ryo_executor/engine/impls/

stmt_ops.rs

//! V2 ASTRegApply implementations for statement/expression operations
//!
//! - ReplaceExpr: Replace expressions matching a pattern
//! - ReplaceExprAt: Replace expression at specific position indices
//! - WrapExpr: Wrap expressions with macro calls
//! - RemoveStatement: Remove statements matching a pattern
//! - InsertStatement: Insert statements at specific positions
//! - ReplaceStatement: Replace statements matching a pattern
//!
//! # Implementation Strategy
//!
//! All operations work on function bodies in the ASTRegistry:
//! 1. Find target function(s)
//! 2. Traverse/modify statements or expressions
//! 3. Update the AST in registry

use ryo_analysis::SymbolKind;
use ryo_mutations::basic::stmt::{
    InsertPosition, InsertStatementMutation, RemoveStatementMutation, ReplaceExprAtMutation,
    ReplaceExprMutation, ReplaceStatementMutation, WrapExprMutation,
};
use ryo_mutations::{Mutation, MutationResult};
use ryo_source::pure::{MacroDelimiter, PureBlock, PureExpr, PureItem, PureStmt};

use crate::engine::{ASTMutationContext, ASTRegApply, ModificationType};

// =============================================================================
// ReplaceExprMutation
// =============================================================================

impl ASTRegApply for ReplaceExprMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: self.mutation_type().to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();
            let replacements = replace_expr_in_block(
                &mut new_func.body,
                &self.old_expr,
                &self.new_expr,
                self.replace_all,
            );

            if replacements > 0 {
                ctx.set_ast(fn_id, PureItem::Fn(new_func));
                ctx.emit_modified(fn_id, ModificationType::BodyModified);
                return MutationResult {
                    mutation_type: self.mutation_type().to_string(),
                    changes: replacements,
                    description: format!("Replaced {} expression(s)", replacements),
                };
            }
        }

        MutationResult {
            mutation_type: self.mutation_type().to_string(),
            changes: 0,
            description: "No matching expressions found".to_string(),
        }
    }
}

// =============================================================================
// WrapExprMutation
// =============================================================================

impl ASTRegApply for WrapExprMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: self.mutation_type().to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();
            let wraps = wrap_expr_in_block(
                &mut new_func.body,
                &self.target_expr,
                &self.wrapper_macro,
                self.wrap_all,
            );

            if wraps > 0 {
                ctx.set_ast(fn_id, PureItem::Fn(new_func));
                ctx.emit_modified(fn_id, ModificationType::BodyModified);
                return MutationResult {
                    mutation_type: self.mutation_type().to_string(),
                    changes: wraps,
                    description: format!(
                        "Wrapped {} expression(s) with {}!()",
                        wraps, self.wrapper_macro
                    ),
                };
            }
        }

        MutationResult {
            mutation_type: self.mutation_type().to_string(),
            changes: 0,
            description: "No matching expressions found".to_string(),
        }
    }
}

// =============================================================================
// RemoveStatementMutation
// =============================================================================

impl ASTRegApply for RemoveStatementMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: self.mutation_type().to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();
            let removed = remove_stmts_in_block(&mut new_func.body, &self.pattern, self.remove_all);

            if removed > 0 {
                ctx.set_ast(fn_id, PureItem::Fn(new_func));
                ctx.emit_modified(fn_id, ModificationType::BodyModified);
                return MutationResult {
                    mutation_type: self.mutation_type().to_string(),
                    changes: removed,
                    description: format!("Removed {} statement(s)", removed),
                };
            }
        }

        MutationResult {
            mutation_type: self.mutation_type().to_string(),
            changes: 0,
            description: "No matching statements found".to_string(),
        }
    }
}

// =============================================================================
// InsertStatementMutation
// =============================================================================

impl ASTRegApply for InsertStatementMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: self.mutation_type().to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();

            let inserted = match self.position {
                InsertPosition::Start => {
                    new_func.body.stmts.insert(0, self.stmt.clone());
                    true
                }
                InsertPosition::End => {
                    // Insert before return statement if present, otherwise at end
                    let insert_idx = find_return_index(&new_func.body.stmts);
                    new_func.body.stmts.insert(insert_idx, self.stmt.clone());
                    true
                }
                InsertPosition::BeforePattern | InsertPosition::AfterPattern => {
                    if let Some(ref reference_stmt) = self.reference_stmt {
                        insert_relative_to_stmt(
                            &mut new_func.body.stmts,
                            &self.stmt,
                            reference_stmt,
                            self.position == InsertPosition::AfterPattern,
                        )
                    } else {
                        false
                    }
                }
            };

            if inserted {
                ctx.set_ast(fn_id, PureItem::Fn(new_func));
                ctx.emit_modified(fn_id, ModificationType::BodyModified);
                return MutationResult {
                    mutation_type: self.mutation_type().to_string(),
                    changes: 1,
                    description: format!(
                        "Inserted statement in '{}' at {:?}",
                        self.target_fn, self.position
                    ),
                };
            }
        }

        MutationResult {
            mutation_type: self.mutation_type().to_string(),
            changes: 0,
            description: "Failed to insert statement".to_string(),
        }
    }
}

// =============================================================================
// ReplaceStatementMutation
// =============================================================================

impl ASTRegApply for ReplaceStatementMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: self.mutation_type().to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();
            let replaced =
                replace_stmts_in_block(&mut new_func.body, &self.old_stmt, &self.new_stmt);

            if replaced > 0 {
                ctx.set_ast(fn_id, PureItem::Fn(new_func));
                ctx.emit_modified(fn_id, ModificationType::BodyModified);
                return MutationResult {
                    mutation_type: self.mutation_type().to_string(),
                    changes: replaced,
                    description: format!("Replaced {} statement(s)", replaced),
                };
            }
        }

        MutationResult {
            mutation_type: self.mutation_type().to_string(),
            changes: 0,
            description: "No matching statements found".to_string(),
        }
    }
}

// =============================================================================
// Helper functions
// =============================================================================

/// Replace expressions in a block
fn replace_expr_in_block(
    block: &mut PureBlock,
    old: &PureExpr,
    new: &PureExpr,
    replace_all: bool,
) -> usize {
    let mut count = 0;
    for stmt in &mut block.stmts {
        count += replace_expr_in_stmt(stmt, old, new, replace_all);
        if !replace_all && count > 0 {
            return count;
        }
    }
    count
}

/// Wrap expressions in a block
fn wrap_expr_in_block(
    block: &mut PureBlock,
    target: &PureExpr,
    wrapper_macro: &str,
    wrap_all: bool,
) -> usize {
    let mut count = 0;
    for stmt in &mut block.stmts {
        count += wrap_expr_in_stmt(stmt, target, wrapper_macro, wrap_all);
        if !wrap_all && count > 0 {
            return count;
        }
    }
    count
}

fn wrap_expr_in_stmt(
    stmt: &mut PureStmt,
    target: &PureExpr,
    wrapper_macro: &str,
    wrap_all: bool,
) -> usize {
    match stmt {
        PureStmt::Local { init, .. } => {
            if let Some(expr) = init {
                wrap_expr(expr, target, wrapper_macro, wrap_all)
            } else {
                0
            }
        }
        PureStmt::Semi(expr) | PureStmt::Expr(expr) => {
            wrap_expr(expr, target, wrapper_macro, wrap_all)
        }
        PureStmt::Item(_) => 0,
        // Verbatim is opaque raw bytes — no inner mutation target
        // for stmt_ops to walk into (B-3-cont carrier).
        PureStmt::Verbatim(_) => 0,
    }
}

fn wrap_expr(expr: &mut PureExpr, target: &PureExpr, wrapper_macro: &str, wrap_all: bool) -> usize {
    if expr == target {
        let wrapped = PureExpr::Macro {
            name: wrapper_macro.to_string(),
            delimiter: MacroDelimiter::Paren,
            tokens: format!("{:?}", expr),
        };
        *expr = wrapped;
        return 1;
    }

    match expr {
        PureExpr::Binary { left, right, .. } => {
            let mut c = wrap_expr(left, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr(right, target, wrapper_macro, wrap_all);
            }
            c
        }
        PureExpr::Unary { expr: inner, .. } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Call { func, args } => {
            let mut c = wrap_expr(func, target, wrapper_macro, wrap_all);
            for arg in args {
                if wrap_all || c == 0 {
                    c += wrap_expr(arg, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::MethodCall { receiver, args, .. } => {
            let mut c = wrap_expr(receiver, target, wrapper_macro, wrap_all);
            for arg in args {
                if wrap_all || c == 0 {
                    c += wrap_expr(arg, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::Field { expr: inner, .. } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Index { expr: e, index } => {
            let mut c = wrap_expr(e, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr(index, target, wrapper_macro, wrap_all);
            }
            c
        }
        PureExpr::Block { block: b, .. } => wrap_expr_in_block(b, target, wrapper_macro, wrap_all),
        PureExpr::If {
            cond,
            then_branch,
            else_branch,
        } => {
            let mut c = wrap_expr(cond, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr_in_block(then_branch, target, wrapper_macro, wrap_all);
            }
            if let Some(else_expr) = else_branch {
                if wrap_all || c == 0 {
                    c += wrap_expr(else_expr, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::Match { expr: e, arms } => {
            let mut c = wrap_expr(e, target, wrapper_macro, wrap_all);
            for arm in arms {
                if wrap_all || c == 0 {
                    c += wrap_expr(&mut arm.body, target, wrapper_macro, wrap_all);
                }
                if let Some(guard) = &mut arm.guard {
                    if wrap_all || c == 0 {
                        c += wrap_expr(guard, target, wrapper_macro, wrap_all);
                    }
                }
            }
            c
        }
        PureExpr::Loop { body: b, .. } => wrap_expr_in_block(b, target, wrapper_macro, wrap_all),
        PureExpr::While { cond, body, .. } => {
            let mut c = wrap_expr(cond, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr_in_block(body, target, wrapper_macro, wrap_all);
            }
            c
        }
        PureExpr::For { expr: e, body, .. } => {
            let mut c = wrap_expr(e, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr_in_block(body, target, wrapper_macro, wrap_all);
            }
            c
        }
        PureExpr::Return(Some(inner))
        | PureExpr::Break {
            expr: Some(inner), ..
        } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Closure { body, .. } => wrap_expr(body, target, wrapper_macro, wrap_all),
        PureExpr::Struct { fields, .. } => {
            let mut c = 0;
            for (_, field_expr) in fields {
                if wrap_all || c == 0 {
                    c += wrap_expr(field_expr, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::Tuple(exprs) | PureExpr::Array(exprs) => {
            let mut c = 0;
            for e in exprs {
                if wrap_all || c == 0 {
                    c += wrap_expr(e, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::Ref { expr: inner, .. } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Await(inner) | PureExpr::Try(inner) => {
            wrap_expr(inner, target, wrapper_macro, wrap_all)
        }
        PureExpr::Range { start, end, .. } => {
            let mut c = 0;
            if let Some(s) = start {
                c += wrap_expr(s, target, wrapper_macro, wrap_all);
            }
            if let Some(e) = end {
                if wrap_all || c == 0 {
                    c += wrap_expr(e, target, wrapper_macro, wrap_all);
                }
            }
            c
        }
        PureExpr::Cast { expr: inner, .. } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Let { expr: inner, .. } => wrap_expr(inner, target, wrapper_macro, wrap_all),
        PureExpr::Async { body, .. } | PureExpr::Unsafe(body) => {
            wrap_expr_in_block(body, target, wrapper_macro, wrap_all)
        }
        PureExpr::Repeat { expr: e, len } => {
            let mut c = wrap_expr(e, target, wrapper_macro, wrap_all);
            if wrap_all || c == 0 {
                c += wrap_expr(len, target, wrapper_macro, wrap_all);
            }
            c
        }
        PureExpr::Lit(_)
        | PureExpr::Path(_)
        | PureExpr::Macro { .. }
        | PureExpr::Return(None)
        | PureExpr::Break { expr: None, .. }
        | PureExpr::Continue { .. }
        | PureExpr::Other(_)
        // Verbatim is opaque raw bytes — leaf for stmt_ops (B-3).
        | PureExpr::Verbatim(_) => 0,
    }
}

fn replace_expr_in_stmt(
    stmt: &mut PureStmt,
    old: &PureExpr,
    new: &PureExpr,
    replace_all: bool,
) -> usize {
    match stmt {
        PureStmt::Local { init, .. } => {
            if let Some(expr) = init {
                replace_expr(expr, old, new, replace_all)
            } else {
                0
            }
        }
        PureStmt::Semi(expr) | PureStmt::Expr(expr) => replace_expr(expr, old, new, replace_all),
        PureStmt::Item(_) => 0,
        // Verbatim is opaque raw bytes — no inner mutation target
        // for stmt_ops to walk into (B-3-cont carrier).
        PureStmt::Verbatim(_) => 0,
    }
}

fn replace_expr(expr: &mut PureExpr, old: &PureExpr, new: &PureExpr, replace_all: bool) -> usize {
    if expr == old {
        *expr = new.clone();
        return 1;
    }

    match expr {
        PureExpr::Binary { left, right, .. } => {
            let mut c = replace_expr(left, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr(right, old, new, replace_all);
            }
            c
        }
        PureExpr::Unary { expr: inner, .. } => replace_expr(inner, old, new, replace_all),
        PureExpr::Call { func, args } => {
            let mut c = replace_expr(func, old, new, replace_all);
            for arg in args {
                if replace_all || c == 0 {
                    c += replace_expr(arg, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::MethodCall { receiver, args, .. } => {
            let mut c = replace_expr(receiver, old, new, replace_all);
            for arg in args {
                if replace_all || c == 0 {
                    c += replace_expr(arg, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::Field { expr: inner, .. } => replace_expr(inner, old, new, replace_all),
        PureExpr::Index { expr: e, index } => {
            let mut c = replace_expr(e, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr(index, old, new, replace_all);
            }
            c
        }
        PureExpr::Block { block: b, .. } => replace_expr_in_block(b, old, new, replace_all),
        PureExpr::If {
            cond,
            then_branch,
            else_branch,
        } => {
            let mut c = replace_expr(cond, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr_in_block(then_branch, old, new, replace_all);
            }
            if let Some(else_expr) = else_branch {
                if replace_all || c == 0 {
                    c += replace_expr(else_expr, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::Match { expr: e, arms } => {
            let mut c = replace_expr(e, old, new, replace_all);
            for arm in arms {
                if replace_all || c == 0 {
                    c += replace_expr(&mut arm.body, old, new, replace_all);
                }
                if let Some(guard) = &mut arm.guard {
                    if replace_all || c == 0 {
                        c += replace_expr(guard, old, new, replace_all);
                    }
                }
            }
            c
        }
        PureExpr::Loop { body: b, .. } => replace_expr_in_block(b, old, new, replace_all),
        PureExpr::While { cond, body, .. } => {
            let mut c = replace_expr(cond, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr_in_block(body, old, new, replace_all);
            }
            c
        }
        PureExpr::For { expr: e, body, .. } => {
            let mut c = replace_expr(e, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr_in_block(body, old, new, replace_all);
            }
            c
        }
        PureExpr::Return(Some(inner))
        | PureExpr::Break {
            expr: Some(inner), ..
        } => replace_expr(inner, old, new, replace_all),
        PureExpr::Closure { body, .. } => replace_expr(body, old, new, replace_all),
        PureExpr::Struct { fields, .. } => {
            let mut c = 0;
            for (_, field_expr) in fields {
                if replace_all || c == 0 {
                    c += replace_expr(field_expr, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::Tuple(exprs) | PureExpr::Array(exprs) => {
            let mut c = 0;
            for e in exprs {
                if replace_all || c == 0 {
                    c += replace_expr(e, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::Ref { expr: inner, .. } => replace_expr(inner, old, new, replace_all),
        PureExpr::Await(inner) | PureExpr::Try(inner) => replace_expr(inner, old, new, replace_all),
        PureExpr::Range { start, end, .. } => {
            let mut c = 0;
            if let Some(s) = start {
                c += replace_expr(s, old, new, replace_all);
            }
            if let Some(e) = end {
                if replace_all || c == 0 {
                    c += replace_expr(e, old, new, replace_all);
                }
            }
            c
        }
        PureExpr::Cast { expr: inner, .. } => replace_expr(inner, old, new, replace_all),
        PureExpr::Let { expr: inner, .. } => replace_expr(inner, old, new, replace_all),
        PureExpr::Async { body, .. } | PureExpr::Unsafe(body) => {
            replace_expr_in_block(body, old, new, replace_all)
        }
        PureExpr::Repeat { expr: e, len } => {
            let mut c = replace_expr(e, old, new, replace_all);
            if replace_all || c == 0 {
                c += replace_expr(len, old, new, replace_all);
            }
            c
        }
        PureExpr::Lit(_)
        | PureExpr::Path(_)
        | PureExpr::Macro { .. }
        | PureExpr::Return(None)
        | PureExpr::Break { expr: None, .. }
        | PureExpr::Continue { .. }
        | PureExpr::Other(_)
        // Verbatim is opaque raw bytes — leaf for stmt_ops (B-3).
        | PureExpr::Verbatim(_) => 0,
    }
}

/// Check if two statements match structurally (using PartialEq).
///
/// Used by `InsertStatement` (BeforePattern/AfterPattern) for **exact** position matching.
/// InsertStatement needs to identify a specific statement to insert next to,
/// so structural equality is required (e.g., `let x = compute()` must NOT match `let x = other()`).
///
/// This is intentionally different from `stmt_matches_pattern` (used by RemoveStatement),
/// which uses fuzzy string-based matching appropriate for "remove anything matching this pattern".
fn stmt_matches(target: &PureStmt, stmt: &PureStmt) -> bool {
    target == stmt
}

/// Check if a statement matches a pattern (fuzzy, string-based).
///
/// Used by `RemoveStatement` for flexible pattern matching.
/// Also suitable for any operation where approximate matching is acceptable.
///
/// Pattern formats:
/// - `macro_name!(..)` or `macro_name!` - matches macro calls by name
/// - `let var_name = ...` - matches let statements by variable name
/// - Other patterns - substring match against Debug format
fn stmt_matches_pattern(stmt: &PureStmt, pattern: &str) -> bool {
    // Check for macro pattern: "name!(..)` or "name!"
    let macro_name = pattern
        .strip_suffix("!(..)")
        .or_else(|| pattern.strip_suffix('!'));

    if let Some(name) = macro_name {
        // Check if the statement is a macro call with this name
        match stmt {
            PureStmt::Semi(PureExpr::Macro { name: macro_n, .. })
            | PureStmt::Expr(PureExpr::Macro { name: macro_n, .. }) => {
                return macro_n == name;
            }
            _ => {}
        }
    }

    // Check for let pattern: "let var_name = ..." or "let var_name"
    if let Some(after_let) = pattern.strip_prefix("let ") {
        // Extract variable name (before "=" if present)
        let var_name = if let Some(eq_pos) = after_let.find(" = ") {
            after_let[..eq_pos].trim()
        } else if let Some(eq_pos) = after_let.find("=") {
            after_let[..eq_pos].trim()
        } else {
            after_let.trim()
        };

        if let PureStmt::Local {
            pattern: ryo_source::pure::PurePattern::Ident { name, .. },
            ..
        } = stmt
        {
            if name == var_name {
                return true;
            }
        }
    }

    // Fallback: match against Debug format
    let stmt_str = format!("{:?}", stmt);
    stmt_str.contains(pattern)
}

/// Remove statements matching a pattern from a block
fn remove_stmts_in_block(block: &mut PureBlock, pattern: &str, remove_all: bool) -> usize {
    let initial_len = block.stmts.len();
    let mut removed = 0;

    block.stmts.retain(|stmt| {
        if stmt_matches_pattern(stmt, pattern) {
            if !remove_all && removed > 0 {
                return true; // Keep this one, already removed one
            }
            removed += 1;
            false // Remove
        } else {
            true // Keep
        }
    });

    // Also recurse into nested blocks
    for stmt in &mut block.stmts {
        match stmt {
            PureStmt::Semi(expr) | PureStmt::Expr(expr) => {
                removed += remove_stmts_in_expr(expr, pattern, remove_all);
            }
            _ => {}
        }
    }

    removed.min(initial_len - block.stmts.len() + removed)
}

fn remove_stmts_in_expr(expr: &mut PureExpr, pattern: &str, remove_all: bool) -> usize {
    match expr {
        PureExpr::Block { block, .. } => remove_stmts_in_block(block, pattern, remove_all),
        PureExpr::If {
            then_branch,
            else_branch,
            ..
        } => {
            let mut c = remove_stmts_in_block(then_branch, pattern, remove_all);
            if let Some(else_expr) = else_branch {
                c += remove_stmts_in_expr(else_expr, pattern, remove_all);
            }
            c
        }
        PureExpr::Loop { body: block, .. } | PureExpr::While { body: block, .. } => {
            remove_stmts_in_block(block, pattern, remove_all)
        }
        PureExpr::For { body, .. } => remove_stmts_in_block(body, pattern, remove_all),
        PureExpr::Match { arms, .. } => {
            let mut c = 0;
            for arm in arms {
                c += remove_stmts_in_expr(&mut arm.body, pattern, remove_all);
            }
            c
        }
        PureExpr::Closure { body, .. } => remove_stmts_in_expr(body, pattern, remove_all),
        PureExpr::Async { body, .. } | PureExpr::Unsafe(body) => {
            remove_stmts_in_block(body, pattern, remove_all)
        }
        _ => 0,
    }
}

/// Replace statements in a block
fn replace_stmts_in_block(block: &mut PureBlock, old: &PureStmt, new: &PureStmt) -> usize {
    let mut count = 0;
    for stmt in &mut block.stmts {
        if stmt == old {
            *stmt = new.clone();
            count += 1;
        } else {
            // Recurse into nested blocks
            match stmt {
                PureStmt::Semi(expr) | PureStmt::Expr(expr) => {
                    count += replace_stmts_in_expr(expr, old, new);
                }
                _ => {}
            }
        }
    }
    count
}

fn replace_stmts_in_expr(expr: &mut PureExpr, old: &PureStmt, new: &PureStmt) -> usize {
    match expr {
        PureExpr::Block { block, .. } => replace_stmts_in_block(block, old, new),
        PureExpr::If {
            then_branch,
            else_branch,
            ..
        } => {
            let mut c = replace_stmts_in_block(then_branch, old, new);
            if let Some(else_expr) = else_branch {
                c += replace_stmts_in_expr(else_expr, old, new);
            }
            c
        }
        PureExpr::Loop { body: block, .. } | PureExpr::While { body: block, .. } => {
            replace_stmts_in_block(block, old, new)
        }
        PureExpr::For { body, .. } => replace_stmts_in_block(body, old, new),
        PureExpr::Match { arms, .. } => {
            let mut c = 0;
            for arm in arms {
                c += replace_stmts_in_expr(&mut arm.body, old, new);
            }
            c
        }
        PureExpr::Closure { body, .. } => replace_stmts_in_expr(body, old, new),
        PureExpr::Async { body, .. } | PureExpr::Unsafe(body) => {
            replace_stmts_in_block(body, old, new)
        }
        _ => 0,
    }
}

/// Find the index where return statement starts (for End insertion)
fn find_return_index(stmts: &[PureStmt]) -> usize {
    for (i, stmt) in stmts.iter().enumerate().rev() {
        match stmt {
            PureStmt::Expr(PureExpr::Return(_)) | PureStmt::Semi(PureExpr::Return(_)) => {
                return i;
            }
            PureStmt::Expr(_) if i == stmts.len() - 1 => {
                // Tail expression - insert before it
                return i;
            }
            _ => {}
        }
    }
    stmts.len() // Insert at end if no return found
}

/// Insert statement relative to a reference statement (exact structural match).
///
/// Uses `stmt_matches` (PartialEq) — NOT `stmt_matches_pattern`.
/// InsertStatement は「この特定の文の隣に挿入」なので、正確な位置特定が必要。
/// `reference_stmt` は converter が `syn::parse_str` → `to_pure()` で生成し、
/// 元ソースも同一パイプラインを経由するため、同一コードからは同一 PureStmt になる。
fn insert_relative_to_stmt(
    stmts: &mut Vec<PureStmt>,
    stmt: &PureStmt,
    reference_stmt: &PureStmt,
    after: bool,
) -> bool {
    for i in 0..stmts.len() {
        if stmt_matches(reference_stmt, &stmts[i]) {
            let insert_idx = if after { i + 1 } else { i };
            stmts.insert(insert_idx, stmt.clone());
            return true;
        }
    }
    false
}

// =============================================================================
// ReplaceExprAtMutation
// =============================================================================

impl ASTRegApply for ReplaceExprAtMutation {
    fn apply_to_registry(&self, ctx: &mut ASTMutationContext) -> MutationResult {
        let fn_id = self.target_fn;

        if !matches!(ctx.symbol_registry.kind(fn_id), Some(SymbolKind::Function)) {
            return MutationResult {
                mutation_type: "ReplaceExprAt".to_string(),
                changes: 0,
                description: format!("Target function '{:?}' not found", fn_id),
            };
        }

        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(fn_id) {
            let mut new_func = func.clone();

            if self.body_indices.is_empty() {
                return MutationResult {
                    mutation_type: "ReplaceExprAt".to_string(),
                    changes: 0,
                    description: "Empty body indices".to_string(),
                };
            }

            // First index is the statement index
            let stmt_idx = self.body_indices[0];
            if let Some(stmt) = new_func.body.stmts.get_mut(stmt_idx) {
                let replaced = if self.body_indices.len() == 1 {
                    replace_stmt_expr_at(stmt, &self.new_expr)
                } else {
                    replace_in_stmt_at_path(stmt, &self.body_indices[1..], &self.new_expr)
                };

                if replaced {
                    ctx.set_ast(fn_id, PureItem::Fn(new_func));
                    ctx.emit_modified(fn_id, ModificationType::BodyModified);
                    return MutationResult {
                        mutation_type: "ReplaceExprAt".to_string(),
                        changes: 1,
                        description: format!(
                            "Replaced expression at {:?} in '{}'",
                            self.body_indices, self.target_fn
                        ),
                    };
                }
            }
        }

        MutationResult {
            mutation_type: "ReplaceExprAt".to_string(),
            changes: 0,
            description: "Failed to replace expression at position".to_string(),
        }
    }
}

fn replace_stmt_expr_at(stmt: &mut PureStmt, new_expr: &PureExpr) -> bool {
    match stmt {
        PureStmt::Local { init, .. } => {
            if init.is_some() {
                *init = Some(new_expr.clone());
                true
            } else {
                false
            }
        }
        PureStmt::Semi(expr) | PureStmt::Expr(expr) => {
            *expr = new_expr.clone();
            true
        }
        PureStmt::Item(_) => false,
        // Verbatim is opaque raw bytes — leaf for stmt_ops (B-3-cont).
        PureStmt::Verbatim(_) => false,
    }
}

fn replace_in_stmt_at_path(stmt: &mut PureStmt, path: &[usize], new_expr: &PureExpr) -> bool {
    let expr = match stmt {
        PureStmt::Local {
            init: Some(expr), ..
        } => expr,
        PureStmt::Semi(expr) | PureStmt::Expr(expr) => expr,
        _ => return false,
    };

    if path.len() == 1 {
        // Replace child at index
        replace_child_at(expr, path[0], new_expr)
    } else {
        // Navigate deeper
        if let Some(child) = navigate_expr_mut(expr, &path[..path.len() - 1]) {
            replace_child_at(child, path[path.len() - 1], new_expr)
        } else {
            false
        }
    }
}

fn navigate_expr_mut<'a>(expr: &'a mut PureExpr, path: &[usize]) -> Option<&'a mut PureExpr> {
    if path.is_empty() {
        return Some(expr);
    }

    let idx = path[0];
    let child: Option<&'a mut PureExpr> = match expr {
        PureExpr::Binary { left, right, .. } => match idx {
            0 => Some(left.as_mut()),
            1 => Some(right.as_mut()),
            _ => None,
        },
        PureExpr::Unary { expr: inner, .. } => {
            if idx == 0 {
                Some(inner.as_mut())
            } else {
                None
            }
        }
        PureExpr::Call { args, .. } => args.get_mut(idx),
        PureExpr::MethodCall { receiver, args, .. } => {
            if idx == 0 {
                Some(receiver.as_mut())
            } else {
                args.get_mut(idx - 1)
            }
        }
        PureExpr::Tuple(exprs) | PureExpr::Array(exprs) => exprs.get_mut(idx),
        _ => None,
    };

    child.and_then(|c| navigate_expr_mut(c, &path[1..]))
}

fn replace_child_at(expr: &mut PureExpr, idx: usize, new_expr: &PureExpr) -> bool {
    match expr {
        PureExpr::Binary { left, right, .. } => match idx {
            0 => {
                **left = new_expr.clone();
                true
            }
            1 => {
                **right = new_expr.clone();
                true
            }
            _ => false,
        },
        PureExpr::Unary { expr: inner, .. } if idx == 0 => {
            **inner = new_expr.clone();
            true
        }
        PureExpr::Call { args, .. } => {
            if let Some(arg) = args.get_mut(idx) {
                *arg = new_expr.clone();
                true
            } else {
                false
            }
        }
        PureExpr::MethodCall { receiver, args, .. } => {
            if idx == 0 {
                **receiver = new_expr.clone();
                true
            } else if let Some(arg) = args.get_mut(idx - 1) {
                *arg = new_expr.clone();
                true
            } else {
                false
            }
        }
        PureExpr::Tuple(exprs) | PureExpr::Array(exprs) => {
            if let Some(e) = exprs.get_mut(idx) {
                *e = new_expr.clone();
                true
            } else {
                false
            }
        }
        _ => false,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::engine::ASTMutationEngine;
    use ryo_analysis::testing::ContextBuilder;

    #[test]
    fn test_v2_replace_expr() {
        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn compute() -> i32 {
    1 + 2
}
"#,
            )
            .build();

        // Find the function SymbolId
        let compute_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "compute"
            })
            .map(|(id, _)| id)
            .expect("compute function not found");

        let old = PureExpr::Binary {
            op: "+".to_string(),
            left: Box::new(PureExpr::Lit("1".to_string())),
            right: Box::new(PureExpr::Lit("2".to_string())),
        };
        let new = PureExpr::Lit("3".to_string());

        let mutation = ReplaceExprMutation::new(old, new, compute_id);

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        println!("ReplaceExpr result: {:?}", result.result);
    }

    #[test]
    fn test_v2_insert_statement_start() {
        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn greet() {
    println!("World");
}
"#,
            )
            .build();

        // Find the function SymbolId
        let greet_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "greet"
            })
            .map(|(id, _)| id)
            .expect("greet function not found");

        let stmt = PureStmt::Semi(PureExpr::Macro {
            name: "println".to_string(),
            delimiter: MacroDelimiter::Paren,
            tokens: "\"Hello\"".to_string(),
        });

        let mutation = InsertStatementMutation {
            stmt,
            target_fn: greet_id,
            position: InsertPosition::Start,
            reference_stmt: None,
        };

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        assert_eq!(result.result.changes, 1);
    }

    #[test]
    fn test_v2_insert_statement_after_pattern_let() {
        use ryo_source::pure::ToPure;

        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn process() {
    let x = 1;
    let y = 2;
}
"#,
            )
            .build();

        let process_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "process"
            })
            .map(|(id, _)| id)
            .expect("process function not found");

        // Parse the statement to insert
        let new_stmt: syn::Stmt = syn::parse_str("let z = 3;").unwrap();
        // Parse the reference statement
        let ref_stmt: syn::Stmt = syn::parse_str("let x = 1;").unwrap();

        // Debug: print the PureStmt representations
        let ref_pure = ref_stmt.to_pure();
        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(process_id) {
            eprintln!("=== AST body stmts ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] {:?}", i, s);
            }
            eprintln!("=== reference_stmt ===");
            eprintln!("  {:?}", ref_pure);
            eprintln!("=== match result ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] == ref? {}", i, &ref_pure == s);
            }
        }

        let mutation = InsertStatementMutation {
            stmt: new_stmt.to_pure(),
            target_fn: process_id,
            position: InsertPosition::AfterPattern,
            reference_stmt: Some(ref_pure),
        };

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        assert_eq!(
            result.result.changes, 1,
            "AfterPattern should insert 1 statement, got description: {}",
            result.result.description
        );
    }

    #[test]
    fn test_v2_insert_statement_after_pattern_macro() {
        use ryo_source::pure::ToPure;

        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn greet() {
    println!("hello");
    println!("world");
}
"#,
            )
            .build();

        let greet_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "greet"
            })
            .map(|(id, _)| id)
            .expect("greet function not found");

        // Parse the statement to insert
        let new_stmt: syn::Stmt = syn::parse_str("println!(\"inserted\");").unwrap();
        // Parse the reference statement
        let ref_stmt: syn::Stmt = syn::parse_str("println!(\"hello\");").unwrap();

        let ref_pure = ref_stmt.to_pure();
        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(greet_id) {
            eprintln!("=== AST body stmts (macro test) ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] {:?}", i, s);
            }
            eprintln!("=== reference_stmt ===");
            eprintln!("  {:?}", ref_pure);
            eprintln!("=== match result ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] == ref? {}", i, &ref_pure == s);
            }
        }

        let mutation = InsertStatementMutation {
            stmt: new_stmt.to_pure(),
            target_fn: greet_id,
            position: InsertPosition::AfterPattern,
            reference_stmt: Some(ref_pure),
        };

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        assert_eq!(
            result.result.changes, 1,
            "AfterPattern should insert 1 statement, got description: {}",
            result.result.description
        );
    }

    #[test]
    fn test_v2_insert_statement_after_pattern_method_chain() {
        use ryo_source::pure::ToPure;

        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn process(config: &mut Config) {
    config.set_timeout(Duration::from_secs(30));
    config.set_retries(3);
}
"#,
            )
            .build();

        let process_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "process"
            })
            .map(|(id, _)| id)
            .expect("process function not found");

        // Parse the reference: method call with nested call arg
        let ref_stmt: syn::Stmt =
            syn::parse_str("config.set_timeout(Duration::from_secs(30));").unwrap();
        let new_stmt: syn::Stmt = syn::parse_str("config.enable_logging();").unwrap();

        let ref_pure = ref_stmt.to_pure();
        if let Some(PureItem::Fn(func)) = ctx.ast_registry.get(process_id) {
            eprintln!("=== AST body stmts (method chain test) ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] {:?}", i, s);
            }
            eprintln!("=== reference_stmt ===");
            eprintln!("  {:?}", ref_pure);
            eprintln!("=== match ===");
            for (i, s) in func.body.stmts.iter().enumerate() {
                eprintln!("  [{}] == ref? {}", i, &ref_pure == s);
            }
        }

        let mutation = InsertStatementMutation {
            stmt: new_stmt.to_pure(),
            target_fn: process_id,
            position: InsertPosition::AfterPattern,
            reference_stmt: Some(ref_pure),
        };

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        assert_eq!(
            result.result.changes, 1,
            "AfterPattern for method chain should work, got: {}",
            result.result.description
        );
    }

    #[test]
    fn test_v2_remove_statement_no_match() {
        let mut ctx = ContextBuilder::new()
            .with_file(
                "src/lib.rs",
                r#"
fn simple() -> i32 {
    42
}
"#,
            )
            .build();

        use ryo_analysis::SymbolKind;
        use ryo_source::pure::ToPure;

        let simple_id = ctx
            .registry
            .iter()
            .find(|(id, path)| {
                matches!(ctx.registry.kind(*id), Some(SymbolKind::Function))
                    && path.name() == "simple"
            })
            .map(|(id, _)| id)
            .expect("simple function not found");

        let target_stmt: syn::Stmt = syn::parse_str("nonexistent;").unwrap();
        let mutation = RemoveStatementMutation::new(
            target_stmt.to_pure(),
            "nonexistent;".to_string(),
            simple_id,
        );

        let result = ASTMutationEngine::execute_ast_reg(&mutation, &mut ctx);
        assert_eq!(result.result.changes, 0);
    }
}