245 lines
8.2 KiB
Rust
245 lines
8.2 KiB
Rust
// Copyright 2016 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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/// ! This module defines the interface and implementation for parsing an EDN
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/// ! input into a structured Datalog query.
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/// !
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/// ! The query types are defined in the `query` crate, because they
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/// ! are shared between the parser (EDN -> query), the translator
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/// ! (query -> SQL), and the executor (query, SQL -> running code).
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/// !
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/// ! The query input can be in two forms: a 'flat' human-oriented
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/// ! sequence:
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/// !
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/// ! ```clojure
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/// ! [:find ?y :in $ ?x :where [?x :foaf/knows ?y]]
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/// ! ```
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/// !
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/// ! or a more programmatically generable map:
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/// !
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/// ! ```clojure
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/// ! {:find [?y]
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/// ! :in [$]
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/// ! :where [[?x :foaf/knows ?y]]}
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/// ! ```
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/// !
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/// ! We parse by expanding the array format into four parts, treating them as the four
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/// ! parts of the map.
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extern crate edn;
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extern crate mentat_query;
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use std::collections::BTreeMap;
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use self::mentat_query::{
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FindQuery,
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FromValue,
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SrcVar,
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Variable,
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};
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use super::parse::{
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NotAVariableError,
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QueryParseError,
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QueryParseResult,
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clause_seq_to_patterns,
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};
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use super::util::vec_to_keyword_map;
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/// If the provided slice of EDN values are all variables as
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/// defined by `value_to_variable`, return a `Vec` of `Variable`s.
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/// Otherwise, return the unrecognized Value in a `NotAVariableError`.
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fn values_to_variables(vals: &[edn::Value]) -> Result<Vec<Variable>, NotAVariableError> {
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let mut out: Vec<Variable> = Vec::with_capacity(vals.len());
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for v in vals {
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if let Some(var) = Variable::from_value(v) {
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out.push(var);
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continue;
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}
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return Err(NotAVariableError(v.clone()));
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}
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return Ok(out);
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}
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#[allow(unused_variables)]
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fn parse_find_parts(find: &[edn::Value],
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ins: Option<&[edn::Value]>,
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with: Option<&[edn::Value]>,
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wheres: &[edn::Value])
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-> QueryParseResult {
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// :find must be an array of plain var symbols (?foo), pull expressions, and aggregates.
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// For now we only support variables and the annotations necessary to declare which
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// flavor of :find we want:
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// ?x ?y ?z = FindRel
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// [?x ...] = FindColl
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// ?x . = FindScalar
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// [?x ?y ?z] = FindTuple
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//
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// :in must be an array of sources ($), rules (%), and vars (?). For now we only support the
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// default source. :in can be omitted, in which case the default is equivalent to `:in $`.
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// TODO: process `ins`.
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let source = SrcVar::DefaultSrc;
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// :with is an array of variables. This is simple, so we don't use a parser.
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let with_vars = if let Some(vals) = with {
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values_to_variables(vals)?
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} else {
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vec![]
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};
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// :wheres is a whole datastructure.
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let where_clauses = clause_seq_to_patterns(wheres)?;
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super::parse::find_seq_to_find_spec(find)
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.map(|spec| {
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FindQuery {
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find_spec: spec,
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default_source: source,
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with: with_vars,
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in_vars: vec!(), // TODO
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in_sources: vec!(), // TODO
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where_clauses: where_clauses,
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}
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})
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.map_err(QueryParseError::FindParseError)
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}
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fn parse_find_map(map: BTreeMap<edn::Keyword, Vec<edn::Value>>) -> QueryParseResult {
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// Eagerly awaiting `const fn`.
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let kw_find = edn::Keyword::new("find");
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let kw_in = edn::Keyword::new("in");
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let kw_with = edn::Keyword::new("with");
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let kw_where = edn::Keyword::new("where");
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// Oh, if only we had `guard`.
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if let Some(find) = map.get(&kw_find) {
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if let Some(wheres) = map.get(&kw_where) {
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return parse_find_parts(find,
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map.get(&kw_in).map(|x| x.as_slice()),
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map.get(&kw_with).map(|x| x.as_slice()),
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wheres);
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} else {
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return Err(QueryParseError::MissingField(kw_where));
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}
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} else {
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return Err(QueryParseError::MissingField(kw_find));
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}
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}
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fn parse_find_edn_map(map: BTreeMap<edn::Value, edn::Value>) -> QueryParseResult {
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// Every key must be a Keyword. Every value must be a Vec.
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let mut m = BTreeMap::new();
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if map.is_empty() {
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return parse_find_map(m);
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}
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for (k, v) in map {
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if let edn::Value::Keyword(kw) = k {
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if let edn::Value::Vector(vec) = v {
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m.insert(kw, vec);
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continue;
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} else {
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return Err(QueryParseError::InvalidInput(v));
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}
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} else {
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return Err(QueryParseError::InvalidInput(k));
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}
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}
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parse_find_map(m)
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}
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impl From<edn::parse::ParseError> for QueryParseError {
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fn from(err: edn::parse::ParseError) -> QueryParseError {
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QueryParseError::EdnParseError(err)
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}
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}
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pub fn parse_find_string(string: &str) -> QueryParseResult {
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let expr = edn::parse::value(string)?;
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parse_find(expr.without_spans())
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}
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pub fn parse_find(expr: edn::Value) -> QueryParseResult {
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// No `match` because scoping and use of `expr` in error handling is nuts.
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if let edn::Value::Map(m) = expr {
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return parse_find_edn_map(m);
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}
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if let edn::Value::Vector(ref v) = expr {
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if let Some(m) = vec_to_keyword_map(v) {
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return parse_find_map(m);
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}
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}
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return Err(QueryParseError::InvalidInput(expr));
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}
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#[cfg(test)]
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mod test_parse {
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extern crate edn;
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use self::edn::{NamespacedKeyword, PlainSymbol};
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use self::edn::types::Value;
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use super::mentat_query::{
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Element,
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FindSpec,
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Pattern,
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PatternNonValuePlace,
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PatternValuePlace,
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SrcVar,
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Variable,
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WhereClause,
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};
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use super::*;
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// TODO: when #224 lands, fix to_keyword to be variadic.
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#[test]
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fn test_parse_find() {
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let truncated_input = edn::Value::Vector(vec![Value::from_keyword(None, "find")]);
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assert!(parse_find(truncated_input).is_err());
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let input = edn::Value::Vector(vec![
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Value::from_keyword(None, "find"),
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Value::from_symbol(None, "?x"),
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Value::from_symbol(None, "?y"),
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Value::from_keyword(None, "where"),
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edn::Value::Vector(vec![
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Value::from_symbol(None, "?x"),
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Value::from_keyword("foo", "bar"),
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Value::from_symbol(None, "?y"),
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]),
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]);
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let parsed = parse_find(input).unwrap();
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if let FindSpec::FindRel(elems) = parsed.find_spec {
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assert_eq!(2, elems.len());
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assert_eq!(vec![
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Element::Variable(Variable(edn::PlainSymbol::new("?x"))),
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Element::Variable(Variable(edn::PlainSymbol::new("?y"))),
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], elems);
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} else {
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panic!("Expected FindRel.");
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}
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assert_eq!(SrcVar::DefaultSrc, parsed.default_source);
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assert_eq!(parsed.where_clauses,
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vec![
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WhereClause::Pattern(Pattern {
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source: None,
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entity: PatternNonValuePlace::Variable(Variable(PlainSymbol::new("?x"))),
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attribute: PatternNonValuePlace::Ident(NamespacedKeyword::new("foo", "bar")),
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value: PatternValuePlace::Variable(Variable(PlainSymbol::new("?y"))),
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tx: PatternNonValuePlace::Placeholder,
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})]);
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}
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}
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