// SPRINT6-005: Full Z3 SMT solver integration
// PMAT Complexity: <10 per function
use std::collections::HashMap;
use std::io::Write;
use std::process::{Command, Stdio};
use std::time::Duration;
/// SMT solver integration for formal verification
pub struct SmtSolver {
    solver_type: SolverType,
    timeout: Duration,
    proof_cache: ProofCache,
}
#[derive(Debug, Clone)]
pub enum SolverType {
    Z3,
    CVC4,
    Yices,
    Vampire,
}
#[derive(Debug, Clone)]
pub struct SmtQuery {
    pub declarations: Vec<String>,
    pub assertions: Vec<String>,
    pub query: String,
}
#[derive(Debug, Clone)]
pub enum SmtResult {
    Satisfiable(Model),
    Unsatisfiable(Proof),
    Unknown(String),
    Timeout,
}
#[derive(Debug, Clone)]
pub struct Model {
    pub assignments: HashMap<String, String>,
}
#[derive(Debug, Clone)]
pub struct Proof {
    pub steps: Vec<String>,
    pub conclusion: String,
}
/// Cache for SMT proof results
pub struct ProofCache {
    cache: HashMap<String, CachedProof>,
    hit_count: usize,
    miss_count: usize,
}
#[derive(Debug, Clone)]
struct CachedProof {
    query_hash: String,
    result: SmtResult,
    timestamp: std::time::SystemTime,
}
impl SmtSolver {
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::SmtSolver;
    ///
    /// let instance = SmtSolver::new();
    /// // Verify behavior
    /// ```
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::SmtSolver;
    ///
    /// let instance = SmtSolver::new();
    /// // Verify behavior
    /// ```
    pub fn new(solver_type: SolverType) -> Self {
        Self {
            solver_type,
            timeout: Duration::from_secs(5),
            proof_cache: ProofCache::new(),
        }
    }
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::SmtSolver;
    ///
    /// let mut instance = SmtSolver::new();
    /// let result = instance.with_timeout();
    /// // Verify behavior
    /// ```
    pub fn with_timeout(solver_type: SolverType, timeout: Duration) -> Self {
        Self {
            solver_type,
            timeout,
            proof_cache: ProofCache::new(),
        }
    }
    /// Solve an SMT query
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::SmtSolver;
    ///
    /// let mut instance = SmtSolver::new();
    /// let result = instance.solve();
    /// // Verify behavior
    /// ```
    pub fn solve(&mut self, query: &SmtQuery) -> SmtResult {
        let query_string = self.format_query(query);
        let query_hash = self.calculate_hash(&query_string);
        // Check cache first
        if let Some(cached) = self.proof_cache.get(&query_hash) {
            return cached;
        }
        // Solve with external solver
        let result = match self.solver_type {
            SolverType::Z3 => self.solve_with_z3(&query_string),
            SolverType::CVC4 => self.solve_with_cvc4(&query_string),
            SolverType::Yices => self.solve_with_yices(&query_string),
            SolverType::Vampire => self.solve_with_vampire(&query_string),
        };
        // Cache result
        self.proof_cache.store(query_hash, result.clone());
        result
    }
    /// Verify a function against its specification
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::SmtSolver;
    ///
    /// let mut instance = SmtSolver::new();
    /// let result = instance.verify_function();
    /// // Verify behavior
    /// ```
    pub fn verify_function(
        &mut self,
        function: &Function,
        spec: &FunctionSpec,
    ) -> VerificationResult {
        let mut assertions = Vec::new();
        // Add function definition
        assertions.push(self.encode_function(function));
        // Add preconditions
        for precond in &spec.preconditions {
            assertions.push(format!("(assert {precond})"));
        }
        // Verify each postcondition
        let mut results = Vec::new();
        for postcond in &spec.postconditions {
            // Query: can postcondition be false?
            let query = SmtQuery {
                declarations: self.generate_declarations(function),
                assertions: assertions.clone(),
                query: format!("(assert (not {postcond}))"),
            };
            match self.solve(&query) {
                SmtResult::Unsatisfiable(_) => {
                    results.push(PostconditionResult::Satisfied(postcond.clone()));
                }
                SmtResult::Satisfiable(model) => {
                    results.push(PostconditionResult::Violated {
                        postcondition: postcond.clone(),
                        counterexample: model,
                    });
                }
                SmtResult::Timeout => {
                    results.push(PostconditionResult::Timeout(postcond.clone()));
                }
                SmtResult::Unknown(reason) => {
                    results.push(PostconditionResult::Unknown {
                        postcondition: postcond.clone(),
                        reason,
                    });
                }
            }
        }
        VerificationResult {
            function_name: function.name.clone(),
            results,
            verification_time: Duration::from_millis(100), // Would measure actual time
        }
    }
    /// Verify loop invariants
    /// # Examples
    ///
    /// ```ignore
    /// use ruchy::notebook::testing::smt::verify_loop_invariant;
    ///
    /// let result = verify_loop_invariant("example");
    /// assert_eq!(result, Ok(()));
    /// ```
    pub fn verify_loop_invariant(
        &mut self,
        loop_info: &LoopInfo,
        invariant: &str,
    ) -> LoopVerificationResult {
        // Initialization: invariant holds before loop
        let init_query = SmtQuery {
            declarations: loop_info.variable_declarations.clone(),
            assertions: vec![
                loop_info.precondition.clone(),
                format!("(assert (not {}))", invariant),
            ],
            query: "(check-sat)".to_string(),
        };
        let init_valid = matches!(self.solve(&init_query), SmtResult::Unsatisfiable(_));
        // Maintenance: if invariant holds and loop condition true, invariant still holds after iteration
        let maintain_query = SmtQuery {
            declarations: loop_info.variable_declarations.clone(),
            assertions: vec![
                format!("(assert {})", invariant),
                format!("(assert {})", loop_info.loop_condition),
                loop_info.loop_body.clone(),
                format!("(assert (not {}))", invariant.replace('x', "x_next")), // After transformation
            ],
            query: "(check-sat)".to_string(),
        };
        let maintain_valid = matches!(self.solve(&maintain_query), SmtResult::Unsatisfiable(_));
        // Termination: loop eventually terminates
        let termination_valid = self.verify_termination(loop_info);
        LoopVerificationResult {
            initialization_valid: init_valid,
            maintenance_valid: maintain_valid,
            termination_valid,
            invariant: invariant.to_string(),
        }
    }
    fn solve_with_z3(&self, query: &str) -> SmtResult {
        let mut cmd = Command::new("z3")
            .args(["-in", "-t:5000"]) // 5 second timeout
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .stderr(Stdio::piped())
            .spawn()
            .unwrap_or_else(|_| {
                // Fallback: return empty child process that will be handled below
                std::process::Command::new("echo").spawn().unwrap()
            });
        // Send query to solver
        if let Some(stdin) = cmd.stdin.as_mut() {
            stdin.write_all(query.as_bytes()).ok();
        }
        // Get response
        let output = cmd.wait_with_output().unwrap();
        let response = String::from_utf8_lossy(&output.stdout);
        self.parse_solver_response(&response)
    }
    fn solve_with_cvc4(&self, query: &str) -> SmtResult {
        // Similar to Z3 but with CVC4-specific flags
        self.simulate_solver_response(query)
    }
    fn solve_with_yices(&self, query: &str) -> SmtResult {
        // Similar to Z3 but with Yices-specific format
        self.simulate_solver_response(query)
    }
    fn solve_with_vampire(&self, query: &str) -> SmtResult {
        // First-order logic theorem prover
        self.simulate_solver_response(query)
    }
    fn simulate_solver_response(&self, query: &str) -> SmtResult {
        // Simulate solver behavior for testing
        if query.contains("(assert false)") {
            SmtResult::Unsatisfiable(Proof {
                steps: vec!["(assert false) is unsatisfiable".to_string()],
                conclusion: "contradiction".to_string(),
            })
        } else if query.contains("unknown_function") {
            SmtResult::Unknown("Unknown function symbol".to_string())
        } else {
            SmtResult::Satisfiable(Model {
                assignments: vec![
                    ("x".to_string(), "42".to_string()),
                    ("y".to_string(), "true".to_string()),
                ]
                .into_iter()
                .collect(),
            })
        }
    }
    fn parse_solver_response(&self, response: &str) -> SmtResult {
        let response = response.trim();
        if response.starts_with("sat") {
            // Parse model
            let mut assignments = HashMap::new();
            for line in response.lines().skip(1) {
                if line.contains("->") {
                    let parts: Vec<&str> = line.split("->").collect();
                    if parts.len() == 2 {
                        assignments
                            .insert(parts[0].trim().to_string(), parts[1].trim().to_string());
                    }
                }
            }
            SmtResult::Satisfiable(Model { assignments })
        } else if response.starts_with("unsat") {
            SmtResult::Unsatisfiable(Proof {
                steps: vec!["Proof by contradiction".to_string()],
                conclusion: "unsatisfiable".to_string(),
            })
        } else if response.starts_with("timeout") {
            SmtResult::Timeout
        } else {
            SmtResult::Unknown(response.to_string())
        }
    }
    fn format_query(&self, query: &SmtQuery) -> String {
        let mut result = String::new();
        // Add declarations
        for decl in &query.declarations {
            result.push_str(&format!("{decl}\n"));
        }
        // Add assertions
        for assertion in &query.assertions {
            result.push_str(&format!("{assertion}\n"));
        }
        // Add query
        result.push_str(&format!("{}\n", query.query));
        result
    }
    fn encode_function(&self, function: &Function) -> String {
        // Simplified function encoding
        format!(
            "(define-fun {} ({}) {} {})",
            function.name,
            function.parameters.join(" "),
            function.return_type,
            function.body_smt
        )
    }
    fn generate_declarations(&self, function: &Function) -> Vec<String> {
        let mut decls = Vec::new();
        // Declare function
        decls.push(format!(
            "(declare-fun {} ({}) {})",
            function.name,
            function.parameter_types.join(" "),
            function.return_type
        ));
        // Declare variables
        for param in &function.parameters {
            decls.push(format!("(declare-const {param} Int)")); // Simplified as Int
        }
        decls
    }
    fn verify_termination(&mut self, loop_info: &LoopInfo) -> bool {
        // Check if there's a decreasing measure
        if let Some(measure) = &loop_info.termination_measure {
            let query = SmtQuery {
                declarations: loop_info.variable_declarations.clone(),
                assertions: vec![
                    format!("(assert {})", loop_info.loop_condition),
                    loop_info.loop_body.clone(),
                    format!(
                        "(assert (>= {} {}))",
                        measure,
                        measure.replace('x', "x_next")
                    ),
                ],
                query: "(check-sat)".to_string(),
            };
            matches!(self.solve(&query), SmtResult::Unsatisfiable(_))
        } else {
            false // Can't prove termination without measure
        }
    }
    fn calculate_hash(&self, content: &str) -> String {
        use sha2::{Digest, Sha256};
        let mut hasher = Sha256::new();
        hasher.update(content);
        format!("{:x}", hasher.finalize())
    }
}
impl ProofCache {
    fn new() -> Self {
        Self {
            cache: HashMap::new(),
            hit_count: 0,
            miss_count: 0,
        }
    }
    fn get(&mut self, query_hash: &str) -> Option<SmtResult> {
        if let Some(cached) = self.cache.get(query_hash) {
            // Check if cache entry is still valid (not too old)
            if let Ok(elapsed) = cached.timestamp.elapsed() {
                if elapsed < Duration::from_secs(24 * 60 * 60) {
                    self.hit_count += 1;
                    return Some(cached.result.clone());
                }
            }
        }
        self.miss_count += 1;
        None
    }
    fn store(&mut self, query_hash: String, result: SmtResult) {
        self.cache.insert(
            query_hash.clone(),
            CachedProof {
                query_hash,
                result,
                timestamp: std::time::SystemTime::now(),
            },
        );
    }
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::ProofCache;
    ///
    /// let mut instance = ProofCache::new();
    /// let result = instance.get_hit_rate();
    /// // Verify behavior
    /// ```
    pub fn get_hit_rate(&self) -> f64 {
        let total = self.hit_count + self.miss_count;
        if total > 0 {
            self.hit_count as f64 / total as f64
        } else {
            0.0
        }
    }
}
// Supporting types
#[derive(Debug, Clone)]
pub struct Function {
    pub name: String,
    pub parameters: Vec<String>,
    pub parameter_types: Vec<String>,
    pub return_type: String,
    pub body_smt: String,
}
#[derive(Debug, Clone)]
pub struct FunctionSpec {
    pub preconditions: Vec<String>,
    pub postconditions: Vec<String>,
}
#[derive(Debug)]
pub struct VerificationResult {
    pub function_name: String,
    pub results: Vec<PostconditionResult>,
    pub verification_time: Duration,
}
#[derive(Debug)]
pub enum PostconditionResult {
    Satisfied(String),
    Violated {
        postcondition: String,
        counterexample: Model,
    },
    Timeout(String),
    Unknown {
        postcondition: String,
        reason: String,
    },
}
#[derive(Debug, Clone)]
pub struct LoopInfo {
    pub variable_declarations: Vec<String>,
    pub precondition: String,
    pub loop_condition: String,
    pub loop_body: String,
    pub termination_measure: Option<String>,
}
#[derive(Debug)]
pub struct LoopVerificationResult {
    pub initialization_valid: bool,
    pub maintenance_valid: bool,
    pub termination_valid: bool,
    pub invariant: String,
}
/// Bounded model checker for finding counterexamples
pub struct BoundedModelChecker {
    solver: SmtSolver,
    max_depth: usize,
}
impl BoundedModelChecker {
    pub fn new(solver_type: SolverType, max_depth: usize) -> Self {
        Self {
            solver: SmtSolver::new(solver_type),
            max_depth,
        }
    }
    /// Check property up to bounded depth
    /// # Examples
    ///
    /// ```
    /// use ruchy::notebook::testing::smt::BoundedModelChecker;
    ///
    /// let mut instance = BoundedModelChecker::new();
    /// let result = instance.check_bounded();
    /// // Verify behavior
    /// ```
    pub fn check_bounded(&mut self, property: &str, program: &Program) -> BoundedResult {
        for depth in 1..=self.max_depth {
            let unrolled = self.unroll_program(program, depth);
            let query = SmtQuery {
                declarations: program.variable_declarations.clone(),
                assertions: vec![unrolled, format!("(assert (not {}))", property)],
                query: "(check-sat)".to_string(),
            };
            match self.solver.solve(&query) {
                SmtResult::Satisfiable(model) => {
                    return BoundedResult::CounterExample { depth, model };
                }
                SmtResult::Unsatisfiable(_) => {
                    // Property holds at this depth, continue
                }
                SmtResult::Timeout => {
                    return BoundedResult::Timeout {
                        reached_depth: depth,
                    };
                }
                SmtResult::Unknown(reason) => {
                    return BoundedResult::Unknown { reason, depth };
                }
            }
        }
        BoundedResult::BoundedSafe {
            max_depth: self.max_depth,
        }
    }
    fn unroll_program(&self, _program: &Program, depth: usize) -> String {
        // Unroll loops and function calls up to specified depth
        let mut unrolled = String::new();
        for step in 0..depth {
            unrolled.push_str(&format!("(assert (= x_{} (f x_{})))\n", step + 1, step));
        }
        unrolled
    }
}
#[derive(Debug)]
pub enum BoundedResult {
    CounterExample { depth: usize, model: Model },
    BoundedSafe { max_depth: usize },
    Timeout { reached_depth: usize },
    Unknown { reason: String, depth: usize },
}
#[derive(Debug)]
pub struct Program {
    pub variable_declarations: Vec<String>,
    pub statements: Vec<String>,
}
trait DurationExt {
    fn from_hours(hours: u64) -> Duration;
}
impl DurationExt for Duration {
    fn from_hours(hours: u64) -> Duration {
        Duration::from_secs(hours * 3600)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::HashMap;

    #[test]
    fn test_smt_solver_new() {
        let _solver = SmtSolver::new(SolverType::Z3);
        // Constructor test - should create without panic
        assert!(true);
    }

    #[test]
    fn test_smt_solver_with_timeout() {
        let timeout = Duration::from_secs(30);
        let _solver = SmtSolver::with_timeout(SolverType::Z3, timeout);
        // Constructor with timeout should work
        assert!(true);
    }

    #[test]
    fn test_solve_simple_query() {
        let mut solver = SmtSolver::new(SolverType::Z3);
        let query = SmtQuery {
            declarations: vec!["(declare-fun x () Int)".to_string()],
            assertions: vec!["(assert (> x 0))".to_string()],
            query: "(check-sat)".to_string(),
        };

        let result = solver.solve(&query);
        // Should return some result
        match result {
            SmtResult::Satisfiable(_) => assert!(true),
            SmtResult::Unsatisfiable(_) => assert!(true),
            SmtResult::Unknown(_) => assert!(true),
            SmtResult::Timeout => assert!(true),
        }
    }

    #[test]
    fn test_verify_function_basic() {
        let mut solver = SmtSolver::new(SolverType::Z3);
        let function = Function {
            name: "add_one".to_string(),
            parameters: vec!["x".to_string()],
            parameter_types: vec!["Int".to_string()],
            return_type: "Int".to_string(),
            body_smt: "(+ x 1)".to_string(),
        };

        let spec = FunctionSpec {
            preconditions: vec!["(> x 0)".to_string()],
            postconditions: vec!["(> result 0)".to_string()],
        };

        let result = solver.verify_function(&function, &spec);
        assert_eq!(result.function_name, "add_one");
    }

    #[test]
    fn test_verify_loop_invariant() {
        let mut solver = SmtSolver::new(SolverType::Z3);
        let loop_info = LoopInfo {
            variable_declarations: vec![
                "(declare-fun i () Int)".to_string(),
                "(declare-fun n () Int)".to_string(),
            ],
            precondition: "(and (= i 0) (>= n 0))".to_string(),
            loop_condition: "(< i n)".to_string(),
            loop_body: "(= i_next (+ i 1))".to_string(),
            termination_measure: Some("(- n i)".to_string()),
        };

        let invariant = "(and (>= i 0) (<= i n))";
        let result = solver.verify_loop_invariant(&loop_info, invariant);
        assert_eq!(result.invariant, invariant);
    }

    #[test]
    fn test_smt_query_creation() {
        let query = SmtQuery {
            declarations: vec!["(declare-fun x () Int)".to_string()],
            assertions: vec!["(assert (> x 0))".to_string()],
            query: "(check-sat)".to_string(),
        };

        assert_eq!(query.declarations.len(), 1);
        assert_eq!(query.assertions.len(), 1);
        assert_eq!(query.query, "(check-sat)");
    }

    #[test]
    fn test_model_creation() {
        let mut assignments = HashMap::new();
        assignments.insert("x".to_string(), "5".to_string());
        assignments.insert("y".to_string(), "10".to_string());

        let model = Model { assignments };

        assert_eq!(model.assignments.len(), 2);
        assert_eq!(model.assignments.get("x"), Some(&"5".to_string()));
    }

    #[test]
    fn test_proof_creation() {
        let proof = Proof {
            steps: vec![
                "step 1: assume x > 0".to_string(),
                "step 2: derive y > 0".to_string(),
            ],
            conclusion: "therefore x + y > 0".to_string(),
        };

        assert_eq!(proof.steps.len(), 2);
        assert!(!proof.conclusion.is_empty());
    }

    #[test]
    fn test_solver_type_variants() {
        let types = [
            SolverType::Z3,
            SolverType::CVC4,
            SolverType::Yices,
            SolverType::Vampire,
        ];

        assert_eq!(types.len(), 4);
    }

    #[test]
    fn test_function_creation() {
        let function = Function {
            name: "add_one".to_string(),
            parameters: vec!["x".to_string()],
            parameter_types: vec!["Int".to_string()],
            return_type: "Int".to_string(),
            body_smt: "(+ x 1)".to_string(),
        };

        assert_eq!(function.name, "add_one");
        assert_eq!(function.parameters.len(), 1);
    }

    #[test]
    fn test_function_spec_creation() {
        let spec = FunctionSpec {
            preconditions: vec!["(> x 0)".to_string()],
            postconditions: vec!["(> result 0)".to_string()],
        };

        assert_eq!(spec.preconditions.len(), 1);
        assert_eq!(spec.postconditions.len(), 1);
    }

    #[test]
    fn test_loop_info_creation() {
        let loop_info = LoopInfo {
            variable_declarations: vec![
                "(declare-fun i () Int)".to_string(),
                "(declare-fun n () Int)".to_string(),
            ],
            precondition: "(and (= i 0) (>= n 0))".to_string(),
            loop_condition: "(< i n)".to_string(),
            loop_body: "(= i_next (+ i 1))".to_string(),
            termination_measure: Some("(- n i)".to_string()),
        };

        assert_eq!(loop_info.variable_declarations.len(), 2);
        assert!(loop_info.termination_measure.is_some());
    }

    #[test]
    fn test_bounded_model_checker_new() {
        let _checker = BoundedModelChecker::new(SolverType::Z3, 10);
        // Constructor should work
        assert!(true);
    }

    #[test]
    fn test_duration_ext() {
        let duration = Duration::from_hours(2);
        assert_eq!(duration, Duration::from_secs(7200));
    }
}
