package lua

import (
	"context"
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"
)

// Package lua — 插件可调用的内核动作面（R4-c）
//
// 用户需求（原话）：「现在这个接口不全，可以多给一些接口让 lua 调用内核。」
//
// 在此之前，插件只能通过 __llmsproxy_adapters 管适配器 —— 那是三个手写闭包。
// 内核另有十几个公开动作（重载配置、清冷却、重探上游、增删源/密钥、改 AUTO 链…），
// 插件一个都调不到。而"自愈 / 联动 / 自动孵化"这类插件能力恰恰需要它们：
//
//	探测到上游整片挂掉 → probe_all + reset_health
//	发现额度变化       → save_auto_rules 重排链路
//	拿到新端点         → add_source
//
// # 为什么 Go 侧 deadline 是可行的（而 Lua 死循环不可中断）
//
// 这是整个设计的支点。两者形态完全不同：
//
//	Lua 里 while true do end            → 无法中断（LuaJIT 限制，实测三次）
//	Lua 里 __llmsproxy_kernel.call(...)  → **可以**超时
//
// 因为后者 Lua 只是在等一个返回值，不占用 Lua 栈的执行权。所以每次调用在 Go
// 侧包一层 select + ctx deadline：超时就把 (nil, err) 还给 Lua。这比"Lua 投递
// 请求、Go 队列执行"干净 —— 队列还要定义"超时后积压的命令算什么"，而 deadline
// 的语义是闭合的。
//
// # 权限：全开，但默认不授予
//
// 用户选定「全开」（13 个动作都可达）+ 「设置页可配权限」。全开描述的是**能力
// 存在**，不是**默认授予**：一个插件能删密钥这件事必须由运维在设置页点过确认。
// 因此默认拒绝，授权记录在 .access.json 里（复用现有覆盖机制）。
//
// danger 级动作必须**逐个**授权，不接受通配符 —— 否则运维图省事写个 "*"，
// "删密钥"就和"读状态"同权了。

// KernelAPI 是内核暴露给插件的能力面。由 internal/core 实现并注入。
//
// 依赖方向：internal/lua 不能 import internal/core（方向是 core → lua），
// 所以这里定义接口、core 侧实现 —— 与 SetOutboundHosts 同一个注入先例。
type KernelAPI interface {
	// Actions 列出可调用的动作。设置页据此渲染权限开关，插件据此发现能力。
	Actions() []KernelAction
	// Invoke 执行一个动作。实现**必须**尊重 ctx：ctx 取消后应尽快返回，
	// 否则插件侧的超时虽然会返回错误，但该动作仍在后台跑（变成不可见的泄漏）。
	Invoke(ctx context.Context, name string, args map[string]interface{}) (interface{}, error)
}

// 危险级。它决定权限授予的严格程度，也决定设置页用什么颜色提示。
const (
	// DangerRead 无副作用，只读。仍然需要授权，但可以一次授予全部。
	DangerRead = "read"
	// DangerWrite 修改运行状态或配置，但可恢复（重载、清冷却、改链路）。
	DangerWrite = "write"
	// DangerDestructive 删除类，或让服务中断。**必须逐个授权**。
	DangerDestructive = "destructive"
)

// KernelAction 描述一个可调用动作。
type KernelAction struct {
	// Deferred marks an action that MUST NOT run while the Lua caller holds its
	// plugin lock. The Lua entry points (hook, exported call, scheduled task) all
	// hold p.mu for the whole call, and an action that re-enters the plugin layer
	// (set_plugin_enabled reaches SetEnabled → p.mu.Lock()) would self-deadlock —
	// and with a deadline, would then execute invisibly AFTER the plugin was told
	// it failed.
	//
	// Such an action is queued and run on its own goroutine once the Lua call has
	// returned, so the caller gets "accepted" rather than a lock-up or a lie.
	Deferred bool

	Name        string   `json:"name"`
	Title       string   `json:"title"`
	Description string   `json:"description"`
	Danger      string   `json:"danger"`
	Params      []string `json:"params,omitempty"`
	// TimeoutMS is the Go-side deadline for one invocation. Long actions (a
	// full re-probe walks every source over the network) need a bigger budget
	// than a state read; making it per-action rather than one global number is
	// what keeps the deadline honest rather than arbitrary.
	TimeoutMS int `json:"timeout_ms"`
}

// kernelCatalog is the full action set. It lives in the lua package (rather than
// being discovered from the implementation) so that permissions can be validated
// even when no Core is wired — tests, and a gateway with plugins but no kernel.
//
// Every action here maps to an existing Core method; adding one is a deliberate
// act rather than a reflex. ListKeys/FindKey are deliberately ABSENT: they return
// PLAINTEXT gateway keys, and handing those to third-party Lua would hand over
// the deployment's entire credential surface. Key-related reads go through
// masked forms instead.
var kernelCatalog = []KernelAction{
	// ---- 只读 ----
	{Name: "status", Title: "运行状态", Danger: DangerRead, TimeoutMS: 3000,
		Description: "各源的调度状态（冷却、连续失败、最近错误）"},
	{Name: "list_sources", Title: "源列表", Danger: DangerRead, TimeoutMS: 3000,
		Description: "已配置的上游源（api_key 已掩码）"},
	{Name: "list_models", Title: "模型列表", Danger: DangerRead, TimeoutMS: 3000,
		Description: "当前可路由的模型 id 列表"},
	{Name: "list_adapters", Title: "适配器列表", Danger: DangerRead, TimeoutMS: 3000,
		Description: "已加载的适配器名与版本"},
	{Name: "list_auto_rules", Title: "AUTO 链路", Danger: DangerRead, TimeoutMS: 3000,
		Description: "当前全局 AUTO 链的槽位"},
	{Name: "adapter_owner", Title: "适配器归属", Danger: DangerRead, TimeoutMS: 3000,
		Params:      []string{"name"},
		Description: "某适配器由谁安装（operator 或 plugin:名字）"},

	// ---- 写（可恢复） ----
	{Name: "reload", Title: "重载配置", Danger: DangerWrite, TimeoutMS: 30000,
		Description: "重新读取运行配置并重建源/链路"},
	{Name: "reset_health", Title: "清除冷却", Danger: DangerWrite, TimeoutMS: 5000,
		Description: "清掉所有源的退避状态（修好上游后立即恢复）"},
	{Name: "probe_all", Title: "全量探测", Danger: DangerWrite, TimeoutMS: 60000,
		Description: "对每个源做一次真实可达性探测（走网络，慢）"},
	{Name: "save_auto_rules", Title: "设置 AUTO 链", Danger: DangerWrite, TimeoutMS: 10000,
		Params:      []string{"entries"},
		Description: "替换全局 AUTO 链；entries 为 [{model, source, ...}] 数组"},
	{Name: "save_key_auto", Title: "设置按 key 链路", Danger: DangerWrite, TimeoutMS: 10000,
		Params:      []string{"key_name", "entries"},
		Description: "替换某个网关 key 自己的 AUTO 链"},
	{Name: "add_source", Title: "新增源", Danger: DangerWrite, TimeoutMS: 30000,
		Params:      []string{"source"},
		Description: "把一个新的上游源接入（source 为源定义表）"},
	{Name: "create_key", Title: "新建网关密钥", Danger: DangerWrite, TimeoutMS: 10000,
		Params:      []string{"name", "role", "models"},
		Description: "创建一个网关 key（返回的明文密钥只在此次响应里出现）"},

	// ---- 破坏性：必须逐个授权 ----
	{Name: "remove_source", Title: "删除源", Danger: DangerDestructive, TimeoutMS: 30000,
		Params:      []string{"name"},
		Description: "删除一个上游源"},
	{Name: "delete_key", Title: "删除网关密钥", Danger: DangerDestructive, TimeoutMS: 10000,
		Params:      []string{"key"},
		Description: "删除一个网关 key（正在使用的客户端会立刻 401）"},
	{Name: "update_key", Title: "修改网关密钥", Danger: DangerDestructive, TimeoutMS: 10000,
		Params:      []string{"key", "name", "role", "models"},
		Description: "改动 key 的角色/可见模型（可能扩大访问面）"},
	{Name: "remove_adapter", Title: "删除适配器", Danger: DangerDestructive, TimeoutMS: 30000,
		Params:      []string{"name"},
		Description: "删除适配器（仅限插件自己装的；内置与非自有的会被拒）"},
	{Name: "set_plugin_enabled", Title: "启停插件", Danger: DangerDestructive, TimeoutMS: 5000,
		Params: []string{"name", "enabled"}, Deferred: true,
		Description: "启用或停用某个插件（异步执行：在本次调用返回后生效）"},
}

// kernelActionByName indexes the catalog.
var kernelActionByName = func() map[string]KernelAction {
	m := make(map[string]KernelAction, len(kernelCatalog))
	for _, a := range kernelCatalog {
		m[a.Name] = a
	}
	return m
}()

// KernelActions returns the catalog sorted by name (stable for the UI).
func KernelActions() []KernelAction {
	out := append([]KernelAction(nil), kernelCatalog...)
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

// LookupKernelAction finds an action, reporting whether it exists.
func LookupKernelAction(name string) (KernelAction, bool) {
	a, ok := kernelActionByName[name]
	return a, ok
}

// ---- 权限 ----

// errNotPermitted is returned when a plugin calls an action it was not granted.
// It names the action and the plugin so the operator can act on it directly.
func notPermitted(plugin, action string) error {
	return fmt.Errorf("kernel action %q is not granted to plugin %q; "+
		"enable it in the plugin's kernel permissions", action, plugin)
}

// KernelPermission is the operator's grant for one plugin: the set of action
// names it may call, plus whether it was granted "everything readable".
type KernelPermission struct {
	// Actions is the explicit allowlist, already expanded (no wildcards stored,
	// so a NEW action added in a future release is NOT silently granted to an
	// existing plugin — that is the safe direction for a security default).
	Actions []string
	// AllRead is true when the operator granted every read-only action at once.
	// Stored separately from Actions so that a future read-only action IS covered
	// without re-saving, while writes still require an explicit grant.
	AllRead bool
}

// clone returns a copy so callers cannot mutate the stored permission.
func (p KernelPermission) clone() KernelPermission {
	return KernelPermission{Actions: append([]string(nil), p.Actions...), AllRead: p.AllRead}
}

// allows reports whether the permission covers action.
//
// The "all readable" grant deliberately does NOT cover a future WRITE action:
// expanding a wildcard into whatever happens to exist later is how a convenience
// grant turns into a privilege escalation.
func (p KernelPermission) allows(a KernelAction) bool {
	if p.AllRead && a.Danger == DangerRead {
		return true
	}
	for _, n := range p.Actions {
		if n == a.Name {
			return true
		}
	}
	return false
}

// ---- 调用（带 Go 侧超时） ----

// ErrKernelUnavailable is returned when no KernelAPI was injected (a gateway
// running plugins without a wired core, e.g. some tests).
var ErrKernelUnavailable = errors.New("kernel actions are not available in this build")

// callKernel invokes one action with the permission check and the Go-side
// deadline, returning a value Lua can consume.
//
// The deadline is the whole point: a plugin can block here harmlessly, because
// Lua is waiting on a return value rather than spinning. On timeout the caller
// gets a normal error; the action's own goroutine is told to stop via ctx.
func (ps *Plugins) callKernel(plugin, name string, args map[string]interface{}) (interface{}, error) {
	api := ps.kernel()
	if api == nil {
		return nil, ErrKernelUnavailable
	}
	action, ok := LookupKernelAction(name)
	if !ok {
		return nil, fmt.Errorf("unknown kernel action %q", name)
	}
	if !ps.kernelPermitted(plugin, action) {
		return nil, notPermitted(plugin, name)
	}

	timeout := time.Duration(action.TimeoutMS) * time.Millisecond
	if timeout <= 0 {
		timeout = 10 * time.Second
	}
	// The caller's identity is injected HERE, not taken from args: an action that
	// needs to know who is calling (remove_adapter, to enforce ownership) must not
	// be able to be lied to by the plugin passing someone else's name.
	if args == nil {
		args = map[string]interface{}{}
	}
	args["plugin"] = plugin

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	type result struct {
		v   interface{}
		err error
	}
	// A deferred action must not run under the caller's plugin lock, so it is
	// queued and returns "accepted" immediately. Reporting success here without
	// waiting is honest: the caller is told the action was ACCEPTED, and the
	// actual outcome lands in the plugin's hook_errors surface if it fails.
	if action.Deferred {
		ps.runDeferred(action, args)
		return map[string]interface{}{
			"accepted": true,
			"note":     "this action runs asynchronously; check the plugin state/errors for the outcome",
		}, nil
	}

	// The action runs on its own goroutine so this call can give up on time.
	// Buffered so a late-finishing action never blocks on sending.
	done := make(chan result, 1)
	go func() {
		defer func() {
			// A panicking kernel action must not take the gateway down through a
			// Lua call. Convert it into an error the plugin sees.
			if rec := recover(); rec != nil {
				done <- result{err: fmt.Errorf("kernel action %s panicked: %v", name, rec)}
			}
		}()
		v, err := api.Invoke(ctx, name, args)
		done <- result{v: v, err: err}
	}()

	select {
	case r := <-done:
		return r.v, r.err
	case <-ctx.Done():
		return nil, fmt.Errorf("kernel action %q exceeded its %s budget", name, timeout)
	}
}

// runDeferred executes a lock-re-entrant action outside the Lua call.
//
// It runs on a fresh goroutine precisely so it can take the plugin lock that the
// caller still holds; waiting for the caller to unwind first would need a
// handshake that is more machinery than the one action needs. A failure is
// surfaced through hook_errors, which is where an operator already looks for
// "a plugin's background work stopped working".
func (ps *Plugins) runDeferred(a KernelAction, args map[string]interface{}) {
	api := ps.kernel()
	if api == nil {
		return
	}
	timeout := time.Duration(a.TimeoutMS) * time.Millisecond
	if timeout <= 0 {
		timeout = 10 * time.Second
	}
	// Copy the args: the caller's map is still owned by the Lua call frame.
	cp := make(map[string]interface{}, len(args))
	for k, v := range args {
		cp[k] = v
	}
	go func() {
		defer func() {
			if rec := recover(); rec != nil {
				ps.hookErr.note(StageRequestEnd, fmt.Sprintf("deferred kernel action %s panicked: %v", a.Name, rec))
			}
		}()
		ctx, cancel := context.WithTimeout(context.Background(), timeout)
		defer cancel()
		if _, err := api.Invoke(ctx, a.Name, cp); err != nil {
			ps.hookErr.note(StageRequestEnd, fmt.Sprintf("deferred kernel action %s failed: %v", a.Name, err))
		}
	}()
}

// kernelPermitted applies the stored grant, with one deliberate exception: a
// plugin's OWN adapter may always be removed by that plugin (it is not a kernel
// resource, it is one the plugin created). Everything else needs a grant.
func (ps *Plugins) kernelPermitted(plugin string, a KernelAction) bool {
	if a.Name == "remove_adapter" {
		return true
	}
	ps.mu.RLock()
	perm := ps.kernelPerms[plugin]
	ps.mu.RUnlock()
	return perm.allows(a)
}

// SetPluginKernelPermission replaces one plugin's grant and persists it.
//
// Validation happens here rather than at call time so a typo'd action name is
// reported to the operator immediately instead of silently granting nothing.
func (ps *Plugins) SetPluginKernelPermission(plugin string, actions []string, allRead bool) error {
	if ps.find(plugin) == nil {
		return fmt.Errorf("plugin %s not found", plugin)
	}
	clean := make([]string, 0, len(actions))
	seen := map[string]bool{}
	for _, raw := range actions {
		name := strings.TrimSpace(raw)
		if name == "" || seen[name] {
			continue
		}
		a, ok := LookupKernelAction(name)
		if !ok {
			return fmt.Errorf("unknown kernel action %q", name)
		}
		seen[name] = true
		clean = append(clean, a.Name)
	}
	sort.Strings(clean)
	ps.mu.Lock()
	if ps.kernelPerms == nil {
		ps.kernelPerms = kernelPermissionSet{}
	}
	if len(clean) == 0 && !allRead {
		delete(ps.kernelPerms, plugin)
	} else {
		ps.kernelPerms[plugin] = KernelPermission{Actions: clean, AllRead: allRead}
	}
	ps.saveKernelPermissionsLocked()
	ps.mu.Unlock()
	return nil
}

// PluginKernelPermission returns a copy of one plugin's grant.
func (ps *Plugins) PluginKernelPermission(plugin string) KernelPermission {
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	return ps.kernelPerms[plugin].clone()
}

// KernelPermissionView is the UI-facing form: what the plugin ASKED for (from its
// own source) next to what the operator GRANTED. The distinction matters — a
// plugin declaring `plugin.kernel = {...}` is a request, not a privilege.
type KernelPermissionView struct {
	Plugin   string   `json:"plugin"`
	Declared []string `json:"declared,omitempty"`
	Granted  []string `json:"granted,omitempty"`
	AllRead  bool     `json:"all_read"`
}

// KernelPermissions lists every plugin's declared-vs-granted state for the UI.
func (ps *Plugins) KernelPermissions() []KernelPermissionView {
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	out := make([]KernelPermissionView, 0, len(ps.plugins))
	for _, p := range ps.plugins {
		perm := ps.kernelPerms[p.Info.Name]
		out = append(out, KernelPermissionView{
			Plugin:   p.Info.Name,
			Declared: append([]string(nil), p.KernelDeclared...),
			Granted:  append([]string(nil), perm.Actions...),
			AllRead:  perm.AllRead,
		})
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Plugin < out[j].Plugin })
	return out
}

// kernel returns the injected API, or nil.
func (ps *Plugins) kernel() KernelAPI {
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	return ps.kernelAPI
}

// SetKernelAPI injects the kernel action implementation. Called during wiring,
// mirroring SetOutboundHosts.
func (ps *Plugins) SetKernelAPI(api KernelAPI) {
	ps.mu.Lock()
	defer ps.mu.Unlock()
	ps.kernelAPI = api
}

// kernelPermissionSet is the persisted per-plugin grant map.
type kernelPermissionSet map[string]KernelPermission

// jsonPermission is the on-disk form of one grant. Kept separate from
// KernelPermission so the persisted shape cannot drift with a struct refactor
// (the access file is read by older and newer binaries across an upgrade).
type jsonPermission struct {
	Actions []string `json:"actions,omitempty"`
	AllRead bool     `json:"all_read,omitempty"`
}

func (p KernelPermission) marshal() jsonPermission {
	return jsonPermission{Actions: p.Actions, AllRead: p.AllRead}
}

func (j jsonPermission) unmarshal() KernelPermission {
	return KernelPermission{Actions: j.Actions, AllRead: j.AllRead}
}