package matching

import (
	"fmt"
	"fuj-management/go/internal/domain/czech"
	"time"
)

// Transaction is the subset of a payment row used by InferTransactionDetails.
// Date accepts string ("YYYY-MM-DD"), float64 (Sheets serial), or int — matching
// the heterogeneous types returned by the Sheets API and the FIO scraper.
type Transaction struct {
	Sender  string
	Message string
	UserID  string
	Date    any
}

// InferredDetails is the result of InferTransactionDetails.
type InferredDetails struct {
	Members    []Match
	Months     []string
	SearchText string
}

// InferTransactionDetails infers which member(s) and month(s) a transaction belongs to.
//
// Search text for member matching: sender + message + user_id.
// Month search text: message + user_id only (sender excluded, matching Python).
// Fallback 1: if no members found, retry match on sender alone.
// Fallback 2: if no months found, derive from tx.Date (Sheets serial or YYYY-MM-DD).
//
// defaultYear seeds czech.ParseMonthReferences (Python defaulted to the current year;
// callers should pass time.Now().Year() or a fixed year for deterministic tests).
//
// Ports scripts/match_payments.py infer_transaction_details.
func InferTransactionDetails(tx Transaction, memberNames []string, defaultYear int) InferredDetails {
	searchText := fmt.Sprintf("%s %s %s", tx.Sender, tx.Message, tx.UserID)

	members := MatchMembers(searchText, memberNames)
	months := czech.ParseMonthReferences(tx.Message+" "+tx.UserID, defaultYear)

	if len(members) == 0 {
		members = MatchMembers(tx.Sender, memberNames)
	}

	if len(months) == 0 && tx.Date != nil && tx.Date != "" {
		if ym := inferMonthFromDate(tx.Date); ym != "" {
			months = []string{ym}
		}
	}

	if months == nil {
		months = []string{}
	}

	return InferredDetails{
		Members:    members,
		Months:     months,
		SearchText: searchText,
	}
}

// inferMonthFromDate converts a date value to "YYYY-MM" for the month fallback.
// Returns "" on any error, matching Python's bare except pass.
func inferMonthFromDate(val any) string {
	switch v := val.(type) {
	case int:
		dt := sheetsEpoch.Add(time.Duration(float64(v) * 24 * float64(time.Hour)))
		return dt.Format("2006-01")
	case int64:
		dt := sheetsEpoch.Add(time.Duration(float64(v) * 24 * float64(time.Hour)))
		return dt.Format("2006-01")
	case float64:
		dt := sheetsEpoch.Add(time.Duration(v * 24 * float64(time.Hour)))
		return dt.Format("2006-01")
	case string:
		if v == "" {
			return ""
		}
		dt, err := time.Parse("2006-01-02", v)
		if err != nil {
			return ""
		}
		return dt.Format("2006-01")
	default:
		return ""
	}
}