package backendupdate

import (
	"encoding/json"

	"yms-daemon/internal/hostnginx"
	"yms-daemon/internal/transaction"
)

// gatewaySwitchIntent 构造原生后端 Nginx 上游切换步骤的意图，记录切换前、
// 切换后各自的端口与配置摘要，供审计与回放时确认两侧快照一致。
func gatewaySwitchIntent(request persistedRequest, before hostnginx.Snapshot, after hostnginx.Snapshot) transaction.StepIntent {
	return stepIntent("backend.gateway.switch", "switch host Nginx backend upstream", struct {
		BeforePort int    `json:"beforePort"`
		BeforeHash string `json:"beforeHash"`
		AfterPort  int    `json:"afterPort"`
		AfterHash  string `json:"afterHash"`
	}{before.ActivePort, snapshotDigest(before), after.ActivePort, snapshotDigest(after)})
}

// activeLinkIntent 构造替换原生后端兼容性链接步骤的意图，记录链接路径、
// 更新前状态以及即将指向的安装路径。
func activeLinkIntent(request persistedRequest, installedPath string) transaction.StepIntent {
	return stepIntent("backend.native.active-link", "replace backend compatibility link", struct {
		Path          string    `json:"path"`
		Before        pathState `json:"before"`
		InstalledPath string    `json:"installedPath"`
	}{request.ActiveJARPath, request.ActiveJARBefore, installedPath})
}

// stopPreviousUnitIntent 构造停止前一原生后端单元的步骤意图，记录待停止单元名。
func stopPreviousUnitIntent(request persistedRequest) transaction.StepIntent {
	return stepIntent("backend.previous-unit.stop", "stop previous backend unit after drain", struct {
		Unit string `json:"unit"`
	}{request.PreviousUnit})
}

// activeLinkRestoreIntent 构造恢复原生后端兼容性链接步骤的意图，记录链接
// 路径及其更新前状态，供补偿流程回滚。
func activeLinkRestoreIntent(request persistedRequest) transaction.StepIntent {
	return stepIntent("backend.native.active-link.restore", "restore backend compatibility path", struct {
		Path   string    `json:"path"`
		Before pathState `json:"before"`
	}{request.ActiveJARPath, request.ActiveJARBefore})
}

// gatewayRestoreIntent 构造恢复原生后端 Nginx 上游步骤的意图，记录需恢复到的端口。
func gatewayRestoreIntent(request persistedRequest) transaction.StepIntent {
	return stepIntent("backend.gateway.restore", "restore host Nginx backend upstream", struct {
		Port int `json:"port"`
	}{request.PreviousGatewayPort})
}

// stopTargetUnitIntent 构造停止被补偿的原生后端目标单元步骤的意图，记录待停止单元名。
func stopTargetUnitIntent(request persistedRequest) transaction.StepIntent {
	return stepIntent("backend.target-unit.stop", "stop compensated backend target unit", struct {
		Unit string `json:"unit"`
	}{request.TargetUnit})
}

// restoreTargetSlotIntent 构造恢复被补偿的原生后端目标槽位步骤的意图，记录
// 槽位链接路径、其安装路径以及更新前的链接目标。
func restoreTargetSlotIntent(request persistedRequest, installedPath string) transaction.StepIntent {
	return stepIntent("backend.target-slot.restore", "restore compensated backend target slot", struct {
		Path           string `json:"path"`
		InstalledPath  string `json:"installedPath"`
		PreviousTarget string `json:"previousTarget"`
	}{request.TargetSlotJAR, installedPath, request.PreviousSlotTarget})
}

// stepIntent 以键名、显示名和任意值构造一个事务步骤意图。意图值会被序列化为
// JSON；若序列化失败则直接 panic，因为该失败属于程序缺陷而非运行期错误。
func stepIntent(key string, name string, value any) transaction.StepIntent {
	content, err := json.Marshal(value)
	if err != nil {
		panic(err)
	}
	return transaction.StepIntent{Key: key, Name: name, Intent: content}
}