/**
 * workspacePath — pure, vscode-free helpers for the "is this document one
 * Cowriting can anchor to?" decision (F2/F3/F4 require a SAVED file under the
 * workspace folder, because threads/attribution/proposals persist to a
 * `.threads/` sidecar beside that file).
 *
 * Split out so the membership test and the per-condition warning are
 * deterministic and unit-testable with no editor — see `test/workspacePath.test.ts`.
 */
import * as path from "node:path";

/**
 * Is `fsPath` the workspace root or a path strictly inside it?
 *
 * Uses a path-separator boundary, NOT a bare `startsWith(root)` — otherwise a
 * sibling whose name merely begins with the root's name would falsely match
 * (e.g. `.../vscode-cowriting-plugin-content/x` vs root `.../vscode-cowriting-plugin`).
 */
export function isUnderRoot(fsPath: string, root: string): boolean {
  return fsPath === root || fsPath.startsWith(root + path.sep);
}

/**
 * Documents Cowriting can author on: a saved file OR an unsaved buffer (F8 §6.2).
 * F8 widened membership from "saved file under the workspace folder" to any
 * `file:`/`untitled:` doc — the SidecarRouter then routes where its artifact is
 * stored (repo `.threads/` in-workspace, global storage otherwise). `isUnderRoot`
 * (above) is retained as that ROUTING input, no longer an authoring gate.
 */
export function isAuthorable(scheme: string): boolean {
  return scheme === "file" || scheme === "untitled";
}

export interface SelectionContext {
  /** Is there an active text editor at all? */
  hasEditor: boolean;
  /** Is the active editor's selection empty (no highlight)? */
  selectionEmpty: boolean;
  /** The active document's URI scheme (`file`, `untitled`, …). */
  scheme: string;
}

/**
 * Why a selection can't be sent to Claude — or `null` if it can. F8 widened the
 * membership: any `file:` or `untitled:` document is authorable (in-workspace
 * files persist to the repo `.threads/` sidecar, out-of-workspace/untitled to
 * global storage — the router decides). Only a non-{file,untitled} scheme (a
 * read-only `git:`/`output:` view), a missing editor, or an empty selection is
 * refused — each with its OWN message (#24's per-condition messaging).
 */
export function selectionRejection(ctx: SelectionContext): string | null {
  if (!ctx.hasEditor) {
    return "Cowriting: focus a text editor with a selection first.";
  }
  if (ctx.selectionEmpty) {
    return "Cowriting: select some text to send to Claude first.";
  }
  if (!isAuthorable(ctx.scheme)) {
    return "Cowriting: this kind of document can't be edited — Cowriting authors on a file or an untitled buffer, not a read-only view.";
  }
  return null;
}