package log

import (
	"fmt"
	"os"
	"strconv"
	"strings"

	"github.com/juju/errors"
	"github.com/sirupsen/logrus"
	"gopkg.in/yaml.v3"

	"git.dev.m-and-m.ovh/mderasse/gocommon/convert"
	"git.dev.m-and-m.ovh/mderasse/gocommon/log/hooks/file"
	"git.dev.m-and-m.ovh/mderasse/gocommon/log/hooks/gelf"
)

// envPrefix is the prefix that will be used for any environnement variable used to configure the logging system.
const envPrefix = "LOG_"

// CONFIG_FILE is the default file that will be searched to apply configuration from the filesystem.
const defaultConfigFile = "log.yaml"

// SECRET_NAME is the default name of the secret that will be searched in vault.
const defaultSecretName = "log"

// ConfigStruct represent the configuration of our logger system.
type ConfigStruct struct {
	EnableStdOut *bool                  `yaml:"ensable_std_out"`
	ExtrasFields map[string]interface{} `yaml:"extra_fields"`
	FileConfig   *file.ConfigStruct     `yaml:"file_config"`
	GelfConfig   *gelf.ConfigStruct     `yaml:"gelf_config"`
	Level        *string                `yaml:"level"`
	Providers    []ProviderName         `yaml:"providers"`
}

func newDefaultConfig() *ConfigStruct {
	return &ConfigStruct{
		Level:        convert.ToPointer("debug"),
		EnableStdOut: convert.ToPointer(true),
		Providers:    []ProviderName{ProviderName_NONE},
	}
}

func loadConfigFromVault(secret string) (*ConfigStruct, error) {
	return nil, os.ErrNotExist
}

// loadConfigFromFile will read the given file and return a config struct.
func loadConfigFromFile(path string) (*ConfigStruct, error) {

	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
		return nil, errors.Trace(err)
	}

	//nolint:gosec // we did compute the file path
	f, err := os.ReadFile(path)
	if err != nil {
		return nil, errors.Trace(err)
	}

	var config ConfigStruct

	if err := yaml.Unmarshal(f, &config); err != nil {
		return nil, errors.Trace(err)
	}

	return &config, nil
}

func loadConfig() (*ConfigStruct, error) {

	c, err := loadConfigFromVault(defaultSecretName)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, err
	} else if err == nil {
		return c, nil
	}

	c, err = loadConfigFromFile(defaultConfigFile)
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, err
	} else if err == nil {
		return c, nil
	}

	return newDefaultConfig(), nil
}

// applyEnv will retrieve info from environment variable and overide those got by config / vault.
// validity of the value is not checked here and will be check in a IsValid method.
func (c *ConfigStruct) applyEnv() error {

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "LEVEL")); v != "" {
		c.Level = convert.ToPointer(v)
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "ENABLE_STDOUT")); v != "" {
		b, err := strconv.ParseBool(v)
		if err != nil {
			return errors.NewNotValid(err, fmt.Sprintf("Invalid %s%s environment variable. Should be a boolean", envPrefix, "ENABLE_STDOUT"))
		}
		c.EnableStdOut = convert.ToPointer(b)
	}

	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "PROVIDERS")); v != "" {
		providersStr := strings.Split(v, ",")
		var providers []ProviderName
		for _, ps := range providersStr {
			providers = append(providers, ProviderName(ps))
		}
		c.Providers = providers
	}

	// Extra Fields
	if v := os.Getenv(fmt.Sprintf("%s%s", envPrefix, "EXTRA_FIELDS")); v != "" {
		extraFieldsPart := strings.Split(v, ",")
		for _, efp := range extraFieldsPart {
			extraFieldKV := strings.SplitN(efp, ":", 1)
			if len(extraFieldKV) != 2 {
				return errors.NotValidf(fmt.Sprintf("Invalid extra_field %s in environment variable. Should be a key1:value1,key2:value2 format", efp))
			}
			c.ExtrasFields[extraFieldKV[0]] = extraFieldKV[1]
		}
	}

	return nil
}

// applyDefault will check the gaven config and will apply default on empty field.
func (c *ConfigStruct) applyDefault() {

	defaultConfig := newDefaultConfig()

	if c.Level == nil || *c.Level == "" {
		c.Level = defaultConfig.Level
	}

	if c.EnableStdOut == nil {
		c.EnableStdOut = defaultConfig.EnableStdOut
	}

	if c.Providers == nil || len(c.Providers) == 0 {
		c.Providers = defaultConfig.Providers
	}
}

// IsValid will check a config struct.
func (c *ConfigStruct) IsValid() error {

	if c.EnableStdOut == nil {
		return errors.NotValidf("EnableStdOut is empty")
	}

	if c.Level == nil {
		return errors.NotValidf("Level is empty")
	} else if _, err := logrus.ParseLevel(*c.Level); err != nil {
		return errors.NotValidf("Invalid Level. Allowed values: %s", strings.Join(convert.StringerSliceToStringSlice(logrus.AllLevels), ", "))
	}

	if c.Providers == nil || len(c.Providers) == 0 {
		return errors.NotValidf("Providers is empty")
	}

	// Validating configuration for the chosen provider.
	for _, provider := range c.Providers {
		if !provider.IsValid() {
			return errors.NotValidf("Invalid Provider %s. Allowed values: %s", provider.String(), strings.Join(convert.StringerSliceToStringSlice(GetListProviderName()), ", "))
		}

		switch provider {
		case ProviderName_FILE:
			if c.FileConfig == nil {
				return errors.NotValidf("file configuration is empty")
			}
			err := c.FileConfig.IsValid()
			if err != nil {
				return errors.Trace(err)
			}
		case ProviderName_GELF:
			if c.GelfConfig == nil {
				return errors.NotValidf("GELF configuration is empty")
			}
			err := c.GelfConfig.IsValid()
			if err != nil {
				return errors.Trace(err)
			}
		case ProviderName_NONE:
			if !*c.EnableStdOut {
				return errors.NotValidf("Provider set to none with StdOut disabled make no sense")
			}
		default:
			return errors.NotValidf("Provider not handled")
		}
	}

	return nil
}