package channelbridge

import (
	"context"
	"strings"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/adapter"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/session"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
)

// This file holds the channel bridge's minimal-disturbance inbound classification
// for public platforms (DevDocs/design/12 §6 策略一/二/五). Non-owner group/stranger
// messages are judged cheaply before they reach the full agent loop, so a busy
// public group does not fling every message into an expensive LLM turn. The logic
// lives here to keep channelbridge.go under the module size bound; it never reads
// message content to decide identity — identity is already resolved structurally by
// the session/actor layer (a project red line).

// Quiet-hour defaults, mirroring the backthink service so the bridge and the
// background thinker share one do-not-disturb window (design/12 §6 策略五).
const (
	defaultQuietStartHour = 23
	defaultQuietEndHour   = 7
)

// lightVerdict is the outcome of a rule-based light judgement before the optional
// injected LightJudge is consulted (design/12 §6 策略二/五).
type lightVerdict int

const (
	// verdictRespond means the rule signals the message is worth a response.
	verdictRespond lightVerdict = iota
	// verdictSilent means the rule signals the message should be registered but not
	// answered (e.g. during quiet hours with no strong signal).
	verdictSilent
	// verdictInconclusive means the rules cannot tell; defer to the LightJudge (or
	// fail-closed to silence when none is wired).
	verdictInconclusive
)

// LightInput is the set of signals a LightJudge receives to decide response
// worthiness. Identity is already resolved structurally by the session/actor
// layer, so the judge weighs only 值不值得回 — it never decides who the sender is.
type LightInput struct {
	Msg          adapter.UnifiedMessage
	Actor        adapter.Actor
	SenderName   string
	InQuietHours bool
	QuietStart   int
	QuietEnd     int

	// Engage reports whether this is a cost-controlled participation judgment
	// (design/18): it is set only when a trigger (role-name mention / probability)
	// or an active activity window routed the message here, so the caller feeds the
	// group context and persona prompt ONCE and never on every chat message. A
	// legacy (design/12 §6) inconclusive judgment leaves it false.
	Engage bool
	// PersonaPrompt is the current persona's identity/system-prompt block, so the
	// judge can weigh the role's tone without ever deciding identity. It carries no
	// owner secret (a project red line).
	PersonaPrompt string
	// RecentContext is the group conversation's recent N messages rendered with each
	// sender's display name, plus the triggering message, so the judge can tell
	// whether the topic is worth participating in.
	RecentContext string
	// TriggerWords are the current persona's role-name reminder words (design/18 §2),
	// passed as context so the judge knows which word was mentioned.
	TriggerWords []string
}

// LightDecision is a LightJudge's verdict.
type LightDecision struct {
	// Respond is the legacy design/12 §6 simple verdict (respond or not). It is kept
	// for backward compatibility; the design/18 fields below carry the structured
	// participation verdict that the engage engine reads.
	Respond bool
	Reason  string

	// Interesting reports whether she finds the topic interesting (design/18) — the
	// signal to enter/remain ACTIVE.
	Interesting bool
	// WorthReply reports whether the message is worth a reply.
	WorthReply bool
	// AvoidTopic reports whether the topic should be avoided (sensitive / privet /
	// red-line), so she does not engage even when otherwise interested.
	AvoidTopic bool
}

// LightJudge is the optional cost-controlled light-response judge (design/12 §6
// 策略二/五). The bridge consults it only when the built-in rule judge is
// inconclusive, so a chat message is not repeatedly sent to an expensive LLM. A
// nil LightJudge (the default) keeps the bridge rule-only and fail-closed toward
// silence (不打扰为第一原则). The production wiring does not supply one yet, so the
// seam is ready but not token-consuming until it is deliberately wired.
type LightJudge interface {
	Judge(ctx context.Context, in LightInput) (LightDecision, error)
}

// highValueKeywords is the small term list the rule judge matches to decide a
// message is worth a response even when the sender was not directly addressed
// (设计/12 §6 策略二: 关键词重要度). It is a cheap substring match — never an LLM call,
// and never used to infer identity.
var highValueKeywords = []string{
	"紧急", "救命", "故障", "坏掉", "坏了", "报错", "出错", "崩溃",
	"求助", "帮帮我", "help", "urgent", "error", "bug",
}

// isLowValueEvent reports whether a non-owner message is platform/system noise
// that must be registered but never drives the full agent loop (设计/12 §6 策略一).
// It is only consulted for non-owner messages: a system/synthetic sender is the
// canonical low-value signal. Messages with no meaningful chat text are dropped at
// the bridge head anyway, so this primarily gates system-actor notifications.
func isLowValueEvent(actor adapter.Actor) bool {
	return actor.IsSystem()
}

// hasHighValueKeyword reports whether text carries a term worth responding to even
// when the sender was not directly addressed. Kept tiny so the rule path stays O(1)
// per message.
func hasHighValueKeyword(text string) bool {
	lower := strings.ToLower(text)
	for _, k := range highValueKeywords {
		if strings.Contains(lower, k) {
			return true
		}
	}
	return false
}

// ruleLightJudge decides response-worthiness from cheap rule signals only
// (设计/12 §6 策略二/五). Priority: a direct mention, a mention of the owner's display
// name, a high-value keyword, then a quiet-hours bias toward silence; otherwise the
// verdict is inconclusive (defer to the injected LightJudge, else silence). It
// reads only already-resolved actor metadata and message content — never infers
// identity.
func (b *Bridge) ruleLightJudge(msg adapter.UnifiedMessage, actor adapter.Actor, inQuiet bool) lightVerdict {
	if len(msg.Mentions) > 0 {
		return verdictRespond
	}
	if b.owner != nil && b.owner.DisplayName != "" &&
		strings.Contains(msg.Content, b.owner.DisplayName) {
		return verdictRespond
	}
	if hasHighValueKeyword(msg.Content) {
		return verdictRespond
	}
	if inQuiet {
		return verdictSilent
	}
	return verdictInconclusive
}

// shouldRespond implements the minimal-disturbance classification for a non-owner
// inbound message (设计/12 §6 策略一/二/五 + design/18 §2/§4/§5). It returns whether
// the message should drive the full agent loop and reply, or be registered-and-
// silenced. Owner messages never reach here (processFrom gates on !actor.IsOwner),
// so owner-private chat and owner group @/high-value replies are untouched. sess is
// the isolated group/stranger session binding the message resolved to, so the
// participation engine can read the group's recent context when it probes.
func (b *Bridge) shouldRespond(ctx context.Context, msg adapter.UnifiedMessage, actor adapter.Actor, sess session.Session) (bool, string) {
	// 策略一: platform/system noise → register only, never the full loop.
	if isLowValueEvent(actor) {
		b.log.Debug("non-owner low-value system event, registered only",
			"platform", msg.Platform, "channel", msg.ChannelID, "actor_role", actor.Role)
		return false, "low-value system event; registered only"
	}

	// 策略二/五: rule-based light judgement, quiet-hours aware. A direct @, a mention
	// of the owner's display name, or a high-value keyword always responds; quiet
	// hours bias toward silence. The participation engine is only consulted on the
	// inconclusive remainder.
	inQuiet := b.inQuietHours(b.now())
	switch b.ruleLightJudge(msg, actor, inQuiet) {
	case verdictRespond:
		return true, "rule signal: worth responding"
	case verdictSilent:
		b.log.Debug("non-owner message silenced (quiet/no signal), registered only",
			"platform", msg.Platform, "channel", msg.ChannelID, "quiet", inQuiet, "actor_role", actor.Role)
		return false, "rule signal: not worth responding"
	}

	// The cheap rules are inconclusive. When the participation engine (design/18) is
	// configured it takes over and only consults the light judge on an actual trigger
	// (role-name mention / probability) or an active activity window — never on every
	// chat message, so cost stays controlled (a red line). Without engage
	// configuration the bridge keeps the pre-engage legacy behaviour: consult the
	// optional injected light judge on every inconclusive message, else fail-closed.
	if !b.engageConfigured() {
		return b.legacyLightJudge(ctx, msg, actor, inQuiet)
	}
	return b.engageDecision(ctx, msg, actor, sess, inQuiet)
}

// legacyLightJudge is the pre-design/18 inconclusive handling: consult the optional
// injected light judge, fail-closed toward silence on error or absence
// (不打扰为第一原则). It is only reached when the participation engine is not wired.
func (b *Bridge) legacyLightJudge(ctx context.Context, msg adapter.UnifiedMessage, actor adapter.Actor, inQuiet bool) (bool, string) {
	if b.light != nil {
		d, err := b.light.Judge(ctx, LightInput{
			Msg: msg, Actor: actor, SenderName: senderDisplayName(msg, actor),
			InQuietHours: inQuiet, QuietStart: b.quietStartHour, QuietEnd: b.quietEndHour,
		})
		if err == nil {
			if d.Respond {
				return true, "light judge: " + d.Reason
			}
			return false, "light judge: " + d.Reason
		}
		b.log.Warn("light judge failed; silencing", "error", err)
	}
	b.log.Debug("non-owner message has no rule signal, silenced",
		"platform", msg.Platform, "channel", msg.ChannelID, "actor_role", actor.Role)
	return false, "no rule signal; silenced (fail-closed)"
}

// mentionsTriggerWord reports whether the message content names the current persona
// via one of its trigger words (design/18 §2 触发②). It is a cheap substring match —
// never an LLM call, and never used to infer who the sender is.
func (b *Bridge) mentionsTriggerWord(text string) bool {
	if text == "" {
		return false
	}
	for _, w := range b.triggerWords {
		if w != "" && strings.Contains(text, w) {
			return true
		}
	}
	return false
}

// registerSilenced persists a silenced non-owner inbound turn into its isolated
// session's platform log so the adapter log page still renders the non-owner
// stream (design/16 §4.6 §4), then stops — no loop, no reply. a is the account
// adapter that received the message, so the log is tagged with the adapter config.
// It is the 登记 side of the minimal-disturbance path.
func (b *Bridge) registerSilenced(ctx context.Context, msg adapter.UnifiedMessage, actor adapter.Actor, sess session.Session, a adapter.PlatformAdapter) {
	b.persistIsolated(ctx, history.RoleUser, msg.Content, deviceIDFor(msg), sess, msg.Platform, senderDisplayName(msg, actor), adapterName(a))
	b.log.Debug("non-owner message silenced, registered only",
		"platform", msg.Platform, "channel", msg.ChannelID, "session", sess.SessionID)
}

// inQuietHours reports whether at falls inside the configured do-not-disturb
// window (shared semantics with backthink: equal non-zero hours disable it, and a
// window that wraps midnight is handled). It is a pure method on Bridge so tests
// drive it deterministically via the Now source.
func (b *Bridge) inQuietHours(at time.Time) bool {
	h := at.Hour()
	start, end := b.quietStartHour, b.quietEndHour
	if start <= end {
		return h >= start && h < end
	}
	return h >= start || h < end
}