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| 1 | +# Gas Estimation for Soroban Operations |
| 2 | + |
| 3 | +This SDK provides comprehensive gas estimation capabilities, allowing users to preview transaction costs before executing complex contract operations. |
| 4 | + |
| 5 | +## Features |
| 6 | + |
| 7 | +- **Accurate Simulation**: Uses Soroban RPC simulation to get precise resource measurements |
| 8 | +- **Cost Breakdown**: Detailed breakdown of base fees, resource fees, and refundable portions |
| 9 | +- **Resource Metrics**: CPU instructions, read/write bytes, and storage operations |
| 10 | +- **Safety Buffer**: Configurable fee buffer multiplier to ensure transactions succeed |
| 11 | +- **Offline Estimation**: Rough estimates for air-gapped or hardware wallet flows |
| 12 | +- **Formatted Display**: Human-readable gas reports for UI display |
| 13 | + |
| 14 | +## Quick Start |
| 15 | + |
| 16 | +### Basic Gas Estimation |
| 17 | + |
| 18 | +```typescript |
| 19 | +import { createTokenboundSdk } from '@crowdpass/tokenbound-sdk'; |
| 20 | + |
| 21 | +const sdk = createTokenboundSdk({ |
| 22 | + horizonUrl: 'https://horizon-testnet.stellar.org', |
| 23 | + sorobanRpcUrl: 'https://soroban-testnet.stellar.org', |
| 24 | + networkPassphrase: 'Test SDF Network ; September 2015', |
| 25 | + simulationSource: 'GABC...', // Default source for simulations |
| 26 | +}); |
| 27 | + |
| 28 | +// Estimate gas for a contract call |
| 29 | +const gas = await sdk.estimateGas('eventManager', { |
| 30 | + contractId: 'CDP...', |
| 31 | + method: 'create_event', |
| 32 | + args: [/* ... */] |
| 33 | +}, { |
| 34 | + source: 'GABC...', // Optional: override simulation source |
| 35 | + feeBufferMultiplier: 1.3, // 30% buffer for safety |
| 36 | +}); |
| 37 | + |
| 38 | +console.log(gas.summary); |
| 39 | +// "Estimated gas: 0.0001234 XLM (max: 0.0001481 XLM). Resources: 50000 instructions, 1024 bytes I/O." |
| 40 | +``` |
| 41 | + |
| 42 | +### Formatted Display |
| 43 | + |
| 44 | +```typescript |
| 45 | +import { formatGasDisplay } from '@crowdpass/tokenbound-sdk'; |
| 46 | + |
| 47 | +// Print detailed gas report |
| 48 | +console.log(formatGasDisplay(gas, { |
| 49 | + currency: 'XLM', |
| 50 | + decimals: 7, |
| 51 | + showResources: true, |
| 52 | + showCosts: true, |
| 53 | +})); |
| 54 | + |
| 55 | +// Output: |
| 56 | +// ═══════════════════════════════════════════ |
| 57 | +// GAS ESTIMATION REPORT |
| 58 | +// ═══════════════════════════════════════════ |
| 59 | +// |
| 60 | +// 💰 ESTIMATED COSTS |
| 61 | +// ─────────────────────────────────────────── |
| 62 | +// Base Fee: 0.0000100 XLM |
| 63 | +// Resource Fee: 0.0001134 XLM |
| 64 | +// Refundable: 0.0000100 XLM |
| 65 | +// ───────────────────────────────────────── |
| 66 | +// TOTAL: 0.0001234 XLM |
| 67 | +// Max (buffered): 0.0001481 XLM |
| 68 | +// |
| 69 | +// ⚡ RESOURCE USAGE |
| 70 | +// ─────────────────────────────────────────── |
| 71 | +// Instructions: 50,000 |
| 72 | +// Read Bytes: 1,024 |
| 73 | +// Write Bytes: 512 |
| 74 | +// ... |
| 75 | +// |
| 76 | +// ═══════════════════════════════════════════ |
| 77 | +// Estimated gas: 0.0001234 XLM (max: 0.0001481 XLM). Resources: 50000 instructions, 1024 bytes I/O. |
| 78 | +// ═══════════════════════════════════════════ |
| 79 | +``` |
| 80 | + |
| 81 | +## API Reference |
| 82 | + |
| 83 | +### `sdk.estimateGas(contract, artifact, options)` |
| 84 | + |
| 85 | +Estimates gas costs by simulating a transaction against the actual contract state. |
| 86 | + |
| 87 | +**Parameters:** |
| 88 | +- `contract`: Contract name ('eventManager', 'ticketNft', etc.) |
| 89 | +- `artifact`: Contract call details including contractId, method, and args |
| 90 | +- `options`: Gas estimation options |
| 91 | + - `source`: Source account for simulation |
| 92 | + - `fee`: Base fee override (in stroops) |
| 93 | + - `feeBufferMultiplier`: Safety buffer multiplier (default: 1.2) |
| 94 | + - `includeRawSimulation`: Include raw RPC response (default: false) |
| 95 | + - `correlationId`: Tracing correlation ID |
| 96 | + |
| 97 | +**Returns:** `GasEstimation` object with: |
| 98 | +- `costs`: Detailed cost breakdown |
| 99 | + - `baseFee`: Base transaction fee |
| 100 | + - `resourceFee`: Fee for resource consumption |
| 101 | + - `refundableFee`: Portion refunded on success |
| 102 | + - `totalFee`: Total estimated fee |
| 103 | + - `maxFee`: Maximum fee with buffer applied |
| 104 | +- `resources`: Resource usage metrics |
| 105 | + - `instructions`: CPU instructions executed |
| 106 | + - `readBytes`: Bytes read from storage |
| 107 | + - `writeBytes`: Bytes written to storage |
| 108 | + - `entryReads`: Contract entries read |
| 109 | + - `entryWrites`: Contract entries written |
| 110 | + - `transactionSizeBytes`: Transaction XDR size |
| 111 | + - `metadataSizeBytes`: Soroban metadata size |
| 112 | +- `success`: Whether simulation succeeded |
| 113 | +- `summary`: Human-readable summary string |
| 114 | +- `rawSimulation`: Raw RPC response (if requested) |
| 115 | + |
| 116 | +### `formatGasDisplay(estimation, options)` |
| 117 | + |
| 118 | +Formats a gas estimation into a multi-line human-readable report. |
| 119 | + |
| 120 | +```typescript |
| 121 | +import { formatGasDisplay } from '@crowdpass/tokenbound-sdk'; |
| 122 | + |
| 123 | +const report = formatGasDisplay(gas, { |
| 124 | + currency: 'XLM', // 'XLM' or 'stroops' |
| 125 | + decimals: 7, // Decimal places for XLM |
| 126 | + showResources: true, // Include resource breakdown |
| 127 | + showCosts: true, // Include cost breakdown |
| 128 | +}); |
| 129 | +``` |
| 130 | + |
| 131 | +### `formatGasCost(stroops, currency, decimals)` |
| 132 | + |
| 133 | +Formats a single gas cost value. |
| 134 | + |
| 135 | +```typescript |
| 136 | +import { formatGasCost } from '@crowdpass/tokenbound-sdk'; |
| 137 | + |
| 138 | +formatGasCost(1234000, 'XLM', 7); // "0.1234000 XLM" |
| 139 | +formatGasCost(1234000, 'stroops'); // "1,234,000 stroops" |
| 140 | +``` |
| 141 | + |
| 142 | +### `calculateRecommendedFee(gasEstimation, priority)` |
| 143 | + |
| 144 | +Calculates a recommended fee based on priority level. |
| 145 | + |
| 146 | +```typescript |
| 147 | +import { calculateRecommendedFee } from '@crowdpass/tokenbound-sdk'; |
| 148 | + |
| 149 | +const recommendedFee = calculateRecommendedFee(gas, 'high'); |
| 150 | +// Returns fee with 1.5x multiplier for high priority |
| 151 | +``` |
| 152 | + |
| 153 | +### `checkResourceWarnings(estimation)` |
| 154 | + |
| 155 | +Checks for potentially problematic resource usage. |
| 156 | + |
| 157 | +```typescript |
| 158 | +import { checkResourceWarnings } from '@crowdpass/tokenbound-sdk'; |
| 159 | + |
| 160 | +const { hasWarnings, warnings } = checkResourceWarnings(gas); |
| 161 | +if (hasWarnings) { |
| 162 | + console.warn('Resource concerns:', warnings); |
| 163 | + // ["High instruction count (150,000,000). May exceed network limits."] |
| 164 | +} |
| 165 | +``` |
| 166 | + |
| 167 | +### `compareGasEstimations(before, after)` |
| 168 | + |
| 169 | +Compares two gas estimations to show the impact of changes. |
| 170 | + |
| 171 | +```typescript |
| 172 | +import { compareGasEstimations } from '@crowdpass/tokenbound-sdk'; |
| 173 | + |
| 174 | +const comparison = compareGasEstimations(oldGas, newGas); |
| 175 | +console.log(comparison.summary); |
| 176 | +// "Gas cost increase: 0.0000500 XLM (500000 stroops)" |
| 177 | +``` |
| 178 | + |
| 179 | +## Offline Gas Estimation |
| 180 | + |
| 181 | +For air-gapped or hardware wallet flows where network access isn't available: |
| 182 | + |
| 183 | +```typescript |
| 184 | +import { OfflineTransactionBuilder } from '@crowdpass/tokenbound-sdk'; |
| 185 | + |
| 186 | +const builder = new OfflineTransactionBuilder('Test SDF Network ; September 2015'); |
| 187 | + |
| 188 | +const account = { |
| 189 | + accountId: 'GABC...', |
| 190 | + sequenceNumber: '123456789', |
| 191 | +}; |
| 192 | + |
| 193 | +const artifact = { |
| 194 | + contractId: 'CDP...', |
| 195 | + method: 'create_event', |
| 196 | + args: [/* ... */], |
| 197 | +}; |
| 198 | + |
| 199 | +// Rough estimate without network |
| 200 | +const estimate = builder.estimateGasOffline(account, artifact, 100, 1.2); |
| 201 | + |
| 202 | +console.log(estimate.summary); |
| 203 | +// "Estimated gas: 0.0000150 XLM (max: 0.0000180 XLM). Tx size: 450 bytes." |
| 204 | +``` |
| 205 | + |
| 206 | +**Note:** Offline estimates are less accurate than online simulation as they cannot account for current contract state or resource contention. |
| 207 | + |
| 208 | +## Integration with Contract Calls |
| 209 | + |
| 210 | +### Estimate Before Write |
| 211 | + |
| 212 | +```typescript |
| 213 | +// First, estimate the gas |
| 214 | +const gas = await sdk.estimateGas('eventManager', artifact, { |
| 215 | + source: organizerAddress, |
| 216 | +}); |
| 217 | + |
| 218 | +// Check if user can afford it |
| 219 | +if (gas.costs.maxFee > userBalance) { |
| 220 | + throw new Error(`Insufficient balance. Need ${formatGasCost(gas.costs.maxFee)}`); |
| 221 | +} |
| 222 | + |
| 223 | +// Show confirmation with gas estimate |
| 224 | +if (confirm(`This will cost approximately ${gas.summary}. Proceed?`)) { |
| 225 | + // Execute the actual transaction |
| 226 | + const result = await sdk.write('eventManager', artifact, { |
| 227 | + source: organizerAddress, |
| 228 | + signTransaction: wallet.sign, |
| 229 | + }); |
| 230 | +} |
| 231 | +``` |
| 232 | + |
| 233 | +### Batch Operations |
| 234 | + |
| 235 | +```typescript |
| 236 | +const operations = [artifact1, artifact2, artifact3]; |
| 237 | + |
| 238 | +// Estimate all operations |
| 239 | +const estimates = await Promise.all( |
| 240 | + operations.map(op => sdk.estimateGas('eventManager', op, { source })) |
| 241 | +); |
| 242 | + |
| 243 | +// Calculate total cost |
| 244 | +const totalMaxFee = estimates.reduce((sum, e) => sum + e.costs.maxFee, 0); |
| 245 | + |
| 246 | +console.log(`Total estimated cost for ${operations.length} operations:`); |
| 247 | +console.log(` Max: ${formatGasCost(totalMaxFee)}`); |
| 248 | +``` |
| 249 | + |
| 250 | +## Best Practices |
| 251 | + |
| 252 | +1. **Always Use Buffer**: Set `feeBufferMultiplier` to at least 1.2 (20%) to handle network congestion |
| 253 | +2. **Check Success**: Verify `gas.success` before proceeding with actual transactions |
| 254 | +3. **Handle Failures**: If simulation fails, the error is in `gas.summary` |
| 255 | +4. **Cache Estimates**: Gas estimates can be cached for similar operations within a short time window |
| 256 | +5. **Offline Fallback**: Use `estimateGasOffline` for hardware wallet flows where online simulation isn't possible |
| 257 | + |
| 258 | +## Troubleshooting |
| 259 | + |
| 260 | +### "Simulation failed" errors |
| 261 | +- Check that the contract ID is correct |
| 262 | +- Verify the method name and arguments match the contract spec |
| 263 | +- Ensure the source account exists on the network |
| 264 | + |
| 265 | +### High gas costs |
| 266 | +- Large argument values increase transaction size |
| 267 | +- Complex operations with many storage reads/writes cost more |
| 268 | +- Consider batching multiple operations into a single transaction |
| 269 | + |
| 270 | +### Fee buffer exceeded |
| 271 | +- Network congestion can cause actual fees to exceed estimates |
| 272 | +- Increase `feeBufferMultiplier` during high-traffic periods |
| 273 | +- Monitor recent ledger fees to set appropriate buffers |
| 274 | + |
| 275 | +## TypeScript Types |
| 276 | + |
| 277 | +```typescript |
| 278 | +interface GasEstimation { |
| 279 | + costs: { |
| 280 | + baseFee: number; // stroops |
| 281 | + resourceFee: number; // stroops |
| 282 | + refundableFee: number; // stroops |
| 283 | + totalFee: number; // stroops |
| 284 | + maxFee: number; // stroops |
| 285 | + }; |
| 286 | + resources: { |
| 287 | + instructions: number; |
| 288 | + readBytes: number; |
| 289 | + writeBytes: number; |
| 290 | + entryReads: number; |
| 291 | + entryWrites: number; |
| 292 | + transactionSizeBytes: number; |
| 293 | + metadataSizeBytes: number; |
| 294 | + }; |
| 295 | + success: boolean; |
| 296 | + summary: string; |
| 297 | + rawSimulation?: unknown; |
| 298 | +} |
| 299 | + |
| 300 | +interface GasEstimateOptions extends InvokeOptions { |
| 301 | + includeRawSimulation?: boolean; |
| 302 | + feeBufferMultiplier?: number; |
| 303 | +} |
| 304 | +``` |
| 305 | + |
| 306 | +--- |
| 307 | + |
| 308 | +For more information on Soroban fees, see the [Stellar Documentation](https://soroban.stellar.org/docs/fundamentals/fees-and-metering). |
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