package config

import (
	"flag"
	"fmt"
	"os"

	"github.com/caarlos0/env/v9"
	"gopkg.in/yaml.v3"
)

type AppConfig struct {
	Name        string     `yaml:"name" env:"APP_NAME" envDefault:"go-http-server-with-otel"`
	Environment string     `yaml:"environment" env:"APP_ENVIRONMENT" envDefault:"development"`
	Version     string     `yaml:"version" env:"APP_VERSION"`
	Logging     LogConfig  `yaml:"logging"`
	HTTP        HTTPConfig `yaml:"http"`
	OTEL        OTELConfig `yaml:"otel"`
}

type LogConfig struct {
	Enabled bool   `yaml:"enabled" env:"APP_LOGGING_ENABLED" envDefault:"true"`
	Level   string `yaml:"level" env:"APP_LOGGING_LEVEL" envDefault:"info"`
	Format  string `yaml:"format" env:"APP_LOGGING_FORMAT" envDefault:"json"`
}

type HTTPConfig struct {
	Listen         string `yaml:"listen" env:"APP_HTTP_LISTEN" envDefault:"127.0.0.1:8080"`
	RequestTimeout int    `yaml:"request_timeout" env:"APP_HTTP_REQUEST_TIMEOUT" envDefault:"30"`
}

type OTELConfig struct {
	Enabled           bool   `yaml:"enabled" env:"APP_OTEL_ENABLED" envDefault:"true"`
	PrometheusEnabled bool   `yaml:"prometheus_enabled" env:"APP_OTEL_PROMETHEUS_ENABLED" envDefault:"true"`
	PrometheusPath    string `yaml:"prometheus_path" env:"APP_OTEL_PROMETHEUS_PATH" envDefault:"/metrics"`
}

// Calling this will try to load from config if -config is
// provided, otherwise will return *AppConfig with defaults,
// performing any environment substitutions
func LoadConfig() (*AppConfig, error) {
	configPath := flag.String("config", "", "Path to the configuration file")
	flag.Parse()

	return loadConfig(*configPath)
}

func loadConfig(configPath string) (*AppConfig, error) {
	cfg := AppConfig{}

	if configPath != "" {
		file, err := os.Open(configPath)
		if err != nil {
			return nil, fmt.Errorf("could not open config file: %w", err)
		}
		defer file.Close()

		decoder := yaml.NewDecoder(file)
		if err := decoder.Decode(&cfg); err != nil {
			return nil, fmt.Errorf("could not decode config file: %w", err)
		}
	}

	if err := env.Parse(&cfg); err != nil {
		return nil, fmt.Errorf("could not parse environment variables: %w", err)
	}

	return &cfg, nil
}