// Package environment provides strict parsing for runtime configuration.
package environment

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

// String returns a trimmed environment value or fallback when it is empty.
func String(name, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(name)); value != "" {
		return value
	}
	return fallback
}

// Required returns a non-empty environment value.
func Required(name string) (string, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return "", fmt.Errorf("%s must be set", name)
	}
	return value, nil
}

// Int parses an integer environment value.
func Int(name string, fallback int) (int, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return fallback, nil
	}
	parsed, err := strconv.Atoi(value)
	if err != nil {
		return 0, fmt.Errorf("%s must be an integer: %w", name, err)
	}
	return parsed, nil
}

// Float parses a floating-point environment value.
func Float(name string, fallback float64) (float64, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return fallback, nil
	}
	parsed, err := strconv.ParseFloat(value, 64)
	if err != nil {
		return 0, fmt.Errorf("%s must be a number: %w", name, err)
	}
	return parsed, nil
}

// Bool parses a boolean environment value.
func Bool(name string, fallback bool) (bool, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return fallback, nil
	}
	parsed, err := strconv.ParseBool(value)
	if err != nil {
		return false, fmt.Errorf("%s must be a boolean: %w", name, err)
	}
	return parsed, nil
}

// Duration parses a Go duration environment value.
func Duration(name string, fallback time.Duration) (time.Duration, error) {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return fallback, nil
	}
	parsed, err := time.ParseDuration(value)
	if err != nil {
		return 0, fmt.Errorf("%s must be a duration: %w", name, err)
	}
	return parsed, nil
}

// CSV returns non-empty, trimmed comma-separated values.
func CSV(name string) []string {
	value := strings.TrimSpace(os.Getenv(name))
	if value == "" {
		return nil
	}
	parts := strings.Split(value, ",")
	result := make([]string, 0, len(parts))
	for _, part := range parts {
		if part = strings.TrimSpace(part); part != "" {
			result = append(result, part)
		}
	}
	return result
}