// Browser-side comment calls. Each throws CommentError naming the action.

import { appendComment, type CommentItem } from "./comment-model";

export type CommentAction = "load" | "post";

export class CommentError extends Error {
  constructor(public readonly action: CommentAction, public readonly signedOut: boolean) {
    super(signedOut ? "sign_in" : `comment_${action}_failed`);
  }
}

export function commentErrorText(action: CommentAction): string {
  return action === "load" ? "Could not load comments." : "Could not post comment.";
}

async function parse(res: Response, action: CommentAction): Promise<Record<string, unknown>> {
  if (res.status === 401) throw new CommentError(action, true);
  if (!res.ok) throw new CommentError(action, false);
  try {
    return (await res.json()) as Record<string, unknown>;
  } catch {
    throw new CommentError(action, false);
  }
}

export async function loadComments(postId: string, fetchImpl: typeof fetch = fetch): Promise<CommentItem[]> {
  let res: Response;
  try {
    res = await fetchImpl(`/api/posts/${encodeURIComponent(postId)}/comments`, { credentials: "same-origin" });
  } catch {
    throw new CommentError("load", false);
  }
  const b = await parse(res, "load");
  return Array.isArray(b.comments) ? (b.comments as CommentItem[]) : [];
}

/** Post a comment and return the list as it should now read. Throws and returns nothing on failure. */
export async function postComment(
  postId: string,
  text: string,
  current: CommentItem[],
  fetchImpl: typeof fetch = fetch,
): Promise<CommentItem[]> {
  const content = text.trim();
  if (!content) return current;
  let res: Response;
  try {
    res = await fetchImpl(`/api/posts/${encodeURIComponent(postId)}/comments`, {
      method: "POST",
      credentials: "same-origin",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ content }),
    });
  } catch {
    throw new CommentError("post", false);
  }
  const b = await parse(res, "post");
  const made = b.comment as CommentItem | null | undefined;
  if (made && typeof made === "object") return appendComment(current, made);
  // The feed did not return the new comment; read the list back.
  try {
    return await loadComments(postId, fetchImpl);
  } catch {
    return appendComment(current, {
      key: `local#${current.length}`, id: null, authorName: "You",
      createdAt: new Date().toISOString(), removed: false, content,
    });
  }
}