import { PublicKey, SystemProgram, TransactionInstruction } from "@solana/web3.js";
import type { PitProgram } from "../program.js";
import { getUserProfileAddress } from "../accounts/userProfile.js";

/**
 * Parameters for creating a set_nickname instruction
 */
export interface SetNicknameParams {
  /** User's wallet public key (signer) */
  user: PublicKey;
  /** Custom nickname (max 32 UTF-8 **bytes**, empty string to reset) */
  nickname: string;
}

/**
 * Create a set_nickname instruction
 *
 * This instruction allows users to set a custom on-chain nickname.
 * If the user profile doesn't exist, it will be created automatically.
 *
 * **IMPORTANT**: Nickname is validated by **byte length** (max 32 bytes),
 * not character count. Multi-byte UTF-8 characters (emoji, CJK) consume
 * 2-4 bytes each.
 *
 * @param program - Anchor Program instance
 * @param params - Nickname parameters
 * @returns Promise resolving to TransactionInstruction
 *
 * @example
 * ```typescript
 * import { createProgram, createSetNicknameInstruction } from "@pit-protocol/sdk";
 *
 * const program = createProgram(provider);
 * const ix = await createSetNicknameInstruction(program, {
 *   user: wallet.publicKey,
 *   nickname: "Diamond Ape",
 * });
 *
 * const tx = new Transaction().add(ix);
 * await sendAndConfirmTransaction(connection, tx, [wallet]);
 * ```
 */
export async function createSetNicknameInstruction(
  program: PitProgram,
  params: SetNicknameParams
): Promise<TransactionInstruction> {
  const { user, nickname } = params;

  // Validate nickname byte length (client-side validation)
  const byteLength = Buffer.byteLength(nickname, "utf8");
  if (byteLength > 32) {
    throw new Error(
      `Nickname too long: ${byteLength} bytes (max 32 bytes). ` +
        `Multi-byte characters (emoji, CJK) use 2-4 bytes each.`
    );
  }

  const userProfile = getUserProfileAddress(user);

  return await program.methods
    .setNickname(nickname)
    .accountsPartial({
      userProfile,
      user,
      systemProgram: SystemProgram.programId,
    })
    .instruction();
}