//! Proof tactics library with ML-powered suggestions

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

use super::prover::{ProofGoal, ProofContext, StepResult};

/// A proof tactic
pub trait Tactic: Send + Sync {
    /// Get tactic name
    fn name(&self) -> &str;
    
    /// Get tactic description
    fn description(&self) -> &str;
    
    /// Apply the tactic to a goal
    fn apply(&self, goal: &ProofGoal, args: &[&str], context: &ProofContext) -> Result<StepResult>;
    
    /// Check if tactic is applicable
    fn is_applicable(&self, goal: &ProofGoal, context: &ProofContext) -> bool;
}

/// Library of available tactics
pub struct TacticLibrary {
    /// Available tactics
    tactics: HashMap<String, Box<dyn Tactic>>,
    
    /// ML model for suggestions (placeholder)
    _suggestion_model: SuggestionModel,
}

/// ML model for tactic suggestions
struct SuggestionModel {
    // Placeholder for ML model
}

/// Tactic suggestion with confidence
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TacticSuggestion {
    /// Tactic name
    pub tactic_name: String,
    
    /// Confidence score (0.0 - 1.0)
    pub confidence: f64,
    
    /// Reason for suggestion
    pub reason: Option<String>,
    
    /// Suggested arguments
    pub arguments: Vec<String>,
}

impl TacticLibrary {
    /// Create default tactic library
    pub fn default() -> Self {
        let mut tactics = HashMap::new();
        
        // Add basic tactics
        tactics.insert("intro".to_string(), Box::new(IntroTactic) as Box<dyn Tactic>);
        tactics.insert("split".to_string(), Box::new(SplitTactic) as Box<dyn Tactic>);
        tactics.insert("induction".to_string(), Box::new(InductionTactic) as Box<dyn Tactic>);
        tactics.insert("contradiction".to_string(), Box::new(ContradictionTactic) as Box<dyn Tactic>);
        tactics.insert("reflexivity".to_string(), Box::new(ReflexivityTactic) as Box<dyn Tactic>);
        tactics.insert("simplify".to_string(), Box::new(SimplifyTactic) as Box<dyn Tactic>);
        tactics.insert("unfold".to_string(), Box::new(UnfoldTactic) as Box<dyn Tactic>);
        tactics.insert("rewrite".to_string(), Box::new(RewriteTactic) as Box<dyn Tactic>);
        tactics.insert("apply".to_string(), Box::new(ApplyTactic) as Box<dyn Tactic>);
        tactics.insert("assumption".to_string(), Box::new(AssumptionTactic) as Box<dyn Tactic>);
        
        Self {
            tactics,
            _suggestion_model: SuggestionModel {},
        }
    }
    
    /// Get all tactics
    pub fn all_tactics(&self) -> Vec<&dyn Tactic> {
        self.tactics.values().map(std::convert::AsRef::as_ref).collect()
    }
    
    /// Get a specific tactic
    pub fn get_tactic(&self, name: &str) -> Result<&dyn Tactic> {
        self.tactics.get(name)
            .map(std::convert::AsRef::as_ref)
            .ok_or_else(|| anyhow::anyhow!("Unknown tactic: {}", name))
    }
    
    /// Suggest tactics for a goal
    pub fn suggest_tactics(&self, goal: &ProofGoal, context: &ProofContext) -> Result<Vec<TacticSuggestion>> {
        let mut suggestions = Vec::new();
        
        // Check each tactic's applicability
        for (name, tactic) in &self.tactics {
            if tactic.is_applicable(goal, context) {
                let confidence = self.calculate_confidence(goal, tactic.as_ref());
                suggestions.push(TacticSuggestion {
                    tactic_name: name.clone(),
                    confidence,
                    reason: Some(format!("Pattern matches {}", tactic.description())),
                    arguments: Vec::new(),
                });
            }
        }
        
        // Sort by confidence
        suggestions.sort_by(|a, b| b.confidence.partial_cmp(&a.confidence).unwrap());
        
        Ok(suggestions)
    }
    
    /// Calculate confidence for a tactic
    fn calculate_confidence(&self, goal: &ProofGoal, _tactic: &dyn Tactic) -> f64 {
        // Simple heuristic-based confidence
        match &goal.statement {
            s if s.contains("->") => 0.8,  // Implication
            s if s.contains("&&") => 0.7,  // Conjunction
            s if s.contains("||") => 0.6,  // Disjunction
            s if s.contains("==") => 0.9,  // Equality
            _ => 0.5,
        }
    }
}

// Basic tactic implementations

/// Introduction tactic (for implications)
struct IntroTactic;

impl Tactic for IntroTactic {
    fn name(&self) -> &'static str { "intro" }
    
    fn description(&self) -> &'static str { "Introduce hypothesis from implication" }
    
    fn apply(&self, goal: &ProofGoal, _args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        if goal.statement.contains("->") {
            let parts: Vec<&str> = goal.statement.split("->").collect();
            if parts.len() == 2 {
                return Ok(StepResult::Simplified(parts[1].trim().to_string()));
            }
        }
        Ok(StepResult::Failed("Cannot apply intro".to_string()))
    }
    
    fn is_applicable(&self, goal: &ProofGoal, _context: &ProofContext) -> bool {
        goal.statement.contains("->")
    }
}

/// Split tactic (for conjunctions)
struct SplitTactic;

impl Tactic for SplitTactic {
    fn name(&self) -> &'static str { "split" }
    
    fn description(&self) -> &'static str { "Split conjunction into subgoals" }
    
    fn apply(&self, goal: &ProofGoal, _args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        if goal.statement.contains("&&") {
            let parts: Vec<&str> = goal.statement.split("&&").collect();
            let subgoals: Vec<String> = parts.iter().map(|p| p.trim().to_string()).collect();
            return Ok(StepResult::Subgoals(subgoals));
        }
        Ok(StepResult::Failed("Cannot apply split".to_string()))
    }
    
    fn is_applicable(&self, goal: &ProofGoal, _context: &ProofContext) -> bool {
        goal.statement.contains("&&")
    }
}

/// Induction tactic
struct InductionTactic;

impl Tactic for InductionTactic {
    fn name(&self) -> &'static str { "induction" }
    
    fn description(&self) -> &'static str { "Proof by induction" }
    
    fn apply(&self, goal: &ProofGoal, args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        if args.is_empty() {
            return Ok(StepResult::Failed("Induction requires a variable".to_string()));
        }
        
        let var = args[0];
        Ok(StepResult::Subgoals(vec![
            format!("Base case: {} when {} = 0", goal.statement, var),
            format!("Inductive step: {} implies {}", 
                goal.statement.replace(var, &var.to_string()),
                goal.statement.replace(var, &format!("{var}+1"))
            ),
        ]))
    }
    
    fn is_applicable(&self, goal: &ProofGoal, _context: &ProofContext) -> bool {
        goal.statement.contains("forall") || goal.statement.contains('n')
    }
}

/// Contradiction tactic
struct ContradictionTactic;

impl Tactic for ContradictionTactic {
    fn name(&self) -> &'static str { "contradiction" }
    
    fn description(&self) -> &'static str { "Proof by contradiction" }
    
    fn apply(&self, _goal: &ProofGoal, _args: &[&str], context: &ProofContext) -> Result<StepResult> {
        // Check for contradictory assumptions
        for assumption in &context.assumptions {
            if assumption.contains('!') {
                let negated = assumption.replace('!', "");
                if context.assumptions.contains(&negated) {
                    return Ok(StepResult::Solved);
                }
            }
        }
        Ok(StepResult::Failed("No contradiction found".to_string()))
    }
    
    fn is_applicable(&self, _goal: &ProofGoal, context: &ProofContext) -> bool {
        context.assumptions.len() >= 2
    }
}

/// Reflexivity tactic
struct ReflexivityTactic;

impl Tactic for ReflexivityTactic {
    fn name(&self) -> &'static str { "reflexivity" }
    
    fn description(&self) -> &'static str { "Prove equality by reflexivity" }
    
    fn apply(&self, goal: &ProofGoal, _args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        if goal.statement.contains("==") {
            let parts: Vec<&str> = goal.statement.split("==").collect();
            if parts.len() == 2 && parts[0].trim() == parts[1].trim() {
                return Ok(StepResult::Solved);
            }
        }
        Ok(StepResult::Failed("Terms are not equal".to_string()))
    }
    
    fn is_applicable(&self, goal: &ProofGoal, _context: &ProofContext) -> bool {
        goal.statement.contains("==")
    }
}

/// Simplify tactic
struct SimplifyTactic;

impl Tactic for SimplifyTactic {
    fn name(&self) -> &'static str { "simplify" }
    
    fn description(&self) -> &'static str { "Simplify expression" }
    
    fn apply(&self, goal: &ProofGoal, _args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        let mut simplified = goal.statement.clone();
        
        // Basic simplifications
        simplified = simplified.replace("true && ", "");
        simplified = simplified.replace(" && true", "");
        simplified = simplified.replace("false || ", "");
        simplified = simplified.replace(" || false", "");
        simplified = simplified.replace("!!!", "!");
        simplified = simplified.replace("!!", "");
        
        if simplified == goal.statement {
            Ok(StepResult::Failed("No simplification possible".to_string()))
        } else {
            Ok(StepResult::Simplified(simplified))
        }
    }
    
    fn is_applicable(&self, _goal: &ProofGoal, _context: &ProofContext) -> bool {
        true
    }
}

/// Unfold tactic
struct UnfoldTactic;

impl Tactic for UnfoldTactic {
    fn name(&self) -> &'static str { "unfold" }
    
    fn description(&self) -> &'static str { "Unfold definition" }
    
    fn apply(&self, goal: &ProofGoal, args: &[&str], context: &ProofContext) -> Result<StepResult> {
        if args.is_empty() {
            return Ok(StepResult::Failed("Unfold requires a definition name".to_string()));
        }
        
        let def_name = args[0];
        if let Some(definition) = context.definitions.get(def_name) {
            let unfolded = goal.statement.replace(def_name, definition);
            Ok(StepResult::Simplified(unfolded))
        } else {
            Ok(StepResult::Failed(format!("Unknown definition: {def_name}")))
        }
    }
    
    fn is_applicable(&self, _goal: &ProofGoal, context: &ProofContext) -> bool {
        !context.definitions.is_empty()
    }
}

/// Rewrite tactic
struct RewriteTactic;

impl Tactic for RewriteTactic {
    fn name(&self) -> &'static str { "rewrite" }
    
    fn description(&self) -> &'static str { "Rewrite using equality" }
    
    fn apply(&self, goal: &ProofGoal, args: &[&str], context: &ProofContext) -> Result<StepResult> {
        if args.is_empty() {
            return Ok(StepResult::Failed("Rewrite requires an equality".to_string()));
        }
        
        // Find equality in assumptions
        for assumption in &context.assumptions {
            if assumption.contains("==") {
                let parts: Vec<&str> = assumption.split("==").collect();
                if parts.len() == 2 {
                    let lhs = parts[0].trim();
                    let rhs = parts[1].trim();
                    let rewritten = goal.statement.replace(lhs, rhs);
                    if rewritten != goal.statement {
                        return Ok(StepResult::Simplified(rewritten));
                    }
                }
            }
        }
        
        Ok(StepResult::Failed("No applicable rewrite found".to_string()))
    }
    
    fn is_applicable(&self, _goal: &ProofGoal, context: &ProofContext) -> bool {
        context.assumptions.iter().any(|a| a.contains("=="))
    }
}

/// Apply tactic
struct ApplyTactic;

impl Tactic for ApplyTactic {
    fn name(&self) -> &'static str { "apply" }
    
    fn description(&self) -> &'static str { "Apply theorem or lemma" }
    
    fn apply(&self, _goal: &ProofGoal, args: &[&str], _context: &ProofContext) -> Result<StepResult> {
        if args.is_empty() {
            return Ok(StepResult::Failed("Apply requires a theorem name".to_string()));
        }
        
        // In a real implementation, this would look up theorems
        Ok(StepResult::Failed(format!("Cannot apply theorem: {}", args[0])))
    }
    
    fn is_applicable(&self, _goal: &ProofGoal, _context: &ProofContext) -> bool {
        true
    }
}

/// Assumption tactic
struct AssumptionTactic;

impl Tactic for AssumptionTactic {
    fn name(&self) -> &'static str { "assumption" }
    
    fn description(&self) -> &'static str { "Prove using an assumption" }
    
    fn apply(&self, goal: &ProofGoal, _args: &[&str], context: &ProofContext) -> Result<StepResult> {
        if context.assumptions.contains(&goal.statement) {
            Ok(StepResult::Solved)
        } else {
            Ok(StepResult::Failed("Goal not in assumptions".to_string()))
        }
    }
    
    fn is_applicable(&self, goal: &ProofGoal, context: &ProofContext) -> bool {
        context.assumptions.contains(&goal.statement)
    }
}