// Package memory provides temporal context tracking with recency-weighted scoring.
package memory

import (
	"math"
	"sort"
	"time"
)

// TemporalContext provides time-aware context for memory retrieval.
// It tracks temporal relationships and applies recency-based scoring.
type TemporalContext struct {
	// UserID identifies the user
	UserID string

	// SessionID identifies the current session
	SessionID string

	// QueryTime is when the query was issued
	QueryTime time.Time

	// LastInteraction is the time of the last user interaction
	LastInteraction time.Time

	// Timezone is the user's timezone
	Timezone string

	// RecencyBias is the exponential decay factor (lambda)
	// Higher values = faster decay = stronger preference for recent
	// Typical range: 0.01 (slow decay) to 0.5 (fast decay)
	RecencyBias float64

	// TemporalAnchors are specific time points of interest
	TemporalAnchors []time.Time

	// TimeOfDay context (morning, afternoon, evening, night)
	TimeOfDay string

	// DayOfWeek for weekly patterns
	DayOfWeek time.Weekday

	// SeasonalContext for seasonal patterns
	SeasonalContext string
}

// NewTemporalContext creates a new temporal context
func NewTemporalContext(userID, sessionID string) *TemporalContext {
	now := time.Now()
	return &TemporalContext{
		UserID:          userID,
		SessionID:       sessionID,
		QueryTime:       now,
		LastInteraction: now,
		RecencyBias:     0.1, // Default decay rate
		TimeOfDay:       getTimeOfDay(now),
		DayOfWeek:       now.Weekday(),
	}
}

// CalculateRecencyScore computes a recency-weighted relevance score
// using exponential decay: score = confidence * e^(-λ * age_hours)
func (tc *TemporalContext) CalculateRecencyScore(entry *MemoryEntry) float64 {
	age := tc.QueryTime.Sub(entry.Timestamp).Hours()

	// Prevent negative ages (future timestamps)
	if age < 0 {
		age = 0
	}

	// Exponential decay: score = e^(-λ * age)
	recencyScore := math.Exp(-tc.RecencyBias * age)

	// Combine with confidence
	return entry.Confidence * recencyScore
}

// CalculateCombinedScore combines multiple scoring factors
func (tc *TemporalContext) CalculateCombinedScore(entry *MemoryEntry, similarityScore float64) float64 {
	recencyScore := tc.CalculateRecencyScore(entry)

	// Weighted combination
	// similarity: 0.6, recency: 0.3, confidence: 0.1
	weights := struct {
		similarity float64
		recency    float64
		confidence float64
	}{0.6, 0.3, 0.1}

	combined := weights.similarity*similarityScore +
		weights.recency*recencyScore +
		weights.confidence*entry.Confidence

	return combined
}

// ApplyTemporalScoring applies recency scoring to a slice of entries
func (tc *TemporalContext) ApplyTemporalScoring(entries []*MemoryEntry) []*MemoryEntry {
	for _, entry := range entries {
		entry.Score = tc.CalculateRecencyScore(entry)
	}
	return entries
}

// SortByRecency sorts entries by recency score (highest first)
func (tc *TemporalContext) SortByRecency(entries []*MemoryEntry) []*MemoryEntry {
	tc.ApplyTemporalScoring(entries)

	sort.Slice(entries, func(i, j int) bool {
		return entries[i].Score > entries[j].Score
	})

	return entries
}

// FilterByTimeRange filters entries to a specific time range
func (tc *TemporalContext) FilterByTimeRange(entries []*MemoryEntry, start, end time.Time) []*MemoryEntry {
	var filtered []*MemoryEntry
	for _, entry := range entries {
		if entry.Timestamp.After(start) && entry.Timestamp.Before(end) {
			filtered = append(filtered, entry)
		}
	}
	return filtered
}

// FilterByMaxAge filters entries to those within maxAge of query time
func (tc *TemporalContext) FilterByMaxAge(entries []*MemoryEntry, maxAge time.Duration) []*MemoryEntry {
	cutoff := tc.QueryTime.Add(-maxAge)
	var filtered []*MemoryEntry
	for _, entry := range entries {
		if entry.Timestamp.After(cutoff) {
			filtered = append(filtered, entry)
		}
	}
	return filtered
}

// GroupByTimePeriod groups entries by time period
func (tc *TemporalContext) GroupByTimePeriod(entries []*MemoryEntry, period TimePeriod) map[string][]*MemoryEntry {
	groups := make(map[string][]*MemoryEntry)

	for _, entry := range entries {
		key := getTimePeriodKey(entry.Timestamp, period)
		groups[key] = append(groups[key], entry)
	}

	return groups
}

// TimePeriod represents a time grouping unit
type TimePeriod int

const (
	PeriodHour TimePeriod = iota
	PeriodDay
	PeriodWeek
	PeriodMonth
)

func getTimePeriodKey(t time.Time, period TimePeriod) string {
	switch period {
	case PeriodHour:
		return t.Format("2006-01-02-15")
	case PeriodDay:
		return t.Format("2006-01-02")
	case PeriodWeek:
		year, week := t.ISOWeek()
		return t.Format("2006") + "-W" + padInt(week, 2) + "-" + padInt(year, 4)
	case PeriodMonth:
		return t.Format("2006-01")
	default:
		return t.Format("2006-01-02")
	}
}

func padInt(n, width int) string {
	s := ""
	for i := 0; i < width; i++ {
		s = "0" + s
	}
	return s[len(s)-width:]
}

func getTimeOfDay(t time.Time) string {
	hour := t.Hour()
	switch {
	case hour >= 5 && hour < 12:
		return "morning"
	case hour >= 12 && hour < 17:
		return "afternoon"
	case hour >= 17 && hour < 21:
		return "evening"
	default:
		return "night"
	}
}

// TemporalPattern represents a detected temporal pattern
type TemporalPattern struct {
	// PatternType describes the pattern
	// Values: "daily", "weekly", "hourly", "seasonal"
	PatternType string

	// Description explains the pattern
	Description string

	// Confidence in the pattern
	Confidence float64

	// Frequency of occurrence
	Frequency int

	// TimeSlots are the typical times this pattern occurs
	TimeSlots []string

	// AssociatedTags are commonly associated with this pattern
	AssociatedTags []string
}

// DetectPatterns analyzes entries for temporal patterns
func (tc *TemporalContext) DetectPatterns(entries []*MemoryEntry) []TemporalPattern {
	if len(entries) < 5 {
		return nil // Need minimum entries for pattern detection
	}

	var patterns []TemporalPattern

	// Detect daily patterns
	dailyGroups := tc.GroupByTimePeriod(entries, PeriodDay)
	if len(dailyGroups) >= 3 {
		patterns = append(patterns, tc.analyzeDailyPatterns(dailyGroups))
	}

	// Detect hourly patterns
	hourlyDistribution := make(map[int]int)
	for _, entry := range entries {
		hour := entry.Timestamp.Hour()
		hourlyDistribution[hour]++
	}
	if pattern := tc.analyzeHourlyPatterns(hourlyDistribution); pattern != nil {
		patterns = append(patterns, *pattern)
	}

	return patterns
}

func (tc *TemporalContext) analyzeDailyPatterns(groups map[string][]*MemoryEntry) TemporalPattern {
	avgPerDay := 0
	for _, entries := range groups {
		avgPerDay += len(entries)
	}
	avgPerDay /= len(groups)

	return TemporalPattern{
		PatternType: "daily",
		Description: "Regular daily interaction pattern detected",
		Confidence:  0.7,
		Frequency:   avgPerDay,
	}
}

func (tc *TemporalContext) analyzeHourlyPatterns(distribution map[int]int) *TemporalPattern {
	if len(distribution) < 3 {
		return nil
	}

	// Find peak hours
	maxCount := 0
	peakHours := []string{}

	for hour, count := range distribution {
		if count > maxCount {
			maxCount = count
			peakHours = []string{getHourLabel(hour)}
		} else if count == maxCount {
			peakHours = append(peakHours, getHourLabel(hour))
		}
	}

	return &TemporalPattern{
		PatternType: "hourly",
		Description: "Peak activity hours detected",
		Confidence:  0.65,
		TimeSlots:   peakHours,
	}
}

func getHourLabel(hour int) string {
	if hour == 0 {
		return "12am"
	} else if hour < 12 {
		return string(rune('0'+hour%10)) + "am"
	} else if hour == 12 {
		return "12pm"
	} else {
		return string(rune('0'+(hour-12)%10)) + "pm"
	}
}

// TimeAwareRanker combines temporal and semantic ranking
type TimeAwareRanker struct {
	temporal         *TemporalContext
	recencyWeight    float64
	similarityWeight float64
	confidenceWeight float64
}

// NewTimeAwareRanker creates a new time-aware ranker
func NewTimeAwareRanker(temporal *TemporalContext) *TimeAwareRanker {
	return &TimeAwareRanker{
		temporal:         temporal,
		recencyWeight:    0.3,
		similarityWeight: 0.6,
		confidenceWeight: 0.1,
	}
}

// SetWeights configures the ranking weights
func (r *TimeAwareRanker) SetWeights(recency, similarity, confidence float64) {
	total := recency + similarity + confidence
	r.recencyWeight = recency / total
	r.similarityWeight = similarity / total
	r.confidenceWeight = confidence / total
}

// Rank applies combined scoring and sorting
func (r *TimeAwareRanker) Rank(entries []*MemoryEntry, similarityScores map[string]float64) []*MemoryEntry {
	for _, entry := range entries {
		similarity := 0.0
		if s, ok := similarityScores[entry.ID]; ok {
			similarity = s
		}

		recency := r.temporal.CalculateRecencyScore(entry)

		entry.Score = r.recencyWeight*recency +
			r.similarityWeight*similarity +
			r.confidenceWeight*entry.Confidence
	}

	sort.Slice(entries, func(i, j int) bool {
		return entries[i].Score > entries[j].Score
	})

	return entries
}