package dotenv

import (

	"strings"

	"github.com/spf13/cast"

)

// flattenAndMergeMap recursively flattens the given map into a new map

// Code is based on the function with the same name in tha main package.

// TODO: move it to a common place

func flattenAndMergeMap(shadow map[string]interface{}, m map[string]interface{}, prefix string, delimiter string) map[string]interface{} {

	if shadow != nil && prefix != "" && shadow[prefix] != nil {

		// prefix is shadowed => nothing more to flatten

		return shadow

	}

	if shadow == nil {

		shadow = make(map[string]interface{})

	}

	var m2 map[string]interface{}

	if prefix != "" {

		prefix += delimiter

	}

	for k, val := range m {

		fullKey := prefix + k

		switch val.(type) {

		case map[string]interface{}:

			m2 = val.(map[string]interface{})

		case map[interface{}]interface{}:

			m2 = cast.ToStringMap(val)

		default:

			// immediate value

			shadow[strings.ToLower(fullKey)] = val

			continue

		}

		// recursively merge to shadow map

		shadow = flattenAndMergeMap(shadow, m2, fullKey, delimiter)

	}

	return shadow

}