package service

import (
	"archive/tar"
	"bufio"
	"bytes"
	"compress/gzip"
	"crypto/rand"
	"embed"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"syscall"
	"unicode/utf8"

	"github.com/mhsanaei/3x-ui/v3/internal/web/service/probe"
)

// Item 7 B5: the theme store (hub frontend.rs + api.rs theme
// management port). Themes stay static directory packages on disk —
// <db folder>/themes/<short>/ — installed from an uploaded or fetched
// theme.tar.gz only after full validation, published by a single
// rename so the public page is never served from a partial directory.
// The monitor-theme-default release package is embedded in the binary
// as the fallback theme (MIT, see probe_theme_default/LICENSE), so
// the public page answers even with nothing installed.
//
// A refusal the OPERATOR can act on (bad package, bad address, quota)
// is a *ProbeThemeRefusal carrying the hub's own wording; anything
// else is a machine fault and surfaces as a plain error.

// ProbeTheme is one theme manifest as the panel lists it (hub Theme).
type ProbeTheme struct {
	Name        string          `json:"name"`
	Short       string          `json:"short"`
	Description string          `json:"description"`
	Version     string          `json:"version"`
	Author      string          `json:"author"`
	URL         string          `json:"url"`
	Config      json.RawMessage `json:"config,omitempty"`
	Selected    bool            `json:"selected"`
	Builtin     bool            `json:"builtin"`
	Preview     bool            `json:"preview"`
}

// ProbeThemeRefusal is an operator-facing refusal (hub Shown).
type ProbeThemeRefusal struct{ Msg string }

func (e *ProbeThemeRefusal) Error() string { return e.Msg }

func themeRefuse(format string, args ...any) *ProbeThemeRefusal {
	return &ProbeThemeRefusal{Msg: fmt.Sprintf(format, args...)}
}

// IsThemeRefusal reports whether err is an operator-facing refusal.
func IsThemeRefusal(err error) bool {
	var r *ProbeThemeRefusal
	return errors.As(err, &r)
}

// ---- limits (hub frontend.rs / api.rs, verbatim) ----

const (
	maxThemeEntries  = 2000
	maxThemeFile     = 8 << 20
	maxThemeExpanded = 64 << 20
	maxThemePadding  = 1 << 20
	// Every byte the gzip stream may expand to, headers included.
	maxThemeStream = maxThemeExpanded + maxThemePadding + (8 << 20)
	// Upload/download ceiling for one theme.tar.gz.
	MaxThemeArchive = 32 * 1024 * 1024
)

// Archive failure wordings (hub frontend.rs).
const (
	themeDamaged = "主题包损坏或不完整（可能没下载完），重新下载 theme.tar.gz 再试"
	themeTangled = "主题包里有同名的文件和目录，或者文件名过长，包本身有问题，请联系主题作者"
	themeNotGzip = "选的不是主题包：到主题仓库的 Releases 下载 theme.tar.gz，不要选 Source code"
)

var themeGzipMagic = []byte{0x1f, 0x8b}

// ---- the embedded fallback theme ----

//go:embed all:probe_theme_default
var probeDefaultThemeFS embed.FS

const probeDefaultThemeDir = "probe_theme_default"

// probeBuiltinManifest parses the embedded default theme's manifest.
// It is vendored from the official release package, so a parse
// failure is a build defect, not a runtime condition.
func probeBuiltinManifest() ProbeTheme {
	data, err := probeDefaultThemeFS.ReadFile(probeDefaultThemeDir + "/theme.json")
	if err != nil {
		return ProbeTheme{Name: "默认主题", Short: "default", Builtin: true, Preview: true}
	}
	theme, perr := parseProbeManifest(data)
	if perr != nil {
		return ProbeTheme{Name: "默认主题", Short: "default", Builtin: true, Preview: true}
	}
	theme.Builtin = true
	theme.Preview = true
	return theme
}

// probeEmbeddedFile reads one file of the embedded theme's dist.
func probeEmbeddedFile(relative string) ([]byte, bool) {
	clean := path.Clean(relative)
	if clean == "." || strings.HasPrefix(clean, "../") || path.IsAbs(clean) {
		return nil, false
	}
	data, err := probeDefaultThemeFS.ReadFile(probeDefaultThemeDir + "/dist/" + clean)
	if err != nil {
		return nil, false
	}
	return data, true
}

// parseProbeManifest decodes a theme.json (hub manifest parse): the
// six string fields must be present; config passes through unparsed.
func parseProbeManifest(data []byte) (ProbeTheme, error) {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return ProbeTheme{}, err
	}
	var theme ProbeTheme
	for _, key := range []string{"name", "short", "description", "version", "author", "url"} {
		v, ok := raw[key]
		if !ok {
			return ProbeTheme{}, fmt.Errorf("theme.json missing %s", key)
		}
		var s string
		if err := json.Unmarshal(v, &s); err != nil {
			return ProbeTheme{}, fmt.Errorf("theme.json %s is not a string", key)
		}
		switch key {
		case "name":
			theme.Name = s
		case "short":
			theme.Short = s
		case "description":
			theme.Description = s
		case "version":
			theme.Version = s
		case "author":
			theme.Author = s
		case "url":
			theme.URL = s
		}
	}
	if cfg, ok := raw["config"]; ok {
		theme.Config = cfg
	}
	return theme, nil
}

// probeDiskManifest reads the manifest of an installed theme dir
// (hub manifest): valid only when the manifest's short matches the
// directory name; oversized or unparsable manifests exclude the theme.
func probeDiskManifest(root, short string) (ProbeTheme, bool) {
	data, ok := readInsideTheme(root, "theme.json")
	if !ok || len(data) > 64*1024 {
		return ProbeTheme{}, false
	}
	theme, err := parseProbeManifest(data)
	if err != nil || theme.Short != short {
		return ProbeTheme{}, false
	}
	return theme, true
}

// ProbeThemes lists the embedded fallback first, then every installed
// theme (hub themes()): an installed copy of the built-in theme
// replaces it in the list, the rest sort by name, and the selected
// flag follows the theme setting with a fallback to "default".
func ProbeThemes() ([]ProbeTheme, error) {
	list := []ProbeTheme{probeBuiltinManifest()}

	root := ProbeThemesRoot()
	if base, err := filepath.EvalSymlinks(root); err == nil {
		entries, err := os.ReadDir(base)
		if err != nil {
			return nil, err
		}
		for _, entry := range entries {
			if !entry.IsDir() {
				continue
			}
			short := entry.Name()
			if !ValidThemeShort(short) {
				continue
			}
			if _, ok := probeExternalTheme(short); !ok {
				continue
			}
			dir, err := filepath.EvalSymlinks(filepath.Join(base, short))
			if err != nil || !strings.HasPrefix(dir, base+string(os.PathSeparator)) {
				continue
			}
			theme, ok := probeDiskManifest(dir, short)
			if !ok {
				continue
			}
			theme.Preview = ProbeThemePreview(short) != nil
			if theme.Short == "default" {
				list[0] = theme
			} else {
				list = append(list, theme)
			}
		}
	}

	configured := ProbeCurrentTheme()
	selected := "default"
	for _, theme := range list {
		if theme.Short == configured {
			selected = configured
			break
		}
	}
	for i := range list {
		list[i].Selected = list[i].Short == selected
	}
	rest := list[1:]
	sort.SliceStable(rest, func(i, j int) bool { return rest[i].Name < rest[j].Name })
	return list, nil
}

// ProbeThemeSelectable mirrors hub selectable: the empty string and
// "default" always are (switching back is the recovery from a broken
// external theme); anything else must be installed.
func ProbeThemeSelectable(short string) bool {
	if short == "" || short == "default" {
		return true
	}
	list, err := ProbeThemes()
	if err != nil {
		return false
	}
	for _, theme := range list {
		if theme.Short == short {
			return true
		}
	}
	return false
}

// SetProbeCurrentTheme switches the public page to a theme, effective
// on the next request (the setting is read per request).
func SetProbeCurrentTheme(short string) error {
	if !ProbeThemeSelectable(short) {
		return themeRefuse("没有这个主题")
	}
	return setProbeSetting("theme", short)
}

// ProbeThemePreview returns a theme's preview.png where it has one
// (hub preview): the installed copy's own file, and for the built-in
// theme the embedded one when no disk copy provides it.
func ProbeThemePreview(short string) []byte {
	if !ValidThemeShort(short) {
		return nil
	}
	root := filepath.Join(ProbeThemesRoot(), short)
	if info, err := os.Stat(filepath.Join(root, "preview.png")); err == nil && info.Size() <= maxThemeFile {
		if data, ok := readInsideTheme(root, "preview.png"); ok {
			return data
		}
	}
	if short == "default" {
		if data, err := probeDefaultThemeFS.ReadFile(probeDefaultThemeDir + "/preview.png"); err == nil {
			return data
		}
	}
	return nil
}

// ---- installing (hub frontend.rs install/unpack/publish) ----

func themeRandomSuffix() string {
	var b [8]byte
	if _, err := rand.Read(b[:]); err != nil {
		return "0000000000000000"
	}
	return hex.EncodeToString(b[:])
}

var errThemeStreamOver = errors.New("theme stream over budget")

// streamCounter caps the decompressed stream: a gzip header may
// declare hundreds of MiB the tar reader would hold in memory before
// any entry is seen, so the budget applies to the stream itself.
type streamCounter struct {
	r    io.Reader
	left int64
	over bool
}

func (s *streamCounter) Read(p []byte) (int, error) {
	if s.left <= 0 {
		s.over = true
		return 0, errThemeStreamOver
	}
	if int64(len(p)) > s.left {
		p = p[:s.left]
	}
	n, err := s.r.Read(p)
	s.left -= int64(n)
	return n, err
}

// archiveReadError maps a stream read failure the way hub's
// archive_error does: a cut or corrupt stream is the archive's fault,
// structural write failures are the package's shape, the rest is the
// machine's.
func archiveReadError(err error) error {
	if errors.Is(err, io.ErrUnexpectedEOF) || errors.Is(err, io.ErrClosedPipe) ||
		errors.Is(err, gzip.ErrChecksum) || errors.Is(err, gzip.ErrHeader) ||
		errors.Is(err, tar.ErrHeader) || errors.Is(err, tar.ErrWriteTooLong) {
		return themeRefuse("%s", themeDamaged)
	}
	return err
}

func archiveWriteError(err error) error {
	if errors.Is(err, os.ErrExist) || errors.Is(err, syscall.ENOTDIR) || errors.Is(err, syscall.EISDIR) {
		return themeRefuse("%s", themeTangled)
	}
	return err
}

// unpackProbeTheme expands the archive into into (which it creates),
// enforcing every hub limit. Nothing is published by this step.
func unpackProbeTheme(archive io.Reader, into string) error {
	br := bufio.NewReader(archive)
	magic, err := br.Peek(2)
	if err != nil || !bytes.Equal(magic, themeGzipMagic) {
		return themeRefuse("%s", themeNotGzip)
	}
	if err := os.Mkdir(into, 0o755); err != nil {
		return err
	}
	gz, err := gzip.NewReader(br)
	if err != nil {
		return themeRefuse("%s", themeDamaged)
	}
	stream := &streamCounter{r: gz, left: maxThemeStream}
	tr := tar.NewReader(stream)

	entriesErr := unpackProbeEntries(tr, into)
	// Read to the end of the gzip stream, where its checksum lives:
	// the entries stop at tar's end marker, short of it, so otherwise
	// an archive altered in transit installs as long as its headers
	// survived. What follows the marker is record padding, drained
	// through the same stream budget and bounded in its own right.
	tail, tailErr := io.Copy(io.Discard, stream)
	if stream.over {
		return themeRefuse("主题包解压后超过 %d MiB", maxThemeExpanded>>20)
	}
	if entriesErr != nil {
		return entriesErr
	}
	if tailErr != nil {
		return archiveReadError(tailErr)
	}
	if tail > maxThemePadding {
		return themeRefuse("主题包在 tar 结尾之后还有超过 1 MiB 的数据，包本身有问题，请联系主题作者")
	}
	return nil
}

func unpackProbeEntries(tr *tar.Reader, into string) error {
	var expanded int64
	for seen := 0; ; seen++ {
		hdr, err := tr.Next()
		if err == io.EOF {
			return nil
		}
		if err != nil {
			if errors.Is(err, errThemeStreamOver) {
				return err
			}
			return archiveReadError(err)
		}
		if seen >= maxThemeEntries {
			return themeRefuse("主题包里的条目超过 %d 个", maxThemeEntries)
		}
		// Only the entry types a theme consists of (plus pax global
		// metadata, which writes nothing). A symlink, hard link or
		// device node is a route to writing where the path check
		// cannot see.
		metadata := hdr.Typeflag == tar.TypeXGlobalHeader
		switch {
		case hdr.Typeflag == tar.TypeReg || hdr.Typeflag == tar.TypeRegA || hdr.Typeflag == tar.TypeDir:
		case metadata:
		default:
			return themeRefuse("主题包里有不支持的条目：%s", hdr.Name)
		}
		if hdr.Size > maxThemeFile {
			return themeRefuse("%s 超过单个文件 %d MiB 的上限", hdr.Name, maxThemeFile>>20)
		}
		if expanded > maxThemeExpanded-hdr.Size {
			return themeRefuse("主题包解压后超过 %d MiB", maxThemeExpanded>>20)
		}
		expanded += hdr.Size
		if metadata {
			continue
		}

		// The entry must land inside the staging directory: absolute
		// paths and ".." escapes are refused outright (symlinks are
		// already refused above, so no parent can redirect the join).
		clean := path.Clean(hdr.Name)
		if clean == "." && hdr.Typeflag == tar.TypeDir {
			// The package root itself: guboysky's LuminaPlus ships a
			// leading "." directory entry (all other names carry the
			// "./" prefix too, which Clean strips). Nothing to create —
			// the staging directory already is the root.
			continue
		}
		if clean == "." || clean == ".." || strings.HasPrefix(clean, "../") || path.IsAbs(hdr.Name) {
			return themeRefuse("主题包里的路径越出了主题目录")
		}
		target := filepath.Join(into, filepath.FromSlash(clean))
		if !strings.HasPrefix(target, into+string(os.PathSeparator)) {
			return themeRefuse("主题包里的路径越出了主题目录")
		}
		if hdr.Typeflag == tar.TypeDir {
			if err := os.MkdirAll(target, 0o755); err != nil {
				return archiveWriteError(err)
			}
			continue
		}
		if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
			return archiveWriteError(err)
		}
		if info, err := os.Lstat(target); err == nil && info.IsDir() {
			return themeRefuse("%s", themeTangled)
		}
		f, err := os.OpenFile(target, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
		if err != nil {
			return archiveWriteError(err)
		}
		_, copyErr := io.Copy(f, tr)
		closeErr := f.Close()
		if copyErr != nil {
			if errors.Is(copyErr, errThemeStreamOver) {
				return copyErr
			}
			return archiveReadError(copyErr)
		}
		if closeErr != nil {
			return archiveWriteError(closeErr)
		}
	}
}

// publishProbeTheme checks the unpacked staging directory is a theme
// this panel can serve, then moves it into place under the name its
// manifest asks for (hub publish): a theme being replaced is renamed
// aside and restored if the publish cannot complete.
func publishProbeTheme(themesRoot, staging, expect string) (ProbeTheme, error) {
	manifest, ok := readInsideTheme(staging, "theme.json")
	if !ok {
		return ProbeTheme{}, themeRefuse("主题包里没有 theme.json，下载的若是 Source code，换成 Releases 里的 theme.tar.gz")
	}
	if len(manifest) > 64*1024 {
		return ProbeTheme{}, themeRefuse("theme.json 过大")
	}
	theme, err := parseProbeManifest(manifest)
	if err != nil {
		return ProbeTheme{}, themeRefuse("theme.json 格式不对")
	}
	if !ValidThemeShort(theme.Short) {
		return ProbeTheme{}, themeRefuse("theme.json 里的 short 不能作为目录名：%q", theme.Short)
	}
	if expect != "" && expect != theme.Short {
		return ProbeTheme{}, themeRefuse("这个包里是主题 %q，不是 %q", theme.Short, expect)
	}
	if info, err := os.Stat(filepath.Join(staging, "dist", "index.html")); err != nil || info.IsDir() {
		return ProbeTheme{}, themeRefuse("主题包里没有 dist/index.html")
	}

	destination := filepath.Join(themesRoot, theme.Short)
	replaced := filepath.Join(themesRoot, ".replaced-"+themeRandomSuffix())
	_, statErr := os.Stat(destination)
	replacing := statErr == nil
	if replacing {
		if err := os.Rename(destination, replaced); err != nil {
			return ProbeTheme{}, err
		}
	}
	if err := os.Rename(staging, destination); err != nil {
		if replacing {
			_ = os.Rename(replaced, destination)
		}
		return ProbeTheme{}, err
	}
	if replacing {
		_ = os.RemoveAll(replaced)
	}
	theme.Preview = ProbeThemePreview(theme.Short) != nil
	return theme, nil
}

// InstallProbeTheme installs a theme from its theme.tar.gz under the
// name its manifest carries. expect, when non-empty, names the short
// the caller is replacing: an update may not install a different one.
func InstallProbeTheme(archive io.Reader, expect string) (ProbeTheme, error) {
	root := ProbeThemesRoot()
	if err := os.MkdirAll(root, 0o755); err != nil {
		return ProbeTheme{}, err
	}
	staging := filepath.Join(root, ".staging-"+themeRandomSuffix())
	theme, err := func() (ProbeTheme, error) {
		if err := unpackProbeTheme(archive, staging); err != nil {
			return ProbeTheme{}, err
		}
		return publishProbeTheme(root, staging, expect)
	}()
	if err != nil {
		_ = os.RemoveAll(staging)
		return ProbeTheme{}, err
	}
	return theme, nil
}

// RemoveProbeTheme deletes an installed theme (hub remove), including
// an installed copy of the built-in one — the embedded copy then
// serves in its place. Deleting the theme in use is permitted: the
// public page falls back from the next request.
func RemoveProbeTheme(short string) error {
	if !ValidThemeShort(short) {
		return themeRefuse("没有这个主题")
	}
	base, err := filepath.EvalSymlinks(ProbeThemesRoot())
	if err != nil {
		return themeRefuse("没有这个主题")
	}
	root, err := filepath.EvalSymlinks(filepath.Join(base, short))
	if err != nil || !strings.HasPrefix(root, base+string(os.PathSeparator)) {
		return themeRefuse("没有这个主题")
	}
	if info, err := os.Stat(root); err != nil || !info.IsDir() {
		return themeRefuse("没有这个主题")
	}
	return os.RemoveAll(root)
}

// ---- chunked upload (hub api.rs receive + upload_theme) ----

const probeUploadName = ".upload.tar.gz"

// ReceiveProbeThemeChunk appends one piece of an upload to the
// scratch archive, returning its length afterwards. The state of an
// upload is the length of the file on disk: a piece continues only
// where the last ended, and offset 0 truncates whatever an
// interrupted attempt left behind.
func ReceiveProbeThemeChunk(offset, total int64, body io.Reader) (int64, error) {
	if total <= 0 || total > MaxThemeArchive {
		return 0, themeRefuse("文件必须在 1 字节到 %d MiB 之间", MaxThemeArchive/1024/1024)
	}
	if offset > total {
		return 0, themeRefuse("分片位置越过了文件末尾")
	}
	root := ProbeThemesRoot()
	if err := os.MkdirAll(root, 0o755); err != nil {
		return 0, err
	}
	uploadPath := filepath.Join(root, probeUploadName)
	var f *os.File
	var err error
	if offset == 0 {
		f, err = os.OpenFile(uploadPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
	} else {
		f, err = os.OpenFile(uploadPath, os.O_WRONLY|os.O_APPEND, 0o600)
		if errors.Is(err, os.ErrNotExist) {
			return 0, themeRefuse("这次上传已经不在了，请从头开始")
		}
	}
	if err != nil {
		return 0, err
	}
	defer f.Close()
	info, err := f.Stat()
	if err != nil {
		return 0, err
	}
	if info.Size() != offset {
		return 0, themeRefuse("分片接不上：已经收到 %d 字节，这一片却从 %d 开始", info.Size(), offset)
	}
	written, copyErr := io.Copy(f, io.LimitReader(body, total-offset+1))
	if copyErr != nil || written > total-offset {
		// Undo a partially written piece so a retry aligns again.
		_ = f.Truncate(offset)
		if copyErr != nil {
			return 0, copyErr
		}
		return 0, themeRefuse("这一片超出了声明的文件大小")
	}
	return offset + written, nil
}

// FinishProbeThemeUpload installs the completed scratch archive. The
// file is first moved off the shared upload name, so a second upload
// landing on it cannot change the bytes being unpacked.
func FinishProbeThemeUpload() (ProbeTheme, error) {
	root := ProbeThemesRoot()
	uploadPath := filepath.Join(root, probeUploadName)
	source := filepath.Join(root, ".installing-"+themeRandomSuffix()+".tar.gz")
	if err := os.Rename(uploadPath, source); err != nil {
		_ = os.Remove(uploadPath)
		return ProbeTheme{}, err
	}
	defer os.Remove(source)
	f, err := os.Open(source)
	if err != nil {
		return ProbeTheme{}, err
	}
	defer f.Close()
	return InstallProbeTheme(f, "")
}

// ---- site icons (hub frontend.rs site_icon / ICON_PATHS) ----

// probeIconPaths names each icon the public surface answers and the
// setting that replaces it. With a site icon set, all of them answer
// with it, so the icon follows the site across theme switches.
var probeIconPaths = []struct{ Path, Key string }{
	{"favicon.svg", "favicon"},
	{"favicon.ico", "favicon"},
	{"admin/favicon.svg", "favicon"},
	{"apple-touch-icon.png", "touch_icon"},
	{"apple-touch-icon-precomposed.png", "touch_icon"},
	{"admin/apple-touch-icon.png", "touch_icon"},
}

// ProbeIconSettingKey returns the setting behind an icon path.
func ProbeIconSettingKey(path string) (string, bool) {
	for _, icon := range probeIconPaths {
		if icon.Path == path {
			return icon.Key, true
		}
	}
	return "", false
}

const maxSiteIcon = 20 * 1024

const siteIconNotImage = "站点图标只支持 PNG、ICO、SVG、WebP、JPEG、GIF"

// ProbeSiteIcon decodes a favicon/touch_icon setting — a
// data:image/...;base64, URL — into the bytes and the type they
// actually are. The declared type is not trusted: the response's type
// comes from the bytes.
func ProbeSiteIcon(value string) (mime string, data []byte, err error) {
	rest, ok := strings.CutPrefix(value, "data:image/")
	if !ok {
		return "", nil, themeRefuse("%s", siteIconNotImage)
	}
	_, payload, ok := strings.Cut(rest, ";base64,")
	if !ok {
		return "", nil, themeRefuse("%s", siteIconNotImage)
	}
	data, derr := base64.StdEncoding.DecodeString(payload)
	if derr != nil {
		return "", nil, themeRefuse("%s", siteIconNotImage)
	}
	if len(data) > maxSiteIcon {
		return "", nil, themeRefuse("站点图标不能超过 20 KiB")
	}
	switch {
	case len(data) >= 4 && data[0] == 0x89 && data[1] == 'P' && data[2] == 'N' && data[3] == 'G':
		mime = "image/png"
	case len(data) >= 4 && data[0] == 0 && data[1] == 0 && data[2] == 1 && data[3] == 0:
		mime = "image/x-icon"
	case len(data) >= 3 && data[0] == 0xff && data[1] == 0xd8 && data[2] == 0xff:
		mime = "image/jpeg"
	case len(data) >= 4 && string(data[:4]) == "GIF8":
		mime = "image/gif"
	case len(data) >= 12 && string(data[:4]) == "RIFF" && string(data[8:12]) == "WEBP":
		mime = "image/webp"
	case utf8.Valid(data) && strings.Contains(string(data), "<svg"):
		mime = "image/svg+xml"
	default:
		return "", nil, themeRefuse("%s", siteIconNotImage)
	}
	return mime, data, nil
}

// ProbeIconSetting reads one site-icon setting ("" when unset).
func ProbeIconSetting(key string) string {
	v, _ := probeSetting(key)
	return v
}

// SetProbeIconSetting stores one site-icon setting, validating the
// data URL the way the hub does (empty clears). The bytes are what
// the root icon paths will serve from the next request.
func SetProbeIconSetting(key, value string) error {
	if key != "favicon" && key != "touch_icon" {
		return themeRefuse("没有这个图标设置")
	}
	if value != "" {
		if _, _, err := ProbeSiteIcon(value); err != nil {
			return err
		}
	}
	return setProbeSetting(key, value)
}

// ProbePublicSettings is the public-surface settings block the probe
// settings page edits (settings KV keys, hub names). RetentionDays
// and FastIntervalSec joined in V2.0.1: the retention window already
// existed as the retention_days key (read by the probe store's
// housekeeping), it only lacked an editing surface; the fast-report
// interval drives the agents' lightweight metrics cadence.
type ProbePublicSettings struct {
	PublicPage      bool   `json:"publicPage"`
	SiteName        string `json:"siteName"`
	Site            string `json:"site"`
	GitHubProxy     string `json:"githubProxy"`
	RetentionDays   int64  `json:"retentionDays"`
	FastIntervalSec int    `json:"fastIntervalSec"`
}

// GetProbePublicSettings reads the settings block.
func GetProbePublicSettings() ProbePublicSettings {
	proxy, _ := probeSetting("github_proxy")
	return ProbePublicSettings{
		PublicPage:      ProbePublicPageEnabled(),
		SiteName:        ProbeSiteName(),
		Site:            ProbeSiteURL(),
		GitHubProxy:     proxy,
		RetentionDays:   probe.RetentionDays(),
		FastIntervalSec: ProbeFastIntervalSec(),
	}
}

// SetProbePublicSettings writes the settings block. The GitHub proxy
// is validated as the hub validates it: empty, or an https:// prefix.
func SetProbePublicSettings(s ProbePublicSettings) error {
	if s.GitHubProxy != "" && !strings.HasPrefix(s.GitHubProxy, "https://") {
		return themeRefuse("GitHub 代理要以 https:// 开头，或者留空")
	}
	if s.RetentionDays < 1 || s.RetentionDays > 365 {
		return themeRefuse("历史保留天数要在 1 到 365 之间")
	}
	if s.FastIntervalSec < 1 || s.FastIntervalSec > 60 {
		return themeRefuse("快报间隔要在 1 到 60 秒之间")
	}
	if err := SetProbePublicPageEnabled(s.PublicPage); err != nil {
		return err
	}
	if err := setProbeSetting("site_name", s.SiteName); err != nil {
		return err
	}
	if err := setProbeSetting("site", s.Site); err != nil {
		return err
	}
	if err := setProbeSetting("retention_days", strconv.FormatInt(s.RetentionDays, 10)); err != nil {
		return err
	}
	if err := setProbeSetting("probe_fast_interval", strconv.Itoa(s.FastIntervalSec)); err != nil {
		return err
	}
	return setProbeSetting("github_proxy", s.GitHubProxy)
}

// ProbeGitHubProxy is the configured GitHub proxy prefix ("" = none).
func ProbeGitHubProxy() string {
	v, _ := probeSetting("github_proxy")
	return strings.TrimSpace(v)
}

// probeProxied places the GitHub proxy in front of a github.com URL
// when one is set (hub proxied()).
func probeProxied(url string) string {
	proxy := ProbeGitHubProxy()
	if proxy == "" {
		return url
	}
	return strings.TrimSuffix(proxy, "/") + "/" + url
}