package storage

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/atlasos/calypso/internal/common/database"
	"github.com/atlasos/calypso/internal/common/logger"
	"github.com/google/uuid"
)

// SnapshotScheduleService handles snapshot schedule management
type SnapshotScheduleService struct {
	db              *database.DB
	logger          *logger.Logger
	snapshotService *SnapshotService
}

// NewSnapshotScheduleService creates a new snapshot schedule service
func NewSnapshotScheduleService(db *database.DB, log *logger.Logger, snapshotService *SnapshotService) *SnapshotScheduleService {
	return &SnapshotScheduleService{
		db:              db,
		logger:          log,
		snapshotService: snapshotService,
	}
}

// SnapshotSchedule represents a scheduled snapshot task
type SnapshotSchedule struct {
	ID                   string                 `json:"id"`
	Name                 string                 `json:"name"`
	Dataset              string                 `json:"dataset"`
	SnapshotNameTemplate string                 `json:"snapshot_name_template"`
	ScheduleType         string                 `json:"schedule_type"` // hourly, daily, weekly, monthly, cron
	ScheduleConfig       map[string]interface{} `json:"schedule_config"`
	Recursive            bool                   `json:"recursive"`
	Enabled              bool                   `json:"enabled"`
	RetentionCount       *int                   `json:"retention_count,omitempty"`
	RetentionDays        *int                   `json:"retention_days,omitempty"`
	LastRunAt            *time.Time             `json:"last_run_at,omitempty"`
	NextRunAt            *time.Time             `json:"next_run_at,omitempty"`
	CreatedBy            string                 `json:"created_by,omitempty"`
	CreatedAt            time.Time              `json:"created_at"`
	UpdatedAt            time.Time              `json:"updated_at"`
}

// CreateScheduleRequest represents a request to create a snapshot schedule
type CreateScheduleRequest struct {
	Name                 string                 `json:"name" binding:"required"`
	Dataset              string                 `json:"dataset" binding:"required"`
	SnapshotNameTemplate string                 `json:"snapshot_name_template" binding:"required"`
	ScheduleType         string                 `json:"schedule_type" binding:"required"`
	ScheduleConfig       map[string]interface{} `json:"schedule_config" binding:"required"`
	Recursive            bool                   `json:"recursive"`
	RetentionCount       *int                   `json:"retention_count"`
	RetentionDays        *int                   `json:"retention_days"`
}

// ListSchedules lists all snapshot schedules
func (s *SnapshotScheduleService) ListSchedules(ctx context.Context) ([]*SnapshotSchedule, error) {
	query := `
		SELECT id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
		       recursive, enabled, retention_count, retention_days,
		       last_run_at, next_run_at, created_by, created_at, updated_at
		FROM snapshot_schedules
		ORDER BY created_at DESC
	`

	rows, err := s.db.QueryContext(ctx, query)
	if err != nil {
		return nil, fmt.Errorf("failed to query schedules: %w", err)
	}
	defer rows.Close()

	var schedules []*SnapshotSchedule
	for rows.Next() {
		schedule, err := s.scanSchedule(rows)
		if err != nil {
			s.logger.Error("Failed to scan schedule", "error", err)
			continue
		}
		schedules = append(schedules, schedule)
	}

	return schedules, rows.Err()
}

// GetSchedule retrieves a schedule by ID
func (s *SnapshotScheduleService) GetSchedule(ctx context.Context, id string) (*SnapshotSchedule, error) {
	query := `
		SELECT id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
		       recursive, enabled, retention_count, retention_days,
		       last_run_at, next_run_at, created_by, created_at, updated_at
		FROM snapshot_schedules
		WHERE id = $1
	`

	row := s.db.QueryRowContext(ctx, query, id)
	schedule, err := s.scanScheduleRow(row)
	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("schedule not found")
		}
		return nil, fmt.Errorf("failed to get schedule: %w", err)
	}

	return schedule, nil
}

// CreateSchedule creates a new snapshot schedule
func (s *SnapshotScheduleService) CreateSchedule(ctx context.Context, req *CreateScheduleRequest, createdBy string) (*SnapshotSchedule, error) {
	id := uuid.New().String()

	// Calculate next run time
	nextRunAt, err := s.calculateNextRun(req.ScheduleType, req.ScheduleConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to calculate next run time: %w", err)
	}

	// Marshal schedule config to JSON
	configJSON, err := json.Marshal(req.ScheduleConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal schedule config: %w", err)
	}

	query := `
		INSERT INTO snapshot_schedules (
			id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
			recursive, enabled, retention_count, retention_days,
			next_run_at, created_by, created_at, updated_at
		) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, NOW(), NOW())
		RETURNING id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
		          recursive, enabled, retention_count, retention_days,
		          last_run_at, next_run_at, created_by, created_at, updated_at
	`

	row := s.db.QueryRowContext(ctx, query,
		id, req.Name, req.Dataset, req.SnapshotNameTemplate, req.ScheduleType,
		string(configJSON), req.Recursive, true, req.RetentionCount, req.RetentionDays,
		nextRunAt, createdBy,
	)

	schedule, err := s.scanScheduleRow(row)
	if err != nil {
		return nil, fmt.Errorf("failed to create schedule: %w", err)
	}

	s.logger.Info("Snapshot schedule created", "id", id, "name", req.Name, "dataset", req.Dataset)
	return schedule, nil
}

// UpdateSchedule updates an existing schedule
func (s *SnapshotScheduleService) UpdateSchedule(ctx context.Context, id string, req *CreateScheduleRequest) (*SnapshotSchedule, error) {
	// Calculate next run time
	nextRunAt, err := s.calculateNextRun(req.ScheduleType, req.ScheduleConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to calculate next run time: %w", err)
	}

	// Marshal schedule config to JSON
	configJSON, err := json.Marshal(req.ScheduleConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal schedule config: %w", err)
	}

	query := `
		UPDATE snapshot_schedules
		SET name = $1, dataset = $2, snapshot_name_template = $3, schedule_type = $4,
		    schedule_config = $5, recursive = $6, retention_count = $7, retention_days = $8,
		    next_run_at = $9, updated_at = NOW()
		WHERE id = $10
		RETURNING id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
		          recursive, enabled, retention_count, retention_days,
		          last_run_at, next_run_at, created_by, created_at, updated_at
	`

	row := s.db.QueryRowContext(ctx, query,
		req.Name, req.Dataset, req.SnapshotNameTemplate, req.ScheduleType,
		string(configJSON), req.Recursive, req.RetentionCount, req.RetentionDays,
		nextRunAt, id,
	)

	schedule, err := s.scanScheduleRow(row)
	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("schedule not found")
		}
		return nil, fmt.Errorf("failed to update schedule: %w", err)
	}

	s.logger.Info("Snapshot schedule updated", "id", id)
	return schedule, nil
}

// DeleteSchedule deletes a schedule
func (s *SnapshotScheduleService) DeleteSchedule(ctx context.Context, id string) error {
	query := `DELETE FROM snapshot_schedules WHERE id = $1`
	result, err := s.db.ExecContext(ctx, query, id)
	if err != nil {
		return fmt.Errorf("failed to delete schedule: %w", err)
	}

	rowsAffected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rowsAffected == 0 {
		return fmt.Errorf("schedule not found")
	}

	s.logger.Info("Snapshot schedule deleted", "id", id)
	return nil
}

// ToggleSchedule enables or disables a schedule
func (s *SnapshotScheduleService) ToggleSchedule(ctx context.Context, id string, enabled bool) error {
	query := `UPDATE snapshot_schedules SET enabled = $1, updated_at = NOW() WHERE id = $2`
	result, err := s.db.ExecContext(ctx, query, enabled, id)
	if err != nil {
		return fmt.Errorf("failed to toggle schedule: %w", err)
	}

	rowsAffected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rowsAffected == 0 {
		return fmt.Errorf("schedule not found")
	}

	s.logger.Info("Snapshot schedule toggled", "id", id, "enabled", enabled)
	return nil
}

// scanScheduleRow scans a single schedule row
func (s *SnapshotScheduleService) scanScheduleRow(row *sql.Row) (*SnapshotSchedule, error) {
	var schedule SnapshotSchedule
	var configJSON string
	var lastRunAt, nextRunAt sql.NullTime
	var retentionCount, retentionDays sql.NullInt64
	var createdBy sql.NullString

	err := row.Scan(
		&schedule.ID, &schedule.Name, &schedule.Dataset, &schedule.SnapshotNameTemplate,
		&schedule.ScheduleType, &configJSON, &schedule.Recursive, &schedule.Enabled,
		&retentionCount, &retentionDays, &lastRunAt, &nextRunAt,
		&createdBy, &schedule.CreatedAt, &schedule.UpdatedAt,
	)
	if err != nil {
		return nil, err
	}

	// Parse schedule config JSON
	if err := json.Unmarshal([]byte(configJSON), &schedule.ScheduleConfig); err != nil {
		return nil, fmt.Errorf("failed to unmarshal schedule config: %w", err)
	}

	// Handle nullable fields
	if lastRunAt.Valid {
		schedule.LastRunAt = &lastRunAt.Time
	}
	if nextRunAt.Valid {
		schedule.NextRunAt = &nextRunAt.Time
	}
	if retentionCount.Valid {
		count := int(retentionCount.Int64)
		schedule.RetentionCount = &count
	}
	if retentionDays.Valid {
		days := int(retentionDays.Int64)
		schedule.RetentionDays = &days
	}
	if createdBy.Valid {
		schedule.CreatedBy = createdBy.String
	}

	return &schedule, nil
}

// scanSchedule scans a schedule from rows
func (s *SnapshotScheduleService) scanSchedule(rows *sql.Rows) (*SnapshotSchedule, error) {
	var schedule SnapshotSchedule
	var configJSON string
	var lastRunAt, nextRunAt sql.NullTime
	var retentionCount, retentionDays sql.NullInt64
	var createdBy sql.NullString

	err := rows.Scan(
		&schedule.ID, &schedule.Name, &schedule.Dataset, &schedule.SnapshotNameTemplate,
		&schedule.ScheduleType, &configJSON, &schedule.Recursive, &schedule.Enabled,
		&retentionCount, &retentionDays, &lastRunAt, &nextRunAt,
		&createdBy, &schedule.CreatedAt, &schedule.UpdatedAt,
	)
	if err != nil {
		return nil, err
	}

	// Parse schedule config JSON
	if err := json.Unmarshal([]byte(configJSON), &schedule.ScheduleConfig); err != nil {
		return nil, fmt.Errorf("failed to unmarshal schedule config: %w", err)
	}

	// Handle nullable fields
	if lastRunAt.Valid {
		schedule.LastRunAt = &lastRunAt.Time
	}
	if nextRunAt.Valid {
		schedule.NextRunAt = &nextRunAt.Time
	}
	if retentionCount.Valid {
		count := int(retentionCount.Int64)
		schedule.RetentionCount = &count
	}
	if retentionDays.Valid {
		days := int(retentionDays.Int64)
		schedule.RetentionDays = &days
	}
	if createdBy.Valid {
		schedule.CreatedBy = createdBy.String
	}

	return &schedule, nil
}

// calculateNextRun calculates the next run time based on schedule type and config
func (s *SnapshotScheduleService) calculateNextRun(scheduleType string, config map[string]interface{}) (*time.Time, error) {
	now := time.Now()

	switch scheduleType {
	case "hourly":
		nextRun := now.Add(1 * time.Hour)
		// Round to next hour
		nextRun = nextRun.Truncate(time.Hour).Add(1 * time.Hour)
		return &nextRun, nil

	case "daily":
		timeStr, ok := config["time"].(string)
		if !ok {
			timeStr = "00:00"
		}
		// Parse time (HH:MM format)
		hour, min := 0, 0
		fmt.Sscanf(timeStr, "%d:%d", &hour, &min)
		nextRun := time.Date(now.Year(), now.Month(), now.Day(), hour, min, 0, 0, now.Location())
		if nextRun.Before(now) {
			nextRun = nextRun.Add(24 * time.Hour)
		}
		return &nextRun, nil

	case "weekly":
		dayOfWeek, ok := config["day"].(float64) // JSON numbers are float64
		if !ok {
			dayOfWeek = 0 // Sunday
		}
		timeStr, ok := config["time"].(string)
		if !ok {
			timeStr = "00:00"
		}
		hour, min := 0, 0
		fmt.Sscanf(timeStr, "%d:%d", &hour, &min)

		// Calculate next occurrence
		currentDay := int(now.Weekday())
		targetDay := int(dayOfWeek)
		daysUntil := (targetDay - currentDay + 7) % 7
		if daysUntil == 0 {
			// If same day, check if time has passed
			today := time.Date(now.Year(), now.Month(), now.Day(), hour, min, 0, 0, now.Location())
			if today.Before(now) {
				daysUntil = 7
			}
		}
		nextRun := time.Date(now.Year(), now.Month(), now.Day(), hour, min, 0, 0, now.Location()).AddDate(0, 0, daysUntil)
		return &nextRun, nil

	case "monthly":
		day, ok := config["day"].(float64)
		if !ok {
			day = 1
		}
		timeStr, ok := config["time"].(string)
		if !ok {
			timeStr = "00:00"
		}
		hour, min := 0, 0
		fmt.Sscanf(timeStr, "%d:%d", &hour, &min)

		// Calculate next occurrence
		nextRun := time.Date(now.Year(), now.Month(), int(day), hour, min, 0, 0, now.Location())
		if nextRun.Before(now) {
			nextRun = nextRun.AddDate(0, 1, 0)
		}
		return &nextRun, nil

	case "cron":
		// For cron, we'll use a simple implementation
		// In production, you'd want to use a proper cron parser library
		_, ok := config["cron"].(string)
		if !ok {
			return nil, fmt.Errorf("cron expression not found in config")
		}
		// Simple implementation: assume next run is in 1 hour
		// TODO: Implement proper cron parsing
		nextRun := now.Add(1 * time.Hour)
		return &nextRun, nil

	default:
		return nil, fmt.Errorf("unknown schedule type: %s", scheduleType)
	}
}

// GetDueSchedules retrieves all enabled schedules that are due to run
func (s *SnapshotScheduleService) GetDueSchedules(ctx context.Context) ([]*SnapshotSchedule, error) {
	now := time.Now()
	query := `
		SELECT id, name, dataset, snapshot_name_template, schedule_type, schedule_config,
		       recursive, enabled, retention_count, retention_days,
		       last_run_at, next_run_at, created_by, created_at, updated_at
		FROM snapshot_schedules
		WHERE enabled = true AND next_run_at <= $1
		ORDER BY next_run_at ASC
	`

	rows, err := s.db.QueryContext(ctx, query, now)
	if err != nil {
		return nil, fmt.Errorf("failed to query due schedules: %w", err)
	}
	defer rows.Close()

	var schedules []*SnapshotSchedule
	for rows.Next() {
		schedule, err := s.scanSchedule(rows)
		if err != nil {
			s.logger.Error("Failed to scan schedule", "error", err)
			continue
		}
		schedules = append(schedules, schedule)
	}

	return schedules, rows.Err()
}

// ExecuteSchedule executes a snapshot schedule
func (s *SnapshotScheduleService) ExecuteSchedule(ctx context.Context, schedule *SnapshotSchedule) error {
	now := time.Now()

	// Generate snapshot name from template
	snapshotName := s.generateSnapshotName(schedule.SnapshotNameTemplate, now)

	// Create snapshot
	if err := s.snapshotService.CreateSnapshot(ctx, schedule.Dataset, snapshotName, schedule.Recursive); err != nil {
		return fmt.Errorf("failed to create snapshot: %w", err)
	}

	s.logger.Info("Snapshot created from schedule", "schedule", schedule.Name, "snapshot", snapshotName, "dataset", schedule.Dataset)

	// Calculate next run time
	nextRunAt, err := s.calculateNextRun(schedule.ScheduleType, schedule.ScheduleConfig)
	if err != nil {
		s.logger.Error("Failed to calculate next run time", "error", err, "schedule", schedule.Name)
		// Set a default next run time (1 hour from now) if calculation fails
		defaultNextRun := now.Add(1 * time.Hour)
		nextRunAt = &defaultNextRun
	}

	// Update schedule with last run time and next run time
	query := `
		UPDATE snapshot_schedules
		SET last_run_at = $1, next_run_at = $2, updated_at = NOW()
		WHERE id = $3
	`
	if _, err := s.db.ExecContext(ctx, query, now, nextRunAt, schedule.ID); err != nil {
		s.logger.Error("Failed to update schedule after execution", "error", err, "schedule", schedule.Name)
		// Don't return error here - snapshot was created successfully
	}

	// Handle retention
	if err := s.handleRetention(ctx, schedule); err != nil {
		s.logger.Error("Failed to handle retention", "error", err, "schedule", schedule.Name)
		// Don't return error - retention is best effort
	}

	return nil
}

// generateSnapshotName generates a snapshot name from a template
func (s *SnapshotScheduleService) generateSnapshotName(template string, t time.Time) string {
	// Replace common time format placeholders
	name := template
	name = strings.ReplaceAll(name, "%Y", t.Format("2006"))
	name = strings.ReplaceAll(name, "%m", t.Format("01"))
	name = strings.ReplaceAll(name, "%d", t.Format("02"))
	name = strings.ReplaceAll(name, "%H", t.Format("15"))
	name = strings.ReplaceAll(name, "%M", t.Format("04"))
	name = strings.ReplaceAll(name, "%S", t.Format("05"))
	name = strings.ReplaceAll(name, "%Y-%m-%d", t.Format("2006-01-02"))
	name = strings.ReplaceAll(name, "%Y-%m-%d-%H%M", t.Format("2006-01-02-1504"))
	name = strings.ReplaceAll(name, "%Y-%m-%d-%H%M%S", t.Format("2006-01-02-150405"))

	// If no placeholders were replaced, append timestamp
	if name == template {
		name = fmt.Sprintf("%s-%d", template, t.Unix())
	}

	return name
}

// handleRetention handles snapshot retention based on schedule settings
func (s *SnapshotScheduleService) handleRetention(ctx context.Context, schedule *SnapshotSchedule) error {
	// Get all snapshots for this dataset
	snapshots, err := s.snapshotService.ListSnapshots(ctx, schedule.Dataset)
	if err != nil {
		return fmt.Errorf("failed to list snapshots: %w", err)
	}

	// Filter snapshots that match this schedule's naming pattern
	matchingSnapshots := make([]*Snapshot, 0)
	for _, snapshot := range snapshots {
		// Check if snapshot name matches the template pattern
		if s.snapshotMatchesTemplate(snapshot.SnapshotName, schedule.SnapshotNameTemplate) {
			matchingSnapshots = append(matchingSnapshots, snapshot)
		}
	}

	now := time.Now()
	snapshotsToDelete := make([]*Snapshot, 0)

	// Apply retention_count if set
	if schedule.RetentionCount != nil && *schedule.RetentionCount > 0 {
		if len(matchingSnapshots) > *schedule.RetentionCount {
			// Sort by creation time (oldest first)
			sort.Slice(matchingSnapshots, func(i, j int) bool {
				return matchingSnapshots[i].Created.Before(matchingSnapshots[j].Created)
			})
			// Mark excess snapshots for deletion
			excessCount := len(matchingSnapshots) - *schedule.RetentionCount
			for i := 0; i < excessCount; i++ {
				snapshotsToDelete = append(snapshotsToDelete, matchingSnapshots[i])
			}
		}
	}

	// Apply retention_days if set
	if schedule.RetentionDays != nil && *schedule.RetentionDays > 0 {
		cutoffTime := now.AddDate(0, 0, -*schedule.RetentionDays)
		for _, snapshot := range matchingSnapshots {
			if snapshot.Created.Before(cutoffTime) {
				// Check if not already marked for deletion
				alreadyMarked := false
				for _, marked := range snapshotsToDelete {
					if marked.ID == snapshot.ID {
						alreadyMarked = true
						break
					}
				}
				if !alreadyMarked {
					snapshotsToDelete = append(snapshotsToDelete, snapshot)
				}
			}
		}
	}

	// Delete snapshots
	for _, snapshot := range snapshotsToDelete {
		if err := s.snapshotService.DeleteSnapshot(ctx, snapshot.Name, schedule.Recursive); err != nil {
			s.logger.Error("Failed to delete snapshot for retention", "error", err, "snapshot", snapshot.Name)
			continue
		}
		s.logger.Info("Deleted snapshot for retention", "snapshot", snapshot.Name, "schedule", schedule.Name)
	}

	return nil
}

// snapshotMatchesTemplate checks if a snapshot name matches a template pattern
func (s *SnapshotScheduleService) snapshotMatchesTemplate(snapshotName, template string) bool {
	if template == "" {
		return false
	}

	// Extract the base name from template (everything before the first %)
	// This handles templates like "auto-%Y-%m-%d" or "daily-backup-%Y%m%d"
	baseName := template
	if idx := strings.Index(template, "%"); idx != -1 {
		baseName = template[:idx]
	}

	// If template starts with a placeholder, check if snapshot name matches the pattern
	// by checking if it starts with any reasonable prefix
	if baseName == "" {
		// Template starts with placeholder - use a more lenient check
		// Check if snapshot name matches common patterns
		return true // Match all if template is just placeholders
	}

	// Check if snapshot name starts with the base name
	// This handles cases like template "auto-%Y-%m-%d" matching snapshot "auto-2024-01-15"
	return strings.HasPrefix(snapshotName, baseName)
}