//! 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)

    }

}