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//! Implementation of the context for closures (lambdas).

use crate::AstNode;
use dsntk_feel::closure::Closure;
use dsntk_feel::{Name, QualifiedName};
use std::collections::BTreeSet;

/// Context for closures (lambdas).
#[derive(Default)]
pub struct ClosureBuilder {
  /// Collection of parameter names in function definitions.
  parameter_names: BTreeSet<QualifiedName>,
  /// Collection of names used in expressions.
  names: BTreeSet<QualifiedName>,
}

impl ClosureBuilder {
  pub fn from_node(node: &AstNode) -> Closure {
    let mut closure_context = ClosureBuilder::default();
    closure_context.visit_1(node, 0);
    closure_context
      .names
      .difference(&closure_context.parameter_names)
      .cloned()
      .collect::<Vec<QualifiedName>>()
      .into()
  }

  pub fn from_function_definition(lhs: &AstNode, rhs: &AstNode) -> Closure {
    let mut closure_context = ClosureBuilder::default();
    closure_context.visit_2(lhs, rhs, 0);
    closure_context
      .names
      .difference(&closure_context.parameter_names)
      .cloned()
      .collect::<Vec<QualifiedName>>()
      .into()
  }

  /// Returns an empty vector of names.
  fn visit_0(&mut self, _: usize) -> Vec<Name> {
    vec![]
  }

  /// Visits a single AST node.
  fn visit_1(&mut self, node: &AstNode, path_level: usize) -> Vec<Name> {
    match node {
      AstNode::Add(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::And(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::At(_) => self.visit_0(path_level),
      AstNode::Between(lhs, mhs, rhs) => self.visit_3(lhs, mhs, rhs, path_level),
      AstNode::Boolean(_) => self.visit_0(path_level),
      AstNode::CommaList(lhs) => self.visit_list(lhs, path_level),
      AstNode::Context(lhs) => self.visit_list(lhs, path_level),
      AstNode::ContextEntry(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::ContextEntryKey(_) => self.visit_0(path_level),
      AstNode::ContextType(lhs) => self.visit_list(lhs, path_level),
      AstNode::ContextTypeEntry(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::ContextTypeEntryKey(_) => self.visit_0(path_level),
      AstNode::Div(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Eq(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::EvaluatedExpression(lhs) => self.visit_1(lhs, path_level),
      AstNode::Every(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Exp(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::ExpressionList(lhs) => self.visit_list(lhs, path_level),
      AstNode::FeelType(_) => self.visit_0(path_level),
      AstNode::Filter(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::For(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::FormalParameter(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::FormalParameters(lhs) => self.visit_list(lhs, path_level),
      AstNode::FunctionBody(lhs, _) => self.visit_1(lhs, path_level),
      AstNode::FunctionDefinition(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::FunctionInvocation(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::FunctionType(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Ge(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Gt(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::If(lhs, mhs, rhs) => self.visit_3(lhs, mhs, rhs, path_level),
      AstNode::In(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::InstanceOf(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::IntervalEnd(lhs, _) => self.visit_1(lhs, path_level),
      AstNode::IntervalStart(lhs, _) => self.visit_1(lhs, path_level),
      AstNode::Irrelevant => self.visit_0(path_level),
      AstNode::IterationContexts(lhs) => self.visit_list(lhs, path_level),
      AstNode::IterationContextList(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::IterationContextRange(lhs, mhs, rhs) => self.visit_3(lhs, mhs, rhs, path_level),
      AstNode::Le(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::List(lhs) => self.visit_list(lhs, path_level),
      AstNode::ListType(lhs) => self.visit_1(lhs, path_level),
      AstNode::Lt(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Mul(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Name(name) => {
        if path_level == 0 {
          let closure_name = name.clone();
          self.names.insert(closure_name.into());
        }
        vec![name.clone()]
      }
      AstNode::NamedParameter(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::NamedParameters(lhs) => self.visit_list(lhs, path_level),
      AstNode::Neg(lhs) => self.visit_1(lhs, path_level),
      AstNode::NegatedList(lhs) => self.visit_list(lhs, path_level),
      AstNode::Null => self.visit_0(path_level),
      AstNode::Numeric(_, _, _, _) => self.visit_0(path_level),
      AstNode::Nq(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Or(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::Out(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::ParameterName(name) => {
        let parameter_name = name.clone();
        self.parameter_names.insert(parameter_name.into());
        vec![name.clone()]
      }
      AstNode::ParameterTypes(lhs) => self.visit_list(lhs, path_level),
      AstNode::Path(lhs, rhs) => {
        let mut parts = self.visit_1(rhs, path_level + 1);
        let mut name = self.visit_1(lhs, path_level + 1);
        parts.append(&mut name);
        if path_level == 0 {
          let mut closure_parts = parts.clone();
          closure_parts.reverse();
          self.names.insert(closure_parts.into());
        }
        parts
      }
      AstNode::PositionalParameters(lhs) => self.visit_list(lhs, path_level),
      AstNode::QualifiedName(lhs) => self.visit_list(lhs, path_level),
      AstNode::QualifiedNameSegment(_name) => self.visit_0(path_level), //TODO verify if also must be used
      AstNode::QuantifiedContext(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::QuantifiedContexts(lhs) => self.visit_list(lhs, path_level),
      AstNode::Range(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::RangeType(lhs) => self.visit_1(lhs, path_level),
      AstNode::Some(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::String(_) => self.visit_0(path_level),
      AstNode::Sub(lhs, rhs) => self.visit_2(lhs, rhs, path_level),
      AstNode::UnaryGe(lhs) => self.visit_1(lhs, path_level),
      AstNode::UnaryGt(lhs) => self.visit_1(lhs, path_level),
      AstNode::UnaryLe(lhs) => self.visit_1(lhs, path_level),
      AstNode::UnaryLt(lhs) => self.visit_1(lhs, path_level),
      AstNode::UnaryEq(lhs) => self.visit_1(lhs, path_level),
      AstNode::UnaryNe(lhs) => self.visit_1(lhs, path_level),
      AstNode::Satisfies(lhs) => self.visit_1(lhs, path_level),
    }
  }

  /// Visits two AST nodes.
  fn visit_2(&mut self, lhs: &AstNode, rhs: &AstNode, path_level: usize) -> Vec<Name> {
    self.visit_1(lhs, path_level);
    self.visit_1(rhs, path_level);
    vec![]
  }

  /// Visits three AST nodes.
  fn visit_3(&mut self, lhs: &AstNode, mhs: &AstNode, rhs: &AstNode, path_level: usize) -> Vec<Name> {
    self.visit_1(lhs, path_level);
    self.visit_1(mhs, path_level);
    self.visit_1(rhs, path_level);
    vec![]
  }

  /// Visits a list of AST nodes.
  fn visit_list(&mut self, lhs: &Vec<AstNode>, path_level: usize) -> Vec<Name> {
    for item in lhs {
      self.visit_1(item, path_level);
    }
    vec![]
  }
}