import { execFile } from "node:child_process";
import fs from "node:fs/promises";
import path from "node:path";
import { promisify } from "node:util";
import { and, desc, eq, inArray, isNull } from "drizzle-orm";
import type { Db } from "@paperclipai/db";
import { executionWorkspaces, issues, projects, projectWorkspaces } from "@paperclipai/db";
import type {
  ResolvedWorkspaceResource,
  WorkspaceFileContent,
  WorkspaceFileListItem,
  WorkspaceFileListMode,
  WorkspaceFileListResponse,
  WorkspaceFilePreviewKind,
  WorkspaceFileSelector,
  WorkspaceFileWorkspaceKind,
} from "@paperclipai/shared";
import { HttpError, notFound, unprocessable } from "../errors.js";

export const WORKSPACE_FILE_TEXT_MAX_BYTES = 512 * 1024;
export const WORKSPACE_FILE_MEDIA_MAX_BYTES = 10 * 1024 * 1024;
export const WORKSPACE_FILE_LIST_DEFAULT_LIMIT = 25;
export const WORKSPACE_FILE_LIST_MAX_LIMIT = 100;
export const WORKSPACE_FILE_LIST_MAX_SCANNED_ENTRIES = 5_000;
const MAX_RELATIVE_PATH_BYTES = 4096;
const TEXT_SNIFF_BYTES = 4096;
const MAX_LIST_DEPTH = 20;
const GIT_STATUS_MAX_BUFFER_BYTES = 1024 * 1024;
const execFileAsync = promisify(execFile);
const LOCAL_PROJECT_WORKSPACE_SOURCE_TYPES = new Set(["local_path", "non_git_path", "git_repo", "git_worktree"]);

const DENIED_SEGMENTS = new Set([
  ".git",
  ".paperclip",
  "node_modules",
  ".pnpm-store",
  ".yarn",
  ".cache",
  ".turbo",
  ".next",
  ".vite",
  ".vercel",
  "dist",
  "build",
  "coverage",
  "runtime-services",
  ".runtime",
]);

const TEXT_EXTENSIONS = new Set([
  ".c",
  ".cc",
  ".conf",
  ".cpp",
  ".css",
  ".csv",
  ".go",
  ".h",
  ".html",
  ".htm",
  ".java",
  ".js",
  ".json",
  ".jsx",
  ".log",
  ".md",
  ".mjs",
  ".py",
  ".rb",
  ".rs",
  ".sh",
  ".sql",
  ".svg",
  ".toml",
  ".ts",
  ".tsx",
  ".txt",
  ".xml",
  ".yaml",
  ".yml",
]);

const IMAGE_CONTENT_TYPES = new Map([
  [".gif", "image/gif"],
  [".jpeg", "image/jpeg"],
  [".jpg", "image/jpeg"],
  [".png", "image/png"],
  [".webp", "image/webp"],
]);

const VIDEO_CONTENT_TYPES = new Map([
  [".m4v", "video/mp4"],
  [".mov", "video/quicktime"],
  [".mp4", "video/mp4"],
  [".webm", "video/webm"],
]);

type IssueRow = typeof issues.$inferSelect;
type ExecutionWorkspaceRow = typeof executionWorkspaces.$inferSelect;
type ProjectWorkspaceRow = typeof projectWorkspaces.$inferSelect;

type WorkspaceCandidate = {
  workspaceKind: WorkspaceFileWorkspaceKind;
  workspaceId: string;
  projectId?: string | null;
  projectName?: string | null;
  provider: string;
  label: string;
  rootPath: string | null;
  remote: boolean;
};

type NormalizedPath = {
  relativePath: string;
  segments: string[];
};

type LocalResolvedFile = {
  resource: ResolvedWorkspaceResource;
  realPath: string;
};

type LocalResolvedDirectory = {
  resource: ResolvedWorkspaceResource;
  realPath: string;
  rootReal: string;
};

type AutoDiscovered<T> =
  | { state: "none" }
  | { state: "one"; value: T }
  | { state: "ambiguous"; count: number };

type WorkspaceFileListQueryInput = {
  workspace?: WorkspaceFileSelector | null;
  projectId?: string | null;
  workspaceId?: string | null;
  path?: string | null;
  mode?: WorkspaceFileListMode | null;
  q?: string | null;
  limit?: number | null;
  offset?: number | null;
};

type WorkspaceTargetInput = {
  projectId?: string | null;
  workspaceId?: string | null;
};

function previewCapForKind(kind: WorkspaceFilePreviewKind) {
  return kind === "image" || kind === "video" || kind === "pdf"
    ? WORKSPACE_FILE_MEDIA_MAX_BYTES
    : WORKSPACE_FILE_TEXT_MAX_BYTES;
}

function relativePathFromReal(rootReal: string, targetReal: string) {
  return path.relative(rootReal, targetReal).split(path.sep).join(path.posix.sep);
}

function isInsideRoot(rootReal: string, targetReal: string) {
  const realRelative = path.relative(rootReal, targetReal);
  return realRelative === "" || (!realRelative.startsWith("..") && !path.isAbsolute(realRelative));
}

function normalizeWorkspaceRelativePath(input: string): NormalizedPath {
  const trimmed = input.trim();
  if (!trimmed) throw unprocessable("Workspace file path is required", { code: "invalid_path" });
  if (Buffer.byteLength(trimmed, "utf8") > MAX_RELATIVE_PATH_BYTES) {
    throw unprocessable("Workspace file path is too long", { code: "invalid_path" });
  }
  if (trimmed.includes("\0")) throw unprocessable("Workspace file path contains an invalid character", { code: "invalid_path" });
  if (/^file:\/\//i.test(trimmed)) throw unprocessable("File URLs are not supported", { code: "invalid_path" });
  if (/^[a-zA-Z]:/.test(trimmed)) throw unprocessable("Windows drive paths are not supported", { code: "invalid_path" });
  if (trimmed.startsWith("~")) throw unprocessable("Home-relative paths are not supported", { code: "invalid_path" });
  if (trimmed.includes("\\")) throw unprocessable("Workspace file paths must use forward slashes", { code: "invalid_path" });
  if (path.posix.isAbsolute(trimmed)) throw unprocessable("Workspace file path must be relative", { code: "invalid_path" });

  const normalizedRaw = path.posix.normalize(trimmed);
  const normalized = normalizedRaw.endsWith("/") ? normalizedRaw.replace(/\/+$/, "") : normalizedRaw;
  if (normalized === "." || normalized === ".." || normalized.startsWith("../")) {
    throw new HttpError(403, "Workspace file path is outside the workspace", { code: "outside_workspace" });
  }

  return {
    relativePath: normalized,
    segments: normalized.split("/").filter(Boolean),
  };
}

function denyReasonForPathSegments(segments: string[]): string | null {
  const lowerSegments = segments.map((segment) => segment.toLowerCase());
  if (lowerSegments.some((segment) => DENIED_SEGMENTS.has(segment))) return "denied_path_segment";

  const fileName = lowerSegments.at(-1) ?? "";
  if (fileName === ".env" || fileName.startsWith(".env.")) return "denied_secret";
  if (fileName.endsWith(".pem") || fileName.endsWith(".key") || fileName.endsWith(".p12") || fileName.endsWith(".pfx")) {
    return "denied_secret";
  }
  if (["id_rsa", "id_ed25519", ".npmrc", ".pypirc", ".netrc", "kubeconfig"].includes(fileName)) return "denied_secret";
  if (lowerSegments.includes(".aws") || lowerSegments.includes(".ssh")) return "denied_secret";
  if (lowerSegments.length >= 2 && lowerSegments.at(-2) === ".docker" && fileName === "config.json") return "denied_secret";
  if (lowerSegments.length >= 2 && lowerSegments.at(-2) === ".kube" && fileName === "config") return "denied_secret";

  return null;
}

function throwIfDenied(segments: string[]) {
  const denialReason = denyReasonForPathSegments(segments);
  if (denialReason) {
    throw new HttpError(403, "Workspace file path is denied by policy", { code: denialReason });
  }
}

function shouldPruneSegments(segments: string[]) {
  return denyReasonForPathSegments(segments) != null;
}

function contentTypeForPath(filePath: string): string | null {
  const ext = path.extname(filePath).toLowerCase();
  if (IMAGE_CONTENT_TYPES.has(ext)) return IMAGE_CONTENT_TYPES.get(ext) ?? null;
  if (VIDEO_CONTENT_TYPES.has(ext)) return VIDEO_CONTENT_TYPES.get(ext) ?? null;
  if (ext === ".pdf") return "application/pdf";
  if (ext === ".svg") return "image/svg+xml";
  if (ext === ".html" || ext === ".htm") return "text/html";
  if (TEXT_EXTENSIONS.has(ext)) return "text/plain; charset=utf-8";
  return null;
}

function previewKindForKnownContentType(contentType: string | null): WorkspaceFilePreviewKind | null {
  if (!contentType) return null;
  if (contentType.startsWith("image/") && contentType !== "image/svg+xml") return "image";
  if (contentType.startsWith("video/")) return "video";
  if (contentType === "application/pdf") return "pdf";
  if (contentType === "text/html") return "unsupported";
  if (contentType === "image/svg+xml" || contentType.startsWith("text/")) return "text";
  return "unsupported";
}

function listItemFromStat(input: {
  candidate: WorkspaceCandidate;
  relativePath: string;
  stat: { size: number; mtime: Date };
}): WorkspaceFileListItem | null {
  const contentType = contentTypeForPath(input.relativePath);
  const previewKind = previewKindForKnownContentType(contentType);
  if (!previewKind || previewKind === "unsupported") return null;
  if (input.stat.size > previewCapForKind(previewKind)) return null;

  return {
    kind: "file",
    provider: input.candidate.provider,
    title: path.posix.basename(input.relativePath),
    relativePath: input.relativePath,
    displayPath: input.candidate.projectName ? `${input.candidate.projectName} / ${input.relativePath}` : input.relativePath,
    workspaceLabel: input.candidate.label,
    workspaceKind: input.candidate.workspaceKind,
    workspaceId: input.candidate.workspaceId,
    projectId: input.candidate.projectId ?? null,
    projectName: input.candidate.projectName ?? null,
    contentType: contentType ?? (previewKind === "text" ? "text/plain; charset=utf-8" : "application/octet-stream"),
    byteSize: input.stat.size,
    modifiedAt: input.stat.mtime.toISOString(),
    previewKind,
    capabilities: {
      preview: true,
      download: false,
      listChildren: false,
    },
  };
}

function listItemFromDirectory(input: {
  candidate: WorkspaceCandidate;
  relativePath: string;
  stat?: { mtime: Date };
}): WorkspaceFileListItem {
  return {
    kind: "directory",
    provider: input.candidate.provider,
    title: path.posix.basename(input.relativePath),
    relativePath: input.relativePath,
    displayPath: input.candidate.projectName ? `${input.candidate.projectName} / ${input.relativePath}/` : `${input.relativePath}/`,
    workspaceLabel: input.candidate.label,
    workspaceKind: input.candidate.workspaceKind,
    workspaceId: input.candidate.workspaceId,
    projectId: input.candidate.projectId ?? null,
    projectName: input.candidate.projectName ?? null,
    contentType: null,
    byteSize: null,
    modifiedAt: input.stat?.mtime.toISOString() ?? null,
    previewKind: "unsupported",
    capabilities: {
      preview: false,
      download: false,
      listChildren: true,
    },
  };
}

function looksLikeText(buffer: Buffer) {
  if (buffer.length === 0) return true;
  let controlBytes = 0;
  for (const byte of buffer) {
    if (byte === 0) return false;
    if (byte < 32 && byte !== 9 && byte !== 10 && byte !== 13) controlBytes += 1;
  }
  return controlBytes / buffer.length < 0.02;
}

async function sniffUnknownPreviewKind(realPath: string): Promise<WorkspaceFilePreviewKind> {
  const handle = await fs.open(realPath, "r");
  try {
    const buffer = Buffer.alloc(TEXT_SNIFF_BYTES);
    const { bytesRead } = await handle.read(buffer, 0, TEXT_SNIFF_BYTES, 0);
    return looksLikeText(buffer.subarray(0, bytesRead)) ? "text" : "unsupported";
  } finally {
    await handle.close();
  }
}

function remoteResource(candidate: WorkspaceCandidate, relativePath: string): ResolvedWorkspaceResource {
  return {
    kind: "remote_resource",
    provider: candidate.provider || "remote_managed",
    title: path.posix.basename(relativePath),
    displayPath: candidate.projectName ? `${candidate.projectName} / ${relativePath}` : relativePath,
    workspaceLabel: candidate.label,
    workspaceKind: candidate.workspaceKind,
    workspaceId: candidate.workspaceId,
    projectId: candidate.projectId ?? null,
    projectName: candidate.projectName ?? null,
    contentType: null,
    byteSize: null,
    previewKind: "unsupported",
    denialReason: "remote_workspace",
    capabilities: {
      preview: false,
      download: false,
      listChildren: false,
    },
  };
}

function candidateFromExecutionWorkspace(row: ExecutionWorkspaceRow): WorkspaceCandidate {
  const provider = row.providerType || row.strategyType || "local_fs";
  const rootPath = row.cwd || row.providerRef || null;
  const remote = !["local_fs", "git_worktree"].includes(provider) || !rootPath || row.status !== "active" || row.closedAt != null;
  return {
    workspaceKind: "execution_workspace",
    workspaceId: row.id,
    provider,
    label: row.name,
    rootPath,
    remote,
  };
}

function candidateFromProjectWorkspace(
  row: ProjectWorkspaceRow,
  project?: { id: string; name: string } | null,
): WorkspaceCandidate {
  const provider = row.sourceType === "local_path" ? "local_fs" : row.sourceType;
  const rootPath = row.cwd ?? null;
  const remote = !LOCAL_PROJECT_WORKSPACE_SOURCE_TYPES.has(row.sourceType) || !rootPath;
  return {
    workspaceKind: "project_workspace",
    workspaceId: row.id,
    projectId: project?.id ?? row.projectId,
    projectName: project?.name ?? null,
    provider,
    label: row.name,
    rootPath,
    remote,
  };
}

function isHttpStatus(error: unknown, status: number) {
  return (
    error instanceof Error &&
    "status" in error &&
    (error as { status?: number }).status === status
  );
}

function directoryResource(input: {
  candidate: WorkspaceCandidate;
  relativePath: string;
}): ResolvedWorkspaceResource {
  return {
    kind: "directory",
    provider: input.candidate.provider,
    title: path.posix.basename(input.relativePath),
    displayPath: input.candidate.projectName
      ? `${input.candidate.projectName} / ${input.relativePath}/`
      : `${input.relativePath}/`,
    workspaceLabel: input.candidate.label,
    workspaceKind: input.candidate.workspaceKind,
    workspaceId: input.candidate.workspaceId,
    projectId: input.candidate.projectId ?? null,
    projectName: input.candidate.projectName ?? null,
    contentType: null,
    byteSize: null,
    previewKind: "unsupported",
    denialReason: null,
    capabilities: {
      preview: false,
      download: false,
      listChildren: true,
    },
  };
}

async function statLocalCandidate(candidate: WorkspaceCandidate, normalized: NormalizedPath): Promise<LocalResolvedFile> {
  if (!candidate.rootPath) {
    throw unprocessable("Workspace is not locally readable", { code: "remote_workspace" });
  }
  throwIfDenied(normalized.segments);

  let rootReal: string;
  try {
    rootReal = await fs.realpath(candidate.rootPath);
  } catch {
    throw unprocessable("Workspace is not available on this host", { code: "workspace_unavailable" });
  }

  const targetLexical = path.resolve(rootReal, ...normalized.segments);
  let targetReal: string;
  try {
    targetReal = await fs.realpath(targetLexical);
  } catch {
    throw notFound("Workspace file not found");
  }

  const realRelative = path.relative(rootReal, targetReal);
  if (realRelative === "" || realRelative.startsWith("..") || path.isAbsolute(realRelative)) {
    throw new HttpError(403, "Workspace file path is outside the workspace", { code: "outside_workspace" });
  }
  throwIfDenied(relativePathFromReal(rootReal, targetReal).split("/").filter(Boolean));

  const stat = await fs.stat(targetReal);
  if (!stat.isFile()) {
    throw unprocessable("Workspace file is not a regular file", { code: "not_regular_file" });
  }

  const contentType = contentTypeForPath(normalized.relativePath);
  let previewKind = previewKindForKnownContentType(contentType);
  if (!previewKind) {
    previewKind = await sniffUnknownPreviewKind(targetReal);
  }

  const cap = previewCapForKind(previewKind);
  const tooLarge = stat.size > cap;
  const unsupported = previewKind === "unsupported";
  const denialReason = tooLarge ? "too_large" : unsupported ? "unsupported_content" : null;

  return {
    realPath: targetReal,
    resource: {
      kind: "file",
      provider: candidate.provider,
      title: path.posix.basename(normalized.relativePath),
      displayPath: candidate.projectName ? `${candidate.projectName} / ${normalized.relativePath}` : normalized.relativePath,
      workspaceLabel: candidate.label,
      workspaceKind: candidate.workspaceKind,
      workspaceId: candidate.workspaceId,
      projectId: candidate.projectId ?? null,
      projectName: candidate.projectName ?? null,
      contentType: contentType ?? (previewKind === "text" ? "text/plain; charset=utf-8" : "application/octet-stream"),
      byteSize: stat.size,
      previewKind,
      denialReason,
      capabilities: {
        preview: !tooLarge && !unsupported,
        download: false,
        listChildren: false,
      },
    },
  };
}

async function statLocalDirectory(candidate: WorkspaceCandidate, normalized: NormalizedPath): Promise<LocalResolvedDirectory> {
  if (!candidate.rootPath) {
    throw unprocessable("Workspace is not locally readable", { code: "remote_workspace" });
  }
  throwIfDenied(normalized.segments);

  let rootReal: string;
  try {
    rootReal = await fs.realpath(candidate.rootPath);
  } catch {
    throw unprocessable("Workspace is not available on this host", { code: "workspace_unavailable" });
  }

  const targetLexical = path.resolve(rootReal, ...normalized.segments);
  let targetReal: string;
  try {
    targetReal = await fs.realpath(targetLexical);
  } catch {
    throw notFound("Workspace folder not found");
  }

  if (!isInsideRoot(rootReal, targetReal)) {
    throw new HttpError(403, "Workspace folder path is outside the workspace", { code: "outside_workspace" });
  }
  throwIfDenied(relativePathFromReal(rootReal, targetReal).split("/").filter(Boolean));

  const stat = await fs.stat(targetReal);
  if (!stat.isDirectory()) {
    throw unprocessable("Workspace path is not a directory", { code: "not_directory" });
  }

  return {
    realPath: targetReal,
    rootReal,
    resource: directoryResource({ candidate, relativePath: normalized.relativePath }),
  };
}

async function readStableFile(realPath: string, maxBytes: number) {
  const handle = await fs.open(realPath, "r");
  try {
    const before = await handle.stat();
    if (!before.isFile()) throw unprocessable("Workspace file is not a regular file", { code: "not_regular_file" });
    if (before.size > maxBytes) throw unprocessable("Workspace file is too large to preview", { code: "too_large" });
    const data = await handle.readFile();
    const after = await handle.stat();
    if (before.dev !== after.dev || before.ino !== after.ino || before.size !== after.size || after.mtimeMs !== before.mtimeMs) {
      throw unprocessable("Workspace file changed while being read", { code: "file_changed" });
    }
    return data;
  } finally {
    await handle.close();
  }
}

function unavailableFileList(input: {
  selector: WorkspaceFileSelector;
  mode: WorkspaceFileListMode;
  path?: string | null;
  q: string | null;
  limit: number;
  offset: number;
  candidate?: WorkspaceCandidate | null;
  reason: string;
}): WorkspaceFileListResponse {
  return {
    kind: "workspace_file_list",
    state: "unavailable",
    unavailableReason: input.reason,
    workspace: input.candidate
      ? {
          provider: input.candidate.provider,
          workspaceLabel: input.candidate.label,
          workspaceKind: input.candidate.workspaceKind,
          workspaceId: input.candidate.workspaceId,
          projectId: input.candidate.projectId ?? null,
          projectName: input.candidate.projectName ?? null,
        }
      : null,
    query: {
      workspace: input.selector,
      mode: input.mode,
      path: input.path ?? null,
      q: input.q,
      limit: input.limit,
      offset: input.offset,
    },
    items: [],
    scannedCount: 0,
    truncated: false,
  };
}

function availableFileList(input: {
  selector: WorkspaceFileSelector;
  mode: WorkspaceFileListMode;
  path?: string | null;
  q: string | null;
  limit: number;
  offset: number;
  candidate: WorkspaceCandidate;
  items: WorkspaceFileListItem[];
  scannedCount: number;
  truncated: boolean;
}): WorkspaceFileListResponse {
  return {
    kind: "workspace_file_list",
    state: "available",
    workspace: {
      provider: input.candidate.provider,
      workspaceLabel: input.candidate.label,
      workspaceKind: input.candidate.workspaceKind,
      workspaceId: input.candidate.workspaceId,
      projectId: input.candidate.projectId ?? null,
      projectName: input.candidate.projectName ?? null,
    },
    query: {
      workspace: input.selector,
      mode: input.mode,
      path: input.path ?? null,
      q: input.q,
      limit: input.limit,
      offset: input.offset,
    },
    items: input.items,
    scannedCount: input.scannedCount,
    truncated: input.truncated,
  };
}

function matchesSearch(relativePath: string, normalizedQuery: string | null) {
  return !normalizedQuery || relativePath.toLowerCase().includes(normalizedQuery);
}

async function listLocalFileCandidate(input: {
  candidate: WorkspaceCandidate;
  rootReal: string;
  relativePath: string;
  normalizedQuery: string | null;
}): Promise<WorkspaceFileListItem | null> {
  let normalized: NormalizedPath;
  try {
    normalized = normalizeWorkspaceRelativePath(input.relativePath);
  } catch {
    return null;
  }
  if (shouldPruneSegments(normalized.segments)) return null;
  if (!matchesSearch(normalized.relativePath, input.normalizedQuery)) return null;

  const targetLexical = path.resolve(input.rootReal, ...normalized.segments);
  let targetReal: string;
  let stat;
  try {
    stat = await fs.lstat(targetLexical);
    if (stat.isSymbolicLink() || !stat.isFile()) return null;
    targetReal = await fs.realpath(targetLexical);
    if (!isInsideRoot(input.rootReal, targetReal)) return null;
    const realRelative = relativePathFromReal(input.rootReal, targetReal);
    if (shouldPruneSegments(realRelative.split("/").filter(Boolean))) return null;
  } catch {
    return null;
  }
  return listItemFromStat({ candidate: input.candidate, relativePath: normalized.relativePath, stat });
}

async function listLocalDirectoryChildCandidate(input: {
  candidate: WorkspaceCandidate;
  rootReal: string;
  parentReal: string;
  relativePath: string;
  entry: import("node:fs").Dirent;
  normalizedQuery: string | null;
}): Promise<WorkspaceFileListItem | null> {
  let normalized: NormalizedPath;
  try {
    normalized = normalizeWorkspaceRelativePath(input.relativePath);
  } catch {
    return null;
  }
  if (shouldPruneSegments(normalized.segments)) return null;
  if (!matchesSearch(normalized.relativePath, input.normalizedQuery)) return null;
  if (input.entry.isSymbolicLink()) return null;

  if (input.entry.isDirectory()) {
    const targetLexical = path.join(input.parentReal, input.entry.name);
    try {
      const stat = await fs.lstat(targetLexical);
      const targetReal = await fs.realpath(targetLexical);
      if (!isInsideRoot(input.rootReal, targetReal)) return null;
      const realRelative = relativePathFromReal(input.rootReal, targetReal);
      if (shouldPruneSegments(realRelative.split("/").filter(Boolean))) return null;
      return listItemFromDirectory({ candidate: input.candidate, relativePath: normalized.relativePath, stat });
    } catch {
      return null;
    }
  }

  if (!input.entry.isFile()) return null;
  return listLocalFileCandidate({
    candidate: input.candidate,
    rootReal: input.rootReal,
    relativePath: input.relativePath,
    normalizedQuery: input.normalizedQuery,
  });
}

async function enumerateWorkspaceDirectoryChildren(input: {
  candidate: WorkspaceCandidate;
  rootReal: string;
  startReal?: string;
  startRelativePath?: string;
  normalizedQuery: string | null;
  limit: number;
  offset: number;
}) {
  let entries;
  try {
    entries = await fs.readdir(input.startReal ?? input.rootReal, { withFileTypes: true });
  } catch {
    return { items: [], scannedCount: 0, truncated: false };
  }

  entries.sort((a, b) => {
    if (a.isDirectory() !== b.isDirectory()) return a.isDirectory() ? -1 : 1;
    return a.name.localeCompare(b.name);
  });

  const items: WorkspaceFileListItem[] = [];
  let scannedCount = 0;
  let matchedCount = 0;
  let truncated = false;
  for (const entry of entries) {
    scannedCount += 1;
    if (scannedCount > WORKSPACE_FILE_LIST_MAX_SCANNED_ENTRIES) {
      truncated = true;
      break;
    }
    if (entry.name.includes("\0") || entry.name.includes("/") || entry.name.includes("\\")) continue;

    const relativePath = input.startRelativePath ? `${input.startRelativePath}/${entry.name}` : entry.name;
    const item = await listLocalDirectoryChildCandidate({
      candidate: input.candidate,
      rootReal: input.rootReal,
      parentReal: input.startReal ?? input.rootReal,
      relativePath,
      entry,
      normalizedQuery: input.normalizedQuery,
    });
    if (!item) continue;

    if (matchedCount < input.offset) {
      matchedCount += 1;
      continue;
    }
    if (items.length >= input.limit) {
      truncated = true;
      break;
    }
    matchedCount += 1;
    items.push(item);
  }

  return { items, scannedCount, truncated };
}

async function enumerateWorkspaceFiles(input: {
  candidate: WorkspaceCandidate;
  rootReal: string;
  startReal?: string;
  startRelativePath?: string;
  mode: WorkspaceFileListMode;
  normalizedQuery: string | null;
  limit: number;
  offset: number;
}) {
  const dirs: Array<{ realPath: string; relativePath: string; depth: number }> = [
    { realPath: input.startReal ?? input.rootReal, relativePath: input.startRelativePath ?? "", depth: 0 },
  ];
  const items: WorkspaceFileListItem[] = [];
  let scannedCount = 0;
  let matchedCount = 0;
  let truncated = false;
  let hitScanCap = false;

  while (dirs.length > 0) {
    const dir = dirs.shift()!;
    let entries;
    try {
      entries = await fs.readdir(dir.realPath, { withFileTypes: true });
    } catch {
      continue;
    }
    entries.sort((a, b) => a.name.localeCompare(b.name));

    for (const entry of entries) {
      scannedCount += 1;
      if (scannedCount > WORKSPACE_FILE_LIST_MAX_SCANNED_ENTRIES) {
        truncated = true;
        hitScanCap = true;
        break;
      }
      if (entry.name.includes("\0") || entry.name.includes("/") || entry.name.includes("\\")) continue;

      const relativePath = dir.relativePath ? `${dir.relativePath}/${entry.name}` : entry.name;
      const segments = relativePath.split("/").filter(Boolean);
      if (shouldPruneSegments(segments)) continue;
      if (entry.isSymbolicLink()) continue;

      if (entry.isDirectory()) {
        if (dir.depth >= MAX_LIST_DEPTH) {
          truncated = true;
          continue;
        }
        dirs.push({
          realPath: path.join(dir.realPath, entry.name),
          relativePath,
          depth: dir.depth + 1,
        });
        continue;
      }
      if (!entry.isFile()) continue;

      const item = await listLocalFileCandidate({
        candidate: input.candidate,
        rootReal: input.rootReal,
        relativePath,
        normalizedQuery: input.normalizedQuery,
      });
      if (!item) continue;

      if (input.mode === "recent") {
        items.push(item);
        continue;
      }

      if (matchedCount < input.offset) {
        matchedCount += 1;
        continue;
      }
      if (items.length >= input.limit) {
        truncated = true;
        break;
      }
      matchedCount += 1;
      items.push(item);
    }
    if (hitScanCap || (truncated && input.mode !== "recent")) break;
  }

  if (input.mode === "recent") {
    items.sort((a, b) => (b.modifiedAt ?? "").localeCompare(a.modifiedAt ?? "") || a.displayPath.localeCompare(b.displayPath));
    const end = input.offset + input.limit;
    truncated = truncated || items.length > end;
    return { items: items.slice(input.offset, end), scannedCount, truncated };
  }

  return { items, scannedCount, truncated };
}

function parseGitStatusPaths(stdout: string) {
  const tokens = stdout.split("\0").filter(Boolean);
  const paths: string[] = [];
  let hitScanCap = false;
  for (let i = 0; i < tokens.length; i += 1) {
    const token = tokens[i]!;
    if (token.length < 4) continue;
    const status = token.slice(0, 2);
    const filePath = token.slice(3);
    if (filePath) paths.push(filePath);
    if (status.includes("R") || status.includes("C")) i += 1;
    if (paths.length >= WORKSPACE_FILE_LIST_MAX_SCANNED_ENTRIES) {
      hitScanCap = true;
      break;
    }
  }
  return { paths, hitScanCap };
}

async function listChangedWorkspaceFiles(input: {
  candidate: WorkspaceCandidate;
  rootReal: string;
  normalizedQuery: string | null;
  limit: number;
  offset: number;
}) {
  let stdout: string;
  try {
    const result = await execFileAsync(
      "git",
      ["-C", input.rootReal, "status", "--porcelain=v1", "-z", "--untracked-files=all"],
      { maxBuffer: GIT_STATUS_MAX_BUFFER_BYTES },
    );
    stdout = result.stdout;
  } catch {
    return { unavailableReason: "changed_unavailable" as const };
  }

  const { paths, hitScanCap } = parseGitStatusPaths(stdout);
  const matchedItems: WorkspaceFileListItem[] = [];
  let scannedCount = 0;
  for (const filePath of paths) {
    scannedCount += 1;
    const item = await listLocalFileCandidate({
      candidate: input.candidate,
      rootReal: input.rootReal,
      relativePath: filePath,
      normalizedQuery: input.normalizedQuery,
    });
    if (item) matchedItems.push(item);
  }
  matchedItems.sort((a, b) => a.displayPath.localeCompare(b.displayPath));
  const end = input.offset + input.limit;
  return {
    items: matchedItems.slice(input.offset, end),
    scannedCount,
    truncated: hitScanCap || matchedItems.length > end,
  };
}

export function workspaceFileResourceService(db: Db) {
  async function getIssue(issueId: string): Promise<IssueRow> {
    const [issue] = await db.select().from(issues).where(eq(issues.id, issueId)).limit(1);
    if (!issue) throw notFound("Issue not found");
    return issue;
  }

  async function targetProjectWorkspaceCandidate(
    issue: IssueRow,
    target: WorkspaceTargetInput,
  ): Promise<WorkspaceCandidate | null> {
    const projectId = target.projectId ?? null;
    const workspaceId = target.workspaceId ?? null;
    if (!projectId && !workspaceId) return null;
    if (!projectId || !workspaceId) {
      throw unprocessable("Workspace file target requires both projectId and workspaceId", { code: "invalid_target" });
    }

    const [project] = await db.select().from(projects).where(eq(projects.id, projectId)).limit(1);
    const [workspace] = await db.select().from(projectWorkspaces).where(eq(projectWorkspaces.id, workspaceId)).limit(1);
    if (!project || !workspace) throw notFound("Project workspace not found");
    if (project.companyId !== issue.companyId || workspace.companyId !== issue.companyId) {
      throw new HttpError(403, "Project workspace belongs to another company", { code: "cross_company_workspace" });
    }
    if (workspace.projectId !== project.id) {
      throw unprocessable("Workspace does not belong to the selected project", { code: "workspace_project_mismatch" });
    }

    return candidateFromProjectWorkspace(workspace, { id: project.id, name: project.name });
  }

  async function listCandidates(
    issue: IssueRow,
    selector: WorkspaceFileSelector,
    target: WorkspaceTargetInput = {},
  ): Promise<WorkspaceCandidate[]> {
    const explicitTarget = await targetProjectWorkspaceCandidate(issue, target);
    if (explicitTarget) return [explicitTarget];

    const candidates: WorkspaceCandidate[] = [];
    if ((selector === "auto" || selector === "execution") && issue.projectId) {
      const executionIds = [issue.executionWorkspaceId].filter((id): id is string => Boolean(id));
      let executionRows: ExecutionWorkspaceRow[] = [];
      if (executionIds.length > 0) {
        executionRows = await db.select().from(executionWorkspaces).where(
          and(
            eq(executionWorkspaces.companyId, issue.companyId),
            inArray(executionWorkspaces.id, executionIds),
          ),
        );
      }
      const sourceIssueIds = [issue.id, issue.parentId].filter((id): id is string => Boolean(id));
      if (sourceIssueIds.length > 0) {
        const activeRows = await db.select().from(executionWorkspaces).where(
          and(
            eq(executionWorkspaces.companyId, issue.companyId),
            eq(executionWorkspaces.projectId, issue.projectId),
            inArray(executionWorkspaces.sourceIssueId, sourceIssueIds),
            eq(executionWorkspaces.status, "active"),
            isNull(executionWorkspaces.closedAt),
          ),
        ).orderBy(desc(executionWorkspaces.lastUsedAt)).limit(2);
        executionRows = [...executionRows, ...activeRows];
      }
      const seen = new Set<string>();
      for (const row of executionRows) {
        if (seen.has(row.id)) continue;
        seen.add(row.id);
        candidates.push(candidateFromExecutionWorkspace(row));
      }
    }

    if ((selector === "auto" || selector === "project") && issue.projectId) {
      if (issue.projectWorkspaceId) {
        const rows = await db.select().from(projectWorkspaces).where(
          and(
            eq(projectWorkspaces.companyId, issue.companyId),
            eq(projectWorkspaces.projectId, issue.projectId),
            eq(projectWorkspaces.id, issue.projectWorkspaceId),
          ),
        ).limit(1);
        if (rows[0]) candidates.push(candidateFromProjectWorkspace(rows[0]));
      }
      const primaryRows = await db.select().from(projectWorkspaces).where(
        and(
          eq(projectWorkspaces.companyId, issue.companyId),
          eq(projectWorkspaces.projectId, issue.projectId),
          eq(projectWorkspaces.isPrimary, true),
        ),
      ).limit(1);
      if (primaryRows[0] && !candidates.some((candidate) => candidate.workspaceId === primaryRows[0]!.id)) {
        candidates.push(candidateFromProjectWorkspace(primaryRows[0]));
      }
    }

    return candidates;
  }

  async function sameCompanyProjectWorkspaceCandidates(
    issue: IssueRow,
    excludedWorkspaceIds: Set<string>,
  ): Promise<WorkspaceCandidate[]> {
    const rows = await db.select({
      workspace: projectWorkspaces,
      project: {
        id: projects.id,
        name: projects.name,
      },
    })
      .from(projectWorkspaces)
      .innerJoin(projects, eq(projectWorkspaces.projectId, projects.id))
      .where(and(
        eq(projectWorkspaces.companyId, issue.companyId),
        eq(projects.companyId, issue.companyId),
      ))
      .orderBy(desc(projectWorkspaces.isPrimary), desc(projectWorkspaces.updatedAt));

    const candidates: WorkspaceCandidate[] = [];
    const seen = new Set(excludedWorkspaceIds);
    for (const row of rows) {
      if (seen.has(row.workspace.id)) continue;
      seen.add(row.workspace.id);
      candidates.push(candidateFromProjectWorkspace(row.workspace, row.project));
    }
    return candidates;
  }

  async function discoverUniqueProjectWorkspaceMatch<T>(
    issue: IssueRow,
    excludedWorkspaceIds: Set<string>,
    check: (candidate: WorkspaceCandidate) => Promise<T>,
  ): Promise<AutoDiscovered<T>> {
    const candidates = await sameCompanyProjectWorkspaceCandidates(issue, excludedWorkspaceIds);
    const matches: T[] = [];
    for (const candidate of candidates) {
      if (candidate.remote) continue;
      try {
        matches.push(await check(candidate));
      } catch (error) {
        if (isHttpStatus(error, 404)) continue;
        throw error;
      }
      if (matches.length > 1) return { state: "ambiguous", count: matches.length };
    }
    if (matches.length === 1) return { state: "one", value: matches[0]! };
    return { state: "none" };
  }

  function throwAmbiguousWorkspacePath(count: number): never {
    throw new HttpError(409, "Workspace path matched multiple project workspaces", {
      code: "ambiguous_workspace_path",
      matchCount: count,
    });
  }

  async function resolve(issueId: string, input: {
    path: string;
    workspace?: WorkspaceFileSelector | null;
    projectId?: string | null;
    workspaceId?: string | null;
  }, opts: { issue?: IssueRow } = {}): Promise<ResolvedWorkspaceResource> {
    const issue = opts.issue ?? await getIssue(issueId);
    const selector = input.workspace ?? "auto";
    const explicitTarget = Boolean(input.projectId || input.workspaceId);
    const isDirectoryRequest = input.path.trim().endsWith("/");
    const normalized = normalizeWorkspaceRelativePath(input.path);
    const candidates = await listCandidates(issue, selector, input);
    if (candidates.length === 0) {
      throw unprocessable("No workspace is available for this issue", { code: "no_workspace" });
    }

    let lastNotFound: unknown = null;
    for (const candidate of candidates) {
      if (candidate.remote) {
        if (explicitTarget || selector !== "auto") return remoteResource(candidate, normalized.relativePath);
        continue;
      }
      try {
        return isDirectoryRequest
          ? (await statLocalDirectory(candidate, normalized)).resource
          : (await statLocalCandidate(candidate, normalized)).resource;
      } catch (error) {
        if (!explicitTarget && selector === "auto" && isHttpStatus(error, 404)) {
          lastNotFound = error;
          continue;
        }
        throw error;
      }
    }

    if (lastNotFound && !explicitTarget && selector === "auto") {
      const discovered = await discoverUniqueProjectWorkspaceMatch(
        issue,
        new Set(candidates.map((candidate) => candidate.workspaceId)),
        async (candidate) => isDirectoryRequest
          ? (await statLocalDirectory(candidate, normalized)).resource
          : (await statLocalCandidate(candidate, normalized)).resource,
      );
      if (discovered.state === "one") return discovered.value;
      if (discovered.state === "ambiguous") throwAmbiguousWorkspacePath(discovered.count);
    }

    if (lastNotFound) throw lastNotFound;
    throw unprocessable("No local-readable workspace is available for this issue", { code: "no_local_workspace" });
  }

  async function list(
    issueId: string,
    input: WorkspaceFileListQueryInput = {},
    opts: { issue?: IssueRow } = {},
  ): Promise<WorkspaceFileListResponse> {
    const issue = opts.issue ?? await getIssue(issueId);
    const selector = input.workspace ?? "auto";
    const explicitTarget = Boolean(input.projectId || input.workspaceId);
    const normalizedPath = input.path?.trim() ? normalizeWorkspaceRelativePath(input.path) : null;
    const mode = normalizedPath ? "all" : input.mode ?? "all";
    const limit = Math.min(
      WORKSPACE_FILE_LIST_MAX_LIMIT,
      Math.max(1, Math.floor(input.limit ?? WORKSPACE_FILE_LIST_DEFAULT_LIMIT)),
    );
    const offset = Math.max(0, Math.floor(input.offset ?? 0));
    const q = input.q?.trim() || null;
    const normalizedQuery = q?.toLowerCase() ?? null;
    const candidates = await listCandidates(issue, selector, input);
    if (candidates.length === 0) {
      return unavailableFileList({ selector, mode, path: normalizedPath?.relativePath ?? null, q, limit, offset, reason: "no_workspace" });
    }

    let firstUnavailable: { candidate: WorkspaceCandidate; reason: string } | null = null;
    let lastNotFound: unknown = null;
    for (const candidate of candidates) {
      if (candidate.remote) {
        firstUnavailable ??= { candidate, reason: "remote_workspace" };
        if (explicitTarget || selector !== "auto") {
          return unavailableFileList({
            selector,
            mode,
            path: normalizedPath?.relativePath ?? null,
            q,
            limit,
            offset,
            candidate,
            reason: "remote_workspace",
          });
        }
        continue;
      }

      let rootReal: string;
      let startReal: string | undefined;
      let startRelativePath: string | undefined;
      try {
        rootReal = await fs.realpath(candidate.rootPath!);
        if (normalizedPath) {
          const resolvedDirectory = await statLocalDirectory(candidate, normalizedPath);
          rootReal = resolvedDirectory.rootReal;
          startReal = resolvedDirectory.realPath;
          startRelativePath = normalizedPath.relativePath;
        }
      } catch (error) {
        if (normalizedPath) {
          if (!explicitTarget && selector === "auto" && isHttpStatus(error, 404)) {
            lastNotFound = error;
            continue;
          }
          throw error;
        }
        firstUnavailable ??= { candidate, reason: "workspace_unavailable" };
        if (explicitTarget || selector !== "auto") {
          return unavailableFileList({
            selector,
            mode,
            path: null,
            q,
            limit,
            offset,
            candidate,
            reason: "workspace_unavailable",
          });
        }
        continue;
      }

      if (mode === "changed") {
        const changed = await listChangedWorkspaceFiles({ candidate, rootReal, normalizedQuery, limit, offset });
        if ("unavailableReason" in changed) {
          const reason = changed.unavailableReason ?? "changed_unavailable";
          firstUnavailable ??= { candidate, reason };
          if (explicitTarget || selector !== "auto") {
            return unavailableFileList({
              selector,
              mode,
              path: normalizedPath?.relativePath ?? null,
              q,
              limit,
              offset,
              candidate,
              reason,
            });
          }
          continue;
        }
        return availableFileList({
          selector,
          mode,
          path: normalizedPath?.relativePath ?? null,
          q,
          limit,
          offset,
          candidate,
          items: changed.items,
          scannedCount: changed.scannedCount,
          truncated: changed.truncated,
        });
      }

      const listed = mode === "all" && !normalizedQuery
        ? await enumerateWorkspaceDirectoryChildren({
          candidate,
          rootReal,
          startReal,
          startRelativePath,
          normalizedQuery,
          limit,
          offset,
        })
        : await enumerateWorkspaceFiles({
        candidate,
        rootReal,
        startReal,
        startRelativePath,
        mode,
        normalizedQuery,
        limit,
        offset,
      });
      return availableFileList({
        selector,
        mode,
        path: normalizedPath?.relativePath ?? null,
        q,
        limit,
        offset,
        candidate,
        items: listed.items,
        scannedCount: listed.scannedCount,
        truncated: listed.truncated,
      });
    }

    if (lastNotFound && normalizedPath && !explicitTarget && selector === "auto") {
      const discovered = await discoverUniqueProjectWorkspaceMatch(
        issue,
        new Set(candidates.map((candidate) => candidate.workspaceId)),
        async (candidate) => {
          const resolvedDirectory = await statLocalDirectory(candidate, normalizedPath);
          return {
            candidate,
            rootReal: resolvedDirectory.rootReal,
            startReal: resolvedDirectory.realPath,
            startRelativePath: normalizedPath.relativePath,
          };
        },
      );
      if (discovered.state === "ambiguous") throwAmbiguousWorkspacePath(discovered.count);
      if (discovered.state === "one") {
        const listed = mode === "all" && !normalizedQuery
          ? await enumerateWorkspaceDirectoryChildren({
            candidate: discovered.value.candidate,
            rootReal: discovered.value.rootReal,
            startReal: discovered.value.startReal,
            startRelativePath: discovered.value.startRelativePath,
            normalizedQuery,
            limit,
            offset,
          })
          : await enumerateWorkspaceFiles({
          candidate: discovered.value.candidate,
          rootReal: discovered.value.rootReal,
          startReal: discovered.value.startReal,
          startRelativePath: discovered.value.startRelativePath,
          mode,
          normalizedQuery,
          limit,
          offset,
        });
        return availableFileList({
          selector,
          mode,
          path: normalizedPath.relativePath,
          q,
          limit,
          offset,
          candidate: discovered.value.candidate,
          items: listed.items,
          scannedCount: listed.scannedCount,
          truncated: listed.truncated,
        });
      }
    }

    return unavailableFileList({
      selector,
      mode,
      path: normalizedPath?.relativePath ?? null,
      q,
      limit,
      offset,
      candidate: firstUnavailable?.candidate ?? null,
      reason: firstUnavailable?.reason ?? "no_local_workspace",
    });
  }

  async function readContent(issueId: string, input: {
    path: string;
    workspace?: WorkspaceFileSelector | null;
    projectId?: string | null;
    workspaceId?: string | null;
  }, opts: { issue?: IssueRow } = {}): Promise<WorkspaceFileContent> {
    const issue = opts.issue ?? await getIssue(issueId);
    const selector = input.workspace ?? "auto";
    const explicitTarget = Boolean(input.projectId || input.workspaceId);
    const normalized = normalizeWorkspaceRelativePath(input.path);
    const candidates = await listCandidates(issue, selector, input);
    if (candidates.length === 0) {
      throw unprocessable("No workspace is available for this issue", { code: "no_workspace" });
    }

    let lastNotFound: unknown = null;
    for (const candidate of candidates) {
      if (candidate.remote) {
        if (explicitTarget || selector !== "auto") {
          throw unprocessable("Remote workspaces cannot be previewed by the server", { code: "remote_workspace" });
        }
        continue;
      }
      let resolved: LocalResolvedFile;
      try {
        resolved = await statLocalCandidate(candidate, normalized);
      } catch (error) {
        if (!explicitTarget && selector === "auto" && isHttpStatus(error, 404)) {
          lastNotFound = error;
          continue;
        }
        throw error;
      }

      if (!resolved.resource.capabilities.preview) {
        throw unprocessable("Workspace file cannot be previewed", { code: resolved.resource.denialReason ?? "unsupported_content" });
      }
      const cap = previewCapForKind(resolved.resource.previewKind);
      const data = await readStableFile(resolved.realPath, cap);
      if (resolved.resource.previewKind === "text" && !looksLikeText(data.subarray(0, Math.min(data.length, TEXT_SNIFF_BYTES)))) {
        throw unprocessable("Workspace file is not a text file", { code: "binary_content" });
      }

      return {
        resource: resolved.resource,
        content: {
          encoding: resolved.resource.previewKind === "text" ? "utf8" : "base64",
          data: resolved.resource.previewKind === "text" ? data.toString("utf8") : data.toString("base64"),
        },
      };
    }

    if (lastNotFound && !explicitTarget && selector === "auto") {
      const discovered = await discoverUniqueProjectWorkspaceMatch(
        issue,
        new Set(candidates.map((candidate) => candidate.workspaceId)),
        async (candidate) => statLocalCandidate(candidate, normalized),
      );
      if (discovered.state === "ambiguous") throwAmbiguousWorkspacePath(discovered.count);
      if (discovered.state === "one") {
        const resolved = discovered.value;
        if (!resolved.resource.capabilities.preview) {
          throw unprocessable("Workspace file cannot be previewed", { code: resolved.resource.denialReason ?? "unsupported_content" });
        }
        const cap = previewCapForKind(resolved.resource.previewKind);
        const data = await readStableFile(resolved.realPath, cap);
        if (resolved.resource.previewKind === "text" && !looksLikeText(data.subarray(0, Math.min(data.length, TEXT_SNIFF_BYTES)))) {
          throw unprocessable("Workspace file is not a text file", { code: "binary_content" });
        }

        return {
          resource: resolved.resource,
          content: {
            encoding: resolved.resource.previewKind === "text" ? "utf8" : "base64",
            data: resolved.resource.previewKind === "text" ? data.toString("utf8") : data.toString("base64"),
          },
        };
      }
    }

    if (lastNotFound) throw lastNotFound;
    throw unprocessable("No local-readable workspace is available for this issue", { code: "no_local_workspace" });
  }

  return {
    getIssue,
    list,
    resolve,
    readContent,
  };
}