package bot

import (
	"fmt"
	"math"
	"strings"
	"time"

	"worktimeBot/internal/db"
)

// Burnout scoring model
// ======================
// Total score out of 100, computed as a weighted sum of signals:
//
//  1. Consecutive workdays  (0-25 pts)
//     Measures how many days the user has worked without a break.
//     0 days: 0, 1-3: 5, 4-6: 15, 7+: 25
//
//  2. Long hours today      (0-20 pts)
//     Measures daily work duration.
//     <8h: 0, 8-10h: 10, 10-12h: 15, 12h+: 20
//
//  3. Reduced breaks        (0-15 pts)
//     Measures break ratio (break / (work+break)).
//     >20%: 0, 10-20%: 5, 5-10%: 10, <5%: 15
//
//  4. Weekend work          (0-15 pts)
//     Working on Saturday or Sunday in user's timezone.
//     Not weekend: 0, Weekend: 15
//
//  5. Work trend            (0-15 pts)
//     Compares last 3 days to the 3 before that.
//     Decreasing: 0, Stable: 5, Increasing: 15
//
//  6. Late-night work       (0-10 pts)
//     Last event after typical working hours.
//     Before 20:00: 0, 20:00-22:00: 5, After 22:00: 10
//
// Total -> Concern level:
//   0-20:  Healthy
//   21-40: Mild concern
//   41-60: Moderate concern
//   61+:   High concern

// BurnoutLevel represents the severity of burnout indicators.
type BurnoutLevel int

const (
	BurnoutHealthy  BurnoutLevel = 0
	BurnoutMild     BurnoutLevel = 1
	BurnoutModerate BurnoutLevel = 2
	BurnoutHigh     BurnoutLevel = 3
)

func (b BurnoutLevel) String() string {
	switch b {
	case BurnoutHealthy:
		return "Healthy"
	case BurnoutMild:
		return "Mild concern"
	case BurnoutModerate:
		return "Moderate concern"
	case BurnoutHigh:
		return "High concern"
	default:
		return "Unknown"
	}
}

// BurnoutResult holds the full burnout assessment.
type BurnoutResult struct {
	Score           int
	Level           BurnoutLevel
	ConsecutivePts  int
	LongHoursPts    int
	BreakRatioPts   int
	WeekendPts      int
	TrendPts        int
	LateNightPts    int
	ConsecutiveDays int
	WorkSeconds     int64
	BreakSeconds    int64
	TrendDirection  string
}

// assessBurnout computes a burnout assessment for a user.
func (h *Handler) assessBurnout(userID int64, loc *time.Location) (*BurnoutResult, error) {
	now := time.Now().In(loc)
	today := now.Format(DateLayout)

	result := &BurnoutResult{}

	// 1. Consecutive workdays
	stats, err := h.DB.GetOrCreateRPGStats(userID)
	if err == nil {
		result.ConsecutiveDays = stats.CurrentStreak
	}
	switch {
	case result.ConsecutiveDays >= 7:
		result.ConsecutivePts = 25
	case result.ConsecutiveDays >= 4:
		result.ConsecutivePts = 15
	case result.ConsecutiveDays >= 1:
		result.ConsecutivePts = 5
	}

	// 2. Long hours today
	todayEvents, _ := h.DB.EventsForDayByDate(userID, today)
	if len(todayEvents) > 0 {
		day, _ := h.DB.GetDay(userID, today)
		if day != nil {
			y, m, d := now.Date()
			dayStart := time.Date(y, m, d, 0, 0, 0, 0, loc).Unix()
			dayEnd := now.Unix()
			totals := ComputeDailyTotals(todayEvents, day.MinBreakThreshold, dayStart, dayEnd)
			result.WorkSeconds = totals.TotalSeconds
			result.BreakSeconds = totals.BreakSeconds

			workHours := float64(totals.TotalSeconds) / secondsPerHour
			switch {
			case workHours >= 12:
				result.LongHoursPts = 20
			case workHours >= 10:
				result.LongHoursPts = 15
			case workHours >= 8:
				result.LongHoursPts = 10
			}

			// 3. Reduced breaks
			total := totals.TotalSeconds + totals.BreakSeconds
			if total > 0 {
				breakRatio := float64(totals.BreakSeconds) / float64(total) * 100
				switch {
				case breakRatio < 5:
					result.BreakRatioPts = 15
				case breakRatio < 10:
					result.BreakRatioPts = 10
				case breakRatio < 20:
					result.BreakRatioPts = 5
				}
			}

			// 6. Late-night work
			if len(todayEvents) > 0 {
				lastEvent := todayEvents[len(todayEvents)-1]
				lt := time.Unix(lastEvent.OccurredAt, 0).In(loc)
				minutes := lt.Hour()*60 + lt.Minute()
				switch {
				case minutes >= 22*60:
					result.LateNightPts = 10
				case minutes >= 20*60:
					result.LateNightPts = 5
				}
			}
		}
	}

	// 4. Weekend work
	weekday := now.Weekday()
	if weekday == time.Saturday || weekday == time.Sunday {
		if result.WorkSeconds > 0 {
			result.WeekendPts = 15
		}
	}

	// 5. Work trend (last 3 days vs 3 before that)
	result.TrendPts, result.TrendDirection = computeTrend(h.DB, userID, today, loc)

	// Total
	result.Score = result.ConsecutivePts + result.LongHoursPts + result.BreakRatioPts +
		result.WeekendPts + result.TrendPts + result.LateNightPts

	switch {
	case result.Score >= 61:
		result.Level = BurnoutHigh
	case result.Score >= 41:
		result.Level = BurnoutModerate
	case result.Score >= 21:
		result.Level = BurnoutMild
	default:
		result.Level = BurnoutHealthy
	}

	return result, nil
}

// computeTrend compares average work time of most recent 3 days vs the 3 before those.
func computeTrend(store *db.Store, userID int64, today string, loc *time.Location) (pts int, direction string) {
	t, err := time.Parse(DateLayout, today)
	if err != nil {
		return 0, "unknown"
	}

	var recent, older [3]int64
	for i := 0; i < 3; i++ {
		d := t.AddDate(0, 0, -(i + 1)).Format(DateLayout)
		recent[2-i] = dayWorkSeconds(store, userID, d, loc)
	}
	for i := 0; i < 3; i++ {
		d := t.AddDate(0, 0, -(i + 4)).Format(DateLayout)
		older[2-i] = dayWorkSeconds(store, userID, d, loc)
	}

	var recentAvg, olderAvg float64
	for _, v := range recent {
		recentAvg += float64(v)
	}
	for _, v := range older {
		olderAvg += float64(v)
	}
	recentAvg /= 3.0
	olderAvg /= 3.0

	if olderAvg < 1 {
		if recentAvg > 0 {
			return 15, "new"
		}
		return 5, "stable"
	}

	changePct := math.Round((recentAvg - olderAvg) / olderAvg * 100)
	if recentAvg > olderAvg*1.2 {
		return 15, fmt.Sprintf("+%.0f%%", changePct)
	}
	if olderAvg > recentAvg*1.2 {
		return 0, fmt.Sprintf("%.0f%%", changePct)
	}
	return 5, "stable"
}

// computeTrendFromAvgs is a pure version of the trend computation for testing.
func computeTrendFromAvgs(recentAvg, olderAvg float64) (pts int, direction string) {
	if olderAvg < 1 {
		if recentAvg > 0 {
			return 15, "new"
		}
		return 5, "stable"
	}
	changePct := math.Round((recentAvg - olderAvg) / olderAvg * 100)
	if recentAvg > olderAvg*1.2 {
		return 15, fmt.Sprintf("+%.0f%%", changePct)
	}
	if olderAvg > recentAvg*1.2 {
		return 0, fmt.Sprintf("%.0f%%", changePct)
	}
	return 5, "stable"
}

func dayWorkSeconds(store *db.Store, userID int64, date string, loc *time.Location) int64 {
	events, err := store.EventsForDayByDate(userID, date)
	if err != nil || len(events) == 0 {
		return 0
	}
	day, err := store.GetDay(userID, date)
	if err != nil || day == nil {
		return 0
	}
	y, m, d := parseGregorianDateKey(date)
	dayStart := time.Date(y, time.Month(m), d, 0, 0, 0, 0, loc).Unix()
	dayEnd := time.Date(y, time.Month(m), d, 23, 59, 59, 0, loc).Unix()
	totals := ComputeDailyTotals(events, day.MinBreakThreshold, dayStart, dayEnd)
	return totals.TotalSeconds
}

// buildBurnoutText returns a formatted burnout assessment.
func (h *Handler) buildBurnoutText(userID int64, loc *time.Location) string {
	res, err := h.assessBurnout(userID, loc)
	if err != nil {
		return "Burnout assessment unavailable."
	}

	var b strings.Builder
	b.WriteString(fmt.Sprintf("Burnout Assessment\nLevel: %s (%d/100)\n\n", res.Level, res.Score))

	if res.ConsecutiveDays > 0 {
		b.WriteString(fmt.Sprintf("  Consecutive workdays: %d days (%d pts)\n", res.ConsecutiveDays, res.ConsecutivePts))
	}
	if res.WorkSeconds > 0 {
		wh := float64(res.WorkSeconds) / secondsPerHour
		b.WriteString(fmt.Sprintf("  Today's work: %.1f hours (%d pts)\n", wh, res.LongHoursPts))
	}
	if res.BreakSeconds > 0 {
		br := float64(res.BreakSeconds)
		total := float64(res.WorkSeconds + res.BreakSeconds)
		ratio := br / total * 100
		if ratio > 100 {
			ratio = 100
		}
		b.WriteString(fmt.Sprintf("  Break ratio: %.0f%% (%d pts)\n", ratio, res.BreakRatioPts))
	}
	if res.WeekendPts > 0 {
		b.WriteString(fmt.Sprintf("  Weekend work: yes (%d pts)\n", res.WeekendPts))
	}
	b.WriteString(fmt.Sprintf("  Work trend: %s (%d pts)\n", res.TrendDirection, res.TrendPts))
	if res.LateNightPts > 0 {
		b.WriteString(fmt.Sprintf("  Late-night work: yes (%d pts)\n", res.LateNightPts))
	}

	b.WriteString("\nRecommendations:\n")
	switch res.Level {
	case BurnoutHealthy:
		b.WriteString("  Keep up the balanced routine!")
	case BurnoutMild:
		b.WriteString("  Consider taking short breaks throughout the day.")
		b.WriteString("\n  Make sure to disconnect after work hours.")
	case BurnoutModerate:
		b.WriteString("  Consider taking a day off soon.")
		b.WriteString("\n  Review your workload distribution.")
		b.WriteString("\n  Ensure you are taking adequate breaks.")
	case BurnoutHigh:
		b.WriteString("  Strongly consider taking time off.")
		b.WriteString("\n  Your workload patterns indicate potential strain.")
		b.WriteString("\n  Please prioritize rest and recovery.")
	}

	return b.String()
}

// burnoutAssessment returns the burnout assessment text.
func (h *Handler) burnoutAssessment(chatID int64) (string, error) {
	user, err := h.getOrCreateUser(chatID)
	if err != nil {
		return "", err
	}
	loc := loadLocation(user.Timezone)
	return h.buildBurnoutText(user.ID, loc), nil
}