ryo-executor 0.1.0

//! MutationSpec: Atomic, serializable mutation specifications
//!
//! # Architecture: Intent vs MutationSpec
//!
//! Ryo has a two-layer mutation system:
//!
//! ```text
//! ┌─────────────────────────────────────────────────────────────────┐
//! │  Intent (ryo-app::intent)                                       │
//! │  - Public DSL for CLI users                                     │
//! │  - High-level, uses Pattern matching                            │
//! │  - One Intent may expand to multiple MutationSpecs              │
//! │  - Example: AddField { target: Pattern::Glob("*Config"), ... }  │
//! └───────────────────────────┬─────────────────────────────────────┘
//!                             ↓ Resolution & Expansion
//! ┌─────────────────────────────────────────────────────────────────┐
//! │  MutationSpec (this module)                                     │
//! │  - Execution-level specification                                │
//! │  - Concrete targets (SymbolId, exact names)                     │
//! │  - Atomic: one spec = one mutation                              │
//! │  - Example: AddField { struct_name: "AppConfig", ... }          │
//! └───────────────────────────┬─────────────────────────────────────┘
//!                             ↓ Execution
//! ┌─────────────────────────────────────────────────────────────────┐
//! │  AST Mutation                                                   │
//! │  - Actual code transformation                                   │
//! └─────────────────────────────────────────────────────────────────┘
//! ```
//!
//! ## Why Two Layers?
//!
//! - **Intent**: User-friendly, pattern-based, requires symbol resolution
//! - **MutationSpec**: Machine-friendly, direct targets, ready for execution
//!
//! This separation allows:
//! 1. CLI users to use high-level patterns (`*Config`)
//! 2. `Suggest` system to generate specs directly (bypassing Intent)
//! 3. Clear conflict detection at the MutationSpec level
//!
//! ## Usage by Suggest
//!
//! The `Suggest` trait (in `ryo-suggest`) generates `MutationSpec` directly:
//! - Detects opportunities from analyzed code
//! - Converts opportunities to `MutationSpec` via `to_mutation_specs()`
//! - Bypasses Intent layer for efficiency (no pattern resolution needed)
//!
//! See `ryo_suggest::suggest::Suggest` for the trait definition.
//!
//! # Design Goals
//!
//! Designed for:
//! - LLM-friendly: Can be generated/selected by lightweight LLMs
//! - Declarative: Pure data, no behavior
//! - Composable: Multiple specs form a ParallelBlueprint
//!
//! ## Scope: Single Crate + Multi-Module
//!
//! MutationSpec operates within a **single crate** (MonoCrate model).
//! Multi-crate workspace operations are **NOT SUPPORTED**:
//! - No cross-crate MoveItem
//! - No Cargo.toml manipulation (requires TOML parser, not AST)
//! - Use external tools for workspace-level refactoring
//!
//! ## Target Resolution
//!
//! All targeting uses `SymbolPath` (e.g., "crate::config::Settings").
//! SymbolPath provides:
//! - AST-based resolution
//! - Fine-grained conflict detection
//! - Type-safe path operations

use serde::{Deserialize, Serialize};

pub use ryo_analysis::{SymbolId, SymbolPath};
pub use ryo_mutations::{EnumToTraitStrategy, MatchHandling};
pub use ryo_source::ItemKind;

/// Target symbol specification for MutationSpec.
///
/// Supports flexible target resolution:
/// - Eager: Already resolved to SymbolId
/// - Lazy: Resolved during Wave execution (DetectConflict phase)
/// - Derived: Resolved from parent mutations (e.g., newly added struct)
///
/// # Design
///
/// Replaces the scattered `request_*` fields with a unified approach.
/// Enables batch processing of Add & Update operations within a Wave.
///
/// # Examples
///
/// ```text
/// ById(symbol_id)                      // Direct reference (already resolved)
/// ByPath("crate::config::Settings")    // Lazy resolution by path
/// ByKindAndName(Struct, "User")        // Lazy resolution by kind + name
/// ByAffectedId(parent_id, Field, "id") // Derived from parent (e.g., field in newly added struct)
/// ```
#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum MutationTargetSymbol {
    /// Direct reference by SymbolId (already resolved)
    ById(SymbolId),
    /// Lazy resolution by SymbolPath (parsed path)
    ByPath(Box<SymbolPath>),
    /// Lazy resolution by kind and name
    ByKindAndName(ItemKind, String),
    /// Derived from affected parent symbol
    /// Example: Field in a struct that was just added in the same Wave
    ByAffectedId {
        /// Parent symbol ID
        parent_id: SymbolId,
        /// Kind of the child item
        kind: ItemKind,
        /// Optional name (None for anonymous items)
        name: Option<String>,
    },
}

impl MutationTargetSymbol {
    /// Create a direct SymbolId reference
    pub fn by_id(id: SymbolId) -> Self {
        Self::ById(id)
    }

    /// Create a lazy SymbolPath reference
    pub fn by_path(path: SymbolPath) -> Self {
        Self::ByPath(Box::new(path))
    }

    /// Create a lazy kind+name reference
    pub fn by_kind_and_name(kind: ItemKind, name: impl Into<String>) -> Self {
        Self::ByKindAndName(kind, name.into())
    }

    /// Create a derived reference from parent
    pub fn by_affected_id(parent_id: SymbolId, kind: ItemKind, name: Option<String>) -> Self {
        Self::ByAffectedId {
            parent_id,
            kind,
            name,
        }
    }

    /// Check if this is already resolved to a SymbolId
    pub fn is_resolved(&self) -> bool {
        matches!(self, Self::ById(_))
    }

    /// Resolve to SymbolPath using the registry.
    ///
    /// Returns `Some(SymbolPath)` if resolution succeeds, `None` otherwise.
    pub fn to_path(&self, registry: &ryo_symbol::SymbolRegistry) -> Option<SymbolPath> {
        match self {
            Self::ById(id) => registry.resolve(*id).cloned(),
            Self::ByPath(path) => Some(*path.clone()),
            Self::ByKindAndName(_, name) => SymbolPath::parse(name).ok(),
            Self::ByAffectedId { parent_id, .. } => registry.resolve(*parent_id).cloned(),
        }
    }
}

// ============================================================================
// Type Transformation Types (for ReplaceType and EnumToTrait)
// ============================================================================

/// Type transformation pattern for ReplaceType.
///
/// Specifies how to transform a type reference.
///
/// # Examples
///
/// ```ignore
/// // Box<dyn Trait>
/// TypeTransform::BoxDyn { trait_name: "Status".to_string() }
///
/// // impl Trait
/// TypeTransform::ImplTrait { trait_name: "Status".to_string() }
///
/// // Generic: <T: Trait>
/// TypeTransform::Generic { param_name: "S".to_string(), bound: "Status".to_string() }
/// ```
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum TypeTransform {
    /// Transform to `Box<dyn Trait>`
    ///
    /// Example: `Status` → `Box<dyn Status>`
    BoxDyn {
        /// The trait name to use
        trait_name: String,
    },

    /// Transform to `impl Trait` (argument position) or `-> impl Trait` (return position)
    ///
    /// Example: `Status` → `impl Status`
    ImplTrait {
        /// The trait name to use
        trait_name: String,
    },

    /// Transform to generic parameter with trait bound
    ///
    /// Example: `fn foo(s: Status)` → `fn foo<S: Status>(s: S)`
    Generic {
        /// Name of the generic parameter (e.g., "S", "T")
        param_name: String,
        /// Trait bound (e.g., "Status", "Status + Send")
        bound: String,
    },

    /// Transform to a literal type string (escape hatch)
    ///
    /// Example: `Status` → `Arc<dyn Status + Send + Sync>`
    Literal(String),
}

impl TypeTransform {
    /// Create a BoxDyn transform
    pub fn box_dyn(trait_name: impl Into<String>) -> Self {
        Self::BoxDyn {
            trait_name: trait_name.into(),
        }
    }

    /// Create an ImplTrait transform
    pub fn impl_trait(trait_name: impl Into<String>) -> Self {
        Self::ImplTrait {
            trait_name: trait_name.into(),
        }
    }

    /// Create a Generic transform
    pub fn generic(param_name: impl Into<String>, bound: impl Into<String>) -> Self {
        Self::Generic {
            param_name: param_name.into(),
            bound: bound.into(),
        }
    }

    /// Create a Literal transform
    pub fn literal(type_str: impl Into<String>) -> Self {
        Self::Literal(type_str.into())
    }

    /// Get the resulting type as a string representation
    pub fn to_type_string(&self) -> String {
        match self {
            Self::BoxDyn { trait_name } => format!("Box<dyn {}>", trait_name),
            Self::ImplTrait { trait_name } => format!("impl {}", trait_name),
            Self::Generic { param_name, .. } => param_name.clone(),
            Self::Literal(s) => s.clone(),
        }
    }
}

/// Context where a type is used.
///
/// Used to filter which type usages should be replaced.
#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Hash)]
pub enum TypeContext {
    /// Function parameter type
    Parameter,
    /// Function return type
    ReturnType,
    /// Struct/enum field type
    Field,
    /// Local variable type annotation
    LocalVar,
    /// Trait bound (e.g., `T: Status`)
    TraitBound,
    /// Impl target type (e.g., `impl Foo for Bar`)
    ImplTarget,
    /// Generic type argument (e.g., `Vec<Status>`)
    GenericArg,
}

/// Atomic mutation specification
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(tag = "type")]
pub enum MutationSpec {
    // === Rename ===
    /// Rename an identifier across scope
    Rename {
        /// Target symbol (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New name to rename to
        to: String,
        #[serde(default)]
        scope: Scope,
    },

    // === Struct/Field ===
    /// Add a field to a struct
    AddField {
        /// Target struct (supports lazy resolution)
        target: MutationTargetSymbol,
        field_name: String,
        field_type: String,
        #[serde(default)]
        visibility: Visibility,
    },

    /// Remove a field from a struct
    RemoveField {
        /// Target struct (supports lazy resolution)
        target: MutationTargetSymbol,
        field_name: String,
    },

    // === Visibility ===
    /// Change visibility of an item or struct field
    ChangeVisibility {
        /// Target symbol (supports lazy resolution)
        target: MutationTargetSymbol,
        visibility: Visibility,
    },

    // === Derive ===
    /// Add derive macros to a type
    AddDerive {
        /// Target type (supports lazy resolution)
        target: MutationTargetSymbol,
        derives: Vec<String>,
    },

    /// Remove derive macros from a type
    RemoveDerive {
        /// Target type (supports lazy resolution)
        target: MutationTargetSymbol,
        derives: Vec<String>,
    },

    // === Enum ===
    /// Add a variant to an enum
    AddVariant {
        /// Target enum (supports lazy resolution)
        target: MutationTargetSymbol,
        variant_name: String,
        #[serde(default)]
        variant_kind: VariantKind,
    },

    /// Remove a variant from an enum
    RemoveVariant {
        /// Target enum (supports lazy resolution)
        target: MutationTargetSymbol,
        variant_name: String,
    },

    /// Add a match arm to a match expression
    ///
    /// Used to fix exhaustiveness errors when adding enum variants.
    AddMatchArm {
        /// Target function/method containing the match expression
        target: MutationTargetSymbol,
        /// Enum type being matched (for validation)
        enum_name: String,
        /// Pattern for the new arm (e.g., "Status::Cancelled")
        pattern: String,
        /// Body of the new arm (e.g., "todo!()")
        body: String,
    },

    /// Remove a match arm from a match expression
    ///
    /// Used to remove arms when deleting enum variants.
    RemoveMatchArm {
        /// Target function/method containing the match expression
        target: MutationTargetSymbol,
        /// Enum type being matched (for validation)
        enum_name: String,
        /// Pattern to remove (e.g., "Status::Completed")
        pattern: String,
    },

    /// Replace a match arm (pattern + body) in a match expression
    ///
    /// Unlike ReplaceExpr which only replaces the body, this replaces both
    /// the pattern and body atomically. Useful when pattern bindings need
    /// to change along with the body.
    ReplaceMatchArm {
        /// Target function/method containing the match expression
        target: MutationTargetSymbol,
        /// Enum type being matched (for validation)
        enum_name: String,
        /// Pattern to find and replace (e.g., "PathSegment::Slice { start: _, end: _ }")
        old_pattern: String,
        /// New pattern (e.g., "PathSegment::Slice { start, end }")
        new_pattern: String,
        /// New body expression
        new_body: String,
    },

    /// Add a field to all struct literals of a given type
    ///
    /// Used to fix missing field errors when adding struct fields.
    AddStructLiteralField {
        /// Target struct (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Field name to add
        field_name: String,
        /// Value expression (e.g., "None", "Default::default()")
        value: String,
    },

    /// Remove a field from all struct literals of a given type
    ///
    /// Used to update struct literals when removing struct fields.
    RemoveStructLiteralField {
        /// Target struct (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Field name to remove
        field_name: String,
    },

    // === Items ===
    /// Add an item (struct, fn, impl, etc.)
    AddItem {
        /// Target module (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Item content (Rust code)
        content: String,
        /// Insert position within the module
        #[serde(default)]
        position: InsertPosition,
    },

    /// Remove an item
    RemoveItem {
        /// Target item (supports lazy resolution)
        target: MutationTargetSymbol,
        item_kind: ItemKind,
    },

    // === Spec ===
    /// Add a Spec TypeAlias (Spec<Group, T> or SpecWith<Group, R, T>)
    AddSpec {
        /// SymbolId of the target type (required, O(1) lookup)
        type_id: SymbolId,
        /// SymbolId of the module to add the type alias (required, O(1) lookup)
        module_id: SymbolId,
        /// Group name (e.g., "ConfigGroup", "DomainGroup")
        group: String,
        /// Optional alias name (default: "{target}Spec")
        #[serde(default, skip_serializing_if = "Option::is_none")]
        alias_name: Option<String>,
        /// Relations (up to 3)
        #[serde(default)]
        relations: Vec<SpecRelation>,
    },

    /// Remove a Spec TypeAlias
    RemoveSpec {
        /// SymbolId of the spec alias to remove (required, O(1) lookup)
        type_id: SymbolId,
        /// SymbolId of the module containing the spec alias (required, O(1) lookup)
        module_id: SymbolId,
    },

    /// Validate existing Spec definitions
    ValidateSpec {
        /// Target modules as SymbolIds
        type_ids: Vec<SymbolId>,
        /// Expected group name (None = any group)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        expected_group: Option<String>,
        /// Check that relations are valid (targets exist)
        #[serde(default = "default_true")]
        validate_relations: bool,
    },

    // === Method ===
    /// Add a method to an impl block
    AddMethod {
        /// Target impl block (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Method name
        method_name: String,
        /// Parameters as (name, type) pairs
        #[serde(default)]
        params: Vec<(String, String)>,
        /// Return type (None for unit)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        return_type: Option<String>,
        /// Method body expression
        #[serde(default = "default_body")]
        body: String,
        /// Whether the method is public
        #[serde(default)]
        is_pub: bool,
        /// Self parameter: "ref" (&self), "mut" (&mut self), "owned" (self), or None
        #[serde(default, skip_serializing_if = "Option::is_none")]
        self_param: Option<SelfParam>,
    },

    /// Remove a method from an impl block
    RemoveMethod {
        /// Target impl block (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Method name to remove
        method_name: String,
    },

    // === Module ===
    /// Remove a module declaration
    RemoveMod {
        /// Target parent module (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Module name to remove
        mod_name: String,
    },

    /// Create a new module (adds to module tree)
    CreateMod {
        /// Target parent module (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New module name
        mod_name: String,
        /// Initial content (optional)
        #[serde(default)]
        content: String,
        /// Whether the module is public
        #[serde(default)]
        is_pub: bool,
    },

    // === Idiom Transformations ===
    /// Organize imports (sort, dedupe, merge)
    OrganizeImports {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        #[serde(default = "default_true")]
        deduplicate: bool,
        #[serde(default = "default_true")]
        merge_groups: bool,
    },

    /// Convert loop to iterator
    LoopToIterator {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        target_var: Option<String>,
    },

    /// Convert unwrap/expect to ? operator
    UnwrapToQuestion {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Only apply in specific function (None = all functions)
        #[serde(default)]
        target_fn: Option<SymbolId>,
        #[serde(default = "default_true")]
        include_expect: bool,
    },

    /// Simplify assign operations: `a = a + b` → `a += b`
    AssignOp {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Only apply in specific function (None = all functions)
        #[serde(default)]
        fn_id: Option<SymbolId>,
    },

    /// Simplify boolean comparisons: `x == true` → `x`, `x == false` → `!x`
    BoolSimplify {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Remove redundant .clone() on Copy types
    CloneOnCopy {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Merge nested if statements into single if with &&
    CollapsibleIf {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Replace empty/noop match arms with todo!/unimplemented!/unreachable!
    /// `_ => {}` → `_ => todo!()` or `_ => unreachable!()`
    NoOpArmToTodo {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Replacement macro: "todo", "unimplemented", or "unreachable" (default: "todo")
        #[serde(default = "default_noop_replacement")]
        replacement: String,
    },

    /// Convert comparisons to method calls: `s == ""` → `s.is_empty()`
    ComparisonToMethod {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Remove redundant closures: `|x| f(x)` → `f`
    RedundantClosure {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Introduce variable for repeated expressions
    /// Expression is specified as string and parsed at runtime
    IntroduceVariable {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Target function to apply (None = all functions)
        #[serde(default)]
        fn_id: Option<SymbolId>,
        /// Expression to extract (as Rust code string, e.g. "a + b * c")
        expr: String,
        /// Name for the new variable
        var_name: String,
    },

    /// Convert manual match on Option to .map(): `match opt { Some(x) => Some(f(x)), None => None }` → `opt.map(f)`
    ManualMap {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
    },

    /// Convert simple match to if let
    MatchToIfLet {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>,
    },

    /// Convert .filter().next() to .find()
    FilterNext {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Target function (None = all functions)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        fn_id: Option<SymbolId>,
    },

    /// Convert .map().unwrap_or() to .map_or()
    MapUnwrapOr {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        /// Target function (None = all functions)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        fn_id: Option<SymbolId>,
    },

    // === PureStmt/PureExpr Operations ===
    /// Replace an expression with another expression
    ///
    /// Target can be specified by:
    /// - `old_expr`: Pattern matching (searches for matching expressions)
    /// - `symbol_path`: Direct position (e.g., "crate::fn::$body::0::1")
    ReplaceExpr {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        #[serde(default)]
        fn_id: Option<SymbolId>,
        /// Expression to replace (as Rust code string) - pattern match mode
        old_expr: String,
        /// Replacement expression (as Rust code string)
        new_expr: String,
        /// Replace all occurrences (default: true)
        #[serde(default = "default_true")]
        replace_all: bool,
        /// Direct position (e.g., "my_crate::my_fn::$body::0::1::2")
        /// When specified, ignores old_expr and replaces at this exact position
        #[serde(default, skip_serializing_if = "Option::is_none")]
        symbol_path: Option<String>,
    },

    /// Remove statements matching a pattern
    ///
    /// Target can be specified by:
    /// - `pattern`: Pattern matching (searches for matching statements)
    /// - `symbol_path`: Direct position (e.g., "crate::fn::$body::2")
    RemoveStatement {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>, // None = all
        #[serde(default)]
        fn_id: Option<SymbolId>,
        /// Statement pattern to remove (as Rust code string, e.g. "println!(..)") - pattern match mode
        pattern: String,
        /// Remove all occurrences (default: true)
        #[serde(default = "default_true")]
        remove_all: bool,
        /// Direct position (e.g., "my_crate::my_fn::$body::2")
        /// When specified, ignores pattern and removes at this exact position
        #[serde(default, skip_serializing_if = "Option::is_none")]
        symbol_path: Option<String>,
    },

    /// Insert a statement at a specific position
    ///
    /// Position can be specified by:
    /// - `position` + `reference_pattern`: Traditional mode
    /// - `symbol_path`: Direct position (inserts after $body::N)
    InsertStatement {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>,
        /// Target function
        #[serde(default)]
        fn_id: SymbolId,
        /// Statement to insert (as Rust code string)
        stmt: String,
        /// Insert position
        #[serde(default)]
        position: StmtInsertPosition,
        /// Reference pattern for BeforePattern/AfterPattern positions
        #[serde(default, skip_serializing_if = "Option::is_none")]
        reference_pattern: Option<String>,
        /// Direct position (e.g., "my_crate::my_fn::$body::2")
        /// When specified, ignores position and inserts after this statement
        #[serde(default, skip_serializing_if = "Option::is_none")]
        symbol_path: Option<String>,
    },

    /// Replace a statement with another statement
    ///
    /// Target can be specified by:
    /// - `old_stmt`: Pattern matching (searches for matching statements)
    /// - `symbol_path`: Direct position (e.g., "crate::fn::$body::1")
    ReplaceStatement {
        /// Target module (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        module_id: Option<SymbolId>,
        #[serde(default, skip_serializing_if = "Option::is_none")]
        fn_id: Option<SymbolId>,
        /// Statement to replace (as Rust code string) - pattern match mode
        old_stmt: String,
        /// Replacement statement (as Rust code string)
        new_stmt: String,
        /// Direct position (e.g., "my_crate::my_fn::$body::1")
        /// When specified, ignores old_stmt and replaces at this exact position
        #[serde(default, skip_serializing_if = "Option::is_none")]
        symbol_path: Option<String>,
    },

    // === Trait Abstraction ===
    /// Extract a trait from an impl block
    ExtractTrait {
        /// Target impl block (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Name for the new trait
        trait_name: String,
        /// Optional: specific methods to extract (None = all)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        methods: Option<Vec<String>>,
    },

    /// Inline a trait back into inherent impl
    InlineTrait {
        /// Target trait (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Struct that implements the trait
        struct_name: String,
        /// Whether to remove the trait definition
        #[serde(default = "default_true")]
        remove_trait: bool,
    },

    /// Replace all occurrences of a type with a transformed type
    ///
    /// # Examples
    ///
    /// ```ignore
    /// // Replace Status with Box<dyn Status>
    /// MutationSpec::ReplaceType {
    ///     from_type: "Status".to_string(),
    ///     to_type: TypeTransform::BoxDyn { trait_name: "Status".to_string() },
    ///     scope: None,
    ///     contexts: None,
    /// }
    /// ```
    ReplaceType {
        /// Target type to replace (supports lazy resolution)
        target: MutationTargetSymbol,
        /// How to transform the type
        to_type: TypeTransform,
        /// Scope to limit replacements (None = entire crate)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        scope: Option<SymbolPath>,
        /// Which contexts to replace in (None = all contexts)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        contexts: Option<Vec<TypeContext>>,
    },

    /// Convert an enum to a trait with struct implementations
    ///
    /// Transforms:
    /// - `enum Status { Running, Stopped }` into:
    /// - `pub trait Status {}`
    /// - `pub struct Running;`
    /// - `pub struct Stopped;`
    /// - `impl Status for Running {}`
    /// - `impl Status for Stopped {}`
    ///
    /// Also updates all usage sites: `Status::Running` → `Running`
    ///
    /// ## Type Replacement
    ///
    /// With `strategy: dynamic` (default):
    /// - `fn process(status: Status)` → `fn process(status: Box<dyn Status>)`
    ///
    /// With `strategy: static`:
    /// - `fn process(status: Status)` → `fn process(status: impl Status)`
    ///
    /// With `strategy: marker_only`:
    /// - No type replacement (manual migration required)
    ///
    EnumToTrait {
        /// Target enum (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Optional: custom trait name (default: same as enum name)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        trait_name: Option<String>,
        /// Whether to remove the original enum (default: true)
        #[serde(default = "default_true")]
        remove_enum: bool,
        /// Type replacement strategy (default: dynamic = Box<dyn Trait>)
        #[serde(default)]
        strategy: EnumToTraitStrategy,
        /// How to handle match expressions (default: warn_only)
        #[serde(default)]
        match_handling: MatchHandling,
    },

    // === Cross-file Operations ===
    /// Move an item from one file to another
    MoveItem {
        /// Source module (supports lazy resolution)
        source: MutationTargetSymbol,
        /// Target module (supports lazy resolution)
        target: MutationTargetSymbol,
        /// Item name to move
        item_name: String,
        /// Item kind (Struct, Enum, Fn, etc.)
        item_kind: ItemKind,
        /// Whether to add use statement in source file
        #[serde(default = "default_true")]
        add_use: bool,
    },

    // === Plugin Transformations ===
    /// Execute a WASM plugin transform
    PluginTransform {
        /// Plugin name (e.g., "map-unwrap-or", "custom-lint")
        plugin_name: String,
        /// Target module as SymbolId (None = all modules)
        #[serde(default, skip_serializing_if = "Option::is_none")]
        target_id: Option<SymbolId>,
        /// File glob patterns (e.g., ["src/**/*.rs", "tests/*.rs"])
        #[serde(default, skip_serializing_if = "Vec::is_empty")]
        file_patterns: Vec<String>,
        /// Plugin-specific configuration as JSON
        #[serde(default)]
        config: serde_json::Value,
    },

    // === Duplicate Operations ===
    /// Duplicate a function with a new name
    DuplicateFunction {
        /// Target function (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New function name
        to: String,
    },

    /// Duplicate a struct with a new name (including impl blocks)
    DuplicateStruct {
        /// Target struct (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New struct name
        to: String,
        /// Whether to also duplicate impl blocks
        #[serde(default = "default_true")]
        include_impls: bool,
    },

    /// Duplicate an enum with a new name (including impl blocks)
    DuplicateEnum {
        /// Target enum (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New enum name
        to: String,
        /// Whether to also duplicate impl blocks
        #[serde(default = "default_true")]
        include_impls: bool,
    },

    /// Duplicate an inline module with a new name
    DuplicateModTree {
        /// Target module (supports lazy resolution)
        target: MutationTargetSymbol,
        /// New module name
        to: String,
    },
}

fn default_true() -> bool {
    true
}

impl MutationSpec {
    /// Get the kind name of this spec (e.g., "Rename", "AddField")
    ///
    /// Used by MutationRegistry to route specs to appropriate converters.
    /// TODO: Consider typed approach (enum variant discriminant or macro-based)
    pub fn kind_name(&self) -> &'static str {
        match self {
            Self::Rename { .. } => "Rename",
            Self::AddField { .. } => "AddField",
            Self::RemoveField { .. } => "RemoveField",
            Self::ChangeVisibility { .. } => "ChangeVisibility",
            Self::AddDerive { .. } => "AddDerive",
            Self::RemoveDerive { .. } => "RemoveDerive",
            Self::AddVariant { .. } => "AddVariant",
            Self::RemoveVariant { .. } => "RemoveVariant",
            Self::AddMatchArm { .. } => "AddMatchArm",
            Self::RemoveMatchArm { .. } => "RemoveMatchArm",
            Self::ReplaceMatchArm { .. } => "ReplaceMatchArm",
            Self::AddStructLiteralField { .. } => "AddStructLiteralField",
            Self::RemoveStructLiteralField { .. } => "RemoveStructLiteralField",
            Self::AddItem { .. } => "AddItem",
            Self::RemoveItem { .. } => "RemoveItem",
            Self::AddSpec { .. } => "AddSpec",
            Self::RemoveSpec { .. } => "RemoveSpec",
            Self::ValidateSpec { .. } => "ValidateSpec",
            Self::AddMethod { .. } => "AddMethod",
            Self::RemoveMethod { .. } => "RemoveMethod",
            Self::RemoveMod { .. } => "RemoveMod",
            Self::CreateMod { .. } => "CreateMod",
            Self::OrganizeImports { .. } => "OrganizeImports",
            Self::LoopToIterator { .. } => "LoopToIterator",
            Self::UnwrapToQuestion { .. } => "UnwrapToQuestion",
            Self::AssignOp { .. } => "AssignOp",
            Self::BoolSimplify { .. } => "BoolSimplify",
            Self::CloneOnCopy { .. } => "CloneOnCopy",
            Self::CollapsibleIf { .. } => "CollapsibleIf",
            Self::NoOpArmToTodo { .. } => "NoOpArmToTodo",
            Self::ComparisonToMethod { .. } => "ComparisonToMethod",
            Self::RedundantClosure { .. } => "RedundantClosure",
            Self::IntroduceVariable { .. } => "IntroduceVariable",
            Self::ManualMap { .. } => "ManualMap",
            Self::MatchToIfLet { .. } => "MatchToIfLet",
            Self::FilterNext { .. } => "FilterNext",
            Self::MapUnwrapOr { .. } => "MapUnwrapOr",
            Self::ReplaceExpr { .. } => "ReplaceExpr",
            Self::RemoveStatement { .. } => "RemoveStatement",
            Self::InsertStatement { .. } => "InsertStatement",
            Self::ReplaceStatement { .. } => "ReplaceStatement",
            Self::ExtractTrait { .. } => "ExtractTrait",
            Self::InlineTrait { .. } => "InlineTrait",
            Self::ReplaceType { .. } => "ReplaceType",
            Self::EnumToTrait { .. } => "EnumToTrait",
            Self::MoveItem { .. } => "MoveItem",
            Self::PluginTransform { .. } => "PluginTransform",
            Self::DuplicateFunction { .. } => "DuplicateFunction",
            Self::DuplicateStruct { .. } => "DuplicateStruct",
            Self::DuplicateEnum { .. } => "DuplicateEnum",
            Self::DuplicateModTree { .. } => "DuplicateModTree",
        }
    }

    /// Check if this mutation is a rename
    pub fn is_rename(&self) -> bool {
        matches!(self, Self::Rename { .. })
    }

    /// Check if this is an additive operation (order-independent within same target)
    ///
    /// Additive operations like AddItem, AddMethod, AddField etc. can be applied
    /// in any order to the same target without conflict, unless they add the
    /// same named item (detected via `additive_identity`).
    pub fn is_additive(&self) -> bool {
        matches!(
            self,
            Self::AddItem { .. }
                | Self::AddMethod { .. }
                | Self::AddField { .. }
                | Self::AddVariant { .. }
                | Self::AddDerive { .. }
                | Self::CreateMod { .. }
                | Self::AddMatchArm { .. }
                | Self::AddStructLiteralField { .. }
                | Self::AddSpec { .. }
        )
    }

    /// Get unique identity for additive operations (for duplicate detection)
    ///
    /// Returns a unique identifier for what this operation adds.
    /// Two additive operations with the same `additive_identity` targeting the
    /// same parent are true conflicts (trying to add the same thing twice).
    pub fn additive_identity(&self) -> Option<String> {
        match self {
            Self::AddItem { content, .. } => {
                // Extract item name from content (first identifier after pub/struct/fn/enum/etc.)
                extract_item_name_from_content(content)
            }
            Self::AddMethod { method_name, .. } => Some(method_name.clone()),
            Self::AddField { field_name, .. } => Some(field_name.clone()),
            Self::AddVariant { variant_name, .. } => Some(variant_name.clone()),
            Self::AddDerive { derives, .. } => Some(derives.join(",")),
            Self::CreateMod { mod_name, .. } => Some(mod_name.clone()),
            Self::AddMatchArm { pattern, .. } => Some(pattern.clone()),
            Self::AddStructLiteralField { field_name, .. } => Some(field_name.clone()),
            Self::AddSpec { type_id, .. } => Some(format!("{:?}", type_id)),
            _ => None,
        }
    }

    /// Check if this is an idiom transformation
    pub fn is_idiom(&self) -> bool {
        matches!(
            self,
            Self::OrganizeImports { .. }
                | Self::LoopToIterator { .. }
                | Self::UnwrapToQuestion { .. }
                | Self::AssignOp { .. }
                | Self::BoolSimplify { .. }
                | Self::CloneOnCopy { .. }
                | Self::CollapsibleIf { .. }
                | Self::NoOpArmToTodo { .. }
                | Self::ComparisonToMethod { .. }
                | Self::RedundantClosure { .. }
                | Self::IntroduceVariable { .. }
                | Self::ManualMap { .. }
                | Self::MatchToIfLet { .. }
                | Self::FilterNext { .. }
                | Self::MapUnwrapOr { .. }
                | Self::ReplaceExpr { .. }
                | Self::RemoveStatement { .. }
                | Self::InsertStatement { .. }
                | Self::ReplaceStatement { .. }
                | Self::PluginTransform { .. }
        )
    }

    /// Get target symbols from this spec.
    ///
    /// Returns references to all `MutationTargetSymbol` fields in this spec.
    /// Used for computing `affected_symbols` after mutation execution.
    pub fn get_targets(&self) -> Vec<&MutationTargetSymbol> {
        match self {
            // Specs with single target field
            Self::Rename { target, .. }
            | Self::AddField { target, .. }
            | Self::RemoveField { target, .. }
            | Self::ChangeVisibility { target, .. }
            | Self::AddDerive { target, .. }
            | Self::RemoveDerive { target, .. }
            | Self::AddVariant { target, .. }
            | Self::RemoveVariant { target, .. }
            | Self::AddMatchArm { target, .. }
            | Self::RemoveMatchArm { target, .. }
            | Self::ReplaceMatchArm { target, .. }
            | Self::AddStructLiteralField { target, .. }
            | Self::RemoveStructLiteralField { target, .. }
            | Self::AddItem { target, .. }
            | Self::RemoveItem { target, .. }
            | Self::AddMethod { target, .. }
            | Self::RemoveMethod { target, .. }
            | Self::RemoveMod { target, .. }
            | Self::CreateMod { target, .. }
            | Self::ExtractTrait { target, .. }
            | Self::InlineTrait { target, .. }
            | Self::ReplaceType { target, .. }
            | Self::EnumToTrait { target, .. }
            | Self::MoveItem { target, .. }
            | Self::DuplicateFunction { target, .. }
            | Self::DuplicateStruct { target, .. }
            | Self::DuplicateEnum { target, .. }
            | Self::DuplicateModTree { target, .. } => vec![target],

            // Specs with SymbolId fields (not MutationTargetSymbol)
            Self::AddSpec { .. } | Self::RemoveSpec { .. } | Self::ValidateSpec { .. } => vec![],

            // Idiom transformations (module-scoped, no specific target)
            Self::OrganizeImports { .. }
            | Self::LoopToIterator { .. }
            | Self::UnwrapToQuestion { .. }
            | Self::AssignOp { .. }
            | Self::BoolSimplify { .. }
            | Self::CloneOnCopy { .. }
            | Self::CollapsibleIf { .. }
            | Self::NoOpArmToTodo { .. }
            | Self::ComparisonToMethod { .. }
            | Self::RedundantClosure { .. }
            | Self::IntroduceVariable { .. }
            | Self::ManualMap { .. }
            | Self::MatchToIfLet { .. }
            | Self::FilterNext { .. }
            | Self::MapUnwrapOr { .. }
            | Self::ReplaceExpr { .. }
            | Self::RemoveStatement { .. }
            | Self::InsertStatement { .. }
            | Self::ReplaceStatement { .. }
            | Self::PluginTransform { .. } => vec![],
        }
    }
}

/// Scope for mutations
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
#[serde(tag = "type")]
pub enum Scope {
    /// All modules in project
    #[default]
    Project,

    /// Specific module by path
    Mod { path: SymbolPath },

    /// Within a specific item
    Item {
        target: SymbolPath,
        item_name: String,
    },
}

/// Visibility levels
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
#[serde(rename_all = "snake_case")]
pub enum Visibility {
    #[default]
    Private,
    Pub,
    PubCrate,
    PubSuper,
    PubIn(String),
}

impl Visibility {
    pub fn to_rust_syntax(&self) -> &str {
        match self {
            Self::Private => "",
            Self::Pub => "pub ",
            Self::PubCrate => "pub(crate) ",
            Self::PubSuper => "pub(super) ",
            Self::PubIn(_) => "pub(in ...) ", // Needs special handling
        }
    }
}

/// Enum variant kinds
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
#[serde(tag = "type")]
pub enum VariantKind {
    #[default]
    Unit,
    Tuple {
        types: Vec<String>,
    },
    Struct {
        fields: Vec<(String, String)>,
    },
}

/// Position for inserting items
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
#[serde(tag = "type")]
pub enum InsertPosition {
    #[default]
    Top,
    Bottom,
    AfterItem {
        name: String,
    },
    BeforeItem {
        name: String,
    },
}

/// Position for inserting statements within a function
#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
#[serde(rename_all = "snake_case")]
pub enum StmtInsertPosition {
    /// At the start of the function body
    Start,
    /// At the end of the function body (before return statement if any)
    #[default]
    End,
    /// Before a statement matching the reference pattern
    BeforePattern,
    /// After a statement matching the reference pattern
    AfterPattern,
}

/// Self parameter for methods
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum SelfParam {
    /// &self
    Ref,
    /// &mut self
    Mut,
    /// self (owned)
    Owned,
}

fn default_body() -> String {
    "todo!()".to_string()
}

fn default_noop_replacement() -> String {
    "todo".to_string()
}

/// Relation for Spec TypeAlias
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub struct SpecRelation {
    /// Relation kind
    pub kind: SpecRelationKind,
    /// Target type name (simple name, e.g., "User")
    pub target: String,
    /// Direct SymbolId for target (from Discover result)
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub symbol_id: Option<SymbolId>,
    /// Full SymbolPath for target (for disambiguation)
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub target_path: Option<SymbolPath>,
}

impl SpecRelation {
    /// Create a new SpecRelation with just a name
    pub fn new(kind: SpecRelationKind, target: impl Into<String>) -> Self {
        Self {
            kind,
            target: target.into(),
            symbol_id: None,
            target_path: None,
        }
    }

    /// Create a new SpecRelation with a SymbolPath
    pub fn with_path(kind: SpecRelationKind, target: impl Into<String>, path: SymbolPath) -> Self {
        Self {
            kind,
            target: target.into(),
            symbol_id: None,
            target_path: Some(path),
        }
    }

    /// Create a new SpecRelation with a SymbolId
    pub fn with_symbol_id(
        kind: SpecRelationKind,
        target: impl Into<String>,
        symbol_id: SymbolId,
    ) -> Self {
        Self {
            kind,
            target: target.into(),
            symbol_id: Some(symbol_id),
            target_path: None,
        }
    }
}

/// Relation kinds for Spec
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(rename_all = "PascalCase")]
pub enum SpecRelationKind {
    /// A depends on B (A needs B to function)
    DependsOn,
    /// A is related to B (semantic relationship)
    RelatedTo,
    /// A is part of B (aggregate membership)
    PartOf,
}

impl SpecRelationKind {
    /// Get the Rust type name for this relation
    pub fn as_type_name(&self) -> &'static str {
        match self {
            Self::DependsOn => "DependsOn",
            Self::RelatedTo => "RelatedTo",
            Self::PartOf => "PartOf",
        }
    }
}

// ItemKind is re-exported from ryo_source

/// Extract item name from Rust code content
///
/// Parses common Rust item declarations to extract the name.
/// Used by `additive_identity()` for AddItem duplicate detection.
fn extract_item_name_from_content(content: &str) -> Option<String> {
    // Simple regex-free parsing for common patterns
    let trimmed = content.trim();

    // Skip attributes and find the item declaration
    let mut lines = trimmed.lines();
    let mut decl_line = "";
    for line in lines.by_ref() {
        let line = line.trim();
        if !line.starts_with('#') && !line.starts_with("//") && !line.is_empty() {
            decl_line = line;
            break;
        }
    }

    // Parse common patterns: pub? (struct|enum|fn|type|const|static|trait|impl|mod|use) NAME
    let tokens: Vec<&str> = decl_line.split_whitespace().collect();
    if tokens.is_empty() {
        return None;
    }

    let mut idx = 0;

    // Skip visibility
    if tokens.get(idx) == Some(&"pub") {
        idx += 1;
        // Skip pub(crate), pub(super), etc.
        if let Some(t) = tokens.get(idx) {
            if t.starts_with('(') {
                idx += 1;
            }
        }
    }

    // Get keyword
    let keyword = tokens.get(idx)?;
    idx += 1;

    match *keyword {
        "struct" | "enum" | "fn" | "type" | "const" | "static" | "trait" | "mod" => {
            // Next token is the name (may include generics)
            let name = tokens.get(idx)?;
            // Strip generics <...> and trailing punctuation
            let name = name.split('<').next().unwrap_or(name);
            let name = name.trim_end_matches(|c: char| !c.is_alphanumeric() && c != '_');
            Some(name.to_string())
        }
        "impl" => {
            // impl Trait for Type or impl Type
            // For impl blocks, include the full impl signature for identity
            let rest = tokens[idx..].join(" ");

            // Extract impl signature (everything before '{' or '<')
            // This includes "Trait for Type" or just "Type"
            let impl_sig = rest
                .split(['{', '<'])
                .next()
                .map(|s| s.trim())
                .filter(|s| !s.is_empty());

            // Also extract method names from the impl block to differentiate
            // multiple impl blocks for the same type
            let methods: Vec<&str> = content
                .lines()
                .filter_map(|line| {
                    let trimmed = line.trim();
                    if trimmed.starts_with("pub fn ") || trimmed.starts_with("fn ") {
                        let after_fn = trimmed
                            .strip_prefix("pub fn ")
                            .or_else(|| trimmed.strip_prefix("fn "))?;
                        let method_name = after_fn.split('(').next()?.trim();
                        Some(method_name)
                    } else {
                        None
                    }
                })
                .collect();

            match (impl_sig, methods.is_empty()) {
                (Some(sig), false) => Some(format!(
                    "impl_{}::{}",
                    sig.replace(' ', "_"),
                    methods.join(",")
                )),
                // Use full signature for empty impl blocks (e.g., "impl_Status_for_Running")
                (Some(sig), true) => Some(format!("impl_{}", sig.replace(' ', "_"))),
                _ => None,
            }
        }
        "use" => {
            // use path::Name or use path::{A, B}
            // Return the full use statement as identity
            Some(tokens[idx..].join(" "))
        }
        _ => {
            // Unknown pattern, use first meaningful token
            Some(keyword.to_string())
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_mutation_spec_serialize() {
        // Test serialization with ByPath (which contains the symbol path)
        let spec = MutationSpec::Rename {
            target: MutationTargetSymbol::ByPath(Box::new(
                SymbolPath::parse("test_crate::old_name").unwrap(),
            )),
            to: "new_name".to_string(),
            scope: Scope::Project,
        };

        let json = serde_json::to_string_pretty(&spec).unwrap();
        assert!(json.contains("Rename"), "JSON should contain Rename");
        assert!(
            json.contains("old_name"),
            "JSON should contain old_name in ByPath"
        );
        assert!(json.contains("new_name"), "JSON should contain new_name");

        let parsed: MutationSpec = serde_json::from_str(&json).unwrap();
        assert_eq!(
            spec, parsed,
            "Round-trip serialization should preserve spec"
        );
    }

    #[test]
    fn test_idiom_detection() {
        let spec = MutationSpec::OrganizeImports {
            module_id: None,
            deduplicate: true,
            merge_groups: true,
        };

        assert!(spec.is_idiom());
        assert!(!spec.is_rename());
    }
}