// Package database provides database abstraction for Tyto.
// Supports both SQLite (default) and PostgreSQL backends.
package database

import (
	"context"
	"time"

	"tyto/internal/models"
)

// Database defines the interface for all database operations.
type Database interface {
	// Lifecycle
	Close() error
	Migrate() error

	// Metrics storage
	StoreMetrics(ctx context.Context, agentID string, metrics *models.AllMetrics) error
	QueryMetrics(ctx context.Context, agentID string, from, to time.Time, resolution string) ([]MetricPoint, error)
	GetLatestMetrics(ctx context.Context, agentID string) (*models.AllMetrics, error)

	// Agents (extends registry with persistence)
	StoreAgent(ctx context.Context, agent *Agent) error
	GetAgent(ctx context.Context, id string) (*Agent, error)
	ListAgents(ctx context.Context) ([]*Agent, error)
	UpdateAgentStatus(ctx context.Context, id string, status AgentStatus, lastSeen time.Time) error
	DeleteAgent(ctx context.Context, id string) error

	// Users
	CreateUser(ctx context.Context, user *User) error
	GetUser(ctx context.Context, id string) (*User, error)
	GetUserByUsername(ctx context.Context, username string) (*User, error)
	UpdateUser(ctx context.Context, user *User) error
	DeleteUser(ctx context.Context, id string) error
	ListUsers(ctx context.Context) ([]*User, error)

	// Roles
	CreateRole(ctx context.Context, role *Role) error
	GetRole(ctx context.Context, id string) (*Role, error)
	ListRoles(ctx context.Context) ([]*Role, error)
	UpdateRole(ctx context.Context, role *Role) error
	DeleteRole(ctx context.Context, id string) error
	GetUserRoles(ctx context.Context, userID string) ([]*Role, error)
	AssignRole(ctx context.Context, userID, roleID string) error
	RemoveRole(ctx context.Context, userID, roleID string) error

	// Sessions
	CreateSession(ctx context.Context, session *Session) error
	GetSession(ctx context.Context, token string) (*Session, error)
	DeleteSession(ctx context.Context, token string) error
	DeleteUserSessions(ctx context.Context, userID string) error
	CleanupExpiredSessions(ctx context.Context) error

	// Alerts
	StoreAlert(ctx context.Context, alert *Alert) error
	GetAlert(ctx context.Context, id string) (*Alert, error)
	QueryAlerts(ctx context.Context, filter AlertFilter) ([]*Alert, error)
	AcknowledgeAlert(ctx context.Context, id string) error

	// Retention
	RunRetention(ctx context.Context) error

	// Logs
	StoreLogs(ctx context.Context, entries []LogEntry) error
	QueryLogs(ctx context.Context, filter LogFilter) ([]LogEntry, int, error)
	DeleteOldLogs(ctx context.Context, before time.Time) (int, error)
}

// MetricPoint represents a single metric data point.
type MetricPoint struct {
	Timestamp time.Time `json:"timestamp"`
	AgentID   string    `json:"agentId"`

	// Aggregated values
	CPUAvg    float64 `json:"cpuAvg"`
	CPUMin    float64 `json:"cpuMin"`
	CPUMax    float64 `json:"cpuMax"`
	MemoryAvg float64 `json:"memoryAvg"`
	MemoryMin float64 `json:"memoryMin"`
	MemoryMax float64 `json:"memoryMax"`
	DiskAvg   float64 `json:"diskAvg,omitempty"`
	GPUAvg    float64 `json:"gpuAvg,omitempty"`
}

// AgentStatus represents agent connection state.
type AgentStatus string

const (
	AgentStatusPending   AgentStatus = "pending"
	AgentStatusApproved  AgentStatus = "approved"
	AgentStatusConnected AgentStatus = "connected"
	AgentStatusOffline   AgentStatus = "offline"
	AgentStatusRevoked   AgentStatus = "revoked"
)

// Agent represents a registered monitoring agent.
type Agent struct {
	ID           string      `json:"id"`
	Name         string      `json:"name,omitempty"`
	Hostname     string      `json:"hostname"`
	OS           string      `json:"os"`
	Architecture string      `json:"architecture"`
	Version      string      `json:"version"`
	Capabilities []string    `json:"capabilities,omitempty"`
	Status       AgentStatus `json:"status"`
	CertSerial   string      `json:"certSerial,omitempty"`
	CertExpiry   time.Time   `json:"certExpiry,omitempty"`
	LastSeen     time.Time   `json:"lastSeen,omitempty"`
	RegisteredAt time.Time   `json:"registeredAt"`
	Tags         []string    `json:"tags,omitempty"`
}

// AuthProvider indicates how a user authenticates.
type AuthProvider string

const (
	AuthProviderLocal AuthProvider = "local"
	AuthProviderLDAP  AuthProvider = "ldap"
)

// User represents a system user.
type User struct {
	ID           string       `json:"id"`
	Username     string       `json:"username"`
	Email        string       `json:"email,omitempty"`
	PasswordHash []byte       `json:"-"`
	AuthProvider AuthProvider `json:"authProvider"`
	LDAPDN       string       `json:"ldapDn,omitempty"`
	CreatedAt    time.Time    `json:"createdAt"`
	UpdatedAt    time.Time    `json:"updatedAt"`
	LastLogin    time.Time    `json:"lastLogin,omitempty"`
	Disabled     bool         `json:"disabled"`
}

// Role represents a set of permissions.
type Role struct {
	ID          string   `json:"id"`
	Name        string   `json:"name"`
	Description string   `json:"description,omitempty"`
	Permissions []string `json:"permissions"`
	IsSystem    bool     `json:"isSystem"`
	CreatedAt   time.Time `json:"createdAt"`
}

// Session represents an authenticated user session.
type Session struct {
	Token     string    `json:"token"`
	UserID    string    `json:"userId"`
	CreatedAt time.Time `json:"createdAt"`
	ExpiresAt time.Time `json:"expiresAt"`
	IPAddress string    `json:"ipAddress,omitempty"`
	UserAgent string    `json:"userAgent,omitempty"`
}

// AlertSeverity indicates alert severity level.
type AlertSeverity string

const (
	AlertSeverityWarning  AlertSeverity = "warning"
	AlertSeverityCritical AlertSeverity = "critical"
)

// Alert represents a triggered alert.
type Alert struct {
	ID           string        `json:"id"`
	AgentID      string        `json:"agentId"`
	Type         string        `json:"type"`
	Severity     AlertSeverity `json:"severity"`
	Message      string        `json:"message"`
	Value        float64       `json:"value"`
	Threshold    float64       `json:"threshold"`
	TriggeredAt  time.Time     `json:"triggeredAt"`
	ResolvedAt   *time.Time    `json:"resolvedAt,omitempty"`
	Acknowledged bool          `json:"acknowledged"`
}

// AlertFilter specifies criteria for querying alerts.
type AlertFilter struct {
	AgentID      string
	Type         string
	Severity     AlertSeverity
	Acknowledged *bool
	From         time.Time
	To           time.Time
	Limit        int
	Offset       int
}

// LogLevel represents log severity.
type LogLevel string

const (
	LogLevelDebug   LogLevel = "debug"
	LogLevelInfo    LogLevel = "info"
	LogLevelWarning LogLevel = "warning"
	LogLevelError   LogLevel = "error"
	LogLevelFatal   LogLevel = "fatal"
)

// LogEntry represents a stored log entry.
type LogEntry struct {
	ID         int64             `json:"id"`
	AgentID    string            `json:"agentId"`
	Timestamp  time.Time         `json:"timestamp"`
	Source     string            `json:"source"`     // "journal", "file", "docker"
	SourceName string            `json:"sourceName"` // Unit name, filename, container
	Level      LogLevel          `json:"level"`
	Message    string            `json:"message"`
	Fields     map[string]string `json:"fields,omitempty"`
}

// LogFilter specifies criteria for querying logs.
type LogFilter struct {
	AgentID    string     // Filter by agent
	Source     string     // Filter by source type (journal, file, docker)
	SourceName string     // Filter by source name
	Level      []LogLevel // Filter by levels
	Query      string     // Full-text search query
	From       time.Time
	To         time.Time
	Limit      int
	Offset     int
}

// RetentionConfig defines data retention policies.
type RetentionConfig struct {
	// Raw metrics retention (default: 24 hours)
	RawRetention time.Duration

	// 1-minute aggregation retention (default: 7 days)
	OneMinuteRetention time.Duration

	// 5-minute aggregation retention (default: 30 days)
	FiveMinuteRetention time.Duration

	// Hourly aggregation retention (default: 1 year)
	HourlyRetention time.Duration

	// Log retention (default: 7 days)
	LogRetention time.Duration
}

// DefaultRetentionConfig returns default retention settings.
func DefaultRetentionConfig() RetentionConfig {
	return RetentionConfig{
		RawRetention:        24 * time.Hour,
		OneMinuteRetention:  7 * 24 * time.Hour,
		FiveMinuteRetention: 30 * 24 * time.Hour,
		HourlyRetention:     365 * 24 * time.Hour,
		LogRetention:        7 * 24 * time.Hour,
	}
}