package app

import (
	"fmt"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"
)

type Config struct {
	ListenAddr        string
	PublicURL         *url.URL
	DatabaseDSN       string
	GiteaURL          *url.URL
	GiteaClientID     string
	GiteaClientSecret string
	GiteaPackageOwner string
	GiteaPackageUser  string
	GiteaPackageToken string
	AllowedGiteaUsers map[string]struct{}
	CookieSecret      []byte
	DefaultDuration   time.Duration
	DefaultHostLimit  int
	MaxHostLimit      int
	TrustProxyHeaders bool
}

func LoadConfig() (Config, error) {
	var cfg Config
	var err error

	cfg.ListenAddr = envDefault("TAPM_LISTEN_ADDR", ":8080")
	cfg.DatabaseDSN = os.Getenv("TAPM_DATABASE_DSN")
	cfg.GiteaClientID = os.Getenv("TAPM_GITEA_CLIENT_ID")
	cfg.GiteaClientSecret = os.Getenv("TAPM_GITEA_CLIENT_SECRET")
	cfg.GiteaPackageOwner = envDefault("TAPM_GITEA_PACKAGE_OWNER", "TAI")
	cfg.GiteaPackageUser = os.Getenv("TAPM_GITEA_PACKAGE_USERNAME")
	cfg.GiteaPackageToken = os.Getenv("TAPM_GITEA_PACKAGE_TOKEN")
	cfg.CookieSecret = []byte(os.Getenv("TAPM_COOKIE_SECRET"))

	cfg.PublicURL, err = parseAbsoluteURL("TAPM_PUBLIC_URL")
	if err != nil {
		return cfg, err
	}
	cfg.GiteaURL, err = parseAbsoluteURL("TAPM_GITEA_URL")
	if err != nil {
		return cfg, err
	}

	cfg.DefaultDuration, err = time.ParseDuration(
		envDefault("TAPM_DEFAULT_DURATION", "3h"),
	)
	if err != nil || cfg.DefaultDuration <= 0 {
		return cfg, fmt.Errorf("TAPM_DEFAULT_DURATION must be positive")
	}
	cfg.DefaultHostLimit, err = envInt("TAPM_DEFAULT_HOST_LIMIT", 3)
	if err != nil {
		return cfg, err
	}
	cfg.MaxHostLimit, err = envInt("TAPM_MAX_HOST_LIMIT", 25)
	if err != nil {
		return cfg, err
	}
	if cfg.DefaultHostLimit < 1 || cfg.MaxHostLimit < cfg.DefaultHostLimit {
		return cfg, fmt.Errorf("invalid default or maximum host limit")
	}

	cfg.TrustProxyHeaders, err = strconv.ParseBool(
		envDefault("TAPM_TRUST_PROXY_HEADERS", "false"),
	)
	if err != nil {
		return cfg, fmt.Errorf("TAPM_TRUST_PROXY_HEADERS: %w", err)
	}

	cfg.AllowedGiteaUsers = make(map[string]struct{})
	for _, user := range strings.Split(
		envDefault("TAPM_ALLOWED_GITEA_USERS", "taiadmin"),
		",",
	) {
		user = strings.ToLower(strings.TrimSpace(user))
		if user != "" {
			cfg.AllowedGiteaUsers[user] = struct{}{}
		}
	}

	required := map[string]string{
		"TAPM_DATABASE_DSN":           cfg.DatabaseDSN,
		"TAPM_GITEA_CLIENT_ID":        cfg.GiteaClientID,
		"TAPM_GITEA_CLIENT_SECRET":    cfg.GiteaClientSecret,
		"TAPM_GITEA_PACKAGE_USERNAME": cfg.GiteaPackageUser,
		"TAPM_GITEA_PACKAGE_TOKEN":    cfg.GiteaPackageToken,
	}
	for name, value := range required {
		if strings.TrimSpace(value) == "" {
			return cfg, fmt.Errorf("%s is required", name)
		}
	}
	if len(cfg.CookieSecret) < 32 {
		return cfg, fmt.Errorf("TAPM_COOKIE_SECRET must contain at least 32 bytes")
	}
	if len(cfg.AllowedGiteaUsers) == 0 {
		return cfg, fmt.Errorf("at least one Gitea user must be allowed")
	}

	return cfg, nil
}

func parseAbsoluteURL(name string) (*url.URL, error) {
	raw := os.Getenv(name)
	parsed, err := url.Parse(raw)
	if err != nil || parsed.Scheme != "https" || parsed.Host == "" {
		return nil, fmt.Errorf("%s must be an absolute HTTPS URL", name)
	}
	return parsed, nil
}

func envDefault(name, fallback string) string {
	if value := os.Getenv(name); value != "" {
		return value
	}
	return fallback
}

func envInt(name string, fallback int) (int, error) {
	raw := envDefault(name, strconv.Itoa(fallback))
	value, err := strconv.Atoi(raw)
	if err != nil {
		return 0, fmt.Errorf("%s must be an integer", name)
	}
	return value, nil
}