use crate::CompilationError;
use crate::context::Context;
use crate::schemas::path;
use crate::step::BoolCollector;
use crate::step::Node;
use crate::step::StepMaker;

use preserves::value::IOValue;

pub trait Predicate: std::fmt::Debug {
    fn test(&mut self, ctxt: &mut Context, value: &IOValue) -> bool;
}

#[derive(Debug)]
pub enum CompiledPredicate {
    Selector(Node),
    Not(Box<CompiledPredicate>),
    Or(Vec<CompiledPredicate>),
    And(Vec<CompiledPredicate>),
}

impl path::Predicate {
    pub fn compile(&self) -> Result<CompiledPredicate, CompilationError> {
        match self {
            path::Predicate::Selector(b) =>
                Ok(CompiledPredicate::Selector((&**b).connect(BoolCollector::new())?)),
            path::Predicate::Not { pred } =>
                Ok(CompiledPredicate::Not(Box::new((&**pred).compile()?))),
            path::Predicate::Or { preds } =>
                Ok(CompiledPredicate::Or(preds.iter().map(Self::compile).collect::<Result<_,_>>()?)),
            path::Predicate::And { preds } =>
                Ok(CompiledPredicate::And(preds.iter().map(Self::compile).collect::<Result<_,_>>()?)),
        }
    }

    pub fn exec(&self, ctxt: &mut Context, value: &IOValue) -> Result<bool, CompilationError> {
        Ok(self.compile()?.test(ctxt, value))
    }
}

impl Predicate for CompiledPredicate {
    fn test(&mut self, ctxt: &mut Context, value: &IOValue) -> bool {
        match self {
            CompiledPredicate::Selector(n) => n.test(ctxt, value),
            CompiledPredicate::Not(p) => !p.test(ctxt, value),
            CompiledPredicate::Or(ps) => {
                for p in ps.iter_mut() {
                    if p.test(ctxt, value) {
                        return true;
                    }
                }
                return false;
            },
            CompiledPredicate::And(ps) => {
                for p in ps.iter_mut() {
                    if !p.test(ctxt, value) {
                        return false;
                    }
                }
                return true;
            },
        }
    }
}