boatramp-server 0.2.9

//! SQL dialect differences the compiler must respect: identifier quoting and bind
//! placeholders. Identifiers always come from the introspected + exposed schema (never
//! request text), so quoting is about correctness (reserved words), not safety; values are
//! always bound parameters. The default managed backend is libsql (SQLite); Postgres/MySQL
//! dialects arrive with bring-your-own introspection.

/// The SQL syntax knobs the compiler varies by backend. `Send + Sync` so a `&dyn Dialect`
/// can be held across the runner's `await` points.
pub(crate) trait Dialect: Send + Sync {
    /// Quote a schema identifier (table/column) for this dialect.
    fn quote_ident(&self, ident: &str) -> String;

    /// The bind placeholder for the 1-based parameter `index` (some dialects number them,
    /// some don't).
    fn placeholder(&self, index: usize) -> String;

    /// A JSON object expression from `(key, value_expr)` pairs — the relationship subquery's
    /// per-row shape. Keys are GraphQL field names (safe), emitted as SQL string literals.
    fn json_object(&self, pairs: &[(String, String)]) -> String;

    /// Aggregate a per-row object expression into a JSON array (the to-many shape).
    fn json_array_agg(&self, element: &str) -> String;
}

/// A SQL single-quoted string literal (`'…'`), doubling any embedded quote.
pub(crate) fn sql_string_literal(s: &str) -> String {
    format!("'{}'", s.replace('\'', "''"))
}

/// SQLite / libsql — the managed default. `"ident"` quoting, **numbered** `?N` placeholders
/// (the libsql backend requires `?1`, `?2`, … and rejects a bare `?`).
pub(crate) struct Sqlite;

impl Dialect for Sqlite {
    fn quote_ident(&self, ident: &str) -> String {
        format!("\"{}\"", ident.replace('"', "\"\""))
    }

    fn placeholder(&self, index: usize) -> String {
        format!("?{index}")
    }

    fn json_object(&self, pairs: &[(String, String)]) -> String {
        let args = pairs
            .iter()
            .map(|(key, value)| format!("{}, {value}", sql_string_literal(key)))
            .collect::<Vec<_>>()
            .join(", ");
        format!("json_object({args})")
    }

    fn json_array_agg(&self, element: &str) -> String {
        // SQLite marks json_object results with the JSON subtype, so json_group_array nests
        // them as objects rather than quoting them.
        format!("json_group_array({element})")
    }
}