package lua

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// Package lua — 插件凭据保险库（R4-d）
//
// 用户点明的能力：插件**自己主导外部源的链接认证、自动领取额度**。这类插件
// （对照 dsh-our-free-model 的渠道插件形态）要长期持有 OAuth token、session、
// 设备指纹等凭据，并在定时任务里拿去换额度、换上游。
//
// 在保险库之前，插件唯一的持久化落点是 plugin.state，而它有两个问题：
//
//  1. **权限**：.state.json 是业务累计量（计费总额、签到天数），和凭据混在同一个
//     文件里。它没有 0600，落在插件目录（0755）下 —— 存 token 等于把凭据摊开。
//  2. **语义**：state 会被 PUT /api/plugins/{name}/state 整体替换，会被
//     `prices` 分离逻辑触碰，会进 WebUI。凭据进去就有可能被一次"重置状态"
//     或一次 UI 回显带走。
//
// 保险库把凭据隔离成独立文件：
//
//	<plugin_dir>/.secrets/<plugin>.json   权限 0600，目录 0700
//
// 与状态分离，不参与 UI 回显，不参与 state 替换。
//
// # 谁能读
//
// 只有该插件自己（按启动时的固定名字）。跨插件读会被拒 —— 记名方式是插件名
// 而非任意引用，因为参考插件的 `credentialRef` 模式（任意字符串引用）在这里
// 会变成一个可以指向别人凭据的键空间。
//
// # 与内核动作的关系
//
// 凭据本身不进 Lua 的返回值上限之外的地方：取出后由插件用于自己的 HTTP 调用。
// 保险库不把凭据交给内核，内核也不需要读它。

// secretsDirName is the vault directory inside plugin_dir. The leading dot keeps
// it out of a casual `ls` of the plugin directory, which is where operators look
// for "what plugins do I have" — the vault is not a plugin.
const secretsDirName = ".secrets"

// secretsDir returns the vault directory (empty when there is no plugin dir, in
// which case the vault is disabled — same posture as state persistence).
func (ps *Plugins) secretsDir() string {
	if ps.dir == "" {
		return ""
	}
	return filepath.Join(ps.dir, secretsDirName)
}

// secretFile returns one plugin's vault path.
func (ps *Plugins) secretFile(plugin string) string {
	d := ps.secretsDir()
	if d == "" {
		return ""
	}
	return filepath.Join(d, plugin+".json")
}

// validateSecretKey rejects keys that could not round-trip through the vault.
//
// The vault is a flat string->string map serialized as JSON, so a key only needs
// to be non-empty and not absurdly long. Traversal is not a concern because keys
// are never used as path components; the FILE name comes from the plugin name,
// which is already validated when the plugin loads.
func validateSecretKey(key string) error {
	if strings.TrimSpace(key) == "" {
		return fmt.Errorf("secret key must not be empty")
	}
	if len(key) > 200 {
		return fmt.Errorf("secret key too long (%d chars, max 200)", len(key))
	}
	return nil
}

// loadSecretsLocked reads one plugin's vault. Caller holds ps.mu.
//
// A missing file means "nothing stored yet" — the normal first-run state. A
// corrupt file returns an error rather than an empty map: silently treating
// unreadable credentials as absent would make a plugin re-login and overwrite
// whatever the file still held, which is how a recoverable parse problem becomes
// a lost session.
func (ps *Plugins) loadSecretsLocked(plugin string) (map[string]string, error) {
	path := ps.secretFile(plugin)
	if path == "" {
		return map[string]string{}, nil
	}
	b, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return map[string]string{}, nil
	}
	if err != nil {
		return nil, err
	}
	m := map[string]string{}
	if len(b) == 0 {
		return m, nil
	}
	if err := json.Unmarshal(b, &m); err != nil {
		return nil, fmt.Errorf("vault for plugin %s is unreadable: %w", plugin, err)
	}
	return m, nil
}

// writeSecretsLocked persists one plugin's vault with 0600.
//
// The mode is set on the temp file BEFORE the rename, so the secret is never
// visible under a looser mode at any instant — a chmod-after-write would leave a
// window where the token sits in a world-readable file.
func (ps *Plugins) writeSecretsLocked(plugin string, m map[string]string) error {
	path := ps.secretFile(plugin)
	if path == "" {
		return fmt.Errorf("no plugin directory configured; the credential vault is disabled")
	}
	dir := ps.secretsDir()
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return err
	}
	// Tighten an existing directory too: MkdirAll is a no-op when it exists, so a
	// vault created before this mode was enforced would keep its old permissions.
	_ = os.Chmod(dir, 0o700)

	b, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return err
	}
	tmp, err := os.CreateTemp(dir, plugin+".*.tmp")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	cleanup := func() { _ = os.Remove(tmpName) }
	if err := tmp.Chmod(0o600); err != nil {
		tmp.Close()
		cleanup()
		return err
	}
	if _, err := tmp.Write(b); err != nil {
		tmp.Close()
		cleanup()
		return err
	}
	if err := tmp.Close(); err != nil {
		cleanup()
		return err
	}
	if err := os.Rename(tmpName, path); err != nil {
		cleanup()
		return err
	}
	return nil
}

// ---- 导出给 Lua 的 API ----

// SetSecret stores one credential for a plugin.
func (ps *Plugins) SetSecret(plugin, key, value string) error {
	if plugin == "" {
		return fmt.Errorf("plugin name required")
	}
	if err := validateSecretKey(key); err != nil {
		return err
	}
	ps.mu.Lock()
	defer ps.mu.Unlock()
	m, err := ps.loadSecretsLocked(plugin)
	if err != nil {
		return err
	}
	m[key] = value
	return ps.writeSecretsLocked(plugin, m)
}

// GetSecret reads one credential. The second return reports whether it existed,
// which lets a plugin distinguish "no token stored yet" from "token is empty"
// without a sentinel value.
func (ps *Plugins) GetSecret(plugin, key string) (string, bool, error) {
	if plugin == "" {
		return "", false, fmt.Errorf("plugin name required")
	}
	if err := validateSecretKey(key); err != nil {
		return "", false, err
	}
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	m, err := ps.loadSecretsLocked(plugin)
	if err != nil {
		return "", false, err
	}
	v, ok := m[key]
	return v, ok, nil
}

// DeleteSecret removes one credential. Removing a missing key is not an error —
// "make sure nothing is stored under this key" is the useful postcondition.
func (ps *Plugins) DeleteSecret(plugin, key string) error {
	if plugin == "" {
		return fmt.Errorf("plugin name required")
	}
	if err := validateSecretKey(key); err != nil {
		return err
	}
	ps.mu.Lock()
	defer ps.mu.Unlock()
	m, err := ps.loadSecretsLocked(plugin)
	if err != nil {
		return err
	}
	delete(m, key)
	return ps.writeSecretsLocked(plugin, m)
}

// SecretKeys lists the KEY NAMES a plugin has stored (never the values), so a
// plugin can show "which accounts are configured" without exposing token bytes.
func (ps *Plugins) SecretKeys(plugin string) ([]string, error) {
	if plugin == "" {
		return nil, fmt.Errorf("plugin name required")
	}
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	m, err := ps.loadSecretsLocked(plugin)
	if err != nil {
		return nil, err
	}
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out, nil
}

// DeleteAllSecrets wipes a plugin's vault. Used on plugin removal so uninstalling
// a plugin does not leave live credentials behind.
func (ps *Plugins) DeleteAllSecrets(plugin string) {
	ps.mu.Lock()
	defer ps.mu.Unlock()
	if path := ps.secretFile(plugin); path != "" {
		_ = os.Remove(path)
	}
}

// PurgeOrphanVaults removes vault files whose plugin no longer exists.
//
// Vaults outlive the plugin file only if a removal path forgot to clean up, so
// this is a startup sweep rather than a hot path. Its value is that a deleted
// plugin cannot leave a live OAuth token on disk indefinitely.
func (ps *Plugins) PurgeOrphanVaults() {
	dir := ps.secretsDir()
	if dir == "" {
		return
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		return
	}
	ps.mu.RLock()
	live := make(map[string]bool, len(ps.plugins))
	for _, p := range ps.plugins {
		live[p.Info.Name] = true
	}
	ps.mu.RUnlock()
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
			continue
		}
		name := strings.TrimSuffix(e.Name(), ".json")
		if live[name] {
			continue
		}
		_ = os.Remove(filepath.Join(dir, e.Name()))
	}
}