package attr

import (
	"encoding/json"
	"os"
	"runtime"
	"runtime/debug"

	"git.ma-al.com/gora_filip/pkg/level"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/semconv/v1.25.0"
	"go.opentelemetry.io/otel/trace"
)

type IntoTraceAttribute interface {
	IntoTraceAttribute() attribute.KeyValue
}

type IntoTraceAttributes interface {
	IntoTraceAttributes() []attribute.KeyValue
}

func CollectAttributes(attrs ...interface{}) []attribute.KeyValue {
	collected := make([]attribute.KeyValue, len(attrs))
	for _, a := range attrs {
		switch a.(type) {
		case []attribute.KeyValue:
			collected = append(collected, a.([]attribute.KeyValue)...)
		case attribute.KeyValue:
			collected = append(collected, a.(attribute.KeyValue))
		case IntoTraceAttribute:
			collected = append(collected, a.(IntoTraceAttribute).IntoTraceAttribute())
		case IntoTraceAttributes:
			collected = append(collected, a.(IntoTraceAttributes).IntoTraceAttributes()...)
		}
	}
	return collected
}

func WithAttributes(attrs ...interface{}) trace.SpanStartEventOption {
	return trace.WithAttributes(CollectAttributes(attrs...)...)
}

const (
	SeverityLevelKey           = attribute.Key("level")
	LogMessageLongKey          = attribute.Key("log_message.long")
	LogMessageShortKey         = attribute.Key("log_message.short")
	EnduserResponseMessageKey  = attribute.Key("enduser.response_message")
	SessionLanguageIdKey       = attribute.Key("session.language_id")
	SessionCountryIdKey        = attribute.Key("session.country_id")
	SessionCurrencyIdKey       = attribute.Key("session.currency_id")
	ProcessThreadsAvailableKey = attribute.Key("process.threads_available")
	ServiceLayerKey            = attribute.Key("service.layer")
	ServiceLayerNameKey        = attribute.Key("service.layer_name")
)

type ServiceArchitectureLayer string

const (
	LayerFrameworkMiddleware ServiceArchitectureLayer = "framework_middleware"
	LayerHandler                                      = "handler"
	LayerService                                      = "service"
	LayerRepository                                   = "repository"
	LayerORM                                          = "orm"
	LayerUtil                                         = "util"
)

// Build an attribute with a value formatted as json
func JsonAttr(key string, jsonEl map[string]interface{}) attribute.KeyValue {
	jsonStr, _ := json.Marshal(jsonEl)
	return attribute.KeyValue{Key: attribute.Key(key), Value: attribute.StringValue(string(jsonStr))}

}

// An attribute informing about the severity or importance of an event using our own standard of log levels that
// can map to syslog level.
func SeverityLevel(lvl level.SeverityLevel) attribute.KeyValue {
	return attribute.String(string(SeverityLevelKey), lvl.String())
}

func LogMessage(short string, expanded string) []attribute.KeyValue {
	attrs := make([]attribute.KeyValue, 2)
	attrs = append(attrs, LogMessageShort(short), LogMessageLong(expanded))
	return attrs
}

// An attribute which value could be used as the full message field within the GELF format.
func LogMessageLong(msg string) attribute.KeyValue {
	return attribute.String(string(LogMessageLongKey), msg)
}

// An attribute which value could be used as the short message field within the GELF format.
func LogMessageShort(msg string) attribute.KeyValue {
	return attribute.String(string(LogMessageShortKey), msg)
}

// A message provided to the end user. For example, in case of API server errors it might be desired
// to provide to the user a message that does not leak too many details instead of sending an original
// (for a given package) error message.
func EnduserResponseMessage(msg string) attribute.KeyValue {
	return attribute.String(string(EnduserResponseMessageKey), msg)
}

// Inspect the call stack to retrieve the information about a call site location including
// function name, file path, and line number.
func SourceCodeLocation(skipLevelsInCallStack int) []attribute.KeyValue {
	pc, file, line, _ := runtime.Caller(1 + skipLevelsInCallStack)
	funcName := runtime.FuncForPC(pc).Name()

	return []attribute.KeyValue{
		{
			Key:   semconv.CodeFunctionKey,
			Value: attribute.StringValue(funcName),
		},
		{
			Key:   semconv.CodeFilepathKey,
			Value: attribute.StringValue(file),
		},
		{
			Key:   semconv.CodeLineNumberKey,
			Value: attribute.IntValue(line),
		},
	}
}

// Use within some panic handler to generate an attribute that will contain a stack trace.
func PanicStackTrace() attribute.KeyValue {
	stackTrace := string(debug.Stack())
	return semconv.ExceptionStacktrace(stackTrace)
}

// Builds attributes describing a server.
func Server(address string, port int) []attribute.KeyValue {
	return []attribute.KeyValue{
		{
			Key:   semconv.ServerAddressKey,
			Value: attribute.StringValue(address),
		},
		{
			Key:   semconv.ServerPortKey,
			Value: attribute.IntValue(port),
		},
	}
}

// Investigates the running process to derive attributes that describe it. This will only
// try to retrive these details which provide any valuable information at the start of a
// process.
func ProcessStart() []attribute.KeyValue {
	attrs := make([]attribute.KeyValue, 5)
	executablePath, err := os.Executable()
	if err == nil {
		attrs = append(attrs, semconv.ProcessExecutablePath(executablePath))
	}
	hostname, err := os.Hostname()
	if err == nil {
		attrs = append(attrs, semconv.HostName(hostname))
	}

	runtimeVersion := runtime.Version()
	cpuThreads := runtime.NumCPU()
	pid := os.Getpid()
	attrs = append(attrs, semconv.ProcessParentPID(pid), semconv.ProcessRuntimeVersion(runtimeVersion), attribute.KeyValue{
		Key:   ProcessThreadsAvailableKey,
		Value: attribute.IntValue(cpuThreads),
	})

	return attrs
}

// Id of an end user's session.
func SessionId(id string) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   semconv.SessionIDKey,
		Value: attribute.StringValue(id),
	}
}

// Id of a language associated with a user's session.
func SessionLanguageId(id uint) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   SessionLanguageIdKey,
		Value: attribute.IntValue(int(id)),
	}
}

// Id of a country associated with a user's session.
func SessionCountryId(id uint) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   SessionCountryIdKey,
		Value: attribute.IntValue(int(id)),
	}
}

// Id of a currency associated with a user's session.
func SessionCurrencyId(id uint) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   SessionCurrencyIdKey,
		Value: attribute.IntValue(int(id)),
	}
}

// Render details about session as attributes.
func Session(deets SessionDetails) []attribute.KeyValue {
	return deets.IntoTraceAttributes()
}

// A collection of attributes that we at maal frequently attach to user sessions that can
// be converted into a collection of trace attributes. All fields are optional.
type SessionDetails struct {
	ID         *string
	PreviousID *string
	LanguageID *uint
	CountryID  *uint
	CurrencyID *uint
}

func (deets SessionDetails) IntoTraceAttributes() []attribute.KeyValue {
	attrs := make([]attribute.KeyValue, 4) // most frequently we won't have previous session ID
	if deets.ID != nil {
		attrs = append(attrs, SessionId(*deets.ID))
	}
	if deets.PreviousID != nil {
		attrs = append(attrs, attribute.KeyValue{
			Key:   semconv.SessionPreviousIDKey,
			Value: attribute.StringValue(*deets.PreviousID),
		})
	}
	if deets.LanguageID != nil {
		attrs = append(attrs, SessionLanguageId(*deets.LanguageID))
	}
	if deets.CountryID != nil {
		attrs = append(attrs, SessionCountryId(*deets.CountryID))
	}
	if deets.CurrencyID != nil {
		attrs = append(attrs, SessionCurrencyId(*deets.CurrencyID))
	}
	return attrs
}

// Describes a layer of a web server architecture with some of terms frequently used at maal.
func ServiceLayer(layer ServiceArchitectureLayer) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   ServiceLayerKey,
		Value: attribute.StringValue(string(layer)),
	}
}

func ServiceLayerName(name string) attribute.KeyValue {
	return attribute.KeyValue{
		Key:   ServiceLayerNameKey,
		Value: attribute.StringValue(name),
	}
}