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use {
	super::join::JoinManual,
	crate::{
		executor::{
			types::{Alias, ObjectName},
			MetaRecipe,
		},
		Context, Result,
	},
	serde::Serialize,
	sqlparser::ast::{Expr, Ident, Select, SelectItem as SelectItemAst},
	std::fmt::Debug,
	thiserror::Error as ThisError,
};

#[derive(ThisError, Serialize, Debug, PartialEq)]
pub enum ManualError {
	#[error("subqueries are not yet supported")]
	UnimplementedSubquery,

	#[error("this should be impossible, please report")]
	UncaughtASTError(String),

	#[error("this should be impossible, please report")]
	Unreachable,
}

pub struct Manual {
	pub joins: Vec<JoinManual>,
	pub select_items: Vec<SelectItem>,
	pub constraint: MetaRecipe,
	pub group_constraint: MetaRecipe,
	pub groups: Vec<MetaRecipe>,
}
pub enum SelectItem {
	Recipe(MetaRecipe, Alias),
	Wildcard(Option<ObjectName>),
}

impl Manual {
	pub fn new(select: Select, context: &Context) -> Result<Self> {
		let Select {
			projection,
			from,
			selection,
			group_by,
			having,
			// TODO (below)
			distinct: _,
			top: _,
			lateral_views: _,
			cluster_by: _,
			distribute_by: _,
			sort_by: _,
			into: _,
		} = select;

		let constraint = selection
			.map(|selection| MetaRecipe::new(selection)?.simplify_by_context(context))
			.unwrap_or(Ok(MetaRecipe::TRUE))?;

		let group_constraint = having
			.map(|having| MetaRecipe::new(having)?.simplify_by_context(context))
			.unwrap_or(Ok(MetaRecipe::TRUE))?;

		let groups = group_by
			.into_iter()
			.map(|expression| MetaRecipe::new(expression)?.simplify_by_context(context))
			.collect::<Result<Vec<MetaRecipe>>>()?;

		let (select_items, _subqueries): (Vec<SelectItem>, Vec<Vec<JoinManual>>) = projection
			.into_iter()
			.map(|select_item| convert_select_item(select_item, context))
			.collect::<Result<Vec<(SelectItem, Vec<JoinManual>)>>>()?
			.into_iter()
			.unzip();

		/*subqueries.push(constraint.meta.subqueries.clone());

		let subqueries = subqueries
			.into_iter()
			.reduce(|mut all_subqueries, subqueries| {
				all_subqueries.extend(subqueries);
				all_subqueries
			})
			.ok_or(ManualError::UncaughtASTError(String::from(
				"Supposedly subqueries yet none found",
			)))?;
		// Subqueries TODO
		// Issues:
		// - Current method can expand plane on multiple match
		// - No plane isolation (ambiguous columns because subquery columns and plane columns are treated the same)
		if !subqueries.is_empty() {
			return Err(ManualError::UnimplementedSubquery.into());
		}*/

		let /*mut*/ joins = from
            .into_iter()
            .map(|from| {
                let main = JoinManual::new_implicit_join(from.relation)?;
                let mut joins = from
                    .joins
                    .into_iter()
                    .map(|join| JoinManual::new(join, context))
                    .collect::<Result<Vec<JoinManual>>>()?;
                joins.push(main);
                Ok(joins)
            })
            .collect::<Result<Vec<Vec<JoinManual>>>>()?
            .into_iter()
            .reduce(|mut all_joins, joins| {
                all_joins.extend(joins);
                all_joins
            })
            .ok_or_else(||ManualError::UncaughtASTError(String::from("No tables")))?;
		//joins.extend(subqueries);
		//let joins = joins;

		Ok(Manual {
			joins,
			select_items,
			constraint,
			group_constraint,
			groups,
		})
	}
}

fn identifier_into_object_name(identifier: Vec<Ident>) -> ObjectName {
	identifier
		.into_iter()
		.map(|identifier| identifier.value)
		.collect()
}

fn convert_select_item(
	select_item: SelectItemAst,
	context: &Context,
) -> Result<(SelectItem, Vec<JoinManual>)> {
	Ok(match select_item {
		SelectItemAst::UnnamedExpr(_) | SelectItemAst::ExprWithAlias { .. } => {
			let (expression, alias) = match select_item {
				SelectItemAst::UnnamedExpr(expression) => {
					let alias = if let Expr::Identifier(identifier) = expression.clone() {
						Some(identifier.value)
					} else {
						None
					};
					(expression, alias)
				}
				SelectItemAst::ExprWithAlias { expr, alias } => (expr, Some(alias.value)),
				_ => unreachable!(),
			};
			let recipe = MetaRecipe::new(expression)?.simplify_by_context(context)?;
			let subqueries = recipe.meta.subqueries.clone();
			(SelectItem::Recipe(recipe, alias), subqueries)
		}
		SelectItemAst::Wildcard => (SelectItem::Wildcard(None), vec![]),
		SelectItemAst::QualifiedWildcard(qualifier) => (
			SelectItem::Wildcard(Some(identifier_into_object_name(qualifier.0))),
			vec![],
		),
	})
}