use std::sync::Arc;

use async_graphql_parser::types::ExecutableDocument;
use async_graphql_value::Variables;
use futures_util::stream::BoxStream;
use futures_util::TryFutureExt;
use opentelemetry::trace::{FutureExt, SpanKind, TraceContextExt, Tracer};
use opentelemetry::{Context as OpenTelemetryContext, Key};

use crate::extensions::{
    Extension, ExtensionContext, ExtensionFactory, NextExtension, ResolveInfo,
};
use crate::{Response, ServerError, ServerResult, ValidationResult, Value};

const KEY_SOURCE: Key = Key::from_static_str("graphql.source");
const KEY_VARIABLES: Key = Key::from_static_str("graphql.variables");
const KEY_PARENT_TYPE: Key = Key::from_static_str("graphql.parentType");
const KEY_RETURN_TYPE: Key = Key::from_static_str("graphql.returnType");
const KEY_ERROR: Key = Key::from_static_str("graphql.error");
const KEY_COMPLEXITY: Key = Key::from_static_str("graphql.complexity");
const KEY_DEPTH: Key = Key::from_static_str("graphql.depth");

/// OpenTelemetry extension
#[cfg_attr(docsrs, doc(cfg(feature = "opentelemetry")))]
pub struct OpenTelemetry<T> {
    tracer: Arc<T>,
}

impl<T> OpenTelemetry<T> {
    /// Use `tracer` to create an OpenTelemetry extension.
    pub fn new(tracer: T) -> OpenTelemetry<T>
    where
        T: Tracer + Send + Sync,
    {
        Self {
            tracer: Arc::new(tracer),
        }
    }
}

impl<T: Tracer + Send + Sync> ExtensionFactory for OpenTelemetry<T> {
    fn create(&self) -> Arc<dyn Extension> {
        Arc::new(OpenTelemetryExtension {
            tracer: self.tracer.clone(),
        })
    }
}

struct OpenTelemetryExtension<T> {
    tracer: Arc<T>,
}

#[async_trait::async_trait]
impl<T: Tracer + Send + Sync> Extension for OpenTelemetryExtension<T> {
    async fn request(&self, ctx: &ExtensionContext<'_>, next: NextExtension<'_>) -> Response {
        next.request(ctx)
            .with_context(OpenTelemetryContext::current_with_span(
                self.tracer
                    .span_builder("request")
                    .with_kind(SpanKind::Server)
                    .start(&*self.tracer),
            ))
            .await
    }

    fn subscribe<'s>(
        &self,
        ctx: &ExtensionContext<'_>,
        stream: BoxStream<'s, Response>,
        next: NextExtension<'_>,
    ) -> BoxStream<'s, Response> {
        Box::pin(
            next.subscribe(ctx, stream)
                .with_context(OpenTelemetryContext::current_with_span(
                    self.tracer
                        .span_builder("subscribe")
                        .with_kind(SpanKind::Server)
                        .start(&*self.tracer),
                )),
        )
    }

    async fn parse_query(
        &self,
        ctx: &ExtensionContext<'_>,
        query: &str,
        variables: &Variables,
        next: NextExtension<'_>,
    ) -> ServerResult<ExecutableDocument> {
        let attributes = vec![
            KEY_SOURCE.string(query.to_string()),
            KEY_VARIABLES.string(serde_json::to_string(variables).unwrap()),
        ];
        let span = self
            .tracer
            .span_builder("parse")
            .with_kind(SpanKind::Server)
            .with_attributes(attributes)
            .start(&*self.tracer);
        next.parse_query(ctx, query, variables)
            .with_context(OpenTelemetryContext::current_with_span(span))
            .await
    }

    async fn validation(
        &self,
        ctx: &ExtensionContext<'_>,
        next: NextExtension<'_>,
    ) -> Result<ValidationResult, Vec<ServerError>> {
        let span = self
            .tracer
            .span_builder("validation")
            .with_kind(SpanKind::Server)
            .start(&*self.tracer);
        next.validation(ctx)
            .with_context(OpenTelemetryContext::current_with_span(span))
            .map_ok(|res| {
                let current_cx = OpenTelemetryContext::current();
                let span = current_cx.span();
                span.set_attribute(KEY_COMPLEXITY.i64(res.complexity as i64));
                span.set_attribute(KEY_DEPTH.i64(res.depth as i64));
                res
            })
            .await
    }

    async fn execute(&self, ctx: &ExtensionContext<'_>, next: NextExtension<'_>) -> Response {
        let span = self
            .tracer
            .span_builder("execute")
            .with_kind(SpanKind::Server)
            .start(&*self.tracer);
        next.execute(ctx)
            .with_context(OpenTelemetryContext::current_with_span(span))
            .await
    }

    async fn resolve(
        &self,
        ctx: &ExtensionContext<'_>,
        info: ResolveInfo<'_>,
        next: NextExtension<'_>,
    ) -> ServerResult<Option<Value>> {
        let attributes = vec![
            KEY_PARENT_TYPE.string(info.parent_type.to_string()),
            KEY_RETURN_TYPE.string(info.return_type.to_string()),
        ];
        let span = self
            .tracer
            .span_builder(&info.path_node.to_string())
            .with_kind(SpanKind::Server)
            .with_attributes(attributes)
            .start(&*self.tracer);
        next.resolve(ctx, info)
            .with_context(OpenTelemetryContext::current_with_span(span))
            .map_err(|err| {
                let current_cx = OpenTelemetryContext::current();
                current_cx
                    .span()
                    .add_event("error".to_string(), vec![KEY_ERROR.string(err.to_string())]);
                err
            })
            .await
    }
}