package config

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"os"
	"strings"

	"git.ipao.vip/rogee/go-sip/internal/tenant"
)

// DispatcherEnvironment contains only deployment-owned startup values. The
// SaaS read secret is never a task/AI setting and must not be logged.
type DispatcherEnvironment struct {
	DispatcherID string
	SecretKey    string
	SaaSBaseURL  string
	RabbitMQURL  string
	SQLitePath   string
}

// LoadDispatcherEnvironment is pure inspection: it opens no database, queue or
// network connection. The current executable accepts only isolated Mock mode.
func LoadDispatcherEnvironment(mode string) (DispatcherEnvironment, error) {
	if mode != "mock" {
		return DispatcherEnvironment{}, errors.New("Dispatcher accepts only isolated Mock mode")
	}
	get := func(name string) (string, error) {
		value := os.Getenv(name)
		if strings.TrimSpace(value) == "" {
			return "", fmt.Errorf("%s is required", name)
		}
		return value, nil
	}
	var settings DispatcherEnvironment
	var err error
	if settings.DispatcherID, err = get("DISPATCHER_ID"); err != nil {
		return DispatcherEnvironment{}, err
	}
	if tenant.ValidateDispatcherID(settings.DispatcherID) != nil {
		return DispatcherEnvironment{}, errors.New("DISPATCHER_ID must be a canonical UUID v4")
	}
	if settings.SecretKey, err = get("DISPATCHER_SECRET_KEY"); err != nil {
		return DispatcherEnvironment{}, err
	}
	if settings.SaaSBaseURL, err = get("SAAS_BASE_URL"); err != nil {
		return DispatcherEnvironment{}, err
	}
	if !localEndpoint(settings.SaaSBaseURL, "http", "https") {
		return DispatcherEnvironment{}, errors.New("SAAS_BASE_URL must name a local Mock HTTP endpoint")
	}
	if settings.RabbitMQURL, err = get("RABBITMQ_URL"); err != nil {
		return DispatcherEnvironment{}, err
	}
	if !localEndpoint(settings.RabbitMQURL, "amqp", "amqps") {
		return DispatcherEnvironment{}, errors.New("RABBITMQ_URL must name a local Mock AMQP endpoint")
	}
	if settings.SQLitePath, err = get("DISPATCHER_SQLITE_PATH"); err != nil {
		return DispatcherEnvironment{}, err
	}
	return settings, nil
}

func localEndpoint(raw string, schemes ...string) bool {
	parsed, err := url.Parse(raw)
	if err != nil || parsed.Hostname() == "" || parsed.Opaque != "" || parsed.Fragment != "" || parsed.RawQuery != "" {
		return false
	}
	validScheme := false
	for _, scheme := range schemes {
		validScheme = validScheme || parsed.Scheme == scheme
	}
	if !validScheme {
		return false
	}
	host := parsed.Hostname()
	if strings.EqualFold(host, "localhost") {
		return true
	}
	ip := net.ParseIP(host)
	return ip != nil && ip.IsLoopback()
}