error>;

#[derive(Debug)]
pub enum Token<N: NestedValue> {
    Embedded(N::Embedded),
    Atom(N),
    Compound(CompoundClass),
    End,
}

pub trait Reader<'de> {
    fn next<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<Option<N>>;

    fn open_record(&mut self) -> ReaderResult<()>; // followed by label, then fields
    fn open_sequence(&mut self) -> ReaderResult<()>; // followed by items
    fn open_set(&mut self) -> ReaderResult<()>; // followed by items
    fn open_dictionary(&mut self) -> ReaderResult<()>; // followed by key/value pairs
    fn boundary(&mut self, b: &B::Type) -> ReaderResult<()>;

    // Answers true for closed, false for more.
    // Implies a b.shift of None if closed or of Some(i) if not closed, plus a .boundary.
    fn close_compound(&mut self, b: &mut B::Type, i: &B::Item) -> ReaderResult<bool>;

    fn open_embedded(&mut self) -> ReaderResult<()>;
    fn close_embedded(&mut self) -> ReaderResult<()>;

    type Mark;
    fn mark(&mut self) -> io::Result<Self::Mark>;
    fn restore(&mut self, mark: &Self::Mark) -> io::Result<()>;

    fn next_token<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_embedded_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<Token<N>>;

    //---------------------------------------------------------------------------

    fn skip_value(&mut self) -> io::Result<()> {
        // TODO efficient skipping in specific impls of this trait
        let _: DummyValue<IOValue> = self.demand_next(false, &mut IOValueDomainCodec)?;
        Ok(())
    }

    fn next_iovalue(&mut self, read_annotations: bool) -> io::Result<IOValue> {
        self.demand_next(read_annotations, &mut IOValueDomainCodec)
    }

    fn demand_next<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<N> {
        self.next(read_annotations, decode_embedded)?.ok_or_else(io_eof)
    }

    fn next_boolean(&mut self) -> ReaderResult<bool> {
        self.next_iovalue(false)?.value().to_boolean()
    }

    fn next_float(&mut self) -> ReaderResult<Float> {
        Ok(self.next_iovalue(false)?.value().to_float()?.to_owned())
    }

    fn next_double(&mut self) -> ReaderResult<Double> {
        Ok(self.next_iovalue(false)?.value().to_double()?.to_owned())
    }

    fn next_signedinteger(&mut self) -> ReaderResult<SignedInteger> {
        Ok(self.next_iovalue(false)?.value().to_signedinteger()?.to_owned())
    }

    fn next_i8(&mut self) -> ReaderResult<i8> { self.next_iovalue(false)?.value().to_i8() }
    fn next_u8(&mut self) -> ReaderResult<u8> { self.next_iovalue(false)?.value().to_u8() }
    fn next_i16(&mut self) -> ReaderResult<i16> { self.next_iovalue(false)?.value().to_i16() }
    fn next_u16(&mut self) -> ReaderResult<u16> { self.next_iovalue(false)?.value().to_u16() }
    fn next_i32(&mut self) -> ReaderResult<i32> { self.next_iovalue(false)?.value().to_i32() }
    fn next_u32(&mut self) -> ReaderResult<u32> { self.next_iovalue(false)?.value().to_u32() }
    fn next_i64(&mut self) -> ReaderResult<i64> { self.next_iovalue(false)?.value().to_i64() }
    fn next_u64(&mut self) -> ReaderResult<u64> { self.next_iovalue(false)?.value().to_u64() }
    fn next_i128(&mut self) -> ReaderResult<i128> { self.next_iovalue(false)?.value().to_i128() }
    fn next_u128(&mut self) -> ReaderResult<u128> { self.next_iovalue(false)?.value().to_u128() }
    fn next_f32(&mut self) -> ReaderResult<f32> { self.next_iovalue(false)?.value().to_f32() }
    fn next_f64(&mut self) -> ReaderResult<f64> { self.next_iovalue(false)?.value().to_f64() }
    fn next_char(&mut self) -> ReaderResult<char> { self.next_iovalue(false)?.value().to_char() }

    fn next_str(&mut self) -> ReaderResult<Cow<'de, str>> {
        Ok(Cow::Owned(self.next_iovalue(false)?.value().to_string()?.to_owned()))
    }

    fn next_bytestring(&mut self) -> ReaderResult<Cow<'de, [u8]>> {
        Ok(Cow::Owned(self.next_iovalue(false)?.value().to_bytestring()?.to_owned()))
    }

    fn next_symbol(&mut self) -> ReaderResult<Cow<'de, str>> {
        Ok(Cow::Owned(self.next_iovalue(false)?.value().to_symbol()?.to_owned()))
    }

    fn open_simple_record(&mut self, name: &str) -> ReaderResult<()>
    {
        let b = self.open_record()?;
        let label: &str = &self.next_symbol()?;
        if label == name {
            Ok(b)
        } else {
            Err(error::Error::Expected(ExpectedKind::SimpleRecord(name.to_owned())))
        }
    }

    fn configured<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        self,
        read_annotations: bool,
        decode_embedded: Dec,
    ) -> ConfiguredReader<'de, N, Dec, Self>
    where
        Self: std::marker::Sized
    {
        ConfiguredReader {
            reader: self,
            read_annotations,
            decode_embedded,
            phantom: PhantomData,
        }
    }

    fn iovalues(self) -> ConfiguredReader<'de, IOValue, IOValueDomainCodec, Self>
        where Self: Sized
    {
        self.configured(true, IOValueDomainCodec)
    }

    fn ensure_more_expected(&mut self, b: &mut B::Type, i: &B::Item) -> ReaderResult<()> {
        if !self.close_compound(b, i)? {
            Ok(())
        } else {
            Err(error::Error::MissingItem)
        }
    }

    fn ensure_complete(&mut self, mut b: B::Type, i: &B::Item) -> ReaderResult<()> {
        if !self.close_compound(&mut b, i)? {
            Err(error::Error::MissingCloseDelimiter)
        } else {
            Ok(())
        }
    }
}

impl<'r, 'de, R: Reader<'de>> Reader<'de> for &'r mut R {
    fn next<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<Option<N>> {
        (*self).next(read_annotations, decode_embedded)
    }

    fn open_record(&mut self) -> ReaderResult<()> {
        (*self).open_record()
    }

    fn open_sequence(&mut self) -> ReaderResult<()> {
        (*self).open_sequence()
    }

    fn open_set(&mut self) -> ReaderResult<()> {
        (*self).open_set()
    }

    fn open_dictionary(&mut self) -> ReaderResult<()> {
        (*self).open_dictionary()
    }

    fn boundary(&mut self, b: &B::Type) -> ReaderResult<()> {
        (*self).boundary(b)
    }

    fn close_compound(&mut self, b: &mut B::Type, i: &B::Item) -> ReaderResult<bool> {
        (*self).close_compound(b, i)
    }

    fn open_embedded(&mut self) -> ReaderResult<()> {
        (*self).open_embedded()
    }

    fn close_embedded(&mut self) -> ReaderResult<()> {
        (*self).close_embedded()
    }

    type Mark = R::Mark;

    fn mark(&mut self) -> io::Result<Self::Mark> {
        (*self).mark()
    }

    fn restore(&mut self, mark: &Self::Mark) -> io::Result<()> {
        (*self).restore(mark)
    }

    fn next_token<N: NestedValue, Dec: DomainDecode<N::Embedded>>(
        &mut self,
        read_embedded_annotations: bool,
        decode_embedded: &mut Dec,
    ) -> io::Result<Token<N>> {
        (*self).next_token(read_embedded_annotations, decode_embedded)
    }
}

pub struct ConfiguredReader<'de, N: NestedValue, Dec: DomainDecode<N::Embedded>, R: Reader<'de>>
{
    pub reader: R,
    pub read_annotations: bool,
    pub decode_embedded: Dec,
    phantom: PhantomData<&'de N>,
}

impl<'de, N: NestedValue, Dec: DomainDecode<N::Embedded>, R: Reader<'de>>
    ConfiguredReader<'de, N, Dec, R>
{
    pub fn new(reader: R, decode_embedded: Dec) -> Self {
        reader.configured(true, decode_embedded)
    }

    pub fn set_read_annotations(&mut self, read_annotations: bool) {
        self.read_annotations = read_annotations;
    }

    pub fn demand_next(&mut self) -> io::Result<N> {
        self.reader.demand_next(self.read_annotations, &mut self.decode_embedded)
    }

    pub fn next_token(&mut self) -> io::Result<Token<N>> {
        self.reader.next_token(self.read_annotations, &mut self.decode_embedded)
    }
}

impl<'de, N: NestedValue, Dec: DomainDecode<N::Embedded>, R: Reader<'de>>
    std::iter::Iterator
    for ConfiguredReader<'de, N, Dec, R>
{
    type Item = io::Result<N>;
    fn next(&mut self) -> Option<Self::Item> {
        match self.reader.next(self.read_annotations, &mut self.decode_embedded) {
            Err(e) => Some(Err(e)),
            Ok(None) => None,
            Ok(Some(v)) => Some(Ok(v)),
        }
    }
}