//! Simplified interactive theorem prover

use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

use super::smt::SmtBackend;
use super::tactics::TacticLibrary;

/// Interactive prover
pub struct InteractiveProver {
    _backend: SmtBackend,
    tactics: TacticLibrary,
    timeout: u64,
    ml_suggestions: bool,
}

impl InteractiveProver {
    /// Create new prover
    pub fn new(backend: SmtBackend) -> Self {
        Self {
            _backend: backend,
            tactics: TacticLibrary::default(),
            timeout: 5000,
            ml_suggestions: false,
        }
    }
    
    /// Set timeout
    pub fn set_timeout(&mut self, timeout: u64) {
        self.timeout = timeout;
    }
    
    /// Enable ML suggestions
    pub fn set_ml_suggestions(&mut self, enabled: bool) {
        self.ml_suggestions = enabled;
    }
    
    /// Load proof script
    pub fn load_script(&mut self, _script: &str) -> Result<()> {
        // Simplified: just return ok
        Ok(())
    }
    
    /// Get available tactics
    pub fn get_available_tactics(&self) -> Vec<&dyn super::tactics::Tactic> {
        self.tactics.all_tactics()
    }
    
    /// Apply tactic
    pub fn apply_tactic(&mut self, session: &mut ProverSession, tactic_name: &str, args: &[&str]) -> Result<ProofResult> {
        let tactic = self.tactics.get_tactic(tactic_name)?;
        
        if let Some(goal) = session.current_goal() {
            let result = tactic.apply(goal, args, &session.context)?;
            match result {
                StepResult::Solved => {
                    session.complete_goal();
                    Ok(ProofResult::Solved)
                }
                StepResult::Simplified(new_goal) => {
                    session.update_goal(new_goal);
                    Ok(ProofResult::Progress)
                }
                StepResult::Subgoals(subgoals) => {
                    session.replace_with_subgoals(subgoals);
                    Ok(ProofResult::Progress)
                }
                StepResult::Failed(msg) => {
                    Ok(ProofResult::Failed(msg))
                }
            }
        } else {
            Ok(ProofResult::Failed("No active goal".to_string()))
        }
    }
    
    /// Process input
    pub fn process_input(&mut self, session: &mut ProverSession, input: &str) -> Result<ProofResult> {
        // Try to parse as goal
        if let Some(goal) = input.strip_prefix("prove ") {
            session.add_goal(goal.to_string());
            return Ok(ProofResult::Progress);
        }
        
        // Try as tactic
        let parts: Vec<&str> = input.split_whitespace().collect();
        if !parts.is_empty() {
            let tactic_name = parts[0];
            let args = &parts[1..];
            return self.apply_tactic(session, tactic_name, args);
        }
        
        Ok(ProofResult::Failed("Unknown command".to_string()))
    }
    
    /// Suggest tactics
    pub fn suggest_tactics(&self, goal: &ProofGoal) -> Result<Vec<super::tactics::TacticSuggestion>> {
        self.tactics.suggest_tactics(goal, &ProofContext::new())
    }
}

/// Prover session
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProverSession {
    goals: Vec<ProofGoal>,
    context: ProofContext,
    history: Vec<String>,
}

impl ProverSession {
    /// Create new session
    pub fn new() -> Self {
        Self {
            goals: Vec::new(),
            context: ProofContext::new(),
            history: Vec::new(),
        }
    }
    
    /// Add goal
    pub fn add_goal(&mut self, statement: String) {
        self.goals.push(ProofGoal { statement });
    }
    
    /// Get current goal
    pub fn current_goal(&self) -> Option<&ProofGoal> {
        self.goals.first()
    }
    
    /// Update current goal
    pub fn update_goal(&mut self, statement: String) {
        if !self.goals.is_empty() {
            self.goals[0].statement = statement;
        }
    }
    
    /// Complete current goal
    pub fn complete_goal(&mut self) {
        if !self.goals.is_empty() {
            self.goals.remove(0);
        }
    }
    
    /// Replace with subgoals
    pub fn replace_with_subgoals(&mut self, subgoals: Vec<String>) {
        if !self.goals.is_empty() {
            self.goals.remove(0);
            for subgoal in subgoals.into_iter().rev() {
                self.goals.insert(0, ProofGoal { statement: subgoal });
            }
        }
    }
    
    /// Get all goals
    pub fn get_goals(&self) -> &[ProofGoal] {
        &self.goals
    }
    
    /// Check if complete
    pub fn is_complete(&self) -> bool {
        self.goals.is_empty()
    }
    
    /// Export to text
    pub fn to_text_proof(&self) -> String {
        let mut proof = String::new();
        proof.push_str("Proof:\n");
        for line in &self.history {
            use std::fmt::Write;
            let _ = writeln!(proof, "  {line}");
        }
        if self.is_complete() {
            proof.push_str("Qed.\n");
        }
        proof
    }
    
    /// Export to Coq
    pub fn to_coq_proof(&self) -> String {
        self.to_text_proof() // Simplified
    }
    
    /// Export to Lean
    pub fn to_lean_proof(&self) -> String {
        self.to_text_proof() // Simplified
    }
}

impl Default for ProverSession {
    fn default() -> Self {
        Self::new()
    }
}

/// Proof goal
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProofGoal {
    pub statement: String,
}

/// Proof context
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProofContext {
    pub assumptions: Vec<String>,
    pub definitions: HashMap<String, String>,
}

impl ProofContext {
    /// Create new context
    pub fn new() -> Self {
        Self {
            assumptions: Vec::new(),
            definitions: HashMap::new(),
        }
    }
}

impl Default for ProofContext {
    fn default() -> Self {
        Self::new()
    }
}

/// Proof result
#[derive(Debug)]
pub enum ProofResult {
    Solved,
    Progress,
    Failed(String),
}

/// Step result from tactic application
#[derive(Debug, Clone)]
pub enum StepResult {
    /// Goal was solved
    Solved,
    
    /// Goal was simplified to new goal
    Simplified(String),
    
    /// Goal was split into subgoals
    Subgoals(Vec<String>),
    
    /// Tactic failed
    Failed(String),
}