reifydb-sub-flow 0.4.13

// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2025 ReifyDB

use std::sync::{Arc, LazyLock};

use reifydb_core::{
	interface::{
		catalog::flow::FlowNodeId,
		change::{Change, Diff},
	},
	value::column::{ColumnWithName, columns::Columns},
};
use reifydb_engine::{
	expression::{
		compile::{CompiledExpr, compile_expression},
		context::{CompileContext, EvalContext},
	},
	vm::stack::SymbolTable,
};
use reifydb_routine::routine::registry::Routines;
use reifydb_rql::expression::{Expression, name::display_label};
use reifydb_runtime::context::RuntimeContext;
use reifydb_type::{
	Result,
	fragment::Fragment,
	params::Params,
	value::{identity::IdentityId, row_number::RowNumber},
};

use crate::{Operator, operator::Operators, transaction::FlowTransaction};

// Static empty params instance for use in EvaluationContext
static EMPTY_PARAMS: Params = Params::None;
static EMPTY_SYMBOL_TABLE: LazyLock<SymbolTable> = LazyLock::new(SymbolTable::new);

pub struct MapOperator {
	parent: Arc<Operators>,
	node: FlowNodeId,
	expressions: Vec<Expression>,
	compiled_expressions: Vec<CompiledExpr>,
	routines: Routines,
	runtime_context: RuntimeContext,
}

impl MapOperator {
	pub fn new(
		parent: Arc<Operators>,
		node: FlowNodeId,
		expressions: Vec<Expression>,
		routines: Routines,
		runtime_context: RuntimeContext,
	) -> Self {
		let compile_ctx = CompileContext {
			symbols: &EMPTY_SYMBOL_TABLE,
		};
		let compiled_expressions: Vec<CompiledExpr> = expressions
			.iter()
			.map(|e| compile_expression(&compile_ctx, e))
			.collect::<Result<Vec<_>>>()
			.expect("Failed to compile expressions");

		Self {
			parent,
			node,
			expressions,
			compiled_expressions,
			routines,
			runtime_context,
		}
	}

	/// Project all rows in Columns using expressions
	fn project(&self, columns: &Columns) -> Result<Columns> {
		let row_count = columns.row_count();
		if row_count == 0 {
			return Ok(Columns::empty());
		}

		let session = EvalContext {
			params: &EMPTY_PARAMS,
			symbols: &EMPTY_SYMBOL_TABLE,
			routines: &self.routines,
			runtime_context: &self.runtime_context,
			arena: None,
			identity: IdentityId::root(),
			is_aggregate_context: false,
			columns: Columns::empty(),
			row_count: 1,
			target: None,
			take: None,
		};
		let exec_ctx = session.with_eval(columns.clone(), row_count);

		let mut result_columns = Vec::with_capacity(self.expressions.len());

		for (i, compiled_expr) in self.compiled_expressions.iter().enumerate() {
			let evaluated_col = compiled_expr.execute(&exec_ctx)?;

			let expr = &self.expressions[i];
			let field_name = display_label(expr).text().to_string();

			let named_column =
				ColumnWithName::new(Fragment::internal(field_name), evaluated_col.data().clone());

			result_columns.push(named_column);
		}

		let row_numbers = if columns.row_numbers.is_empty() {
			Vec::new()
		} else {
			columns.row_numbers.iter().cloned().collect()
		};

		Ok(Columns::with_system_columns(
			result_columns,
			row_numbers,
			columns.created_at.to_vec(),
			columns.updated_at.to_vec(),
		))
	}
}

impl Operator for MapOperator {
	fn id(&self) -> FlowNodeId {
		self.node
	}

	fn apply(&self, _txn: &mut FlowTransaction, change: Change) -> Result<Change> {
		let mut result = Vec::new();

		for diff in change.diffs.into_iter() {
			match diff {
				Diff::Insert {
					post,
				} => {
					let projected = match self.project(&post) {
						Ok(projected) => projected,
						Err(err) => {
							panic!("{:#?}", err)
						}
					};

					if !projected.is_empty() {
						result.push(Diff::insert(projected));
					}
				}
				Diff::Update {
					pre,
					post,
				} => {
					let projected_post = self.project(&post)?;
					let projected_pre = self.project(&pre)?;

					if !projected_post.is_empty() {
						result.push(Diff::update(projected_pre, projected_post));
					}
				}
				Diff::Remove {
					pre,
				} => {
					let projected_pre = self.project(&pre)?;
					if !projected_pre.is_empty() {
						result.push(Diff::remove(projected_pre));
					}
				}
			}
		}

		Ok(Change::from_flow(self.node, change.version, result, change.changed_at))
	}

	fn pull(&self, txn: &mut FlowTransaction, rows: &[RowNumber]) -> Result<Columns> {
		self.parent.pull(txn, rows)
	}
}