// mcp-server — MCP server for Claude Code integration
//
// Speaks JSON-RPC over stdio. Exposes memory tools and channel
// operations. Replaces the Python MCP bridge entirely.
//
// Protocol: https://modelcontextprotocol.io/specification

use serde::{Deserialize, Serialize};
use serde_json::{json, Value};
use std::io::{self, BufRead, Write};

// ── JSON-RPC types ──────────────────────────────────────────────

#[derive(Deserialize)]
struct Request {
    jsonrpc: String,
    method: String,
    #[serde(default)]
    params: Value,
    id: Value,
}

#[derive(Serialize)]
struct Response {
    jsonrpc: String,
    result: Value,
    id: Value,
}

#[derive(Serialize)]
struct ErrorResponse {
    jsonrpc: String,
    error: Value,
    id: Value,
}

fn respond(id: Value, result: Value) {
    let resp = Response { jsonrpc: "2.0".into(), result, id };
    let json = serde_json::to_string(&resp).unwrap();
    let mut stdout = io::stdout().lock();
    let _ = writeln!(stdout, "{json}");
    let _ = stdout.flush();
}

fn respond_error(id: Value, code: i64, message: &str) {
    let resp = ErrorResponse {
        jsonrpc: "2.0".into(),
        error: json!({ "code": code, "message": message }),
        id,
    };
    let json = serde_json::to_string(&resp).unwrap();
    let mut stdout = io::stdout().lock();
    let _ = writeln!(stdout, "{json}");
    let _ = stdout.flush();
}

fn notify(method: &str, params: Value) {
    let json = serde_json::to_string(&json!({
        "jsonrpc": "2.0",
        "method": method,
        "params": params,
    })).unwrap();
    let mut stdout = io::stdout().lock();
    let _ = writeln!(stdout, "{json}");
    let _ = stdout.flush();
}

// ── Tool definitions ────────────────────────────────────────────

fn tool_definitions() -> Vec<Value> {
    poc_memory::agent::tools::tools().into_iter()
        .map(|t| json!({
            "name": t.def.function.name,
            "description": t.def.function.description,
            "inputSchema": t.def.function.parameters,
        }))
        .collect()
}

// ── Tool dispatch ───────────────────────────────────────────────

fn dispatch_tool(name: &str, args: &Value) -> Result<String, String> {
    let tools = poc_memory::agent::tools::tools();
    let tool = tools.iter().find(|t| t.def.function.name == name);
    let Some(tool) = tool else {
        return Err(format!("unknown tool: {name}"));
    };

    // Run async handler on a blocking runtime
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_all()
        .build()
        .map_err(|e| e.to_string())?;
    let local = tokio::task::LocalSet::new();
    local.block_on(&rt, (tool.handler)(None, args.clone()))
        .map_err(|e| e.to_string())
}

// ── Main loop ───────────────────────────────────────────────────

fn main() {
    let stdin = io::stdin();
    let reader = stdin.lock();

    for line in reader.lines() {
        let line = match line {
            Ok(l) if !l.is_empty() => l,
            _ => continue,
        };

        let req: Request = match serde_json::from_str(&line) {
            Ok(r) => r,
            Err(_) => continue,
        };

        match req.method.as_str() {
            "initialize" => {
                respond(req.id, json!({
                    "protocolVersion": "2024-11-05",
                    "capabilities": {
                        "tools": {}
                    },
                    "serverInfo": {
                        "name": "consciousness",
                        "version": "0.4.0"
                    }
                }));
            }

            "notifications/initialized" => {
                // Client ack — no response needed
            }

            "tools/list" => {
                let tools = tool_definitions();
                respond(req.id, json!({ "tools": tools }));
            }

            "tools/call" => {
                let name = req.params.get("name")
                    .and_then(|v| v.as_str())
                    .unwrap_or("");
                let args = req.params.get("arguments")
                    .cloned()
                    .unwrap_or(json!({}));

                match dispatch_tool(name, &args) {
                    Ok(text) => {
                        respond(req.id, json!({
                            "content": [{"type": "text", "text": text}]
                        }));
                    }
                    Err(e) => {
                        respond(req.id, json!({
                            "content": [{"type": "text", "text": e}],
                            "isError": true
                        }));
                    }
                }
            }

            _ => {
                respond_error(req.id, -32601, &format!("unknown method: {}", req.method));
            }
        }
    }
}