package api

import (
	"fmt"
	"fuj-management/go/internal/config"
	"fuj-management/go/internal/services/membership"
	"sort"
	"strconv"

	domreconcile "fuj-management/go/internal/domain/reconcile"
)

// buildJuniorsResponse constructs the JuniorsResponse wire type from reconcile output.
// Mirrors scripts/views.py:build_juniors_view_model.
func buildJuniorsResponse(
	members []domreconcile.Member,
	sortedMonths []string,
	result domreconcile.Result,
	txns []domreconcile.Transaction,
	cfg config.Config,
	currentMonth string,
) JuniorsResponse {
	monthLabels := getMonthLabels(sortedMonths, membership.JuniorMergedMonths)

	allNames := make([]string, 0, len(members))
	juniorNames := make([]string, 0, len(members))
	for _, m := range members {
		allNames = append(allNames, m.Name)
		juniorNames = append(juniorNames, m.Name)
	}
	sort.Strings(juniorNames)

	monthlyTotals := make(map[string]*monthSums, len(sortedMonths))
	for _, m := range sortedMonths {
		monthlyTotals[m] = &monthSums{}
	}

	var results []MemberRow
	for _, name := range juniorNames {
		mr := result.Members[name]
		row, unpaidMonths, rawUnpaidMonths := buildJuniorMemberRow(name, mr, sortedMonths, monthLabels, currentMonth, monthlyTotals)
		row.UnpaidPeriods = joinComma(unpaidMonths)
		row.RawUnpaidPeriods = joinPlus(rawUnpaidMonths)
		row.Balance = settledBalance(mr, currentMonth)
		row.PayableAmount = max(0, -row.Balance)
		results = append(results, row)
	}

	// Totals row.
	totalsCells := make([]TotalCell, len(sortedMonths))
	for i, m := range sortedMonths {
		t := monthlyTotals[m] // *monthSums, never nil (initialised above)
		status := "empty"
		if t.expected > 0 || t.paid > 0 {
			switch {
			case t.paid == t.expected:
				status = "ok"
			case t.paid < t.expected:
				status = "unpaid"
			default:
				status = "surplus"
			}
		}
		totalsCells[i] = TotalCell{
			Text:   fmt.Sprintf("%d / %d CZK", t.paid, t.expected),
			Status: status,
		}
	}

	var credits, debts []Credit
	for _, name := range juniorNames {
		bal := settledBalance(result.Members[name], currentMonth)
		if bal > 0 {
			credits = append(credits, Credit{Name: name, Amount: bal})
		} else if bal < 0 {
			debts = append(debts, Credit{Name: name, Amount: -bal})
		}
	}
	sort.Slice(credits, func(i, j int) bool { return credits[i].Name < credits[j].Name })
	sort.Slice(debts, func(i, j int) bool { return debts[i].Name < debts[j].Name })

	// member_data: full reconcile output for all junior members.
	memberData := make(map[string]JuniorsMemberData, len(result.Members))
	for name, mr := range result.Members {
		months := make(map[string]JuniorsMonthData, len(mr.Months))
		for m, md := range mr.Months {
			var exc *ExceptionData
			if md.Exception != nil {
				exc = &ExceptionData{Amount: md.Exception.Amount, Note: md.Exception.Note}
			}
			txEntries := make([]MemberTxEntry, len(md.Transactions))
			for i, te := range md.Transactions {
				txEntries[i] = memberTxFromDomain(te)
			}
			months[m] = JuniorsMonthData{
				Expected:         juniorExpected(md),
				OriginalExpected: juniorOriginalExpected(md),
				AttendanceCount:  md.AttendanceCount,
				Exception:        exc,
				Paid:             md.Paid,
				Transactions:     txEntries,
			}
		}
		otherTxs := make([]MemberOtherEntry, len(mr.OtherTransactions))
		for i, oe := range mr.OtherTransactions {
			otherTxs[i] = memberOtherFromDomain(oe)
		}
		memberData[name] = JuniorsMemberData{
			Tier:              mr.Tier,
			Months:            months,
			OtherTransactions: otherTxs,
			TotalBalance:      mr.TotalBalance,
		}
	}

	unmatched := make([]RawTransaction, len(result.Unmatched))
	for i, tx := range result.Unmatched {
		unmatched[i] = rawTxFromDomain(tx)
	}

	juniorURL := "https://docs.google.com/spreadsheets/d/" + config.AttendanceSheetID +
		"/edit#gid=" + config.JuniorSheetGID

	return JuniorsResponse{
		Months:        labelsForMonths(sortedMonths, monthLabels),
		RawMonths:     sortedMonths,
		Results:       ensureSlice(results),
		Totals:        totalsCells,
		MemberData:    memberData,
		MonthLabels:   monthLabels,
		RawPayments:   groupRawPaymentsByPerson(txns, allNames),
		Credits:       ensureSlice(credits),
		Debts:         ensureSlice(debts),
		Unmatched:     unmatched,
		AttendanceURL: juniorURL,
		PaymentsURL:   "https://docs.google.com/spreadsheets/d/" + config.PaymentsSheetID + "/edit",
		BankAccount:   cfg.QRAccount,
		CurrentMonth:  currentMonth,
	}
}

func buildJuniorMemberRow(
	name string,
	mr domreconcile.MemberResult,
	sortedMonths []string,
	monthLabels map[string]string,
	currentMonth string,
	monthlyTotals map[string]*monthSums,
) (row MemberRow, unpaidMonths, rawUnpaidMonths []string) {
	row = MemberRow{Name: name}
	for _, m := range sortedMonths {
		md, ok := mr.Months[m]
		if !ok {
			md = domreconcile.MonthData{}
		}
		paid := int(md.Paid)

		// Update monthly totals (skip "?" months for expected).
		if t := monthlyTotals[m]; t != nil {
			if !md.IsUnknown {
				t.expected += md.Expected
			}
			t.paid += paid
		}

		// Attendance breakdown string e.g. ":3J,2A".
		var breakdown string
		jc, ac := md.JuniorAttendance, md.AdultAttendance
		switch {
		case jc > 0 && ac > 0:
			breakdown = fmt.Sprintf(":%dJ,%dA", jc, ac)
		case jc > 0:
			breakdown = fmt.Sprintf(":%dJ", jc)
		case ac > 0:
			breakdown = fmt.Sprintf(":%dA", ac)
		}
		countStr := ""
		if md.AttendanceCount > 0 {
			countStr = fmt.Sprintf(" (%d%s)", md.AttendanceCount, breakdown)
		}

		// Fee display string.
		var feeDisplay string
		var isOverridden bool
		if md.Exception != nil {
			overrideAmount := md.Exception.Amount
			var origStr string
			if md.IsUnknown {
				origStr = "?"
				isOverridden = true
			} else {
				origStr = strconv.Itoa(md.OriginalExpected)
				isOverridden = overrideAmount != md.OriginalExpected
			}
			if isOverridden {
				feeDisplay = fmt.Sprintf("%d (%s) CZK%s", overrideAmount, origStr, countStr)
			} else {
				feeDisplay = fmt.Sprintf("%d CZK%s", md.Expected, countStr)
			}
		} else {
			if md.IsUnknown {
				feeDisplay = "? CZK" + countStr
			} else {
				feeDisplay = fmt.Sprintf("%d CZK%s", md.Expected, countStr)
			}
		}

		status := "empty"
		cellText := "-"
		amountToPay := 0

		switch {
		case md.IsUnknown:
			cellText = "?" + countStr
		case md.Expected > 0:
			switch {
			case paid >= md.Expected:
				status = "ok"
				cellText = fmt.Sprintf("%d/%s", paid, feeDisplay)
			case paid > 0:
				status = "partial"
				cellText = fmt.Sprintf("%d/%s", paid, feeDisplay)
				amountToPay = md.Expected - paid
				if m < currentMonth {
					unpaidMonths = append(unpaidMonths, monthLabels[m])
					rawUnpaidMonths = append(rawUnpaidMonths, rawMonthLabel(m))
				}
			default:
				status = "unpaid"
				cellText = fmt.Sprintf("0/%s", feeDisplay)
				amountToPay = md.Expected
				if m < currentMonth {
					unpaidMonths = append(unpaidMonths, monthLabels[m])
					rawUnpaidMonths = append(rawUnpaidMonths, rawMonthLabel(m))
				}
			}
		case paid > 0:
			status = "surplus"
			cellText = fmt.Sprintf("PAID %d", paid)
		}

		tooltip := ""
		if (!md.IsUnknown && md.Expected > 0) || paid > 0 {
			tooltip = fmt.Sprintf("Received: %d, Expected: %d", paid, md.Expected)
		}

		row.Months = append(row.Months, MonthCell{
			Text:       cellText,
			Overridden: isOverridden,
			Status:     status,
			Amount:     amountToPay,
			Month:      monthLabels[m],
			RawMonth:   m,
			Tooltip:    tooltip,
		})
	}
	return row, unpaidMonths, rawUnpaidMonths
}

// juniorExpected converts domain MonthData to the Expected wire type.
// When an exception exists it always produces a concrete int; otherwise
// the "?" sentinel is used when IsUnknown=true.
func juniorExpected(md domreconcile.MonthData) Expected {
	if md.Exception == nil && md.IsUnknown {
		return Expected{Unknown: true}
	}
	return Expected{Value: md.Expected}
}

// juniorOriginalExpected converts the original (pre-exception) expected fee.
func juniorOriginalExpected(md domreconcile.MonthData) Expected {
	if md.IsUnknown {
		return Expected{Unknown: true}
	}
	return Expected{Value: md.OriginalExpected}
}