package backendstatus

import (
	"context"
	"errors"
	"fmt"

	"yms-daemon/internal/containerengine"
	"yms-daemon/internal/daemonapi"
	"yms-daemon/internal/deploymentconfig"
	"yms-daemon/internal/transaction"
)

// 诊断项稳定标识，供测试与 reconcile 识别，不参与展示。
const (
	codeUndeployed                = "container_backend_undeployed"
	codeUndeployedWithHistory     = "container_backend_undeployed_with_history"
	codeContainerWithoutRecord    = "container_present_without_deployment_record"
	codeCommittedPortOK           = "nginx_active_port"
	codeNginxWrongPort            = "nginx_wrong_port"
	codeActiveContainerOK         = "active_container_healthy"
	codeActiveContainerMissing    = "active_container_missing"
	codeActiveContainerIdentity   = "active_container_identity_mismatch"
	codeActiveContainerNotRunning = "active_container_not_running"
	codeInactiveContainerOK       = "inactive_container_absent"
	codeInactiveContainerResidual = "inactive_container_residual"
	codeInactiveContainerRunning  = "inactive_container_running"
	codeDeploymentConfigMismatch  = "deployment_record_config_mismatch"
)

// diagnoseContainer 对 container 后端做只读诊断。
// 事实来源是 backend_container_deployment 单例记录；现场状态由容器引擎与宿主 Nginx 提供。
func (d *Diagnoser) diagnoseContainer(ctx context.Context) (daemonapi.Diagnosis, error) {
	findings, err := d.containerGather(ctx)
	if err != nil {
		return daemonapi.Diagnosis{}, err
	}
	return toDiagnosis("backend", deploymentconfig.BackendTypeContainer, findings), nil
}

// containerGather 读取 container 后端的部署记录、历史事务与宿主 Nginx 状态，生成全部诊断项。
func (d *Diagnoser) containerGather(ctx context.Context) ([]finding, error) {
	deployment, depErr := d.store.BackendContainerDeployment(ctx)
	hasDeployment := depErr == nil
	if depErr != nil && !errors.Is(depErr, transaction.ErrNotFound) {
		return nil, fmt.Errorf("read backend container deployment: %w", depErr)
	}
	hasHistory, err := d.store.HasCommittedBackendContainerTransactionHistory(ctx)
	if err != nil {
		return nil, err
	}
	before, err := d.gateway.Read()
	if err != nil {
		return nil, fmt.Errorf("read host Nginx configuration: %w", err)
	}
	return d.containerFindings(ctx, deployment, hasDeployment, hasHistory, before.ActivePort)
}

// containerFindings 生成 container 后端的全部诊断项。
// deployment 部署记录，hasDeployment 表示是否存在该记录，hasHistory 表示是否存在历史
// 已提交事务，activePort 是宿主 Nginx 当前指向的后端端口。
func (d *Diagnoser) containerFindings(ctx context.Context, deployment transaction.BackendContainerDeployment, hasDeployment bool, hasHistory bool, activePort int) ([]finding, error) {
	if !hasDeployment {
		return d.containerUndeployedFindings(ctx, hasHistory)
	}

	findings := make([]finding, 0, 6)

	committedSlot, err := d.config.Backend.SlotForPort(deployment.ActivePort)
	if err != nil {
		return nil, err
	}
	if deployment.ContainerName != committedSlot.ContainerName {
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeDeploymentConfigMismatch,
			message: fmt.Sprintf("部署记录容器 %s 与活动端口 %d 的槽位容器 %s 不一致", deployment.ContainerName, deployment.ActivePort, committedSlot.ContainerName),
		})
		return findings, nil
	}

	committedContainer, committedErr := d.engine.InspectContainer(ctx, deployment.ContainerName)
	committedHealthy := false
	switch {
	case errors.Is(committedErr, containerengine.ErrNotFound):
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeActiveContainerMissing,
			message: "部署记录的活动容器 " + deployment.ContainerName + " 不存在",
		})
	case committedErr != nil:
		return nil, fmt.Errorf("inspect committed backend container %s: %w", deployment.ContainerName, committedErr)
	case committedContainer.ID != deployment.ContainerID:
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeActiveContainerIdentity,
			message: "活动容器 " + deployment.ContainerName + " 身份与部署记录不一致",
		})
	case !committedContainer.Running || committedContainer.Dead:
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeActiveContainerNotRunning,
			message: "活动容器 " + deployment.ContainerName + " 未运行",
		})
	default:
		committedHealthy = true
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelOK,
			code:    codeActiveContainerOK,
			message: "活动容器 " + deployment.ContainerName + " 健康",
		})
	}

	if activePort == deployment.ActivePort {
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelOK,
			code:    codeCommittedPortOK,
			message: fmt.Sprintf("宿主 Nginx 指向部署记录的活动端口 %d", deployment.ActivePort),
		})
	} else if committedHealthy {
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelFixable,
			code:    codeNginxWrongPort,
			message: fmt.Sprintf("宿主 Nginx 指向 %d，但部署记录的活动端口是 %d", activePort, deployment.ActivePort),
			action:  fmt.Sprintf("将宿主 Nginx 切流到端口 %d", deployment.ActivePort),
			fix:     &fixAction{kind: fixSwitchPort, port: deployment.ActivePort},
		})
	} else {
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeNginxWrongPort,
			message: fmt.Sprintf("宿主 Nginx 指向 %d，与部署记录活动端口 %d 不一致，且活动容器不健康", activePort, deployment.ActivePort),
		})
	}

	inactiveSlot, err := d.config.Backend.SlotForPort(otherPort(deployment.ActivePort))
	if err != nil {
		return nil, err
	}
	inactiveContainer, inactiveErr := d.engine.InspectContainer(ctx, inactiveSlot.ContainerName)
	switch {
	case errors.Is(inactiveErr, containerengine.ErrNotFound):
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelOK,
			code:    codeInactiveContainerOK,
			message: "非活动槽位容器 " + inactiveSlot.ContainerName + " 不存在",
		})
	case inactiveErr != nil:
		return nil, fmt.Errorf("inspect inactive backend container %s: %w", inactiveSlot.ContainerName, inactiveErr)
	case inactiveContainer.Running && !inactiveContainer.Dead:
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeInactiveContainerRunning,
			message: "非活动槽位容器 " + inactiveSlot.ContainerName + " 意外处于运行状态",
		})
	default:
		findings = append(findings, finding{
			level:   daemonapi.DiagnosisLevelFixable,
			code:    codeInactiveContainerResidual,
			message: "非活动槽位容器 " + inactiveSlot.ContainerName + " 已停止，属于残留",
			action:  "移除残留的已停止容器 " + inactiveSlot.ContainerName,
			fix:     &fixAction{kind: fixRemoveContainer, container: inactiveSlot.ContainerName},
		})
	}

	return findings, nil
}

// containerUndeployedFindings 处理不存在部署记录的情况，依据容器现场与历史记录判断是否为全新机器。
func (d *Diagnoser) containerUndeployedFindings(ctx context.Context, hasHistory bool) ([]finding, error) {
	var present []string
	for _, port := range []int{deploymentconfig.BackendPort8080, deploymentconfig.BackendPort8081} {
		slot, err := d.config.Backend.SlotForPort(port)
		if err != nil {
			return nil, err
		}
		if _, err := d.engine.InspectContainer(ctx, slot.ContainerName); err == nil {
			present = append(present, slot.ContainerName)
		} else if !errors.Is(err, containerengine.ErrNotFound) {
			return nil, fmt.Errorf("inspect backend container %s: %w", slot.ContainerName, err)
		}
	}

	if len(present) > 0 {
		return []finding{{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeContainerWithoutRecord,
			message: fmt.Sprintf("SQLite 没有部署记录，但现场存在容器 %v", present),
		}}, nil
	}
	if hasHistory {
		return []finding{{
			level:   daemonapi.DiagnosisLevelDrift,
			code:    codeUndeployedWithHistory,
			message: "存在历史已提交事务，但缺少部署记录且两个槽位容器均不存在",
		}}, nil
	}
	return []finding{{
		level:   daemonapi.DiagnosisLevelOK,
		code:    codeUndeployed,
		message: "全新机器，尚未部署 backend 容器",
	}}, nil
}