From 700d625c9385ef2aa007b595d645628358da172d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Renault?= <renault.cle@gmail.com>
Date: Sun, 2 Dec 2018 16:45:17 +0100
Subject: [PATCH] feat: Introduce the Database and DatabaseView

---
 src/database/mod.rs | 391 ++++++++++++++++++++++++++++++++++++++++++++
 src/index/schema.rs |   4 +
 src/lib.rs          |   1 +
 3 files changed, 396 insertions(+)
 create mode 100644 src/database/mod.rs

diff --git a/src/database/mod.rs b/src/database/mod.rs
new file mode 100644
index 000000000..961b98ab2
--- /dev/null
+++ b/src/database/mod.rs
@@ -0,0 +1,391 @@
+use std::io::{Cursor, Write};
+use std::{fmt, marker};
+use std::error::Error;
+use std::path::Path;
+
+use rocksdb::rocksdb::{DB, Snapshot, DBVector};
+use rocksdb::rocksdb_options::ReadOptions;
+use byteorder::{NetworkEndian, WriteBytesExt};
+use serde::de::{DeserializeOwned, Visitor};
+use serde::de::value::MapDeserializer;
+
+use crate::index::schema::{Schema, SchemaAttr};
+use crate::blob::positive::PositiveBlob;
+use crate::index::update::Update;
+use crate::DocumentId;
+
+const DATA_INDEX:  &[u8] = b"data-index";
+const DATA_SCHEMA: &[u8] = b"data-schema";
+
+const DOC_KEY_LEN:      usize = 4 + std::mem::size_of::<u64>();
+const DOC_KEY_ATTR_LEN: usize = DOC_KEY_LEN + 1 + std::mem::size_of::<u32>();
+
+// FIXME Do not panic!
+fn retrieve_data_schema(snapshot: &Snapshot<&DB>) -> Result<Schema, Box<Error>> {
+    match snapshot.get(DATA_SCHEMA)? {
+        Some(vector) => Ok(Schema::read_from(&*vector)?),
+        None => panic!("BUG: no schema found in the database"),
+    }
+}
+
+fn retrieve_data_index(snapshot: &Snapshot<&DB>) -> Result<PositiveBlob, Box<Error>> {
+    match snapshot.get(DATA_INDEX)? {
+        Some(vector) => Ok(bincode::deserialize(&*vector)?),
+        None => Ok(PositiveBlob::default()),
+    }
+}
+
+fn retrieve_document_attribute(
+    snapshot: &Snapshot<&DB>,
+    id: DocumentId,
+    attr: SchemaAttr
+) -> Result<Option<DBVector>, Box<Error>>
+{
+    let attribute_key = document_key_attr(id, attr);
+    Ok(snapshot.get(&attribute_key)?)
+}
+
+fn document_key(id: DocumentId) -> [u8; DOC_KEY_LEN] {
+    let mut key = [0; DOC_KEY_LEN];
+
+    let mut wtr = Cursor::new(&mut key[..]);
+    wtr.write_all(b"doc-").unwrap();
+    wtr.write_u64::<NetworkEndian>(id).unwrap();
+
+    key
+}
+
+fn document_key_attr(id: DocumentId, attr: SchemaAttr) -> [u8; DOC_KEY_ATTR_LEN] {
+    let mut key = [0; DOC_KEY_ATTR_LEN];
+    let raw_key = document_key(id);
+
+    let mut wtr = Cursor::new(&mut key[..]);
+    wtr.write_all(&raw_key).unwrap();
+    wtr.write_all(b"-").unwrap();
+    wtr.write_u32::<NetworkEndian>(attr.as_u32()).unwrap();
+
+    key
+}
+
+pub struct Database(DB);
+
+impl Database {
+    pub fn create(path: &Path) -> Result<Database, ()> {
+        unimplemented!()
+    }
+
+    pub fn open(path: &Path) -> Result<Database, ()> {
+        unimplemented!()
+    }
+
+    pub fn ingest_update_file(&self, update: Update) -> Result<(), ()> {
+        unimplemented!()
+    }
+
+    pub fn view(&self) -> Result<DatabaseView, Box<Error>> {
+        let snapshot = self.0.snapshot();
+        DatabaseView::new(snapshot)
+    }
+}
+
+pub struct DatabaseView<'a> {
+    snapshot: Snapshot<&'a DB>,
+    schema: Schema,
+}
+
+impl<'a> DatabaseView<'a> {
+    pub fn new(snapshot: Snapshot<&'a DB>) -> Result<DatabaseView, Box<Error>> {
+        let schema = retrieve_data_schema(&snapshot)?;
+        Ok(DatabaseView { snapshot, schema })
+    }
+
+    pub fn into_snapshot(self) -> Snapshot<&'a DB> {
+        self.snapshot
+    }
+
+    // TODO create an enum error type
+    pub fn retrieve_document<D>(&self, id: DocumentId) -> Result<D, Box<Error>>
+    where D: DeserializeOwned
+    {
+        let mut deserializer = Deserializer::new(&self.snapshot, &self.schema, id);
+        Ok(D::deserialize(&mut deserializer)?)
+    }
+
+    pub fn retrieve_documents<D, I>(&self, ids: I) -> DocumentIter<D, I::IntoIter>
+    where D: DeserializeOwned,
+          I: IntoIterator<Item=DocumentId>,
+    {
+        DocumentIter {
+            database_view: self,
+            document_ids: ids.into_iter(),
+            _phantom: marker::PhantomData,
+        }
+    }
+}
+
+// TODO impl ExactSizeIterator, DoubleEndedIterator
+pub struct DocumentIter<'a, D, I> {
+    database_view: &'a DatabaseView<'a>,
+    document_ids: I,
+    _phantom: marker::PhantomData<D>,
+}
+
+impl<'a, D, I> Iterator for DocumentIter<'a, D, I>
+where D: DeserializeOwned,
+      I: Iterator<Item=DocumentId>,
+{
+    type Item = Result<D, Box<Error>>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.document_ids.next() {
+            Some(id) => Some(self.database_view.retrieve_document(id)),
+            None => None
+        }
+    }
+}
+
+struct Deserializer<'a> {
+    snapshot: &'a Snapshot<&'a DB>,
+    schema: &'a Schema,
+    document_id: DocumentId,
+}
+
+impl<'a> Deserializer<'a> {
+    fn new(snapshot: &'a Snapshot<&DB>, schema: &'a Schema, doc: DocumentId) -> Self {
+        Deserializer { snapshot, schema, document_id: doc }
+    }
+}
+
+impl<'de, 'a, 'b> serde::de::Deserializer<'de> for &'b mut Deserializer<'a> {
+    type Error = DeserializerError;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_unit_struct<V>(
+        self,
+        name: &'static str,
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_newtype_struct<V>(
+        self,
+        name: &'static str,
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_tuple<V>(
+        self,
+        len: usize,
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_tuple_struct<V>(
+        self,
+        name: &'static str,
+        len: usize,
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_struct<V>(
+        self,
+        name: &'static str,
+        fields: &'static [&'static str],
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        let mut options = ReadOptions::new();
+        options.set_iterate_lower_bound(&document_key(self.document_id));
+        options.set_iterate_upper_bound(&document_key(self.document_id + 1));
+
+        let mut db_iter = self.snapshot.iter_opt(options);
+        let iter = db_iter.map(|(key, value)| ("hello", "ok"));
+
+        // Create the DocumentKey and DocumentKeyAttr types
+        // to help create and parse document keys attributes...
+        unimplemented!();
+
+        let map_deserializer = MapDeserializer::new(iter);
+        visitor.visit_map(map_deserializer)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &'static str,
+        variants: &'static [&'static str],
+        visitor: V
+    ) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>,
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+}
+
+#[derive(Debug)]
+struct DeserializerError;
+
+impl serde::de::Error for DeserializerError {
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        unimplemented!()
+    }
+}
+
+impl fmt::Display for DeserializerError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        unimplemented!()
+    }
+}
+
+impl Error for DeserializerError {}
diff --git a/src/index/schema.rs b/src/index/schema.rs
index 426b4df8d..286d48398 100644
--- a/src/index/schema.rs
+++ b/src/index/schema.rs
@@ -108,6 +108,10 @@ impl Schema {
     pub fn attribute<S: AsRef<str>>(&self, name: S) -> Option<SchemaAttr> {
         self.attrs.get(name.as_ref()).cloned()
     }
+
+    pub fn attribute_name(&self, attr: SchemaAttr) -> &str {
+        unimplemented!("cannot retrieve the attribute name by its attribute number")
+    }
 }
 
 #[derive(Debug, Copy, Clone, PartialOrd, Ord, PartialEq, Eq)]
diff --git a/src/lib.rs b/src/lib.rs
index 96a3f5d2f..9c8f84c8a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,7 @@
 
 pub mod automaton;
 pub mod blob;
+pub mod database;
 pub mod data;
 pub mod retrieve;
 pub mod index;