package encoding

import (

	"sync"

)

// Decoder decodes the contents of b into v.

// It's primarily used for decoding contents of a file into a map[string]interface{}.

type Decoder interface {

	Decode(b []byte, v map[string]interface{}) error

}

const (

	// ErrDecoderNotFound is returned when there is no decoder registered for a format.

	ErrDecoderNotFound = encodingError("decoder not found for this format")

	// ErrDecoderFormatAlreadyRegistered is returned when an decoder is already registered for a format.

	ErrDecoderFormatAlreadyRegistered = encodingError("decoder already registered for this format")

)

// DecoderRegistry can choose an appropriate Decoder based on the provided format.

type DecoderRegistry struct {

	decoders map[string]Decoder

	mu sync.RWMutex

}

// NewDecoderRegistry returns a new, initialized DecoderRegistry.

func NewDecoderRegistry() *DecoderRegistry {

	return &DecoderRegistry{

		decoders: make(map[string]Decoder),

	}

}

// RegisterDecoder registers a Decoder for a format.

// Registering a Decoder for an already existing format is not supported.

func (e *DecoderRegistry) RegisterDecoder(format string, enc Decoder) error {

	e.mu.Lock()

	defer e.mu.Unlock()

	if _, ok := e.decoders[format]; ok {

		return ErrDecoderFormatAlreadyRegistered

	}

	e.decoders[format] = enc

	return nil

}

// Decode calls the underlying Decoder based on the format.

func (e *DecoderRegistry) Decode(format string, b []byte, v map[string]interface{}) error {

	e.mu.RLock()

	decoder, ok := e.decoders[format]

	e.mu.RUnlock()

	if !ok {

		return ErrDecoderNotFound

	}

	return decoder.Decode(b, v)

}