rjango 0.1.1

A full-stack Rust backend framework inspired by Django
Documentation 
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use super::base::DatabaseBackend;

#[derive(Debug, Default, Clone, Copy)]
pub struct PostgreSqlBackend;

#[must_use]
fn parse_optional_length(field_type: &str, base: &str) -> Option<Option<usize>> {
    let field_type = field_type.trim();
    if field_type == base {
        return Some(None);
    }

    let rest = field_type.strip_prefix(base)?;
    let length = rest.strip_prefix('(')?.strip_suffix(')')?.parse().ok()?;
    Some(Some(length))
}

#[must_use]
fn escape_identifier(name: &str) -> String {
    name.replace('"', "\"\"")
}

#[must_use]
fn escape_literal(value: &str) -> String {
    value.replace('\'', "''")
}

impl DatabaseBackend for PostgreSqlBackend {
    fn name(&self) -> &str {
        "postgresql"
    }

    fn quote_name(&self, name: &str) -> String {
        format!("\"{}\"", escape_identifier(name))
    }

    fn supports_covering_indexes(&self) -> bool {
        true
    }

    fn supports_expression_indexes(&self) -> bool {
        true
    }

    fn db_type(&self, field_type: &str) -> String {
        if let Some(length) = parse_optional_length(field_type, "CharField") {
            let length = length.unwrap_or(255);
            return format!("varchar({length})");
        }

        match field_type.trim() {
            "AutoField" => "serial".to_string(),
            "BigAutoField" => "bigserial".to_string(),
            "SmallAutoField" => "smallserial".to_string(),
            "IntegerField" | "PositiveIntegerField" | "PositiveSmallIntegerField" => {
                "integer".to_string()
            }
            "BigIntegerField" | "PositiveBigIntegerField" => "bigint".to_string(),
            "SmallIntegerField" => "smallint".to_string(),
            "BooleanField" | "NullBooleanField" => "boolean".to_string(),
            "FloatField" => "double precision".to_string(),
            "DateTimeField" => "timestamp with time zone".to_string(),
            "TextField" => "text".to_string(),
            "JSONField" => "jsonb".to_string(),
            "UUIDField" => "uuid".to_string(),
            "BinaryField" => "bytea".to_string(),
            other => other.to_string(),
        }
    }

    fn last_insert_id_sql(&self, table: &str, pk_name: &str) -> String {
        format!(
            "SELECT currval(pg_get_serial_sequence('{}', '{}'))",
            escape_literal(table),
            escape_literal(pk_name)
        )
    }
}

impl PostgreSqlBackend {
    #[must_use]
    pub fn supports_json(&self) -> bool {
        self.supports_json_field()
    }

    #[must_use]
    pub fn max_query_params(&self) -> usize {
        65_535
    }

    #[must_use]
    pub fn supports_returning(&self) -> bool {
        true
    }
}

#[cfg(test)]
mod tests {
    use super::{DatabaseBackend, PostgreSqlBackend};

    #[test]
    fn postgres_backend_reports_feature_flags() {
        let backend = PostgreSqlBackend;

        assert_eq!(backend.name(), "postgresql");
        assert!(backend.supports_transactions());
        assert!(backend.supports_json());
        assert_eq!(backend.max_query_params(), 65_535);
        assert!(backend.supports_returning());
        assert!(backend.supports_covering_indexes());
        assert!(backend.supports_expression_indexes());
    }

    #[test]
    fn test_postgresql_quote_name() {
        let backend = PostgreSqlBackend;

        assert_eq!(backend.quote_name("table_name"), "\"table_name\"");
        assert_eq!(backend.quote_name("table\"name"), "\"table\"\"name\"");
    }

    #[test]
    fn test_postgresql_db_type_mappings() {
        let backend = PostgreSqlBackend;

        assert_eq!(backend.db_type("AutoField"), "serial");
        assert_eq!(backend.db_type("BigAutoField"), "bigserial");
        assert_eq!(backend.db_type("CharField"), "varchar(255)");
        assert_eq!(backend.db_type("CharField(64)"), "varchar(64)");
        assert_eq!(backend.db_type("BooleanField"), "boolean");
        assert_eq!(backend.db_type("DateTimeField"), "timestamp with time zone");
        assert_eq!(backend.db_type("JSONField"), "jsonb");
        assert_eq!(backend.db_type("UUIDField"), "uuid");
        assert_eq!(backend.db_type("BinaryField"), "bytea");
    }

    #[test]
    fn test_postgresql_last_insert_id() {
        let backend = PostgreSqlBackend;

        assert_eq!(
            backend.last_insert_id_sql("widgets", "id"),
            "SELECT currval(pg_get_serial_sequence('widgets', 'id'))"
        );
    }
}