feat: add swap prepare payloads for external signers

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "chain-pilot"
-version = "1.1.0"
+version = "1.2.0-rc.2"
 description = "A CLI tool for on-chain DeFi operations on EVM-compatible networks"
 homepage = "https://github.com/DODOEX/ChainPilot"
 documentation = "https://github.com/DODOEX/ChainPilot#readme"

README.md

@@ -252,6 +252,42 @@ chainpilot swap execute --quote-id <QUOTE_ID> --private-key 0x... --skip-estimat
 | `--gas-buffer-pct`  | Add N% buffer on top of `eth_estimateGas` result (e.g. `20` = +20%)     |
 | `--skip-estimate`   | Skip `eth_estimateGas` and use the quote's gas estimate directly         |
 
+**Prepare an unsigned transaction for an external signer:**
+```bash
+# Swap execution payload from a saved quote
+chainpilot --json swap prepare execute --quote-id <QUOTE_ID> --wallet 0xYourAddress
+
+# ERC-20 approval payload
+chainpilot --json swap prepare approve --quote-id <QUOTE_ID> --wallet 0xYourAddress
+chainpilot --json swap prepare approve \
+  --token USDC \
+  --spender 0xSpenderAddr \
+  --amount 100 \
+  --wallet 0xYourAddress
+
+# ERC-20 revoke payload
+chainpilot --json swap prepare revoke \
+  --token 0xTokenAddr \
+  --spender 0xSpenderAddr \
+  --wallet 0xYourAddress
+```
+
+`swap prepare` does not sign or broadcast. In JSON mode it returns a stable
+unsigned transaction payload with `source`, `operation`, `chain_id`, `caip2`,
+`from`, `transaction { to, value, data, chain_id }`, and risk metadata. This is
+intended for external signing systems such as Privy; user confirmation,
+authorization checks, signing, and broadcasting must happen outside ChainPilot.
+Use `swap simulate` to inspect route execution, gas, and warnings before this
+step; use `swap prepare` only when an external signer needs the exact unsigned
+transaction object.
+
+`swap prepare approve --quote-id` only applies when the quote spends an ERC-20
+input token. Native input tokens such as ETH, MATIC, BNB, or the chain native
+asset do not require ERC-20 approval and are rejected. For explicit approvals,
+`--token` accepts either a token address or a resolvable symbol from the
+tokenlist/cache/custom token store; use the token address when the symbol is
+ambiguous or unavailable.
+
 **Check transaction status:**
 ```bash
 chainpilot swap status --tx-hash 0x...

src/cli/swap.rs

@@ -13,6 +13,8 @@ pub enum SwapAction {
     Quote(QuoteArgs),
     /// Simulate a swap from a saved quote
     Simulate(SimulateArgs),
+    /// Prepare an unsigned transaction payload for an external signer
+    Prepare(PrepareCmd),
     /// Execute a swap (requires wallet)
     Execute(ExecuteArgs),
     /// Check swap transaction status
@@ -55,6 +57,71 @@ pub struct SimulateArgs {
     pub wallet: Option<String>,
 }
 
+#[derive(Args)]
+pub struct PrepareCmd {
+    #[command(subcommand)]
+    pub action: PrepareAction,
+}
+
+#[derive(Subcommand)]
+pub enum PrepareAction {
+    /// Prepare a swap execution transaction from a saved quote
+    Execute(PrepareExecuteArgs),
+    /// Prepare an ERC-20 approval transaction
+    Approve(PrepareApproveArgs),
+    /// Prepare an ERC-20 revoke transaction
+    Revoke(PrepareRevokeArgs),
+}
+
+#[derive(Args)]
+pub struct PrepareExecuteArgs {
+    /// Quote ID returned by `chainpilot swap quote`
+    #[arg(long)]
+    pub quote_id: String,
+
+    /// Wallet address that will sign and send the transaction via an external signer
+    #[arg(long, env = "WALLET_ADDRESS")]
+    pub wallet: Option<String>,
+}
+
+#[derive(Args)]
+pub struct PrepareApproveArgs {
+    /// Quote ID to derive token and spender from (uses from-token and DODOApprove spender)
+    #[arg(long)]
+    pub quote_id: Option<String>,
+
+    /// Token symbol or address to approve (overrides quote's from-token)
+    #[arg(long)]
+    pub token: Option<String>,
+
+    /// Spender contract address (overrides quote's spender)
+    #[arg(long)]
+    pub spender: Option<String>,
+
+    /// Amount to approve in human-readable units (omit for unlimited / U256::MAX)
+    #[arg(long)]
+    pub amount: Option<String>,
+
+    /// Wallet address that will sign and send the transaction via an external signer
+    #[arg(long, env = "WALLET_ADDRESS")]
+    pub wallet: Option<String>,
+}
+
+#[derive(Args)]
+pub struct PrepareRevokeArgs {
+    /// Token contract address
+    #[arg(long)]
+    pub token: String,
+
+    /// Spender contract address
+    #[arg(long)]
+    pub spender: String,
+
+    /// Wallet address that will sign and send the transaction via an external signer
+    #[arg(long, env = "WALLET_ADDRESS")]
+    pub wallet: Option<String>,
+}
+
 #[derive(Args)]
 pub struct ExecuteArgs {
     /// Quote ID returned by `chainpilot swap quote`