// Package config provides application configuration using smartconfig.
package config

import (
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"

	"git.eeqj.de/sneak/smartconfig"
	"go.uber.org/fx"
	"sneak.berlin/go/pixa/internal/globals"
	"sneak.berlin/go/pixa/internal/logger"
)

// Default configuration values.
const (
	DefaultPort                       = 8080
	DefaultStateDir                   = "/var/lib/pixa"
	DefaultUpstreamConnectionsPerHost = 20
)

// Params defines dependencies for Config.
type Params struct {
	fx.In
	Globals *globals.Globals
	Logger  *logger.Logger
}

// Config holds application configuration values.
type Config struct {
	Debug           bool
	MaintenanceMode bool
	MetricsPassword string
	MetricsUsername string
	Port            int
	SentryDSN       string
	StateDir        string
	DBURL           string

	// Image proxy settings
	SigningKey                 string   // HMAC signing key for URL signatures
	WhitelistHosts             []string // Hosts that don't require signatures
	AllowHTTP                  bool     // Allow non-TLS upstream (testing only)
	UpstreamConnectionsPerHost int      // Max concurrent connections per upstream host
}

// New creates a new Config instance by loading configuration from file.
func New(_ fx.Lifecycle, params Params) (*Config, error) {
	log := params.Logger.Get()
	name := params.Globals.Appname

	sc, err := loadConfigFile(log, name)
	if err != nil {
		return nil, err
	}

	if sc == nil {
		log.Info("no config file found, using defaults")
	}

	c := &Config{
		Debug:                      getBool(sc, "debug", false),
		MaintenanceMode:            getBool(sc, "maintenance_mode", false),
		Port:                       getInt(sc, "port", DefaultPort),
		StateDir:                   getString(sc, "state_dir", DefaultStateDir),
		SentryDSN:                  getString(sc, "sentry_dsn", ""),
		MetricsUsername:            getString(sc, "metrics.username", ""),
		MetricsPassword:            getString(sc, "metrics.password", ""),
		SigningKey:                 getString(sc, "signing_key", ""),
		WhitelistHosts:             getStringSlice(sc, "whitelist_hosts"),
		AllowHTTP:                  getBool(sc, "allow_http", false),
		UpstreamConnectionsPerHost: getInt(sc, "upstream_connections_per_host", DefaultUpstreamConnectionsPerHost),
	}

	// Build DBURL from StateDir if not explicitly set
	c.DBURL = getString(sc, "db_url", "")
	if c.DBURL == "" {
		c.DBURL = fmt.Sprintf("file:%s/state.sqlite3?_journal_mode=WAL", c.StateDir)
	}

	if c.Debug {
		params.Logger.EnableDebugLogging()
	}

	// Validate required configuration
	if err := c.validate(); err != nil {
		return nil, err
	}

	return c, nil
}

// validate checks that all required configuration values are set.
func (c *Config) validate() error {
	if c.SigningKey == "" {
		return fmt.Errorf("signing_key is required")
	}

	// Minimum key length for security (32 bytes = 256 bits)
	const minKeyLength = 32
	if len(c.SigningKey) < minKeyLength {
		return fmt.Errorf("signing_key must be at least %d characters", minKeyLength)
	}

	return nil
}

// loadConfigFile loads configuration from PIXA_CONFIG_PATH env var or standard locations.
func loadConfigFile(log *slog.Logger, appName string) (*smartconfig.Config, error) {
	// Check for explicit config path from environment
	if envPath := os.Getenv("PIXA_CONFIG_PATH"); envPath != "" {
		sc, err := smartconfig.NewFromConfigPath(envPath)
		if err != nil {
			return nil, fmt.Errorf("failed to load config from %s: %w", envPath, err)
		}

		log.Info("loaded config file", "path", envPath)

		return sc, nil
	}

	// Try loading config from standard locations
	configPaths := []string{
		fmt.Sprintf("/etc/%s/config.yml", appName),
		fmt.Sprintf("/etc/%s/config.yaml", appName),
		filepath.Join(os.Getenv("HOME"), ".config", appName, "config.yml"),
		filepath.Join(os.Getenv("HOME"), ".config", appName, "config.yaml"),
		"config.yml",
		"config.yaml",
	}

	for _, path := range configPaths {
		if _, statErr := os.Stat(path); statErr == nil {
			sc, err := smartconfig.NewFromConfigPath(path)
			if err != nil {
				log.Warn("failed to parse config file", "path", path, "error", err)

				continue
			}

			log.Info("loaded config file", "path", path)

			return sc, nil
		}
	}

	return nil, nil //nolint:nilnil // nil config is valid (use defaults)
}

func getString(sc *smartconfig.Config, key, defaultVal string) string {
	if sc == nil {
		return defaultVal
	}

	val, err := sc.GetString(key)
	if err != nil {
		return defaultVal
	}

	return val
}

func getInt(sc *smartconfig.Config, key string, defaultVal int) int {
	if sc == nil {
		return defaultVal
	}

	val, err := sc.GetInt(key)
	if err != nil {
		return defaultVal
	}

	return val
}

func getBool(sc *smartconfig.Config, key string, defaultVal bool) bool {
	if sc == nil {
		return defaultVal
	}

	val, err := sc.GetBool(key)
	if err != nil {
		return defaultVal
	}

	return val
}

func getStringSlice(sc *smartconfig.Config, key string) []string {
	if sc == nil {
		return nil
	}

	val, ok := sc.Get(key)
	if !ok || val == nil {
		return nil
	}

	// Handle YAML list format
	if slice, ok := val.([]interface{}); ok {
		result := make([]string, 0, len(slice))
		for _, item := range slice {
			if str, ok := item.(string); ok {
				trimmed := strings.TrimSpace(str)
				if trimmed != "" {
					result = append(result, trimmed)
				}
			}
		}

		return result
	}

	// Fall back to comma-separated string for backwards compatibility
	if str, ok := val.(string); ok && str != "" {
		parts := strings.Split(str, ",")
		result := make([]string, 0, len(parts))

		for _, part := range parts {
			trimmed := strings.TrimSpace(part)
			if trimmed != "" {
				result = append(result, trimmed)
			}
		}

		return result
	}

	return nil
}