theory_core 0.1.0

//! Constraint Utilities and Trait Definitions
//!
//! Provides utilities for working with constraints and interfaces
//! for constraint-based reasoning.

use crate::ir::{ConstraintIR, Expr, VarId};
use anyhow::Result;
// use eenn::tensor::Tensor;  // Not needed for stub
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

/// Context for constraint evaluation and checking
#[derive(Debug, Clone)]
pub struct ConstraintContext {
    /// Variable assignments
    pub assignments: HashMap<VarId, ConstraintValue>,
    /// Evaluation tolerance for approximate checks
    pub tolerance: f64,
}

/// Values that can be assigned to constraint variables
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum ConstraintValue {
    Bool(bool),
    Integer(i64),
    Real(f64),
    String(String),
    BitVector { value: u64, width: u32 },
    Array(Vec<ConstraintValue>),
}

/// Result of constraint checking
#[derive(Debug, Clone)]
pub struct ConstraintCheckResult {
    /// Whether the constraint is satisfied
    pub satisfied: bool,
    /// Confidence in the result (0.0 to 1.0)
    pub confidence: f32,
    /// Additional information about the check
    pub info: Option<String>,
}

/// Trait for constraint checking and evaluation
pub trait ConstraintChecker: Send + Sync {
    /// Check if constraints are satisfied in the given context
    fn check_constraints(
        &self,
        constraints: &ConstraintIR,
        context: &ConstraintContext,
    ) -> Result<ConstraintCheckResult>;

    /// Evaluate an expression in the given context
    fn evaluate_expression(
        &self,
        expr: &Expr,
        context: &ConstraintContext,
    ) -> Result<ConstraintValue>;

    /// Find satisfying assignments for constraints
    fn find_satisfying_assignment(
        &self,
        constraints: &ConstraintIR,
    ) -> Result<Option<HashMap<VarId, ConstraintValue>>>;
}

/// Basic constraint checker implementation
pub struct BasicConstraintChecker {
    tolerance: f64,
}

impl BasicConstraintChecker {
    pub fn new(tolerance: f64) -> Self {
        Self { tolerance }
    }
}

impl ConstraintChecker for BasicConstraintChecker {
    fn check_constraints(
        &self,
        constraints: &ConstraintIR,
        context: &ConstraintContext,
    ) -> Result<ConstraintCheckResult> {
        let mut all_satisfied = true;
        let mut confidence_sum = 0.0;
        let mut constraint_count = 0;

        for constraint in &constraints.constraints {
            let satisfied = self.check_single_constraint(constraint, context)?;

            if !satisfied {
                all_satisfied = false;
            }

            confidence_sum += if satisfied { 1.0 } else { 0.0 };
            constraint_count += 1;
        }

        let confidence = if constraint_count > 0 {
            confidence_sum / constraint_count as f32
        } else {
            1.0
        };

        Ok(ConstraintCheckResult {
            satisfied: all_satisfied,
            confidence,
            info: None,
        })
    }

    fn evaluate_expression(
        &self,
        expr: &Expr,
        context: &ConstraintContext,
    ) -> Result<ConstraintValue> {
        match expr {
            Expr::Var(var_id) => context
                .assignments
                .get(var_id)
                .cloned()
                .ok_or_else(|| anyhow::anyhow!("Variable {:?} not found in context", var_id)),
            Expr::Const(const_val) => Ok(match const_val {
                crate::ir::ConstValue::Bool(b) => ConstraintValue::Bool(*b),
                crate::ir::ConstValue::Integer(i) => ConstraintValue::Integer(*i),
                crate::ir::ConstValue::Real(r) => ConstraintValue::Real(*r),
                crate::ir::ConstValue::String(s) => ConstraintValue::String(s.clone()),
                crate::ir::ConstValue::BitVector { value, width } => ConstraintValue::BitVector {
                    value: *value,
                    width: *width,
                },
            }),
            Expr::Binary { op, lhs, rhs } => {
                let lhs_val = self.evaluate_expression(lhs, context)?;
                let rhs_val = self.evaluate_expression(rhs, context)?;

                self.evaluate_binary_op(op, &lhs_val, &rhs_val)
            }
            Expr::Unary { op, operand } => {
                let operand_val = self.evaluate_expression(operand, context)?;
                self.evaluate_unary_op(op, &operand_val)
            }
            Expr::Call {
                function: _,
                args: _,
            } => {
                // TODO: Implement function calls
                Err(anyhow::anyhow!("Function calls not yet implemented"))
            }
        }
    }

    fn find_satisfying_assignment(
        &self,
        _constraints: &ConstraintIR,
    ) -> Result<Option<HashMap<VarId, ConstraintValue>>> {
        // TODO: Implement basic constraint solving
        // For now, return None (no solution found)
        Ok(None)
    }
}

impl BasicConstraintChecker {
    /// Check a single constraint
    fn check_single_constraint(
        &self,
        constraint: &crate::ir::Constraint,
        context: &ConstraintContext,
    ) -> Result<bool> {
        match constraint {
            crate::ir::Constraint::Equal { lhs, rhs } => {
                let lhs_val = self.evaluate_expression(lhs, context)?;
                let rhs_val = self.evaluate_expression(rhs, context)?;
                Ok(self.values_equal(&lhs_val, &rhs_val))
            }
            crate::ir::Constraint::Less { lhs, rhs } => {
                let lhs_val = self.evaluate_expression(lhs, context)?;
                let rhs_val = self.evaluate_expression(rhs, context)?;
                Ok(self.value_less_than(&lhs_val, &rhs_val)?)
            }
            crate::ir::Constraint::LessEqual { lhs, rhs } => {
                let lhs_val = self.evaluate_expression(lhs, context)?;
                let rhs_val = self.evaluate_expression(rhs, context)?;
                Ok(self.value_less_than(&lhs_val, &rhs_val)?
                    || self.values_equal(&lhs_val, &rhs_val))
            }
            crate::ir::Constraint::And { constraints } => {
                for sub_constraint in constraints {
                    if !self.check_single_constraint(sub_constraint, context)? {
                        return Ok(false);
                    }
                }
                Ok(true)
            }
            crate::ir::Constraint::Or { constraints } => {
                for sub_constraint in constraints {
                    if self.check_single_constraint(sub_constraint, context)? {
                        return Ok(true);
                    }
                }
                Ok(false)
            }
            crate::ir::Constraint::Not { constraint } => {
                Ok(!self.check_single_constraint(constraint, context)?)
            }
            crate::ir::Constraint::Implies {
                antecedent,
                consequent,
            } => {
                let antecedent_satisfied = self.check_single_constraint(antecedent, context)?;
                if !antecedent_satisfied {
                    Ok(true) // Implication vacuously true
                } else {
                    self.check_single_constraint(consequent, context)
                }
            }
            crate::ir::Constraint::Custom { name: _, params: _ } => {
                // TODO: Implement custom constraint checking
                Ok(true) // Assume satisfied for now
            }
        }
    }

    /// Evaluate binary operation on constraint values
    fn evaluate_binary_op(
        &self,
        op: &crate::ir::BinaryOp,
        lhs: &ConstraintValue,
        rhs: &ConstraintValue,
    ) -> Result<ConstraintValue> {
        use crate::ir::BinaryOp;

        match (lhs, rhs) {
            (ConstraintValue::Integer(a), ConstraintValue::Integer(b)) => Ok(match op {
                BinaryOp::Add => ConstraintValue::Integer(a + b),
                BinaryOp::Sub => ConstraintValue::Integer(a - b),
                BinaryOp::Mul => ConstraintValue::Integer(a * b),
                BinaryOp::Div => ConstraintValue::Integer(a / b),
                BinaryOp::Mod => ConstraintValue::Integer(a % b),
                BinaryOp::Equal => ConstraintValue::Bool(a == b),
                BinaryOp::NotEqual => ConstraintValue::Bool(a != b),
                BinaryOp::Less => ConstraintValue::Bool(a < b),
                BinaryOp::LessEqual => ConstraintValue::Bool(a <= b),
                BinaryOp::Greater => ConstraintValue::Bool(a > b),
                BinaryOp::GreaterEqual => ConstraintValue::Bool(a >= b),
                _ => {
                    return Err(anyhow::anyhow!(
                        "Unsupported operation {:?} for integers",
                        op
                    ));
                }
            }),
            (ConstraintValue::Real(a), ConstraintValue::Real(b)) => Ok(match op {
                BinaryOp::Add => ConstraintValue::Real(a + b),
                BinaryOp::Sub => ConstraintValue::Real(a - b),
                BinaryOp::Mul => ConstraintValue::Real(a * b),
                BinaryOp::Div => ConstraintValue::Real(a / b),
                BinaryOp::Equal => ConstraintValue::Bool((a - b).abs() < self.tolerance),
                BinaryOp::NotEqual => ConstraintValue::Bool((a - b).abs() >= self.tolerance),
                BinaryOp::Less => ConstraintValue::Bool(a < b),
                BinaryOp::LessEqual => ConstraintValue::Bool(a <= b),
                BinaryOp::Greater => ConstraintValue::Bool(a > b),
                BinaryOp::GreaterEqual => ConstraintValue::Bool(a >= b),
                _ => return Err(anyhow::anyhow!("Unsupported operation {:?} for reals", op)),
            }),
            _ => Err(anyhow::anyhow!("Type mismatch in binary operation")),
        }
    }

    /// Evaluate unary operation on constraint value
    fn evaluate_unary_op(
        &self,
        op: &crate::ir::UnaryOp,
        operand: &ConstraintValue,
    ) -> Result<ConstraintValue> {
        use crate::ir::UnaryOp;

        match operand {
            ConstraintValue::Bool(b) => Ok(match op {
                UnaryOp::Not => ConstraintValue::Bool(!b),
                _ => {
                    return Err(anyhow::anyhow!(
                        "Unsupported unary operation {:?} for bool",
                        op
                    ));
                }
            }),
            ConstraintValue::Integer(i) => Ok(match op {
                UnaryOp::Negate => ConstraintValue::Integer(-i),
                UnaryOp::Abs => ConstraintValue::Integer(i.abs()),
                _ => {
                    return Err(anyhow::anyhow!(
                        "Unsupported unary operation {:?} for integer",
                        op
                    ));
                }
            }),
            ConstraintValue::Real(r) => Ok(match op {
                UnaryOp::Negate => ConstraintValue::Real(-r),
                UnaryOp::Abs => ConstraintValue::Real(r.abs()),
                _ => {
                    return Err(anyhow::anyhow!(
                        "Unsupported unary operation {:?} for real",
                        op
                    ));
                }
            }),
            _ => Err(anyhow::anyhow!(
                "Unsupported operand type for unary operation"
            )),
        }
    }

    /// Check if two values are equal (with tolerance for reals)
    fn values_equal(&self, lhs: &ConstraintValue, rhs: &ConstraintValue) -> bool {
        match (lhs, rhs) {
            (ConstraintValue::Bool(a), ConstraintValue::Bool(b)) => a == b,
            (ConstraintValue::Integer(a), ConstraintValue::Integer(b)) => a == b,
            (ConstraintValue::Real(a), ConstraintValue::Real(b)) => (a - b).abs() < self.tolerance,
            (ConstraintValue::String(a), ConstraintValue::String(b)) => a == b,
            _ => false,
        }
    }

    /// Check if lhs < rhs
    fn value_less_than(&self, lhs: &ConstraintValue, rhs: &ConstraintValue) -> Result<bool> {
        match (lhs, rhs) {
            (ConstraintValue::Integer(a), ConstraintValue::Integer(b)) => Ok(a < b),
            (ConstraintValue::Real(a), ConstraintValue::Real(b)) => Ok(a < b),
            _ => Err(anyhow::anyhow!("Cannot compare these value types")),
        }
    }
}

impl Default for BasicConstraintChecker {
    fn default() -> Self {
        Self::new(1e-9)
    }
}