From e042f44e0d2020cdd56ee6e4c3a065bf11fa7bc3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Renault?= <renault.cle@gmail.com>
Date: Tue, 21 May 2019 16:15:31 +0200
Subject: [PATCH] feat: Reintroduce the `SortByAttr` custom criterion

---
 meilidb/Cargo.toml          |   2 +-
 meilidb/src/lib.rs          |   3 +
 meilidb/src/sort_by_attr.rs | 125 ++++++++++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 meilidb/src/lib.rs
 create mode 100644 meilidb/src/sort_by_attr.rs

diff --git a/meilidb/Cargo.toml b/meilidb/Cargo.toml
index 8f9517419..e34ccc0eb 100644
--- a/meilidb/Cargo.toml
+++ b/meilidb/Cargo.toml
@@ -5,6 +5,7 @@ version = "0.3.1"
 authors = ["Kerollmops <renault.cle@gmail.com>"]
 
 [dependencies]
+meilidb-core = { path = "../meilidb-core", version = "0.1.0" }
 meilidb-data = { path = "../meilidb-data", version = "0.1.0" }
 serde = { version = "1.0.91" , features = ["derive"] }
 serde_json = "1.0.39"
@@ -12,7 +13,6 @@ tempfile = "3.0.7"
 tide = "0.2.0"
 
 [dev-dependencies]
-meilidb-core = { path = "../meilidb-core", version = "0.1.0" }
 csv = "1.0.7"
 env_logger = "0.6.1"
 jemallocator = "0.1.9"
diff --git a/meilidb/src/lib.rs b/meilidb/src/lib.rs
new file mode 100644
index 000000000..89ed6b07e
--- /dev/null
+++ b/meilidb/src/lib.rs
@@ -0,0 +1,3 @@
+mod sort_by_attr;
+
+pub use self::sort_by_attr::SortByAttr;
diff --git a/meilidb/src/sort_by_attr.rs b/meilidb/src/sort_by_attr.rs
new file mode 100644
index 000000000..6a630bedf
--- /dev/null
+++ b/meilidb/src/sort_by_attr.rs
@@ -0,0 +1,125 @@
+use std::cmp::Ordering;
+use std::error::Error;
+use std::fmt;
+
+use meilidb_core::criterion::Criterion;
+use meilidb_core::RawDocument;
+use meilidb_data::{Schema, SchemaAttr, RankedMap};
+
+/// An helper struct that permit to sort documents by
+/// some of their stored attributes.
+///
+/// # Note
+///
+/// If a document cannot be deserialized it will be considered [`None`][].
+///
+/// Deserialized documents are compared like `Some(doc0).cmp(&Some(doc1))`,
+/// so you must check the [`Ord`] of `Option` implementation.
+///
+/// [`None`]: https://doc.rust-lang.org/std/option/enum.Option.html#variant.None
+/// [`Ord`]: https://doc.rust-lang.org/std/option/enum.Option.html#impl-Ord
+///
+/// # Example
+///
+/// ```ignore
+/// use serde_derive::Deserialize;
+/// use meilidb::rank::criterion::*;
+///
+/// let custom_ranking = SortByAttr::lower_is_better(&ranked_map, &schema, "published_at")?;
+///
+/// let builder = CriteriaBuilder::with_capacity(8)
+///        .add(SumOfTypos)
+///        .add(NumberOfWords)
+///        .add(WordsProximity)
+///        .add(SumOfWordsAttribute)
+///        .add(SumOfWordsPosition)
+///        .add(Exact)
+///        .add(custom_ranking)
+///        .add(DocumentId);
+///
+/// let criterion = builder.build();
+///
+/// ```
+pub struct SortByAttr<'a> {
+    ranked_map: &'a RankedMap,
+    attr: SchemaAttr,
+    reversed: bool,
+}
+
+impl<'a> SortByAttr<'a> {
+    pub fn lower_is_better(
+        ranked_map: &'a RankedMap,
+        schema: &Schema,
+        attr_name: &str,
+    ) -> Result<SortByAttr<'a>, SortByAttrError>
+    {
+        SortByAttr::new(ranked_map, schema, attr_name, false)
+    }
+
+    pub fn higher_is_better(
+        ranked_map: &'a RankedMap,
+        schema: &Schema,
+        attr_name: &str,
+    ) -> Result<SortByAttr<'a>, SortByAttrError>
+    {
+        SortByAttr::new(ranked_map, schema, attr_name, true)
+    }
+
+    fn new(
+        ranked_map: &'a RankedMap,
+        schema: &Schema,
+        attr_name: &str,
+        reversed: bool,
+    ) -> Result<SortByAttr<'a>, SortByAttrError>
+    {
+        let attr = match schema.attribute(attr_name) {
+            Some(attr) => attr,
+            None => return Err(SortByAttrError::AttributeNotFound),
+        };
+
+        if !schema.props(attr).is_ranked() {
+            return Err(SortByAttrError::AttributeNotRegisteredForRanking);
+        }
+
+        Ok(SortByAttr { ranked_map, attr, reversed })
+    }
+}
+
+impl<'a> Criterion for SortByAttr<'a> {
+    fn evaluate(&self, lhs: &RawDocument, rhs: &RawDocument) -> Ordering {
+        let lhs = self.ranked_map.get(lhs.id, self.attr);
+        let rhs = self.ranked_map.get(rhs.id, self.attr);
+
+        match (lhs, rhs) {
+            (Some(lhs), Some(rhs)) => {
+                let order = lhs.cmp(&rhs);
+                if self.reversed { order.reverse() } else { order }
+            },
+            (None,    Some(_)) => Ordering::Greater,
+            (Some(_), None)    => Ordering::Less,
+            (None,    None)    => Ordering::Equal,
+        }
+    }
+
+    fn name(&self) -> &'static str {
+        "SortByAttr"
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum SortByAttrError {
+    AttributeNotFound,
+    AttributeNotRegisteredForRanking,
+}
+
+impl fmt::Display for SortByAttrError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use SortByAttrError::*;
+        match self {
+            AttributeNotFound => f.write_str("attribute not found in the schema"),
+            AttributeNotRegisteredForRanking => f.write_str("attribute not registered for ranking"),
+        }
+    }
+}
+
+impl Error for SortByAttrError { }