// Copyright 2021 Datafuse Labs.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use std::sync::Arc;

use common_datavalues::DataValue;

use common_exception::ErrorCode;

use common_exception::Result;

use common_functions::is_builtin_function;

use common_planners::Expression;

use crate::sessions::QueryContext;

use crate::sessions::TableContext;

pub struct ContextFunction;

impl ContextFunction {

// Some function args need from context

// such as `SELECT database()`, the arg is ctx.get_default_db()

pub fn build_args_from_ctx(ctx: Arc<QueryContext>, name: &str) -> Result<Vec<Expression>> {

// Check the function is supported in common functions.

if !is_builtin_function(name) {

return Result::Err(ErrorCode::UnknownFunction(format!(

"Unsupported function: {:?}",

name

)));

}

Ok(match name.to_lowercase().as_str() {

"database" | "currentdatabase" | "current_database" => {

vec![Expression::create_literal(DataValue::String(

ctx.get_current_database().into_bytes(),

))]

}

"version" => vec![Expression::create_literal(DataValue::String(

ctx.get_fuse_version().into_bytes(),

))],

"user" | "currentuser" | "current_user" => vec![Expression::create_literal(

DataValue::String(ctx.get_current_user()?.identity().to_string().into_bytes()),

)],

"connection_id" => vec![Expression::create_literal(DataValue::String(

ctx.get_connection_id().into_bytes(),

))],

"timezone" => vec![Expression::create_literal(DataValue::String(

ctx.get_settings().get_timezone()?,

))],

_ => vec![],

})

}

}