// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package telemetry // import "go.opentelemetry.io/collector/service/telemetry"

import (
	"fmt"
	"net"
	"strconv"
	"time"

	"go.opentelemetry.io/contrib/config"
	"go.uber.org/zap/zapcore"

	"go.opentelemetry.io/collector/config/configtelemetry"
	"go.opentelemetry.io/collector/confmap"
	"go.opentelemetry.io/collector/featuregate"
)

var _ confmap.Unmarshaler = (*Config)(nil)

var disableAddressFieldForInternalTelemetryFeatureGate = featuregate.GlobalRegistry().MustRegister(
	"telemetry.disableAddressFieldForInternalTelemetry",
	featuregate.StageAlpha,
	featuregate.WithRegisterFromVersion("v0.111.0"),
	featuregate.WithRegisterToVersion("v0.114.0"),
	featuregate.WithRegisterDescription("controls whether the deprecated address field for internal telemetry is still supported"))

// Config defines the configurable settings for service telemetry.
type Config struct {
	Logs    LogsConfig    `mapstructure:"logs"`
	Metrics MetricsConfig `mapstructure:"metrics"`
	Traces  TracesConfig  `mapstructure:"traces"`

	// Resource specifies user-defined attributes to include with all emitted telemetry.
	// Note that some attributes are added automatically (e.g. service.version) even
	// if they are not specified here. In order to suppress such attributes the
	// attribute must be specified in this map with null YAML value (nil string pointer).
	Resource map[string]*string `mapstructure:"resource"`
}

// LogsConfig defines the configurable settings for service telemetry logs.
// This MUST be compatible with zap.Config. Cannot use directly zap.Config because
// the collector uses mapstructure and not yaml tags.
type LogsConfig struct {
	// Level is the minimum enabled logging level.
	// (default = "INFO")
	Level zapcore.Level `mapstructure:"level"`

	// Development puts the logger in development mode, which changes the
	// behavior of DPanicLevel and takes stacktraces more liberally.
	// (default = false)
	Development bool `mapstructure:"development"`

	// Encoding sets the logger's encoding.
	// Example values are "json", "console".
	Encoding string `mapstructure:"encoding"`

	// DisableCaller stops annotating logs with the calling function's file
	// name and line number. By default, all logs are annotated.
	// (default = false)
	DisableCaller bool `mapstructure:"disable_caller"`

	// DisableStacktrace completely disables automatic stacktrace capturing. By
	// default, stacktraces are captured for WarnLevel and above logs in
	// development and ErrorLevel and above in production.
	// (default = false)
	DisableStacktrace bool `mapstructure:"disable_stacktrace"`

	// Sampling sets a sampling policy.
	// Default:
	// 		sampling:
	//	   		enabled: true
	//	   		tick: 10s
	//	   		initial: 10
	//	   		thereafter: 100
	// Sampling can be disabled by setting 'enabled' to false
	Sampling *LogsSamplingConfig `mapstructure:"sampling"`

	// OutputPaths is a list of URLs or file paths to write logging output to.
	// The URLs could only be with "file" schema or without schema.
	// The URLs with "file" schema must be an absolute path.
	// The URLs without schema are treated as local file paths.
	// "stdout" and "stderr" are interpreted as os.Stdout and os.Stderr.
	// see details at Open in zap/writer.go.
	// (default = ["stderr"])
	OutputPaths []string `mapstructure:"output_paths"`

	// ErrorOutputPaths is a list of URLs or file paths to write zap internal logger errors to.
	// The URLs could only be with "file" schema or without schema.
	// The URLs with "file" schema must use absolute paths.
	// The URLs without schema are treated as local file paths.
	// "stdout" and "stderr" are interpreted as os.Stdout and os.Stderr.
	// see details at Open in zap/writer.go.
	//
	// Note that this setting only affects the zap internal logger errors.
	// (default = ["stderr"])
	ErrorOutputPaths []string `mapstructure:"error_output_paths"`

	// InitialFields is a collection of fields to add to the root logger.
	// Example:
	//
	// 		initial_fields:
	//	   		foo: "bar"
	//
	// By default, there is no initial field.
	InitialFields map[string]any `mapstructure:"initial_fields"`
}

// LogsSamplingConfig sets a sampling strategy for the logger. Sampling caps the
// global CPU and I/O load that logging puts on your process while attempting
// to preserve a representative subset of your logs.
type LogsSamplingConfig struct {
	// Enabled enable sampling logging
	Enabled bool `mapstructure:"enabled"`
	// Tick represents the interval in seconds that the logger apply each sampling.
	Tick time.Duration `mapstructure:"tick"`
	// Initial represents the first M messages logged each Tick.
	Initial int `mapstructure:"initial"`
	// Thereafter represents the sampling rate, every Nth message will be sampled after Initial messages are logged during each Tick.
	// If Thereafter is zero, the logger will drop all the messages after the Initial each Tick.
	Thereafter int `mapstructure:"thereafter"`
}

// MetricsConfig exposes the common Telemetry configuration for one component.
// Experimental: *NOTE* this structure is subject to change or removal in the future.
type MetricsConfig struct {
	// Level is the level of telemetry metrics, the possible values are:
	//  - "none" indicates that no telemetry data should be collected;
	//  - "basic" is the recommended and covers the basics of the service telemetry.
	//  - "normal" adds some other indicators on top of basic.
	//  - "detailed" adds dimensions and views to the previous levels.
	Level configtelemetry.Level `mapstructure:"level"`

	// Deprecated: [v0.111.0] use readers configuration.
	Address string `mapstructure:"address"`

	// Readers allow configuration of metric readers to emit metrics to
	// any number of supported backends.
	Readers []config.MetricReader `mapstructure:"readers"`
}

// TracesConfig exposes the common Telemetry configuration for collector's internal spans.
// Experimental: *NOTE* this structure is subject to change or removal in the future.
type TracesConfig struct {
	// Level configures whether spans are emitted or not, the possible values are:
	//  - "none" indicates that no tracing data should be collected;
	//  - "basic" is the recommended and covers the basics of the service telemetry.
	Level configtelemetry.Level `mapstructure:"level"`
	// Propagators is a list of TextMapPropagators from the supported propagators list. Currently,
	// tracecontext and  b3 are supported. By default, the value is set to empty list and
	// context propagation is disabled.
	Propagators []string `mapstructure:"propagators"`
	// Processors allow configuration of span processors to emit spans to
	// any number of supported backends.
	Processors []config.SpanProcessor `mapstructure:"processors"`
}

func (c *Config) Unmarshal(conf *confmap.Conf) error {
	if err := conf.Unmarshal(c); err != nil {
		return err
	}

	// If the support for "metrics::address" is disabled, nothing to do.
	// TODO: when this gate is marked stable remove the whole Unmarshal definition.
	if disableAddressFieldForInternalTelemetryFeatureGate.IsEnabled() {
		return nil
	}

	if len(c.Metrics.Address) != 0 {
		host, port, err := net.SplitHostPort(c.Metrics.Address)
		if err != nil {
			return fmt.Errorf("failing to parse metrics address %q: %w", c.Metrics.Address, err)
		}
		portInt, err := strconv.Atoi(port)
		if err != nil {
			return fmt.Errorf("failing to extract the port from the metrics address %q: %w", c.Metrics.Address, err)
		}

		// User did not overwrite readers, so we will remove the default configured reader.
		if !conf.IsSet("metrics::readers") {
			c.Metrics.Readers = nil
		}

		c.Metrics.Readers = append(c.Metrics.Readers, config.MetricReader{
			Pull: &config.PullMetricReader{
				Exporter: config.MetricExporter{
					Prometheus: &config.Prometheus{
						Host: &host,
						Port: &portInt,
					},
				},
			},
		})
	}

	return nil
}

// Validate checks whether the current configuration is valid
func (c *Config) Validate() error {
	// Check when service telemetry metric level is not none, the metrics readers should not be empty
	if c.Metrics.Level != configtelemetry.LevelNone && len(c.Metrics.Readers) == 0 {
		return fmt.Errorf("collector telemetry metrics reader should exist when metric level is not none")
	}

	return nil
}
