package config

import (
	"fmt"
	"os"
	"strings"

	"github.com/go-kratos/kratos/v2/encoding"
	"github.com/go-kratos/kratos/v2/log"
)

// Decoder is config decoder.
type Decoder func(*KeyValue, map[string]interface{}) error

// Resolver resolve placeholder in config.
type Resolver func(map[string]interface{}) error

// Option is config option.
type Option func(*options)

type options struct {
	sources  []Source
	decoder  Decoder
	resolver Resolver
	logger   log.Logger
}

// WithSource with config source.
func WithSource(s ...Source) Option {
	return func(o *options) {
		o.sources = s
	}
}

// WithDecoder with config decoder.
func WithDecoder(d Decoder) Option {
	return func(o *options) {
		o.decoder = d
	}
}

// WithResolver with config resolver.
func WithResolver(r Resolver) Option {
	return func(o *options) {
		o.resolver = r
	}
}

// WithLogger with config logger.
func WithLogger(l log.Logger) Option {
	return func(o *options) {
		o.logger = l
	}
}

// defaultDecoder decode config from source KeyValue
// to target map[string]interface{} using src.Format codec.
func defaultDecoder(src *KeyValue, target map[string]interface{}) error {
	if src.Format == "" {
		target[src.Key] = src.Value
		return nil
	}
	if codec := encoding.GetCodec(src.Format); codec != nil {
		return codec.Unmarshal(src.Value, &target)
	}
	return fmt.Errorf("unsupported key: %s format: %s", src.Key, src.Format)
}

// defaultResolver resolve placeholder in map value,
// placeholder format in ${key:default} or $key.
func defaultResolver(input map[string]interface{}) error {
	mapper := func(name string) string {
		args := strings.Split(strings.TrimSpace(name), ":")
		if v, has := readValue(input, args[0]); has {
			s, _ := v.String()
			return s
		} else if len(args) > 1 { // default value
			return args[1]
		}
		return ""
	}

	var resolve func(map[string]interface{}) error
	resolve = func(sub map[string]interface{}) error {
		for k, v := range sub {
			switch vt := v.(type) {
			case string:
				sub[k] = os.Expand(vt, mapper)
			case map[string]interface{}:
				if err := resolve(vt); err != nil {
					return err
				}
			case []interface{}:
				for i, iface := range vt {
					if s, ok := iface.(string); ok {
						vt[i] = os.Expand(s, mapper)
					}
				}
				sub[k] = vt
			}
		}
		return nil
	}
	return resolve(input)
}