package log

import (
	"fmt"
)

// An Option configures a Logger.
type Option interface {
	apply(*Logger)
}

// optionFunc wraps a func, so it satisfies the Option interface.
type optionFunc func(*Logger)

func (f optionFunc) apply(log *Logger) {
	f(log)
}

// WrapCore wraps or replaces the Logger's underlying Core.
func WrapCore(f func(Core) Core) Option {
	return optionFunc(func(log *Logger) {
		log.core = f(log.core)
	})
}

func WithName(name string) Option {
	return optionFunc(func(log *Logger) {
		log.name = name
	})
}

func AddSubName(name string) Option {
	return optionFunc(func(log *Logger) {
		if log.name == "" {
			log.name = name
		} else {
			log.name = log.name + "." + name
		}
	})
}

// Hooks registers functions which will be called each time the Logger writes
// out an Entry. Repeated use of Hooks is additive.
//
// Hooks are useful for simple side effects, like capturing metrics for the
// number of emitted logs. More complex side effects, including anything that
// requires access to the Entry's structured fields, should be implemented as
// a Core instead. See RegisterHooks for details.
func Hooks(hooks ...func(Entry) error) Option {
	return optionFunc(func(log *Logger) {
		log.core = RegisterHooks(log.core, hooks...)
	})
}

// Fields adds fields to the Logger.
func Fields(fs ...Field) Option {
	return optionFunc(func(log *Logger) {
		log.core = log.core.With(fs)
	})
}

// ErrorOutput sets the destination for errors generated by the Logger. Note
// that this option only affects internal errors; for sample code that sends
// error-level logs to a different location from info- and debug-level logs,
// see the package-level AdvancedConfiguration example.
//
// The supplied WriteSyncer must be safe for concurrent use. The Open and
// Lock functions are the simplest ways to protect files with a mutex.
func ErrorOutput(w WriteSyncer) Option {
	return optionFunc(func(log *Logger) {
		log.errorOutput = w
	})
}

// Development puts the logger in development mode, which makes DPanic-level
// logs panic instead of simply logging an error.
func Development() Option {
	return optionFunc(func(log *Logger) {
		log.development = true
	})
}

// AddCaller configures the Logger to annotate each message with the filename,
// line number, and function name of log's caller. See also WithCaller.
func AddCaller() Option {
	return WithCaller(true)
}

// WithCaller configures the Logger to annotate each message with the filename,
// line number, and function name of log's caller, or not, depending on the
// value of enabled. This is a generalized form of AddCaller.
func WithCaller(enabled bool) Option {
	return optionFunc(func(log *Logger) {
		log.addCaller = enabled
	})
}

// AddCallerSkip increases the number of callers skipped by caller annotation
// (as enabled by the AddCaller option). When building wrappers around the
// Logger and SugaredLogger, supplying this Option prevents log from always
// reporting the wrapper code as the caller.
func AddCallerSkip(skip int) Option {
	return optionFunc(func(log *Logger) {
		log.callerSkip += skip
	})
}

// AddStacktrace configures the Logger to record a stack trace for all messages at
// or above a given level.
func AddStacktrace(lvl LevelEnabler) Option {
	return optionFunc(func(log *Logger) {
		log.addStack = lvl
	})
}

// IncreaseLevel increase the level of the logger. It has no effect if
// the passed in level tries to decrease the level of the logger.
func IncreaseLevel(lvl LevelEnabler) Option {
	return optionFunc(func(log *Logger) {
		core, err := NewIncreaseLevelCore(log.core, lvl)
		if err != nil {
			fmt.Fprintf(log.errorOutput, "failed to IncreaseLevel: %v\n", err)
		} else {
			log.core = core
		}
	})
}

// OnFatal sets the action to take on fatal logs.
func OnFatal(action CheckWriteAction) Option {
	return optionFunc(func(log *Logger) {
		log.onFatal = action
	})
}

// WithClock specifies the clock used by the logger to determine the current
// time for logged entries. Defaults to the system clock with time.Now.
func WithClock(clock Clock) Option {
	return optionFunc(func(log *Logger) {
		log.clock = clock
	})
}