package services

import (
	"encoding/json"
	"fmt"
	"path"
	"strings"
)

type sidecarLogMount struct {
	containerName    string
	volumeName       string
	mountPath        string
	subPath          string
	createVolume     bool
	mountApplication bool
}

type sidecarDeployment struct {
	Spec struct {
		Template struct {
			Spec struct {
				Containers []struct {
					Name         string `json:"name"`
					VolumeMounts []struct {
						Name        string `json:"name"`
						MountPath   string `json:"mountPath"`
						SubPath     string `json:"subPath"`
						SubPathExpr string `json:"subPathExpr"`
						ReadOnly    bool   `json:"readOnly"`
					} `json:"volumeMounts"`
				} `json:"containers"`
				Volumes []struct {
					Name string `json:"name"`
				} `json:"volumes"`
			} `json:"spec"`
		} `json:"template"`
	} `json:"spec"`
}

// resolveSidecarLogMount 优先复用业务容器已有的卷；否则仅在专用日志目录创建共享 emptyDir。
func resolveSidecarLogMount(deploymentJSON []byte, target, logPath string, collectorID uint) (sidecarLogMount, error) {
	var deployment sidecarDeployment
	if err := json.Unmarshal(deploymentJSON, &deployment); err != nil {
		return sidecarLogMount{}, fmt.Errorf("读取目标 Deployment 失败: %w", err)
	}
	logDir := path.Dir(strings.TrimSpace(logPath))
	if !path.IsAbs(logPath) || logDir == "/" || strings.ContainsAny(logDir, "*?[]\n\r") {
		return sidecarLogMount{}, fmt.Errorf("Sidecar 采集路径需为专用目录下的绝对文件路径或 glob，例如 /var/log/app/*.log")
	}

	containers := deployment.Spec.Template.Spec.Containers
	var appIndex = -1
	var candidate = -1
	for i, container := range containers {
		if container.Name == target {
			appIndex = i
			break
		}
		if container.Name != "fluent-bit" {
			if candidate >= 0 {
				candidate = -2
			} else if candidate == -1 {
				candidate = i
			}
		}
	}
	if appIndex < 0 {
		appIndex = candidate
	}
	if appIndex < 0 {
		return sidecarLogMount{}, fmt.Errorf("目标 Deployment 中无法确定业务容器，请使容器名与 Deployment 名一致，或仅保留一个业务容器")
	}
	app := containers[appIndex]
	mount := sidecarLogMount{containerName: app.Name}
	longest := -1
	for _, item := range app.VolumeMounts {
		prefix := strings.TrimSuffix(item.MountPath, "/")
		if (logDir == prefix || strings.HasPrefix(logDir, prefix+"/")) && len(prefix) > longest {
			if item.ReadOnly || item.SubPathExpr != "" {
				return sidecarLogMount{}, fmt.Errorf("业务容器的日志卷必须可写，且不能使用 subPathExpr")
			}
			mount.volumeName = item.Name
			mount.mountPath = item.MountPath
			mount.subPath = item.SubPath
			longest = len(prefix)
		}
	}
	if mount.volumeName != "" {
		if mount.mountPath == "/tmp" {
			return sidecarLogMount{}, fmt.Errorf("日志卷不能挂载在 /tmp：Fluent Bit 用此目录保存读取位置；请改用专用日志目录")
		}
		return mount, nil
	}

	// 自动挂载会遮蔽目录原有内容，仅对明确的专用日志目录执行。
	if logDir != "/var/log/app" && path.Base(logDir) != "logs" && path.Base(logDir) != "log" {
		return sidecarLogMount{}, fmt.Errorf("业务容器未共享 %s；请将采集路径改为 /var/log/app/*.log 或已有日志卷中的文件", logDir)
	}
	volumeName := fmt.Sprintf("loki-collector-logs-%d", collectorID)
	for _, volume := range deployment.Spec.Template.Spec.Volumes {
		if volume.Name == volumeName {
			return sidecarLogMount{}, fmt.Errorf("卷 %s 已存在但业务容器未挂载，请先检查目标 Deployment", volumeName)
		}
	}
	mount.volumeName = volumeName
	mount.mountPath = logDir
	mount.createVolume = true
	mount.mountApplication = true
	return mount, nil
}

// sidecarRemovePatchYAML 只清理该采集策略注入的卷，保留业务原有的日志卷。
func sidecarRemovePatchYAML(deploymentJSON []byte, collectorID uint) (string, error) {
	var deployment sidecarDeployment
	if err := json.Unmarshal(deploymentJSON, &deployment); err != nil {
		return "", fmt.Errorf("读取目标 Deployment 失败: %w", err)
	}
	injectedName := fmt.Sprintf("loki-collector-logs-%d", collectorID)
	appPatch := ""
	for _, container := range deployment.Spec.Template.Spec.Containers {
		if container.Name == "fluent-bit" {
			continue
		}
		for _, mount := range container.VolumeMounts {
			if mount.Name == injectedName {
				appPatch += fmt.Sprintf("      - name: %s\n        volumeMounts:\n        - mountPath: %q\n          $patch: delete\n", container.Name, mount.MountPath)
			}
		}
	}
	volumePatch := ""
	for _, volume := range deployment.Spec.Template.Spec.Volumes {
		if volume.Name == injectedName {
			volumePatch = fmt.Sprintf("      - name: %s\n        $patch: delete\n", injectedName)
			break
		}
	}
	return fmt.Sprintf(`spec:
  template:
    spec:
      containers:
      - name: fluent-bit
        $patch: delete
%s      volumes:
      - name: fluent-bit-config
        $patch: delete
      - name: fluent-bit-state
        $patch: delete
%s`, appPatch, volumePatch), nil
}