package backthink

import (
	"fmt"
	"strings"
	"time"
)

// Importance is the estimated severity of an event that woke a thinking pass.
// Under design/20 §2 P2 it no longer decides *whether* she wants to speak (her
// conclusion does); it decides the hard-gate exemptions: a critical safety event
// punches through work/busy and quiet hours (裁决 07.4.2), and a high event still
// passes quiet hours (the pre-existing cascade semantics).
type Importance int

const (
	// ImportanceLow is a routine trigger (e.g. the periodic heartbeat).
	ImportanceLow Importance = iota
	// ImportanceNormal is an ordinary event worth reflecting on (device change).
	ImportanceNormal
	// ImportanceHigh is a notable event (a reminder the user set firing).
	ImportanceHigh
	// ImportanceCritical is a safety-critical event that punches through
	// work/busy and quiet hours (裁决 07.4.2 安全域豁免).
	ImportanceCritical
)

// String returns a stable label for logs and records.
func (i Importance) String() string {
	switch i {
	case ImportanceLow:
		return "low"
	case ImportanceNormal:
		return "normal"
	case ImportanceHigh:
		return "high"
	case ImportanceCritical:
		return "critical"
	default:
		return fmt.Sprintf("importance(%d)", int(i))
	}
}

// longIdleThreshold is the gap after the owner's last message beyond which the
// activity gate only lets a genuinely important event through — except heartbeat
// passes, which are never held by a long-silent gap (裁决 07.4.3). Compile-time
// so no magic number appears.
const longIdleThreshold = 2 * time.Hour

// UserState describes the user's current condition as observed from device
// telemetry (heart rate, sleep) and schedule (work, busy). It is the negative
// signal in the interrupt decision: a sleeping, working or busy user is left
// alone. Boredom (0..1) is the soft positive dial that widens interruption.
type UserState struct {
	// HeartRateBPM is the current heart rate, 0 when unknown.
	HeartRateBPM int
	// Sleeping reports whether the user is currently asleep from sleep tracking.
	Sleeping bool
	// Working reports whether the user is in a work/scheduled block.
	Working bool
	// Busy reports whether the user is marked busy (calendar / do-not-disturb).
	Busy bool
	// Boredom ranges 0..1. Higher boredom means the user is idle and more open
	// to a gentle interruption. Under design/20 §2 P2 the push intent is her own
	// conclusion, so this dial no longer gates the decision; it is kept as a
	// telemetry signal her judgment already absorbs.
	Boredom float64
}

// String returns a concise human-readable summary for logs/records.
func (s UserState) String() string {
	return fmt.Sprintf("bpm=%d sleeping=%v working=%v busy=%v boredom=%.2f",
		s.HeartRateBPM, s.Sleeping, s.Working, s.Busy, s.Boredom)
}

// DecisionInput is the set of signals Decide weighs: the event's importance, the
// current wall-clock time, the user's current state and their boredom.
type DecisionInput struct {
	// Trigger is a human-readable source label, recorded for traceability.
	Trigger string
	// Import is the event's estimated importance.
	Import Importance
	// At is the current wall-clock time, in the local timezone used for the
	// do-not-disturb window.
	At time.Time
	// UserState carries the user's physiological/schedule condition.
	UserState UserState
	// LastActivity is the wall-clock time of the owner's most recent message.
	// HasActivity reports whether a user message was found; when false the
	// activity gate falls through without guessing.
	LastActivity time.Time
	// HasActivity reports whether LastActivity is meaningful.
	HasActivity bool
	// ConclusionPush 是她自己思考结论的推送意愿（design/20 §2 P2）：「想不想说」
	// 由她的结论决定，本决策只回答「此刻能不能说」。
	ConclusionPush bool
	// Heartbeat 标记本轮是否为心跳类触发（周期心跳或启动轮）。裁决 07.4.3：
	// 长期静默段不拦心跳——主人久未回应时，主动关心仍可照常发出。
	Heartbeat bool
}

// Decision is the outcome of Decide.
type Decision struct {
	// ShouldPush reports whether the user should be interrupted.
	ShouldPush bool
	// Reason is a short human-readable justification, surfaced on the panel.
	Reason string
}

// Decide 是生产路径的打扰决策（design/12 §2 + design/20 §2 P2 + 裁决 07.4.2/07.4.3）。
// 「想不想说」交给她的结论（ConclusionPush），本方法只判「此刻能不能说」，评估顺序
// 刻意 fail-closed（宁可不打扰）：
//
//  0. 她的结论要求不推送 → 不推送。
//  1. 用户在睡 → 绝不打扰。
//  2. 上班/忙碌 → 仅 critical 安全事件可打扰。
//  3. 安静时段（深夜窗口）→ 挡常规推送；critical 安全事件穿透（裁决 07.4.2，
//     与 design/12 §6 策略五同口径），high 沿袭原级联口径照常放行。
//  4. 其余时段 → 放行（是否值得说已由她的结论回答）。
//
// 通过硬门后再过活动软门：刚聊过天或主人久未回应时酌情扣下；心跳类触发在
// 长期静默段不拦（裁决 07.4.3，主动关心照常发出）。频率门（PushGate）在推送器
// 内部单独生效，不在此处。
func (b *Backthink) Decide(in DecisionInput) Decision {
	if !in.ConclusionPush {
		return Decision{ShouldPush: false, Reason: "conclusion requested no push"}
	}
	if d := b.baseDecide(in); !d.ShouldPush {
		return d
	}
	if held, why := b.activityHeld(in); held {
		return Decision{ShouldPush: false, Reason: "proactive push held: " + why}
	}
	return Decision{ShouldPush: true, Reason: "proactive push approved"}
}

// baseDecide 是不打扰硬门级联（design/12 §2）。critical 安全事件走安全域分支：
// 工作忙碌与安静时段都放行（裁决 07.4.2 安全域豁免）；睡眠仍是绝对不打扰。
// 白天是否「值得说」不再由重要性/无聊度判定——那是她的结论（design/20 §2 P2）
// 已经回答的问题。
func (b *Backthink) baseDecide(in DecisionInput) Decision {
	s := in.UserState
	if s.Sleeping {
		return Decision{ShouldPush: false, Reason: "user is asleep; not interrupting"}
	}
	if (s.Working || s.Busy) && in.Import < ImportanceCritical {
		return Decision{ShouldPush: false, Reason: "user is working/busy; not interrupting"}
	}
	if b.inQuietHours(in.At) {
		if in.Import >= ImportanceCritical {
			return Decision{ShouldPush: true, Reason: "quiet hours but critical safety event bypasses"}
		}
		if in.Import >= ImportanceHigh {
			return Decision{ShouldPush: true, Reason: "quiet hours but event is important"}
		}
		return Decision{ShouldPush: false, Reason: "quiet hours; not interrupting"}
	}
	return Decision{ShouldPush: true, Reason: "worth interrupting"}
}

// activityHeld 是活动感知软门（design/12 §6 + 裁决 07.4.3）。它把「不打扰」延伸到
// 对话自身的节奏，返回是否扣下与简短理由：
//
//   - 最近 RecentChatCooldown 内主人刚说过话 → 对话正热，非 critical 扣下，
//     不在聊天中途插话；
//   - 超过 longIdleThreshold 未说话 → 主人久未回应，仅真正重要的事件值得唤醒；
//     心跳类触发（含启动轮）例外照常放行（裁决 07.4.3：长期静默段不拦心跳，
//     主动关心仍可发出）；
//   - 其间与活动状态未知 → 不软化，照硬门结论通过。
//
// 活动是软信号：硬门（baseDecide）独立生效，频率门（PushGate）在推送器内部生效。
func (b *Backthink) activityHeld(in DecisionInput) (bool, string) {
	if !in.HasActivity {
		return false, ""
	}
	since := in.At.Sub(in.LastActivity)
	if since <= b.cfg.RecentChatCooldown {
		if in.Import >= ImportanceCritical {
			return false, ""
		}
		return true, "owner just chatted"
	}
	if since >= longIdleThreshold {
		if in.Heartbeat {
			return false, ""
		}
		if in.Import >= ImportanceHigh {
			return false, ""
		}
		return true, "owner away a long while"
	}
	return false, ""
}

// inQuietHours reports whether at falls inside the configured do-not-disturb
// window. The window may wrap midnight (e.g. 23:00-07:00); two equal non-zero
// hours disable it.
func (b *Backthink) inQuietHours(at time.Time) bool {
	h := at.Hour()
	start, end := b.cfg.QuietStartHour, b.cfg.QuietEndHour
	if start <= end {
		return h >= start && h < end
	}
	return h >= start || h < end
}

// PushKind classifies a proactive message into one of a few flavors so the
// frequency gate can limit each flavor within a window, avoiding same-style spam
// (design/12 §6 策略二). It is a soft tag derived from the message body's
// keywords — it affects pacing, never identity or permission.
type PushKind int

const (
	// KindGreeting is a warm hello / good-morning / good-night opener.
	KindGreeting PushKind = iota
	// KindReminder is a nudge about a schedule, task or deadline.
	KindReminder
	// KindShare is a discovery, observation or interesting find.
	KindShare
	// KindCare is a warm, caring check-in about the owner's wellbeing.
	KindCare
)

// String returns a stable label for logs and records.
func (k PushKind) String() string {
	switch k {
	case KindGreeting:
		return "greeting"
	case KindReminder:
		return "reminder"
	case KindShare:
		return "share"
	case KindCare:
		return "care"
	default:
		return fmt.Sprintf("pushkind(%d)", int(k))
	}
}

// classifyPush assigns a PushKind to a proactive message from its keyword
// content. A message that matches no flavor defaults to KindCare (the warm,
// generic intent of an unsolicited proactive note), which is the least
// spam-prone grouping. Priority is reminder > care > greeting > share so the
// dominant intent wins when several keywords co-occur.
func classifyPush(message string) PushKind {
	switch {
	case hasAnyKeyword(message, kindReminderKeywords...):
		return KindReminder
	case hasAnyKeyword(message, kindCareKeywords...):
		return KindCare
	case hasAnyKeyword(message, kindGreetingKeywords...):
		return KindGreeting
	case hasAnyKeyword(message, kindShareKeywords...):
		return KindShare
	default:
		return KindCare
	}
}

// keyword sets for classifyPush. They are package vars (not consts) so the
// classification stays flexible and testable, but they are immutable by
// convention and never mutated at run time.
var (
	kindReminderKeywords = []string{"提醒", "记得", "别忘了", "该去", "日程", "会议", "体检", "吃药", "喝药", "到点", "几点", "还有", "迟到", "明天", "马上", "最后", "截止"}
	kindCareKeywords     = []string{"关心", "最近", "辛苦", "注意身体", "照顾好", "好好休息", "心情", "还好", "想你了", "想我", "担心", "保重", "你还好", "陪你", "累"}
	kindGreetingKeywords = []string{"早安", "晚安", "早上好", "中午好", "晚上好", "午安", "回来", "吃饭", "睡了"}
	kindShareKeywords    = []string{"发现", "分享", "看到", "听说", "注意到", "告诉你", "有个", "想到", "有意思", "有趣", "你知道吗"}
)

// hasAnyKeyword reports whether s contains any of the given substrings.
func hasAnyKeyword(s string, subs ...string) bool {
	for _, sub := range subs {
		if strings.Contains(s, sub) {
			return true
		}
	}
	return false
}