package api

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"sync"
	"time"

	"clicd/internal/config"
	"clicd/internal/kvm"
	"clicd/internal/lxc"
)

// ImageInfo represents a template image with its download/enable status.
type ImageInfo struct {
	ID              string `json:"id"`
	Name            string `json:"name"`
	Type            string `json:"type"`
	Distro          string `json:"distro"`
	Release         string `json:"release"`
	Arch            string `json:"arch"`
	Description     string `json:"description"`
	Downloaded      bool   `json:"downloaded"`
	Enabled         bool   `json:"enabled"`
	Downloading     bool   `json:"downloading"`
	Progress        int    `json:"progress"`
	DownloadedBytes int64  `json:"downloaded_bytes"`
	TotalBytes      int64  `json:"total_bytes"`
	Stage           string `json:"stage,omitempty"`
	Error           string `json:"error,omitempty"`
	SizeBytes       int64  `json:"size_bytes"`
	ManualPath      string `json:"manual_path,omitempty"`
	Desktop         string `json:"desktop,omitempty"`
}

var imageDownloadsMu sync.Mutex
var imageDownloads = map[string]*imageDownloadStatus{}

type imageDownloadStatus struct {
	Downloading     bool
	Progress        int
	DownloadedBytes int64
	TotalBytes      int64
	Stage           string
	Error           string
	Cancel          context.CancelFunc
	UpdatedAt       time.Time
}

type imageDownloadSnapshot struct {
	Downloading     bool
	Progress        int
	DownloadedBytes int64
	TotalBytes      int64
	Stage           string
	Error           string
}

func imageDownloadInfo(id string) imageDownloadSnapshot {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	st := imageDownloads[id]
	if st == nil {
		return imageDownloadSnapshot{}
	}
	return imageDownloadSnapshot{
		Downloading:     st.Downloading,
		Progress:        st.Progress,
		DownloadedBytes: st.DownloadedBytes,
		TotalBytes:      st.TotalBytes,
		Stage:           st.Stage,
		Error:           st.Error,
	}
}

func startImageDownload(id, stage string) (context.Context, bool) {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	if st := imageDownloads[id]; st != nil && st.Downloading {
		return nil, false
	}
	ctx, cancel := context.WithCancel(context.Background())
	imageDownloads[id] = &imageDownloadStatus{
		Downloading: true,
		Stage:       stage,
		Cancel:      cancel,
		UpdatedAt:   time.Now(),
	}
	return ctx, true
}

func updateImageDownload(id string, update func(*imageDownloadStatus)) {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	st := imageDownloads[id]
	if st == nil {
		return
	}
	update(st)
	st.UpdatedAt = time.Now()
}

func finishImageDownload(id string, err error) {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	st := imageDownloads[id]
	if st == nil {
		return
	}
	st.Downloading = false
	st.Cancel = nil
	st.UpdatedAt = time.Now()
	if err != nil {
		st.Error = err.Error()
		return
	}
	delete(imageDownloads, id)
}

func clearImageDownload(id string) {
	imageDownloadsMu.Lock()
	delete(imageDownloads, id)
	imageDownloadsMu.Unlock()
}

func isImageDownloadActive(id string) bool {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	st := imageDownloads[id]
	return st != nil && st.Downloading
}

func lxcImageDownloadTempName(id string) string {
	return fmt.Sprintf("clicd-img-dl-%s", id)
}

func cleanupLXCImageDownloadTemp(id string) {
	tmpName := lxcImageDownloadTempName(id)
	exec.Command("lxc-destroy", "-n", tmpName, "-f").Run()
	os.RemoveAll(filepath.Join("/var/lib/lxc", tmpName))
}

func cleanupOldImageDownloadErrors() {
	imageDownloadsMu.Lock()
	defer imageDownloadsMu.Unlock()
	cutoff := time.Now().Add(-10 * time.Minute)
	for id, st := range imageDownloads {
		if !st.Downloading && st.UpdatedAt.Before(cutoff) {
			delete(imageDownloads, id)
		}
	}
}

// isImageDownloaded checks if the LXC download cache exists for a template.
func isImageDownloaded(distro, release, arch string) bool {
	downloaded, _ := imageDownloadedInfo(distro, release, arch)
	return downloaded
}

// imageDownloadedInfo returns whether the image is downloaded and its total size in bytes.
func imageDownloadedInfo(distro, release, arch string) (bool, int64) {
	cachePath := filepath.Join("/var/cache/lxc/download", distro, release, arch)
	info, err := os.Stat(cachePath)
	if err != nil || !info.IsDir() {
		return false, 0
	}
	// Check directly for rootfs.tar.xz (some LXC versions store it here)
	if fi, err := os.Stat(filepath.Join(cachePath, "rootfs.tar.xz")); err == nil {
		return true, fi.Size()
	}
	if fi, err := os.Stat(filepath.Join(cachePath, "meta.tar.xz")); err == nil {
		return true, fi.Size()
	}
	// Check one level deeper (LXC uses variant subdirectories like "default")
	entries, err := os.ReadDir(cachePath)
	if err != nil {
		return false, 0
	}
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		subPath := filepath.Join(cachePath, entry.Name())
		if fi, err := os.Stat(filepath.Join(subPath, "rootfs.tar.xz")); err == nil {
			return true, fi.Size()
		}
		if fi, err := os.Stat(filepath.Join(subPath, "meta.tar.xz")); err == nil {
			return true, fi.Size()
		}
	}
	return false, 0
}

// getEnabledImageSet returns the set of enabled image IDs.
// If none have been explicitly set, all templates are enabled by default.
func getEnabledImageSet() map[string]bool {
	set := make(map[string]bool)
	if len(config.AppConfig.EnabledImages) == 0 {
		for _, t := range lxc.GetTemplates() {
			set[t.ID] = true
		}
		for _, t := range kvm.GetImages() {
			set[t.ID] = true
		}
	} else {
		for _, id := range config.AppConfig.EnabledImages {
			set[id] = true
		}
	}
	return set
}

// HandleImages returns the list of templates with download/enable status.
func HandleImages(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:read") {
		return
	}

	enabledSet := getEnabledImageSet()
	cleanupOldImageDownloadErrors()
	kvmAvailable := hostKVMAvailable()

	templates := lxc.GetTemplates()
	kvmImages := []kvm.Image{}
	if kvmAvailable {
		kvmImages = kvm.GetImages()
	}
	images := make([]ImageInfo, 0, len(templates)+len(kvmImages))
	for _, t := range templates {
		dl := imageDownloadInfo(t.ID)
		downloaded, size := imageDownloadedInfo(t.Distro, t.Release, t.Arch)
		images = append(images, ImageInfo{
			ID:              t.ID,
			Name:            t.Name,
			Type:            config.VirtualizationLXC,
			Distro:          t.Distro,
			Release:         t.Release,
			Arch:            t.Arch,
			Description:     t.Description,
			Downloaded:      downloaded,
			Enabled:         enabledSet[t.ID],
			Downloading:     dl.Downloading,
			Progress:        dl.Progress,
			DownloadedBytes: dl.DownloadedBytes,
			TotalBytes:      dl.TotalBytes,
			Stage:           dl.Stage,
			Error:           dl.Error,
			SizeBytes:       size,
		})
	}
	for _, t := range kvmImages {
		dl := imageDownloadInfo(t.ID)
		downloaded, size := kvm.ImageDownloadedInfo(t.ID)
		manualPath := ""
		if t.Distro == "windows" {
			manualPath = kvm.ImagePath(t.ID)
		}
		images = append(images, ImageInfo{
			ID:              t.ID,
			Name:            t.Name,
			Type:            config.VirtualizationKVM,
			Distro:          t.Distro,
			Release:         t.Release,
			Arch:            t.Arch,
			Description:     t.Description,
			Downloaded:      downloaded,
			Enabled:         enabledSet[t.ID],
			Downloading:     dl.Downloading,
			Progress:        dl.Progress,
			DownloadedBytes: dl.DownloadedBytes,
			TotalBytes:      dl.TotalBytes,
			Stage:           dl.Stage,
			Error:           dl.Error,
			SizeBytes:       size,
			ManualPath:      manualPath,
			Desktop:         t.Desktop,
		})
	}

	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: images})
}

// HandleImageDownload starts a template image download in the background.
func HandleImageDownload(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:download") {
		return
	}

	var req struct {
		TemplateID string `json:"template_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.TemplateID == "" {
		jsonResponse(w, http.StatusBadRequest, APIResponse{Success: false, Message: "template_id required"})
		return
	}

	tmpl := lxc.FindTemplate(req.TemplateID)
	if tmpl == nil {
		image := kvm.FindImage(req.TemplateID)
		if image == nil {
			jsonResponse(w, http.StatusNotFound, APIResponse{Success: false, Message: "Template not found"})
			return
		}
		if !hostKVMAvailable() {
			jsonResponse(w, http.StatusForbidden, APIResponse{Success: false, Message: "KVM is not available on this host"})
			return
		}
		if ok, _ := kvm.ImageDownloadedInfo(image.ID); ok {
			ensureImageEnabled(image.ID)
			clearImageDownload(image.ID)
			jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "Already downloaded"})
			return
		}
		ctx, ok := startImageDownload(image.ID, "downloading")
		if !ok {
			jsonResponse(w, http.StatusConflict, APIResponse{Success: false, Message: "Already downloading"})
			return
		}
		go func(image kvm.Image) {
			err := kvm.DownloadImageWithProgress(ctx, image, func(p kvm.DownloadProgress) {
				updateImageDownload(image.ID, func(st *imageDownloadStatus) {
					if p.Stage != "" {
						st.Stage = p.Stage
					}
					if p.DownloadedBytes > 0 || p.TotalBytes > 0 {
						st.DownloadedBytes = p.DownloadedBytes
						st.TotalBytes = p.TotalBytes
					}
					st.Progress = p.Percent
				})
			})
			if err != nil {
				if ctx.Err() != nil {
					os.Remove(kvm.ImagePath(image.ID) + ".tmp")
					os.Remove(kvm.ImagePath(image.ID))
					finishImageDownload(image.ID, nil)
					return
				}
				finishImageDownload(image.ID, err)
				return
			}
			ensureImageEnabled(image.ID)
			finishImageDownload(image.ID, nil)
		}(*image)
		jsonResponse(w, http.StatusAccepted, APIResponse{Success: true, Message: "Download started"})
		return
	}

	// Already downloaded? Just enable if needed.
	if isImageDownloaded(tmpl.Distro, tmpl.Release, tmpl.Arch) {
		ensureImageEnabled(tmpl.ID)
		clearImageDownload(tmpl.ID)
		jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "Already downloaded"})
		return
	}

	ctx, ok := startImageDownload(tmpl.ID, "lxc-create")
	if !ok {
		jsonResponse(w, http.StatusConflict, APIResponse{Success: false, Message: "Already downloading"})
		return
	}

	go func(tmpl lxc.Template) {
		// Download via lxc-create with a temp container, then destroy it.
		tmpName := lxcImageDownloadTempName(tmpl.ID)
		args := []string{"-n", tmpName, "-t", "download", "--",
			"-d", tmpl.Distro, "-r", tmpl.Release, "-a", tmpl.Arch}
		if tmpl.Variant != "" {
			args = append(args, "--variant", tmpl.Variant)
		}
		updateImageDownload(tmpl.ID, func(st *imageDownloadStatus) {
			st.Stage = "lxc-create"
		})
		cmd := exec.CommandContext(ctx, "lxc-create", args...)
		output, err := cmd.CombinedOutput()

		// Clean up the temp container unconditionally.
		cleanupLXCImageDownloadTemp(tmpl.ID)

		if err != nil {
			if ctx.Err() != nil {
				finishImageDownload(tmpl.ID, nil)
				return
			}
			err = fmt.Errorf("Download failed: %v, output: %s", err, string(output))
			finishImageDownload(tmpl.ID, err)
			return
		}
		ensureImageEnabled(tmpl.ID)
		finishImageDownload(tmpl.ID, nil)
	}(*tmpl)

	jsonResponse(w, http.StatusAccepted, APIResponse{Success: true, Message: "Download started"})
}

// HandleImageCancel cancels an in-progress image download.
func HandleImageCancel(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:download") {
		return
	}
	var req struct {
		TemplateID string `json:"template_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.TemplateID == "" {
		jsonResponse(w, http.StatusBadRequest, APIResponse{Success: false, Message: "template_id required"})
		return
	}

	imageDownloadsMu.Lock()
	st := imageDownloads[req.TemplateID]
	if st == nil || !st.Downloading || st.Cancel == nil {
		imageDownloadsMu.Unlock()
		jsonResponse(w, http.StatusNotFound, APIResponse{Success: false, Message: "No active download"})
		return
	}
	cancel := st.Cancel
	st.Stage = "canceling"
	st.UpdatedAt = time.Now()
	imageDownloadsMu.Unlock()

	cancel()
	if image := kvm.FindImage(req.TemplateID); image != nil {
		os.Remove(kvm.ImagePath(image.ID) + ".tmp")
		os.Remove(kvm.ImagePath(image.ID))
	}
	if tmpl := lxc.FindTemplate(req.TemplateID); tmpl != nil {
		go cleanupLXCImageDownloadTemp(tmpl.ID)
	}
	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "Cancel requested"})
}

// HandleImageDelete deletes a cached template image from disk.
func HandleImageDelete(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodDelete {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:delete") {
		return
	}

	var req struct {
		TemplateID string `json:"template_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.TemplateID == "" {
		jsonResponse(w, http.StatusBadRequest, APIResponse{Success: false, Message: "template_id required"})
		return
	}
	if isImageDownloadActive(req.TemplateID) {
		jsonResponse(w, http.StatusConflict, APIResponse{Success: false, Message: "Image is downloading; cancel it before deleting"})
		return
	}

	tmpl := lxc.FindTemplate(req.TemplateID)
	if tmpl == nil {
		if image := kvm.FindImage(req.TemplateID); image != nil {
			if err := kvm.DeleteImage(image.ID); err != nil {
				jsonResponse(w, http.StatusInternalServerError, APIResponse{Success: false, Message: "Failed to delete image cache: " + err.Error()})
				return
			}
			removeImageEnabled(image.ID)
			jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "Deleted"})
			return
		}
		jsonResponse(w, http.StatusNotFound, APIResponse{Success: false, Message: "Template not found"})
		return
	}

	// Remove cache directory
	cachePath := filepath.Join("/var/cache/lxc/download", tmpl.Distro, tmpl.Release, tmpl.Arch)
	if err := os.RemoveAll(cachePath); err != nil {
		jsonResponse(w, http.StatusInternalServerError, APIResponse{
			Success: false,
			Message: fmt.Sprintf("Failed to delete image cache: %v", err),
		})
		return
	}

	// Remove from enabled list
	removeImageEnabled(tmpl.ID)

	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "Deleted"})
}

// HandleImageToggle enables or disables a template image.
func HandleImageToggle(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPut {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:toggle") {
		return
	}

	var req struct {
		TemplateID string `json:"template_id"`
		Enabled    bool   `json:"enabled"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.TemplateID == "" {
		jsonResponse(w, http.StatusBadRequest, APIResponse{Success: false, Message: "template_id required"})
		return
	}

	if req.Enabled {
		ensureImageEnabled(req.TemplateID)
	} else {
		removeImageEnabled(req.TemplateID)
	}

	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Message: "OK"})
}

// HandleEnabledImages returns only the enabled AND downloaded templates.
// Used by container create / reinstall to filter available templates.
func HandleEnabledImages(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Success: false, Message: "Method not allowed"})
		return
	}
	if !requireScope(w, r, "image:read") {
		return
	}

	runtime := runtimeFromRequest(r.URL.Query().Get("type"))
	enabledSet := getEnabledImageSet()

	result := make([]map[string]string, 0)
	if runtime == config.VirtualizationKVM {
		if !hostKVMAvailable() {
			jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: result})
			return
		}
		for _, t := range kvm.GetImages() {
			if downloaded, _ := kvm.ImageDownloadedInfo(t.ID); enabledSet[t.ID] && downloaded {
				result = append(result, map[string]string{
					"id": t.ID, "name": t.Name, "distro": t.Distro, "release": t.Release, "arch": t.Arch,
					"description": t.Description, "type": config.VirtualizationKVM, "desktop": t.Desktop,
				})
			}
		}
	} else {
		for _, t := range lxc.GetTemplates() {
			if enabledSet[t.ID] && isImageDownloaded(t.Distro, t.Release, t.Arch) {
				result = append(result, map[string]string{
					"id": t.ID, "name": t.Name, "distro": t.Distro, "release": t.Release, "arch": t.Arch,
					"variant": t.Variant, "description": t.Description, "type": config.VirtualizationLXC,
				})
			}
		}
	}

	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: result})
}

func isTemplateEnabledAndDownloaded(templateID string) bool {
	return isImageEnabledAndDownloaded(templateID, runtimeFromTemplateID(templateID))
}

func isImageEnabledAndDownloaded(templateID string, runtime string) bool {
	runtime = runtimeFromRequest(runtime)
	if runtime == config.VirtualizationKVM {
		if !hostKVMAvailable() {
			return false
		}
		image := kvm.FindImage(templateID)
		if image == nil {
			return false
		}
		enabledSet := getEnabledImageSet()
		downloaded, _ := kvm.ImageDownloadedInfo(image.ID)
		return enabledSet[image.ID] && downloaded
	}
	tmpl := lxc.FindTemplate(templateID)
	if tmpl == nil {
		return false
	}
	enabledSet := getEnabledImageSet()
	return enabledSet[tmpl.ID] && isImageDownloaded(tmpl.Distro, tmpl.Release, tmpl.Arch)
}

func hostKVMAvailable() bool {
	if runtime.GOARCH != "amd64" && runtime.GOARCH != "arm64" {
		return false
	}
	return fileExists("/dev/kvm") && commandExists("virsh") && commandExists(kvmQEMUCheckKey())
}

func ensureImageEnabled(id string) {
	// If the enabled list is empty, all templates are currently enabled by default.
	// We must populate the list with all template IDs first so that explicit toggles stick.
	if len(config.AppConfig.EnabledImages) == 0 {
		for _, t := range lxc.GetTemplates() {
			config.AppConfig.EnabledImages = append(config.AppConfig.EnabledImages, t.ID)
		}
		for _, t := range kvm.GetImages() {
			config.AppConfig.EnabledImages = append(config.AppConfig.EnabledImages, t.ID)
		}
		config.SaveConfig()
		return // Already contains all IDs including this one
	}
	found := false
	for _, eid := range config.AppConfig.EnabledImages {
		if eid == id {
			found = true
			break
		}
	}
	if !found {
		config.AppConfig.EnabledImages = append(config.AppConfig.EnabledImages, id)
		config.SaveConfig()
	}
}

func removeImageEnabled(id string) {
	// If the enabled list is empty, populate it first with all templates,
	// then remove the one being disabled.
	if len(config.AppConfig.EnabledImages) == 0 {
		for _, t := range lxc.GetTemplates() {
			if t.ID != id {
				config.AppConfig.EnabledImages = append(config.AppConfig.EnabledImages, t.ID)
			}
		}
		for _, t := range kvm.GetImages() {
			if t.ID != id {
				config.AppConfig.EnabledImages = append(config.AppConfig.EnabledImages, t.ID)
			}
		}
		config.SaveConfig()
		return
	}
	filtered := make([]string, 0, len(config.AppConfig.EnabledImages))
	for _, eid := range config.AppConfig.EnabledImages {
		if eid != id {
			filtered = append(filtered, eid)
		}
	}
	if len(filtered) != len(config.AppConfig.EnabledImages) {
		config.AppConfig.EnabledImages = filtered
		config.SaveConfig()
	}
}