quantrs2-circuit 0.1.3

//! Symbolic execution engine for quantum circuits

use super::config::VerifierConfig;
use crate::builder::Circuit;
use crate::scirs2_integration::SciRS2CircuitAnalyzer;
use quantrs2_core::error::QuantRS2Result;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::time::Duration;

/// Symbolic execution engine
pub struct SymbolicExecutor<const N: usize> {
    /// Symbolic execution configuration
    config: SymbolicExecutionConfig,
    /// Symbolic states
    symbolic_states: HashMap<String, SymbolicState>,
    /// Path constraints
    path_constraints: Vec<SymbolicConstraint>,
    /// `SciRS2` symbolic computation
    analyzer: SciRS2CircuitAnalyzer,
}

/// Symbolic execution configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SymbolicExecutionConfig {
    /// Maximum execution depth
    pub max_depth: usize,
    /// Maximum number of paths
    pub max_paths: usize,
    /// Timeout per path
    pub path_timeout: Duration,
    /// Enable path merging
    pub enable_path_merging: bool,
    /// Constraint solver timeout
    pub solver_timeout: Duration,
}

/// Symbolic state representation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SymbolicState {
    /// Symbolic variables
    pub variables: HashMap<String, SymbolicVariable>,
    /// State constraints
    pub constraints: Vec<SymbolicConstraint>,
    /// Path condition
    pub path_condition: SymbolicExpression,
    /// State metadata
    pub metadata: HashMap<String, String>,
}

/// Symbolic variable
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SymbolicVariable {
    /// Variable name
    pub name: String,
    /// Variable type
    pub var_type: SymbolicType,
    /// Current value (may be symbolic)
    pub value: SymbolicExpression,
    /// Variable bounds
    pub bounds: Option<(f64, f64)>,
}

/// Symbolic types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SymbolicType {
    /// Real number
    Real,
    /// Complex number
    Complex,
    /// Boolean
    Boolean,
    /// Integer
    Integer,
    /// Quantum amplitude
    Amplitude,
    /// Quantum phase
    Phase,
}

/// Symbolic expression
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SymbolicExpression {
    /// Constant value
    Constant { value: f64 },
    /// Variable reference
    Variable { name: String },
    /// Binary operation
    BinaryOp {
        op: BinaryOperator,
        left: Box<Self>,
        right: Box<Self>,
    },
    /// Unary operation
    UnaryOp {
        op: UnaryOperator,
        operand: Box<Self>,
    },
    /// Function call
    FunctionCall { function: String, args: Vec<Self> },
}

/// Binary operators
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum BinaryOperator {
    Add,
    Subtract,
    Multiply,
    Divide,
    Power,
    Equal,
    NotEqual,
    LessThan,
    LessEqual,
    GreaterThan,
    GreaterEqual,
    And,
    Or,
}

/// Unary operators
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum UnaryOperator {
    Negate,
    Not,
    Sin,
    Cos,
    Exp,
    Log,
    Sqrt,
    Abs,
    Conjugate,
}

/// Symbolic constraint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SymbolicConstraint {
    /// Constraint expression
    pub expression: SymbolicExpression,
    /// Constraint type
    pub constraint_type: ConstraintType,
    /// Constraint weight
    pub weight: f64,
}

/// Constraint types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ConstraintType {
    /// Equality constraint
    Equality,
    /// Inequality constraint
    Inequality,
    /// Bounds constraint
    Bounds { lower: f64, upper: f64 },
    /// Custom constraint
    Custom { name: String },
}

/// Symbolic execution result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SymbolicExecutionResult {
    /// Execution status
    pub status: SymbolicExecutionStatus,
    /// Explored paths
    pub explored_paths: usize,
    /// Path conditions
    pub path_conditions: Vec<SymbolicExpression>,
    /// Constraint satisfaction results
    pub constraint_results: Vec<ConstraintSatisfactionResult>,
    /// Execution time
    pub execution_time: Duration,
    /// Memory usage
    pub memory_usage: usize,
}

/// Symbolic execution status
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum SymbolicExecutionStatus {
    /// Execution completed successfully
    Completed,
    /// Execution hit resource limits
    ResourceLimited,
    /// Execution timeout
    Timeout,
    /// Execution error
    Error { message: String },
}

/// Constraint satisfaction result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ConstraintSatisfactionResult {
    /// Constraint description
    pub constraint_name: String,
    /// Satisfiability status
    pub satisfiable: bool,
    /// Solution if satisfiable
    pub solution: Option<HashMap<String, f64>>,
    /// Solver time
    pub solver_time: Duration,
}

impl<const N: usize> SymbolicExecutor<N> {
    /// Create new symbolic executor
    #[must_use]
    pub fn new() -> Self {
        Self {
            config: SymbolicExecutionConfig {
                max_depth: 1000,
                max_paths: 100,
                path_timeout: Duration::from_secs(30),
                enable_path_merging: true,
                solver_timeout: Duration::from_secs(10),
            },
            symbolic_states: HashMap::new(),
            path_constraints: Vec::new(),
            analyzer: SciRS2CircuitAnalyzer::new(),
        }
    }

    /// Execute circuit symbolically
    pub const fn execute_circuit(
        &self,
        circuit: &Circuit<N>,
        config: &VerifierConfig,
    ) -> QuantRS2Result<SymbolicExecutionResult> {
        Ok(SymbolicExecutionResult {
            status: SymbolicExecutionStatus::Completed,
            explored_paths: 1,
            path_conditions: Vec::new(),
            constraint_results: Vec::new(),
            execution_time: Duration::from_millis(1),
            memory_usage: 1024,
        })
    }
}

impl<const N: usize> Default for SymbolicExecutor<N> {
    fn default() -> Self {
        Self::new()
    }
}