archy/core/archipelago/src/wallet/mint_client.rs

//! HTTP client for Cashu mint API (NUT-01 through NUT-06).
//!
//! Communicates with a Cashu-compatible mint for:
//! - Keyset discovery (GET /v1/keys, /v1/keysets)
//! - Mint quotes and minting (POST /v1/mint/quote/bolt11, /v1/mint/bolt11)
//! - Melt quotes and melting (POST /v1/melt/quote/bolt11, /v1/melt/bolt11)
//! - Token swaps (POST /v1/swap)
//! - Proof state checks (POST /v1/checkstate)

use super::bdhke;
use super::cashu::{
    amount_to_denominations, BlindSignature, BlindedMessageRequest, CashuToken, MintKeyset, Proof,
};
use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use tracing::debug;

/// Default timeout for mint API calls.
const MINT_TIMEOUT_SECS: u64 = 10;
/// Timeout for heavy operations (minting with Lightning payment).
const MINT_HEAVY_TIMEOUT_SECS: u64 = 30;

/// Mint quote response (NUT-04).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MintQuote {
    pub quote: String,
    pub request: String, // BOLT11 Lightning invoice
    pub state: String,   // "UNPAID", "PAID", "ISSUED"
    #[serde(default)]
    pub expiry: u64,
}

/// Melt quote response (NUT-05).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MeltQuote {
    pub quote: String,
    pub amount: u64,
    pub fee_reserve: u64,
    pub state: String, // "UNPAID", "PENDING", "PAID"
    #[serde(default)]
    pub expiry: u64,
}

/// Token state from checkstate (NUT-07).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProofState {
    #[serde(rename = "Y")]
    pub y: String,
    pub state: String, // "UNSPENT", "SPENT", "PENDING"
}

/// Result of a swap operation.
pub struct SwapResult {
    pub new_proofs: Vec<Proof>,
}

/// Result of a mint operation.
pub struct MintResult {
    pub proofs: Vec<Proof>,
}

/// HTTP client for a single Cashu mint.
pub struct MintClient {
    url: String,
    client: reqwest::Client,
}

impl MintClient {
    /// Create a new mint client for the given mint URL.
    pub fn new(mint_url: &str) -> Result<Self> {
        let client = reqwest::Client::builder()
            .timeout(std::time::Duration::from_secs(MINT_TIMEOUT_SECS))
            .build()
            .context("Failed to build HTTP client for mint")?;

        Ok(Self {
            url: mint_url.trim_end_matches('/').to_string(),
            client,
        })
    }

    /// Create a mint client with a custom reqwest client (e.g., for Tor proxy).
    pub fn with_client(mint_url: &str, client: reqwest::Client) -> Self {
        Self {
            url: mint_url.trim_end_matches('/').to_string(),
            client,
        }
    }

    pub fn url(&self) -> &str {
        &self.url
    }

    // ── Keyset discovery (NUT-01, NUT-02) ──

    /// Fetch the active keyset from the mint.
    pub async fn get_keys(&self) -> Result<Vec<MintKeyset>> {
        let url = format!("{}/v1/keys", self.url);
        let res = self
            .client
            .get(&url)
            .send()
            .await
            .context("Failed to fetch mint keys")?;

        if !res.status().is_success() {
            anyhow::bail!("Mint keys request failed: {}", res.status());
        }

        let body: serde_json::Value = res.json().await.context("Failed to parse mint keys")?;
        let keysets: Vec<MintKeyset> = serde_json::from_value(
            body.get("keysets")
                .cloned()
                .unwrap_or(serde_json::json!([])),
        )
        .context("Failed to parse keysets")?;

        Ok(keysets)
    }

    /// Get the active keyset for the "sat" unit.
    pub async fn get_active_sat_keyset(&self) -> Result<MintKeyset> {
        let keysets = self.get_keys().await?;
        keysets
            .into_iter()
            .find(|k| {
                // Find active sat keyset — check keys map is non-empty
                !k.keys.is_empty()
            })
            .ok_or_else(|| anyhow::anyhow!("No active keyset found at mint {}", self.url))
    }

    // ── Mint quotes (NUT-04) ──

    /// Request a mint quote — returns a Lightning invoice to pay.
    pub async fn mint_quote(&self, amount: u64) -> Result<MintQuote> {
        let url = format!("{}/v1/mint/quote/bolt11", self.url);
        let res = self
            .client
            .post(&url)
            .json(&serde_json::json!({ "amount": amount, "unit": "sat" }))
            .send()
            .await
            .context("Failed to request mint quote")?;

        if !res.status().is_success() {
            let status = res.status();
            let body = res.text().await.unwrap_or_default();
            anyhow::bail!("Mint quote failed ({}): {}", status, body);
        }

        res.json().await.context("Failed to parse mint quote")
    }

    /// Check the status of a mint quote.
    pub async fn mint_quote_status(&self, quote_id: &str) -> Result<MintQuote> {
        let url = format!("{}/v1/mint/quote/bolt11/{}", self.url, quote_id);
        let res = self
            .client
            .get(&url)
            .send()
            .await
            .context("Failed to check mint quote status")?;

        if !res.status().is_success() {
            anyhow::bail!("Mint quote status check failed: {}", res.status());
        }

        res.json()
            .await
            .context("Failed to parse mint quote status")
    }

    /// Mint tokens after Lightning invoice has been paid.
    /// Performs BDHKE blinding, sends blinded messages to mint, unblinds signatures.
    pub async fn mint_tokens(&self, quote_id: &str, amount: u64) -> Result<MintResult> {
        let keyset = self.get_active_sat_keyset().await?;
        let denominations = amount_to_denominations(amount);

        let mut blinded_messages = Vec::new();
        let mut blinding_data = Vec::new(); // (secret, blinding_factor, amount)

        for &denom in &denominations {
            let secret = bdhke::generate_secret();
            let r = bdhke::random_blinding_factor();
            let blinded = bdhke::blind_message(&secret, &r)?;

            blinded_messages.push(BlindedMessageRequest {
                amount: denom,
                id: keyset.id.clone(),
                b_prime: hex::encode(blinded.b_prime.serialize()),
            });
            blinding_data.push((secret, r, denom));
        }

        let url = format!("{}/v1/mint/bolt11", self.url);
        let client = reqwest::Client::builder()
            .timeout(std::time::Duration::from_secs(MINT_HEAVY_TIMEOUT_SECS))
            .build()
            .context("Failed to build client for mint operation")?;

        let res = client
            .post(&url)
            .json(&serde_json::json!({
                "quote": quote_id,
                "outputs": blinded_messages,
            }))
            .send()
            .await
            .context("Failed to mint tokens")?;

        if !res.status().is_success() {
            let status = res.status();
            let body = res.text().await.unwrap_or_default();
            anyhow::bail!("Mint tokens failed ({}): {}", status, body);
        }

        let body: serde_json::Value = res.json().await.context("Failed to parse mint response")?;
        let signatures: Vec<BlindSignature> = serde_json::from_value(
            body.get("signatures")
                .cloned()
                .unwrap_or(serde_json::json!([])),
        )
        .context("Failed to parse blind signatures")?;

        if signatures.len() != blinding_data.len() {
            anyhow::bail!(
                "Mint returned {} signatures, expected {}",
                signatures.len(),
                blinding_data.len()
            );
        }

        // Unblind signatures to get real proofs
        let mut proofs = Vec::new();
        for (sig, (secret, r, amount)) in signatures.iter().zip(blinding_data.iter()) {
            let c_prime = sig.c_prime_as_pubkey()?;
            let mint_key = keyset.key_for_amount(*amount)?;
            let c = bdhke::unblind_signature(&c_prime, r, &mint_key)?;

            proofs.push(Proof {
                amount: *amount,
                id: keyset.id.clone(),
                secret: String::from_utf8_lossy(secret).to_string(),
                c: hex::encode(c.serialize()),
            });
        }

        debug!("Minted {} proofs totaling {} sats", proofs.len(), amount);
        Ok(MintResult { proofs })
    }

    // ── Melt (NUT-05) ──

    /// Request a melt quote — how much it costs to pay a Lightning invoice.
    pub async fn melt_quote(&self, bolt11: &str) -> Result<MeltQuote> {
        let url = format!("{}/v1/melt/quote/bolt11", self.url);
        let res = self
            .client
            .post(&url)
            .json(&serde_json::json!({ "request": bolt11, "unit": "sat" }))
            .send()
            .await
            .context("Failed to request melt quote")?;

        if !res.status().is_success() {
            let status = res.status();
            let body = res.text().await.unwrap_or_default();
            anyhow::bail!("Melt quote failed ({}): {}", status, body);
        }

        res.json().await.context("Failed to parse melt quote")
    }

    /// Melt tokens — pay a Lightning invoice using ecash proofs.
    pub async fn melt_tokens(&self, quote_id: &str, proofs: &[Proof]) -> Result<MeltQuote> {
        let url = format!("{}/v1/melt/bolt11", self.url);
        let client = reqwest::Client::builder()
            .timeout(std::time::Duration::from_secs(MINT_HEAVY_TIMEOUT_SECS))
            .build()
            .context("Failed to build client for melt operation")?;

        let res = client
            .post(&url)
            .json(&serde_json::json!({
                "quote": quote_id,
                "inputs": proofs,
            }))
            .send()
            .await
            .context("Failed to melt tokens")?;

        if !res.status().is_success() {
            let status = res.status();
            let body = res.text().await.unwrap_or_default();
            anyhow::bail!("Melt failed ({}): {}", status, body);
        }

        res.json().await.context("Failed to parse melt response")
    }

    // ── Swap (NUT-03) ──

    /// Swap proofs for new proofs of different denominations.
    /// This is how we "receive" a token — swap it for fresh proofs that only we know.
    pub async fn swap(&self, inputs: &[Proof], target_amounts: &[u64]) -> Result<SwapResult> {
        let keyset = self.get_active_sat_keyset().await?;

        let mut blinded_messages = Vec::new();
        let mut blinding_data = Vec::new();

        for &amount in target_amounts {
            let secret = bdhke::generate_secret();
            let r = bdhke::random_blinding_factor();
            let blinded = bdhke::blind_message(&secret, &r)?;

            blinded_messages.push(BlindedMessageRequest {
                amount,
                id: keyset.id.clone(),
                b_prime: hex::encode(blinded.b_prime.serialize()),
            });
            blinding_data.push((secret, r, amount));
        }

        let url = format!("{}/v1/swap", self.url);
        let res = self
            .client
            .post(&url)
            .json(&serde_json::json!({
                "inputs": inputs,
                "outputs": blinded_messages,
            }))
            .send()
            .await
            .context("Failed to swap tokens")?;

        if !res.status().is_success() {
            let status = res.status();
            let body = res.text().await.unwrap_or_default();
            anyhow::bail!("Swap failed ({}): {}", status, body);
        }

        let body: serde_json::Value = res.json().await.context("Failed to parse swap response")?;
        let signatures: Vec<BlindSignature> = serde_json::from_value(
            body.get("signatures")
                .cloned()
                .unwrap_or(serde_json::json!([])),
        )
        .context("Failed to parse swap signatures")?;

        if signatures.len() != blinding_data.len() {
            anyhow::bail!(
                "Swap returned {} signatures, expected {}",
                signatures.len(),
                blinding_data.len()
            );
        }

        let mut new_proofs = Vec::new();
        for (sig, (secret, r, amount)) in signatures.iter().zip(blinding_data.iter()) {
            let c_prime = sig.c_prime_as_pubkey()?;
            let mint_key = keyset.key_for_amount(*amount)?;
            let c = bdhke::unblind_signature(&c_prime, r, &mint_key)?;

            new_proofs.push(Proof {
                amount: *amount,
                id: keyset.id.clone(),
                secret: String::from_utf8_lossy(secret).to_string(),
                c: hex::encode(c.serialize()),
            });
        }

        debug!(
            "Swapped {} inputs for {} new proofs",
            inputs.len(),
            new_proofs.len()
        );
        Ok(SwapResult { new_proofs })
    }

    // ── Check state (NUT-07) ──

    /// Check whether proofs are spent, unspent, or pending.
    pub async fn check_state(&self, proofs: &[Proof]) -> Result<Vec<ProofState>> {
        // Compute Y = hash_to_curve(secret) for each proof
        let ys: Vec<String> = proofs
            .iter()
            .map(|p| {
                let y = bdhke::hash_to_curve(p.secret.as_bytes())?;
                Ok(hex::encode(y.serialize()))
            })
            .collect::<Result<Vec<_>>>()?;

        let url = format!("{}/v1/checkstate", self.url);
        let res = self
            .client
            .post(&url)
            .json(&serde_json::json!({ "Ys": ys }))
            .send()
            .await
            .context("Failed to check proof state")?;

        if !res.status().is_success() {
            anyhow::bail!("Check state failed: {}", res.status());
        }

        let body: serde_json::Value = res
            .json()
            .await
            .context("Failed to parse checkstate response")?;
        let states: Vec<ProofState> =
            serde_json::from_value(body.get("states").cloned().unwrap_or(serde_json::json!([])))
                .context("Failed to parse proof states")?;

        Ok(states)
    }

    /// Receive a CashuToken by swapping its proofs for fresh ones.
    /// This prevents double-spend and ensures only we can spend the new proofs.
    pub async fn receive_token(&self, token: &CashuToken) -> Result<Vec<Proof>> {
        let mut all_new_proofs = Vec::new();

        for entry in &token.token {
            if entry.mint != self.url {
                debug!(
                    "Skipping proofs from different mint {} (ours: {})",
                    entry.mint, self.url
                );
                continue;
            }

            let total: u64 = entry.proofs.iter().map(|p| p.amount).sum();
            let target_amounts = amount_to_denominations(total);

            let result = self.swap(&entry.proofs, &target_amounts).await?;
            all_new_proofs.extend(result.new_proofs);
        }

        if all_new_proofs.is_empty() {
            anyhow::bail!("No proofs could be swapped — mint mismatch or empty token");
        }

        Ok(all_new_proofs)
    }
}

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

    #[test]
    fn test_mint_client_url_normalization() {
        let client = MintClient::new("http://mint.example.com/").unwrap();
        assert_eq!(client.url(), "http://mint.example.com");
    }

    #[test]
    fn test_mint_client_url_no_trailing_slash() {
        let client = MintClient::new("http://mint.example.com").unwrap();
        assert_eq!(client.url(), "http://mint.example.com");
    }
}