/*
Copyright 2021 The Kubernetes 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

    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.
*/

package logs

import (
	"flag"
	"fmt"
	"sort"
	"strings"

	"github.com/spf13/pflag"

	cliflag "k8s.io/component-base/cli/flag"
	"k8s.io/component-base/config"
	"k8s.io/component-base/logs/registry"
	"k8s.io/klog/v2"
)

// Supported klog formats
const (
	DefaultLogFormat = "text"
	JSONLogFormat    = "json"
)

// loggingFlags captures the state of the logging flags, in particular their default value
// before flag parsing. It is used by UnsupportedLoggingFlags.
var loggingFlags pflag.FlagSet

func init() {
	// Text format is default klog format
	registry.LogRegistry.Register(DefaultLogFormat, nil)

	var fs flag.FlagSet
	klog.InitFlags(&fs)
	loggingFlags.AddGoFlagSet(&fs)
}

// List of logs (k8s.io/klog + k8s.io/component-base/logs) flags supported by all logging formats
var supportedLogsFlags = map[string]struct{}{
	"v": {},
}

// BindLoggingFlags binds the Options struct fields to a flagset.
//
// Programs using LoggingConfiguration must use SkipLoggingConfigurationFlags
// when calling AddFlags to avoid the duplicate registration of flags.
func BindLoggingFlags(c *config.LoggingConfiguration, fs *pflag.FlagSet) {
	// The help text is generated assuming that flags will eventually use
	// hyphens, even if currently no normalization function is set for the
	// flag set yet.
	unsupportedFlags := strings.Join(unsupportedLoggingFlagNames(cliflag.WordSepNormalizeFunc), ", ")
	formats := fmt.Sprintf(`"%s"`, strings.Join(registry.LogRegistry.List(), `", "`))
	fs.StringVar(&c.Format, "logging-format", c.Format, fmt.Sprintf("Sets the log format. Permitted formats: %s.\nNon-default formats don't honor these flags: %s.\nNon-default choices are currently alpha and subject to change without warning.", formats, unsupportedFlags))
	// No new log formats should be added after generation is of flag options
	registry.LogRegistry.Freeze()

	fs.DurationVar(&c.FlushFrequency, logFlushFreqFlagName, logFlushFreq, "Maximum number of seconds between log flushes")
	fs.VarP(&c.Verbosity, "v", "v", "number for the log level verbosity")
	fs.Var(&c.VModule, "vmodule", "comma-separated list of pattern=N settings for file-filtered logging (only works for text log format)")

	// JSON options. We only register them if "json" is a valid format. The
	// config file API however always has them.
	if _, err := registry.LogRegistry.Get("json"); err == nil {
		fs.BoolVar(&c.Options.JSON.SplitStream, "log-json-split-stream", false, "[Experimental] In JSON format, write error messages to stderr and info messages to stdout. The default is to write a single stream to stdout.")
		fs.Var(&c.Options.JSON.InfoBufferSize, "log-json-info-buffer-size", "[Experimental] In JSON format with split output streams, the info messages can be buffered for a while to increase performance. The default value of zero bytes disables buffering. The size can be specified as number of bytes (512), multiples of 1000 (1K), multiples of 1024 (2Ki), or powers of those (3M, 4G, 5Mi, 6Gi).")
	}
}

// UnsupportedLoggingFlags lists unsupported logging flags. The normalize
// function is optional.
func UnsupportedLoggingFlags(normalizeFunc func(f *pflag.FlagSet, name string) pflag.NormalizedName) []*pflag.Flag {
	// k8s.io/component-base/logs and klog flags
	pfs := &pflag.FlagSet{}
	loggingFlags.VisitAll(func(flag *pflag.Flag) {
		if _, found := supportedLogsFlags[flag.Name]; !found {
			// Normalization changes flag.Name, so make a copy.
			clone := *flag
			pfs.AddFlag(&clone)
		}
	})

	// Apply normalization.
	pfs.SetNormalizeFunc(normalizeFunc)

	var allFlags []*pflag.Flag
	pfs.VisitAll(func(flag *pflag.Flag) {
		allFlags = append(allFlags, flag)
	})
	return allFlags
}

// unsupportedLoggingFlagNames lists unsupported logging flags by name, with
// optional normalization and sorted.
func unsupportedLoggingFlagNames(normalizeFunc func(f *pflag.FlagSet, name string) pflag.NormalizedName) []string {
	unsupportedFlags := UnsupportedLoggingFlags(normalizeFunc)
	names := make([]string, 0, len(unsupportedFlags))
	for _, f := range unsupportedFlags {
		names = append(names, "--"+f.Name)
	}
	sort.Strings(names)
	return names
}