// Copyright 2024 The NativeLink Authors. All rights reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//    http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use opentelemetry::metrics::Meter;

use tracing::info;

use crate::metrics_collection::{

    CollectedMetricChildren, CollectedMetricPrimitive, CollectedMetricPrimitiveValue,

    CollectedMetrics, RootMetricCollectedMetrics,

};

/// The maximum length of a metric name that otel supports.

/// Going beyond this limit causes otel to complain.

const MAX_METRIC_NAME_LENGTH: usize = 256;

/// Export the collected metrics to the OpenTelemetry meter.

pub fn otel_export(

    mut root_prefix: String,

    meter: &Meter,

    root_collected_metrics: &RootMetricCollectedMetrics,

) {

    if !root_prefix.is_empty() {

  Branch (33:8): [True: 0, False: 0]

  Branch (33:8): [Folded - Ignored]

        root_prefix.push('_');

    }

    process_children(&mut root_prefix, meter, root_collected_metrics);

}

fn process_children(prefix: &mut String, meter: &Meter, children: &CollectedMetricChildren) {

    for (name, child) in children {

        prefix.push_str(name);

        let mut added_prefix_len = name.len();

        match child {

            CollectedMetrics::Primitive(primitive) => {

                process_primitive(prefix, meter, primitive);

            }

            CollectedMetrics::Component(component) => {

                prefix.push('_');

                added_prefix_len += 1;

                process_children(prefix, meter, component);

            }

        }

        prefix.truncate(prefix.len() - added_prefix_len);

    }

}

fn process_primitive(prefix: &mut String, meter: &Meter, primitive: &CollectedMetricPrimitive) {

    match &primitive.value {

        Some(CollectedMetricPrimitiveValue::Counter(value)) => {

            if prefix.len() > MAX_METRIC_NAME_LENGTH {

  Branch (60:16): [True: 0, False: 0]

  Branch (60:16): [Folded - Ignored]

                info!("Metric name longer than 256 characters: {}", prefix);

                return;

            }

            let counter = meter

                .u64_counter(prefix.clone())

                .with_description(primitive.help.clone())

                .build();

            counter.add(*value, &[]);

        }

        Some(CollectedMetricPrimitiveValue::String(_value)) => {

            // We don't publish strings in metrics.

        }

        None => {}

    }

}