aft/commands/

apply_patch.rs

//! Rust implementation of the `apply_patch` command.

use std::collections::{HashMap, HashSet};
use std::fs;
use std::path::{Component, Path, PathBuf};

use lsp_types::FileChangeType;
use serde_json::{json, Value};

use crate::context::AppContext;
use crate::edit;
use crate::patch::apply::apply_update_chunks;
use crate::patch::parser::{parse_patch, Hunk};
use crate::protocol::{RawRequest, Response};

#[derive(Clone)]
struct ResolvedHunk {
    hunk: Hunk,
    source: ResolvedPath,
    move_dest: Option<ResolvedPath>,
}

#[derive(Clone)]
struct ResolvedPath {
    abs: PathBuf,
    rel: String,
}

struct AppliedHunkResult {
    index: usize,
    kind: &'static str,
    file_path: PathBuf,
    display_path: PathBuf,
    move_path: Option<PathBuf>,
    before: String,
    after: String,
    additions: usize,
    deletions: usize,
}

struct DiffEntry {
    file_path: PathBuf,
    display_path: PathBuf,
    move_path: Option<PathBuf>,
    last_kind: &'static str,
    before: String,
    after: String,
    additions: usize,
    deletions: usize,
    hunk_count: usize,
}

fn path_string(path: &Path) -> String {
    path.to_string_lossy().into_owned()
}

/// Agent-facing DISPLAY paths (relativePath, movePath, diff headers) are
/// forward-slash normalized so they are stable across platforms — matching the
/// rest of AFT's tools (e.g. outline's `path_to_slash`). Without this, Windows
/// emits `nested\dest.txt` and breaks the cross-platform display contract.
fn display_slash(path: &Path) -> String {
    path.to_string_lossy().replace('\\', "/")
}

fn command_params(req: &RawRequest) -> &Value {
    req.params
        .get("params")
        .filter(|params| params.is_object())
        .unwrap_or(&req.params)
}

fn project_root(ctx: &AppContext) -> Option<PathBuf> {
    ctx.config().project_root.clone()
}

fn project_root_for_relative_paths(ctx: &AppContext) -> Option<PathBuf> {
    project_root(ctx)
}

fn resolve_patch_input(ctx: &AppContext, path: &str) -> PathBuf {
    let raw = Path::new(path);
    if raw.is_absolute() {
        raw.to_path_buf()
    } else if let Some(root) = project_root(ctx) {
        root.join(raw)
    } else {
        std::env::current_dir()
            .unwrap_or_else(|_| PathBuf::from("."))
            .join(raw)
    }
}

fn normalize_path_lexically(path: &Path) -> PathBuf {
    let mut normalized = PathBuf::new();
    for component in path.components() {
        match component {
            Component::CurDir => {}
            Component::ParentDir => {
                normalized.pop();
            }
            other => normalized.push(other.as_os_str()),
        }
    }
    normalized
}

fn normalize_resolved_path(path: PathBuf) -> PathBuf {
    fs::canonicalize(&path).unwrap_or_else(|_| normalize_path_lexically(&path))
}

fn relative_path(abs: &Path, root: Option<&Path>) -> String {
    if let Some(root) = root {
        if let Ok(rel) = abs.strip_prefix(root) {
            return display_slash(rel);
        }
        if let Ok(canonical_root) = fs::canonicalize(root) {
            if let Ok(rel) = abs.strip_prefix(canonical_root) {
                return display_slash(rel);
            }
        }
    }
    display_slash(abs)
}

fn resolve_path(req: &RawRequest, ctx: &AppContext, path: &str) -> Result<ResolvedPath, Response> {
    let input = resolve_patch_input(ctx, path);
    let abs = normalize_resolved_path(ctx.validate_path(&req.id, &input)?);
    let root = project_root_for_relative_paths(ctx);
    let rel = relative_path(&abs, root.as_deref());
    Ok(ResolvedPath { abs, rel })
}

fn remember_path(
    abs: &Path,
    rel: &str,
    affected_abs: &mut Vec<String>,
    affected_rel: &mut Vec<String>,
) {
    let abs_s = path_string(abs);
    if !affected_abs.iter().any(|existing| existing == &abs_s) {
        affected_abs.push(abs_s);
    }
    if !affected_rel.iter().any(|existing| existing == rel) {
        affected_rel.push(rel.to_string());
    }
}

fn resolve_hunks(
    req: &RawRequest,
    ctx: &AppContext,
    hunks: Vec<Hunk>,
) -> Result<(Vec<ResolvedHunk>, Vec<String>, Vec<String>), Response> {
    let mut resolved = Vec::with_capacity(hunks.len());
    let mut affected_abs = Vec::new();
    let mut affected_rel = Vec::new();

    for hunk in hunks {
        let (source_path, move_path) = match &hunk {
            Hunk::Add { path, .. } | Hunk::Delete { path } => (path.as_str(), None),
            Hunk::Update {
                path, move_path, ..
            } => (path.as_str(), move_path.as_deref()),
        };
        let source = resolve_path(req, ctx, source_path)?;
        remember_path(
            &source.abs,
            &source.rel,
            &mut affected_abs,
            &mut affected_rel,
        );
        let move_dest = if let Some(move_path) = move_path {
            let dest = resolve_path(req, ctx, move_path)?;
            if dest.abs == source.abs {
                // Models can spell an in-place edit as a move back to the same file.
                // Drop the move so apply and preview both use the normal update path.
                None
            } else {
                remember_path(&dest.abs, &dest.rel, &mut affected_abs, &mut affected_rel);
                Some(dest)
            }
        } else {
            None
        };
        resolved.push(ResolvedHunk {
            hunk,
            source,
            move_dest,
        });
    }

    Ok((resolved, affected_abs, affected_rel))
}

fn line_count(content: &str) -> usize {
    if content.is_empty() {
        return 0;
    }
    let mut parts = content.split('\n').collect::<Vec<_>>();
    if parts.last() == Some(&"") {
        parts.pop();
    }
    parts.len()
}

fn diff_counts(before: &str, after: &str) -> (usize, usize) {
    use similar::ChangeTag;

    let diff = similar::TextDiff::from_lines(before, after);
    let mut additions = 0usize;
    let mut deletions = 0usize;
    for change in diff.iter_all_changes() {
        match change.tag() {
            ChangeTag::Insert => additions += 1,
            ChangeTag::Delete => deletions += 1,
            ChangeTag::Equal => {}
        }
    }
    (additions, deletions)
}

fn ensure_parent_dirs(path: &Path) -> Result<(), String> {
    if let Some(parent) = path.parent() {
        if !parent.as_os_str().is_empty() && !parent.exists() {
            fs::create_dir_all(parent)
                .map_err(|error| format!("failed to create directories: {error}"))?;
        }
    }
    Ok(())
}

fn discard_latest_backup(ctx: &AppContext, req: &RawRequest, op_id: &str, path: &Path) {
    ctx.backup()
        .lock()
        .discard_latest_operation_entry_for_path(req.session(), op_id, path);
}

fn snapshot_for_write_once(
    req: &RawRequest,
    ctx: &AppContext,
    path: &Path,
    op_id: &str,
    existed: bool,
    description: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<bool, String> {
    if backed_paths.contains(path) {
        return Ok(false);
    }

    if existed {
        edit::auto_backup(ctx, req.session(), path, description, Some(op_id))
            .map(|_| ())
            .map_err(|error| error.to_string())
    } else {
        ctx.backup()
            .lock()
            .snapshot_op_tombstone(req.session(), op_id, path, description)
            .map(|_| ())
            .map_err(|error| error.to_string())
    }?;
    backed_paths.insert(path.to_path_buf());
    Ok(true)
}

fn restore_pre_write_state(path: &Path, existed: bool, original: Option<&str>) {
    if existed {
        if let Some(original) = original {
            let _ = fs::write(path, original);
        }
    } else if path.exists() {
        let _ = fs::remove_file(path);
    }
}

fn write_patched_file(
    req: &RawRequest,
    ctx: &AppContext,
    path: &Path,
    content: &str,
    op_id: &str,
    description: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<(String, bool), String> {
    let existed = path.exists();
    let original = if existed {
        Some(
            fs::read_to_string(path)
                .map_err(|error| format!("failed to read pre-write content: {error}"))?,
        )
    } else {
        None
    };

    let snapshot_taken =
        snapshot_for_write_once(req, ctx, path, op_id, existed, description, backed_paths)?;
    if let Err(error) = ensure_parent_dirs(path) {
        if snapshot_taken {
            discard_latest_backup(ctx, req, op_id, path);
            backed_paths.remove(path);
        }
        return Err(error);
    }

    let params = command_params(req);
    let mut write_result = match edit::write_format_validate(path, content, &ctx.config(), params) {
        Ok(result) => result,
        Err(error) => {
            restore_pre_write_state(path, existed, original.as_deref());
            if snapshot_taken {
                discard_latest_backup(ctx, req, op_id, path);
                backed_paths.remove(path);
            }
            return Err(error.to_string());
        }
    };

    if write_result.rolled_back {
        if snapshot_taken {
            discard_latest_backup(ctx, req, op_id, path);
            backed_paths.remove(path);
        }
        return Err("produced invalid syntax (rolled back)".to_string());
    }

    let final_content = fs::read_to_string(path).unwrap_or_else(|_| content.to_string());
    let change_type = if existed {
        FileChangeType::CHANGED
    } else {
        FileChangeType::CREATED
    };
    ctx.lsp_notify_watched_config_file(path, change_type);
    write_result.lsp_outcome = ctx.lsp_post_write(path, &final_content, params);
    Ok((final_content, snapshot_taken))
}

fn delete_file_with_backup(
    req: &RawRequest,
    ctx: &AppContext,
    path: &Path,
    op_id: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<bool, String> {
    let snapshot_taken = if backed_paths.contains(path) {
        false
    } else {
        edit::auto_backup(
            ctx,
            req.session(),
            path,
            "apply_patch: pre-delete backup",
            Some(op_id),
        )
        .map_err(|error| error.to_string())?;
        backed_paths.insert(path.to_path_buf());
        true
    };

    if let Err(error) = fs::remove_file(path) {
        if snapshot_taken {
            discard_latest_backup(ctx, req, op_id, path);
            backed_paths.remove(path);
        }
        return Err(format!("failed to delete: {error}"));
    }
    ctx.lsp_notify_watched_config_file(path, FileChangeType::DELETED);
    Ok(snapshot_taken)
}

fn read_required(path: &Path, action: &str, patch_path: &str) -> Result<String, String> {
    fs::read_to_string(path).map_err(|error| format!("Failed to {action} {patch_path}: {error}"))
}

fn preview_virtual_content(
    virtual_files: &HashMap<PathBuf, Option<String>>,
    path: &Path,
) -> Option<Option<String>> {
    virtual_files.get(path).cloned()
}

fn read_preview_content(
    virtual_files: &HashMap<PathBuf, Option<String>>,
    path: &Path,
    action: &str,
    patch_path: &str,
) -> Result<String, String> {
    if let Some(content) = preview_virtual_content(virtual_files, path) {
        return content.ok_or_else(|| {
            format!(
                "Failed to {action} {patch_path}: file not found: {}",
                path_string(path)
            )
        });
    }
    read_required(path, action, patch_path)
}

fn build_preview_response(
    req: &RawRequest,
    resolved: &[ResolvedHunk],
    affected_abs: Vec<String>,
    affected_rel: Vec<String>,
) -> Response {
    let mut virtual_files: HashMap<PathBuf, Option<String>> = HashMap::new();
    let mut patches = Vec::new();
    let filepath = affected_rel
        .first()
        .cloned()
        .unwrap_or_else(|| ".".to_string());

    for resolved_hunk in resolved {
        match &resolved_hunk.hunk {
            Hunk::Add { path, contents } => {
                let virtual_content =
                    preview_virtual_content(&virtual_files, &resolved_hunk.source.abs);
                let exists = virtual_content
                    .map(|content| content.is_some())
                    .unwrap_or_else(|| resolved_hunk.source.abs.exists());
                if exists {
                    return Response::error(
                        &req.id,
                        "invalid_request",
                        format!(
                            "Failed to create {path}: file already exists. Use *** Update File: to modify, or *** Delete File: first if you want to replace it entirely."
                        ),
                    );
                }
                let after = ensure_trailing_newline(contents);
                patches.push(edit::build_unified_diff(
                    &display_slash(&resolved_hunk.source.abs),
                    "",
                    &after,
                ));
                virtual_files.insert(resolved_hunk.source.abs.clone(), Some(after));
            }
            Hunk::Delete { path } => {
                let before = match read_preview_content(
                    &virtual_files,
                    &resolved_hunk.source.abs,
                    "delete",
                    path,
                ) {
                    Ok(content) => content,
                    Err(error) => return Response::error(&req.id, "invalid_request", error),
                };
                patches.push(edit::build_unified_diff(
                    &display_slash(&resolved_hunk.source.abs),
                    &before,
                    "",
                ));
                virtual_files.insert(resolved_hunk.source.abs.clone(), None);
            }
            Hunk::Update {
                path,
                chunks,
                move_path: _,
            } => {
                let before = match read_preview_content(
                    &virtual_files,
                    &resolved_hunk.source.abs,
                    "update",
                    path,
                ) {
                    Ok(content) => content,
                    Err(error) => return Response::error(&req.id, "invalid_request", error),
                };
                let after = match apply_update_chunks(
                    &before,
                    &path_string(&resolved_hunk.source.abs),
                    chunks,
                ) {
                    Ok(content) => content,
                    Err(error) => {
                        return Response::error(
                            &req.id,
                            "invalid_request",
                            format!("Failed to update {path}: {error}"),
                        );
                    }
                };
                let target = resolved_hunk
                    .move_dest
                    .as_ref()
                    .unwrap_or(&resolved_hunk.source);
                patches.push(edit::build_unified_diff(
                    &display_slash(&target.abs),
                    &before,
                    &after,
                ));
                if resolved_hunk.move_dest.is_some() {
                    virtual_files.insert(resolved_hunk.source.abs.clone(), None);
                }
                virtual_files.insert(target.abs.clone(), Some(after));
            }
        }
    }

    Response::success(
        &req.id,
        json!({
            "preview": true,
            "preview_diff": patches.join("\n"),
            "affected_paths": affected_abs,
            "affected_rel_paths": affected_rel,
            "filepath": filepath,
        }),
    )
}

fn ensure_trailing_newline(content: &str) -> String {
    if content.ends_with('\n') {
        content.to_string()
    } else {
        format!("{content}\n")
    }
}

fn add_failure(failures: &mut Vec<Value>, path: &str, error: String) {
    failures.push(json!({ "path": path, "error": error }));
}

fn failure_paths(failures: &[Value]) -> String {
    failures
        .iter()
        .filter_map(|failure| failure.get("path").and_then(Value::as_str))
        .collect::<Vec<_>>()
        .join(", ")
}

fn apply_add(
    req: &RawRequest,
    ctx: &AppContext,
    resolved: &ResolvedHunk,
    _path: &str,
    contents: &str,
    op_id: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<AppliedHunkResult, String> {
    if resolved.source.abs.exists() {
        return Err(
            "file already exists. Use *** Update File: to modify, or *** Delete File: first if you want to replace it entirely."
                .to_string(),
        );
    }

    let after = ensure_trailing_newline(contents);
    let (final_content, _) = write_patched_file(
        req,
        ctx,
        &resolved.source.abs,
        &after,
        op_id,
        "apply_patch: file created by add hunk",
        backed_paths,
    )?;
    let (additions, deletions) = diff_counts("", &final_content);
    Ok(AppliedHunkResult {
        index: 0,
        kind: "add",
        file_path: resolved.source.abs.clone(),
        display_path: resolved.source.abs.clone(),
        move_path: None,
        before: String::new(),
        after: final_content,
        additions,
        deletions,
    })
}

fn apply_delete(
    req: &RawRequest,
    ctx: &AppContext,
    resolved: &ResolvedHunk,
    _path: &str,
    op_id: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<AppliedHunkResult, String> {
    if !resolved.source.abs.exists() {
        return Err("file not found".to_string());
    }
    if !resolved.source.abs.is_file() {
        return Err("not a regular file".to_string());
    }

    let before = fs::read_to_string(&resolved.source.abs)
        .map_err(|error| format!("failed to read before delete: {error}"))?;
    let deletions = line_count(&before);
    delete_file_with_backup(req, ctx, &resolved.source.abs, op_id, backed_paths)?;
    Ok(AppliedHunkResult {
        index: 0,
        kind: "delete",
        file_path: resolved.source.abs.clone(),
        display_path: resolved.source.abs.clone(),
        move_path: None,
        before,
        after: String::new(),
        additions: 0,
        deletions,
    })
}

fn apply_update(
    req: &RawRequest,
    ctx: &AppContext,
    resolved: &ResolvedHunk,
    chunks: &[crate::patch::parser::UpdateFileChunk],
    op_id: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<AppliedHunkResult, String> {
    let original = fs::read_to_string(&resolved.source.abs)
        .map_err(|error| format!("failed to read file: {error}"))?;
    let new_content = apply_update_chunks(&original, &path_string(&resolved.source.abs), chunks)?;

    if let Some(dest) = &resolved.move_dest {
        apply_move_update(
            req,
            ctx,
            resolved,
            dest,
            original,
            new_content,
            op_id,
            backed_paths,
        )
    } else {
        let (final_content, _) = write_patched_file(
            req,
            ctx,
            &resolved.source.abs,
            &new_content,
            op_id,
            "apply_patch: pre-update backup",
            backed_paths,
        )?;
        let (additions, deletions) = diff_counts(&original, &final_content);
        Ok(AppliedHunkResult {
            index: 0,
            kind: "update",
            file_path: resolved.source.abs.clone(),
            display_path: resolved.source.abs.clone(),
            move_path: None,
            before: original,
            after: final_content,
            additions,
            deletions,
        })
    }
}

fn apply_move_update(
    req: &RawRequest,
    ctx: &AppContext,
    resolved: &ResolvedHunk,
    dest: &ResolvedPath,
    original: String,
    new_content: String,
    op_id: &str,
    backed_paths: &mut HashSet<PathBuf>,
) -> Result<AppliedHunkResult, String> {
    let dest_existed = dest.abs.exists();
    let dest_snapshot = if dest_existed {
        Some(
            fs::read_to_string(&dest.abs)
                .map_err(|error| format!("move: failed to read destination snapshot: {error}"))?,
        )
    } else {
        None
    };

    let (final_content, dest_snapshot_taken) = match write_patched_file(
        req,
        ctx,
        &dest.abs,
        &new_content,
        op_id,
        "apply_patch: move destination backup",
        backed_paths,
    ) {
        Ok(outcome) => outcome,
        Err(error) => {
            if !dest_existed && dest.abs.exists() {
                let _ = fs::remove_file(&dest.abs);
            }
            return Err(error);
        }
    };

    let source_snapshot_taken = if backed_paths.contains(&resolved.source.abs) {
        false
    } else {
        edit::auto_backup(
            ctx,
            req.session(),
            &resolved.source.abs,
            "apply_patch: move source backup",
            Some(op_id),
        )
        .map_err(|error| error.to_string())?;
        backed_paths.insert(resolved.source.abs.clone());
        true
    };

    if let Err(error) = fs::remove_file(&resolved.source.abs) {
        if source_snapshot_taken {
            discard_latest_backup(ctx, req, op_id, &resolved.source.abs);
            backed_paths.remove(&resolved.source.abs);
        }
        rollback_move_destination(
            req,
            ctx,
            op_id,
            &dest.abs,
            dest_existed,
            dest_snapshot.as_deref(),
            dest_snapshot_taken,
            backed_paths,
        );
        return Err(format!(
            "move: failed to remove source after writing destination: {error}"
        ));
    }
    ctx.lsp_notify_watched_config_file(&resolved.source.abs, FileChangeType::DELETED);

    let (additions, deletions) = diff_counts(&original, &final_content);
    Ok(AppliedHunkResult {
        index: 0,
        kind: "update",
        file_path: resolved.source.abs.clone(),
        display_path: dest.abs.clone(),
        move_path: Some(dest.abs.clone()),
        before: original,
        after: final_content,
        additions,
        deletions,
    })
}

fn rollback_move_destination(
    req: &RawRequest,
    ctx: &AppContext,
    op_id: &str,
    dest: &Path,
    dest_existed: bool,
    dest_snapshot: Option<&str>,
    dest_snapshot_taken: bool,
    backed_paths: &mut HashSet<PathBuf>,
) {
    if dest_snapshot_taken {
        discard_latest_backup(ctx, req, op_id, dest);
        backed_paths.remove(dest);
    }
    if dest_existed {
        if let Some(snapshot) = dest_snapshot {
            let _ = fs::write(dest, snapshot);
        }
    } else if dest.exists() {
        let _ = fs::remove_file(dest);
    }
}

fn report_key(applied: &AppliedHunkResult) -> String {
    if let Some(move_path) = &applied.move_path {
        format!(
            "{}\0{}",
            path_string(&applied.file_path),
            path_string(move_path)
        )
    } else {
        path_string(&applied.file_path)
    }
}

fn metadata_files(applied: &[AppliedHunkResult], root: Option<&Path>) -> (String, Vec<Value>) {
    let mut entries: Vec<(String, DiffEntry)> = Vec::new();

    for applied_hunk in applied {
        let key = report_key(applied_hunk);
        if let Some((_, entry)) = entries.iter_mut().find(|(existing, _)| existing == &key) {
            entry.display_path = applied_hunk.display_path.clone();
            if applied_hunk.move_path.is_some() {
                entry.move_path = applied_hunk.move_path.clone();
            }
            entry.last_kind = applied_hunk.kind;
            entry.after = applied_hunk.after.clone();
            entry.hunk_count += 1;
            let (additions, deletions) = diff_counts(&entry.before, &entry.after);
            entry.additions = additions;
            entry.deletions = deletions;
        } else {
            entries.push((
                key,
                DiffEntry {
                    file_path: applied_hunk.file_path.clone(),
                    display_path: applied_hunk.display_path.clone(),
                    move_path: applied_hunk.move_path.clone(),
                    last_kind: applied_hunk.kind,
                    before: applied_hunk.before.clone(),
                    after: applied_hunk.after.clone(),
                    additions: applied_hunk.additions,
                    deletions: applied_hunk.deletions,
                    hunk_count: 1,
                },
            ));
        }
    }

    let files = entries
        .into_iter()
        .map(|(_, entry)| {
            let patch = edit::build_unified_diff(
                &display_slash(&entry.display_path),
                &entry.before,
                &entry.after,
            );
            let entry_type = if entry.move_path.is_some() {
                "move"
            } else if entry.hunk_count == 1 {
                entry.last_kind
            } else if entry.before.is_empty() && !entry.after.is_empty() {
                "add"
            } else if !entry.before.is_empty() && entry.after.is_empty() {
                "delete"
            } else {
                "update"
            };
            let mut value = json!({
                "filePath": path_string(&entry.file_path),
                "relativePath": relative_path(&entry.display_path, root),
                "type": entry_type,
                "patch": patch,
                "additions": entry.additions,
                "deletions": entry.deletions,
            });
            if let Some(move_path) = entry.move_path {
                value["movePath"] = json!(display_slash(&move_path));
            }
            value
        })
        .collect::<Vec<_>>();

    let diff = files
        .iter()
        .filter_map(|file| file.get("patch").and_then(Value::as_str))
        .filter(|patch| !patch.is_empty())
        .collect::<Vec<_>>()
        .join("\n");

    (diff, files)
}

fn apply_patch(req: &RawRequest, ctx: &AppContext, resolved: &[ResolvedHunk]) -> Response {
    let op_id = crate::backup::new_op_id();
    let mut backed_paths = HashSet::new();
    let mut output_lines = Vec::new();
    let mut failures = Vec::new();
    let mut applied = Vec::new();

    for (index, resolved_hunk) in resolved.iter().enumerate() {
        match &resolved_hunk.hunk {
            Hunk::Add { path, contents } => {
                match apply_add(
                    req,
                    ctx,
                    resolved_hunk,
                    path,
                    contents,
                    &op_id,
                    &mut backed_paths,
                ) {
                    Ok(mut result) => {
                        result.index = index;
                        output_lines.push(format!("Created {path}"));
                        applied.push(result);
                    }
                    Err(error) => {
                        output_lines.push(format!("Failed to create {path}: {error}"));
                        add_failure(&mut failures, path, error);
                    }
                }
            }
            Hunk::Delete { path } => {
                match apply_delete(req, ctx, resolved_hunk, path, &op_id, &mut backed_paths) {
                    Ok(mut result) => {
                        result.index = index;
                        output_lines.push(format!("Deleted {path}"));
                        applied.push(result);
                    }
                    Err(error) => {
                        output_lines.push(format!("Failed to delete {path}: {error}"));
                        add_failure(&mut failures, path, error);
                    }
                }
            }
            Hunk::Update {
                path,
                move_path,
                chunks,
            } => match apply_update(req, ctx, resolved_hunk, chunks, &op_id, &mut backed_paths) {
                Ok(mut result) => {
                    result.index = index;
                    if let (Some(_), Some(move_path)) = (&resolved_hunk.move_dest, move_path) {
                        output_lines.push(format!("Updated and moved {path} → {move_path}"));
                    } else {
                        output_lines.push(format!("Updated {path}"));
                    }
                    applied.push(result);
                }
                Err(error) => {
                    output_lines.push(format!("Failed to update {path}: {error}"));
                    add_failure(&mut failures, path, error);
                }
            },
        }
    }

    if !failures.is_empty() {
        let partial = failures.len() < resolved.len();
        let failed_list = failure_paths(&failures);
        let summary = if partial {
            format!(
                "Patch partially applied — {} of {} hunk(s) succeeded. Failed: {failed_list}. Successful changes are kept; use `aft_safety` to revert if you want to abort.",
                resolved.len() - failures.len(),
                resolved.len()
            )
        } else {
            format!(
                "Patch failed — none of the {} hunk(s) applied: {failed_list}.",
                resolved.len()
            )
        };
        output_lines.push(summary);
    }

    let root = project_root_for_relative_paths(ctx);
    let (diff, files) = metadata_files(&applied, root.as_deref());
    let output = output_lines.join("\n");

    if applied.is_empty() && !failures.is_empty() {
        return Response::error_with_data(
            req.id.clone(),
            "apply_patch_failed",
            output.clone(),
            json!({
                "output": output,
                "complete": false,
                "all_failed": true,
                "partial": false,
                "failures": failures,
                "metadata": { "diff": "", "files": [] },
            }),
        );
    }

    let complete = failures.is_empty();
    let title = if complete {
        format!("Applied {} hunks", resolved.len())
    } else {
        format!("Applied {} of {} hunks", applied.len(), resolved.len())
    };

    Response::success(
        &req.id,
        json!({
            "output": output,
            "title": title,
            "complete": complete,
            "partial": !complete,
            "all_failed": false,
            "failures": failures,
            "metadata": { "diff": diff, "files": files },
        }),
    )
}

/// Handle a raw `apply_patch` request.
pub fn handle_apply_patch(req: &RawRequest, ctx: &AppContext) -> Response {
    let params = command_params(req);
    let patch_text = match params.get("patch_text").and_then(Value::as_str) {
        Some(patch_text) => patch_text,
        None => {
            return Response::error(
                &req.id,
                "invalid_request",
                "apply_patch: missing required param 'patch_text'",
            );
        }
    };

    let hunks = match parse_patch(patch_text) {
        Ok(hunks) => hunks,
        Err(error) => return Response::error(&req.id, "invalid_request", error),
    };
    if hunks.is_empty() {
        return Response::error(
            &req.id,
            "invalid_request",
            "Empty patch: no file operations found",
        );
    }

    let (resolved, affected_abs, affected_rel) = match resolve_hunks(req, ctx, hunks) {
        Ok(resolved) => resolved,
        Err(response) => return response,
    };

    if edit::wants_preview(params) {
        return build_preview_response(req, &resolved, affected_abs, affected_rel);
    }

    apply_patch(req, ctx, &resolved)
}