// Copyright 2020 PingCAP, Inc. Licensed under Apache-2.0.

package logutil

import (
	"context"

	"github.com/pingcap/log"
	"go.uber.org/zap"
)

// We cannot directly set global logger as log.L(),
// or when the global logger updated, we cannot get the latest logger.
var globalLogger *zap.Logger = nil

// ResetGlobalLogger resets the global logger.
// Contexts have already made by `ContextWithField` would keep untouched,
// subsequent wrapping over those contexts would keep using the old global logger,
// only brand new contexts (i.e. context without logger) would be wrapped with the new global logger.
// This method is mainly for testing.
func ResetGlobalLogger(l *zap.Logger) {
	globalLogger = l
}

type loggingContextKey struct{}

var keyLogger loggingContextKey = loggingContextKey{}

// ContextWithField wrap a context with a logger with some fields.
func ContextWithField(c context.Context, fields ...zap.Field) context.Context {
	logger := LoggerFromContext(c).With(fields...)
	return context.WithValue(c, keyLogger, logger)
}

// LoggerFromContext returns the contextual logger via the context.
// If there isn't a logger in the context, returns the global logger.
func LoggerFromContext(c context.Context) *zap.Logger {
	logger, ok := c.Value(keyLogger).(*zap.Logger)
	if !ok {
		if globalLogger != nil {
			return globalLogger
		}
		return log.L()
	}
	return logger
}

// CL is the shorthand for LoggerFromContext.
func CL(c context.Context) *zap.Logger {
	return LoggerFromContext(c)
}