/**
 * User-prompt formatting for backends.
 *
 * Every backend formats incoming user messages the same way before handing
 * them to its underlying SDK: optional `[YYYY-MM-DD HH:MM:SS]` time tag,
 * optional `[Name]` sender label for group chats, optional `[msg_id:N]`
 * reference for tool-use targeting, then the user text.
 *
 * Centralising this prevents the "Claude SDK adds the time tag, Kilo
 * doesn't" drift that motivated the shared-framework refactor.
 *
 * Examples:
 *   group:  "[2026-05-15 11:01:23] [Dylan (@dylanneve1)] [msg_id:2485]: actual text"
 *   DM:     "[2026-05-15 11:01:23] [msg_id:2485] actual text"
 *   DM (no msg_id): "[2026-05-15 11:01:23] actual text"
 */

import { formatFullDatetime } from "../../util/time.js";

// ── Public API ──────────────────────────────────────────────────────────────

/** Inputs for `formatUserPrompt`. */
export type PromptFormatInputs = {
  /** Raw user text — passed through verbatim. */
  text: string;
  /** Display name of the sender (e.g. "Dylan"). */
  senderName: string;
  /**
   * Platform handle of the sender WITHOUT the leading `@` (e.g. `dylanneve1`).
   * Rendered next to the display name in group chats so the model can address
   * or mention someone correctly — display names are not addressable, handles
   * are. Absent for users who have no handle set.
   */
  senderHandle?: string;
  /** True when the chat is a group; influences whether the `[Name]` label is included. */
  isGroup?: boolean;
  /** Provider message id (Telegram numeric, Discord snowflake string). */
  messageId?: number | string;
  /** When true, omit the leading `[YYYY-MM-DD HH:MM:SS]` tag. */
  omitTimeTag?: boolean;
};

/**
 * Format a user prompt for the AI backend.
 *
 * The shape matches what the Claude SDK backend has shipped since the
 * v1.10.x window — all later backends should consume this helper so the
 * model receives a consistent input contract regardless of which provider
 * is on the other end.
 */
export function formatUserPrompt(inputs: PromptFormatInputs): string {
  const timeTag = inputs.omitTimeTag ? "" : `[${formatFullDatetime()}]`;
  const msgIdHint =
    inputs.messageId !== undefined ? ` [msg_id:${inputs.messageId}]` : "";

  if (inputs.isGroup) {
    const handle = inputs.senderHandle?.trim().replace(/^@+/, "");
    const who = handle
      ? `${inputs.senderName} (@${handle})`
      : inputs.senderName;
    return joinNonEmpty(timeTag, `[${who}]${msgIdHint}:`, inputs.text);
  }

  // DM: no [Name] label needed (Telegram already shows sender)
  if (msgIdHint) {
    return joinNonEmpty(`${timeTag}${msgIdHint}`.trim(), inputs.text);
  }
  return joinNonEmpty(timeTag, inputs.text);
}

// ── Helpers ─────────────────────────────────────────────────────────────────

function joinNonEmpty(...parts: string[]): string {
  return parts
    .map((p) => p.trim())
    .filter((p) => p.length > 0)
    .join(" ");
}