import { struct, u8 } from '@solana/buffer-layout';
import type { AccountMeta, PublicKey } from '@solana/web3.js';
import { TransactionInstruction } from '@solana/web3.js';
import { TOKEN_PROGRAM_ID } from '../constants.js';
import {
    TokenInvalidInstructionDataError,
    TokenInvalidInstructionKeysError,
    TokenInvalidInstructionProgramError,
    TokenInvalidInstructionTypeError,
} from '../errors.js';
import { TokenInstruction } from './types.js';

/** TODO: docs */
export interface SyncNativeInstructionData {
    instruction: TokenInstruction.SyncNative;
}

/** TODO: docs */
export const syncNativeInstructionData = struct<SyncNativeInstructionData>([u8('instruction')]);

/**
 * Construct a SyncNative instruction
 *
 * @param account   Native account to sync lamports from
 * @param programId SPL Token program account
 *
 * @return Instruction to add to a transaction
 */
export function createSyncNativeInstruction(account: PublicKey, programId = TOKEN_PROGRAM_ID): TransactionInstruction {
    const keys = [{ pubkey: account, isSigner: false, isWritable: true }];

    const data = Buffer.alloc(syncNativeInstructionData.span);
    syncNativeInstructionData.encode({ instruction: TokenInstruction.SyncNative }, data);

    return new TransactionInstruction({ keys, programId, data });
}

/** A decoded, valid SyncNative instruction */
export interface DecodedSyncNativeInstruction {
    programId: PublicKey;
    keys: {
        account: AccountMeta;
    };
    data: {
        instruction: TokenInstruction.SyncNative;
    };
}

/**
 * Decode a SyncNative instruction and validate it
 *
 * @param instruction Transaction instruction to decode
 * @param programId   SPL Token program account
 *
 * @return Decoded, valid instruction
 */
export function decodeSyncNativeInstruction(
    instruction: TransactionInstruction,
    programId = TOKEN_PROGRAM_ID,
): DecodedSyncNativeInstruction {
    if (!instruction.programId.equals(programId)) throw new TokenInvalidInstructionProgramError();
    if (instruction.data.length !== syncNativeInstructionData.span) throw new TokenInvalidInstructionDataError();

    const {
        keys: { account },
        data,
    } = decodeSyncNativeInstructionUnchecked(instruction);
    if (data.instruction !== TokenInstruction.SyncNative) throw new TokenInvalidInstructionTypeError();
    if (!account) throw new TokenInvalidInstructionKeysError();

    // TODO: key checks?

    return {
        programId,
        keys: {
            account,
        },
        data,
    };
}

/** A decoded, non-validated SyncNative instruction */
export interface DecodedSyncNativeInstructionUnchecked {
    programId: PublicKey;
    keys: {
        account: AccountMeta | undefined;
    };
    data: {
        instruction: number;
    };
}

/**
 * Decode a SyncNative instruction without validating it
 *
 * @param instruction Transaction instruction to decode
 *
 * @return Decoded, non-validated instruction
 */
export function decodeSyncNativeInstructionUnchecked({
    programId,
    keys: [account],
    data,
}: TransactionInstruction): DecodedSyncNativeInstructionUnchecked {
    return {
        programId,
        keys: {
            account,
        },
        data: syncNativeInstructionData.decode(data),
    };
}
