use crate::OtelConfig;
use opentelemetry::trace::TracerProvider;
use opentelemetry::{global, KeyValue};
use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;
use opentelemetry_otlp::WithExportConfig;
use opentelemetry_sdk::logs::SdkLoggerProvider;
use opentelemetry_sdk::{
    metrics::{MeterProviderBuilder, PeriodicReader, SdkMeterProvider},
    trace::{RandomIdGenerator, Sampler, SdkTracerProvider},
    Resource,
};
use opentelemetry_semantic_conventions::{
    attribute::{DEPLOYMENT_ENVIRONMENT_NAME, NETWORK_LOCAL_ADDRESS, SERVICE_VERSION as OTEL_SERVICE_VERSION},
    SCHEMA_URL,
};
use rustfs_config::{APP_NAME, DEFAULT_LOG_LEVEL, ENVIRONMENT, METER_INTERVAL, SAMPLE_RATIO, SERVICE_VERSION, USE_STDOUT};
use rustfs_utils::get_local_ip_with_default;
use smallvec::SmallVec;
use std::borrow::Cow;
use std::io::IsTerminal;
use tracing::info;
use tracing_error::ErrorLayer;
use tracing_opentelemetry::{MetricsLayer, OpenTelemetryLayer};
use tracing_subscriber::fmt::format::FmtSpan;
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter, Layer};

/// A guard object that manages the lifecycle of OpenTelemetry components.
///
/// This struct holds references to the created OpenTelemetry providers and ensures
/// they are properly shut down when the guard is dropped. It implements the RAII
/// (Resource Acquisition Is Initialization) pattern for managing telemetry resources.
///
/// When this guard goes out of scope, it will automatically shut down:
/// - The tracer provider (for distributed tracing)
/// - The meter provider (for metrics collection)
/// - The logger provider (for structured logging)
///
/// # Example
///
/// ```
/// use rustfs_obs::{init_telemetry, OtelConfig};
///
/// let config = OtelConfig::default();
/// let otel_guard = init_telemetry(&config);
///
/// // The guard is kept alive for the duration of the application
/// // When it's dropped, all telemetry components are properly shut down
/// drop(otel_guard);
/// ```
#[derive(Debug)]
pub struct OtelGuard {
    tracer_provider: SdkTracerProvider,
    meter_provider: SdkMeterProvider,
    logger_provider: SdkLoggerProvider,
}

impl Drop for OtelGuard {
    fn drop(&mut self) {
        if let Err(err) = self.tracer_provider.shutdown() {
            eprintln!("Tracer shutdown error: {:?}", err);
        }
        if let Err(err) = self.meter_provider.shutdown() {
            eprintln!("Meter shutdown error: {:?}", err);
        }
        if let Err(err) = self.logger_provider.shutdown() {
            eprintln!("Logger shutdown error: {:?}", err);
        }
    }
}

/// create OpenTelemetry Resource
fn resource(config: &OtelConfig) -> Resource {
    Resource::builder()
        .with_service_name(Cow::Borrowed(config.service_name.as_deref().unwrap_or(APP_NAME)).to_string())
        .with_schema_url(
            [
                KeyValue::new(
                    OTEL_SERVICE_VERSION,
                    Cow::Borrowed(config.service_version.as_deref().unwrap_or(SERVICE_VERSION)).to_string(),
                ),
                KeyValue::new(
                    DEPLOYMENT_ENVIRONMENT_NAME,
                    Cow::Borrowed(config.environment.as_deref().unwrap_or(ENVIRONMENT)).to_string(),
                ),
                KeyValue::new(NETWORK_LOCAL_ADDRESS, get_local_ip_with_default()),
            ],
            SCHEMA_URL,
        )
        .build()
}

/// Creates a periodic reader for stdout metrics
fn create_periodic_reader(interval: u64) -> PeriodicReader<opentelemetry_stdout::MetricExporter> {
    PeriodicReader::builder(opentelemetry_stdout::MetricExporter::default())
        .with_interval(std::time::Duration::from_secs(interval))
        .build()
}

/// Initialize Telemetry
pub fn init_telemetry(config: &OtelConfig) -> OtelGuard {
    // avoid repeated access to configuration fields
    let endpoint = &config.endpoint;
    let use_stdout = config.use_stdout.unwrap_or(USE_STDOUT);
    let meter_interval = config.meter_interval.unwrap_or(METER_INTERVAL);
    let logger_level = config.logger_level.as_deref().unwrap_or(DEFAULT_LOG_LEVEL);
    let service_name = config.service_name.as_deref().unwrap_or(APP_NAME);
    let environment = config.environment.as_deref().unwrap_or(ENVIRONMENT);

    // Pre-create resource objects to avoid repeated construction
    let res = resource(config);

    // initialize tracer provider
    let tracer_provider = {
        let sample_ratio = config.sample_ratio.unwrap_or(SAMPLE_RATIO);
        let sampler = if sample_ratio > 0.0 && sample_ratio < 1.0 {
            Sampler::TraceIdRatioBased(sample_ratio)
        } else {
            Sampler::AlwaysOn
        };

        let builder = SdkTracerProvider::builder()
            .with_sampler(sampler)
            .with_id_generator(RandomIdGenerator::default())
            .with_resource(res.clone());

        let tracer_provider = if endpoint.is_empty() {
            builder
                .with_batch_exporter(opentelemetry_stdout::SpanExporter::default())
                .build()
        } else {
            let exporter = opentelemetry_otlp::SpanExporter::builder()
                .with_tonic()
                .with_endpoint(endpoint)
                .build()
                .unwrap();

            let builder = if use_stdout {
                builder
                    .with_batch_exporter(exporter)
                    .with_batch_exporter(opentelemetry_stdout::SpanExporter::default())
            } else {
                builder.with_batch_exporter(exporter)
            };

            builder.build()
        };

        global::set_tracer_provider(tracer_provider.clone());
        tracer_provider
    };

    // initialize meter provider
    let meter_provider = {
        let mut builder = MeterProviderBuilder::default().with_resource(res.clone());

        if endpoint.is_empty() {
            builder = builder.with_reader(create_periodic_reader(meter_interval));
        } else {
            let exporter = opentelemetry_otlp::MetricExporter::builder()
                .with_tonic()
                .with_endpoint(endpoint)
                .with_temporality(opentelemetry_sdk::metrics::Temporality::default())
                .build()
                .unwrap();

            builder = builder.with_reader(
                PeriodicReader::builder(exporter)
                    .with_interval(std::time::Duration::from_secs(meter_interval))
                    .build(),
            );

            if use_stdout {
                builder = builder.with_reader(create_periodic_reader(meter_interval));
            }
        }

        let meter_provider = builder.build();
        global::set_meter_provider(meter_provider.clone());
        meter_provider
    };

    // initialize logger provider
    let logger_provider = {
        let mut builder = SdkLoggerProvider::builder().with_resource(res);

        if endpoint.is_empty() {
            builder = builder.with_batch_exporter(opentelemetry_stdout::LogExporter::default());
        } else {
            let exporter = opentelemetry_otlp::LogExporter::builder()
                .with_tonic()
                .with_endpoint(endpoint)
                .build()
                .unwrap();

            builder = builder.with_batch_exporter(exporter);

            if use_stdout {
                builder = builder.with_batch_exporter(opentelemetry_stdout::LogExporter::default());
            }
        }

        builder.build()
    };

    // configuring tracing
    {
        // configure the formatting layer
        let fmt_layer = {
            let enable_color = std::io::stdout().is_terminal();
            let mut layer = tracing_subscriber::fmt::layer()
                .with_target(true)
                .with_ansi(enable_color)
                .with_thread_names(true)
                .with_thread_ids(true)
                .with_file(true)
                .with_line_number(true);

            // Only add full span events tracking in the development environment
            if environment != ENVIRONMENT {
                layer = layer.with_span_events(FmtSpan::FULL);
            }

            layer.with_filter(build_env_filter(logger_level, None))
        };

        let filter = build_env_filter(logger_level, None);
        let otel_filter = build_env_filter(logger_level, None);
        let otel_layer = OpenTelemetryTracingBridge::new(&logger_provider).with_filter(otel_filter);
        let tracer = tracer_provider.tracer(Cow::Borrowed(service_name).to_string());

        // Configure registry to avoid repeated calls to filter methods
        tracing_subscriber::registry()
            .with(filter)
            .with(ErrorLayer::default())
            .with(if config.local_logging_enabled.unwrap_or(false) {
                Some(fmt_layer)
            } else {
                None
            })
            .with(OpenTelemetryLayer::new(tracer))
            .with(otel_layer)
            .with(MetricsLayer::new(meter_provider.clone()))
            .init();

        if !endpoint.is_empty() {
            info!(
                "OpenTelemetry telemetry initialized with OTLP endpoint: {}, logger_level: {},RUST_LOG env: {}",
                endpoint,
                logger_level,
                std::env::var("RUST_LOG").unwrap_or_else(|_| "Not set".to_string())
            );
        }
    }

    OtelGuard {
        tracer_provider,
        meter_provider,
        logger_provider,
    }
}

fn build_env_filter(logger_level: &str, default_level: Option<&str>) -> EnvFilter {
    let level = default_level.unwrap_or(logger_level);
    let mut filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new(level));
    if !matches!(logger_level, "trace" | "debug") {
        let directives: SmallVec<[&str; 5]> = smallvec::smallvec!["hyper", "tonic", "h2", "reqwest", "tower"];
        for directive in directives {
            filter = filter.add_directive(format!("{}=off", directive).parse().unwrap());
        }
    }

    filter
}