// Licensed to Apache Software Foundation (ASF) under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Apache Software Foundation (ASF) licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package config

import (
	"os"
	"regexp"
	"strconv"
	"strings"

	"github.com/spf13/viper"
)

// ${ENV:defaultVal} pattern is supported to override the default value by the env config.
// And the value would be converted to the different types, such as int, float64 ana string.
// If you want to keep it as the string value, please decorate it with `"`.
const RegularExpression = "${_|[A-Z]+:.*}"

func overrideConfigByEnv(v *viper.Viper) error {
	regex, err := regexp.Compile(RegularExpression)
	if err != nil {
		return err
	}
	overrideCfg := overrideMapStringInterface(v.AllSettings(), regex)
	for key, val := range overrideCfg {
		v.Set(key, val)
	}
	return nil
}

func overrideMapStringInterface(cfg map[string]interface{}, regex *regexp.Regexp) map[string]interface{} {
	res := make(map[string]interface{})
	for key, val := range cfg {
		switch val := val.(type) {
		case string:
			res[key] = overrideString(val, regex)
		case []interface{}:
			res[key] = overrideSlice(val, regex)
		case map[string]interface{}:
			res[key] = overrideMapStringInterface(val, regex)
		case map[interface{}]interface{}:
			res[key] = overrideMapInterfaceInterface(val, regex)
		default:
			res[key] = val
		}
	}
	return res
}

func overrideSlice(m []interface{}, regex *regexp.Regexp) []interface{} {
	res := make([]interface{}, 0)
	for _, val := range m {
		switch val := val.(type) {
		case map[string]interface{}:
			res = append(res, overrideMapStringInterface(val, regex))
		case map[interface{}]interface{}:
			res = append(res, overrideMapInterfaceInterface(val, regex))
		case string:
			res = append(res, val)
		}
	}
	return res
}

func overrideMapInterfaceInterface(m map[interface{}]interface{}, regex *regexp.Regexp) interface{} {
	cfg := make(map[string]interface{})
	for key, val := range m {
		cfg[key.(string)] = val
	}
	return overrideMapStringInterface(cfg, regex)
}

func overrideString(s string, regex *regexp.Regexp) interface{} {
	if regex.MatchString(s) {
		index := strings.Index(s, ":")
		envName := s[2:index]
		defaultVal := s[index+1 : len(s)-1]
		envVal := os.Getenv(envName)
		if envVal != "" {
			defaultVal = envVal
		}
		return parseVal(defaultVal)
	}
	return s
}

func parseVal(val string) interface{} {
	if intVal, err := strconv.Atoi(val); err == nil {
		return intVal
	} else if floatVal, err := strconv.ParseFloat(val, 64); err == nil {
		return floatVal
	} else if strings.EqualFold(val, "true") {
		return true
	} else if strings.EqualFold(val, "false") {
		return false
	} else if strings.HasPrefix(val, "\"") && strings.HasSuffix(val, "\"") {
		return val[1 : len(val)-1]
	} else {
		return val
	}
}