/**
 * 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);
}

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;
  /** The active document's filesystem path (empty if none). */
  fsPath: string;
  /** The workspace folder Cowriting is anchored to. */
  root: string;
}

/**
 * Why a selection can't be sent to Claude — or `null` if it can. Each condition
 * gets its OWN message so the user learns the real reason instead of always
 * being told to "select some text" (the reported bug: an out-of-workspace file
 * was rejected with the no-selection message even though text was selected).
 */
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 (ctx.scheme !== "file") {
    return "Cowriting: save this document to a file first — Cowriting anchors edits to a saved workspace file.";
  }
  if (!isUnderRoot(ctx.fsPath, ctx.root)) {
    return "Cowriting: this file is outside your workspace folder — open a file inside it to ask Claude to edit (Cowriting anchors edits and attribution to files in the workspace).";
  }
  return null;
}