package config

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

type envReader struct {
	err error
}

func (reader *envReader) fail(name string, err error) {
	if reader.err == nil {
		reader.err = fmt.Errorf("%s: %w", name, err)
	}
}

func (reader *envReader) text(name, fallback string) string {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return fallback
	}
	return value
}

func (reader *envReader) boolean(name string, fallback bool) bool {
	raw := reader.text(name, "")
	if raw == "" {
		return fallback
	}
	value, err := strconv.ParseBool(raw)
	if err != nil {
		reader.fail(name, err)
		return fallback
	}
	return value
}

func (reader *envReader) integer(name string, fallback int) int {
	raw := reader.text(name, "")
	if raw == "" {
		return fallback
	}
	value, err := strconv.Atoi(raw)
	if err != nil {
		reader.fail(name, err)
		return fallback
	}
	return value
}

func (reader *envReader) ports(name, fallback string) []uint16 {
	raw := reader.text(name, fallback)
	if raw == "*" {
		return nil
	}

	var ports []uint16
	for _, part := range strings.Split(raw, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		value, err := strconv.ParseUint(part, 10, 16)
		if err != nil || value == 0 {
			reader.fail(name, fmt.Errorf("invalid port %q", part))
			return nil
		}
		ports = append(ports, uint16(value))
	}

	if len(ports) == 0 {
		reader.fail(name, fmt.Errorf("no ports listed, use * to allow any port"))
	}
	return ports
}