package storage

import (
	"context"
	"os/exec"
	"regexp"
	"strconv"
	"strings"
	"time"

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

// ZFSPoolMonitor handles periodic ZFS pool status monitoring and sync to database
type ZFSPoolMonitor struct {
	zfsService *ZFSService
	logger     *logger.Logger
	interval   time.Duration
	stopCh     chan struct{}
}

// NewZFSPoolMonitor creates a new ZFS pool monitor service
func NewZFSPoolMonitor(db *database.DB, log *logger.Logger, interval time.Duration) *ZFSPoolMonitor {
	return &ZFSPoolMonitor{
		zfsService: NewZFSService(db, log),
		logger:     log,
		interval:   interval,
		stopCh:     make(chan struct{}),
	}
}

// Start starts the ZFS pool monitor background service
func (m *ZFSPoolMonitor) Start(ctx context.Context) {
	m.logger.Info("Starting ZFS pool monitor service", "interval", m.interval)
	ticker := time.NewTicker(m.interval)
	defer ticker.Stop()

	// Run initial sync immediately
	m.syncPools(ctx)

	for {
		select {
		case <-ctx.Done():
			m.logger.Info("ZFS pool monitor service stopped")
			return
		case <-m.stopCh:
			m.logger.Info("ZFS pool monitor service stopped")
			return
		case <-ticker.C:
			m.syncPools(ctx)
		}
	}
}

// Stop stops the ZFS pool monitor service
func (m *ZFSPoolMonitor) Stop() {
	close(m.stopCh)
}

// syncPools syncs ZFS pool status from system to database
func (m *ZFSPoolMonitor) syncPools(ctx context.Context) {
	m.logger.Debug("Running periodic ZFS pool sync")

	// Get all pools from system
	systemPools, err := m.getSystemPools(ctx)
	if err != nil {
		m.logger.Error("Failed to get system pools", "error", err)
		return
	}

	m.logger.Debug("Found pools in system", "count", len(systemPools))

	// Update each pool in database
	for poolName, poolInfo := range systemPools {
		if err := m.updatePoolStatus(ctx, poolName, poolInfo); err != nil {
			m.logger.Error("Failed to update pool status", "pool", poolName, "error", err)
		}
	}

	// Mark pools that don't exist in system as offline
	if err := m.markMissingPoolsOffline(ctx, systemPools); err != nil {
		m.logger.Error("Failed to mark missing pools offline", "error", err)
	}

	m.logger.Debug("ZFS pool sync completed")
}

// PoolInfo represents pool information from system
type PoolInfo struct {
	Name      string
	SizeBytes int64
	UsedBytes int64
	Health    string // online, degraded, faulted, offline, unavailable, removed
}

// getSystemPools gets all pools from ZFS system
func (m *ZFSPoolMonitor) getSystemPools(ctx context.Context) (map[string]PoolInfo, error) {
	pools := make(map[string]PoolInfo)

	// Get pool list
	cmd := exec.CommandContext(ctx, "zpool", "list", "-H", "-o", "name,size,alloc,free,health")
	output, err := cmd.Output()
	if err != nil {
		return nil, err
	}

	lines := strings.Split(strings.TrimSpace(string(output)), "\n")
	for _, line := range lines {
		if line == "" {
			continue
		}

		fields := strings.Fields(line)
		if len(fields) < 5 {
			continue
		}

		poolName := fields[0]
		sizeStr := fields[1]
		allocStr := fields[2]
		health := fields[4]

		// Parse size (e.g., "95.5G" -> bytes)
		sizeBytes, err := parseSize(sizeStr)
		if err != nil {
			m.logger.Warn("Failed to parse pool size", "pool", poolName, "size", sizeStr, "error", err)
			continue
		}

		// Parse allocated (used) size
		usedBytes, err := parseSize(allocStr)
		if err != nil {
			m.logger.Warn("Failed to parse pool used size", "pool", poolName, "alloc", allocStr, "error", err)
			continue
		}

		// Normalize health status to lowercase
		healthNormalized := strings.ToLower(health)

		pools[poolName] = PoolInfo{
			Name:      poolName,
			SizeBytes: sizeBytes,
			UsedBytes: usedBytes,
			Health:    healthNormalized,
		}
	}

	return pools, nil
}

// parseSize parses size string (e.g., "95.5G", "1.2T") to bytes
func parseSize(sizeStr string) (int64, error) {
	// Remove any whitespace
	sizeStr = strings.TrimSpace(sizeStr)

	// Match pattern like "95.5G", "1.2T", "512M"
	re := regexp.MustCompile(`^([\d.]+)([KMGT]?)$`)
	matches := re.FindStringSubmatch(strings.ToUpper(sizeStr))
	if len(matches) != 3 {
		return 0, nil // Return 0 if can't parse
	}

	value, err := strconv.ParseFloat(matches[1], 64)
	if err != nil {
		return 0, err
	}

	unit := matches[2]
	var multiplier int64 = 1

	switch unit {
	case "K":
		multiplier = 1024
	case "M":
		multiplier = 1024 * 1024
	case "G":
		multiplier = 1024 * 1024 * 1024
	case "T":
		multiplier = 1024 * 1024 * 1024 * 1024
	case "P":
		multiplier = 1024 * 1024 * 1024 * 1024 * 1024
	}

	return int64(value * float64(multiplier)), nil
}

// updatePoolStatus updates pool status in database
func (m *ZFSPoolMonitor) updatePoolStatus(ctx context.Context, poolName string, poolInfo PoolInfo) error {
	// Get pool from database by name
	var poolID string
	err := m.zfsService.db.QueryRowContext(ctx,
		"SELECT id FROM zfs_pools WHERE name = $1",
		poolName,
	).Scan(&poolID)

	if err != nil {
		// Pool not in database, skip (might be created outside of Calypso)
		m.logger.Debug("Pool not found in database, skipping", "pool", poolName)
		return nil
	}

	// Update pool status, size, and used bytes
	_, err = m.zfsService.db.ExecContext(ctx, `
		UPDATE zfs_pools SET
			size_bytes = $1,
			used_bytes = $2,
			health_status = $3,
			updated_at = NOW()
		WHERE id = $4
	`, poolInfo.SizeBytes, poolInfo.UsedBytes, poolInfo.Health, poolID)

	if err != nil {
		return err
	}

	m.logger.Debug("Updated pool status", "pool", poolName, "health", poolInfo.Health, "size", poolInfo.SizeBytes, "used", poolInfo.UsedBytes)
	return nil
}

// markMissingPoolsOffline marks pools that exist in database but not in system as offline or deletes them
func (m *ZFSPoolMonitor) markMissingPoolsOffline(ctx context.Context, systemPools map[string]PoolInfo) error {
	// Get all pools from database
	rows, err := m.zfsService.db.QueryContext(ctx, "SELECT id, name FROM zfs_pools WHERE is_active = true")
	if err != nil {
		return err
	}
	defer rows.Close()

	for rows.Next() {
		var poolID, poolName string
		if err := rows.Scan(&poolID, &poolName); err != nil {
			continue
		}

		// Check if pool exists in system
		if _, exists := systemPools[poolName]; !exists {
			// Pool doesn't exist in system - delete from database (pool was destroyed)
			m.logger.Info("Pool not found in system, removing from database", "pool", poolName)
			_, err = m.zfsService.db.ExecContext(ctx, "DELETE FROM zfs_pools WHERE id = $1", poolID)
			if err != nil {
				m.logger.Warn("Failed to delete missing pool from database", "pool", poolName, "error", err)
			} else {
				m.logger.Info("Removed missing pool from database", "pool", poolName)
			}
		}
	}

	return rows.Err()
}