package config

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"

	"github.com/pelletier/go-toml"
)

var ErrNotFound = errors.New("no config file found")

type Config struct {
	ListenAddr string `toml:"ListenAddr"`
	LogLevel   string `toml:"LogLevel"`
}

type InvalidValueError struct {
	Key string
}

func (ive *InvalidValueError) Error() string {
	return fmt.Sprintf("invalid value: config key %s has invalid value", ive.Key)
}

func FromReader(r io.Reader) (*Config, error) {
	var c Config
	// Set some defaults
	c.ListenAddr = ":5566"
	c.LogLevel = "INFO"

	decoder := toml.NewDecoder(r)
	if err := decoder.Decode(&c); err != nil {
		return nil, fmt.Errorf("error parsing config file: %w", err)
	}

	return &c, c.Verify()
}

func (c *Config) Verify() error {
	// Check that LogLevel is valid
	switch c.LogLevel {
	case "DEBUG", "INFO", "WARN", "ERROR":
	default:
		return &InvalidValueError{Key: "LogLevel"}
	}
	return nil
}

func (c *Config) UpdateFromEnv() error {
	if loglevel, found := os.LookupEnv("DOGTAMER_LOGLEVEL"); found {
		c.LogLevel = loglevel
	}
	if listenAddr, found := os.LookupEnv("DOGTAMER_LISTENADDR"); found {
		c.ListenAddr = listenAddr
	}

	return c.Verify()
}

func FromFile(path string) (*Config, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("Error opening config file: %w", err)
	}

	return FromReader(f)
}

func FromDefaultLocations(path string) (*Config, error) {
	defaultLocations := []string{
		"dogtamer.toml",
		"/etc/dogtamer.toml",
	}
	baseConfigDir, err := os.UserConfigDir()
	if err == nil {
		userConfigFile := filepath.Join(baseConfigDir, "dogtamer", "dogtamer.toml")
		defaultLocations = append(defaultLocations, userConfigFile)
	}

	for _, fname := range defaultLocations {
		if _, err := os.Stat(fname); os.IsNotExist(err) {
			continue
		}

		cfg, err := FromFile(fname)
		if err != nil {
			continue

		}

		return cfg, cfg.UpdateFromEnv()
	}

	return nil, ErrNotFound
}