/*
 * Copyright The OpenTelemetry Authors
 *
 * 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
 *
 *      https://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.
 */

import { diag } from '@opentelemetry/api';
import { getNumberFromEnv, getStringFromEnv } from '@opentelemetry/core';
import { Sampler } from './Sampler';
import { AlwaysOffSampler } from './sampler/AlwaysOffSampler';
import { AlwaysOnSampler } from './sampler/AlwaysOnSampler';
import { ParentBasedSampler } from './sampler/ParentBasedSampler';
import { TraceIdRatioBasedSampler } from './sampler/TraceIdRatioBasedSampler';

const enum TracesSamplerValues {
  AlwaysOff = 'always_off',
  AlwaysOn = 'always_on',
  ParentBasedAlwaysOff = 'parentbased_always_off',
  ParentBasedAlwaysOn = 'parentbased_always_on',
  ParentBasedTraceIdRatio = 'parentbased_traceidratio',
  TraceIdRatio = 'traceidratio',
}

const DEFAULT_RATIO = 1;

/**
 * Load default configuration. For fields with primitive values, any user-provided
 * value will override the corresponding default value. For fields with
 * non-primitive values (like `spanLimits`), the user-provided value will be
 * used to extend the default value.
 */

// object needs to be wrapped in this function and called when needed otherwise
// envs are parsed before tests are ran - causes tests using these envs to fail
export function loadDefaultConfig() {
  return {
    sampler: buildSamplerFromEnv(),
    forceFlushTimeoutMillis: 30000,
    generalLimits: {
      attributeValueLengthLimit:
        getNumberFromEnv('OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT') ?? Infinity,
      attributeCountLimit:
        getNumberFromEnv('OTEL_ATTRIBUTE_COUNT_LIMIT') ?? 128,
    },
    spanLimits: {
      attributeValueLengthLimit:
        getNumberFromEnv('OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT') ?? Infinity,
      attributeCountLimit:
        getNumberFromEnv('OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT') ?? 128,
      linkCountLimit: getNumberFromEnv('OTEL_SPAN_LINK_COUNT_LIMIT') ?? 128,
      eventCountLimit: getNumberFromEnv('OTEL_SPAN_EVENT_COUNT_LIMIT') ?? 128,
      attributePerEventCountLimit:
        getNumberFromEnv('OTEL_SPAN_ATTRIBUTE_PER_EVENT_COUNT_LIMIT') ?? 128,
      attributePerLinkCountLimit:
        getNumberFromEnv('OTEL_SPAN_ATTRIBUTE_PER_LINK_COUNT_LIMIT') ?? 128,
    },
  };
}

/**
 * Based on environment, builds a sampler, complies with specification.
 */
export function buildSamplerFromEnv(): Sampler {
  const sampler =
    getStringFromEnv('OTEL_TRACES_SAMPLER') ??
    TracesSamplerValues.ParentBasedAlwaysOn;
  switch (sampler) {
    case TracesSamplerValues.AlwaysOn:
      return new AlwaysOnSampler();
    case TracesSamplerValues.AlwaysOff:
      return new AlwaysOffSampler();
    case TracesSamplerValues.ParentBasedAlwaysOn:
      return new ParentBasedSampler({
        root: new AlwaysOnSampler(),
      });
    case TracesSamplerValues.ParentBasedAlwaysOff:
      return new ParentBasedSampler({
        root: new AlwaysOffSampler(),
      });
    case TracesSamplerValues.TraceIdRatio:
      return new TraceIdRatioBasedSampler(getSamplerProbabilityFromEnv());
    case TracesSamplerValues.ParentBasedTraceIdRatio:
      return new ParentBasedSampler({
        root: new TraceIdRatioBasedSampler(getSamplerProbabilityFromEnv()),
      });
    default:
      diag.error(
        `OTEL_TRACES_SAMPLER value "${sampler}" invalid, defaulting to "${TracesSamplerValues.ParentBasedAlwaysOn}".`
      );
      return new ParentBasedSampler({
        root: new AlwaysOnSampler(),
      });
  }
}

function getSamplerProbabilityFromEnv(): number | undefined {
  const probability = getNumberFromEnv('OTEL_TRACES_SAMPLER_ARG');
  if (probability == null) {
    diag.error(
      `OTEL_TRACES_SAMPLER_ARG is blank, defaulting to ${DEFAULT_RATIO}.`
    );
    return DEFAULT_RATIO;
  }

  if (probability < 0 || probability > 1) {
    diag.error(
      `OTEL_TRACES_SAMPLER_ARG=${probability} was given, but it is out of range ([0..1]), defaulting to ${DEFAULT_RATIO}.`
    );
    return DEFAULT_RATIO;
  }

  return probability;
}