// Package config loads tomswallapi runtime configuration from the environment.
package config

import (
	"fmt"
	"net/url"
	"os"
)

// Config holds all runtime configuration, sourced from environment variables.
type Config struct {
	ListenAddr string

	DBHost     string
	DBPort     string
	DBUser     string
	DBPassword string
	DBName     string
	DBSSLMode  string

	// WriteToken guards all mutating API endpoints (used by the Terraform provider).
	WriteToken string
	// AgentToken guards the per-device config endpoint (used by tomswall agents).
	AgentToken string

	// IPLocateAPIKey is used to expand ASN address groups into prefixes.
	IPLocateAPIKey string
}

// Load reads configuration from the environment, applying defaults.
func Load() (*Config, error) {
	c := &Config{
		ListenAddr:     env("TOMSWALLAPI_LISTEN_ADDR", ":8000"),
		DBHost:         env("TOMSWALLAPI_DB_HOST", "localhost"),
		DBPort:         env("TOMSWALLAPI_DB_PORT", "5432"),
		DBUser:         env("TOMSWALLAPI_DB_USER", "tomswallapi"),
		DBPassword:     os.Getenv("TOMSWALLAPI_DB_PASSWORD"),
		DBName:         env("TOMSWALLAPI_DB_NAME", "tomswallapi"),
		DBSSLMode:      env("TOMSWALLAPI_DB_SSLMODE", "disable"),
		WriteToken:     os.Getenv("TOMSWALLAPI_WRITE_TOKEN"),
		AgentToken:     os.Getenv("TOMSWALLAPI_AGENT_TOKEN"),
		IPLocateAPIKey: os.Getenv("TOMSWALLAPI_IPLOCATE_API_KEY"),
	}
	if c.DBName == "" {
		return nil, fmt.Errorf("TOMSWALLAPI_DB_NAME must not be empty")
	}
	return c, nil
}

// DatabaseDSN builds a libpq-style connection string.
func (c *Config) DatabaseDSN() string {
	u := url.URL{
		Scheme: "postgres",
		User:   url.UserPassword(c.DBUser, c.DBPassword),
		Host:   fmt.Sprintf("%s:%s", c.DBHost, c.DBPort),
		Path:   c.DBName,
	}
	q := u.Query()
	q.Set("sslmode", c.DBSSLMode)
	u.RawQuery = q.Encode()
	return u.String()
}

func env(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}