import Foundation

@main
enum UserCreatorChatDatePresentationCheck {
    static var assertions = 0

    static func check(_ condition: Bool, _ message: String) {
        guard condition else { print("FAIL: \(message)"); exit(1) }
        assertions += 1
    }

    static func checkTitles(for date: Date, calendar: Calendar, timeZone: TimeZone, expected: [String], label: String) {
        for (localeID, expectedTitle) in zip(["ko_KR", "en_US", "ja_JP"], expected) {
            let title = UserCreatorChatDatePresentation.title(
                for: date,
                locale: Locale(identifier: localeID),
                calendar: calendar,
                timeZone: timeZone
            )
            check(title == expectedTitle, "\(label) \(localeID): expected '\(expectedTitle)', got '\(title)'")
        }
    }

    static func main() {
        let utc = TimeZone(secondsFromGMT: 0)!
        let seoul = TimeZone(identifier: "Asia/Seoul")!
        let losAngeles = TimeZone(identifier: "America/Los_Angeles")!
        var calendar = Calendar(identifier: .gregorian)
        calendar.timeZone = utc
        var seoulCalendar = calendar
        seoulCalendar.timeZone = seoul
        var losAngelesCalendar = calendar
        losAngelesCalendar.timeZone = losAngeles

        let fixtures: [(label: String, timestamp: String, calendar: Calendar, timeZone: TimeZone, expected: [String])] = [
            ("Gregorian UTC fixture", "2026-10-16T12:00:00Z", calendar, utc,
             ["2026년 10월 16일 금요일", "Friday, October 16, 2026", "2026年10月16日 金曜日"]),
            ("previous year", "2025-10-16T12:00:00Z", calendar, utc,
             ["2025년 10월 16일 목요일", "Thursday, October 16, 2025", "2025年10月16日 木曜日"]),
            ("UTC boundary", "2026-10-16T15:30:00Z", calendar, utc,
             ["2026년 10월 16일 금요일", "Friday, October 16, 2026", "2026年10月16日 金曜日"]),
            ("Seoul boundary in every app locale", "2026-10-16T15:30:00Z", seoulCalendar, seoul,
             ["2026년 10월 17일 토요일", "Saturday, October 17, 2026", "2026年10月17日 土曜日"]),
            ("Los Angeles boundary in every app locale", "2026-10-16T15:30:00Z", losAngelesCalendar, losAngeles,
             ["2026년 10월 16일 금요일", "Friday, October 16, 2026", "2026年10月16日 金曜日"]),
            ("Los Angeles calendar normalized to Seoul", "2026-10-16T15:30:00Z", losAngelesCalendar, seoul,
             ["2026년 10월 17일 토요일", "Saturday, October 17, 2026", "2026年10月17日 土曜日"]),
            ("Seoul calendar normalized to Los Angeles", "2026-10-16T15:30:00Z", seoulCalendar, losAngeles,
             ["2026년 10월 16일 금요일", "Friday, October 16, 2026", "2026年10月16日 金曜日"])
        ]
        let isoFormatter = ISO8601DateFormatter()
        for fixture in fixtures {
            checkTitles(
                for: isoFormatter.date(from: fixture.timestamp)!,
                calendar: fixture.calendar,
                timeZone: fixture.timeZone,
                expected: fixture.expected,
                label: fixture.label
            )
        }

        let englishMonths = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]
        let englishWeekdays = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]
        let koreanWeekdays = ["일요일", "월요일", "화요일", "수요일", "목요일", "금요일", "토요일"]
        let japaneseWeekdays = ["日曜日", "月曜日", "火曜日", "水曜日", "木曜日", "金曜日", "土曜日"]
        let today = Date()
        let yesterday = calendar.date(byAdding: .day, value: -1, to: today)!
        for (label, date) in [("today without relative wording", today), ("yesterday without relative wording", yesterday)] {
            let components = calendar.dateComponents([.year, .month, .day, .weekday], from: date)
            let year = components.year!
            let month = components.month!
            let day = components.day!
            let weekday = components.weekday! - 1
            checkTitles(
                for: date,
                calendar: calendar,
                timeZone: utc,
                expected: [
                    "\(year)년 \(month)월 \(day)일 \(koreanWeekdays[weekday])",
                    "\(englishWeekdays[weekday]), \(englishMonths[month - 1]) \(day), \(year)",
                    "\(year)年\(month)月\(day)日 \(japaneseWeekdays[weekday])"
                ],
                label: label
            )
        }
        print("PASS: \(assertions) assertions")
    }
}