//
//  DateParser.swift
//  SodaLive
//
//  Created by klaus on 12/19/25.
//

import Foundation

// MARK: - 내부: 다양한 포맷 파서를 시도
enum DateParser {
    static func parse(_ text: String) -> Date? {
        for parser in parsers {
            if let d = parser(text) { return d }
        }
        return nil
    }

    static func relativeTimeText(fromUTC text: String, fallback: String, now: Date = Date()) -> String {
        guard let date = parse(text) else {
            return fallback
        }

        let interval = max(0, now.timeIntervalSince(date))
        let calendar = Calendar.current
        let yearMonth = calendar.dateComponents([.year, .month], from: date, to: now)

        if let years = yearMonth.year, years >= 1 {
            return I18n.Time.yearsAgo(years)
        }

        if let months = yearMonth.month, months >= 1 {
            return I18n.Time.monthsAgo(months)
        }

        if interval < 60 {
            return I18n.Time.justNow
        }

        if interval < 3600 {
            return I18n.Time.minutesAgo(max(1, Int(interval / 60)))
        }

        if interval < 86_400 {
            return I18n.Time.hoursAgo(max(1, Int(interval / 3600)))
        }

        return I18n.Time.daysAgo(max(1, Int(interval / 86_400)))
    }

    static func chatListDateText(fromUTC text: String, fallback: String, now: Date = Date()) -> String {
        guard let date = parse(text) else {
            return fallback
        }

        let interval = max(0, now.timeIntervalSince(date))
        if interval < 60 {
            return I18n.Time.justNow
        }

        if interval < 3600 {
            return I18n.Time.minutesAgo(max(1, Int(interval / 60)))
        }

        if interval < 86_400 {
            return I18n.Time.hoursAgo(max(1, Int(interval / 3600)))
        }

        if interval < 604_800 {
            return I18n.Time.daysAgo(max(1, Int(interval / 86_400)))
        }

        let calendar = Calendar.current
        if calendar.component(.year, from: date) == calendar.component(.year, from: now) {
            let formatter = DateFormatter()
            formatter.locale = Locale(identifier: LanguageHeaderProvider.current)
            formatter.timeZone = calendar.timeZone
            formatter.dateFormat = I18n.MainChat.monthDayDateFormat
            return formatter.string(from: date)
        }

        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.timeZone = calendar.timeZone
        formatter.dateFormat = "yyyy.MM.dd"
        return formatter.string(from: date)
    }
    
    // 시도 순서: ISO8601(소수초 포함) → ISO8601 → RFC3339 유사 → 공백 구분 기본
    private static let parsers: [(String) -> Date?] = [
        { ISO8601.fractional.date(from: $0) },
        { ISO8601.basic.date(from: $0) },
        { DF.rfc3339.date(from: $0) },
        { DF.isoLocalDateTime.date(from: $0) },
        { DF.basic.date(from: $0) }
    ]
    
    private enum ISO8601 {
        static let fractional: ISO8601DateFormatter = {
            let f = ISO8601DateFormatter()
            f.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
            f.timeZone = TimeZone(secondsFromGMT: 0)
            return f
        }()
        
        static let basic: ISO8601DateFormatter = {
            let f = ISO8601DateFormatter()
            f.formatOptions = [.withInternetDateTime]
            f.timeZone = TimeZone(secondsFromGMT: 0)
            return f
        }()
    }
    
    private enum DF {
        static let rfc3339: DateFormatter = {
            let f = DateFormatter()
            f.locale = Locale(identifier: "en_US_POSIX")
            f.timeZone = TimeZone(secondsFromGMT: 0)
            f.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
            return f
        }()
        
        static let basic: DateFormatter = {
            let f = DateFormatter()
            f.locale = Locale(identifier: "en_US_POSIX")
            f.timeZone = TimeZone(secondsFromGMT: 0)
            f.dateFormat = "yyyy-MM-dd HH:mm:ss"
            return f
        }()

        static let isoLocalDateTime: DateFormatter = {
            let f = DateFormatter()
            f.locale = Locale(identifier: "en_US_POSIX")
            f.timeZone = TimeZone(secondsFromGMT: 0)
            f.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
            return f
        }()
    }
}