start implementing a skeleton of the v1 dump reader

dump/src/reader/v1/settings.rs

@@ -0,0 +1,63 @@
+use std::collections::{BTreeMap, BTreeSet};
+use std::result::Result as StdResult;
+
+use serde::{Deserialize, Deserializer, Serialize};
+
+#[derive(Default, Clone, Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase", deny_unknown_fields)]
+pub struct Settings {
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub ranking_rules: Option<Option<Vec<String>>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub distinct_attribute: Option<Option<String>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub searchable_attributes: Option<Option<Vec<String>>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub displayed_attributes: Option<Option<BTreeSet<String>>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub stop_words: Option<Option<BTreeSet<String>>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub synonyms: Option<Option<BTreeMap<String, Vec<String>>>>,
+    #[serde(default, deserialize_with = "deserialize_some")]
+    pub attributes_for_faceting: Option<Option<Vec<String>>>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SettingsUpdate {
+    pub ranking_rules: UpdateState<Vec<RankingRule>>,
+    pub distinct_attribute: UpdateState<String>,
+    pub primary_key: UpdateState<String>,
+    pub searchable_attributes: UpdateState<Vec<String>>,
+    pub displayed_attributes: UpdateState<BTreeSet<String>>,
+    pub stop_words: UpdateState<BTreeSet<String>>,
+    pub synonyms: UpdateState<BTreeMap<String, Vec<String>>>,
+    pub attributes_for_faceting: UpdateState<Vec<String>>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum UpdateState<T> {
+    Update(T),
+    Clear,
+    Nothing,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum RankingRule {
+    Typo,
+    Words,
+    Proximity,
+    Attribute,
+    WordsPosition,
+    Exactness,
+    Asc(String),
+    Desc(String),
+}
+
+// Any value that is present is considered Some value, including null.
+fn deserialize_some<'de, T, D>(deserializer: D) -> StdResult<Option<T>, D::Error>
+where
+    T: Deserialize<'de>,
+    D: Deserializer<'de>,
+{
+    Deserialize::deserialize(deserializer).map(Some)
+}