package stripe

import (
	"fmt"
	"io"
	"log"
	"os"
)

//
// Public constants
//

const (
	// LevelError sets a logger to show error messages only.
	LevelError Level = 1

	// LevelWarn sets a logger to show warning messages or anything more
	// severe.
	LevelWarn Level = 2

	// LevelInfo sets a logger to show informational messages or anything more
	// severe.
	LevelInfo Level = 3

	// LevelDebug sets a logger to show informational messages or anything more
	// severe.
	LevelDebug Level = 4

	// Older deprecated levels for Printfer-style logging.
	printferLevelError = 1
	printferLevelInfo  = 2
	printferLevelDebug = 3
)

//
// Public variables
//

// DefaultLeveledLogger is the default logger that the library will use to log
// errors, warnings, and informational messages.
//
// LeveledLoggerInterface is implemented by LeveledLogger, and one can be
// initialized at the desired level of logging.  LeveledLoggerInterface also
// provides out-of-the-box compatibility with a Logrus Logger, but may require
// a thin shim for use with other logging libraries that use less standard
// conventions like Zap.
//
// This Logger will be inherited by any backends created by default, but will
// be overridden if a backend is created with GetBackendWithConfig with a
// custom LeveledLogger set.
var DefaultLeveledLogger LeveledLoggerInterface

// LogLevel is the logging level for this library.
// 0: no logging
// 1: errors only
// 2: errors + informational (default)
// 3: errors + informational + debug
//
// Deprecated: Logging should be configured with DefaultLeveledLogger instead.
var LogLevel = 2

// Logger controls how stripe performs logging at a package level. It is useful
// to customise if you need it prefixed for your application to meet other
// requirements.
//
// This Logger will be inherited by any backends created by default, but will
// be overridden if a backend is created with GetBackendWithConfig with a
// custom Logger set.
//
// Deprecated: Logging should be configured with DefaultLeveledLogger instead.
var Logger Printfer

//
// Public types
//

// Level represents a logging level.
type Level uint32

// LeveledLogger is a leveled logger implementation.
//
// It prints warnings and errors to `os.Stderr` and other messages to
// `os.Stdout`.
type LeveledLogger struct {
	// Level is the minimum logging level that will be emitted by this logger.
	//
	// For example, a Level set to LevelWarn will emit warnings and errors, but
	// not informational or debug messages.
	//
	// Always set this with a constant like LevelWarn because the individual
	// values are not guaranteed to be stable.
	Level Level

	// Internal testing use only.
	stderrOverride io.Writer
	stdoutOverride io.Writer
}

// Debugf logs a debug message using Printf conventions.
func (l *LeveledLogger) Debugf(format string, v ...interface{}) {
	if l.Level >= LevelDebug {
		fmt.Fprintf(l.stdout(), "[DEBUG] "+format+"\n", v...)
	}
}

// Errorf logs a warning message using Printf conventions.
func (l *LeveledLogger) Errorf(format string, v ...interface{}) {
	// Infof logs a debug message using Printf conventions.
	if l.Level >= LevelError {
		fmt.Fprintf(l.stderr(), "[ERROR] "+format+"\n", v...)
	}
}

// Infof logs an informational message using Printf conventions.
func (l *LeveledLogger) Infof(format string, v ...interface{}) {
	if l.Level >= LevelInfo {
		fmt.Fprintf(l.stdout(), "[INFO] "+format+"\n", v...)
	}
}

// Warnf logs a warning message using Printf conventions.
func (l *LeveledLogger) Warnf(format string, v ...interface{}) {
	if l.Level >= LevelWarn {
		fmt.Fprintf(l.stderr(), "[WARN] "+format+"\n", v...)
	}
}

func (l *LeveledLogger) stderr() io.Writer {
	if l.stderrOverride != nil {
		return l.stderrOverride
	}

	return os.Stderr
}

func (l *LeveledLogger) stdout() io.Writer {
	if l.stdoutOverride != nil {
		return l.stdoutOverride
	}

	return os.Stdout
}

// LeveledLoggerInterface provides a basic leveled logging interface for
// printing debug, informational, warning, and error messages.
//
// It's implemented by LeveledLogger and also provides out-of-the-box
// compatibility with a Logrus Logger, but may require a thin shim for use with
// other logging libraries that you use less standard conventions like Zap.
type LeveledLoggerInterface interface {
	// Debugf logs a debug message using Printf conventions.
	Debugf(format string, v ...interface{})

	// Errorf logs a warning message using Printf conventions.
	Errorf(format string, v ...interface{})

	// Infof logs an informational message using Printf conventions.
	Infof(format string, v ...interface{})

	// Warnf logs a warning message using Printf conventions.
	Warnf(format string, v ...interface{})
}

// Printfer is an interface to be implemented by Logger.
type Printfer interface {
	Printf(format string, v ...interface{})
}

//
// Private types
//

// Level represents a deprecated logging level.
type printferLevel uint32

type leveledLoggerPrintferShim struct {
	level  printferLevel
	logger Printfer
}

// Debugf logs a debug message using Printf conventions.
func (l *leveledLoggerPrintferShim) Debugf(format string, v ...interface{}) {
	if l.level >= printferLevelDebug {
		l.logger.Printf(format+"\n", v...)
	}
}

// Errorf logs a warning message using Printf conventions.
func (l *leveledLoggerPrintferShim) Errorf(format string, v ...interface{}) {
	if l.level >= printferLevelError {
		l.logger.Printf(format+"\n", v...)
	}
}

// Infof logs an informational message using Printf conventions.
func (l *leveledLoggerPrintferShim) Infof(format string, v ...interface{}) {
	if l.level >= printferLevelInfo {
		l.logger.Printf(format+"\n", v...)
	}
}

// Warnf logs a warning message using Printf conventions.
func (l *leveledLoggerPrintferShim) Warnf(format string, v ...interface{}) {
	// The original Stripe log level system didn't have a concept for warnings,
	// so just reuse the same levels as error.
	if l.level >= printferLevelError {
		l.logger.Printf(format+"\n", v...)
	}
}

//
// Private functions
//

func init() {
	// Defaults to logging nothing, but also makes sure that we have a logger
	// so that we don't panic on a `nil` when the library tries to log
	// something.
	Logger = log.New(os.Stderr, "", log.LstdFlags)
}