75 lines
2.5 KiB
Rust
75 lines
2.5 KiB
Rust
//! Implements the Preserves
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//! [merge](https://preserves.dev/preserves.html#appendix-merging-values) of values.
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use super::Map;
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use super::NestedValue;
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use super::Record;
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use super::Value;
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/// Merge two sequences of values according to [the
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/// specification](https://preserves.dev/preserves.html#appendix-merging-values).
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pub fn merge_seqs<N: NestedValue>(mut a: Vec<N>, mut b: Vec<N>) -> Option<Vec<N>> {
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if a.len() > b.len() {
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std::mem::swap(&mut a, &mut b);
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}
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let mut r = vec![];
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let mut bi = b.into_iter();
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for av in a.into_iter() {
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r.push(merge2(av, bi.next().unwrap())?);
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}
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r.extend(bi);
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Some(r)
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}
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/// Merge two values according to [the
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/// specification](https://preserves.dev/preserves.html#appendix-merging-values).
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pub fn merge2<N: NestedValue>(v: N, w: N) -> Option<N> {
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let (mut v_anns, v_val) = v.pieces();
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let (w_anns, w_val) = w.pieces();
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v_anns.modify(|anns| anns.extend(w_anns.to_vec().into_iter()));
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if v_val == w_val {
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Some(N::wrap(v_anns, v_val))
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} else {
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let maybe_merged = match v_val {
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Value::Record(rv) => Some(Value::Record(Record(merge_seqs(
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rv.0,
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w_val.into_record()?.0,
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)?))),
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Value::Sequence(vs) => Some(Value::Sequence(merge_seqs(vs, w_val.into_sequence()?)?)),
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Value::Set(_vs) => None, // unsure how to merge sets
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Value::Dictionary(vs) => {
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let mut ws = w_val.into_dictionary()?;
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let mut rs = Map::new();
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for (k, vv) in vs.into_iter() {
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match ws.remove(&k) {
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Some(wv) => {
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rs.insert(k, merge2(vv, wv)?);
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}
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None => {
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rs.insert(k, vv);
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}
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}
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}
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rs.extend(ws.into_iter());
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Some(Value::Dictionary(rs))
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}
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_ => None,
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};
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maybe_merged.map(|vw| N::wrap(v_anns, vw))
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}
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}
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/// Merge several values into a single value according to [the
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/// specification](https://preserves.dev/preserves.html#appendix-merging-values).
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pub fn merge<N: NestedValue, I: IntoIterator<Item = N>>(vs: I) -> Option<N> {
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let mut vs = vs.into_iter();
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let mut v = vs.next().expect("at least one value in merge()");
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for w in vs {
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match merge2(v, w) {
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Some(merged) => v = merged,
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None => return None,
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}
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}
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Some(v)
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}
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