wanderbooks/crates/ledger-mcp/src/main.rs

//! `ledger-mcp`: the AI-first bookkeeping interface, over stdio.
//!
//! Usage: `ledger-mcp [--data-dir PATH] [--config PATH] [--books-toml PATH]`
//!
//! The data dir holds `journal.jsonl` (the source of truth), `wanderbooks.db`
//! (the disposable SQLite projection), `blobs/` (content-addressed receipts),
//! and optionally `config.json`. If no store exists, one is created with the
//! configured base currency. Company settings (name, fiscal year start,
//! receipt threshold) come from the books dir's `wanderbooks.toml`, by
//! default the one next to the data dir.

use ledger_config as company;
mod policy;
mod server;
mod types;

use ledger_core::Currency;
use ledger_store::Store;
use policy::ReceiptPolicy;
use rmcp::{ServiceExt, transport::stdio};
use serde::Deserialize;
use server::BooksServer;
use std::path::PathBuf;

/// Server configuration, JSON. All fields optional.
#[derive(Debug, Default, Deserialize)]
struct Config {
    /// ISO 4217 base currency for a new store. Default "USD".
    #[serde(default)]
    base_currency: Option<String>,
    /// Receipt policy. Overrides `wanderbooks.toml`'s receipt_threshold;
    /// with neither, receipts are required above $25.00.
    #[serde(default)]
    receipt_policy: Option<ReceiptPolicy>,
}

fn default_data_dir() -> PathBuf {
    let home = std::env::var("HOME").unwrap_or_else(|_| ".".to_string());
    PathBuf::from(home).join(".local/share/wanderbooks")
}

fn print_usage() {
    eprintln!(
        "usage: ledger-mcp [--data-dir PATH] [--config PATH] [--books-toml PATH] [--http ADDR]"
    );
    eprintln!("  --data-dir  directory holding journal.jsonl (default ~/.local/share/wanderbooks)");
    eprintln!("  --config    JSON config file (default <data-dir>/config.json, optional)");
    eprintln!(
        "  --books-toml  company settings (default <data-dir>/../wanderbooks.toml, optional)"
    );
    eprintln!(
        "  --http      serve over Streamable HTTP at ADDR (e.g. 127.0.0.1:8080) instead of stdio"
    );
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut data_dir = default_data_dir();
    let mut config_path: Option<PathBuf> = None;
    let mut books_toml: Option<PathBuf> = None;
    let mut http_addr: Option<String> = None;
    let mut args = std::env::args().skip(1);
    while let Some(arg) = args.next() {
        match arg.as_str() {
            "--data-dir" => {
                data_dir = PathBuf::from(args.next().ok_or("--data-dir needs a path")?);
            }
            "--config" => {
                config_path = Some(PathBuf::from(args.next().ok_or("--config needs a path")?));
            }
            "--books-toml" => {
                books_toml = Some(PathBuf::from(
                    args.next().ok_or("--books-toml needs a path")?,
                ));
            }
            "--http" => {
                http_addr = Some(args.next().ok_or("--http needs an address")?);
            }
            "--help" | "-h" => {
                print_usage();
                return Ok(());
            }
            other => {
                eprintln!("unknown argument: {other}");
                print_usage();
                std::process::exit(2);
            }
        }
    }
    let config_path = config_path.unwrap_or_else(|| data_dir.join("config.json"));
    let config: Config = if config_path.exists() {
        let raw = std::fs::read_to_string(&config_path)?;
        serde_json::from_str(&raw)
            .map_err(|e| format!("bad config {}: {e}", config_path.display()))?
    } else {
        Config::default()
    };
    // Logs go to stderr: stdout is the MCP channel.
    eprintln!("ledger-mcp: data dir {}", data_dir.display());
    // An explicit --books-toml must exist; the default is optional.
    let settings = match books_toml {
        Some(path) => company::load(&path)?,
        None => match data_dir.parent().map(|p| p.join("wanderbooks.toml")) {
            Some(path) if path.exists() => company::load(&path)?,
            _ => company::BooksSettings::default(),
        },
    };
    eprintln!("ledger-mcp: company {:?}", settings.company.name);
    let policy = match (config.receipt_policy, settings.receipt_threshold) {
        (Some(policy), _) => policy,
        (None, Some(threshold)) => ReceiptPolicy {
            require_receipts_above: threshold,
            ..ReceiptPolicy::default()
        },
        (None, None) => ReceiptPolicy::default(),
    };
    let company = settings.company;

    let mut store = if data_dir.join(ledger_store::JOURNAL_FILE).exists() {
        Store::open(&data_dir)?
    } else {
        let code = config.base_currency.as_deref().unwrap_or("USD");
        let currency = Currency::new(code).map_err(|_| format!("bad base currency {code:?}"))?;
        eprintln!("ledger-mcp: creating new store (base currency {code})");
        Store::create(&data_dir, currency)?
    };
    // The journal is the source of truth: verify the chain, the replay, and
    // the whole projection before serving a single tool call, rebuilding
    // the projection if it drifted.
    let report = store
        .verify_and_heal()
        .map_err(|e| format!("store verify failed: {e}"))?;
    if let Some(why) = &report.healed {
        eprintln!("ledger-mcp: rebuilt the database from the journal ({why})");
    }

    let rt = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()?;
    if let Some(addr) = http_addr {
        eprintln!("ledger-mcp: store verified, serving Streamable HTTP on {addr}");
        rt.block_on(serve_http(addr, store, policy, company))?;
        return Ok(());
    }

    eprintln!("ledger-mcp: store verified, serving over stdio");
    let server = BooksServer::new(store, policy).with_company(company);
    rt.block_on(async {
        let running = server.serve(stdio()).await?;
        let _ = running.waiting().await;
        Ok::<(), Box<dyn std::error::Error>>(())
    })
}

/// Serve MCP over Streamable HTTP (for network clients).
async fn serve_http(
    addr: String,
    store: Store,
    policy: ReceiptPolicy,
    company: company::Company,
) -> Result<(), Box<dyn std::error::Error>> {
    use rmcp::transport::streamable_http_server::{
        StreamableHttpService, session::local::LocalSessionManager,
    };
    use std::sync::Arc;

    let store = Arc::new(std::sync::Mutex::new(store));
    let service = StreamableHttpService::new(
        move || {
            let server = server::BooksServer::new_shared(store.clone(), policy.clone())
                .with_company(company.clone());
            Ok(server)
        },
        Arc::new(LocalSessionManager::default()),
        Default::default(),
    );

    let router = axum::Router::new().nest_service("/mcp", service);
    let listener = tokio::net::TcpListener::bind(&addr).await?;
    eprintln!("ledger-mcp: listening on http://{addr}/mcp");
    axum::serve(listener, router).await?;
    Ok(())
}