package services

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
	"time"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	"lokistack/models"
)

// ResourceUsage 是页面上「资源」弹框的数据。
//
// 三种部署模式都能采集：
//   - k8s-yaml     : StatefulSet resources + metrics-server（实时用量）
//   - host-docker  : docker stats / docker inspect（容器限额未设则按宿主机内存做参考）
//   - host-binary  : ps 采集进程 CPU%/RSS（无 cgroup 限额）
//
// 权限兼容：集群 token 常是最小权限，可能没有 metrics.k8s.io。
// 这时**不报错**，照样返回 limits/就绪/重启，并把原因写进 MetricsNote 让页面提示。
type ResourceUsage struct {
	Mode      string `json:"mode"`
	Source    string `json:"source"`
	Namespace string `json:"namespace,omitempty"`
	Pod       string `json:"pod,omitempty"`
	Node      string `json:"node,omitempty"`
	Ready     bool   `json:"ready"`
	Restarts  int32  `json:"restarts"`

	CPUCurrentMilli int64 `json:"cpuCurrentMilli"`
	CPURequestMilli int64 `json:"cpuRequestMilli"`
	CPULimitMilli   int64 `json:"cpuLimitMilli"`

	MemCurrentBytes int64 `json:"memCurrentBytes"`
	MemRequestBytes int64 `json:"memRequestBytes"`
	MemLimitBytes   int64 `json:"memLimitBytes"`

	// 限额是否真的配置了（docker 未加 --memory 时为 false，页面不画百分比）
	LimitsConfigured bool `json:"limitsConfigured"`

	// 采集受限说明（如缺 metrics.k8s.io 权限、未装 metrics-server、docker 无历史数据）
	MetricsNote string `json:"metricsNote,omitempty"`

	CPUSuggest string `json:"cpuSuggest,omitempty"`
	MemSuggest string `json:"memSuggest,omitempty"`
	Summary    string `json:"summary"`
}

type podMetricsResponse struct {
	Containers []struct {
		Name  string `json:"name"`
		Usage struct {
			CPU    string `json:"cpu"`
			Memory string `json:"memory"`
		} `json:"usage"`
	} `json:"containers"`
}

// GetUsage 采集某个 Loki 部署的资源用量（按部署模式分派）。
func (s *DeploymentService) GetUsage(ctx context.Context, id uint) (*ResourceUsage, error) {
	d, err := s.Get(id)
	if err != nil {
		return nil, err
	}
	switch d.Mode {
	case "k8s-yaml":
		return s.k8sUsage(ctx, d)
	case "host-docker":
		return s.dockerUsage(ctx, d)
	case "host-binary":
		return s.processUsage(ctx, d)
	default:
		return nil, fmt.Errorf("不支持的部署模式：%s", d.Mode)
	}
}

// ---------- Kubernetes ----------

func (s *DeploymentService) k8sUsage(ctx context.Context, d *models.LokiDeployment) (*ResourceUsage, error) {
	if d.Cluster == nil {
		return nil, fmt.Errorf("部署未关联 Kubernetes 集群")
	}
	client, err := clusterClient(d.Cluster, 20*time.Second)
	if err != nil {
		return nil, err
	}
	ctx, cancel := context.WithTimeout(ctx, 15*time.Second)
	defer cancel()

	ns := d.Namespace
	if ns == "" {
		ns = "log"
	}
	usage := &ResourceUsage{Mode: d.Mode, Source: "kubernetes", Namespace: ns, Pod: "loki-0"}

	// 1) limits/requests 取线上 StatefulSet（以运行态为准，不信部署记录）
	if sts, err := client.AppsV1().StatefulSets(ns).Get(ctx, "loki", metav1.GetOptions{}); err == nil &&
		len(sts.Spec.Template.Spec.Containers) > 0 {
		res := sts.Spec.Template.Spec.Containers[0].Resources
		usage.CPULimitMilli = parseQuantityMilli(res.Limits.Cpu().String())
		usage.CPURequestMilli = parseQuantityMilli(res.Requests.Cpu().String())
		usage.MemLimitBytes = parseQuantityBytes(res.Limits.Memory().String())
		usage.MemRequestBytes = parseQuantityBytes(res.Requests.Memory().String())
		usage.LimitsConfigured = usage.CPULimitMilli > 0 && usage.MemLimitBytes > 0
	}

	// 2) Pod 状态
	if pod, err := client.CoreV1().Pods(ns).Get(ctx, usage.Pod, metav1.GetOptions{}); err == nil {
		usage.Node = pod.Spec.NodeName
		for _, cs := range pod.Status.ContainerStatuses {
			if cs.Name == "loki" {
				usage.Ready = cs.Ready
				usage.Restarts = cs.RestartCount
			}
		}
	}

	// 3) 实时用量：metrics-server（最小权限 token 常常没有这个 API 组，要降级而不是报错）
	raw, err := client.Discovery().RESTClient().Get().
		AbsPath("/apis/metrics.k8s.io/v1beta1/namespaces/" + ns + "/pods/" + usage.Pod).
		DoRaw(ctx)
	switch {
	case err != nil:
		usage.MetricsNote = explainMetricsError(err)
	case json.Unmarshal(raw, &podMetricsResponse{}) == nil:
		var pm podMetricsResponse
		if json.Unmarshal(raw, &pm) == nil {
			for _, c := range pm.Containers {
				if c.Name == "loki" {
					usage.CPUCurrentMilli = parseQuantityMilli(c.Usage.CPU)
					usage.MemCurrentBytes = parseQuantityBytes(c.Usage.Memory)
				}
			}
		}
	default:
		usage.MetricsNote = "无法解析 metrics-server 返回"
	}

	usage.buildHints()
	return usage, nil
}

// explainMetricsError 把 RBAC/安装问题翻译成可执行的提示。
func explainMetricsError(err error) string {
	msg := strings.ToLower(err.Error())
	switch {
	case strings.Contains(msg, "forbidden") || strings.Contains(msg, "cannot get resource"):
		return "当前集群凭证缺少 metrics.k8s.io 权限，看不到实时用量。需要给该 ServiceAccount 增加：" +
			"apiGroups=[\"metrics.k8s.io\"] resources=[\"pods\"] verbs=[\"get\",\"list\"]（其余限额/就绪数据仍可正常显示）"
	case strings.Contains(msg, "not found") || strings.Contains(msg, "could not find the requested resource"):
		return "集群未安装 metrics-server，无法获取实时 CPU/内存用量（限额与就绪状态仍可显示）"
	default:
		return "读取实时用量失败：" + err.Error()
	}
}

// ---------- host-docker ----------

func (s *DeploymentService) dockerUsage(ctx context.Context, d *models.LokiDeployment) (*ResourceUsage, error) {
	if d.Host == nil {
		return nil, fmt.Errorf("部署未关联主机")
	}
	client, err := NewSSHClientWithAuth(HostSSHAuth(d.Host))
	if err != nil {
		return nil, fmt.Errorf("连接部署主机失败：%w", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, 20*time.Second)
	defer cancel()

	name := dockerContainerName(d.ID)
	usage := &ResourceUsage{Mode: d.Mode, Source: "docker", Pod: name, Node: d.Host.HostIP}

	// 容器状态 + 限额（docker run 未指定 --memory/--cpus 时限额为 0 = 不限制）
	inspectFmt := "{{.State.Status}}|{{.RestartCount}}|{{.HostConfig.NanoCpus}}|{{.HostConfig.Memory}}"
	out, stderr, err := client.Execute(ctx, fmt.Sprintf("docker inspect -f '%s' %s 2>&1", inspectFmt, name))
	if err != nil || strings.Contains(out, "No such object") {
		return nil, fmt.Errorf("容器 %s 不存在或主机无法访问：%s", name, strings.TrimSpace(stderr))
	}
	parts := strings.Split(strings.TrimSpace(out), "|")
	if len(parts) >= 4 {
		usage.Ready = parts[0] == "running"
		if n, err := strconv.Atoi(parts[1]); err == nil {
			usage.Restarts = int32(n)
		}
		if nano, err := strconv.ParseInt(parts[2], 10, 64); err == nil && nano > 0 {
			usage.CPULimitMilli = nano / 1e6
		}
		if mem, err := strconv.ParseInt(parts[3], 10, 64); err == nil && mem > 0 {
			usage.MemLimitBytes = mem
		}
		usage.LimitsConfigured = usage.CPULimitMilli > 0 && usage.MemLimitBytes > 0
	}

	// 实时用量：docker stats（一次采样）
	statsFmt := "{{.CPUPerc}}|{{.MemUsage}}"
	out, _, err = client.Execute(ctx, fmt.Sprintf("docker stats --no-stream --format '%s' %s 2>/dev/null", statsFmt, name))
	if err == nil {
		if fields := strings.Split(strings.TrimSpace(out), "|"); len(fields) >= 2 {
			usage.CPUCurrentMilli = int64(parsePercent(fields[0]) * 10) // 1% = 10m
			used, limit := parseDockerMemUsage(fields[1])
			usage.MemCurrentBytes = used
			if usage.MemLimitBytes == 0 {
				usage.MemLimitBytes = limit // 未设限额时 docker 报宿主机内存，作为参考上限
			}
		}
	} else {
		usage.MetricsNote = "docker stats 读取失败：" + err.Error()
	}
	if usage.MetricsNote == "" {
		usage.MetricsNote = "未接入 Prometheus：暂无峰值/限流数据"
	}

	usage.buildHints()
	return usage, nil
}

// ---------- host-binary ----------

func (s *DeploymentService) processUsage(ctx context.Context, d *models.LokiDeployment) (*ResourceUsage, error) {
	if d.Host == nil {
		return nil, fmt.Errorf("部署未关联主机")
	}
	client, err := NewSSHClientWithAuth(HostSSHAuth(d.Host))
	if err != nil {
		return nil, fmt.Errorf("连接部署主机失败：%w", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, 15*time.Second)
	defer cancel()

	usage := &ResourceUsage{Mode: d.Mode, Source: "binary", Pod: "loki", Node: d.Host.HostIP}
	out, _, err := client.Execute(ctx, "ps -eo pcpu,rss,comm --no-headers | awk '$3==\"loki\"{print $1\"|\"$2; exit}'")
	if err != nil || strings.TrimSpace(out) == "" {
		return nil, fmt.Errorf("主机上未找到 loki 进程")
	}
	if fields := strings.Split(strings.TrimSpace(out), "|"); len(fields) >= 2 {
		usage.CPUCurrentMilli = int64(parseFloatSafe(fields[0]) * 10) // %CPU → millicores（单核百分比）
		rssKB, _ := strconv.ParseInt(strings.TrimSpace(fields[1]), 10, 64)
		usage.MemCurrentBytes = rssKB * 1024
		usage.Ready = true
	}
	usage.MetricsNote = "裸进程部署没有 cgroup 限额，只能看实时占用（无峰值/限额对比）"

	usage.buildHints()
	return usage, nil
}

// ---------- 共用：扩容建议 ----------

func (u *ResourceUsage) buildHints() {
	// 峰值需 Prometheus,平台不接入:扩容建议基于 metrics-server 实时值
	cpuRef := u.CPUCurrentMilli
	memRef := u.MemCurrentBytes

	var notes []string
	if u.CPULimitMilli > 0 {
		ratio := float64(cpuRef) / float64(u.CPULimitMilli)
		switch {
		case ratio >= 0.9:
			u.CPUSuggest = fmt.Sprintf("CPU 峰值已达 limit 的 %.0f%%，建议把 CPU limit 提升到 %s 核", ratio*100, formatMilli(nextCPU(u.CPULimitMilli)))
			notes = append(notes, "CPU 打满")
		case ratio >= 0.7:
			u.CPUSuggest = fmt.Sprintf("CPU 峰值占 limit 的 %.0f%%，接近上限，可考虑提前扩容", ratio*100)
			notes = append(notes, "CPU 偏高")
		}
	}
	if u.MemLimitBytes > 0 {
		ratio := float64(memRef) / float64(u.MemLimitBytes)
		switch {
		case ratio >= 0.9:
			u.MemSuggest = fmt.Sprintf("内存峰值已达 limit 的 %.0f%%，有 OOMKilled 风险，建议提升到 %s", ratio*100, formatBytesShort(nextMem(u.MemLimitBytes)))
			notes = append(notes, "内存吃紧")
		case ratio >= 0.75:
			u.MemSuggest = fmt.Sprintf("内存峰值占 limit 的 %.0f%%，接近上限，可考虑提前扩容", ratio*100)
			notes = append(notes, "内存偏高")
		}
	}
	if !u.Ready {
		notes = append(notes, "实例未就绪")
	}

	if len(notes) == 0 {
		if u.LimitsConfigured {
			u.Summary = "资源充足：CPU / 内存均低于 limit 的 70%"
		} else {
			u.Summary = "未配置资源限额（建议设置 CPU / 内存上限，便于判断扩容时机）"
		}
	} else {
		u.Summary = "需要关注：" + strings.Join(notes, "、")
	}
}

// ---------- 单位解析 ----------

// parseQuantityMilli 解析 CPU 用量/限额为毫核。
//
// 注意 metrics-server 返回的 CPU 常常是**纳核**（如 "194533645n" = 194.5 毫核），
// 早先只处理了 "m" 后缀，导致 "194533645" 被当成 194 亿核，
// 页面出现「CPU 已达 limit 的 4863341125%」这种荒谬结论。
func parseQuantityMilli(s string) int64 {
	s = strings.TrimSpace(s)
	if s == "" || s == "0" {
		return 0
	}
	switch {
	case strings.HasSuffix(s, "n"): // 纳核
		return int64(parseFloatSafe(strings.TrimSuffix(s, "n")) / 1e6)
	case strings.HasSuffix(s, "u"): // 微核
		return int64(parseFloatSafe(strings.TrimSuffix(s, "u")) / 1e3)
	case strings.HasSuffix(s, "m"): // 毫核
		return int64(parseFloatSafe(strings.TrimSuffix(s, "m")))
	default: // 整核
		return int64(parseFloatSafe(s) * 1000)
	}
}

func parseQuantityBytes(s string) int64 {
	s = strings.TrimSpace(s)
	if s == "" {
		return 0
	}
	units := []struct {
		suffix string
		mul    float64
	}{
		{"Gi", 1024 * 1024 * 1024}, {"Mi", 1024 * 1024}, {"Ki", 1024},
		{"G", 1e9}, {"M", 1e6}, {"K", 1e3},
	}
	for _, u := range units {
		if strings.HasSuffix(s, u.suffix) {
			return int64(parseFloatSafe(strings.TrimSuffix(s, u.suffix)) * u.mul)
		}
	}
	return int64(parseFloatSafe(s))
}

func parseFloatSafe(s string) float64 {
	var f float64
	if _, err := fmt.Sscanf(strings.TrimSpace(s), "%g", &f); err != nil {
		return 0
	}
	return f
}

// parsePercent 解析 "0.15%" / "12.5%" → 数值百分比
func parsePercent(s string) float64 {
	return parseFloatSafe(strings.TrimSuffix(strings.TrimSpace(s), "%"))
}

// parseDockerMemUsage 解析 docker stats 的 "120MiB / 7.6GiB" → (used, limit)
func parseDockerMemUsage(s string) (int64, int64) {
	parts := strings.Split(s, "/")
	if len(parts) != 2 {
		return 0, 0
	}
	return parseDockerSize(parts[0]), parseDockerSize(parts[1])
}

func parseDockerSize(s string) int64 {
	s = strings.TrimSpace(s)
	units := []struct {
		suffix string
		mul    float64
	}{
		{"GiB", 1024 * 1024 * 1024}, {"MiB", 1024 * 1024}, {"KiB", 1024},
		{"GB", 1e9}, {"MB", 1e6}, {"KB", 1e3}, {"B", 1},
	}
	for _, u := range units {
		if strings.HasSuffix(s, u.suffix) {
			return int64(parseFloatSafe(strings.TrimSuffix(s, u.suffix)) * u.mul)
		}
	}
	return int64(parseFloatSafe(s))
}

func nextCPU(currentMilli int64) int64 {
	for _, c := range []int64{1000, 2000, 4000, 6000, 8000, 16000} {
		if c > currentMilli {
			return c
		}
	}
	return currentMilli * 2
}

func nextMem(currentBytes int64) int64 {
	for _, g := range []int64{2, 4, 8, 16, 32, 64} {
		if g*1024*1024*1024 > currentBytes {
			return g * 1024 * 1024 * 1024
		}
	}
	return currentBytes * 2
}

func formatMilli(milli int64) string {
	if milli%1000 == 0 {
		return fmt.Sprintf("%d", milli/1000)
	}
	return fmt.Sprintf("%.1f", float64(milli)/1000)
}

func formatBytesShort(b int64) string {
	if b >= 1024*1024*1024 {
		return fmt.Sprintf("%dGi", b/(1024*1024*1024))
	}
	return fmt.Sprintf("%dMi", b/(1024*1024))
}