/// Custom lint rules for Ruchy code quality

use crate::frontend::ast::{Expr, ExprKind};

use thiserror::Error;

#[derive(Debug, Error)]

pub enum LintViolation {

    #[error("{location}: {message} (severity: {severity:?})")]

    Violation {

        location: String,

        message: String,

        severity: Severity,

        suggestion: Option<String>,

    },

}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]

pub enum Severity {

    Error,

    Warning,

    Info,

}

/// Trait for implementing lint rules

pub trait LintRule: Send + Sync {

    fn name(&self) -> &str;

    fn check_expression(&self, expr: &Expr) -> Vec<LintViolation>;

}

/// Main linter that runs all rules

pub struct RuchyLinter {

    rules: Vec<Box<dyn LintRule>>,

}

impl Default for RuchyLinter {

    fn default() -> Self {

        Self::new()

    }

}

impl RuchyLinter {

    pub fn new() -> Self {

        let rules: Vec<Box<dyn LintRule>> = vec![

            Box::new(ComplexityRule::default()),

            Box::new(NoDebugPrintRule),

        ];

        Self { rules }

    }

    pub fn add_rule(&mut self, rule: Box<dyn LintRule>) {

        self.rules.push(rule);

    }

    pub fn lint(&self, expr: &Expr) -> Vec<LintViolation> {

        let mut violations = Vec::new();

        for rule in &self.rules {

            violations.extend(rule.check_expression(expr));

        }

        violations

    }

}

/// Rule: Cyclomatic complexity limit

#[derive(Default)]

struct ComplexityRule {

    max_complexity: usize,

}

impl ComplexityRule {

    #[allow(clippy::only_used_in_recursion)]

    fn calculate_complexity(&self, expr: &Expr) -> usize {

        match &expr.kind {

            ExprKind::If {

                condition,

                then_branch,

                else_branch,

            } => {

                1 + self.calculate_complexity(condition)

                    + self.calculate_complexity(then_branch)

                    + else_branch

                        .as_ref()

                        .map_or(0, |e| self.calculate_complexity(e))

            }

            ExprKind::Match { expr, arms } => {

                1 + self.calculate_complexity(expr)

                    + arms

                        .iter()

                        .map(|arm| self.calculate_complexity(&arm.body))

                        .sum::<usize>()

            }

            ExprKind::While { condition, body } => {

                1 + self.calculate_complexity(condition) + self.calculate_complexity(body)

            }

            ExprKind::For { iter, body, .. } => {

                1 + self.calculate_complexity(iter) + self.calculate_complexity(body)

            }

            ExprKind::Binary { left, right, .. } => {

                self.calculate_complexity(left) + self.calculate_complexity(right)

            }

            _ => 0,

        }

    }

}

impl LintRule for ComplexityRule {

    fn name(&self) -> &'static str {

        "complexity"

    }

    fn check_expression(&self, expr: &Expr) -> Vec<LintViolation> {

        let mut violations = Vec::new();

        let max = if self.max_complexity == 0 {

            10

        } else {

            self.max_complexity

        };

        let complexity = self.calculate_complexity(expr);

        if complexity > max {

            violations.push(LintViolation::Violation {

                location: format!("position {}", expr.span.start),

                message: format!("Cyclomatic complexity is {complexity} (max: {max})"),

                severity: Severity::Warning,

                suggestion: Some("Consider breaking this into smaller functions".to_string()),

            });

        }

        violations

    }

}

/// Rule: No debug print statements

struct NoDebugPrintRule;

impl LintRule for NoDebugPrintRule {

    fn name(&self) -> &'static str {

        "no_debug_print"

    }

    fn check_expression(&self, expr: &Expr) -> Vec<LintViolation> {

        match &expr.kind {

            ExprKind::Call { func, .. } => {

                if let ExprKind::Identifier(name) = &func.kind {

                    if name == "dbg" || name == "debug_print" {

                        vec![LintViolation::Violation {

                            location: format!("position {}", expr.span.start),

                            message: "Debug print statement found".to_string(),

                            severity: Severity::Warning,

                            suggestion: Some(

                                "Remove debug statements before committing".to_string(),

                            ),

                        }]

                    } else {

                        vec![]

                    }

                } else {

                    vec![]

                }

            }

            _ => vec![],

        }

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::frontend::ast::{Expr, ExprKind, Span, Literal, BinaryOp};

    fn make_test_expr(kind: ExprKind) -> Expr {

        Expr {

            kind,

            span: Span::new(0, 10),

            attributes: vec![],

        }

    }

    #[test]

    fn test_linter_creation() {

        let linter = RuchyLinter::new();

        assert_eq!(linter.rules.len(), 2);

    }

    #[test]

    fn test_linter_default() {

        let linter = RuchyLinter::default();

        assert_eq!(linter.rules.len(), 2);

    }

    #[test]

    fn test_add_custom_rule() {

        struct TestRule;

        impl LintRule for TestRule {

            fn name(&self) -> &'static str {

                "test"

            }

            fn check_expression(&self, _expr: &Expr) -> Vec<LintViolation> {

                vec![]

            }

        }

        let mut linter = RuchyLinter::new();

        linter.add_rule(Box::new(TestRule));

        assert_eq!(linter.rules.len(), 3);

    }

    #[test]

    fn test_severity_display() {

        assert_eq!(format!("{:?}", Severity::Error), "Error");

        assert_eq!(format!("{:?}", Severity::Warning), "Warning");

        assert_eq!(format!("{:?}", Severity::Info), "Info");

    }

    #[test]

    fn test_severity_equality() {

        assert_eq!(Severity::Error, Severity::Error);

        assert_ne!(Severity::Error, Severity::Warning);

    }

    #[test]

    fn test_lint_violation_display() {

        let violation = LintViolation::Violation {

            location: "line 5".to_string(),

            message: "Test violation".to_string(),

            severity: Severity::Warning,

            suggestion: Some("Fix it".to_string()),

        };

        let display = violation.to_string();

        assert!(display.contains("line 5"));

        assert!(display.contains("Test violation"));

        assert!(display.contains("Warning"));

    }

    #[test]

    fn test_lint_violation_without_suggestion() {

        let violation = LintViolation::Violation {

            location: "position 10".to_string(),

            message: "Error found".to_string(),

            severity: Severity::Error,

            suggestion: None,

        };

        let display = violation.to_string();

        assert!(display.contains("position 10"));

        assert!(display.contains("Error found"));

        assert!(display.contains("Error"));

    }

    #[test]

    fn test_complexity_rule_simple() {

        let rule = ComplexityRule::default();

        let expr = make_test_expr(ExprKind::Literal(Literal::Integer(42)));

        let violations = rule.check_expression(&expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_complexity_rule_name() {

        let rule = ComplexityRule::default();

        assert_eq!(rule.name(), "complexity");

    }

    #[test]

    fn test_complexity_rule_if_statement() {

        let rule = ComplexityRule { max_complexity: 0 }; // Will use default of 10

        // Create a simple if statement

        let if_expr = make_test_expr(ExprKind::If {

            condition: Box::new(make_test_expr(ExprKind::Literal(Literal::Bool(true)))),

            then_branch: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(1)))),

            else_branch: None,

        });

        let violations = rule.check_expression(&if_expr);

        assert!(violations.is_empty()); // Complexity is 1, under limit of 10

    }

    #[test]

    fn test_complexity_rule_nested_if_exceeds_limit() {

        let rule = ComplexityRule { max_complexity: 1 };

        // Create nested if statements to exceed complexity of 1

        let inner_if = make_test_expr(ExprKind::If {

            condition: Box::new(make_test_expr(ExprKind::Literal(Literal::Bool(true)))),

            then_branch: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(1)))),

            else_branch: None,

        });

        let outer_if = make_test_expr(ExprKind::If {

            condition: Box::new(make_test_expr(ExprKind::Literal(Literal::Bool(false)))),

            then_branch: Box::new(inner_if),

            else_branch: Some(Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(2))))),

        });

        let violations = rule.check_expression(&outer_if);

        assert!(!violations.is_empty());

        assert!(violations[0].to_string().contains("Cyclomatic complexity"));

    }

    #[test]

    fn test_complexity_rule_while_loop() {

        let rule = ComplexityRule { max_complexity: 5 };

        let while_expr = make_test_expr(ExprKind::While {

            condition: Box::new(make_test_expr(ExprKind::Literal(Literal::Bool(true)))),

            body: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(42)))),

        });

        let violations = rule.check_expression(&while_expr);

        assert!(violations.is_empty()); // Complexity is 1, under limit

    }

    #[test]

    fn test_complexity_rule_for_loop() {

        let rule = ComplexityRule { max_complexity: 5 };

        let for_expr = make_test_expr(ExprKind::For {

            var: "i".to_string(),

            pattern: None,

            iter: Box::new(make_test_expr(ExprKind::Range {

                start: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(0)))),

                end: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(10)))),

                inclusive: false,

            })),

            body: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(42)))),

        });

        let violations = rule.check_expression(&for_expr);

        assert!(violations.is_empty()); // Complexity is 1, under limit

    }

    #[test]

    fn test_complexity_rule_binary_operation() {

        let rule = ComplexityRule { max_complexity: 5 };

        let binary_expr = make_test_expr(ExprKind::Binary {

            left: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(1)))),

            op: BinaryOp::Add,

            right: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(2)))),

        });

        let violations = rule.check_expression(&binary_expr);

        assert!(violations.is_empty()); // Binary operations don't add complexity

    }

    #[test]

    fn test_no_debug_print_rule() {

        let rule = NoDebugPrintRule;

        // Test normal function call - no violation

        let normal_call = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Identifier("println".to_string()))),

            args: vec![],

        });

        assert!(rule.check_expression(&normal_call).is_empty());

        // Test debug print - should have violation

        let debug_call = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Identifier("dbg".to_string()))),

            args: vec![],

        });

        let violations = rule.check_expression(&debug_call);

        assert_eq!(violations.len(), 1);

        assert!(violations[0].to_string().contains("Debug print"));

        // Test debug_print - should have violation

        let debug_print = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Identifier("debug_print".to_string()))),

            args: vec![],

        });

        let violations = rule.check_expression(&debug_print);

        assert_eq!(violations.len(), 1);

    }

    #[test]

    fn test_no_debug_print_rule_name() {

        let rule = NoDebugPrintRule;

        assert_eq!(rule.name(), "no_debug_print");

    }

    #[test]

    fn test_linter_runs_all_rules() {

        let linter = RuchyLinter::new();

        // Create expression that violates debug print rule

        let expr = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Identifier("dbg".to_string()))),

            args: vec![],

        });

        let violations = linter.lint(&expr);

        assert!(!violations.is_empty());

    }

    #[test]

    fn test_linter_no_violations() {

        let linter = RuchyLinter::new();

        // Create simple expression with no violations

        let expr = make_test_expr(ExprKind::Literal(Literal::Integer(42)));

        let violations = linter.lint(&expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_complexity_calculation_match() {

        let rule = ComplexityRule { max_complexity: 10 };

        // Match expressions add complexity

        use crate::frontend::ast::{MatchArm, Pattern};

        let arms = vec![

            MatchArm {

                pattern: Pattern::Literal(Literal::Integer(1)),

                guard: None,

                body: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(10)))),

                span: Span::new(0, 10),

            },

            MatchArm {

                pattern: Pattern::Literal(Literal::Integer(2)),

                guard: None,

                body: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(20)))),

                span: Span::new(0, 10),

            },

        ];

        let match_expr = make_test_expr(ExprKind::Match {

            expr: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(42)))),

            arms,

        });

        let violations = rule.check_expression(&match_expr);

        assert!(violations.is_empty()); // Under complexity limit

    }

    #[test]

    fn test_complexity_rule_with_custom_max() {

        let rule = ComplexityRule { max_complexity: 3 };

        // Simple literal should not trigger

        let expr = make_test_expr(ExprKind::Literal(Literal::Integer(42)));

        let violations = rule.check_expression(&expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_no_debug_print_rule_non_call_expression() {

        let rule = NoDebugPrintRule;

        // Test with non-call expression

        let expr = make_test_expr(ExprKind::Literal(Literal::String("test".to_string())));

        let violations = rule.check_expression(&expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_no_debug_print_rule_non_identifier_function() {

        let rule = NoDebugPrintRule;

        // Test with non-identifier function (e.g., lambda call)

        let expr = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(42)))),

            args: vec![],

        });

        let violations = rule.check_expression(&expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_lint_violation_debug_formatting() {

        let violation = LintViolation::Violation {

            location: "test.ruchy:10:5".to_string(),

            message: "Complex expression detected".to_string(),

            severity: Severity::Info,

            suggestion: None,

        };

        let debug_str = format!("{violation:?}");

        assert!(debug_str.contains("Violation"));

        assert!(debug_str.contains("test.ruchy:10:5"));

    }

    #[test]

    fn test_severity_clone() {

        let sev1 = Severity::Warning;

        let sev2 = sev1;

        assert_eq!(sev1, sev2);

    }

    #[test]

    fn test_complexity_rule_if_with_else() {

        let rule = ComplexityRule { max_complexity: 5 };

        let if_expr = make_test_expr(ExprKind::If {

            condition: Box::new(make_test_expr(ExprKind::Literal(Literal::Bool(true)))),

            then_branch: Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(1)))),

            else_branch: Some(Box::new(make_test_expr(ExprKind::Literal(Literal::Integer(2))))),

        });

        let violations = rule.check_expression(&if_expr);

        assert!(violations.is_empty());

    }

    #[test]

    fn test_multiple_violations_from_linter() {

        let mut linter = RuchyLinter::new();

        // Add another rule that always fails

        struct AlwaysFailRule;

        impl LintRule for AlwaysFailRule {

            fn name(&self) -> &'static str {

                "always_fail"

            }

            fn check_expression(&self, expr: &Expr) -> Vec<LintViolation> {

                vec![LintViolation::Violation {

                    location: format!("position {}", expr.span.start),

                    message: "Always fails".to_string(),

                    severity: Severity::Error,

                    suggestion: None,

                }]

            }

        }

        linter.add_rule(Box::new(AlwaysFailRule));

        // Create expression that also violates debug print rule

        let expr = make_test_expr(ExprKind::Call {

            func: Box::new(make_test_expr(ExprKind::Identifier("dbg".to_string()))),

            args: vec![],

        });

        let violations = linter.lint(&expr);

        assert!(violations.len() >= 2); // At least 2 violations

    }

}