package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"reflect"
	"regexp"
	"strings"

	"github.com/BurntSushi/toml"

	"gopkg.in/yaml.v2"
)

type Configurator struct {
	*Config
}

type Config struct {
	Environment string
	ENVPrefix   string
}

// New initialize a Configurator
func New(config *Config) *Configurator {
	if config == nil {
		config = &Config{}
	}
	return &Configurator{Config: config}
}

// GetEnvironment get environment
func (c *Configurator) GetEnvironment() string {
	if c.Environment == "" {
		if env := os.Getenv("CONFIGOR_ENV"); env != "" {
			return env
		}

		if isTest, _ := regexp.MatchString("/_test/", os.Args[0]); isTest {
			return "test"
		}

		return "development"
	}
	return c.Environment
}

// Load will unmarshal configurations to struct from files that you provide
func (c *Configurator) Load(config interface{}, files ...string) error {
	for _, file := range c.getConfigurationFiles(files...) {
		if err := processFile(config, file); err != nil {
			return err
		}
	}

	if prefix := c.getENVPrefix(config); prefix == "-" {
		return processTags(config)
	} else {
		return processTags(config, prefix)
	}
}

func (c *Configurator) getENVPrefix(config interface{}) string {
	if c.Config.ENVPrefix == "" {
		if prefix := os.Getenv("CONFIGOR_ENV_PREFIX"); prefix != "" {
			return prefix
		}
		return "Configurator"
	}
	return c.Config.ENVPrefix
}

func (c *Configurator) getConfigurationFiles(files ...string) []string {
	var results []string

	for i := len(files) - 1; i >= 0; i-- {
		foundFile := false
		file := files[i]

		// check configuration
		if fileInfo, err := os.Stat(file); err == nil && fileInfo.Mode().IsRegular() {
			foundFile = true
			results = append(results, file)
		}

		// check configuration with env
		if file, err := getConfigurationFileWithENVPrefix(file, c.GetEnvironment()); err == nil {
			foundFile = true
			results = append(results, file)
		}

		// check example configuration
		if !foundFile {
			if example, err := getConfigurationFileWithENVPrefix(file, "example"); err == nil {
				fmt.Printf("Failed to find configuration %v, using example file %v\n", file, example)
				results = append(results, example)
			} else {
				fmt.Printf("Failed to find configuration %v\n", file)
			}
		}
	}
	return results
}

// ENV return environment
func ENV() string {
	return New(nil).GetEnvironment()
}

// Load will unmarshal configurations to struct from files that you provide
func Load(config interface{}, files ...string) error {
	return New(nil).Load(config, files...)
}

func getConfigurationFileWithENVPrefix(file, env string) (string, error) {
	var (
		envFile string
		extname = path.Ext(file)
	)

	if extname == "" {
		envFile = fmt.Sprintf("%v.%v", file, env)
	} else {
		envFile = fmt.Sprintf("%v.%v%v", strings.TrimSuffix(file, extname), env, extname)
	}

	if fileInfo, err := os.Stat(envFile); err == nil && fileInfo.Mode().IsRegular() {
		return envFile, nil
	}
	return "", fmt.Errorf("failed to find file %v", file)
}

func processFile(config interface{}, file string) error {
	data, err := ioutil.ReadFile(file)
	if err != nil {
		return err
	}

	switch {
	case strings.HasSuffix(file, ".yaml") || strings.HasSuffix(file, ".yml"):
		return yaml.Unmarshal(data, config)
	case strings.HasSuffix(file, ".toml"):
		return toml.Unmarshal(data, config)
	case strings.HasSuffix(file, ".json"):
		return json.Unmarshal(data, config)
	default:
		if toml.Unmarshal(data, config) != nil {
			if json.Unmarshal(data, config) != nil {
				if yaml.Unmarshal(data, config) != nil {
					return errors.New("failed to decode config")
				}
			}
		}
		return nil
	}
}

func getPrefixForStruct(prefixes []string, fieldStruct *reflect.StructField) []string {
	if fieldStruct.Anonymous && fieldStruct.Tag.Get("anonymous") == "true" {
		return prefixes
	}
	return append(prefixes, fieldStruct.Name)
}

func processTags(config interface{}, prefixes ...string) error {
	configValue := reflect.Indirect(reflect.ValueOf(config))
	if configValue.Kind() != reflect.Struct {
		return errors.New("invalid config, should be struct")
	}

	configType := configValue.Type()
	for i := 0; i < configType.NumField(); i++ {
		var (
			envNames    []string
			fieldStruct = configType.Field(i)
			field       = configValue.Field(i)
			envName     = fieldStruct.Tag.Get("env") // read configuration from shell env
		)

		if envName == "" {
			envNames = append(envNames, strings.Join(append(prefixes, fieldStruct.Name), "_"))                  // Configor_DB_Name
			envNames = append(envNames, strings.ToUpper(strings.Join(append(prefixes, fieldStruct.Name), "_"))) // CONFIGOR_DB_NAME
		} else {
			envNames = []string{envName}
		}

		// Load From Shell ENV
		for _, env := range envNames {
			if value := os.Getenv(env); value != "" {
				if err := yaml.Unmarshal([]byte(value), field.Addr().Interface()); err != nil {
					return err
				}
				break
			}
		}

		if isBlank := reflect.DeepEqual(field.Interface(), reflect.Zero(field.Type()).Interface()); isBlank {
			// Set default configuration if blank
			if value := fieldStruct.Tag.Get("default"); value != "" {
				if err := yaml.Unmarshal([]byte(value), field.Addr().Interface()); err != nil {
					return err
				}
			} else if fieldStruct.Tag.Get("required") == "true" {
				// return error if it is required but blank
				return errors.New(fieldStruct.Name + " is required, but blank")
			}
		}

		for field.Kind() == reflect.Ptr {
			field = field.Elem()
		}

		if field.Kind() == reflect.Struct {
			if err := processTags(field.Addr().Interface(), getPrefixForStruct(prefixes, &fieldStruct)...); err != nil {
				return err
			}
		}

		if field.Kind() == reflect.Slice {
			for i := 0; i < field.Len(); i++ {
				if reflect.Indirect(field.Index(i)).Kind() == reflect.Struct {
					if err := processTags(field.Index(i).Addr().Interface(), append(getPrefixForStruct(prefixes, &fieldStruct), fmt.Sprint(i))...); err != nil {
						return err
					}
				}
			}
		}
	}
	return nil
}