// Package config loads and validates the notifier service's configuration
// (notifiers, queue, auth, retention, and related settings) from files,
// environment variables, and defaults via viper.
package config

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

	"github.com/igodwin/notifier/internal/domain"
	"github.com/igodwin/notifier/internal/notifier"
	"github.com/spf13/viper"
)

// Config represents the application configuration
type Config struct {
	Server      ServerConfig                `mapstructure:"server"`
	Queue       domain.QueueConfig          `mapstructure:"queue"`
	Notifiers   NotifiersConfig             `mapstructure:"notifiers"`
	Logging     LoggingConfig               `mapstructure:"logging"`
	Metrics     MetricsConfig               `mapstructure:"metrics"`
	HealthCheck HealthCheckConfig           `mapstructure:"health_check"`
	Auth        AuthConfig                  `mapstructure:"auth"`
	CORS        CORSConfig                  `mapstructure:"cors"`
	Retention   NotificationRetentionConfig `mapstructure:"retention"`
	ConfigFile  string                      `mapstructure:"-"` // Path to config file used (not from config)
}

// ServerConfig contains server configuration
type ServerConfig struct {
	GRPCPort int       `mapstructure:"grpc_port"`
	RESTPort int       `mapstructure:"rest_port"`
	Host     string    `mapstructure:"host"`
	Mode     string    `mapstructure:"mode"` // "both", "grpc", "rest"
	TLS      TLSConfig `mapstructure:"tls"`
}

// TLSConfig enables TLS on the REST and gRPC listeners. When disabled the
// servers speak plaintext, which is only appropriate behind a TLS-terminating
// gateway or service mesh.
type TLSConfig struct {
	Enabled  bool   `mapstructure:"enabled"`
	CertFile string `mapstructure:"cert_file"`
	KeyFile  string `mapstructure:"key_file"`
}

// NotifiersConfig contains configuration for all notifier types
type NotifiersConfig struct {
	SMTP   map[string]*notifier.SMTPConfig  `mapstructure:"smtp"`
	Slack  map[string]*notifier.SlackConfig `mapstructure:"slack"`
	Ntfy   map[string]*notifier.NtfyConfig  `mapstructure:"ntfy"`
	Stdout bool                             `mapstructure:"stdout"` // Enable stdout notifier
}

// LoggingConfig contains logging configuration
type LoggingConfig struct {
	Level      string `mapstructure:"level"`       // debug, info, warn, error
	Format     string `mapstructure:"format"`      // json, text
	OutputPath string `mapstructure:"output_path"` // stdout, stderr, or file path
}

// MetricsConfig contains metrics/observability configuration
type MetricsConfig struct {
	Enabled           bool   `mapstructure:"enabled"`
	Port              int    `mapstructure:"port"`
	Path              string `mapstructure:"path"`
	PrometheusEnabled bool   `mapstructure:"prometheus_enabled"`
}

// HealthCheckConfig contains health check configuration
type HealthCheckConfig struct {
	Enabled  bool   `mapstructure:"enabled"`
	Port     int    `mapstructure:"port"`
	Path     string `mapstructure:"path"`
	Interval int    `mapstructure:"interval"` // seconds
}

// AuthConfig contains authentication and authorization configuration
type AuthConfig struct {
	Enabled          bool           `mapstructure:"enabled"`            // Enable API key authentication
	DefaultRateLimit int            `mapstructure:"default_rate_limit"` // Default rate limit in requests/minute (0 = unlimited)
	Database         DatabaseConfig `mapstructure:"database"`           // Database configuration for persistent key storage
	Bootstrap        BootstrapConf  `mapstructure:"bootstrap"`          // Bootstrap admin key configuration
}

// DatabaseConfig contains database connection configuration
type DatabaseConfig struct {
	URL string `mapstructure:"url"` // Database connection URL (e.g., "postgresql://user:pass@host:5432/db")
}

// BootstrapConf contains configuration for bootstrap admin key creation
type BootstrapConf struct {
	Enabled              bool   `mapstructure:"enabled"`                // Enable bootstrap on startup
	AdminKeyFileName     string `mapstructure:"admin_key_file"`         // File to save the generated admin key
	PrintToStdout        bool   `mapstructure:"print_to_stdout"`        // Print admin key to stdout (only for setup)
	KubernetesSecretName string `mapstructure:"kubernetes_secret_name"` // Kubernetes secret name (e.g., "notifier-admin-key")
	KubernetesSecretKey  string `mapstructure:"kubernetes_secret_key"`  // Key within secret (e.g., "admin-key")
}

// CORSConfig contains CORS (Cross-Origin Resource Sharing) configuration
type CORSConfig struct {
	// AllowedOrigins is a whitelist of allowed origins (e.g., ["https://example.com", "https://app.example.com"])
	// Wildcards (*) are NOT supported for security reasons - you must specify exact origins
	AllowedOrigins []string `mapstructure:"allowed_origins"`

	// AllowedMethods is a list of allowed HTTP methods (e.g., ["GET", "POST", "OPTIONS", "DELETE"])
	AllowedMethods []string `mapstructure:"allowed_methods"`

	// AllowedHeaders is a list of allowed HTTP headers (e.g., ["Content-Type", "Authorization"])
	AllowedHeaders []string `mapstructure:"allowed_headers"`

	// AllowCredentials indicates whether credentials (cookies, authorization headers) are allowed
	// Note: When true, AllowedOrigins must NOT contain wildcards (enforced by validation)
	AllowCredentials bool `mapstructure:"allow_credentials"`

	// MaxAge is the duration in seconds that browsers can cache preflight responses
	MaxAge int `mapstructure:"max_age"`
}

// NotificationRetentionConfig contains notification retention and cleanup configuration
type NotificationRetentionConfig struct {
	Enabled        bool   `mapstructure:"enabled"`         // Enable automatic cleanup
	TTL            string `mapstructure:"ttl"`             // Time-to-live duration (e.g., "168h" for 7 days)
	CheckFrequency string `mapstructure:"check_frequency"` // How often to run cleanup (e.g., "1h")
	MaxSize        int    `mapstructure:"max_size"`        // Maximum number of notifications to keep
}

// Load loads configuration from file and environment variables
// Returns the loaded config and the path to the config file that was used
func Load(configPath string) (*Config, error) {
	v := viper.New()

	// Set default values
	setDefaults(v)

	// Configure viper to look for config.yaml
	v.SetConfigName("config")
	v.SetConfigType("yaml")

	// Add config search paths
	if configPath != "" {
		v.AddConfigPath(configPath)
	}

	v.AddConfigPath(".")
	v.AddConfigPath("./config")
	v.AddConfigPath("/etc/notifier")

	// Add $HOME/.notifier if HOME is set
	if home := os.Getenv("HOME"); home != "" {
		v.AddConfigPath(filepath.Join(home, ".notifier"))
	}

	// Environment variable support
	v.SetEnvPrefix("NOTIFIER")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	v.AutomaticEnv()

	// Read config file
	var configErr error
	if err := v.ReadInConfig(); err != nil {
		// Config file is optional if environment variables are set
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			return nil, fmt.Errorf("failed to read config file: %w", err)
		}
		configErr = err
	}

	var config Config
	if err := v.Unmarshal(&config); err != nil {
		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
	}

	// Store which config file was used
	config.ConfigFile = v.ConfigFileUsed()
	if config.ConfigFile == "" {
		if configErr != nil {
			config.ConfigFile = "no config file found (using defaults and environment variables)"
		} else {
			config.ConfigFile = "using defaults and environment variables"
		}
	}

	// Validate configuration
	if err := config.Validate(); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	return &config, nil
}

// setDefaults sets default configuration values
func setDefaults(v *viper.Viper) {
	// Server defaults
	v.SetDefault("server.grpc_port", 50051)
	v.SetDefault("server.rest_port", 8080)
	v.SetDefault("server.host", "0.0.0.0")
	v.SetDefault("server.mode", "both")

	// Queue defaults
	v.SetDefault("queue.type", "local")
	v.SetDefault("queue.max_size", 10000)
	v.SetDefault("queue.worker_count", 10)
	v.SetDefault("queue.retry_attempts", 3)
	v.SetDefault("queue.retry_backoff", "exponential")

	// Local queue defaults
	v.SetDefault("queue.local.buffer_size", 1000)
	v.SetDefault("queue.local.persist_to_disk", false)

	// Logging defaults
	v.SetDefault("logging.level", "info")
	v.SetDefault("logging.format", "json")
	v.SetDefault("logging.output_path", "stdout")

	// Metrics defaults
	v.SetDefault("metrics.enabled", true)
	v.SetDefault("metrics.port", 9090)
	v.SetDefault("metrics.path", "/metrics")
	v.SetDefault("metrics.prometheus_enabled", true)

	// Health check defaults
	v.SetDefault("health_check.enabled", true)
	v.SetDefault("health_check.port", 8081)
	v.SetDefault("health_check.path", "/health")
	v.SetDefault("health_check.interval", 30)

	// Auth defaults
	v.SetDefault("auth.enabled", false)                                         // Authentication disabled by default
	v.SetDefault("auth.default_rate_limit", 100)                                // 100 requests per minute default
	v.SetDefault("auth.bootstrap.enabled", false)                               // Bootstrap disabled by default
	v.SetDefault("auth.bootstrap.admin_key_file", "")                           // No file by default
	v.SetDefault("auth.bootstrap.print_to_stdout", false)                       // Don't print to stdout by default
	v.SetDefault("auth.bootstrap.kubernetes_secret_name", "notifier-admin-key") // Default secret name
	v.SetDefault("auth.bootstrap.kubernetes_secret_key", "admin-key")           // Default secret key

	// CORS defaults - secure by default (no origins allowed)
	v.SetDefault("cors.allowed_origins", []string{})                                   // Empty by default - must be explicitly configured
	v.SetDefault("cors.allowed_methods", []string{"GET", "POST", "OPTIONS", "DELETE"}) // Standard REST methods
	v.SetDefault("cors.allowed_headers", []string{"Content-Type", "Authorization"})    // Common headers
	v.SetDefault("cors.allow_credentials", false)                                      // Credentials disabled by default
	v.SetDefault("cors.max_age", 3600)                                                 // 1 hour cache for preflight

	// Retention defaults
	v.SetDefault("retention.enabled", true)         // Enable retention cleanup by default
	v.SetDefault("retention.ttl", "168h")           // 7 days default
	v.SetDefault("retention.check_frequency", "1h") // Check every hour
	v.SetDefault("retention.max_size", 100000)      // Maximum 100,000 notifications

	// Notifier defaults
	v.SetDefault("notifiers.stdout", true)
	// Note: SMTP, Slack, and Ntfy now use named instances (maps)
	// so we don't set defaults at the type level
}

// Validate validates the configuration
func (c *Config) Validate() error {
	// Validate server config
	if c.Server.GRPCPort < 1 || c.Server.GRPCPort > 65535 {
		return fmt.Errorf("invalid gRPC port: %d", c.Server.GRPCPort)
	}

	if c.Server.RESTPort < 1 || c.Server.RESTPort > 65535 {
		return fmt.Errorf("invalid REST port: %d", c.Server.RESTPort)
	}

	validModes := map[string]bool{"both": true, "grpc": true, "rest": true}
	if !validModes[c.Server.Mode] {
		return fmt.Errorf("invalid server mode: %s (must be both, grpc, or rest)", c.Server.Mode)
	}

	if c.Server.TLS.Enabled {
		if c.Server.TLS.CertFile == "" || c.Server.TLS.KeyFile == "" {
			return fmt.Errorf("server.tls.enabled requires both cert_file and key_file")
		}
	}

	// Validate queue config
	validQueueTypes := map[string]bool{"local": true, "kafka": true}
	if !validQueueTypes[c.Queue.Type] {
		return fmt.Errorf("invalid queue type: %s (must be local or kafka)", c.Queue.Type)
	}

	if c.Queue.Type == "kafka" && c.Queue.Kafka == nil {
		return fmt.Errorf("kafka queue type selected but no kafka configuration provided")
	}

	// Validate at least one notifier is configured
	if !c.HasAnyNotifier() {
		return fmt.Errorf("at least one notifier must be configured")
	}

	// Validate CORS configuration
	if err := c.validateCORS(); err != nil {
		return err
	}

	return nil
}

// validateCORS validates the CORS configuration
func (c *Config) validateCORS() error {
	// Check for wildcard in allowed origins (security vulnerability)
	for _, origin := range c.CORS.AllowedOrigins {
		if origin == "*" {
			return fmt.Errorf("wildcard (*) is not allowed in CORS allowed_origins for security reasons - specify exact origins instead")
		}
		// Check for invalid origin format
		if origin != "" && !strings.HasPrefix(origin, "http://") && !strings.HasPrefix(origin, "https://") {
			return fmt.Errorf("invalid origin format: %s - origins must start with http:// or https://", origin)
		}
	}

	// Validate that credentials are not used with empty origin list (pointless configuration)
	if c.CORS.AllowCredentials && len(c.CORS.AllowedOrigins) == 0 {
		return fmt.Errorf("allow_credentials is enabled but no origins are allowed - this configuration is ineffective")
	}

	return nil
}

// HasAnyNotifier checks if at least one notifier is configured
func (c *Config) HasAnyNotifier() bool {
	return c.Notifiers.Stdout ||
		len(c.Notifiers.SMTP) > 0 ||
		len(c.Notifiers.Slack) > 0 ||
		len(c.Notifiers.Ntfy) > 0
}

// GetEnabledNotifiers returns a list of enabled notifier types
func (c *Config) GetEnabledNotifiers() []domain.NotificationType {
	var enabled []domain.NotificationType

	if c.Notifiers.Stdout {
		enabled = append(enabled, domain.TypeStdout)
	}
	if len(c.Notifiers.SMTP) > 0 {
		enabled = append(enabled, domain.TypeEmail)
	}
	if len(c.Notifiers.Slack) > 0 {
		enabled = append(enabled, domain.TypeSlack)
	}
	if len(c.Notifiers.Ntfy) > 0 {
		enabled = append(enabled, domain.TypeNtfy)
	}

	return enabled
}

// Sanitize returns a sanitized copy of the config with sensitive data redacted
func (c *Config) Sanitize() map[string]interface{} {
	sanitized := map[string]interface{}{
		"config_file": c.ConfigFile,
		"server": map[string]interface{}{
			"grpc_port": c.Server.GRPCPort,
			"rest_port": c.Server.RESTPort,
			"host":      c.Server.Host,
			"mode":      c.Server.Mode,
		},
		"queue": map[string]interface{}{
			"type":           c.Queue.Type,
			"worker_count":   c.Queue.WorkerCount,
			"retry_attempts": c.Queue.RetryAttempts,
		},
		"logging": map[string]interface{}{
			"level":  c.Logging.Level,
			"format": c.Logging.Format,
		},
		"metrics": map[string]interface{}{
			"enabled": c.Metrics.Enabled,
			"port":    c.Metrics.Port,
		},
		"health_check": map[string]interface{}{
			"enabled": c.HealthCheck.Enabled,
			"port":    c.HealthCheck.Port,
		},
	}

	// Sanitize notifiers
	notifiers := map[string]interface{}{
		"stdout": c.Notifiers.Stdout,
	}

	// Sanitize SMTP configs
	if len(c.Notifiers.SMTP) > 0 {
		smtpAccounts := make(map[string]interface{})
		for name, cfg := range c.Notifiers.SMTP {
			smtpAccounts[name] = map[string]interface{}{
				"host":      cfg.Host,
				"port":      cfg.Port,
				"username":  cfg.Username,
				"password":  "***REDACTED***",
				"from":      cfg.From,
				"from_name": cfg.FromName,
				"use_tls":   cfg.UseTLS,
				"default":   cfg.Default,
			}
		}
		notifiers["smtp"] = smtpAccounts
	}

	// Sanitize Slack configs
	if len(c.Notifiers.Slack) > 0 {
		slackAccounts := make(map[string]interface{})
		for name, cfg := range c.Notifiers.Slack {
			slackAccounts[name] = map[string]interface{}{
				"webhook_url": "***REDACTED***",
				"token":       "***REDACTED***",
				"username":    cfg.Username,
				"icon_emoji":  cfg.IconEmoji,
				"default":     cfg.Default,
			}
		}
		notifiers["slack"] = slackAccounts
	}

	// Sanitize Ntfy configs
	if len(c.Notifiers.Ntfy) > 0 {
		ntfyAccounts := make(map[string]interface{})
		for name, cfg := range c.Notifiers.Ntfy {
			ntfyAccounts[name] = map[string]interface{}{
				"server_url":    cfg.ServerURL,
				"token":         "***REDACTED***",
				"username":      cfg.Username,
				"password":      "***REDACTED***",
				"default_topic": cfg.DefaultTopic,
				"default":       cfg.Default,
			}
		}
		notifiers["ntfy"] = ntfyAccounts
	}

	sanitized["notifiers"] = notifiers

	// Sanitize auth config
	sanitized["auth"] = map[string]interface{}{
		"enabled": c.Auth.Enabled,
		"database": map[string]interface{}{
			"url": SanitizeDatabaseURL(c.Auth.Database.URL),
		},
		"bootstrap": map[string]interface{}{
			"enabled":                c.Auth.Bootstrap.Enabled,
			"admin_key_file":         c.Auth.Bootstrap.AdminKeyFileName,
			"print_to_stdout":        c.Auth.Bootstrap.PrintToStdout,
			"kubernetes_secret_name": c.Auth.Bootstrap.KubernetesSecretName,
			"kubernetes_secret_key":  c.Auth.Bootstrap.KubernetesSecretKey,
		},
	}

	// Sanitize retention config
	sanitized["retention"] = map[string]interface{}{
		"enabled":         c.Retention.Enabled,
		"ttl":             c.Retention.TTL,
		"check_frequency": c.Retention.CheckFrequency,
		"max_size":        c.Retention.MaxSize,
	}

	return sanitized
}

// SanitizeDatabaseURL redacts the password from a database connection URL
// Handles formats like: postgresql://user:password@host:port/database
// Also handles passwords containing @ characters by finding the last @
func SanitizeDatabaseURL(dbURL string) string {
	if dbURL == "" {
		return ""
	}

	// Find the protocol (e.g., "postgresql://", "mysql://")
	protocolIdx := strings.Index(dbURL, "://")
	if protocolIdx == -1 {
		return dbURL
	}

	protocol := dbURL[:protocolIdx+3]
	remaining := dbURL[protocolIdx+3:]

	// Find the LAST @ symbol that separates credentials from host
	// (to handle passwords that may contain @ characters)
	atIdx := strings.LastIndex(remaining, "@")
	if atIdx == -1 {
		// No credentials in the URL
		return dbURL
	}

	// Extract credentials part and check if there's a password
	credentials := remaining[:atIdx]
	hostPart := remaining[atIdx:]

	// Check if there's a colon (indicating a password)
	colonIdx := strings.Index(credentials, ":")
	if colonIdx == -1 {
		// No password, just username
		return protocol + credentials + hostPart
	}

	// Extract username and redact password
	username := credentials[:colonIdx]
	return protocol + username + ":***REDACTED***" + hostPart
}

// GetDefaultAccount returns the default account name for a notifier type, or the first account if no default is set
func (c *Config) GetDefaultAccount(notifierType domain.NotificationType) string {
	switch notifierType {
	case domain.TypeEmail:
		for name, cfg := range c.Notifiers.SMTP {
			if cfg.Default {
				return name
			}
		}
		// Return first account if no default is set
		for name := range c.Notifiers.SMTP {
			return name
		}
	case domain.TypeSlack:
		for name, cfg := range c.Notifiers.Slack {
			if cfg.Default {
				return name
			}
		}
		// Return first account if no default is set
		for name := range c.Notifiers.Slack {
			return name
		}
	case domain.TypeNtfy:
		for name, cfg := range c.Notifiers.Ntfy {
			if cfg.Default {
				return name
			}
		}
		// Return first account if no default is set
		for name := range c.Notifiers.Ntfy {
			return name
		}
	}
	return ""
}