package providers

import (
	"context"
	"database/sql"
	"errors"
	"time"

	"go.mongodb.org/mongo-driver/mongo"
)

// Common errors
var (
	// ErrNotSQLDatabase is returned when attempting SQL operations on a non-SQL database
	ErrNotSQLDatabase = errors.New("not a SQL database")

	// ErrNotMongoDB is returned when attempting MongoDB operations on a non-MongoDB connection
	ErrNotMongoDB = errors.New("not a MongoDB connection")
)

// ConnectionStats contains statistics about a database connection
type ConnectionStats struct {
	Name              string
	Type              string // Database type as string to avoid circular dependency
	Connected         bool
	LastHealthCheck   time.Time
	HealthCheckStatus string

	// SQL connection pool stats
	OpenConnections    int
	MaxOpenConnections int
	TotalOpened        int64 // physical connections ever dialled (0 when unknown)
	InUse              int
	Idle               int
	WaitCount          int64
	WaitDuration       time.Duration
	MaxIdleClosed      int64
	MaxLifetimeClosed  int64
}

// ConnectionConfig is a minimal interface for configuration
// The actual implementation is in dbmanager package
type ConnectionConfig interface {
	BuildDSN() (string, error)
	GetName() string
	GetType() string
	GetHost() string
	GetPort() int
	GetUser() string
	GetPassword() string
	GetDatabase() string
	GetFilePath() string
	GetConnectTimeout() time.Duration
	GetQueryTimeout() time.Duration
	GetEnableLogging() bool
	GetEnableMetrics() bool
	GetMaxOpenConns() *int
	GetMaxIdleConns() *int
	GetConnMaxLifetime() *time.Duration
	GetConnMaxIdleTime() *time.Duration
	GetReadPreference() string
	GetApplicationName() string
	GetRetryAttempts() int
	GetRetryDelay() time.Duration
	GetRetryMaxDelay() time.Duration
}

// retryPolicy returns the configured retry settings, falling back to defaults.
func retryPolicy(cfg ConnectionConfig) (attempts int, delay, maxDelay time.Duration) {
	attempts, delay, maxDelay = cfg.GetRetryAttempts(), cfg.GetRetryDelay(), cfg.GetRetryMaxDelay()
	if attempts <= 0 {
		attempts = 3
	}
	if delay <= 0 {
		delay = time.Second
	}
	if maxDelay <= 0 {
		maxDelay = 10 * time.Second
	}
	return
}

// Refresher is implemented by providers that can retire their pooled
// connections and dial fresh ones without closing the shared *sql.DB, so
// handles already handed out keep working.
type Refresher interface {
	Refresh(ctx context.Context) error
}

// Provider creates and manages the underlying database connection
type Provider interface {
	// Connect establishes the database connection
	Connect(ctx context.Context, cfg ConnectionConfig) error

	// Close closes the connection
	Close() error

	// HealthCheck verifies the connection is alive
	HealthCheck(ctx context.Context) error

	// GetNative returns the native *sql.DB (SQL databases only)
	// Returns an error for non-SQL databases
	GetNative() (*sql.DB, error)

	// GetMongo returns the MongoDB client (MongoDB only)
	// Returns an error for non-MongoDB databases
	GetMongo() (*mongo.Client, error)

	// Stats returns connection statistics
	Stats() *ConnectionStats
}