use std::{
    io,
    sync::{Arc, Mutex},
};

use crank_observability::{
    ObservabilityConfig, RedactionLimits, ServiceIdentity, build_subscriber, safe_json,
};
use serde_json::Value;
use time::{OffsetDateTime, format_description::well_known::Rfc3339};
use tracing_subscriber::fmt::MakeWriter;

#[derive(Clone, Default)]
struct SharedWriter {
    buffer: Arc<Mutex<Vec<u8>>>,
}

impl SharedWriter {
    fn output(&self) -> String {
        String::from_utf8(self.buffer.lock().expect("test writer lock").clone())
            .expect("log output must be UTF-8")
    }
}

impl<'a> MakeWriter<'a> for SharedWriter {
    type Writer = SharedWriterGuard;

    fn make_writer(&'a self) -> Self::Writer {
        SharedWriterGuard {
            buffer: Arc::clone(&self.buffer),
        }
    }
}

struct SharedWriterGuard {
    buffer: Arc<Mutex<Vec<u8>>>,
}

impl io::Write for SharedWriterGuard {
    fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
        self.buffer
            .lock()
            .map_err(|_| io::Error::other("test writer lock poisoned"))?
            .extend_from_slice(bytes);
        Ok(bytes.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

fn capture(service: &'static str, emit: impl FnOnce()) -> Vec<Value> {
    capture_with_limits(service, RedactionLimits::default(), emit)
}

fn capture_with_limits(
    service: &'static str,
    limits: RedactionLimits,
    emit: impl FnOnce(),
) -> Vec<Value> {
    let writer = SharedWriter::default();
    let config = ObservabilityConfig::new(
        ServiceIdentity::try_new(service, "0.3.1", "test").expect("valid test identity"),
        "info",
        limits,
    );
    let subscriber =
        build_subscriber(config, writer.clone()).expect("test subscriber must be built");

    tracing::subscriber::with_default(subscriber, emit);

    writer
        .output()
        .lines()
        .map(|line| {
            assert!(!line.contains('\u{1b}'), "ANSI is forbidden: {line}");
            serde_json::from_str(line).expect("every line must be one JSON object")
        })
        .collect()
}

#[test]
fn schema_contract_is_identical_for_both_services() {
    let outputs = ["admin-api", "mcp-server"].map(|service| {
        capture(service, || {
            tracing::info!(
                name: "service.started",
                target: "crank::startup",
                port = 3101_u64,
                "service started"
            );
        })
    });

    for (service, events) in ["admin-api", "mcp-server"].into_iter().zip(outputs.iter()) {
        assert_eq!(events.len(), 1);
        let event = &events[0];
        assert_eq!(event["service"], service);
        assert_eq!(event["version"], "0.3.1");
        assert_eq!(event["environment"], "test");
        assert_eq!(event["level"], "INFO");
        assert_eq!(event["target"], "crank::startup");
        assert_eq!(event["event"], "service.started");
        assert!(event["fields"].is_object());
        assert_eq!(event["fields"]["port"], 3101);
        assert_eq!(event["fields"]["message"], "service started");
        let timestamp = event["timestamp"].as_str().expect("timestamp string");
        let parsed =
            OffsetDateTime::parse(timestamp, &Rfc3339).expect("timestamp must be RFC 3339");
        assert_eq!(parsed.offset(), time::UtcOffset::UTC);
    }

    let first_keys: Vec<_> = outputs[0][0]
        .as_object()
        .expect("object")
        .keys()
        .cloned()
        .collect();
    let second_keys: Vec<_> = outputs[1][0]
        .as_object()
        .expect("object")
        .keys()
        .cloned()
        .collect();
    assert_eq!(first_keys, second_keys);
}

#[test]
fn correlation_fields_are_distinct_and_only_present_when_recorded() {
    let present = capture("admin-api", || {
        tracing::info!(
            name: "admin.request.completed",
            request_id = "req-123",
            trace_id = "0af7651916cd43dd8448eb211c80319c"
        );
    });
    assert_eq!(present[0]["request_id"], "req-123");
    assert_eq!(present[0]["trace_id"], "0af7651916cd43dd8448eb211c80319c");
    assert!(present[0]["fields"].get("request_id").is_none());
    assert!(present[0]["fields"].get("trace_id").is_none());

    let absent = capture("mcp-server", || {
        tracing::info!(name: "mcp.request.completed", status = 200_u64);
    });
    assert!(absent[0].get("request_id").is_none());
    assert!(absent[0].get("trace_id").is_none());
}

#[test]
fn correlation_fields_accept_valid_strings_and_reject_non_string_values() {
    let limits = RedactionLimits {
        max_object_fields: 1,
        ..RedactionLimits::default()
    };
    let request_id = "123";
    let events = capture_with_limits("admin-api", limits, || {
        tracing::info!(
            name: "admin.request.completed",
            alpha = "field that consumes the object budget",
            request_id = %request_id,
            trace_id = true,
        );
    });

    assert_eq!(events[0]["request_id"], "123");
    assert!(events[0].get("trace_id").is_none());
}

#[test]
fn empty_correlation_fields_are_omitted() {
    let events = capture("admin-api", || {
        tracing::info!(
            name: "admin.request.completed",
            request_id = "",
            trace_id = ""
        );
    });

    assert!(events[0].get("request_id").is_none());
    assert!(events[0].get("trace_id").is_none());
}

#[test]
fn formatter_redacts_fields_before_serialization() {
    let context = safe_json(
        &serde_json::json!({
            "nested": {
                "access_token": "nested-canary-secret",
                "endpoint": "https://example.test/private?key=nested-canary-secret"
            }
        }),
        RedactionLimits::default(),
    )
    .expect("safe nested context");
    let events = capture("admin-api", || {
        tracing::warn!(
            name: "admin.request.rejected",
            password = "canary-secret",
            url = "https://example.test/path?token=canary-secret",
            safe_fields = %context,
            unsafe_context = ?serde_json::json!({"password": "debug-canary-secret"}),
            error_code = "invalid_request"
        );
    });
    let serialized = serde_json::to_string(&events[0]).expect("event JSON");

    assert_eq!(events[0]["fields"]["password"], "[REDACTED]");
    assert_eq!(events[0]["fields"]["url"], "https://example.test/path");
    assert_eq!(
        events[0]["fields"]["safe_fields"]["nested"]["access_token"],
        "[REDACTED]"
    );
    assert_eq!(
        events[0]["fields"]["safe_fields"]["nested"]["endpoint"],
        "https://example.test/private"
    );
    assert_eq!(events[0]["fields"]["unsafe_context"], "[REDACTED]");
    assert_eq!(events[0]["fields"]["error_code"], "invalid_request");
    assert!(!serialized.contains("canary-secret"));
}

#[test]
fn arbitrary_debug_text_is_never_written_verbatim() {
    struct Credentials;

    impl std::fmt::Debug for Credentials {
        fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            formatter.write_str("Credentials { password: \"debug-canary-secret\" }")
        }
    }

    let events = capture("admin-api", || {
        tracing::warn!(
            name: "admin.debug.inspected",
            details = ?Credentials
        );
    });
    let serialized = serde_json::to_string(&events[0]).expect("event JSON");

    assert_eq!(events[0]["fields"]["details"], "[REDACTED]");
    assert!(!serialized.contains("debug-canary-secret"));
}

#[test]
fn compound_sensitive_event_fields_are_redacted() {
    let events = capture("admin-api", || {
        tracing::warn!(
            name: "admin.request.rejected",
            client_api_key = "client-canary-secret",
            authorization_header = "Bearer auth-canary-secret",
            response_body = "response-canary-secret",
            tool_arguments = "argument-canary-secret",
            query_params = "query-canary-secret",
        );
    });
    let serialized = serde_json::to_string(&events[0]).expect("event JSON");

    for key in [
        "client_api_key",
        "authorization_header",
        "response_body",
        "tool_arguments",
        "query_params",
    ] {
        assert_eq!(events[0]["fields"][key], "[REDACTED]");
    }
    assert!(!serialized.contains("canary-secret"));
}

#[test]
fn oversized_event_falls_back_to_valid_bounded_json() {
    let limits = RedactionLimits {
        max_event_bytes: 512,
        ..RedactionLimits::default()
    };
    let events = capture_with_limits("admin-api", limits, || {
        tracing::info!(
            name: "admin.payload.inspected",
            description = %"x".repeat(1024)
        );
    });
    let serialized = serde_json::to_vec(&events[0]).expect("bounded event JSON");

    assert!(serialized.len() < limits.max_event_bytes);
    assert_eq!(events[0]["fields"]["truncated"], true);
}

#[test]
fn safe_json_honours_the_total_event_budget() {
    let limits = RedactionLimits {
        max_event_bytes: 512,
        ..RedactionLimits::default()
    };

    let serialized = safe_json(
        &serde_json::json!({"description": "x".repeat(4096)}),
        limits,
    )
    .expect("safe JSON must remain serializable");

    assert!(serialized.len() <= limits.max_event_bytes);
    assert_eq!(
        serde_json::from_str::<Value>(&serialized).expect("valid JSON")["truncated"],
        true
    );
}

#[test]
fn subscriber_rejects_limits_that_cannot_hold_an_event() {
    let config = ObservabilityConfig::new(
        ServiceIdentity::try_new("admin-api", "0.3.1", "test").expect("valid identity"),
        "info",
        RedactionLimits {
            max_event_bytes: 16,
            ..RedactionLimits::default()
        },
    );

    assert!(build_subscriber(config, SharedWriter::default()).is_err());
}

#[test]
fn event_budget_rejects_maximum_identity_labels_when_correlation_cannot_fit() {
    let writer = SharedWriter::default();
    let config = ObservabilityConfig::new(
        ServiceIdentity::try_new("s".repeat(64), "v".repeat(64), "e".repeat(64))
            .expect("maximum identity labels are valid"),
        "info",
        RedactionLimits {
            max_event_bytes: 512,
            ..RedactionLimits::default()
        },
    );
    assert!(build_subscriber(config, writer).is_err());
}

#[test]
fn env_filter_is_applied_and_invalid_filter_is_safe() {
    let writer = SharedWriter::default();
    let config = ObservabilityConfig::new(
        ServiceIdentity::try_new("admin-api", "0.3.1", "test").expect("valid identity"),
        "warn",
        RedactionLimits::default(),
    );
    let subscriber =
        build_subscriber(config, writer.clone()).expect("test subscriber must be built");
    tracing::subscriber::with_default(subscriber, || {
        tracing::info!(name: "filtered.info", "filtered");
        tracing::warn!(name: "visible.warning", "visible");
    });
    let output = writer.output();

    assert!(!output.contains("filtered.info"));
    assert!(output.contains("visible.warning"));

    let invalid = ObservabilityConfig::new(
        ServiceIdentity::try_new("admin-api", "0.3.1", "test").expect("valid identity"),
        "[not a valid filter",
        RedactionLimits::default(),
    );
    let error = build_subscriber(invalid, SharedWriter::default())
        .err()
        .expect("invalid filter must fail");
    assert_eq!(error.to_string(), "invalid log filter");
    assert!(!error.to_string().contains("not a valid filter"));
}

#[test]
fn service_identity_rejects_empty_or_unsafe_labels() {
    for (service, version, environment) in [
        ("", "0.3.1", "test"),
        ("admin api", "0.3.1", "test"),
        ("admin-api", "", "test"),
        ("admin-api", "0.3.1", "prod\nsecret"),
    ] {
        assert!(ServiceIdentity::try_new(service, version, environment).is_err());
    }
}