package changes

import (
	"fmt"
	"sort"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/module"
	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
)

func CompareThreeDay(previous module.Snapshot, current module.Snapshot, thresholds Thresholds) ([]Change, error) {
	previousDayparts, err := requiredStanza[map[string]daypartSummaryStanza](previous, "derived_daypart_summaries")
	if err != nil {
		return nil, fmt.Errorf("previous daypart summaries: %w", err)
	}
	currentDayparts, err := requiredStanza[map[string]daypartSummaryStanza](current, "derived_daypart_summaries")
	if err != nil {
		return nil, fmt.Errorf("current daypart summaries: %w", err)
	}
	previousDays := outlookDaysFromDayparts(previousDayparts)
	currentDays := outlookDaysFromDayparts(currentDayparts)
	return compareOutlookDays(previousDays, currentDays, thresholds, "")
}

type outlookDay struct {
	Date           string
	LowTempF       *int
	HighTempF      *int
	MaxPopPercent  *int
	MaxPopTime     string
	MaxWindGustMph *int
	Indicators     indicators
}

func compareOutlookDays(previousDays map[string]outlookDay, currentDays map[string]outlookDay, thresholds Thresholds, prefix string) ([]Change, error) {
	var changes []Change
	for date, currentDay := range currentDays {
		previousDay, ok := previousDays[date]
		if !ok {
			changes = append(changes, Change{Type: prefix + "outlook_day_added", Message: fmt.Sprintf("Outlook day added: %s.", date), Current: date})
			continue
		}
		changes = append(changes, compareOutlookDay(date, previousDay, currentDay, thresholds, prefix)...)
	}
	for date := range previousDays {
		if _, ok := currentDays[date]; !ok {
			changes = append(changes, Change{Type: prefix + "outlook_day_removed", Message: fmt.Sprintf("Outlook day removed: %s.", date), Previous: date})
		}
	}
	sortChanges(changes)
	return changes, nil
}

func compareOutlookDay(date string, previous outlookDay, current outlookDay, thresholds Thresholds, prefix string) []Change {
	var changes []Change
	for _, change := range compareTemperatureValues("Low", previous.LowTempF, current.LowTempF, thresholds.TemperatureDegrees) {
		change.Message = date + ": " + change.Message
		change.Type = prefix + "outlook_" + change.Type
		changes = append(changes, change)
	}
	for _, change := range compareTemperatureValues("High", previous.HighTempF, current.HighTempF, thresholds.TemperatureDegrees) {
		change.Message = date + ": " + change.Message
		change.Type = prefix + "outlook_" + change.Type
		changes = append(changes, change)
	}
	for _, change := range comparePrecipitationValues(previous.MaxPopPercent, current.MaxPopPercent, thresholds.PrecipProbabilityPoints, prefix+"outlook_") {
		change.Message = date + ": " + change.Message
		changes = append(changes, change)
	}
	for _, change := range comparePrecipTiming(previous.MaxPopTime, current.MaxPopTime, thresholds.PrecipTimingShiftMinutes, prefix+"outlook_") {
		change.Message = date + ": " + change.Message
		changes = append(changes, change)
	}
	for _, change := range compareWindValues(previous.MaxWindGustMph, current.MaxWindGustMph, thresholds.WindGustMilesPerHour, prefix+"outlook_") {
		change.Message = date + ": " + change.Message
		changes = append(changes, change)
	}
	for _, change := range compareIndicators(previous.Indicators, current.Indicators, prefix+"outlook_") {
		change.Message = date + ": " + change.Message
		changes = append(changes, change)
	}
	return changes
}

func outlookDaysFromDayparts(dayparts map[string]daypartSummaryStanza) map[string]outlookDay {
	out := map[string]outlookDay{}
	var keys []string
	for key := range dayparts {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	for _, key := range keys {
		daypart := dayparts[key]
		date := daypartDate(daypart)
		if date == "" {
			continue
		}
		day := out[date]
		day.Date = date
		low, high := parseTempRange(daypart.TempRangeF)
		day.LowTempF = minInt(day.LowTempF, low)
		day.HighTempF = maxInt(day.HighTempF, high)
		day.MaxPopPercent = maxInt(day.MaxPopPercent, daypart.MaxPopPercent)
		if daypart.MaxPopPercent != nil && day.MaxPopPercent != nil && *daypart.MaxPopPercent == *day.MaxPopPercent {
			day.MaxPopTime = daypart.MaxPopTime
		}
		day.MaxWindGustMph = maxInt(day.MaxWindGustMph, daypart.MaxWindGustMph)
		day.Indicators.Snow = day.Indicators.Snow || daypart.Snow
		day.Indicators.Ice = day.Indicators.Ice || daypart.Ice
		out[date] = day
	}
	return out
}

func daypartDate(daypart daypartSummaryStanza) string {
	if !daypart.Period.Start.IsZero() {
		return daypart.Period.Start.Format(timeutil.DateLayout)
	}
	return ""
}

func minInt(a *int, b *int) *int {
	if a == nil {
		return copyInt(b)
	}
	if b != nil && *b < *a {
		return copyInt(b)
	}
	return a
}

func maxInt(a *int, b *int) *int {
	if a == nil {
		return copyInt(b)
	}
	if b != nil && *b > *a {
		return copyInt(b)
	}
	return a
}

func copyInt(value *int) *int {
	if value == nil {
		return nil
	}
	copied := *value
	return &copied
}