// Package log provides logging for rclone
package log

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"os"
	"reflect"
	"runtime"
	"strings"
	"time"

	"github.com/rclone/rclone/fs"
	"gopkg.in/natefinch/lumberjack.v2"
)

// OptionsInfo descripts the Options in use
var OptionsInfo = fs.Options{{
	Name:    "log_file",
	Default: "",
	Help:    "Log everything to this file",
	Groups:  "Logging",
}, {
	Name:    "log_file_max_size",
	Default: fs.SizeSuffix(-1),
	Help:    `Maximum size of the log file before it's rotated (eg "10M")`,
	Groups:  "Logging",
}, {
	Name:    "log_file_max_backups",
	Default: 0,
	Help:    "Maximum number of old log files to retain.",
	Groups:  "Logging",
}, {
	Name:    "log_file_max_age",
	Default: fs.Duration(0),
	Help:    `Maximum duration to retain old log files (eg "7d")`,
	Groups:  "Logging",
}, {
	Name:    "log_file_compress",
	Default: false,
	Help:    "If set, compress rotated log files using gzip.",
	Groups:  "Logging",
}, {
	Name:    "log_format",
	Default: logFormatDate | logFormatTime,
	Help:    "Comma separated list of log format options",
	Groups:  "Logging",
}, {
	Name:    "syslog",
	Default: false,
	Help:    "Use Syslog for logging",
	Groups:  "Logging",
}, {
	Name:    "syslog_facility",
	Default: "DAEMON",
	Help:    "Facility for syslog, e.g. KERN,USER",
	Groups:  "Logging",
}, {
	Name:    "log_systemd",
	Default: false,
	Help:    "Activate systemd integration for the logger",
	Groups:  "Logging",
}, {
	Name:    "windows_event_log_level",
	Default: fs.LogLevelOff,
	Help:    "Windows Event Log level DEBUG|INFO|NOTICE|ERROR|OFF",
	Groups:  "Logging",
	Hide: func() fs.OptionVisibility {
		if runtime.GOOS == "windows" {
			return 0
		}
		return fs.OptionHideBoth
	}(),
}}

// Options contains options for controlling the logging
type Options struct {
	File                 string        `config:"log_file"`             // Log everything to this file
	MaxSize              fs.SizeSuffix `config:"log_file_max_size"`    // Max size of log file
	MaxBackups           int           `config:"log_file_max_backups"` // Max backups of log file
	MaxAge               fs.Duration   `config:"log_file_max_age"`     // Max age of log file
	Compress             bool          `config:"log_file_compress"`    // Set to compress log file
	Format               logFormat     `config:"log_format"`           // Comma separated list of log format options
	UseSyslog            bool          `config:"syslog"`               // Use Syslog for logging
	SyslogFacility       string        `config:"syslog_facility"`      // Facility for syslog, e.g. KERN,USER,...
	LogSystemdSupport    bool          `config:"log_systemd"`          // set if using systemd logging
	WindowsEventLogLevel fs.LogLevel   `config:"windows_event_log_level"`
}

func init() {
	fs.RegisterGlobalOptions(fs.OptionsInfo{Name: "log", Opt: &Opt, Options: OptionsInfo})
}

// Opt is the options for the logger
var Opt Options

// enum for the log format
type logFormat = fs.Bits[logFormatChoices]

const (
	logFormatDate logFormat = 1 << iota
	logFormatTime
	logFormatMicroseconds
	logFormatUTC
	logFormatLongFile
	logFormatShortFile
	logFormatPid
	logFormatNoLevel
	logFormatJSON
)

type logFormatChoices struct{}

func (logFormatChoices) Choices() []fs.BitsChoicesInfo {
	return []fs.BitsChoicesInfo{
		{Bit: uint64(logFormatDate), Name: "date"},
		{Bit: uint64(logFormatTime), Name: "time"},
		{Bit: uint64(logFormatMicroseconds), Name: "microseconds"},
		{Bit: uint64(logFormatUTC), Name: "UTC"},
		{Bit: uint64(logFormatLongFile), Name: "longfile"},
		{Bit: uint64(logFormatShortFile), Name: "shortfile"},
		{Bit: uint64(logFormatPid), Name: "pid"},
		{Bit: uint64(logFormatNoLevel), Name: "nolevel"},
		{Bit: uint64(logFormatJSON), Name: "json"},
	}
}

// fnName returns the name of the calling +2 function
func fnName() string {
	pc, _, _, ok := runtime.Caller(2)
	name := "*Unknown*"
	if ok {
		name = runtime.FuncForPC(pc).Name()
		dot := strings.LastIndex(name, ".")
		if dot >= 0 {
			name = name[dot+1:]
		}
	}
	return name
}

// Trace debugs the entry and exit of the calling function
//
// It is designed to be used in a defer statement, so it returns a
// function that logs the exit parameters.
//
// Any pointers in the exit function will be dereferenced
func Trace(o any, format string, a ...any) func(string, ...any) {
	if fs.GetConfig(context.Background()).LogLevel < fs.LogLevelDebug {
		return func(format string, a ...any) {}
	}
	name := fnName()
	fs.LogPrintf(fs.LogLevelDebug, o, name+": "+format, a...)
	return func(format string, a ...any) {
		for i := range a {
			// read the values of the pointed to items
			typ := reflect.TypeOf(a[i])
			if typ.Kind() == reflect.Pointer {
				value := reflect.ValueOf(a[i])
				if value.IsNil() {
					a[i] = nil
				} else {
					pointedToValue := reflect.Indirect(value)
					a[i] = pointedToValue.Interface()
				}
			}
		}
		fs.LogPrintf(fs.LogLevelDebug, o, ">"+name+": "+format, a...)
	}
}

// Stack logs a stack trace of callers with the o and info passed in
func Stack(o any, info string) {
	if fs.GetConfig(context.Background()).LogLevel < fs.LogLevelDebug {
		return
	}
	arr := [16 * 1024]byte{}
	buf := arr[:]
	n := runtime.Stack(buf, false)
	buf = buf[:n]
	fs.LogPrintf(fs.LogLevelDebug, o, "%s\nStack trace:\n%s", info, buf)
}

// This is called from fs when the config is reloaded
//
// The config should really be here but we can't move it as it is
// externally visible in the rc.
func logReload(ci *fs.ConfigInfo) error {
	Handler.SetLevel(fs.LogLevelToSlog(ci.LogLevel))

	if Opt.WindowsEventLogLevel != fs.LogLevelOff && Opt.WindowsEventLogLevel > ci.LogLevel {
		return fmt.Errorf("--windows-event-log-level %q must be >= --log-level %q", Opt.WindowsEventLogLevel, ci.LogLevel)
	}

	return nil
}

func init() {
	fs.LogReload = logReload
}

// InitLogging start the logging as per the command line flags
//
// This is called explicitly from the CLI, the librclone wrapper and
// the test framework, but not from package init, so that importing
// rclone as a library has no side effects on the process-wide default
// slog logger.
func InitLogging() {
	// Redirect the process-wide default logger through rclone's
	// handler so that log.Print/log.Fatal and slog.Default() (used by
	// some standard library and third party code) end up in rclone's
	// log output.
	slog.SetDefault(slog.New(Handler))

	// Make log.Printf logs at level Notice
	slog.SetLogLoggerLevel(fs.SlogLevelNotice)

	// Note that ci only has the defaults in at this point
	// We set real values in logReload
	ci := fs.GetConfig(context.Background())

	// Log file output
	if Opt.File != "" {
		var w io.Writer
		if Opt.MaxSize < 0 {
			// No log rotation - just open the file as normal
			// We'll capture tracebacks like this too.
			f, err := os.OpenFile(Opt.File, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0640)
			if err != nil {
				fs.Fatalf(nil, "Failed to open log file: %v", err)
			}
			redirectStderr(f)
			w = f
		} else {
			// Round with a minimum of 1 if set
			round := func(x float64) int {
				if x <= 0 {
					return 0
				} else if x <= 1 {
					return 1
				}
				return int(x + 0.5)
			}
			// Log rotation active
			f := &lumberjack.Logger{
				Filename:   Opt.File,
				MaxSize:    round(float64(Opt.MaxSize) / float64(fs.Mebi)), // MiB
				MaxBackups: Opt.MaxBackups,
				MaxAge:     round(time.Duration(Opt.MaxAge).Hours() / 24), // Days
				Compress:   Opt.Compress,
				LocalTime:  true, // format log file names in localtime
			}
			w = f
		}
		Handler.setWriter(w)
	}

	// --use-json-log implies JSON formatting
	if ci.UseJSONLog {
		Opt.Format |= logFormatJSON
	}

	// Set slog level to initial log level
	Handler.SetLevel(fs.LogLevelToSlog(fs.InitialLogLevel()))

	// Set the format to the configured format
	Handler.setFormat(Opt.Format)

	// Syslog output
	if Opt.UseSyslog {
		if Opt.File != "" {
			fs.Fatalf(nil, "Can't use --syslog and --log-file together")
		}
		startSysLog(Handler)
	}

	// Activate systemd logger support if systemd invocation ID is
	// detected and output is going to stderr (not logging to a file or syslog)
	if !Redirected() {
		if isJournalStream() {
			Opt.LogSystemdSupport = true
		}
	}

	// Systemd logging output
	if Opt.LogSystemdSupport {
		startSystemdLog(Handler)
	}

	// Windows event logging
	if Opt.WindowsEventLogLevel != fs.LogLevelOff {
		err := startWindowsEventLog(Handler)
		if err != nil {
			fs.Fatalf(nil, "Failed to start windows event log: %v", err)
		}
	}
}

// Redirected returns true if the log has been redirected from stdout
func Redirected() bool {
	return Opt.UseSyslog || Opt.File != ""
}
