near_kit/client/

rpc.rs

//! Low-level JSON-RPC client for NEAR.

use std::sync::atomic::{AtomicU64, Ordering};
use std::time::Duration;

use base64::{Engine as _, engine::general_purpose::STANDARD};
use serde::{Deserialize, Serialize, de::DeserializeOwned};

use crate::error::RpcError;
use crate::types::rpc::RawTransactionResponse;
use crate::types::{
    AccessKeyListView, AccessKeyView, AccountId, AccountView, BlockReference, BlockView,
    CryptoHash, EpochValidatorInfo, GasPrice, PublicKey, SignedTransaction, StatusResponse,
    TxExecutionStatus, ViewFunctionResult,
};

/// Network configuration presets.
pub struct NetworkConfig {
    /// The RPC URL for this network.
    pub rpc_url: &'static str,
    /// The network identifier (e.g., "mainnet", "testnet").
    /// Reserved for future use in transaction signing.
    #[allow(dead_code)]
    pub network_id: &'static str,
}

/// Mainnet configuration.
pub const MAINNET: NetworkConfig = NetworkConfig {
    rpc_url: "https://free.rpc.fastnear.com",
    network_id: "mainnet",
};

/// Testnet configuration.
pub const TESTNET: NetworkConfig = NetworkConfig {
    rpc_url: "https://test.rpc.fastnear.com",
    network_id: "testnet",
};

/// Retry configuration for RPC calls.
#[derive(Clone, Debug)]
pub struct RetryConfig {
    /// Maximum number of retries.
    pub max_retries: u32,
    /// Initial delay in milliseconds.
    pub initial_delay_ms: u64,
    /// Maximum delay in milliseconds.
    pub max_delay_ms: u64,
}

impl Default for RetryConfig {
    fn default() -> Self {
        Self {
            max_retries: 3,
            initial_delay_ms: 500,
            max_delay_ms: 5000,
        }
    }
}

/// JSON-RPC request structure.
#[derive(Serialize)]
struct JsonRpcRequest<'a, P: Serialize> {
    jsonrpc: &'static str,
    id: u64,
    method: &'a str,
    params: P,
}

/// JSON-RPC response structure.
///
/// The `result` field is deserialized as raw JSON first, then parsed into `T`
/// only after confirming no error is present. This avoids deserialization
/// failures when the RPC returns an error with a partial/unexpected `result`.
#[derive(Deserialize)]
struct JsonRpcResponse {
    #[allow(dead_code)]
    jsonrpc: String,
    #[allow(dead_code)]
    id: u64,
    result: Option<serde_json::Value>,
    error: Option<JsonRpcError>,
}

/// JSON-RPC error structure.
/// NEAR RPC returns structured errors with name/cause/info pattern.
#[derive(Debug, Deserialize)]
struct JsonRpcError {
    code: i64,
    message: String,
    #[serde(default)]
    data: Option<serde_json::Value>,
    #[serde(default)]
    cause: Option<ErrorCause>,
    #[serde(default)]
    #[allow(dead_code)]
    name: Option<String>,
}

/// Structured error cause from NEAR RPC.
#[derive(Debug, Deserialize)]
struct ErrorCause {
    name: String,
    #[serde(default)]
    info: Option<serde_json::Value>,
}

/// Response from EXPERIMENTAL_call_function.
/// Errors are returned through the JSON-RPC error envelope, so no `error`
/// field is needed here.
#[derive(Debug, Deserialize)]
struct CallFunctionResponse {
    result: Vec<u8>,
    #[serde(default)]
    logs: Vec<String>,
    block_height: u64,
    block_hash: CryptoHash,
}

/// Low-level JSON-RPC client for NEAR.
pub struct RpcClient {
    url: String,
    client: reqwest::Client,
    retry_config: RetryConfig,
    request_id: AtomicU64,
}

impl RpcClient {
    /// Create a new RPC client with the given URL.
    pub fn new(url: impl Into<String>) -> Self {
        Self {
            url: url.into(),
            client: reqwest::Client::new(),
            retry_config: RetryConfig::default(),
            request_id: AtomicU64::new(0),
        }
    }

    /// Create a new RPC client with custom retry configuration.
    pub fn with_retry_config(url: impl Into<String>, retry_config: RetryConfig) -> Self {
        Self {
            url: url.into(),
            client: reqwest::Client::new(),
            retry_config,
            request_id: AtomicU64::new(0),
        }
    }

    /// Get the RPC URL.
    pub fn url(&self) -> &str {
        &self.url
    }

    /// Make a raw RPC call with retries.
    #[tracing::instrument(skip(self, params), fields(rpc.method = method, rpc.url = %sanitize_url(&self.url)))]
    pub async fn call<P: Serialize, R: DeserializeOwned>(
        &self,
        method: &str,
        params: P,
    ) -> Result<R, RpcError> {
        let total_attempts = self.retry_config.max_retries + 1;

        for attempt in 0..total_attempts {
            let request_id = self.request_id.fetch_add(1, Ordering::Relaxed);

            let request = JsonRpcRequest {
                jsonrpc: "2.0",
                id: request_id,
                method,
                params: &params,
            };

            match self.try_call::<R>(&request).await {
                Ok(result) => return Ok(result),
                Err(e) if e.is_retryable() && attempt < total_attempts - 1 => {
                    let delay = std::cmp::min(
                        self.retry_config.initial_delay_ms * 2u64.pow(attempt),
                        self.retry_config.max_delay_ms,
                    );
                    tracing::warn!(
                        attempt = attempt + 1,
                        max_attempts = total_attempts,
                        delay_ms = delay,
                        error = %e,
                        "RPC request failed, retrying"
                    );
                    tokio::time::sleep(Duration::from_millis(delay)).await;
                    continue;
                }
                Err(e) => {
                    tracing::error!(error = %e, "RPC request failed");
                    return Err(e);
                }
            }
        }

        unreachable!("all loop iterations return")
    }

    /// Single attempt to make an RPC call.
    async fn try_call<R: DeserializeOwned>(
        &self,
        request: &JsonRpcRequest<'_, impl Serialize>,
    ) -> Result<R, RpcError> {
        if tracing::enabled!(tracing::Level::TRACE) {
            if let Ok(json) = serde_json::to_string(request) {
                tracing::trace!(payload = %json, "RPC request");
            }
        }

        let response = self
            .client
            .post(&self.url)
            .header("Content-Type", "application/json")
            .json(request)
            .send()
            .await?;

        let status = response.status();
        let body = response.text().await?;

        tracing::trace!(payload = %body, "RPC response");

        if !status.is_success() {
            let retryable = is_retryable_status(status.as_u16());
            return Err(RpcError::network(
                format!("HTTP {}: {}", status, body),
                Some(status.as_u16()),
                retryable,
            ));
        }

        let rpc_response: JsonRpcResponse = serde_json::from_str(&body).map_err(RpcError::Json)?;

        if let Some(error) = rpc_response.error {
            return Err(self.parse_rpc_error(&error));
        }

        let result_value = rpc_response
            .result
            .ok_or_else(|| RpcError::InvalidResponse("Missing result in response".to_string()))?;

        // NEAR's `query` endpoint sometimes returns errors inside the result
        // object (with an "error" field) instead of in the JSON-RPC error
        // envelope. Only check for this on the `query` method to avoid
        // misclassifying legitimate results from other methods.
        if request.method == "query" {
            if let Some(error_str) = result_value.get("error").and_then(|e| e.as_str()) {
                let synthetic = JsonRpcError {
                    // Use -32600 (Invalid Request) rather than -32000 (Server Error)
                    // so deterministic failures don't get retried.
                    code: -32600,
                    message: error_str.to_string(),
                    data: Some(serde_json::Value::String(error_str.to_string())),
                    cause: None,
                    name: None,
                };
                return Err(self.parse_rpc_error(&synthetic));
            }
        }

        serde_json::from_value(result_value).map_err(RpcError::Json)
    }

    /// Parse an RPC error into a specific error type.
    fn parse_rpc_error(&self, error: &JsonRpcError) -> RpcError {
        // First, check the direct cause field (NEAR RPC structured errors)
        if let Some(cause) = &error.cause {
            let cause_name = cause.name.as_str();
            let info = cause.info.as_ref();
            let data = &error.data;

            match cause_name {
                "UNKNOWN_ACCOUNT" => {
                    if let Some(account_id) = info
                        .and_then(|i| i.get("requested_account_id"))
                        .and_then(|a| a.as_str())
                    {
                        if let Ok(account_id) = account_id.parse() {
                            return RpcError::AccountNotFound(account_id);
                        }
                    }
                }
                "INVALID_ACCOUNT" => {
                    let account_id = info
                        .and_then(|i| i.get("requested_account_id"))
                        .and_then(|a| a.as_str())
                        .unwrap_or("unknown");
                    return RpcError::InvalidAccount(account_id.to_string());
                }
                "UNKNOWN_ACCESS_KEY" => {
                    if let Some(public_key) = info
                        .and_then(|i| i.get("public_key"))
                        .and_then(|k| k.as_str())
                        .and_then(|k| k.parse().ok())
                    {
                        // Legacy `query` includes requested_account_id;
                        // EXPERIMENTAL_view_access_key does not (the caller
                        // already knows the account). Fall back to "unknown".
                        let account_id = info
                            .and_then(|i| i.get("requested_account_id"))
                            .and_then(|a| a.as_str())
                            .and_then(|a| a.parse().ok())
                            .unwrap_or_else(|| "unknown".parse().unwrap());
                        return RpcError::AccessKeyNotFound {
                            account_id,
                            public_key,
                        };
                    }
                }
                "UNKNOWN_BLOCK" => {
                    let block_ref = data
                        .as_ref()
                        .and_then(|d| d.as_str())
                        .unwrap_or(&error.message);
                    return RpcError::UnknownBlock(block_ref.to_string());
                }
                "UNKNOWN_CHUNK" => {
                    let chunk_ref = info
                        .and_then(|i| i.get("chunk_hash"))
                        .and_then(|c| c.as_str())
                        .unwrap_or(&error.message);
                    return RpcError::UnknownChunk(chunk_ref.to_string());
                }
                "UNKNOWN_EPOCH" => {
                    let block_ref = data
                        .as_ref()
                        .and_then(|d| d.as_str())
                        .unwrap_or(&error.message);
                    return RpcError::UnknownEpoch(block_ref.to_string());
                }
                "UNKNOWN_RECEIPT" => {
                    let receipt_id = info
                        .and_then(|i| i.get("receipt_id"))
                        .and_then(|r| r.as_str())
                        .unwrap_or("unknown");
                    return RpcError::UnknownReceipt(receipt_id.to_string());
                }
                "NO_CONTRACT_CODE" => {
                    let account_id = info
                        .and_then(|i| {
                            i.get("contract_account_id")
                                .or_else(|| i.get("account_id"))
                                .or_else(|| i.get("contract_id"))
                        })
                        .and_then(|a| a.as_str())
                        .unwrap_or("unknown");
                    if let Ok(account_id) = account_id.parse() {
                        return RpcError::ContractNotDeployed(account_id);
                    }
                }
                "TOO_LARGE_CONTRACT_STATE" => {
                    let account_id = info
                        .and_then(|i| i.get("account_id").or_else(|| i.get("contract_id")))
                        .and_then(|a| a.as_str())
                        .unwrap_or("unknown");
                    if let Ok(account_id) = account_id.parse() {
                        return RpcError::ContractStateTooLarge(account_id);
                    }
                }
                "CONTRACT_EXECUTION_ERROR" => {
                    // Check for CodeDoesNotExist inside vm_error
                    // (EXPERIMENTAL_call_function wraps this as CONTRACT_EXECUTION_ERROR)
                    if let Some(vm_error) = info.and_then(|i| i.get("vm_error")) {
                        if let Some(compilation_err) = vm_error.get("CompilationError") {
                            if let Some(code_not_exist) = compilation_err.get("CodeDoesNotExist") {
                                if let Some(account_id) = code_not_exist
                                    .get("account_id")
                                    .and_then(|a| a.as_str())
                                    .and_then(|a| a.parse().ok())
                                {
                                    return RpcError::ContractNotDeployed(account_id);
                                }
                            }
                        }
                    }

                    // Legacy `query` includes contract_id/method_name;
                    // EXPERIMENTAL_call_function does not (the caller
                    // already knows them). Fall back to "unknown".
                    let contract_id = info
                        .and_then(|i| i.get("contract_id"))
                        .and_then(|c| c.as_str())
                        .unwrap_or("unknown");
                    let method_name = info
                        .and_then(|i| i.get("method_name"))
                        .and_then(|m| m.as_str())
                        .map(String::from);
                    let message = data
                        .as_ref()
                        .and_then(|d| d.as_str())
                        .map(|s| s.to_string())
                        .or_else(|| {
                            // EXPERIMENTAL endpoint: use vm_error as fallback
                            // when data isn't a string
                            info.and_then(|i| i.get("vm_error")).map(|v| v.to_string())
                        })
                        .unwrap_or_else(|| error.message.clone());
                    if let Ok(contract_id) = contract_id.parse() {
                        return RpcError::ContractExecution {
                            contract_id,
                            method_name,
                            message,
                        };
                    }
                }
                "UNAVAILABLE_SHARD" => {
                    return RpcError::ShardUnavailable(error.message.clone());
                }
                "NO_SYNCED_BLOCKS" | "NOT_SYNCED_YET" => {
                    return RpcError::NodeNotSynced(error.message.clone());
                }
                "INVALID_SHARD_ID" => {
                    let shard_id = info
                        .and_then(|i| i.get("shard_id"))
                        .map(|s| s.to_string())
                        .unwrap_or_else(|| "unknown".to_string());
                    return RpcError::InvalidShardId(shard_id);
                }
                "INVALID_TRANSACTION" => {
                    return RpcError::invalid_transaction(&error.message, data.clone());
                }
                "TIMEOUT_ERROR" => {
                    let tx_hash = info
                        .and_then(|i| i.get("transaction_hash"))
                        .and_then(|h| h.as_str())
                        .map(String::from);
                    return RpcError::RequestTimeout {
                        message: error.message.clone(),
                        transaction_hash: tx_hash,
                    };
                }
                "PARSE_ERROR" => {
                    return RpcError::ParseError(error.message.clone());
                }
                "INTERNAL_ERROR" => {
                    return RpcError::InternalError(error.message.clone());
                }
                _ => {}
            }
        }

        // Fallback: check for string error messages in data field
        if let Some(data) = &error.data {
            if let Some(error_str) = data.as_str() {
                if error_str.contains("does not exist") {
                    // Try to extract account ID from error message
                    // Format: "account X does not exist while viewing"
                    if let Some(start) = error_str.strip_prefix("account ") {
                        if let Some(account_str) = start.split_whitespace().next() {
                            if let Ok(account_id) = account_str.parse() {
                                return RpcError::AccountNotFound(account_id);
                            }
                        }
                    }
                }
            }
        }

        RpcError::Rpc {
            code: error.code,
            message: error.message.clone(),
            data: error.data.clone(),
        }
    }

    // ========================================================================
    // High-level RPC methods
    // ========================================================================

    /// View account information.
    #[tracing::instrument(skip(self, block), fields(%account_id))]
    pub async fn view_account(
        &self,
        account_id: &AccountId,
        block: BlockReference,
    ) -> Result<AccountView, RpcError> {
        let mut params = serde_json::json!({
            "account_id": account_id.to_string(),
        });
        self.merge_block_reference(&mut params, &block);
        self.call("EXPERIMENTAL_view_account", params).await
    }

    /// View access key information.
    #[tracing::instrument(skip(self, block), fields(%account_id, %public_key))]
    pub async fn view_access_key(
        &self,
        account_id: &AccountId,
        public_key: &PublicKey,
        block: BlockReference,
    ) -> Result<AccessKeyView, RpcError> {
        let mut params = serde_json::json!({
            "account_id": account_id.to_string(),
            "public_key": public_key.to_string(),
        });
        self.merge_block_reference(&mut params, &block);
        self.call("EXPERIMENTAL_view_access_key", params)
            .await
            .map_err(|e| match e {
                // The EXPERIMENTAL endpoint's UNKNOWN_ACCESS_KEY error omits
                // the account_id from its info payload. Patch it in from the
                // request params so callers get a complete error.
                RpcError::AccessKeyNotFound { public_key, .. } => RpcError::AccessKeyNotFound {
                    account_id: account_id.clone(),
                    public_key,
                },
                other => other,
            })
    }

    /// View all access keys for an account.
    #[tracing::instrument(skip(self, block), fields(%account_id))]
    pub async fn view_access_key_list(
        &self,
        account_id: &AccountId,
        block: BlockReference,
    ) -> Result<AccessKeyListView, RpcError> {
        let mut params = serde_json::json!({
            "account_id": account_id.to_string(),
        });
        self.merge_block_reference(&mut params, &block);
        self.call("EXPERIMENTAL_view_access_key_list", params).await
    }

    /// Call a view function on a contract.
    #[tracing::instrument(skip(self, args, block), fields(contract_id = %account_id, method = method_name))]
    pub async fn view_function(
        &self,
        account_id: &AccountId,
        method_name: &str,
        args: &[u8],
        block: BlockReference,
    ) -> Result<ViewFunctionResult, RpcError> {
        let mut params = serde_json::json!({
            "account_id": account_id.to_string(),
            "method_name": method_name,
            "args_base64": STANDARD.encode(args),
        });
        self.merge_block_reference(&mut params, &block);

        // EXPERIMENTAL_call_function returns errors through the JSON-RPC
        // error envelope, so `parse_rpc_error` handles them. Patch in
        // the caller-known contract_id and method_name when they are
        // missing from the error info (the experimental endpoint omits them).
        let response: CallFunctionResponse = self
            .call("EXPERIMENTAL_call_function", params)
            .await
            .map_err(|e| match e {
                RpcError::ContractExecution { message, .. } => RpcError::ContractExecution {
                    contract_id: account_id.clone(),
                    method_name: Some(method_name.to_string()),
                    message,
                },
                other => other,
            })?;

        Ok(ViewFunctionResult {
            result: response.result,
            logs: response.logs,
            block_height: response.block_height,
            block_hash: response.block_hash,
        })
    }

    /// Get block information.
    #[tracing::instrument(skip(self, block))]
    pub async fn block(&self, block: BlockReference) -> Result<BlockView, RpcError> {
        let params = block.to_rpc_params();
        self.call("block", params).await
    }

    /// Get node status.
    #[tracing::instrument(skip(self))]
    pub async fn status(&self) -> Result<StatusResponse, RpcError> {
        self.call("status", serde_json::json!([])).await
    }

    /// Get current gas price.
    #[tracing::instrument(skip(self))]
    pub async fn gas_price(&self, block_hash: Option<&CryptoHash>) -> Result<GasPrice, RpcError> {
        let params = match block_hash {
            Some(hash) => serde_json::json!([hash.to_string()]),
            None => serde_json::json!([serde_json::Value::Null]),
        };
        self.call("gas_price", params).await
    }

    /// Get validator information for an epoch.
    ///
    /// Pass `None` for the latest epoch, or a block height/hash to query a
    /// specific epoch. Finality and sync-checkpoint variants are treated as
    /// latest (the `validators` RPC accepts only `block_id` or `null`).
    #[tracing::instrument(skip(self))]
    pub async fn validators(
        &self,
        block: Option<BlockReference>,
    ) -> Result<EpochValidatorInfo, RpcError> {
        let params = serde_json::json!([block_id_or_null(block.as_ref())]);
        self.call("validators", params).await
    }

    /// Send a signed transaction.
    #[tracing::instrument(skip(self, signed_tx), fields(
        tx_hash = tracing::field::Empty,
        sender = %signed_tx.transaction.signer_id,
        receiver = %signed_tx.transaction.receiver_id,
        ?wait_until,
    ))]
    pub async fn send_tx(
        &self,
        signed_tx: &SignedTransaction,
        wait_until: TxExecutionStatus,
    ) -> Result<RawTransactionResponse, RpcError> {
        let tx_hash = signed_tx.get_hash();
        tracing::Span::current().record("tx_hash", tracing::field::display(&tx_hash));
        let params = serde_json::json!({
            "signed_tx_base64": signed_tx.to_base64(),
            "wait_until": wait_until.as_str(),
        });
        let mut response: RawTransactionResponse = self.call("send_tx", params).await?;
        response.transaction_hash = tx_hash;
        Ok(response)
    }

    /// Get transaction status with full receipt details.
    ///
    /// Uses `EXPERIMENTAL_tx_status` which returns complete receipt information.
    /// When the transaction has been executed, the outcome's `receipts` field
    /// will be populated (unlike `send_tx` which leaves it empty).
    #[tracing::instrument(skip(self), fields(%tx_hash, sender = %sender_id, ?wait_until))]
    pub async fn tx_status(
        &self,
        tx_hash: &CryptoHash,
        sender_id: &AccountId,
        wait_until: TxExecutionStatus,
    ) -> Result<RawTransactionResponse, RpcError> {
        let params = serde_json::json!({
            "tx_hash": tx_hash.to_string(),
            "sender_account_id": sender_id.to_string(),
            "wait_until": wait_until.as_str(),
        });
        let mut response: RawTransactionResponse =
            self.call("EXPERIMENTAL_tx_status", params).await?;
        response.transaction_hash = response
            .outcome
            .as_ref()
            .map(|o| *o.transaction_hash())
            .unwrap_or(*tx_hash);
        Ok(response)
    }

    /// Merge block reference parameters into a JSON object.
    fn merge_block_reference(&self, params: &mut serde_json::Value, block: &BlockReference) {
        if let serde_json::Value::Object(block_params) = block.to_rpc_params() {
            if let serde_json::Value::Object(map) = params {
                map.extend(block_params);
            }
        }
    }

    // ========================================================================
    // Sandbox-only methods
    // ========================================================================

    /// Patch account state in sandbox.
    ///
    /// This is a sandbox-only method that allows modifying account state directly,
    /// useful for testing scenarios that require specific account configurations
    /// (e.g., setting a high balance for staking tests).
    ///
    /// # Arguments
    ///
    /// * `records` - State records to patch (Account, Data, Contract, AccessKey, etc.)
    ///
    /// # Example
    ///
    /// ```rust,ignore
    /// // Set account balance to 1M NEAR
    /// rpc.sandbox_patch_state(serde_json::json!([
    ///     {
    ///         "Account": {
    ///             "account_id": "alice.sandbox",
    ///             "account": {
    ///                 "amount": "1000000000000000000000000000000",
    ///                 "locked": "0",
    ///                 "code_hash": "11111111111111111111111111111111",
    ///                 "storage_usage": 182
    ///             }
    ///         }
    ///     }
    /// ])).await?;
    /// ```
    /// Fast-forward the sandbox by `delta_height` blocks.
    ///
    /// This is useful for testing time-dependent logic (e.g., lockups, staking
    /// epoch changes) without waiting for real block production.
    ///
    /// **Note:** This can take a while for large deltas — the sandbox node
    /// internally produces all intermediate blocks. The RPC call will block
    /// until fast-forwarding completes (up to 1 hour server-side timeout).
    ///
    /// # Example
    ///
    /// ```rust,ignore
    /// // Advance the sandbox by 1000 blocks
    /// rpc.sandbox_fast_forward(1000).await?;
    /// ```
    pub async fn sandbox_fast_forward(&self, delta_height: u64) -> Result<(), RpcError> {
        let params = serde_json::json!({
            "delta_height": delta_height,
        });

        let _: serde_json::Value = self.call("sandbox_fast_forward", params).await?;
        Ok(())
    }

    pub async fn sandbox_patch_state(&self, records: serde_json::Value) -> Result<(), RpcError> {
        let params = serde_json::json!({
            "records": records,
        });

        // The sandbox_patch_state method returns an empty result on success
        let _: serde_json::Value = self.call("sandbox_patch_state", params).await?;

        // NOTE: For some reason, patching account-related items sometimes requires
        // sending the patch twice for it to take effect reliably.
        // See: https://github.com/near/near-workspaces-rs/commit/2b72b9b8491c3140ff2d30b0c45d09b200cb027b
        let _: serde_json::Value = self
            .call(
                "sandbox_patch_state",
                serde_json::json!({
                    "records": records,
                }),
            )
            .await?;

        // Small delay to allow state to propagate - sandbox patch_state has race conditions
        tokio::time::sleep(std::time::Duration::from_millis(100)).await;

        Ok(())
    }
}

impl Clone for RpcClient {
    fn clone(&self) -> Self {
        Self {
            url: self.url.clone(),
            client: self.client.clone(),
            retry_config: self.retry_config.clone(),
            request_id: AtomicU64::new(0),
        }
    }
}

impl std::fmt::Debug for RpcClient {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("RpcClient")
            .field("url", &self.url)
            .field("retry_config", &self.retry_config)
            .finish()
    }
}

// ============================================================================
// Helper functions
// ============================================================================

/// Convert a [`BlockReference`] to a `block_id` value for RPC methods that
/// accept only positional `block_id` or `null` (e.g. `validators`,
/// `EXPERIMENTAL_validators_ordered`).
///
/// Height and hash variants are forwarded as-is; finality and sync-checkpoint
/// variants become `null` (latest).
fn block_id_or_null(block: Option<&BlockReference>) -> serde_json::Value {
    match block {
        Some(BlockReference::Height(h)) => serde_json::json!(*h),
        Some(BlockReference::Hash(h)) => serde_json::json!(h.to_string()),
        _ => serde_json::Value::Null,
    }
}

/// Strip query string, fragment, and userinfo from a URL for safe logging.
///
/// RPC provider URLs may carry API keys as query parameters or path tokens.
/// This returns `scheme://host/path` so credentials don't leak into tracing spans.
fn sanitize_url(url: &str) -> &str {
    // Strip query and fragment
    let end = url.find('?').or_else(|| url.find('#')).unwrap_or(url.len());
    &url[..end]
}

/// Check if an HTTP status code is retryable.
fn is_retryable_status(status: u16) -> bool {
    // 408 Request Timeout - retryable
    // 429 Too Many Requests - retryable (rate limiting)
    // 503 Service Unavailable - retryable
    // 5xx Server Errors - retryable
    status == 408 || status == 429 || status == 503 || (500..600).contains(&status)
}

#[cfg(test)]
mod tests {
    use super::*;

    // ========================================================================
    // RetryConfig tests
    // ========================================================================

    #[test]
    fn test_retry_config_default() {
        let config = RetryConfig::default();
        assert_eq!(config.max_retries, 3);
        assert_eq!(config.initial_delay_ms, 500);
        assert_eq!(config.max_delay_ms, 5000);
    }

    #[test]
    fn test_retry_config_clone() {
        let config = RetryConfig {
            max_retries: 5,
            initial_delay_ms: 100,
            max_delay_ms: 1000,
        };
        let cloned = config.clone();
        assert_eq!(cloned.max_retries, 5);
        assert_eq!(cloned.initial_delay_ms, 100);
        assert_eq!(cloned.max_delay_ms, 1000);
    }

    #[test]
    fn test_retry_config_debug() {
        let config = RetryConfig::default();
        let debug = format!("{:?}", config);
        assert!(debug.contains("RetryConfig"));
        assert!(debug.contains("max_retries"));
    }

    // ========================================================================
    // RpcClient tests
    // ========================================================================

    #[test]
    fn test_rpc_client_new() {
        let client = RpcClient::new("https://rpc.testnet.near.org");
        assert_eq!(client.url(), "https://rpc.testnet.near.org");
    }

    #[test]
    fn test_rpc_client_with_retry_config() {
        let config = RetryConfig {
            max_retries: 5,
            initial_delay_ms: 100,
            max_delay_ms: 1000,
        };
        let client = RpcClient::with_retry_config("https://rpc.example.com", config);
        assert_eq!(client.url(), "https://rpc.example.com");
    }

    #[test]
    fn test_rpc_client_clone() {
        let client = RpcClient::new("https://rpc.testnet.near.org");
        let cloned = client.clone();
        assert_eq!(cloned.url(), client.url());
    }

    #[test]
    fn test_rpc_client_debug() {
        let client = RpcClient::new("https://rpc.testnet.near.org");
        let debug = format!("{:?}", client);
        assert!(debug.contains("RpcClient"));
        assert!(debug.contains("rpc.testnet.near.org"));
    }

    // ========================================================================
    // sanitize_url tests
    // ========================================================================

    #[test]
    fn test_sanitize_url_plain() {
        assert_eq!(
            sanitize_url("https://rpc.mainnet.near.org"),
            "https://rpc.mainnet.near.org"
        );
    }

    #[test]
    fn test_sanitize_url_strips_query() {
        assert_eq!(
            sanitize_url("https://rpc.provider.com/v1?api_key=secret123"),
            "https://rpc.provider.com/v1"
        );
    }

    #[test]
    fn test_sanitize_url_strips_fragment() {
        assert_eq!(
            sanitize_url("https://rpc.provider.com/v1#section"),
            "https://rpc.provider.com/v1"
        );
    }

    #[test]
    fn test_sanitize_url_strips_query_and_fragment() {
        assert_eq!(
            sanitize_url("https://rpc.provider.com/v1?key=val#frag"),
            "https://rpc.provider.com/v1"
        );
    }

    // ========================================================================
    // is_retryable_status tests
    // ========================================================================

    #[test]
    fn test_is_retryable_status() {
        // Retryable statuses
        assert!(is_retryable_status(408)); // Request Timeout
        assert!(is_retryable_status(429)); // Too Many Requests
        assert!(is_retryable_status(500)); // Internal Server Error
        assert!(is_retryable_status(502)); // Bad Gateway
        assert!(is_retryable_status(503)); // Service Unavailable
        assert!(is_retryable_status(504)); // Gateway Timeout
        assert!(is_retryable_status(599)); // Edge of 5xx range

        // Non-retryable statuses
        assert!(!is_retryable_status(200)); // OK
        assert!(!is_retryable_status(201)); // Created
        assert!(!is_retryable_status(400)); // Bad Request
        assert!(!is_retryable_status(401)); // Unauthorized
        assert!(!is_retryable_status(403)); // Forbidden
        assert!(!is_retryable_status(404)); // Not Found
        assert!(!is_retryable_status(422)); // Unprocessable Entity
    }

    // ========================================================================
    // InvalidTxError parsing tests
    // ========================================================================

    #[test]
    fn test_invalid_transaction_parses_invalid_nonce() {
        use crate::types::InvalidTxError;
        let data = serde_json::json!({
            "TxExecutionError": {
                "InvalidTxError": {
                    "InvalidNonce": {
                        "tx_nonce": 5,
                        "ak_nonce": 10
                    }
                }
            }
        });
        let err = RpcError::invalid_transaction("invalid nonce", Some(data));
        match err {
            RpcError::InvalidTx(InvalidTxError::InvalidNonce { tx_nonce, ak_nonce }) => {
                assert_eq!(tx_nonce, 5);
                assert_eq!(ak_nonce, 10);
            }
            other => panic!("Expected InvalidTx(InvalidNonce), got: {other:?}"),
        }
    }

    #[test]
    fn test_invalid_transaction_parses_top_level_invalid_tx() {
        use crate::types::InvalidTxError;
        // Some RPC versions put InvalidTxError at the top level
        let data = serde_json::json!({
            "InvalidTxError": {
                "NotEnoughBalance": {
                    "signer_id": "alice.near",
                    "balance": "1000000000000000000000000",
                    "cost": "9000000000000000000000000"
                }
            }
        });
        let err = RpcError::invalid_transaction("insufficient balance", Some(data));
        assert!(
            matches!(
                err,
                RpcError::InvalidTx(InvalidTxError::NotEnoughBalance { .. })
            ),
            "Expected InvalidTx(NotEnoughBalance), got: {err:?}"
        );
    }

    #[test]
    fn test_invalid_transaction_falls_back_on_unparseable() {
        // When data doesn't contain a parseable InvalidTxError, falls back
        let data = serde_json::json!({ "SomeOtherError": {} });
        let err = RpcError::invalid_transaction("some error", Some(data));
        assert!(matches!(err, RpcError::InvalidTransaction { .. }));
    }

    // ========================================================================
    // NetworkConfig tests
    // ========================================================================

    #[test]
    fn test_mainnet_config() {
        assert!(MAINNET.rpc_url.contains("fastnear"));
        assert_eq!(MAINNET.network_id, "mainnet");
    }

    #[test]
    fn test_testnet_config() {
        assert!(TESTNET.rpc_url.contains("fastnear") || TESTNET.rpc_url.contains("test"));
        assert_eq!(TESTNET.network_id, "testnet");
    }

    // ========================================================================
    // parse_rpc_error tests (via RpcClient)
    // ========================================================================

    #[test]
    fn test_parse_rpc_error_unknown_account() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "UNKNOWN_ACCOUNT".to_string(),
                info: Some(serde_json::json!({
                    "requested_account_id": "nonexistent.near"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::AccountNotFound(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_access_key_legacy() {
        // Legacy `query` endpoint includes requested_account_id in info
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "UNKNOWN_ACCESS_KEY".to_string(),
                info: Some(serde_json::json!({
                    "requested_account_id": "alice.near",
                    "public_key": "ed25519:6E8sCci9badyRkXb3JoRpBj5p8C6Tw41ELDZoiihKEtp"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::AccessKeyNotFound {
                account_id,
                public_key,
            } => {
                assert_eq!(account_id.as_str(), "alice.near");
                assert!(public_key.to_string().contains("ed25519:"));
            }
            _ => panic!("Expected AccessKeyNotFound error, got {:?}", result),
        }
    }

    #[test]
    fn test_parse_rpc_error_unknown_access_key_experimental() {
        // EXPERIMENTAL_view_access_key omits requested_account_id from info
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: Some(serde_json::Value::String(
                "Access key for public key ed25519:6E8sCci9badyRkXb3JoRpBj5p8C6Tw41ELDZoiihKEtp does not exist while viewing".to_string()
            )),
            cause: Some(ErrorCause {
                name: "UNKNOWN_ACCESS_KEY".to_string(),
                info: Some(serde_json::json!({
                    "public_key": "ed25519:6E8sCci9badyRkXb3JoRpBj5p8C6Tw41ELDZoiihKEtp",
                    "block_height": 243789592,
                    "block_hash": "EC5A7qc6rixfN8T4T9Gkt78H5pAsvdcjAos8Z7kFLJgi"
                })),
            }),
            name: Some("HANDLER_ERROR".to_string()),
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::AccessKeyNotFound {
                account_id,
                public_key,
            } => {
                // account_id falls back to "unknown" — caller enriches it
                assert_eq!(account_id.as_str(), "unknown");
                assert!(public_key.to_string().contains("ed25519:"));
            }
            _ => panic!("Expected AccessKeyNotFound error, got {:?}", result),
        }
    }

    #[test]
    fn test_parse_rpc_error_invalid_account() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "INVALID_ACCOUNT".to_string(),
                info: Some(serde_json::json!({
                    "requested_account_id": "invalid@account"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::InvalidAccount(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_block() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Block not found".to_string(),
            data: Some(serde_json::json!("12345")),
            cause: Some(ErrorCause {
                name: "UNKNOWN_BLOCK".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::UnknownBlock(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_chunk() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Chunk not found".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "UNKNOWN_CHUNK".to_string(),
                info: Some(serde_json::json!({
                    "chunk_hash": "abc123"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::UnknownChunk(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_epoch() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Epoch not found".to_string(),
            data: Some(serde_json::json!("epoch123")),
            cause: Some(ErrorCause {
                name: "UNKNOWN_EPOCH".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::UnknownEpoch(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_receipt() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Receipt not found".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "UNKNOWN_RECEIPT".to_string(),
                info: Some(serde_json::json!({
                    "receipt_id": "receipt123"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::UnknownReceipt(_)));
    }

    #[test]
    fn test_parse_rpc_error_no_contract_code() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "No contract code".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "NO_CONTRACT_CODE".to_string(),
                info: Some(serde_json::json!({
                    "contract_account_id": "no-contract.near"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::ContractNotDeployed(_)));
    }

    #[test]
    fn test_parse_rpc_error_too_large_contract_state() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Contract state too large".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "TOO_LARGE_CONTRACT_STATE".to_string(),
                info: Some(serde_json::json!({
                    "account_id": "large-state.near"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::ContractStateTooLarge(_)));
    }

    #[test]
    fn test_parse_rpc_error_unavailable_shard() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Shard unavailable".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "UNAVAILABLE_SHARD".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::ShardUnavailable(_)));
    }

    #[test]
    fn test_parse_rpc_error_not_synced() {
        let client = RpcClient::new("https://example.com");

        // NO_SYNCED_BLOCKS
        let error = JsonRpcError {
            code: -32000,
            message: "No synced blocks".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "NO_SYNCED_BLOCKS".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::NodeNotSynced(_)));

        // NOT_SYNCED_YET
        let error = JsonRpcError {
            code: -32000,
            message: "Not synced yet".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "NOT_SYNCED_YET".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::NodeNotSynced(_)));
    }

    #[test]
    fn test_parse_rpc_error_invalid_shard_id() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Invalid shard ID".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "INVALID_SHARD_ID".to_string(),
                info: Some(serde_json::json!({
                    "shard_id": 99
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::InvalidShardId(_)));
    }

    #[test]
    fn test_parse_rpc_error_invalid_transaction() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Invalid transaction".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "INVALID_TRANSACTION".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::InvalidTransaction { .. }));
    }

    #[test]
    fn test_parse_rpc_error_timeout() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Request timed out".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "TIMEOUT_ERROR".to_string(),
                info: Some(serde_json::json!({
                    "transaction_hash": "tx123"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::RequestTimeout { .. }));
    }

    #[test]
    fn test_parse_rpc_error_parse_error() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32700,
            message: "Parse error".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "PARSE_ERROR".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::ParseError(_)));
    }

    #[test]
    fn test_parse_rpc_error_internal_error() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32603,
            message: "Internal error".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "INTERNAL_ERROR".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::InternalError(_)));
    }

    #[test]
    fn test_parse_rpc_error_contract_execution_legacy() {
        // Legacy `query` endpoint includes contract_id and method_name in info
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Contract execution failed".to_string(),
            data: None,
            cause: Some(ErrorCause {
                name: "CONTRACT_EXECUTION_ERROR".to_string(),
                info: Some(serde_json::json!({
                    "contract_id": "contract.near",
                    "method_name": "my_method"
                })),
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::ContractExecution {
                contract_id,
                method_name,
                ..
            } => {
                assert_eq!(contract_id.as_str(), "contract.near");
                assert_eq!(method_name.as_deref(), Some("my_method"));
            }
            _ => panic!("Expected ContractExecution error, got {:?}", result),
        }
    }

    #[test]
    fn test_parse_rpc_error_contract_execution_experimental() {
        // EXPERIMENTAL_call_function omits contract_id/method_name from info,
        // but includes vm_error and a data string
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: Some(serde_json::json!(
                "Function call returned an error: MethodResolveError(MethodNotFound)"
            )),
            cause: Some(ErrorCause {
                name: "CONTRACT_EXECUTION_ERROR".to_string(),
                info: Some(serde_json::json!({
                    "vm_error": { "MethodResolveError": "MethodNotFound" },
                    "block_height": 243803767,
                    "block_hash": "Et7So7jtsorkYLdVMMgV8gxA3Cfaztp75Ti6TPv2A"
                })),
            }),
            name: Some("HANDLER_ERROR".to_string()),
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::ContractExecution {
                contract_id,
                message,
                ..
            } => {
                // contract_id falls back to "unknown" — caller enriches it
                assert_eq!(contract_id.as_str(), "unknown");
                assert!(message.contains("MethodResolveError"));
            }
            _ => panic!("Expected ContractExecution error, got {:?}", result),
        }
    }

    #[test]
    fn test_parse_rpc_error_code_does_not_exist_experimental() {
        // EXPERIMENTAL_call_function returns CodeDoesNotExist as CONTRACT_EXECUTION_ERROR
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Server error".to_string(),
            data: Some(serde_json::json!(
                "Function call returned an error: CompilationError(CodeDoesNotExist { account_id: AccountId(\"nonexistent.testnet\") })"
            )),
            cause: Some(ErrorCause {
                name: "CONTRACT_EXECUTION_ERROR".to_string(),
                info: Some(serde_json::json!({
                    "vm_error": {
                        "CompilationError": {
                            "CodeDoesNotExist": {
                                "account_id": "nonexistent.testnet"
                            }
                        }
                    },
                    "block_height": 243803764,
                    "block_hash": "H33oNAtVZDJjhpncQb5LY6NxYzQLMMVLptq99mwmLmnj"
                })),
            }),
            name: Some("HANDLER_ERROR".to_string()),
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::ContractNotDeployed(account_id) => {
                assert_eq!(account_id.as_str(), "nonexistent.testnet");
            }
            _ => panic!("Expected ContractNotDeployed error, got {:?}", result),
        }
    }

    #[test]
    fn test_parse_rpc_error_fallback_account_not_exist() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Error".to_string(),
            data: Some(serde_json::json!(
                "account missing.near does not exist while viewing"
            )),
            cause: None,
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::AccountNotFound(_)));
    }

    #[test]
    fn test_parse_rpc_error_unknown_cause_fallback_to_generic() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32000,
            message: "Some error".to_string(),
            data: Some(serde_json::json!("some data")),
            cause: Some(ErrorCause {
                name: "UNKNOWN_ERROR_TYPE".to_string(),
                info: None,
            }),
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        assert!(matches!(result, RpcError::Rpc { .. }));
    }

    #[test]
    fn test_parse_rpc_error_no_cause_fallback_to_generic() {
        let client = RpcClient::new("https://example.com");
        let error = JsonRpcError {
            code: -32600,
            message: "Invalid request".to_string(),
            data: None,
            cause: None,
            name: None,
        };
        let result = client.parse_rpc_error(&error);
        match result {
            RpcError::Rpc { code, message, .. } => {
                assert_eq!(code, -32600);
                assert_eq!(message, "Invalid request");
            }
            _ => panic!("Expected generic Rpc error"),
        }
    }

    // ========================================================================
    // block_id_or_null tests
    // ========================================================================

    #[test]
    fn test_block_id_or_null_with_none() {
        let result = block_id_or_null(None);
        assert!(result.is_null());
    }

    #[test]
    fn test_block_id_or_null_with_height() {
        let block = BlockReference::at_height(12345);
        let result = block_id_or_null(Some(&block));
        assert_eq!(result, serde_json::json!(12345));
    }

    #[test]
    fn test_block_id_or_null_with_hash() {
        let hash = CryptoHash::hash(b"test block");
        let block = BlockReference::at_hash(hash);
        let result = block_id_or_null(Some(&block));
        assert_eq!(result, serde_json::json!(hash.to_string()));
    }

    #[test]
    fn test_block_id_or_null_with_finality_falls_back_to_null() {
        let block = BlockReference::final_();
        let result = block_id_or_null(Some(&block));
        assert!(result.is_null(), "finality variants should map to null");

        let block = BlockReference::optimistic();
        let result = block_id_or_null(Some(&block));
        assert!(result.is_null(), "optimistic should map to null");
    }

    #[test]
    fn test_block_id_or_null_with_sync_checkpoint_falls_back_to_null() {
        let block = BlockReference::genesis();
        let result = block_id_or_null(Some(&block));
        assert!(result.is_null(), "sync checkpoint should map to null");
    }
}