rtlola_parser/

syntactic_sugar.rs

use std::collections::HashSet;
use std::hash::Hash;
use std::rc::Rc;

// List for all syntactic sugar transformer
mod aggregation_method;
mod builder;
mod delta;
mod implication;
mod last;
mod mirror;
mod next_id;
mod offset_or;
mod probability;
mod probability_aggregation;
mod true_ratio;
use aggregation_method::AggrMethodToWindow;
use delta::Delta;
use itertools::Itertools;
use last::Last;
use mirror::Mirror as SynSugMirror;
use probability::Probability;
use probability_aggregation::ProbabilityAggregation;
use rtlola_reporting::RtLolaError;
use true_ratio::TrueRatio;

use self::implication::Implication;
use self::offset_or::OffsetOr;
use crate::ast::{
    CloseSpec, EvalSpec, Expression, ExpressionKind, Input, InstanceSelection, LambdaExpr,
    Mirror as AstMirror, NodeId, Output, RtLolaAst, SpawnSpec,
};

#[derive(Debug, Clone, Eq, PartialEq, Hash, PartialOrd, Ord)]
enum ChangeInstruction {
    #[allow(dead_code)] // currently unused
    ReplaceExpr(NodeId, Expression),
    RemoveStream(NodeId),
    AddOutput(Box<Output>),
}
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
enum LocalChangeInstruction {
    ReplaceExpr(Expression),
}

/// The ChangeSet collects change instructions for syntactic sugar removal.
///
/// Desugarization could replace the current expression or add global changes, like outsource to new streams.
/// Adding change sets collects all global changes and allows at most one local change to be present.
#[derive(Debug, Clone)]
struct ChangeSet {
    _local_applied_flag: bool,
    local_instructions: Option<LocalChangeInstruction>,
    global_instructions: HashSet<ChangeInstruction>,
}

#[derive(Clone, Copy, Debug)]
enum ExprOrigin {
    SpawnWhen,
    SpawnWith,
    #[allow(dead_code)]
    EvalWhen(usize),
    EvalWith(usize),
    CloseWhen,
}

/// Syntactic Sugar has to implement this trait and override methods if needed.
///
/// The transformer gets every single expression passed once, in an bottom up order. Afterwards every top level stream object is passed once.
/// The [ChangeSet] can hold a single local change, a change that immediately has to be applied to the expression passed in [SynSugar::desugarize_expr],
/// and an arbitrary number of changes that will be applied after an iteration, which is identified by the [NodeId] of the object it wants to replace.
#[allow(unused_variables)] // allow unused arguments in the default implementation without changing the name
trait SynSugar {
    /// Desugars a single expression.  Provided [RtLolaAst] and [Expression] are for reference, not modification.
    ///
    /// # Requirements
    /// * Ids may NEVER be re-used.  Always generate new ones with ast.next_id() or increase the prime-counter of an existing [NodeId].
    /// * When creating new nodes with a span, do not re-use the span of the old node.  Instead, create an indirect span refering to the old one.
    fn desugarize_expr<'a>(
        &self,
        exp: &'a Expression,
        ast: &'a RtLolaAst,
        stream: usize,
        origin: ExprOrigin,
    ) -> Result<ChangeSet, RtLolaError> {
        Ok(ChangeSet::empty())
    }

    /// Desugars a single output stream.  Provided [RtLolaAst] and [Output] are for reference, not modification.
    ///
    /// # Requirements
    /// * Ids may NEVER be re-used.  Always generate new ones with ast.next_id() or increase the prime-counter of an existing [NodeId].
    /// * When creating new nodes with a span, do not re-use the span of the old node.  Instead, create an indirect span refering to the old one.
    fn desugarize_stream_out<'a>(
        &self,
        stream: &'a Output,
        ast: &'a RtLolaAst,
    ) -> Result<ChangeSet, RtLolaError> {
        Ok(ChangeSet::empty())
    }
    /// Desugars a single input stream.  Provided [RtLolaAst] and [Input] are for reference, not modification.
    ///
    /// # Requirements
    /// * Ids may NEVER be re-used.  Always generate new ones with ast.next_id() or increase the prime-counter of an existing [NodeId].
    /// * When creating new nodes with a span, do not re-use the span of the old node.  Instead, create an indirect span refering to the old one.
    fn desugarize_stream_in<'a>(
        &self,
        stream: &'a Input,
        ast: &'a RtLolaAst,
    ) -> Result<ChangeSet, RtLolaError> {
        Ok(ChangeSet::empty())
    }
    /// Desugars a single mirror stream.  Provided [RtLolaAst] and [AstMirror] are for reference, not modification.
    ///
    /// # Requirements
    /// * Ids may NEVER be re-used.  Always generate new ones with ast.next_id() or increase the prime-counter of an existing [NodeId].
    /// * When creating new nodes with a span, do not re-use the span of the old node.  Instead, create an indirect span refering to the old one.
    fn desugarize_stream_mirror<'a>(
        &self,
        stream: &'a AstMirror,
        ast: &'a RtLolaAst,
    ) -> Result<ChangeSet, RtLolaError> {
        Ok(ChangeSet::empty())
    }
}

/// The container for all syntactic sugar structs.
///
/// Contains the logic on how and when to remove syntactic sugar changes.
/// A transformer just needs to implement the SynSugar trait and be registered in the internal vector, constructed in [Desugarizer::all].
#[allow(missing_debug_implementations)] // Contains no relevant fields, only logic. Trait object vectors are hard to print.
pub struct Desugarizer {
    sugar_transformers: Vec<Box<dyn SynSugar>>,
}

impl Desugarizer {
    /// Constructs a Desugarizer with all registered SynSugar transformations.
    ///
    /// All transformations registered in the internal vector will be applied on the ast.
    /// New structs have to be added in this function.
    pub fn all() -> Self {
        let all_transformers: Vec<Box<dyn SynSugar>> = vec![
            Box::new(Implication {}),
            Box::new(AggrMethodToWindow {}),
            Box::new(Last {}),
            Box::new(SynSugMirror {}),
            Box::new(Delta {}),
            Box::new(OffsetOr {}),
            Box::new(TrueRatio {}),
            Box::new(Probability {}),
            Box::new(ProbabilityAggregation {}),
        ];
        Self {
            sugar_transformers: all_transformers,
        }
    }

    /// Before calling this, all others Rcs on Ast nodes MUST be dropped.
    ///
    /// # panics
    /// If an Rc has a strong count greater than one.
    pub fn remove_syn_sugar(&self, mut ast: RtLolaAst) -> Result<RtLolaAst, RtLolaError> {
        while {
            // magic rust do-while loop
            let (new_ast, change_flag) = self.desugarize_fix_point(ast)?;
            ast = new_ast;
            change_flag
        } {} // do not remove! magic rust do-while loop
        Ok(ast)
    }

    fn desugarize_fix_point(&self, mut ast: RtLolaAst) -> Result<(RtLolaAst, bool), RtLolaError> {
        let mut change_flag = false;
        for current_sugar in self.sugar_transformers.iter() {
            let mut change_set = ChangeSet::empty();

            for mirror in ast.mirrors.iter() {
                change_set += self.desugarize_mirror(mirror, &ast, current_sugar)?;
            }

            for ix in 0..ast.outputs.len() {
                let out = &ast.outputs[ix];
                let out_clone: Output = Output::clone(out);
                let Output {
                    spawn, eval, close, ..
                } = out_clone;
                let new_spawn_spec = if let Some(spawn_spec) = spawn {
                    let SpawnSpec {
                        expression,
                        condition,
                        annotated_pacing,
                        id,
                        span,
                    } = spawn_spec;
                    let expression = expression
                        .map(|expr| {
                            let (new_expr, spawn_cs) = Self::desugarize_expression(
                                expr,
                                &ast,
                                current_sugar,
                                ix,
                                ExprOrigin::SpawnWith,
                            )?;
                            change_set += spawn_cs;
                            Ok::<_, RtLolaError>(new_expr)
                        })
                        .transpose()?;
                    let condition = condition
                        .map(|expr| {
                            let (new_expr, spawn_cond_cs) = Self::desugarize_expression(
                                expr,
                                &ast,
                                current_sugar,
                                ix,
                                ExprOrigin::SpawnWhen,
                            )?;
                            change_set += spawn_cond_cs;
                            Ok::<_, RtLolaError>(new_expr)
                        })
                        .transpose()?;
                    Some(SpawnSpec {
                        expression,
                        condition,
                        annotated_pacing,
                        id,
                        span,
                    })
                } else {
                    None
                };

                let transformed_eval = eval
                    .into_iter()
                    .enumerate()
                    .map(|(i, eval_spec)| {
                        let EvalSpec {
                            annotated_pacing,
                            condition,
                            eval_expression,
                            id,
                            span,
                        } = eval_spec;
                        let new_eval = eval_expression
                            .map(|e| {
                                let (res, eval_cs) = Self::desugarize_expression(
                                    e,
                                    &ast,
                                    current_sugar,
                                    ix,
                                    ExprOrigin::EvalWith(i),
                                )?;
                                change_set += eval_cs;
                                Ok::<_, RtLolaError>(res)
                            })
                            .transpose()?;
                        let new_condition = condition
                            .map(|e| {
                                let (res, cond_cs) = Self::desugarize_expression(
                                    e,
                                    &ast,
                                    current_sugar,
                                    ix,
                                    ExprOrigin::EvalWhen(i),
                                )?;
                                change_set += cond_cs;
                                Ok::<_, RtLolaError>(res)
                            })
                            .transpose()?;
                        Ok::<_, RtLolaError>(Some(EvalSpec {
                            annotated_pacing,
                            condition: new_condition,
                            eval_expression: new_eval,
                            id,
                            span,
                        }))
                    })
                    .flatten_ok()
                    .collect::<Result<_, _>>()?;

                let new_close_spec = if let Some(close_spec) = close {
                    let CloseSpec {
                        condition,
                        id,
                        span,
                        annotated_pacing,
                    } = close_spec;
                    let (new_condition, close_cs) = Self::desugarize_expression(
                        condition,
                        &ast,
                        current_sugar,
                        ix,
                        ExprOrigin::CloseWhen,
                    )?;
                    change_set += close_cs;
                    Some(CloseSpec {
                        condition: new_condition,
                        id,
                        span,
                        annotated_pacing,
                    })
                } else {
                    None
                };

                let new_out = Output {
                    spawn: new_spawn_spec,
                    eval: transformed_eval,
                    close: new_close_spec,
                    ..out_clone
                };
                ast.outputs[ix] = Rc::new(new_out);
            }
            for input in ast.inputs.iter() {
                change_set += self.desugarize_input(input, &ast, current_sugar)?;
            }

            for output in ast.outputs.iter() {
                change_set += self.desugarize_output(output, &ast, current_sugar)?;
            }

            change_flag |=
                change_set._local_applied_flag || !change_set.global_instructions.is_empty();
            ast = self.apply_global_changes(change_set, ast);
        }
        Ok((ast, change_flag))
    }

    fn apply_global_changes(&self, c_s: ChangeSet, mut ast: RtLolaAst) -> RtLolaAst {
        c_s.global_iter().for_each(|ci| match ci {
            ChangeInstruction::AddOutput(o) => {
                ast.outputs.push(Rc::new(*o));
            }
            ChangeInstruction::RemoveStream(id) => {
                if let Some(idx) = ast.outputs.iter().position(|o| o.id == id) {
                    assert_eq!(Rc::strong_count(&ast.outputs[idx]), 1);
                    ast.outputs.remove(idx);
                } else if let Some(idx) = ast.inputs.iter().position(|o| o.id == id) {
                    assert_eq!(Rc::strong_count(&ast.inputs[idx]), 1);
                    ast.inputs.remove(idx);
                } else if let Some(idx) = ast.mirrors.iter().position(|o| o.id == id) {
                    assert_eq!(Rc::strong_count(&ast.mirrors[idx]), 1);
                    ast.mirrors.remove(idx);
                } else {
                    debug_assert!(false, "id in changeset does not belong to any stream");
                }
            }
            ChangeInstruction::ReplaceExpr(_, expr) => {
                for ix in 0..ast.outputs.len() {
                    let out = &ast.outputs[ix];
                    let out_clone: Output = Output::clone(out);
                    let Output {
                        spawn, eval, close, ..
                    } = out_clone;
                    let new_spawn_spec = if let Some(spawn_spec) = spawn {
                        let SpawnSpec {
                            expression,
                            condition,
                            annotated_pacing,
                            id,
                            span,
                        } = spawn_spec;
                        let expression = expression.map(|tar_expression| {
                            Self::apply_expr_global_change(id, &expr, &tar_expression)
                        });
                        let condition = condition.map(|cond_expression| {
                            Self::apply_expr_global_change(id, &expr, &cond_expression)
                        });
                        Some(SpawnSpec {
                            expression,
                            condition,
                            annotated_pacing,
                            id,
                            span,
                        })
                    } else {
                        None
                    };

                    let new_eval_spec = eval
                        .into_iter()
                        .flat_map(|eval_spec| {
                            let EvalSpec {
                                eval_expression,
                                condition,
                                annotated_pacing,
                                id,
                                span,
                            } = eval_spec;
                            let eval_expression = eval_expression
                                .map(|e| Self::apply_expr_global_change(id, &expr, &e));
                            let condition =
                                condition.map(|e| Self::apply_expr_global_change(id, &expr, &e));
                            Some(EvalSpec {
                                annotated_pacing,
                                condition,
                                eval_expression,
                                id,
                                span,
                            })
                        })
                        .collect();

                    let new_close_spec = if let Some(close_spec) = close {
                        let CloseSpec {
                            condition,
                            id,
                            span,
                            annotated_pacing,
                        } = close_spec;
                        let new_condition = Self::apply_expr_global_change(id, &expr, &condition);
                        Some(CloseSpec {
                            condition: new_condition,
                            id,
                            span,
                            annotated_pacing,
                        })
                    } else {
                        None
                    };

                    let new_out = Output {
                        spawn: new_spawn_spec,
                        eval: new_eval_spec,
                        close: new_close_spec,
                        ..out_clone
                    };
                    ast.outputs[ix] = Rc::new(new_out);
                }
            }
        });

        ast
    }

    fn apply_expr_global_change(
        target_id: NodeId,
        new_expr: &Expression,
        ast_expr: &Expression,
    ) -> Expression {
        if ast_expr.id == target_id {
            return new_expr.clone();
        }
        let span = ast_expr.span;

        use ExpressionKind::*;
        match &ast_expr.kind {
            Lit(_) | Ident(_) | MissingExpression => ast_expr.clone(),
            Unary(op, inner) => Expression {
                kind: Unary(
                    *op,
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, inner)),
                ),
                span,
                ..*ast_expr
            },
            Field(inner, ident) => Expression {
                kind: Field(
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, inner)),
                    ident.clone(),
                ),
                span,
                ..*ast_expr
            },
            StreamAccess(inner, acc_kind) => Expression {
                kind: StreamAccess(
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, inner)),
                    *acc_kind,
                ),
                span,
                ..*ast_expr
            },
            Offset(inner, offset) => Expression {
                kind: Offset(
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, inner)),
                    *offset,
                ),
                span,
                ..*ast_expr
            },
            ParenthesizedExpression(inner) => Expression {
                kind: ParenthesizedExpression(Box::new(Self::apply_expr_global_change(
                    target_id, new_expr, inner,
                ))),
                span,
                ..*ast_expr
            },
            Binary(bin_op, left, right) => Expression {
                kind: Binary(
                    *bin_op,
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, left)),
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, right)),
                ),
                span,
                ..*ast_expr
            },
            Default(left, right) => Expression {
                kind: Default(
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, left)),
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, right)),
                ),
                span,
                ..*ast_expr
            },
            DiscreteWindowAggregation {
                expr: left,
                duration: right,
                wait,
                aggregation,
                ..
            } => Expression {
                kind: DiscreteWindowAggregation {
                    expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, left)),
                    duration: Box::new(Self::apply_expr_global_change(target_id, new_expr, right)),
                    wait: *wait,
                    aggregation: *aggregation,
                },
                span,
                ..*ast_expr
            },
            SlidingWindowAggregation {
                expr: left,
                duration: right,
                wait,
                aggregation,
            } => Expression {
                kind: SlidingWindowAggregation {
                    expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, left)),
                    duration: Box::new(Self::apply_expr_global_change(target_id, new_expr, right)),
                    wait: *wait,
                    aggregation: *aggregation,
                },
                span,
                ..*ast_expr
            },
            InstanceAggregation {
                expr,
                selection,
                aggregation,
            } => {
                let selection = match selection {
                    InstanceSelection::Fresh => InstanceSelection::Fresh,
                    InstanceSelection::All => InstanceSelection::All,
                    InstanceSelection::FilteredFresh(LambdaExpr {
                        parameters,
                        expr: cond,
                    }) => InstanceSelection::FilteredFresh(LambdaExpr {
                        parameters: parameters.clone(),
                        expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, cond)),
                    }),
                    InstanceSelection::FilteredAll(LambdaExpr {
                        parameters,
                        expr: cond,
                    }) => InstanceSelection::FilteredAll(LambdaExpr {
                        parameters: parameters.clone(),
                        expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, cond)),
                    }),
                };
                Expression {
                    kind: InstanceAggregation {
                        expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, expr)),
                        selection,
                        aggregation: *aggregation,
                    },
                    span,
                    ..*ast_expr
                }
            }
            Ite(condition, normal, alternative) => Expression {
                kind: Ite(
                    Box::new(Self::apply_expr_global_change(
                        target_id, new_expr, condition,
                    )),
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, normal)),
                    Box::new(Self::apply_expr_global_change(
                        target_id,
                        new_expr,
                        alternative,
                    )),
                ),
                span,
                ..*ast_expr
            },
            Tuple(entries) => Expression {
                kind: Tuple(
                    entries
                        .iter()
                        .map(|t_expr| Self::apply_expr_global_change(target_id, new_expr, t_expr))
                        .collect(),
                ),
                span,
                ..*ast_expr
            },
            Function(name, types, entries) => Expression {
                kind: Function(
                    name.clone(),
                    types.clone(),
                    entries
                        .iter()
                        .map(|t_expr| Self::apply_expr_global_change(target_id, new_expr, t_expr))
                        .collect(),
                ),
                span,
                ..*ast_expr
            },
            Method(base, name, types, arguments) => Expression {
                kind: Method(
                    Box::new(Self::apply_expr_global_change(target_id, new_expr, base)),
                    name.clone(),
                    types.clone(),
                    arguments
                        .iter()
                        .map(|t_expr| Self::apply_expr_global_change(target_id, new_expr, t_expr))
                        .collect(),
                ),
                span,
                ..*ast_expr
            },
            Lambda(LambdaExpr {
                parameters,
                expr: cond,
            }) => Expression {
                kind: Lambda(LambdaExpr {
                    parameters: parameters.clone(),
                    expr: Box::new(Self::apply_expr_global_change(target_id, new_expr, cond)),
                }),
                ..*ast_expr
            },
        }
    }

    /// Climbs along the expression and applies desugarizers and their local changes, while collecting global changes.
    ///
    /// LocalChangeInstructions are directly replied and never returned.
    #[allow(clippy::borrowed_box)]
    fn desugarize_expression(
        ast_expr: Expression,
        ast: &RtLolaAst,
        current_sugar: &Box<dyn SynSugar>,
        stream: usize,
        origin: ExprOrigin,
    ) -> Result<(Expression, ChangeSet), RtLolaError> {
        let mut return_cs = ChangeSet::empty();
        use ExpressionKind::*;
        let Expression { kind, id, span } = ast_expr;
        let new_expr = match kind {
            Lit(_) | Ident(_) | MissingExpression => Expression { kind, id, span },
            Unary(op, inner) => {
                let (inner, cs) =
                    Self::desugarize_expression(*inner, ast, current_sugar, stream, origin)?;
                return_cs += cs;
                Expression {
                    kind: Unary(op, Box::new(inner)),
                    span,
                    id,
                }
            }
            Field(inner, ident) => {
                let (inner, cs) =
                    Self::desugarize_expression(*inner, ast, current_sugar, stream, origin)?;
                return_cs += cs;
                Expression {
                    kind: Field(Box::new(inner), ident),
                    span,
                    id,
                }
            }
            StreamAccess(inner, acc_kind) => {
                let (inner, cs) =
                    Self::desugarize_expression(*inner, ast, current_sugar, stream, origin)?;
                return_cs += cs;
                Expression {
                    kind: StreamAccess(Box::new(inner), acc_kind),
                    span,
                    id,
                }
            }
            Offset(inner, offset) => {
                let (inner, cs) =
                    Self::desugarize_expression(*inner, ast, current_sugar, stream, origin)?;
                return_cs += cs;
                Expression {
                    kind: Offset(Box::new(inner), offset),
                    span,
                    id,
                }
            }
            ParenthesizedExpression(inner) => {
                let (inner, cs) =
                    Self::desugarize_expression(*inner, ast, current_sugar, stream, origin)?;
                return_cs += cs;
                Expression {
                    kind: ParenthesizedExpression(Box::new(inner)),
                    span,
                    id,
                }
            }
            Binary(bin_op, left, right) => {
                let (left, lcs) =
                    Self::desugarize_expression(*left, ast, current_sugar, stream, origin)?;
                return_cs += lcs;
                let (right, rcs) =
                    Self::desugarize_expression(*right, ast, current_sugar, stream, origin)?;
                return_cs += rcs;
                Expression {
                    kind: Binary(bin_op, Box::new(left), Box::new(right)),
                    span,
                    id,
                }
            }
            Default(left, right) => {
                let (left, lcs) =
                    Self::desugarize_expression(*left, ast, current_sugar, stream, origin)?;
                return_cs += lcs;
                let (right, rcs) =
                    Self::desugarize_expression(*right, ast, current_sugar, stream, origin)?;
                return_cs += rcs;
                Expression {
                    kind: Default(Box::new(left), Box::new(right)),
                    span,
                    id,
                }
            }
            DiscreteWindowAggregation {
                expr: left,
                duration: right,
                wait,
                aggregation,
                ..
            } => {
                let (expr, ecs) =
                    Self::desugarize_expression(*left, ast, current_sugar, stream, origin)?;
                return_cs += ecs;
                let (dur, dcs) =
                    Self::desugarize_expression(*right, ast, current_sugar, stream, origin)?;
                return_cs += dcs;
                Expression {
                    kind: DiscreteWindowAggregation {
                        expr: Box::new(expr),
                        duration: Box::new(dur),
                        wait,
                        aggregation,
                    },
                    span,
                    id,
                }
            }
            SlidingWindowAggregation {
                expr: left,
                duration: right,
                wait,
                aggregation,
            } => {
                let (expr, ecs) =
                    Self::desugarize_expression(*left, ast, current_sugar, stream, origin)?;
                return_cs += ecs;
                let (dur, dcs) =
                    Self::desugarize_expression(*right, ast, current_sugar, stream, origin)?;
                return_cs += dcs;
                Expression {
                    kind: SlidingWindowAggregation {
                        expr: Box::new(expr),
                        duration: Box::new(dur),
                        wait,
                        aggregation,
                    },
                    span,
                    id,
                }
            }
            InstanceAggregation {
                expr,
                selection,
                aggregation,
            } => {
                let (expr, ecs) =
                    Self::desugarize_expression(*expr, ast, current_sugar, stream, origin)?;
                let (selection, scs) = match selection {
                    selection @ (InstanceSelection::Fresh | InstanceSelection::All) => {
                        (selection, ChangeSet::empty())
                    }
                    InstanceSelection::FilteredFresh(LambdaExpr {
                        parameters,
                        expr: cond,
                    }) => {
                        let (cond, cs) =
                            Self::desugarize_expression(*cond, ast, current_sugar, stream, origin)?;
                        (
                            InstanceSelection::FilteredFresh(LambdaExpr {
                                parameters,
                                expr: Box::new(cond),
                            }),
                            cs,
                        )
                    }
                    InstanceSelection::FilteredAll(LambdaExpr {
                        parameters,
                        expr: cond,
                    }) => {
                        let (cond, cs) =
                            Self::desugarize_expression(*cond, ast, current_sugar, stream, origin)?;
                        (
                            InstanceSelection::FilteredAll(LambdaExpr {
                                parameters,
                                expr: Box::new(cond),
                            }),
                            cs,
                        )
                    }
                };
                return_cs = return_cs + ecs + scs;
                Expression {
                    kind: InstanceAggregation {
                        expr: Box::new(expr),
                        selection,
                        aggregation,
                    },
                    span,
                    id,
                }
            }
            Ite(condition, normal, alternative) => {
                let (condition, ccs) =
                    Self::desugarize_expression(*condition, ast, current_sugar, stream, origin)?;
                return_cs += ccs;
                let (normal, ncs) =
                    Self::desugarize_expression(*normal, ast, current_sugar, stream, origin)?;
                return_cs += ncs;
                let (alternative, acs) =
                    Self::desugarize_expression(*alternative, ast, current_sugar, stream, origin)?;
                return_cs += acs;
                Expression {
                    kind: Ite(Box::new(condition), Box::new(normal), Box::new(alternative)),
                    span,
                    id,
                }
            }
            Tuple(entries) => {
                let (v_expr, v_cs): (Vec<Expression>, Vec<ChangeSet>) = entries
                    .into_iter()
                    .map(|t_expr| {
                        Self::desugarize_expression(t_expr, ast, current_sugar, stream, origin)
                    })
                    .collect::<Result<_, _>>()?;
                return_cs += v_cs.into_iter().fold(ChangeSet::empty(), |acc, x| acc + x);
                Expression {
                    kind: Tuple(v_expr),
                    span,
                    id,
                }
            }
            Function(name, types, entries) => {
                let (v_expr, v_cs): (Vec<Expression>, Vec<ChangeSet>) = entries
                    .into_iter()
                    .map(|t_expr| {
                        Self::desugarize_expression(t_expr, ast, current_sugar, stream, origin)
                    })
                    .collect::<Result<_, _>>()?;
                return_cs += v_cs.into_iter().fold(ChangeSet::empty(), |acc, x| acc + x);
                Expression {
                    kind: Function(name, types, v_expr),
                    span,
                    id,
                }
            }
            Method(base, name, types, arguments) => {
                let (base_expr, ecs) =
                    Self::desugarize_expression(*base, ast, current_sugar, stream, origin)?;
                return_cs += ecs;
                let (v_expr, v_cs): (Vec<Expression>, Vec<ChangeSet>) = arguments
                    .into_iter()
                    .map(|t_expr| {
                        Self::desugarize_expression(t_expr, ast, current_sugar, stream, origin)
                    })
                    .collect::<Result<_, _>>()?;
                return_cs += v_cs.into_iter().fold(ChangeSet::empty(), |acc, x| acc + x);
                Expression {
                    kind: Method(Box::new(base_expr), name, types, v_expr),
                    span,
                    id,
                }
            }
            Lambda(LambdaExpr {
                parameters,
                expr: cond,
            }) => {
                let (cond, ecs) =
                    Self::desugarize_expression(*cond, ast, current_sugar, stream, origin)?;
                return_cs += ecs;
                Expression {
                    kind: Lambda(LambdaExpr {
                        parameters,
                        expr: Box::new(cond),
                    }),
                    span,
                    id,
                }
            }
        };

        // apply transformation on current expression and replace if local change needed
        let mut current_level_cs = current_sugar.desugarize_expr(&new_expr, ast, stream, origin)?;
        let return_expr = if let Some(LocalChangeInstruction::ReplaceExpr(replace_expr)) =
            current_level_cs.extract_local_change()
        {
            replace_expr
        } else {
            new_expr
        };
        let final_cs = current_level_cs + return_cs;

        Ok((return_expr, final_cs))
    }

    #[allow(clippy::borrowed_box)]
    fn desugarize_input(
        &self,
        input: &Input,
        ast: &RtLolaAst,
        current_sugar: &Box<dyn SynSugar>,
    ) -> Result<ChangeSet, RtLolaError> {
        current_sugar.desugarize_stream_in(input, ast)
    }

    #[allow(clippy::borrowed_box)]
    fn desugarize_mirror(
        &self,
        mirror: &AstMirror,
        ast: &RtLolaAst,
        current_sugar: &Box<dyn SynSugar>,
    ) -> Result<ChangeSet, RtLolaError> {
        current_sugar.desugarize_stream_mirror(mirror, ast)
    }

    #[allow(clippy::borrowed_box)]
    fn desugarize_output(
        &self,
        output: &Output,
        ast: &RtLolaAst,
        current_sugar: &Box<dyn SynSugar>,
    ) -> Result<ChangeSet, RtLolaError> {
        current_sugar.desugarize_stream_out(output, ast)
    }
}

impl Default for Desugarizer {
    fn default() -> Self {
        Self::all()
    }
}

impl ChangeSet {
    /// Construct a new empty ChangeSet.
    fn empty() -> Self {
        Self {
            _local_applied_flag: false,
            local_instructions: None,
            global_instructions: HashSet::new(),
        }
    }

    #[allow(dead_code)] // currently unused
    /// Adds a stream to the Ast.
    pub(crate) fn add_output(stream: Output) -> Self {
        let mut cs = ChangeSet::empty();
        cs.global_instructions
            .insert(ChangeInstruction::AddOutput(Box::new(stream)));
        cs
    }

    #[allow(dead_code)] // currently unused
    /// Replaces the expression with id 'target_id' with the given expression. Performs global ast search.
    pub(crate) fn replace_expression(target_id: NodeId, expr: Expression) -> Self {
        let mut cs = Self::empty();
        cs.global_instructions
            .insert(ChangeInstruction::ReplaceExpr(target_id, expr));
        cs
    }

    #[allow(dead_code)] // currently unused
    /// Removes the stream with id 'target_id'. Performs global ast search.
    pub(crate) fn remove_stream(target_id: NodeId) -> Self {
        let mut cs = Self::empty();
        cs.global_instructions
            .insert(ChangeInstruction::RemoveStream(target_id));
        cs
    }

    /// Replaces the current expression.
    /// Should only be called in <T: SynSugar> T.desugarize_expr(...)
    /// Wanted local changes will not be applied if used in other desugarize functions!
    pub(crate) fn replace_current_expression(expr: Expression) -> Self {
        let mut cs = Self::empty();
        cs.local_instructions = Some(LocalChangeInstruction::ReplaceExpr(expr));
        cs._local_applied_flag = true;
        cs
    }

    /// Replaces the stream with the given NodeId with the new stream. Performs global ast search.
    pub(crate) fn replace_stream(target_stream: NodeId, new_stream: Output) -> Self {
        let mut cs = ChangeSet::empty();
        cs.global_instructions
            .insert(ChangeInstruction::RemoveStream(target_stream));
        cs.global_instructions
            .insert(ChangeInstruction::AddOutput(Box::new(new_stream)));
        cs
    }

    /// Provides an [Iterator] over all global changes.
    fn global_iter<'a>(self) -> Box<dyn Iterator<Item = ChangeInstruction> + 'a> {
        Box::new(self.global_instructions.into_iter().sorted())
    }

    /// Internal use: extracts the wanted local change and removes it from the struct.
    fn extract_local_change(&mut self) -> Option<LocalChangeInstruction> {
        let mut ret = None;
        std::mem::swap(&mut self.local_instructions, &mut ret);
        ret
    }
}

impl std::ops::Add<ChangeSet> for ChangeSet {
    type Output = ChangeSet;

    fn add(self, rhs: Self) -> Self {
        let set = self
            .global_instructions
            .union(&rhs.global_instructions)
            .cloned()
            .collect();
        assert!(self.local_instructions.is_none() || rhs.local_instructions.is_none());
        let local = self.local_instructions.or(rhs.local_instructions);
        Self {
            _local_applied_flag: self._local_applied_flag || rhs._local_applied_flag,
            local_instructions: local,
            global_instructions: set,
        }
    }
}

impl std::ops::AddAssign<ChangeSet> for ChangeSet {
    fn add_assign(&mut self, rhs: Self) {
        let set = self
            .global_instructions
            .union(&rhs.global_instructions)
            .cloned()
            .collect();
        assert!(self.local_instructions.is_none() || rhs.local_instructions.is_none());
        let local = self.local_instructions.clone().or(rhs.local_instructions);
        *self = Self {
            _local_applied_flag: self._local_applied_flag || rhs._local_applied_flag,
            local_instructions: local,
            global_instructions: set,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ast::{BinOp, Ident, LitKind, Literal, Offset, UnOp, WindowOperation};

    #[test]
    fn test_impl_simpl_replace() {
        let spec = "input a:Bool\ninput b:Bool\noutput c eval with a -> b".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        let inner_kind = if let ExpressionKind::Binary(op, lhs, _rhs) = out_kind {
            assert!(matches!(op, BinOp::Or));
            lhs.kind
        } else {
            unreachable!()
        };
        assert!(matches!(inner_kind, ExpressionKind::Unary(UnOp::Not, _)));
    }

    #[test]
    fn test_impl_nested_replace() {
        let spec =
            "input a:Bool\ninput b:Bool\ninput c:Bool\noutput d eval with a -> b -> c".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        let inner_kind = if let ExpressionKind::Binary(op, lhs, rhs) = out_kind {
            assert!(matches!(op, BinOp::Or));
            let inner = if let ExpressionKind::Unary(op, inner) = lhs.kind {
                assert!(matches!(op, UnOp::Not));
                inner
            } else {
                unreachable!()
            };
            assert_eq!(inner.to_string(), "a");
            rhs.kind
        } else {
            unreachable!();
        };
        let inner = if let ExpressionKind::Binary(op, lhs, rhs) = inner_kind {
            assert!(matches!(op, BinOp::Or));
            let inner = if let ExpressionKind::Unary(op, inner) = lhs.kind {
                assert!(matches!(op, UnOp::Not));
                inner
            } else {
                unreachable!()
            };
            assert_eq!(inner.to_string(), "b");
            rhs
        } else {
            unreachable!()
        };
        assert_eq!(inner.to_string(), "c");
    }

    #[test]
    fn test_offsetor_replace() {
        let spec = "output x eval @5Hz with x.offset(by: -4, or: 5.0)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        let inner_kind = if let ExpressionKind::Default(inner, default) = out_kind {
            assert!(matches!(default.kind, ExpressionKind::Lit(_)));
            inner.kind
        } else {
            unreachable!()
        };
        assert!(matches!(
            inner_kind,
            ExpressionKind::Offset(_, Offset::Discrete(-4))
        ));
    }

    #[test]
    fn test_offsetor_replace_nested() {
        let spec =
            "output x eval @5Hz with -x.offset(by: -4, or: x.offset(by: -1, or: 5))".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        let inner_kind = if let ExpressionKind::Unary(UnOp::Neg, inner) = out_kind {
            inner.kind
        } else {
            unreachable!()
        };
        let (inner_kind, default_kind) = if let ExpressionKind::Default(inner, default) = inner_kind
        {
            (inner.kind, default.kind)
        } else {
            unreachable!()
        };
        assert!(matches!(
            inner_kind,
            ExpressionKind::Offset(_, Offset::Discrete(-4))
        ));
        let inner_kind = if let ExpressionKind::Default(inner, default) = default_kind {
            assert!(matches!(default.kind, ExpressionKind::Lit(_)));
            inner.kind
        } else {
            unreachable!()
        };
        assert!(matches!(
            inner_kind,
            ExpressionKind::Offset(_, Offset::Discrete(-1))
        ));
    }

    #[test]
    fn test_aggr_replace() {
        let spec = "output x eval @5Hz with x.count(6s)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert!(matches!(
            ast.outputs[0].eval[0].clone().eval_expression.unwrap().kind,
            ExpressionKind::SlidingWindowAggregation {
                aggregation: WindowOperation::Count,
                ..
            }
        ));
    }

    #[test]
    fn test_aggr_replace_nested() {
        let spec = "output x eval @ 5hz with -x.sum(6s)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        assert!(matches!(out_kind, ExpressionKind::Unary(UnOp::Neg, _)));
        let inner_kind = if let ExpressionKind::Unary(UnOp::Neg, inner) = out_kind {
            inner.kind
        } else {
            unreachable!()
        };
        assert!(matches!(
            inner_kind,
            ExpressionKind::SlidingWindowAggregation {
                aggregation: WindowOperation::Sum,
                ..
            }
        ));
    }

    #[test]
    fn test_aggr_replace_multiple() {
        let spec = "output x eval @5hz with x.avg(5s) - x.integral(2.5s)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        assert!(matches!(out_kind, ExpressionKind::Binary(BinOp::Sub, _, _)));
        let (left, right) = if let ExpressionKind::Binary(BinOp::Sub, left, right) = out_kind {
            (left.kind, right.kind)
        } else {
            unreachable!()
        };
        assert!(matches!(
            left,
            ExpressionKind::SlidingWindowAggregation {
                aggregation: WindowOperation::Average,
                ..
            }
        ));
        assert!(matches!(
            right,
            ExpressionKind::SlidingWindowAggregation {
                aggregation: WindowOperation::Integral,
                ..
            }
        ));
    }

    #[test]
    fn test_last_replace() {
        let spec = "output x eval @5hz with x.last(or: 3)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        let out_kind = ast.outputs[0].eval[0]
            .clone()
            .eval_expression
            .unwrap()
            .kind
            .clone();
        let (access, dft) = if let ExpressionKind::Default(access, dft) = out_kind {
            (access.kind, dft.kind)
        } else {
            panic!("Last should result in a top-level default access with its argument as default value")
        };
        assert!(
            matches!(
                &dft,
                &ExpressionKind::Lit(Literal {
                    kind: LitKind::Numeric(ref x, None),
                    ..
                }) if x == &String::from("3")
            ),
            "The argument of last should be the default expression."
        );
        let stream = if let ExpressionKind::Offset(stream, Offset::Discrete(-1)) = access {
            stream
        } else {
            panic!("expected an offset expression, but found {:?}", access);
        };

        assert!(
            matches!(*stream, Expression { kind: ExpressionKind::Ident(Ident { name, .. }), ..} if name == String::from("x") )
        );
    }

    #[test]
    fn test_delta_replace() {
        let spec = "output y eval with delta(x,dft:0)".to_string();
        let expected = "output y eval with x - x.offset(by: -1).defaults(to: 0)";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_delta_replace_float() {
        let spec = "output y eval with delta(x, or: 0.0)".to_string();
        let expected = "output y eval with x - x.offset(by: -1).defaults(to: 0.0)";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_mirror_replace_str_cmp() {
        let spec = "output x eval with 3 \noutput y mirrors x when x > 5".to_string();
        let expected = "output x eval with 3\noutput y eval when x > 5 with 3";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_mirror_replace_multiple_eval() {
        let spec = "output x eval when a > 0 with 3 eval when a < 0 with -3\noutput y mirrors x when x > 5".to_string();
        let expected = "output x eval when a > 0 with 3 eval when a < 0 with -3\noutput y eval when a > 0 ∧ x > 5 with 3 eval when a < 0 ∧ x > 5 with -3";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_aggregation() {
        let spec = "input a: Bool\n\
        output b eval @1Hz with a.aggregate(over: 1s, using: true_ratio)\n"
            .to_string();
        let expected = "input a: Bool\n\
            output b eval @1Hz with a'.aggregate(over: 1s, using: avg)\n\
            output a' eval with if a then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_aggregation_from_output() {
        let spec = "input a: Bool\n\
        output b eval with a\n\
        output c eval @1Hz with b.aggregate(over: 1s, using: true_ratio)\n"
            .to_string();
        let expected = "input a: Bool\n\
            output b eval with a\n\
            output c eval @1Hz with b'.aggregate(over: 1s, using: avg)\n\
            output b' eval with if b then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_parameterized() {
        let spec = "input a: Bool\n\
        output b (p) spawn with a eval @1Hz with a.aggregate(over: 1s, using: true_ratio)\n"
            .to_string();
        let expected = "input a: Bool\n\
            output b (p) spawn with a eval @1Hz with a'.aggregate(over: 1s, using: avg)\n\
            output a' eval with if a then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_parameterized_2() {
        let spec = "input a: Bool\n\
        output b (p) spawn with a eval when a = p with a\n\
        output c (p) spawn with a eval @1Hz with b(p).aggregate(over: 1s, using: true_ratio)\n"
            .to_string();
        let expected = "input a: Bool\n\
            output b (p) spawn with a eval when a = p with a\n\
            output c (p) spawn with a eval @1Hz with b'(p).aggregate(over: 1s, using: avg)\n\
            output b' (p) spawn with a eval when a = p with if b(p) then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_instances() {
        let spec = "input a: UInt8\n\
        output a' (p) spawn @a with a eval @a when a = p with a + p > 5\n\
        output b eval @1Hz with a'.aggregate(over_instances: all, using: true_ratio)\n"
            .to_string();
        let expected = "input a: UInt8\n\
            output a' (p) spawn @a with a eval @a when a = p with a + p > 5\n\
            output b eval @1Hz with a''.aggregate(over_instances: all, using: avg)\n\
            output a'' (p) spawn @a with a eval @a when a = p with if a'(p) then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_true_ratio_name() {
        let spec = "input a: Boolean\n\
        input a': Boolean\n\
        input a'': Boolean\n\
        input a''': Boolean\n\
        output b eval @1Hz with a'.aggregate(over: 1s, using: true_ratio)"
            .to_string();
        let expected = "input a: Boolean\n\
        input a': Boolean\n\
        input a'': Boolean\n\
        input a''': Boolean\n\
        output b eval @1Hz with a''''.aggregate(over: 1s, using: avg)\n\
            output a'''' eval with if a' then 1.0 else 0.0";
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_probability() {
        let spec = "input a : Bool\n\
        input b : Bool\n\
        output c := prob(of: a, given: b)"
            .to_string();
        let expected = "input a: Bool
input b: Bool
output c eval with if count_given' = 0.0 then 0.0 else count_both' / count_given'
output count_both' eval with count_both'.offset(by: -1).defaults(to: 0.0) + if a ∧ b then 1.0 else 0.0
output count_given' eval with count_given'.offset(by: -1).defaults(to: 0.0) + if b ∧ a = a then 1.0 else 0.0".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_probability2() {
        let spec = "input a : UInt64\n\
        input b : UInt64\n\
        output c := prob(of: a > 5, given: b < 10, prior: 0.5, confidence: 2.0)"
            .to_string();
        let expected = "input a: UInt64
input b: UInt64
output c eval with if (count_given' + 2.0) = 0.0 then 0.0 else (count_both' + 0.5 * 2.0) / (count_given' + 2.0)
output count_both' eval with count_both'.offset(by: -1).defaults(to: 0.0) + if a > 5 ∧ b < 10 then 1.0 else 0.0
output count_given' eval with count_given'.offset(by: -1).defaults(to: 0.0) + if b < 10 ∧ a > 5 = a > 5 then 1.0 else 0.0".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_probability3() {
        let spec = "input a : Bool\n\
        output c := prob(of: a)"
            .to_string();
        let expected = "input a: Bool
output c eval with if count_given' = 0.0 then 0.0 else count_both' / count_given'
output count_both' eval with count_both'.offset(by: -1).defaults(to: 0.0) + if a then 1.0 else 0.0
output count_given' eval with count_given'.offset(by: -1).defaults(to: 0.0) + if a = a then 1.0 else 0.0"
            .to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_probability_spawn_close() {
        let spec = "input a : Bool\n\
        output c 
            spawn when a
            eval when a == 0 with prob(of: a)
            close when a"
            .to_string();
        let expected = "input a: Bool
output c spawn when a eval when a = 0 with if count_given' = 0.0 then 0.0 else count_both' / count_given' close when a
output count_both' spawn when a eval when a = 0 with count_both'.offset(by: -1).defaults(to: 0.0) + if a then 1.0 else 0.0 close when a
output count_given' spawn when a eval when a = 0 with count_given'.offset(by: -1).defaults(to: 0.0) + if a = a then 1.0 else 0.0 close when a"
            .to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn test_probability_parameterized() {
        let spec = "input a: Bool\ninput i: UInt64
output c(p)
    spawn with i
    eval with prob(of: a, given: p == i)"
            .to_string();
        let expected = "input a: Bool
input i: UInt64
output c (p) spawn with i eval with if count_given'(p) = 0.0 then 0.0 else count_both'(p) / count_given'(p)
output count_both' (p) spawn with i eval with count_both'(p).offset(by: -1).defaults(to: 0.0) + if a ∧ p = i then 1.0 else 0.0
output count_given' (p) spawn with i eval with count_given'(p).offset(by: -1).defaults(to: 0.0) + if p = i ∧ a = a then 1.0 else 0.0"
            .to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn probability_instance_aggregation_of() {
        let spec = "input a : UInt64
        output b(p)
            spawn with a
            eval when p == a with b(p).last(or: 0) + 1 
        output c := b.prob(of: p => p > 5)
        "
        .to_string();
        let expected = "input a: UInt64
output b (p) spawn with a eval when p = a with b(p).offset(by: -1).defaults(to: 0) + 1
output c eval with if b.aggregate(over_instances: all, using: #) = 0.0 then 0.0 else b.aggregate(over_instances: all(where: (p) => p > 5), using: #) / b.aggregate(over_instances: all, using: #)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn probability_instance_aggregation_of_given() {
        let spec = "input a : UInt64
        output b(p)
            spawn with a
            eval when p == a with b(p).last(or: 0) + 1 
        output c := b.prob(of: p => p > 5, given: p => p < 10)
        "
        .to_string();
        let expected = "input a: UInt64
output b (p) spawn with a eval when p = a with b(p).offset(by: -1).defaults(to: 0) + 1
output c eval with if b.aggregate(over_instances: all(where: (p) => p < 10), using: #) = 0.0 then 0.0 else b.aggregate(over_instances: all(where: (p) => p > 5 ∧ p < 10), using: #) / b.aggregate(over_instances: all(where: (p) => p < 10), using: #)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }

    #[test]
    fn probability_instance_aggregation_of_given_prior() {
        let spec = "input a : UInt64
        output b(p)
            spawn with a
            eval when p == a with b(p).last(or: 0) + 1 
        output c := b.prob(of: p => p > 5, given: p => p < 10, prior: 5.0, confidence: 10.0)
        "
        .to_string();
        let expected = "input a: UInt64
output b (p) spawn with a eval when p = a with b(p).offset(by: -1).defaults(to: 0) + 1
output c eval with if (b.aggregate(over_instances: all(where: (p) => p < 10), using: #) + 10.0) = 0.0 then 0.0 else (b.aggregate(over_instances: all(where: (p) => p > 5 ∧ p < 10), using: #) + 5.0 * 10.0) / (b.aggregate(over_instances: all(where: (p) => p < 10), using: #) + 10.0)".to_string();
        let ast = crate::parse(&crate::ParserConfig::for_string(spec)).unwrap();
        assert_eq!(expected, format!("{}", ast).trim());
    }
}