// Package lua — 插件长期运行环境（R4-b / Phase 4）
//
// 用户需求：插件需要**长期运行环境（独立 LuaVM 线程化）**，以支持自动签到、
// token 轮换等需要"没有浏览器、没有人操作时也会发生"的能力。
//
// 为什么需要独立 VM：现有插件模型是「一个插件 = 一个 Lua 状态 + 一把锁」，
// 因为钩子会往 plugin.state 累加，多个状态会让总额被劈成几份（见 docs 的
// 运行时约束）。这把锁的代价是**一个卡住的钩子会卡住所有插件**——而签到、
// token 轮换这类任务天然是长耗时的网络等待。
//
// 本文件给出调度层：内核按插件声明的周期，在**独立 VM + 独立 goroutine** 上
// 执行它，从而：
//
//   - 一个插件的长任务不阻塞其它插件的钩子（独立 VM，无共享锁）
//   - 任务在没有浏览器、没有人操作时也会执行（内核 ticker 驱动，不是前端轮询）
//   - 状态与主 VM 分离，轮换中崩溃不会带走已累计的钩子统计
//
// 声明方式（插件侧）：
//
//	PLUGIN.schedule = {
//	    { fn = "refresh_token", every = 3600 },              -- 每小时
//	    { fn = "daily_checkin",  every = 86400, at = "03:30" }, -- 每天固定时刻
//	    { fn = "poll_quota",    every = 300, jitter = 30 },   -- 带抖动，避免整点齐射
//	}
//
// 设计取舍：
//   - **适配器不参与调度**：适配器仍是无状态请求级池（见 R4 的澄清）。token
//     轮换靠插件（这里）按周期调用 Phase 3 的 UpdateAdapter。
//   - 任务在独立 VM 上跑，故**不持有**主 VM 的 plugin.state；任务要写共享
//     状态必须走 state API（SetState / 状态文件），与 docs 的约定一致。
//   - 崩溃隔离：任务函数出错/超时只记 hookErr，不影响钩子与请求转发。
package lua

import (
	"fmt"
	"sort"
	"sync"
	"sync/atomic"
	"time"

	golua "github.com/aarzilli/golua/lua"
)

// ScheduledTask is one declared periodic job.
type ScheduledTask struct {
	// Fn is the plugin function name to invoke.
	Fn string
	// Every is the interval in seconds. 0 disables the task.
	Every int `json:"every"`
	// At is an optional daily local time "HH:MM"; when set, Every is ignored
	// and the task fires once per day at that wall-clock time.
	At string `json:"at,omitempty"`
	// Jitter, in seconds, spreads the first fire randomly so many plugins (or
	// many replicas) do not all hit the same upstream at :00.
	Jitter int `json:"jitter,omitempty"`
}

// scheduleSpec is the parsed `PLUGIN.schedule` table.
type scheduleSpec struct {
	tasks []ScheduledTask
}

// parseSchedule extracts the schedule from a loaded plugin table. It is read
// from the already-compiled state's global, not by re-running the script, so a
// plugin's schedule is available the moment it loads.
func parseSchedule(L *golua.State) scheduleSpec {
	var spec scheduleSpec
	if L == nil {
		return spec
	}
	L.GetGlobal(pluginGlobal)
	if L.IsNil(-1) {
		L.Pop(1)
		return spec
	}
	if !getFieldBatch(L, "schedule") {
		L.Pop(1)
		return spec
	}
	// schedule is an array of tables
	if L.Type(-1) != golua.LUA_TTABLE {
		L.Pop(2)
		return spec
	}
	arr := L.GetTop()
	idx := 1
	for {
		// golua exposes indexed table access through RawGeti; GetField only
		// takes a string key.
		L.RawGeti(arr, idx)
		if L.IsNil(-1) {
			L.Pop(1)
			break
		}
		if L.Type(-1) == golua.LUA_TTABLE {
			var t ScheduledTask
			t.Fn = readString(L, -1, "fn")
			t.Every = readNumberInt(L, -1, "every")
			t.At = readString(L, -1, "at")
			t.Jitter = readNumberInt(L, -1, "jitter")
			if t.Fn != "" && (t.Every > 0 || t.At != "") {
				spec.tasks = append(spec.tasks, t)
			}
		}
		L.Pop(1)
		idx++
	}
	L.Pop(2) // schedule table + plugin global
	return spec
}

// PluginRuntime owns one plugin's long-lived execution environment.
//
// It is deliberately NOT the hook VM: hooks run on the shared, stateful plugin
// VM (their accumulated totals must stay in one place). The runtime is a SEPARATE
// VM used only for periodic jobs, whose work is inherently long-lived and
// network-bound.
type PluginRuntime struct {
	plugin   string
	vm       *VM // a private VM running the SAME plugin source
	poolName string
	name     string

	mu      sync.Mutex
	spec    scheduleSpec
	nextDue map[string]time.Time
	running map[string]bool
	stop    chan struct{}
	done    chan struct{}
	// failures counts consecutive task failures, for the hook-error surface.
	failures map[string]int
}

// startRuntime boots a private VM for the plugin and starts its scheduler.
//
// The private VM runs the same source but under a distinct name, so it does not
// collide with the adapter registry or the shared plugin VM. A plugin with no
// schedule gets no runtime at all — the common case stays exactly as cheap as
// before (one shared state, no extra VM).
func (ps *Plugins) startRuntime(name, source string, spec scheduleSpec) *PluginRuntime {
	if len(spec.tasks) == 0 || ps.vm == nil {
		return nil
	}
	rt := &PluginRuntime{
		plugin:   name,
		spec:     spec,
		nextDue:  make(map[string]time.Time, len(spec.tasks)),
		running:  make(map[string]bool, len(spec.tasks)),
		failures: make(map[string]int, len(spec.tasks)),
		stop:     make(chan struct{}),
		done:     make(chan struct{}),
	}
	// A private VM per plugin: booting one is ~0.1ms (see plugin_shard.go for the
	// measurement), which is far cheaper than the isolation it buys.
	//
	// The private VM is the SAME VM OBJECT with an empty dir — it must not
	// re-scan or re-seed the adapter directory, and its pool is private to this
	// runtime. Reusing the VM type (rather than inventing a second sandbox) keeps
	// the shared globals identical, so a plugin behaves the same whether its task
	// runs on the shared state or here.
	rt.vm = &VM{
		dir:   "",
		pools: map[string]*adapterPool{},
		// The janitor is never started for a private runtime VM: it is sized for
		// one idle state that we manage directly, and running a reclaimer over a
		// pool with a single permanent worker would be pure overhead.
		janitorStop: make(chan struct{}),
	}
	w, err := bootPluginState(source, name, ps.outboundAllowlist())
	if err != nil {
		ps.logf("[scheduler] plugin %s: private VM boot failed: %v", name, err)
		return nil
	}
	// File the state as a single-state pool so the existing acquire/release and
	// Transform machinery work unchanged.
	//
	// The Cond MUST be built from this pool's own mu (newAdapterPool does exactly
	// that). Handing it a fresh mutex instead makes cond.Wait unlock a mutex it
	// never locked, which Go reports as "unlock of unlocked mutex" and takes the
	// whole process down — not a recoverable error.
	pool := &adapterPool{
		name:       "__pluginrt_" + name,
		script:     source,
		static:     staticInfo{name: name, headers: map[string]string{}},
		pluginMode: true,
		maxW:       1,
		revision:   1,
	}
	pool.cond = sync.NewCond(&pool.mu)
	pool.idle = []*worker{w}
	pool.created = 1
	rt.vm.pools[pool.name] = pool
	rt.poolName = pool.name
	for _, t := range spec.tasks {
		rt.nextDue[t.Fn] = rt.firstDue(t)
	}
	go rt.loop()
	return rt
}

// firstDue computes when a task first runs. Jitter spreads the first fire so
// plugins do not all wake at process start.
func (rt *PluginRuntime) firstDue(t ScheduledTask) time.Time {
	now := time.Now()
	if t.At != "" {
		return nextDailyOccurrence(t.At, now)
	}
	d := time.Duration(t.Every) * time.Second
	if d <= 0 {
		d = time.Hour
	}
	j := time.Duration(t.Jitter) * time.Second
	if j > 0 {
		d += time.Duration(randInt63n(int64(j)))
	}
	return now.Add(d)
}

// nextDailyOccurrence returns the next time "HH:MM" passes after now (today if
// it has not yet passed, else tomorrow).
func nextDailyOccurrence(at string, now time.Time) time.Time {
	var hh, mm int
	if _, err := fmt.Sscanf(at, "%d:%d", &hh, &mm); err != nil || hh < 0 || hh > 23 || mm < 0 || mm > 59 {
		// A malformed time must not wedge the task forever; fall back to hourly.
		return now.Add(time.Hour)
	}
	t := time.Date(now.Year(), now.Month(), now.Day(), hh, mm, 0, 0, now.Location())
	if !t.After(now) {
		t = t.Add(24 * time.Hour)
	}
	return t
}

// runtimeTick is the scheduler's resolution. A var so tests can shorten it
// without waiting whole seconds; production always uses 1s.
var runtimeTick = time.Second

// loop is the scheduler goroutine: one ticker drives every plugin's tasks.
func (rt *PluginRuntime) loop() {
	defer close(rt.done)
	tick := time.NewTicker(runtimeTick)
	defer tick.Stop()
	for {
		select {
		case <-rt.stop:
			return
		case <-tick.C:
			rt.runDue()
		}
	}
}

// runDue launches every task whose due time has arrived. Each task runs in its
// OWN goroutine, so one long task never delays another's due time (and a
// runaway task only re-runs itself after it finishes + its next interval).
func (rt *PluginRuntime) runDue() {
	now := time.Now()
	rt.mu.Lock()
	var due []ScheduledTask
	for _, t := range rt.spec.tasks {
		if rt.running[t.Fn] {
			continue // still executing; skip this cycle
		}
		if now.Before(rt.nextDue[t.Fn]) {
			continue
		}
		rt.running[t.Fn] = true
		rt.nextDue[t.Fn] = rt.nextAfter(t, now)
		due = append(due, t)
	}
	rt.mu.Unlock()
	for _, t := range due {
		go rt.runOne(t)
	}
}

// nextAfter computes the following due time for a task that just fired.
func (rt *PluginRuntime) nextAfter(t ScheduledTask, now time.Time) time.Time {
	if t.At != "" {
		return nextDailyOccurrence(t.At, now)
	}
	d := time.Duration(t.Every) * time.Second
	if d <= 0 {
		d = time.Hour
	}
	return now.Add(d)
}

// runOne executes one task on the private VM, guarded against a Lua-level
// error. A failure (or a hook that returns an error) is recorded but never
// propagates into request forwarding.
func (rt *PluginRuntime) runOne(t ScheduledTask) {
	defer func() {
		rt.mu.Lock()
		delete(rt.running, t.Fn)
		rt.mu.Unlock()
	}()
	_, err := rt.vm.Transform(rt.poolName, t.Fn, "{}")
	rt.mu.Lock()
	if err != nil {
		rt.failures[t.Fn]++
		rt.mu.Unlock()
		rt.logf("[scheduler] plugin %s task %s failed: %v", rt.plugin, t.Fn, err)
		return
	}
	rt.failures[t.Fn] = 0
	rt.mu.Unlock()
}

func (rt *PluginRuntime) logf(format string, args ...interface{}) {
	if f := activeLogger.Load(); f != nil {
		(*f)(format, args...)
	}
}

// Stop halts the scheduler and closes the private VM.
func (rt *PluginRuntime) Stop() {
	if rt == nil {
		return
	}
	close(rt.stop)
	<-rt.done
	if rt.vm != nil {
		rt.vm.Stop()
	}
}

// activeLogger is installed by the Plugins layer so a runtime goroutine can log
// without capturing the parent (which would keep it alive past Close).
var activeLogger atomic.Pointer[func(string, ...interface{})]

// randInt63n returns a pseudo-random value in [0,n). It avoids importing math/rand
// into this file's already-large import set for one call; the quality is
// irrelevant for jitter.
func randInt63n(n int64) int64 {
	if n <= 0 {
		return 0
	}
	// xorshift seeded from wall clock — jitter only needs to differ across
	// processes, not be cryptographically strong.
	seed := time.Now().UnixNano() ^ int64(n*2654435761)
	x := uint64(seed)
	x ^= x << 13
	x ^= x >> 7
	x ^= x << 17
	return int64(x % uint64(n))
}

// sortedTaskNames returns the task function names of a spec (for diagnostics).
func (s scheduleSpec) sortedTaskNames() []string {
	out := make([]string, 0, len(s.tasks))
	for _, t := range s.tasks {
		out = append(out, t.Fn)
	}
	sort.Strings(out)
	return out
}

// readNumberInt reads a numeric field as an int. Missing/zero yields 0, which
// every caller treats as "not set" (a task with every<=0 and no at is disabled).
func readNumberInt(L *golua.State, idx int, field string) int {
	L.GetField(idx, field)
	defer L.Pop(1)
	if L.Type(-1) != golua.LUA_TNUMBER {
		return 0
	}
	return int(L.ToNumber(-1))
}