package docker

import (
	"context"
	"fmt"
	"time"

	"github.com/moby/moby/client"
)

// SystemStats is a host-level snapshot combining daemon capacity
// (NCPU, memory total) with container counts and disk usage broken down
// by category. Workload CPU/memory utilization is aggregated from
// per-container samples by the stats collector, not here.
type SystemStats struct {
	Timestamp time.Time `json:"timestamp"`

	// Capacity from Docker daemon.
	NCPU        int   `json:"ncpu"`
	MemoryTotal int64 `json:"memory_total"`

	// Container/image counts.
	Containers int `json:"containers"`
	Running    int `json:"running"`
	Paused     int `json:"paused"`
	Stopped    int `json:"stopped"`
	Images     int `json:"images"`

	// Disk usage by category (bytes).
	DiskImagesBytes     int64 `json:"disk_images_bytes"`
	DiskContainersBytes int64 `json:"disk_containers_bytes"`
	DiskVolumesBytes    int64 `json:"disk_volumes_bytes"`
	DiskBuildCacheBytes int64 `json:"disk_build_cache_bytes"`

	// Reclaimable disk space by category (bytes).
	DiskImagesReclaimable     int64 `json:"disk_images_reclaimable"`
	DiskContainersReclaimable int64 `json:"disk_containers_reclaimable"`
	DiskVolumesReclaimable    int64 `json:"disk_volumes_reclaimable"`
	DiskBuildCacheReclaimable int64 `json:"disk_build_cache_reclaimable"`

	// DiskTotalBytes is the sum of the category totals.
	DiskTotalBytes int64 `json:"disk_total_bytes"`
}

// GetSystemStats returns a one-shot host-level snapshot. The Info() call
// and disk usage call are made in sequence. Disk usage failures do not
// fail the whole call — the result degrades gracefully with zero disk fields.
func (c *Client) GetSystemStats(ctx context.Context) (SystemStats, error) {
	info, err := c.Info(ctx)
	if err != nil {
		return SystemStats{}, fmt.Errorf("system stats: %w", err)
	}

	stats := SystemStats{
		Timestamp:   time.Now().UTC(),
		NCPU:        info.NCPU,
		MemoryTotal: info.MemoryTotal,
		Containers:  info.Containers,
		Running:     info.Running,
		Paused:      info.Paused,
		Stopped:     info.Stopped,
		Images:      info.Images,
	}

	du, derr := c.api.DiskUsage(ctx, client.DiskUsageOptions{
		Containers: true,
		Images:     true,
		Volumes:    true,
		BuildCache: true,
	})
	if derr == nil {
		stats.DiskImagesBytes = du.Images.TotalSize
		stats.DiskContainersBytes = du.Containers.TotalSize
		stats.DiskVolumesBytes = du.Volumes.TotalSize
		stats.DiskBuildCacheBytes = du.BuildCache.TotalSize
		stats.DiskImagesReclaimable = du.Images.Reclaimable
		stats.DiskContainersReclaimable = du.Containers.Reclaimable
		stats.DiskVolumesReclaimable = du.Volumes.Reclaimable
		stats.DiskBuildCacheReclaimable = du.BuildCache.Reclaimable
		stats.DiskTotalBytes = stats.DiskImagesBytes +
			stats.DiskContainersBytes +
			stats.DiskVolumesBytes +
			stats.DiskBuildCacheBytes
	}

	return stats, nil
}