use std::io::{BufRead, BufReader, Write};
use std::process::{Child, Command, Stdio};

use tempfile::TempDir;

struct McpProcess {
    child: Child,
    reader: BufReader<std::process::ChildStdout>,
    _tmp: TempDir,
}

impl McpProcess {
    fn spawn() -> Self {
        let tmp = TempDir::new().expect("tempdir");
        let progress_path = tmp.path().join("progress.json");
        let mut child = Command::new(env!("CARGO_BIN_EXE_quantum-bridge-mcp"))
            .env("QB_PROGRESS_PATH", &progress_path)
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .stderr(Stdio::null())
            .spawn()
            .expect("spawn");
        let stdout = child.stdout.take().expect("take stdout");
        let reader = BufReader::new(stdout);
        Self { child, reader, _tmp: tmp }
    }

    fn send(&mut self, msg: &str) {
        let stdin = self.child.stdin.as_mut().unwrap();
        writeln!(stdin, "{msg}").unwrap();
        stdin.flush().unwrap();
    }

    fn recv(&mut self) -> serde_json::Value {
        let mut line = String::new();
        self.reader.read_line(&mut line).unwrap();
        serde_json::from_str(line.trim()).expect("response is JSON")
    }

    fn initialize(&mut self) {
        self.send(r#"{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"0.0.1"}}}"#);
        let _ = self.recv();
    }

    fn extract(resp: &serde_json::Value) -> serde_json::Value {
        let text = resp["result"]["content"][0]["text"].as_str().unwrap();
        serde_json::from_str(text).unwrap()
    }
}

impl Drop for McpProcess {
    fn drop(&mut self) {
        let _ = self.child.kill();
    }
}

#[test]
fn tools_list_exposes_seven_tools() {
    let mut p = McpProcess::spawn();
    p.initialize();
    p.send(r#"{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}"#);
    let resp = p.recv();
    let tools = resp["result"]["tools"].as_array().unwrap();
    assert_eq!(tools.len(), 7);
    let names: Vec<&str> = tools.iter().map(|t| t["name"].as_str().unwrap()).collect();
    for required in ["get_lesson", "check_exercise", "explain_result", "get_progress"] {
        assert!(names.contains(&required), "missing {required}");
    }
}

#[test]
fn check_exercise_persists_progress_in_sandbox() {
    let mut p = McpProcess::spawn();
    p.initialize();
    let circuit = "OPENQASM 3.0;\ninclude \"stdgates.inc\";\nqubit[1] q;\nbit[1] c;\nx q[0];\nc = measure q;";
    let call = serde_json::json!({
        "jsonrpc": "2.0", "id": 3, "method": "tools/call",
        "params": {"name": "check_exercise", "arguments": {"exercise_id": "1-1-a", "circuit": circuit}}
    });
    p.send(&call.to_string());
    let payload = McpProcess::extract(&p.recv());
    assert_eq!(payload["passed"], true);
    assert_eq!(payload["progress_updated"], true);

    p.send(r#"{"jsonrpc":"2.0","id":4,"method":"tools/call","params":{"name":"get_progress","arguments":{}}}"#);
    let progress = McpProcess::extract(&p.recv());
    assert!(progress["total_exercises_solved"].as_u64().unwrap() >= 1);
}

#[test]
fn check_exercise_invalid_circuit_returns_diagnostics_in_payload_not_protocol_error() {
    let mut p = McpProcess::spawn();
    p.initialize();
    p.send(r#"{"jsonrpc":"2.0","id":5,"method":"tools/call","params":{"name":"check_exercise","arguments":{"exercise_id":"1-1-a","circuit":"not valid qasm"}}}"#);
    let resp = p.recv();
    assert!(resp.get("error").is_none(), "expected payload not error: {resp}");
    let payload = McpProcess::extract(&resp);
    assert_eq!(payload["passed"], false);
    assert!(payload["diagnostics"].as_array().is_some());
}

#[test]
fn explain_result_returns_ast_based_breakdown_with_descriptions() {
    let mut p = McpProcess::spawn();
    p.initialize();
    let call = serde_json::json!({
        "jsonrpc": "2.0", "id": 6, "method": "tools/call",
        "params": {"name": "explain_result", "arguments": {
            "circuit": "OPENQASM 3.0;\ninclude \"stdgates.inc\";\nqubit[2] q;\nbit[2] c;\nh q[0];\ncx q[0], q[1];\nc = measure q;",
            "counts": {"00": 512, "11": 512}
        }}
    });
    p.send(&call.to_string());
    let payload = McpProcess::extract(&p.recv());
    assert_eq!(payload["key_concept"], "entanglement");
    assert_eq!(payload["num_qubits"], 2);
    let breakdown = payload["gate_breakdown"].as_array().unwrap();
    assert_eq!(breakdown.len(), 2);
    assert_eq!(breakdown[0]["name"], "h");
    assert_eq!(breakdown[1]["name"], "cx");
}

#[test]
fn golden_pass_cases_all_pass() {
    let golden = std::fs::read_to_string("tests/reference/tutor/exercises_pass.jsonl").unwrap();
    let mut p = McpProcess::spawn();
    p.initialize();
    for line in golden.lines().filter(|l| !l.trim().is_empty()) {
        let case: serde_json::Value = serde_json::from_str(line).unwrap();
        let id = case["exercise_id"].as_str().unwrap();
        let circuit = case["circuit"].as_str().unwrap();
        let call = serde_json::json!({
            "jsonrpc": "2.0", "id": 99, "method": "tools/call",
            "params": {"name": "check_exercise", "arguments": {"exercise_id": id, "circuit": circuit}}
        });
        p.send(&call.to_string());
        let payload = McpProcess::extract(&p.recv());
        assert!(payload["passed"].as_bool().unwrap_or(false), "id={id} payload={payload}");
    }
}

#[test]
fn golden_fail_cases_all_fail() {
    let golden = std::fs::read_to_string("tests/reference/tutor/exercises_fail.jsonl").unwrap();
    let mut p = McpProcess::spawn();
    p.initialize();
    for line in golden.lines().filter(|l| !l.trim().is_empty()) {
        let case: serde_json::Value = serde_json::from_str(line).unwrap();
        let id = case["exercise_id"].as_str().unwrap();
        let circuit = case["circuit"].as_str().unwrap();
        let call = serde_json::json!({
            "jsonrpc": "2.0", "id": 98, "method": "tools/call",
            "params": {"name": "check_exercise", "arguments": {"exercise_id": id, "circuit": circuit}}
        });
        p.send(&call.to_string());
        let payload = McpProcess::extract(&p.recv());
        assert_eq!(payload["passed"].as_bool().unwrap_or(true), false, "id={id} should fail");
    }
}