package focus

import (
	"context"
	"keel/internal/ai"
	"keel/internal/enforce"
	"keel/internal/evidence"
	"keel/internal/mode/focus/domain"
	"keel/internal/store"
	"log"
	"strings"
	"time"
)

const (
	driftDebounce  = 10 * time.Second
	driftTimeout   = 30 * time.Second
	enforceTimeout = 5 * time.Second
	nudgeDebounce  = 5 * time.Minute
	nudgeTimeout   = 30 * time.Second
)

const recentTitlesMax = 10

const (
	driftIdle     = "idle"
	driftPending  = "pending"
	driftOnTask   = "ontask"
	driftDrifting = "drifting"
)

// SetDriftJudge injects the AI drift judge. A nil judge keeps local matching
// working; unmatched windows simply stay idle.
func (c *Mode) SetDriftJudge(j ai.DriftJudge) {
	c.mu.Lock()
	c.judge = j
	c.mu.Unlock()
}

// SetGuard injects the OS enforcement guard. A nil guard disables window-minimize
// enforcement; everything else behaves identically.
func (c *Mode) SetGuard(g enforce.Guard) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.guard = g
}

// SetNudge injects the AI semantic nudge judge. A nil nudger disables nudging;
// local matching and the drift judge are unaffected.
func (c *Mode) SetNudge(n ai.Nudger) {
	c.mu.Lock()
	c.nudge = n
	c.mu.Unlock()
}

// commitmentLineLocked renders the active commitment as a single line for AI
// prompts, or "" if there is none. Caller holds mu.
func (c *Mode) commitmentLineLocked() string {
	if c.commitment == nil {
		return ""
	}
	return c.commitment.NextAction + " — " + c.commitment.SuccessCondition
}

// recentTitlesForTest returns a copy of the recent-titles ring (test-only).
func (c *Mode) recentTitlesForTest() []string {
	c.mu.Lock()
	defer c.mu.Unlock()
	return append([]string(nil), c.recentTitles...)
}

// resetDriftLocked clears all drift machinery for a fresh session. Caller holds mu.
func (c *Mode) resetDriftLocked() {
	c.driftStatus = driftIdle
	c.driftReason = ""
	c.driftGen++
	c.nudgeEpoch++
	c.lastJudgedAt = time.Time{}
	c.judgedWindows = map[string]ai.Verdict{}
	c.recentTitles = nil
	c.nudgeMessage = ""
	c.lastNudgedAt = time.Time{}
}

// OnTask appends the current window class to the session allowed-context, clears
// drift, drops the cached verdict for the current window, and persists. The
// class now matches locally and is never re-judged.
func (c *Mode) OnTask() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.runtimeState != domain.RuntimeActive {
		return ErrNotActive
	}
	var class string
	if c.stats != nil {
		class = c.stats.Current.Class
	}
	if strings.TrimSpace(class) != "" {
		ac := domain.AllowedContext{WindowClasses: c.allowedClasses}
		if !evidence.MatchesAllowed(ac, class, "") {
			c.allowedClasses = append(c.allowedClasses, strings.TrimSpace(class))
		}
		delete(c.judgedWindows, verdictKey(class, c.stats.Current.Title))
	}
	c.driftStatus = driftOnTask
	c.driftReason = ""
	return c.persistLocked()
}

// Refocus clears the current drift verdict without changing allowed-context, and
// drops the cached verdict for the current window so it may be judged again later.
func (c *Mode) Refocus() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.runtimeState != domain.RuntimeActive {
		return ErrNotActive
	}
	if c.stats != nil {
		delete(c.judgedWindows, verdictKey(c.stats.Current.Class, c.stats.Current.Title))
	}
	c.driftStatus = driftIdle
	c.driftReason = ""
	return c.persistLocked()
}

// RecordWindow ingests one sensor observation. It accumulates time only while
// Active, always tracks the latest window for display, and fires onChange after
// releasing the mutex.
func (c *Mode) RecordWindow(snap evidence.WindowSnapshot) {
	c.mu.Lock()
	c.latestWindow = snap
	if c.runtimeState != domain.RuntimeActive || c.stats == nil {
		c.mu.Unlock()
		c.notify()
		return
	}
	now := c.clock()
	_ = store.AppendFocus(c.sessionsDir, c.stats.SessionID, focusEvent(now, snap))
	c.applyEvent(now, snap)
	c.recordTitleLocked(snap.Title)
	launch := c.evaluateDriftLocked(now, snap)
	enforceAct := c.enforceActionLocked()
	c.mu.Unlock()
	if launch != nil {
		go launch()
	}
	if enforceAct != nil {
		go enforceAct()
	}
	c.notify()
}

// enforceActionLocked returns the minimize thunk when this observation should be
// enforced — guard wired, level is block, and drift is confirmed — else nil. The
// returned func performs blocking X11 I/O and MUST run after the caller releases
// c.mu, following the off-lock async-I/O discipline used by the other roles.
func (c *Mode) enforceActionLocked() func() {
	if c.guard == nil || c.enforcementLevel != domain.EnforcementBlock || c.driftStatus != driftDrifting {
		return nil
	}
	guard := c.guard
	return func() {
		ctx, cancel := context.WithTimeout(context.Background(), enforceTimeout)
		defer cancel()
		if err := guard.MinimizeActive(ctx); err != nil {
			log.Printf("focus: enforce minimize failed: %v", err)
		}
	}
}

// evaluateDriftLocked runs the local-first drift pipeline for one observation
// and updates synchronous drift state. When an async judgment is warranted it
// returns the judging closure; the caller runs it in a goroutine after
// releasing the mutex (the M2 RequestCoach discipline). Caller holds mu and has
// already verified the runtime is Active.
func (c *Mode) evaluateDriftLocked(now time.Time, snap evidence.WindowSnapshot) func() {
	class, title := snap.Class, snap.Title

	// 1. Local match: authoritative on-task, no LLM. This is also the ONLY path
	// where the semantic nudge runs — the drift judge stays silent here, so the
	// two are mutually exclusive per observation.
	ac := domain.AllowedContext{WindowClasses: c.allowedClasses}
	if evidence.MatchesAllowed(ac, class, title) {
		c.driftStatus = driftOnTask
		c.driftReason = ""
		return c.maybeNudgeLocked(now)
	}

	// Past this point the window is not a local on-task match: the on-task
	// stretch (if any) has ended. Void any soft nudge tied to it and advance the
	// epoch so an in-flight nudge result is discarded rather than surfacing stale
	// when the user returns.
	c.nudgeMessage = ""
	c.nudgeEpoch++

	// 2. Per-window cache, keyed by class+title. A verdict for one window of an
	// app must not leak to a sibling window of the same class — a browser hosts
	// both an on-task reading page and an off-task chat under one window class, so
	// keying by class alone latched one tab's verdict onto every other tab.
	key := verdictKey(class, title)
	if v, ok := c.judgedWindows[key]; ok {
		c.applyVerdictLocked(v)
		return nil
	}

	// 3. No judge wired: never block; leave idle.
	if c.judge == nil {
		c.driftStatus = driftIdle
		c.driftReason = ""
		return nil
	}

	// 4. Debounce: at most one judgment per driftDebounce window.
	if !c.lastJudgedAt.IsZero() && now.Sub(c.lastJudgedAt) < driftDebounce {
		return nil
	}

	prevStatus, prevReason := c.driftStatus, c.driftReason
	c.driftGen++
	gen := c.driftGen
	c.lastJudgedAt = now
	c.driftStatus = driftPending
	c.driftReason = ""
	judge := c.judge
	commitment := c.commitmentLineLocked()

	return func() {
		ctx, cancel := context.WithTimeout(context.Background(), driftTimeout)
		defer cancel()
		v, err := judge.JudgeDrift(ctx, commitment, class, title)

		c.mu.Lock()
		if gen != c.driftGen || c.runtimeState != domain.RuntimeActive {
			c.mu.Unlock()
			return // stale: a newer judgment started or the session ended
		}
		if err != nil {
			// Degrade: never fabricate drift. Revert the optimistic pending.
			if c.driftStatus == driftPending {
				c.driftStatus = prevStatus
				c.driftReason = prevReason
			}
			c.mu.Unlock()
			log.Printf("focus: drift judge failed: %v", err)
			c.notify()
			return
		}
		c.judgedWindows[key] = v
		var enforceAct func()
		if c.stats != nil && verdictKey(c.stats.Current.Class, c.stats.Current.Title) == key {
			c.applyVerdictLocked(v)
			enforceAct = c.enforceActionLocked()
		}
		c.mu.Unlock()
		if enforceAct != nil {
			enforceAct()
		}
		c.notify()
	}
}

// maybeNudgeLocked decides whether to launch a semantic nudge on the on-task
// local-match path. It returns the nudging closure when eligible (judge wired,
// at least two titles of history, debounce elapsed), else nil. The closure
// follows the drift-judge discipline: it runs in a goroutine after the caller
// releases the mutex, re-acquires the lock, guards on nudgeEpoch (the current
// on-task-stretch id), so a nudge whose stretch has since ended — a drift
// episode or a session change — is discarded rather than surfacing stale, never
// fabricates a concern on error, and notifies only after unlocking. Caller holds
// mu and has already verified the runtime is Active.
func (c *Mode) maybeNudgeLocked(now time.Time) func() {
	if c.nudge == nil || len(c.recentTitles) < 2 {
		return nil
	}
	if !c.lastNudgedAt.IsZero() && now.Sub(c.lastNudgedAt) < nudgeDebounce {
		return nil
	}
	c.lastNudgedAt = now
	epoch := c.nudgeEpoch
	nudge := c.nudge
	commitment := c.commitmentLineLocked()
	titles := append([]string(nil), c.recentTitles...)

	return func() {
		ctx, cancel := context.WithTimeout(context.Background(), nudgeTimeout)
		defer cancel()
		msg, err := nudge.Nudge(ctx, commitment, titles)

		c.mu.Lock()
		if epoch != c.nudgeEpoch || c.runtimeState != domain.RuntimeActive {
			c.mu.Unlock()
			return // stale: the on-task stretch ended (drift episode) or the session changed
		}
		if err != nil {
			c.mu.Unlock()
			log.Printf("focus: nudge failed: %v", err)
			return // never fabricate a concern; leave any prior message intact
		}
		c.nudgeMessage = msg // "" clears a prior advisory once back on trajectory
		c.mu.Unlock()
		c.notify()
	}
}

// recordTitleLocked appends a non-empty title to the recent ring, skipping a
// consecutive duplicate, and caps the ring at recentTitlesMax. Caller holds mu.
func (c *Mode) recordTitleLocked(title string) {
	t := strings.TrimSpace(title)
	if t == "" {
		return
	}
	if n := len(c.recentTitles); n > 0 && c.recentTitles[n-1] == t {
		return
	}
	c.recentTitles = append(c.recentTitles, t)
	if len(c.recentTitles) > recentTitlesMax {
		c.recentTitles = c.recentTitles[len(c.recentTitles)-recentTitlesMax:]
	}
}

// verdictKey identifies the judged window for the per-window verdict cache. It
// combines the window class with the scrubbed, casefolded title so sibling
// windows of one app (a browser's reading tab vs its chat tab) are judged
// independently, while transient title noise (clocks, counts) does not split a
// window into ever-changing keys that defeat the cache.
func verdictKey(class, title string) string {
	return strings.ToLower(strings.TrimSpace(class)) + "\x00" + strings.ToLower(evidence.ScrubTitle(title))
}

// applyVerdictLocked maps a verdict onto drift state. Caller holds mu.
func (c *Mode) applyVerdictLocked(v ai.Verdict) {
	if v.OnTask {
		c.driftStatus = driftOnTask
		c.driftReason = ""
		return
	}
	c.driftStatus = driftDrifting
	c.driftReason = v.Reason
}