package handler

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	"go-backend/internal/http/response"
	"go-backend/internal/panelupgrade"
)

const (
	panelDeployDirEnv                 = "PANEL_DEPLOY_DIR"
	panelBackendContainerEnv          = "PANEL_BACKEND_CONTAINER"
	defaultPanelDeployDir             = "/opt/flvx-panel"
	defaultPanelBackendName           = "flux-panel-backend"
	dockerSocketPath                  = "/var/run/docker.sock"
	maxSystemUpgradeComposeAssetBytes = 1 << 20
	systemUpgradeMessage              = "升级 helper 已启动，面板服务将短暂重启"
	systemUpgradeConflictError        = "已有面板升级任务执行中"
)

var safeBackendContainerPattern = regexp.MustCompile(`^[A-Za-z0-9_.-]+$`)
var enableIPv6ComposePattern = regexp.MustCompile(`(?im)^\s*enable_ipv6\s*:\s*['"]?true['"]?\s*(?:#.*)?$`)
var systemUpgradeReleaseBaseURL = githubHTMLBase
var systemUpgradeAPIBaseURL = githubAPIBase
var systemUpgradeHTTPGet = func(client *http.Client, url string) (*http.Response, error) {
	return client.Get(url)
}

type systemUpgradeExecutor struct {
	deployDir        string
	backendContainer string
}

type systemUpgradeCapabilityData struct {
	Capable          bool     `json:"capable"`
	Reasons          []string `json:"reasons"`
	DeployDir        string   `json:"deployDir"`
	BackendContainer string   `json:"backendContainer"`
}

type systemUpgradeReleaseData struct {
	Version     string `json:"version"`
	Name        string `json:"name"`
	PublishedAt string `json:"publishedAt"`
	Prerelease  bool   `json:"prerelease"`
	Channel     string `json:"channel"`
}

type systemUpgradeVersionData struct {
	CurrentVersion string                      `json:"currentVersion"`
	LatestVersion  string                      `json:"latestVersion"`
	HasUpdate      bool                        `json:"hasUpdate"`
	Channel        string                      `json:"channel"`
	Reason         string                      `json:"reason,omitempty"`
	Capability     systemUpgradeCapabilityData `json:"capability"`
}

type systemUpgradeCheckData struct {
	CurrentVersion string                      `json:"currentVersion"`
	LatestVersion  string                      `json:"latestVersion"`
	HasUpdate      bool                        `json:"hasUpdate"`
	Channel        string                      `json:"channel"`
	Capability     systemUpgradeCapabilityData `json:"capability"`
	Releases       []systemUpgradeReleaseData  `json:"releases"`
}

type systemUpgradeRunData struct {
	JobID           string `json:"jobId"`
	Version         string `json:"version"`
	Channel         string `json:"channel"`
	ComposeAsset    string `json:"composeAsset"`
	HelperContainer string `json:"helperContainer"`
	BackendImageID  string `json:"backendImageId"`
	Message         string `json:"message"`
}

type systemUpgradeRequest struct {
	Version string `json:"version"`
	Channel string `json:"channel"`
}

func newSystemUpgradeExecutor() *systemUpgradeExecutor {
	deployDir := strings.TrimSpace(os.Getenv(panelDeployDirEnv))
	if deployDir == "" {
		deployDir = defaultPanelDeployDir
	}
	backendContainer := strings.TrimSpace(os.Getenv(panelBackendContainerEnv))
	if backendContainer == "" {
		backendContainer = defaultPanelBackendName
	}
	return &systemUpgradeExecutor{deployDir: deployDir, backendContainer: backendContainer}
}

func currentPanelVersion() string {
	version := strings.TrimSpace(os.Getenv("FLUX_VERSION"))
	if version == "" {
		return "dev"
	}
	return version
}

func validateBackendContainerName(value string) error {
	if value == "" {
		return fmt.Errorf("backend container name is empty")
	}
	if !safeBackendContainerPattern.MatchString(value) {
		return fmt.Errorf("unsafe backend container name: %s", value)
	}
	return nil
}

func validateUpgradeVersion(value string) error { return panelupgrade.ValidateVersion(value) }

func (e *systemUpgradeExecutor) composePath() string {
	return filepath.Join(e.deployDir, "docker-compose.yml")
}
func (e *systemUpgradeExecutor) envPath() string { return filepath.Join(e.deployDir, ".env") }

func (e *systemUpgradeExecutor) capability(ctx context.Context) systemUpgradeCapabilityData {
	ctx, cancel := context.WithTimeout(ctx, 15*time.Second)
	defer cancel()
	reasons := make([]string, 0)
	if !filepath.IsAbs(e.deployDir) {
		reasons = append(reasons, "部署目录必须是绝对路径")
	}
	if err := validateBackendContainerName(e.backendContainer); err != nil {
		reasons = append(reasons, err.Error())
	}
	if err := exec.CommandContext(ctx, "docker", "--version").Run(); err != nil {
		reasons = append(reasons, "docker CLI不可用")
	}
	if info, err := os.Stat(dockerSocketPath); err != nil {
		reasons = append(reasons, "docker socket不可用: "+err.Error())
	} else if info.IsDir() {
		reasons = append(reasons, "docker socket路径不是文件")
	}
	if info, err := os.Stat(e.composePath()); err != nil {
		reasons = append(reasons, "部署docker-compose.yml不可用: "+err.Error())
	} else if info.IsDir() {
		reasons = append(reasons, "部署docker-compose.yml不是文件")
	}
	if info, err := os.Stat(e.envPath()); err != nil {
		reasons = append(reasons, "部署.env不可用: "+err.Error())
	} else if info.IsDir() {
		reasons = append(reasons, "部署.env不是文件")
	}
	if err := exec.CommandContext(ctx, "docker", "compose", "version").Run(); err != nil {
		reasons = append(reasons, "docker compose不可用")
	}
	if _, err := (panelupgrade.Manager{Dir: e.deployDir, Backend: e.backendContainer}).Identity(ctx); err != nil {
		reasons = append(reasons, err.Error())
	}

	return systemUpgradeCapabilityData{
		Capable:          len(reasons) == 0,
		Reasons:          reasons,
		DeployDir:        e.deployDir,
		BackendContainer: e.backendContainer,
	}
}

func (e *systemUpgradeExecutor) selectComposeAsset(current []byte) string {
	if enableIPv6ComposePattern.Match(current) {
		return "docker-compose-v6.yml"
	}
	return "docker-compose-v4.yml"
}

func (h *Handler) buildSystemUpgradeDownloadURL(version, filename string) string {
	enabled, proxyURL := h.getGithubProxyConfig()
	base := fmt.Sprintf("%s/%s/releases/download/%s/%s", strings.TrimRight(systemUpgradeReleaseBaseURL, "/"), githubRepo, version, filename)
	if enabled {
		return fmt.Sprintf("%s/%s", proxyURL, base)
	}
	return base
}

func (h *Handler) fetchSystemUpgradeReleases(perPage int) ([]githubRelease, error) {
	if perPage <= 0 {
		perPage = 20
	}

	client := &http.Client{Timeout: 15 * time.Second}
	url := fmt.Sprintf("%s/repos/%s/releases?per_page=%d", strings.TrimRight(systemUpgradeAPIBaseURL, "/"), githubRepo, perPage)
	if enabled, proxyURL := h.getGithubProxyConfig(); enabled {
		url = fmt.Sprintf("%s/%s", proxyURL, url)
	}

	resp, err := systemUpgradeHTTPGet(client, url)
	if err != nil {
		return nil, fmt.Errorf("请求GitHub API失败: %v", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
		return nil, fmt.Errorf("GitHub API返回 %d: %s", resp.StatusCode, string(body))
	}

	var releases []githubRelease
	if err := json.NewDecoder(resp.Body).Decode(&releases); err != nil {
		return nil, fmt.Errorf("解析GitHub API响应失败: %v", err)
	}

	return releases, nil
}

func (h *Handler) resolveSystemUpgradeLatestReleaseByChannel(channel string) (string, error) {
	normalizedChannel := normalizeReleaseChannel(channel)
	releases, err := h.fetchSystemUpgradeReleases(50)
	if err != nil {
		return "", err
	}

	for _, r := range releases {
		if r.Draft {
			continue
		}
		tag := strings.TrimSpace(r.TagName)
		if tag == "" {
			continue
		}
		if releaseChannelFromTag(tag) == normalizedChannel {
			return tag, nil
		}
	}

	return "", fmt.Errorf("未找到%s版本号", releaseChannelLabel(normalizedChannel))
}

func (h *Handler) downloadReleaseAsset(version, filename string) ([]byte, error) {
	url := h.buildSystemUpgradeDownloadURL(version, filename)
	client := &http.Client{Timeout: 60 * time.Second}
	resp, err := systemUpgradeHTTPGet(client, url)
	if err != nil {
		return nil, fmt.Errorf("下载%s失败: %v", filename, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
		return nil, fmt.Errorf("下载%s返回 %d: %s", filename, resp.StatusCode, strings.TrimSpace(string(body)))
	}
	body, err := io.ReadAll(io.LimitReader(resp.Body, maxSystemUpgradeComposeAssetBytes+1))
	if err != nil {
		return nil, fmt.Errorf("读取%s失败: %v", filename, err)
	}
	if len(body) > maxSystemUpgradeComposeAssetBytes {
		return nil, fmt.Errorf("下载%s过大", filename)
	}
	if len(bytes.TrimSpace(body)) == 0 {
		return nil, fmt.Errorf("下载%s内容为空", filename)
	}
	return body, nil
}

func releasesForChannel(releases []githubRelease, channel string) []systemUpgradeReleaseData {
	channel = normalizeReleaseChannel(channel)
	items := make([]systemUpgradeReleaseData, 0, len(releases))
	for _, r := range releases {
		if r.Draft {
			continue
		}
		tag := strings.TrimSpace(r.TagName)
		if tag == "" {
			continue
		}
		itemChannel := releaseChannelFromTag(tag)
		if itemChannel != channel {
			continue
		}
		items = append(items, systemUpgradeReleaseData{
			Version:     tag,
			Name:        r.Name,
			PublishedAt: r.PublishedAt,
			Prerelease:  itemChannel == releaseChannelDev,
			Channel:     itemChannel,
		})
	}
	return items
}

func decodeSystemUpgradeRequest(r *http.Request, req *systemUpgradeRequest) error {
	defer r.Body.Close()
	body, err := io.ReadAll(io.LimitReader(r.Body, 4097))
	if err != nil {
		return err
	}
	if len(body) > 4096 {
		return fmt.Errorf("request too large")
	}
	if len(bytes.TrimSpace(body)) == 0 {
		return nil
	}
	decoder := json.NewDecoder(bytes.NewReader(body))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(req); err != nil {
		return err
	}
	var extra any
	if decoder.Decode(&extra) != io.EOF {
		return fmt.Errorf("unexpected trailing JSON")
	}
	return nil
}

func systemUpgradeVersionResponse(current, channel, latest string, lookupErr error, capability systemUpgradeCapabilityData) systemUpgradeVersionData {
	data := systemUpgradeVersionData{
		CurrentVersion: current,
		LatestVersion:  latest,
		HasUpdate:      latest != "" && latest != current,
		Channel:        channel,
		Capability:     capability,
	}
	if lookupErr != nil {
		data.LatestVersion = ""
		data.HasUpdate = false
		data.Reason = lookupErr.Error()
	}
	return data
}

func (h *Handler) systemVersion(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		response.WriteJSON(w, response.ErrDefault("请求失败"))
		return
	}

	channel := releaseChannelStable
	current := currentPanelVersion()
	exec := newSystemUpgradeExecutor()
	capability := exec.capability(r.Context())
	latest, err := h.resolveSystemUpgradeLatestReleaseByChannel(channel)
	response.WriteJSON(w, response.OK(systemUpgradeVersionResponse(current, channel, latest, err, capability)))
}

func (h *Handler) systemCheckUpdates(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		response.WriteJSON(w, response.ErrDefault("请求失败"))
		return
	}

	var req systemUpgradeRequest
	if err := decodeSystemUpgradeRequest(r, &req); err != nil {
		response.WriteJSON(w, response.ErrDefault("请求参数错误"))
		return
	}
	channel := normalizeReleaseChannel(req.Channel)
	current := currentPanelVersion()
	exec := newSystemUpgradeExecutor()
	capability := exec.capability(r.Context())

	githubReleases, err := h.fetchSystemUpgradeReleases(50)
	if err != nil {
		response.WriteJSON(w, response.Err(-2, fmt.Sprintf("获取版本列表失败: %v", err)))
		return
	}
	releases := releasesForChannel(githubReleases, channel)
	latest := ""
	if len(releases) > 0 {
		latest = releases[0].Version
	}
	response.WriteJSON(w, response.OK(systemUpgradeCheckData{
		CurrentVersion: current,
		LatestVersion:  latest,
		HasUpdate:      latest != "" && latest != current,
		Channel:        channel,
		Capability:     capability,
		Releases:       releases,
	}))
}

func (h *Handler) systemUpgrade(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		response.WriteJSON(w, response.ErrDefault("请求失败"))
		return
	}
	if !h.systemUpgradeMu.TryLock() {
		response.WriteJSON(w, response.ErrDefault(systemUpgradeConflictError))
		return
	}
	defer h.systemUpgradeMu.Unlock()

	var req systemUpgradeRequest
	if err := decodeSystemUpgradeRequest(r, &req); err != nil {
		response.WriteJSON(w, response.ErrDefault("请求参数错误"))
		return
	}
	channel := normalizeReleaseChannel(req.Channel)
	exec := newSystemUpgradeExecutor()
	capability := exec.capability(r.Context())
	if !capability.Capable {
		response.WriteJSON(w, response.ErrDefault("当前环境不支持面板自升级: "+strings.Join(capability.Reasons, "; ")))
		return
	}
	version := strings.TrimSpace(req.Version)
	if version == "" {
		var err error
		version, err = h.resolveSystemUpgradeLatestReleaseByChannel(channel)
		if err != nil {
			response.WriteJSON(w, response.Err(-2, fmt.Sprintf("获取最新%s失败: %v", releaseChannelLabel(channel), err)))
			return
		}
	}

	if err := validateUpgradeVersion(version); err != nil {
		response.WriteJSON(w, response.ErrDefault("版本号格式无效"))
		return
	}
	composeData, err := os.ReadFile(exec.composePath())
	if err != nil {
		response.WriteJSON(w, response.ErrDefault("读取部署配置失败"))
		return
	}
	composeAsset := exec.selectComposeAsset(composeData)
	newCompose, err := h.downloadReleaseAsset(version, composeAsset)
	if err != nil {
		response.WriteJSON(w, response.ErrDefault("下载目标 Compose 失败"))
		return
	}
	// A detached helper must not be canceled when the browser disconnects.
	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
	defer cancel()
	job, imageID, err := (panelupgrade.Manager{Dir: exec.deployDir, Backend: exec.backendContainer}).Start(ctx, version, newCompose)
	if err != nil {
		response.WriteJSON(w, response.ErrDefault(err.Error()))
		return
	}
	response.WriteJSON(w, response.OK(systemUpgradeRunData{JobID: job.ID, Version: version, Channel: channel, ComposeAsset: composeAsset, HelperContainer: job.HelperContainer, BackendImageID: imageID, Message: systemUpgradeMessage}))
}

func (h *Handler) systemUpgradeStatus(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		response.WriteJSON(w, response.ErrDefault("请求失败"))
		return
	}
	var req struct {
		JobID string `json:"jobId"`
	}
	defer r.Body.Close()
	decoder := json.NewDecoder(io.LimitReader(r.Body, 4097))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&req); err != nil && err != io.EOF {
		response.WriteJSON(w, response.ErrDefault("请求参数错误"))
		return
	}
	var extra any
	if decoder.Decode(&extra) != io.EOF {
		response.WriteJSON(w, response.ErrDefault("请求参数错误"))
		return
	}
	e := newSystemUpgradeExecutor()
	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
	defer cancel()
	job, err := (panelupgrade.Manager{Dir: e.deployDir, Backend: e.backendContainer}).Status(ctx, req.JobID)
	if err != nil {
		response.WriteJSON(w, response.ErrDefault("无法读取升级任务状态"))
		return
	}
	response.WriteJSON(w, response.OK(struct {
		CurrentVersion string            `json:"currentVersion"`
		Job            *panelupgrade.Job `json:"job"`
	}{currentPanelVersion(), job}))
}