import { createHash, randomUUID } from "node:crypto";
import { createReadStream, createWriteStream } from "node:fs";
import fs from "node:fs/promises";
import os from "node:os";
import path from "node:path";
import { execFile } from "node:child_process";
import { promisify } from "node:util";
import type { Readable } from "node:stream";
import { pipeline } from "node:stream/promises";
import { and, eq } from "drizzle-orm";
import { environments, environmentLeases, executionWorkspaces, type Db } from "@paperclipai/db";
import type { Environment, EnvironmentLease, WorkspaceFileListMode, WorkspaceFileSource } from "@paperclipai/shared";
import { readRemoteWorkspaceAuthority } from "@paperclipai/shared";
import { HttpError, notFound, unprocessable } from "../errors.js";
import type { EnvironmentRuntimeService } from "./environment-runtime.js";
import { hasRemoteTerminationReceipt } from "./remote-execution-termination.js";
import type { OpenSavedWorkspaceArchive, SavedWorkspaceArchive } from "./saved-workspace-archive.js";

const execFileAsync = promisify(execFile);
const READ_TIMEOUT_MS = 30_000;
const MAX_HELPER_OUTPUT_BYTES = 2 * 1024 * 1024;

export interface RemoteWorkspaceFileEntry {
  kind: "file" | "directory";
  relativePath: string;
  byteSize: number | null;
  modifiedAt: string | null;
  text?: boolean;
  sha256?: string;
}

export interface RemoteWorkspaceFileListInput {
  relativePath?: string;
  mode: WorkspaceFileListMode;
  query?: string | null;
  limit: number;
  offset: number;
  maxScannedEntries: number;
  maxDepth: number;
}

export interface RemoteWorkspaceDownload {
  stream: Readable;
  byteSize: number;
  cleanup(): Promise<void>;
}

export interface RemoteWorkspaceFileAccess {
  source: WorkspaceFileSource;
  stat(relativePath: string): Promise<RemoteWorkspaceFileEntry>;
  read(relativePath: string, options: { maxBytes: number }): Promise<Buffer>;
  list(input: RemoteWorkspaceFileListInput): Promise<{
    entries: RemoteWorkspaceFileEntry[];
    scannedCount: number;
    truncated: boolean;
  }>;
  download(relativePath: string): Promise<RemoteWorkspaceDownload>;
  close(): Promise<void>;
}

export interface SavedWorkspaceFiles {
  root: string;
  savedAt: string;
  cleanup(): Promise<void>;
}

export interface RemoteWorkspaceFileOptions {
  environmentRuntime?: Pick<EnvironmentRuntimeService, "execute" | "syncOut">;
  /** Verify the exact company-owned, committed snapshot before exposing files. */
  loadSavedWorkspace?(input: {
    companyId: string;
    workspaceId: string;
    snapshotId: string;
    signal?: AbortSignal;
  }): Promise<SavedWorkspaceFiles>;
  openSavedWorkspaceArchive?: OpenSavedWorkspaceArchive;
  savedFileDownloadLimits?: Partial<SavedFileDownloadLimits>;
}

export interface RemoteWorkspaceFiles {
  open(input: { companyId: string; workspaceId: string; signal?: AbortSignal }): Promise<RemoteWorkspaceFileAccess | null>;
}

// Run the same confined helper in the execution environment and in a verified,
// disposable saved-version directory. No absolute path comes from a file caller.
export const REMOTE_WORKSPACE_FILES_SCRIPT = String.raw`
const fs = require('node:fs/promises');
const { constants } = require('node:fs');
const path = require('node:path');
const { createHash } = require('node:crypto');
const { execFile } = require('node:child_process');
const { promisify } = require('node:util');
const input = JSON.parse(process.argv[1]);
const denied = new Set(['.git','.paperclip','.paperclip-runtime','node_modules','.pnpm-store','.yarn','.cache','.turbo','.next','.vite','.vercel','dist','build','coverage','runtime-services','.runtime']);
const fail = code => { const error = new Error(code); error.code = code; throw error; };
const deniedPath = relative => {
  const parts = relative.toLowerCase().split('/');
  const file = parts.at(-1) || '';
  return parts.some(part => denied.has(part) || part === '.aws' || part === '.ssh') ||
    file === '.env' || file.startsWith('.env.') || /\.(pem|key|p12|pfx)$/.test(file) ||
    ['id_rsa','id_ed25519','.npmrc','.pypirc','.netrc','kubeconfig'].includes(file) ||
    (parts.at(-2) === '.docker' && file === 'config.json') || (parts.at(-2) === '.kube' && file === 'config');
};
const normalize = (relative, allowRoot = false) => {
  if (allowRoot && !relative) return '';
  if (typeof relative !== 'string' || !relative || relative.length > 4096 || /[\\\u0000-\u001f\u007f]/u.test(relative) ||
      path.isAbsolute(relative) || /^[a-z][a-z0-9+.-]*:/iu.test(relative) || relative.startsWith('~') ||
      relative.split('/').some(part => part === '..' || part === '.' || part === '')) fail('invalid_path');
  if (deniedPath(relative)) fail('denied_path');
  return relative;
};
const same = (a,b) => ['dev','ino','size','mtimeNs','ctimeNs'].every(key => a[key] === b[key]);
const within = (root,target) => { const relative = path.relative(root,target); return relative === '' || (relative !== '..' && !relative.startsWith('../') && !path.isAbsolute(relative)); };
(async () => {
  const rootEntry = await fs.lstat(input.root);
  if (!rootEntry.isDirectory() || rootEntry.isSymbolicLink()) fail('workspace_unavailable');
  const root = await fs.realpath(input.root);
  const confined = async (relative, allowRoot = false) => {
    relative = normalize(relative, allowRoot);
    let current = root;
    for (const part of relative ? relative.split('/') : []) {
      current = path.join(current,part);
      const stat = await fs.lstat(current);
      if (stat.isSymbolicLink()) fail('symlink_denied');
    }
    const canonical = await fs.realpath(current);
    if (!within(root,canonical) || canonical !== current) fail('outside_workspace');
    return canonical;
  };
  const entry = async (relative, withHash = false) => {
    const target = await confined(relative);
    const stat = await fs.lstat(target);
    if (!stat.isDirectory() && !stat.isFile()) fail('not_regular_file');
    const result = {kind:stat.isDirectory()?'directory':'file',relativePath:relative,byteSize:stat.isFile()?stat.size:null,modifiedAt:stat.mtime.toISOString()};
    if (stat.isFile() && input.action === 'stat') {
      const handle = await fs.open(target,constants.O_RDONLY | constants.O_NOFOLLOW | constants.O_NONBLOCK);
      try {
        const before = await handle.stat({bigint:true});
        if (!before.isFile() || before.nlink !== 1n) fail('not_regular_file');
        const sample = Buffer.alloc(4096);
        const {bytesRead} = await handle.read(sample,0,sample.length,0);
        let controls = 0;
        let nul = false;
        for (const byte of sample.subarray(0,bytesRead)) { if (!byte) nul = true; if (byte < 32 && ![9,10,13].includes(byte)) controls++; }
        result.text = !nul && (!bytesRead || controls / bytesRead < .02);
        if (withHash) { const hash = createHash('sha256'); for await (const bytes of handle.createReadStream({start:0,autoClose:false})) hash.update(bytes); result.sha256=hash.digest('hex'); }
        const after = await handle.stat({bigint:true});
        const current = await fs.lstat(target,{bigint:true});
        if (!same(before,after) || !same(after,current) || await confined(relative) !== target) fail('file_changed');
      } finally { await handle.close(); }
    }
    return result;
  };
  let result;
  if (input.action === 'stat') result=await entry(input.relativePath,input.withHash === true);
  else if (input.action === 'list') {
    const requested = input.options;
    const start = normalize(requested.relativePath || '',true);
    const startPath = await confined(start,true);
    if (!(await fs.stat(startPath)).isDirectory()) fail('not_directory');
    const maxScanned = Math.min(5000,Math.max(1,requested.maxScannedEntries));
    const maxDepth = Math.min(20,Math.max(0,requested.maxDepth));
    const limit = Math.min(100,Math.max(1,requested.limit));
    const offset = Math.min(10000,Math.max(0,requested.offset));
    const query = (requested.query || '').toLowerCase();
    let scannedCount=0,truncated=false;
    const entries=[];
    const matches = relative => !query || relative.toLowerCase().includes(query);
    const add = async relative => {
      try { const value=await entry(relative); if(matches(relative)) entries.push(value); }
      catch(error) { if(!['ENOENT','ENOTDIR','denied_path','symlink_denied','not_regular_file'].includes(error.code)) throw error; }
    };
    if (requested.mode === 'changed') {
      let stdout;
      try { ({stdout}=await promisify(execFile)('git',['-c','core.fsmonitor=false','-c','core.hooksPath=/dev/null','-C',root,'status','--porcelain=v1','-z','--untracked-files=all'],{encoding:'utf8',timeout:10000,maxBuffer:1048576,env:{...process.env,GIT_OPTIONAL_LOCKS:'0',GIT_CONFIG_NOSYSTEM:'1',GIT_CONFIG_GLOBAL:'/dev/null'}})); }
      catch { fail('changed_unavailable'); }
      const tokens=stdout.split('\0').filter(Boolean);
      for(let i=0;i<tokens.length;i++) {
        if(++scannedCount>maxScanned) {truncated=true;break;}
        const token=tokens[i];
        const status=token.slice(0,2),relative=token.slice(3);
        if(status.includes('R')||status.includes('C')) i++;
        if(relative && !deniedPath(relative)) await add(relative);
      }
    } else {
      const immediate=requested.mode==='all'&&!query;
      const queue=[{relative:start,depth:0}];
      scan: while(queue.length) {
        const current=queue.shift();
        const directory=await confined(current.relative,true);
        const children=await fs.readdir(directory,{withFileTypes:true});
        children.sort((a,b)=>immediate&&a.isDirectory()!==b.isDirectory()?(a.isDirectory()?-1:1):a.name.localeCompare(b.name));
        for(const child of children) {
          if(++scannedCount>maxScanned) {truncated=true;break scan;}
          const relative=current.relative?current.relative+'/'+child.name:child.name;
          if(deniedPath(relative)||child.isSymbolicLink()||/[\\\u0000-\u001f\u007f]/u.test(relative)) continue;
          if(child.isDirectory()) {
            if(immediate) await add(relative);
            else if(current.depth<maxDepth) queue.push({relative,depth:current.depth+1});
            else truncated=true;
          } else if(child.isFile()) await add(relative);
          if(immediate&&entries.length>offset+limit) {truncated=true;break scan;}
        }
      }
    }
    if(requested.mode==='recent') entries.sort((a,b)=>(b.modifiedAt||'').localeCompare(a.modifiedAt||'')||a.relativePath.localeCompare(b.relativePath));
    else if(requested.mode==='changed') entries.sort((a,b)=>a.relativePath.localeCompare(b.relativePath));
    result={entries:entries.slice(offset,offset+limit),scannedCount:Math.min(scannedCount,maxScanned),truncated:truncated||entries.length>offset+limit};
  } else fail('invalid_operation');
  if(await fs.realpath(input.root)!==root) fail('workspace_unavailable');
  process.stdout.write(JSON.stringify(result));
})().catch(error => {
  const allowed=new Set(['invalid_path','denied_path','symlink_denied','outside_workspace','workspace_unavailable','not_regular_file','not_directory','file_changed','changed_unavailable','ENOENT','ENOTDIR']);
  process.stderr.write(allowed.has(error.code)?error.code:'remote_read_failed');
  process.exitCode=1;
});
`;

function fileFailure(code: string): HttpError {
  if (["ENOENT", "ENOTDIR"].includes(code)) return notFound("Workspace file not found", { code: "not_found" });
  if (["denied_path", "symlink_denied", "outside_workspace", "invalid_path"].includes(code)) {
    return new HttpError(403, "Workspace file path is denied", { code });
  }
  const safe = new Set(["workspace_unavailable", "workspace_changed", "not_regular_file", "not_directory", "file_changed", "changed_unavailable", "too_large"]);
  return unprocessable("Workspace files are unavailable", { code: safe.has(code) ? code : "workspace_unavailable" });
}

function parseFileEntry(value: unknown): RemoteWorkspaceFileEntry {
  const entry = value as Partial<RemoteWorkspaceFileEntry> | null;
  if (!entry || !["file", "directory"].includes(entry.kind ?? "") || typeof entry.relativePath !== "string" ||
    !entry.relativePath || entry.relativePath.length > 4096 || /[\\\u0000-\u001f\u007f]/u.test(entry.relativePath) ||
    path.posix.isAbsolute(entry.relativePath) || entry.relativePath.split("/").some(part => !part || part === "." || part === "..") ||
    (entry.kind === "file" ? !Number.isSafeInteger(entry.byteSize) || entry.byteSize! < 0 : entry.byteSize !== null) ||
    (entry.modifiedAt !== null && (typeof entry.modifiedAt !== "string" || !Number.isFinite(Date.parse(entry.modifiedAt)))) ||
    (entry.text !== undefined && typeof entry.text !== "boolean") ||
    (entry.sha256 !== undefined && !/^[a-f0-9]{64}$/.test(entry.sha256))) throw fileFailure("workspace_unavailable");
  return entry as RemoteWorkspaceFileEntry;
}

function parseHelperResult(action: "stat" | "list", value: unknown, withHash: boolean): unknown {
  if (action === "stat") {
    const entry = parseFileEntry(value);
    if (withHash && entry.kind === "file" && !entry.sha256) throw fileFailure("workspace_unavailable");
    return entry;
  }
  const list = value as { entries?: unknown; scannedCount?: unknown; truncated?: unknown } | null;
  if (!list || !Array.isArray(list.entries) || list.entries.length > 100 ||
    !Number.isSafeInteger(list.scannedCount) || Number(list.scannedCount) < 0 || Number(list.scannedCount) > 5000 ||
    typeof list.truncated !== "boolean") throw fileFailure("workspace_unavailable");
  return { entries: list.entries.map(parseFileEntry), scannedCount: list.scannedCount, truncated: list.truncated };
}

async function verifyDownload(file: string, expected: RemoteWorkspaceFileEntry): Promise<number> {
  const handle = await fs.open(file, "r");
  try {
    const stat = await handle.stat();
    if (!stat.isFile() || stat.size !== expected.byteSize) throw fileFailure("file_changed");
    const hash = createHash("sha256");
    for await (const bytes of handle.createReadStream({ autoClose: false })) hash.update(bytes);
    if (expected.sha256 && hash.digest("hex") !== expected.sha256) throw fileFailure("file_changed");
    return stat.size;
  } finally { await handle.close(); }
}

class ArchiveReadFailure extends Error {
  constructor(readonly code: string) { super(code); }
}

const ARCHIVE_DENIED_NAMES = new Set([".git", ".paperclip", ".paperclip-runtime", "node_modules", ".pnpm-store", ".yarn", ".cache",
  ".turbo", ".next", ".vite", ".vercel", "dist", "build", "coverage", "runtime-services", ".runtime"]);
const ARCHIVE_LIST_SKIPPED = new Set(["ENOENT", "ENOTDIR", "denied_path", "symlink_denied", "not_regular_file"]);
const archiveFail = (code: string): never => { throw new ArchiveReadFailure(code); };

function archiveDeniedPath(relative: string) {
  const parts = relative.toLowerCase().split("/");
  const file = parts.at(-1) || "";
  return parts.some(part => ARCHIVE_DENIED_NAMES.has(part) || part === ".aws" || part === ".ssh")
    || file === ".env" || file.startsWith(".env.") || /\.(pem|key|p12|pfx)$/.test(file)
    || ["id_rsa", "id_ed25519", ".npmrc", ".pypirc", ".netrc", "kubeconfig"].includes(file)
    || (parts.at(-2) === ".docker" && file === "config.json") || (parts.at(-2) === ".kube" && file === "config");
}

function archiveNormalize(relative: unknown, allowRoot = false): string {
  if (allowRoot && !relative) return "";
  if (typeof relative !== "string" || !relative || relative.length > 4096 || /[\\\u0000-\u001f\u007f]/u.test(relative)
    || path.isAbsolute(relative) || /^[a-z][a-z0-9+.-]*:/iu.test(relative) || relative.startsWith("~")
    || relative.split("/").some(part => part === ".." || part === "." || part === "")) archiveFail("invalid_path");
  if (archiveDeniedPath(relative as string)) archiveFail("denied_path");
  return relative as string;
}

function archiveConfined(archive: SavedWorkspaceArchive, relative: string) {
  let current = "";
  for (const part of relative.split("/")) {
    if (current && archive.entry(current)?.type !== "directory") archiveFail("ENOTDIR");
    current = current ? `${current}/${part}` : part;
    const entry = archive.entry(current);
    if (!entry) archiveFail("ENOENT");
    if (entry!.type === "symlink") archiveFail("symlink_denied");
  }
  return archive.entry(relative)!;
}

function archiveEntryInfo(archive: SavedWorkspaceArchive, relativePath: unknown) {
  const relative = archiveNormalize(relativePath);
  const entry = archiveConfined(archive, relative);
  if (entry.type !== "directory" && entry.type !== "file") archiveFail("not_regular_file");
  return { entry, result: { kind: entry.type === "directory" ? "directory" : "file", relativePath: relative,
    byteSize: entry.type === "file" ? entry.size : null, modifiedAt: archive.savedAt } as RemoteWorkspaceFileEntry };
}

async function archiveEntry(archive: SavedWorkspaceArchive, relativePath: unknown, action: "stat" | "list", withHash: boolean,
  signal?: AbortSignal): Promise<RemoteWorkspaceFileEntry> {
  const { entry, result } = archiveEntryInfo(archive, relativePath);
  if (entry.type === "file" && action === "stat") {
    const chunks: Buffer[] = [];
    for await (const chunk of await archive.read(entry, 0, Math.min(4096, entry.size), signal)) {
      chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
    }
    const sample = Buffer.concat(chunks);
    let controls = 0, nul = false;
    for (const byte of sample) { if (!byte) nul = true; if (byte < 32 && ![9, 10, 13].includes(byte)) controls++; }
    result.text = !nul && (!sample.length || controls / sample.length < 0.02);
    if (withHash) result.sha256 = entry.sha256!;
  }
  return result;
}

function archiveList(archive: SavedWorkspaceArchive, requested: RemoteWorkspaceFileListInput) {
  const start = archiveNormalize(requested.relativePath || "", true);
  if (start && archiveConfined(archive, start).type !== "directory") archiveFail("not_directory");
  const maxScanned = Math.min(5000, Math.max(1, requested.maxScannedEntries));
  const maxDepth = Math.min(20, Math.max(0, requested.maxDepth));
  const limit = Math.min(100, Math.max(1, requested.limit));
  const offset = Math.min(10000, Math.max(0, requested.offset));
  const query = (requested.query || "").toLowerCase();
  let scannedCount = 0, truncated = false;
  const entries: RemoteWorkspaceFileEntry[] = [];
  const add = (relative: string) => {
    try {
      const { result } = archiveEntryInfo(archive, relative);
      if (!query || relative.toLowerCase().includes(query)) entries.push(result);
    } catch (error) {
      if (!(error instanceof ArchiveReadFailure) || !ARCHIVE_LIST_SKIPPED.has(error.code)) throw error;
    }
  };
  const immediate = requested.mode === "all" && !query;
  const queue = [{ relative: start, depth: 0 }];
  scan: while (queue.length) {
    const current = queue.shift()!;
    const sorted = archive.children(current.relative);
    const passes = immediate ? [(entry: { type: string }) => entry.type === "directory", (entry: { type: string }) => entry.type !== "directory"]
      : [() => true];
    for (const include of passes) for (const child of sorted) {
      if (!include(child)) continue;
      if (++scannedCount > maxScanned) { truncated = true; break scan; }
      const relative = current.relative ? `${current.relative}/${child.name}` : child.name;
      if (archiveDeniedPath(relative) || child.type === "symlink" || /[\\\u0000-\u001f\u007f]/u.test(relative)) continue;
      if (child.type === "directory") {
        if (immediate) add(relative);
        else if (current.depth < maxDepth) queue.push({ relative, depth: current.depth + 1 });
        else truncated = true;
      } else if (child.type === "file") add(relative);
      if (immediate && entries.length > offset + limit) { truncated = true; break scan; }
    }
  }
  if (requested.mode === "recent") entries.sort((a, b) => (b.modifiedAt || "").localeCompare(a.modifiedAt || "")
    || a.relativePath.localeCompare(b.relativePath));
  return { entries: entries.slice(offset, offset + limit), scannedCount: Math.min(scannedCount, maxScanned),
    truncated: truncated || entries.length > offset + limit };
}

export type SavedFileDownloadLimits = { maxReservedBytes: number; freeSpaceMarginBytes: number; availableBytes: () => Promise<bigint> };
const SAVED_FILE_DOWNLOAD_LIMITS: SavedFileDownloadLimits = {
  maxReservedBytes: 4 * 1024 * 1024 * 1024, freeSpaceMarginBytes: 256 * 1024 * 1024,
  availableBytes: async () => { const disk = await fs.statfs(os.tmpdir(), { bigint: true }); return disk.bavail * disk.bsize; },
};
let savedFileDownloadReservedBytes = 0;

async function archiveRead(archive: SavedWorkspaceArchive, relativePath: string, expected: RemoteWorkspaceFileEntry, maxBytes: number,
  signal?: AbortSignal): Promise<Buffer> {
  const entry = archive.entry(relativePath);
  if (!entry || entry.type !== "file" || entry.size !== expected.byteSize) throw fileFailure("file_changed");
  if (entry.size > maxBytes) throw fileFailure("too_large");
  const chunks: Buffer[] = [], hash = createHash("sha256");
  let size = 0;
  for await (const chunk of await archive.read(entry, 0, entry.size, signal)) {
    const bytes = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk);
    size += bytes.length;
    if (size > entry.size) throw fileFailure("file_changed");
    hash.update(bytes); chunks.push(bytes);
  }
  if (size !== entry.size || hash.digest("hex") !== entry.sha256) throw fileFailure("file_changed");
  return Buffer.concat(chunks);
}

async function archiveDownload(archive: SavedWorkspaceArchive, relativePath: string, expected: RemoteWorkspaceFileEntry,
  checkCurrent: () => Promise<void>, limits: SavedFileDownloadLimits, signal?: AbortSignal): Promise<RemoteWorkspaceDownload> {
  const entry = archive.entry(relativePath);
  if (!entry || entry.type !== "file" || entry.size !== expected.byteSize) throw fileFailure("file_changed");
  if (entry.size > limits.maxReservedBytes) throw fileFailure("too_large");
  if (savedFileDownloadReservedBytes + entry.size > limits.maxReservedBytes) throw fileFailure("workspace_unavailable");
  savedFileDownloadReservedBytes += entry.size;
  let released = false;
  const release = () => { if (!released) { released = true; savedFileDownloadReservedBytes -= entry.size; } };
  try {
    if (await limits.availableBytes() < BigInt(savedFileDownloadReservedBytes + limits.freeSpaceMarginBytes)) {
      throw fileFailure("workspace_unavailable");
    }
  } catch (error) { release(); throw error; }
  let directory: string | undefined;
  const cleanup = async () => {
    try { if (directory) await fs.rm(directory, { recursive: true, force: true }); }
    finally { release(); }
  };
  try {
    directory = await fs.mkdtemp(path.join(os.tmpdir(), "paperclip-saved-file-"));
    const file = path.join(directory, "file");
    await pipeline(await archive.read(entry, 0, entry.size, signal), createWriteStream(file, { flags: "wx", mode: 0o600 }),
      ...(signal ? [{ signal }] : []));
    await verifyDownload(file, expected);
    await checkCurrent();
    return { stream: createReadStream(file), byteSize: entry.size, cleanup };
  } catch (error) { await cleanup(); throw error; }
}

export function createRemoteWorkspaceFiles(db: Db, options: RemoteWorkspaceFileOptions = {}): RemoteWorkspaceFiles {
  return {
    async open(input) {
      input.signal?.throwIfAborted();
      const [workspace] = await db.select().from(executionWorkspaces).where(and(
        eq(executionWorkspaces.companyId, input.companyId), eq(executionWorkspaces.id, input.workspaceId),
      )).limit(1);
      if (!workspace) throw notFound("Workspace not found");
      const authority = readRemoteWorkspaceAuthority(workspace.metadata);
      if (!authority) return null;
      const initialAuthority = JSON.stringify(authority);
      let saved: SavedWorkspaceFiles | undefined;
      let archive: SavedWorkspaceArchive | undefined;
      let savedLocationReleased = false;
      const checkCurrent = async () => {
        input.signal?.throwIfAborted();
        const [current] = await db.select({ metadata: executionWorkspaces.metadata }).from(executionWorkspaces).where(and(
          eq(executionWorkspaces.companyId, input.companyId), eq(executionWorkspaces.id, input.workspaceId),
        )).limit(1);
        const currentAuthority = current ? readRemoteWorkspaceAuthority(current.metadata) : null;
        // An extracted committed save no longer depends on the allocation.
        // Allow only its monotonic location removal; every logical field stays
        // pinned, and a foreign or reintroduced location remains a conflict.
        if ((saved || archive) && authority.location && currentAuthority?.location === null
          && JSON.stringify({ ...currentAuthority, location: authority.location }) === initialAuthority) {
          savedLocationReleased = true;
          return;
        }
        if (!currentAuthority || JSON.stringify(currentAuthority) !== initialAuthority
          || savedLocationReleased && currentAuthority.location !== null) {
          throw fileFailure("workspace_changed");
        }
      };
      let environment: Environment | undefined;
      let lease: EnvironmentLease | undefined;
      let source: WorkspaceFileSource;
      let root: string;
      const savedReady = Boolean(options.loadSavedWorkspace || options.openSavedWorkspaceArchive);
      const loadSaved = async () => {
        if (!authority.snapshotId || authority.dirty || authority.writerRunId || !savedReady) {
          throw fileFailure("workspace_unavailable");
        }
        const scope = { companyId: input.companyId, workspaceId: input.workspaceId, snapshotId: authority.snapshotId,
          ...(input.signal ? { signal: input.signal } : {}) };
        if (options.openSavedWorkspaceArchive) {
          try { archive = await options.openSavedWorkspaceArchive(scope); }
          catch (error) {
            if (error instanceof HttpError) throw error;
            if (error instanceof Error && error.message === "remote_workspace_archive_entry_limit") throw fileFailure("too_large");
            if (error instanceof Error && /^remote_workspace_(snapshot|archive)_/.test(error.message)) throw fileFailure("workspace_unavailable");
            throw error;
          }
          return { root: "", source: { kind: "saved", savedAt: archive.savedAt, snapshotId: authority.snapshotId } as WorkspaceFileSource };
        }
        saved = await options.loadSavedWorkspace!(scope);
        return { root: saved.root, source: { kind: "saved", savedAt: saved.savedAt, snapshotId: authority.snapshotId } as WorkspaceFileSource };
      };
      const extractedRoot = async () => {
        if (saved) return saved.root;
        if (!options.loadSavedWorkspace || !authority.snapshotId) throw fileFailure("changed_unavailable");
        try {
          saved = await options.loadSavedWorkspace({ companyId: input.companyId, workspaceId: input.workspaceId, snapshotId: authority.snapshotId,
            ...(input.signal ? { signal: input.signal } : {}) });
        } catch (error) {
          if (error instanceof HttpError && error.status === 422) throw fileFailure("changed_unavailable");
          throw error;
        }
        return saved.root;
      };
      // A final save clears dirty state and writer authority. Its accepted
      // bytes do not depend on an allocation that can already be closing.
      if (authority.snapshotId && !authority.dirty && !authority.writerRunId && savedReady) {
        ({ root, source } = await loadSaved());
      } else if (authority.location) {
        const [leaseRow] = await db.select().from(environmentLeases).where(and(
          eq(environmentLeases.companyId, input.companyId), eq(environmentLeases.id, authority.location.leaseId),
        )).limit(1);
        const [environmentRow] = await db.select().from(environments).where(eq(environments.id, authority.location.environmentId)).limit(1);
        if (!leaseRow || !environmentRow || leaseRow.environmentId !== environmentRow.id ||
          leaseRow.providerLeaseId !== authority.location.providerLeaseId ||
          leaseRow.metadata?.remoteCwd !== authority.location.remoteCwd) throw fileFailure("workspace_unavailable");
        if (hasRemoteTerminationReceipt(leaseRow)
            && (leaseRow.metadata?.remoteExecutionTermination as { state?: string } | undefined)?.state === "stopped") {
          ({ root, source } = await loadSaved());
        } else {
          if (!options.environmentRuntime || !["active", "retained", "pending_cleanup"].includes(leaseRow.status)) {
            throw fileFailure("workspace_unavailable");
          }
          lease = leaseRow as EnvironmentLease;
          environment = environmentRow as Environment;
          root = authority.location.remoteCwd;
          source = { kind: "live", savedAt: null, snapshotId: null };
        }
      } else {
        ({ root, source } = await loadSaved());
      }
      let closed = false;
      const close = async () => { if (closed) return; closed = true; archive?.close(); await saved?.cleanup(); };
      const execute = async <T>(action: "stat" | "list", args: Record<string, unknown>): Promise<T> => {
        if (closed) throw fileFailure("workspace_unavailable");
        await checkCurrent();
        const changedList = action === "list" && (args.options as RemoteWorkspaceFileListInput | undefined)?.mode === "changed";
        if (archive && !changedList) {
          let value: unknown;
          try {
            value = action === "stat"
              ? await archiveEntry(archive, args.relativePath, "stat", args.withHash === true, input.signal)
              : archiveList(archive, args.options as RemoteWorkspaceFileListInput);
          } catch (error) { throw fileFailure(error instanceof ArchiveReadFailure ? error.code : "workspace_unavailable"); }
          await checkCurrent();
          try { return parseHelperResult(action, value, args.withHash === true) as T; }
          catch { throw fileFailure("workspace_unavailable"); }
        }
        const helperRoot = archive ? await extractedRoot() : root;
        const payload = JSON.stringify({ root: helperRoot, action, ...args });
        let stdout: string;
        if (saved) {
          try {
            ({ stdout } = await execFileAsync(process.execPath, ["--input-type=commonjs", "-e", REMOTE_WORKSPACE_FILES_SCRIPT, payload], {
              cwd: helperRoot, timeout: READ_TIMEOUT_MS, maxBuffer: MAX_HELPER_OUTPUT_BYTES,
              signal: input.signal, env: { ...process.env, NODE_OPTIONS: "", NODE_PATH: "" },
            }));
          } catch (error) { throw fileFailure(String((error as { stderr?: string }).stderr ?? "workspace_unavailable").trim()); }
        } else {
          const result = await options.environmentRuntime!.execute({
            environment: environment!, lease: lease!, command: "node",
            args: ["--input-type=commonjs", "-e", REMOTE_WORKSPACE_FILES_SCRIPT, payload],
            cwd: root, timeoutMs: READ_TIMEOUT_MS, bypassSession: true, env: { NODE_OPTIONS: "", NODE_PATH: "" },
          }).catch(() => { throw fileFailure("workspace_unavailable"); });
          if (result.timedOut || result.exitCode !== 0) throw fileFailure(result.timedOut ? "workspace_unavailable" : result.stderr.trim());
          stdout = result.stdout;
        }
        await checkCurrent();
        try { return parseHelperResult(action, JSON.parse(stdout), args.withHash === true) as T; }
        catch { throw fileFailure("workspace_unavailable"); }
      };
      const stat = (relativePath: string) => execute<RemoteWorkspaceFileEntry>("stat", { relativePath });
      const download = async (relativePath: string): Promise<RemoteWorkspaceDownload> => {
        const expected = await execute<RemoteWorkspaceFileEntry>("stat", { relativePath, withHash: true });
        if (expected.kind !== "file") throw fileFailure("not_regular_file");
        if (archive) return archiveDownload(archive, relativePath, expected, checkCurrent,
          { ...SAVED_FILE_DOWNLOAD_LIMITS, ...options.savedFileDownloadLimits }, input.signal);
        if (saved) {
          await checkCurrent();
          const file = path.join(root, ...relativePath.split("/"));
          return { stream: createReadStream(file), byteSize: expected.byteSize!, cleanup: async () => {} };
        }
        const directory = await fs.mkdtemp(path.join(os.tmpdir(), "paperclip-workspace-file-"));
        const cleanup = async () => { await fs.rm(directory, { recursive: true, force: true }); };
        try {
          await options.environmentRuntime!.syncOut({ environment: environment!, lease: lease!, operations: [{
            operationId: `workspace-file:${randomUUID()}`,
            files: [{ sourcePath: path.posix.join(root, relativePath), targetPath: path.join(directory, "file"), kind: "file", mode: 0o600 }],
          }] }).catch(() => { throw fileFailure("workspace_unavailable"); });
          await verifyDownload(path.join(directory, "file"), expected);
          await checkCurrent();
          return { stream: createReadStream(path.join(directory, "file")), byteSize: expected.byteSize!, cleanup };
        } catch (error) { await cleanup(); throw error; }
      };
      return {
        source, stat, close,
        list: listInput => execute("list", { options: listInput }),
        async read(relativePath, readOptions) {
          const expected = await stat(relativePath);
          if (expected.kind !== "file") throw fileFailure("not_regular_file");
          if (expected.byteSize! > readOptions.maxBytes) throw fileFailure("too_large");
          if (archive) {
            const bytes = await archiveRead(archive, relativePath, expected, readOptions.maxBytes, input.signal);
            await checkCurrent();
            return bytes;
          }
          const transfer = await download(relativePath);
          try {
            const chunks: Buffer[] = [];
            let size = 0;
            for await (const chunk of transfer.stream) {
              input.signal?.throwIfAborted();
              const bytes = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk);
              size += bytes.length;
              if (size > readOptions.maxBytes) throw fileFailure("too_large");
              chunks.push(bytes);
            }
            await checkCurrent();
            return Buffer.concat(chunks);
          } finally { transfer.stream.destroy(); await transfer.cleanup(); }
        },
        download,
      };
    },
  };
}