1 files changed, 138 insertions, 0 deletions
diff --git a/server/src/db_utils.rs b/server/src/db_utils.rs
new file mode 100644
index 0000000..e74fd68
--- /dev/null
+++ b/server/src/db_utils.rs
@@ -0,0 +1,138 @@
+#![allow(dead_code)]
+
+use sqlx::database::HasArguments;
+use sqlx::encode::Encode;
+use sqlx::types::Type;
+use sqlx::{Arguments, Database};
+use std::fmt::Display;
+
+pub struct UpdateBuilder<'args, DB>
+where
+    DB: Database,
+{
+    table: Option<String>,
+    names: Option<Vec<(String, String)>>,
+    where_: Option<Vec<(String, String, String)>>,
+    values: Option<<DB as HasArguments<'args>>::Arguments>,
+}
+
+impl<'args, DB: Database> UpdateBuilder<'args, DB>
+where
+    DB: Database,
+{
+    pub fn new() -> Self
+    where
+        <DB as HasArguments<'args>>::Arguments: Default,
+    {
+        UpdateBuilder {
+            table: None,
+            names: Some(Vec::new()),
+            where_: Some(Vec::new()),
+            values: Some(Default::default()),
+        }
+    }
+
+    #[inline]
+    fn sanity_check(&self) {
+        assert!(
+            self.values.is_some(),
+            "UpdateBuilder must be reset before reuse after `.build()`"
+        );
+    }
+
+    pub fn table(&mut self, table: impl Display) -> &mut Self {
+        self.sanity_check();
+
+        self.table = Some(format!("{table}"));
+
+        self
+    }
+
+    pub fn and_where<T>(&mut self, name: impl Display, op: impl Display, value: T) -> &mut Self
+    where
+        T: 'args + Encode<'args, DB> + Send + Type<DB>,
+    {
+        self.sanity_check();
+
+        let values = self.values.as_mut().expect("BUG: Values taken already");
+        values.add(value);
+
+        let mut placeholder = String::new();
+        values
+            .format_placeholder(&mut placeholder)
+            .expect("error in format_placeholder");
+
+        let where_ = self.where_.as_mut().expect("BUG: Where taken already");
+        where_.push((format!("{name}"), format!("{op}"), placeholder));
+
+        self
+    }
+
+    pub fn set<T>(&mut self, name: impl Display, value: T) -> &mut Self
+    where
+        T: 'args + Encode<'args, DB> + Send + Type<DB>,
+    {
+        self.sanity_check();
+
+        assert!(
+            self.where_.as_ref().unwrap().is_empty(),
+            "set must not be called after add_where"
+        );
+
+        let names = self.names.as_mut().expect("BUG: Names taken already");
+        let values = self.values.as_mut().expect("BUG: Values taken already");
+        values.add(value);
+
+        let mut placeholder = String::new();
+        values
+            .format_placeholder(&mut placeholder)
+            .expect("error in format_placeholder");
+        names.push((format!("{name}"), placeholder));
+
+        self
+    }
+
+    pub fn build(&mut self) -> (String, <DB as HasArguments<'args>>::Arguments) {
+        self.sanity_check();
+
+        let table = self.table.take().unwrap();
+        let mut query = format!("UPDATE {table} SET");
+        let mut first = true;
+        for (name, placeholder) in self.names.take().unwrap() {
+            if first {
+                first = false;
+            } else {
+                query.push(',');
+            }
+            query.push_str(&format!(" {name}={placeholder}"));
+        }
+
+        let where_ = self.where_.take().unwrap();
+        if !where_.is_empty() {
+            query.push_str(" WHERE");
+
+            first = true;
+            for (name, op, placeholder) in where_ {
+                if first {
+                    first = false;
+                } else {
+                    query.push_str(" AND");
+                }
+                query.push_str(&format!(" {name}{op}{placeholder}"));
+            }
+        }
+
+        // TODO: This method should return a Query, constructed by QueryBuilder, but I can't
+        // figure out how to create QueryBuilder::with_arguments in this generic method,
+        // where DB isn't "known".
+        (query, self.values.take().unwrap())
+    }
+
+    pub fn reset(&mut self) -> &mut Self {
+        self.names = Some(Vec::new());
+        self.where_ = Some(Vec::new());
+        self.values = Some(Default::default());
+
+        self
+    }
+}