// Package config loads application configuration from environment variables.
package config

import (
	"fmt"
	"os"
	"strconv"
	"time"

	"github.com/joho/godotenv"
)

type Config struct {
	Database DatabaseConfig
	Redis    RedisConfig
	JWT      JWTConfig
	Server   ServerConfig
	Seed     SeedConfig
	Media    MediaConfig
}

type DatabaseConfig struct {
	URL string
}

type RedisConfig struct {
	URL string
}

type JWTConfig struct {
	Secret     string
	AccessTTL  time.Duration
	RefreshTTL time.Duration
}

type ServerConfig struct {
	Port         string
	GinMode      string
	CORSOrigin   string
	CookieSecure bool
}

type SeedConfig struct {
	AdminEmail    string
	AdminPassword string
}

// MediaConfig configures the pluggable media storage backend. Driver
// selects "local" (files on disk, served via /uploads) or "s3" (any
// S3-compatible object store). Only the fields relevant to the selected
// driver need to be set.
type MediaConfig struct {
	Driver       string
	MaxUploadMB  int64
	LocalDir     string
	LocalBaseURL string

	S3Bucket        string
	S3Region        string
	S3Endpoint      string
	S3AccessKeyID   string
	S3SecretKey     string
	S3UsePathStyle  bool
	S3PublicBaseURL string
}

func Load() (*Config, error) {
	// The .env file lives at the repo root (next to docker-compose.yml),
	// but `go run` is commonly invoked from inside backend/. Try both so
	// either working directory picks it up; missing files are ignored.
	_ = godotenv.Load(".env")
	_ = godotenv.Load("../.env")

	accessMinutes, err := strconv.Atoi(getEnv("ACCESS_TOKEN_TTL_MINUTES", "15"))
	if err != nil {
		return nil, fmt.Errorf("invalid ACCESS_TOKEN_TTL_MINUTES: %w", err)
	}
	refreshHours, err := strconv.Atoi(getEnv("REFRESH_TOKEN_TTL_HOURS", "168"))
	if err != nil {
		return nil, fmt.Errorf("invalid REFRESH_TOKEN_TTL_HOURS: %w", err)
	}

	secret := os.Getenv("JWT_SECRET")
	if secret == "" || secret == "change-me-to-a-long-random-secret" {
		return nil, fmt.Errorf("JWT_SECRET must be set to a strong, unique value")
	}

	dbURL := os.Getenv("DATABASE_URL")
	if dbURL == "" {
		return nil, fmt.Errorf("DATABASE_URL must be set")
	}
	redisURL := os.Getenv("REDIS_URL")
	if redisURL == "" {
		return nil, fmt.Errorf("REDIS_URL must be set")
	}

	ginMode := getEnv("GIN_MODE", "debug")
	cookieSecure, err := strconv.ParseBool(getEnv("COOKIE_SECURE", strconv.FormatBool(ginMode != "debug")))
	if err != nil {
		return nil, fmt.Errorf("invalid COOKIE_SECURE: %w", err)
	}

	mediaDriver := getEnv("MEDIA_STORAGE_DRIVER", "local")
	if mediaDriver != "local" && mediaDriver != "s3" {
		return nil, fmt.Errorf("invalid MEDIA_STORAGE_DRIVER %q: must be \"local\" or \"s3\"", mediaDriver)
	}
	maxUploadMB, err := strconv.ParseInt(getEnv("MEDIA_MAX_UPLOAD_MB", "10"), 10, 64)
	if err != nil {
		return nil, fmt.Errorf("invalid MEDIA_MAX_UPLOAD_MB: %w", err)
	}
	s3UsePathStyle, err := strconv.ParseBool(getEnv("S3_USE_PATH_STYLE", "false"))
	if err != nil {
		return nil, fmt.Errorf("invalid S3_USE_PATH_STYLE: %w", err)
	}
	if mediaDriver == "s3" {
		for _, key := range []string{"S3_BUCKET", "S3_REGION", "S3_ACCESS_KEY_ID", "S3_SECRET_ACCESS_KEY"} {
			if os.Getenv(key) == "" {
				return nil, fmt.Errorf("%s must be set when MEDIA_STORAGE_DRIVER=s3", key)
			}
		}
	}

	return &Config{
		Database: DatabaseConfig{
			URL: dbURL,
		},
		Redis: RedisConfig{
			URL: redisURL,
		},
		JWT: JWTConfig{
			Secret:     secret,
			AccessTTL:  time.Duration(accessMinutes) * time.Minute,
			RefreshTTL: time.Duration(refreshHours) * time.Hour,
		},
		Server: ServerConfig{
			Port:         getEnv("PORT", "8080"),
			GinMode:      ginMode,
			CORSOrigin:   getEnv("CORS_ORIGIN", "http://localhost:5173"),
			CookieSecure: cookieSecure,
		},
		Seed: SeedConfig{
			AdminEmail:    os.Getenv("SEED_ADMIN_EMAIL"),
			AdminPassword: os.Getenv("SEED_ADMIN_PASSWORD"),
		},
		Media: MediaConfig{
			Driver:          mediaDriver,
			MaxUploadMB:     maxUploadMB,
			LocalDir:        getEnv("MEDIA_LOCAL_DIR", "./uploads"),
			LocalBaseURL:    getEnv("MEDIA_LOCAL_BASE_URL", "http://localhost:8080/uploads"),
			S3Bucket:        os.Getenv("S3_BUCKET"),
			S3Region:        os.Getenv("S3_REGION"),
			S3Endpoint:      os.Getenv("S3_ENDPOINT"),
			S3AccessKeyID:   os.Getenv("S3_ACCESS_KEY_ID"),
			S3SecretKey:     os.Getenv("S3_SECRET_ACCESS_KEY"),
			S3UsePathStyle:  s3UsePathStyle,
			S3PublicBaseURL: os.Getenv("S3_PUBLIC_BASE_URL"),
		},
	}, nil
}

func getEnv(key, fallback string) string {
	if v, ok := os.LookupEnv(key); ok && v != "" {
		return v
	}
	return fallback
}