import Foundation
import Testing
@testable import ForgejoKit

struct DateDecodingTests {

    private func decoder() -> JSONDecoder {
        let d = JSONDecoder()
        d.dateDecodingStrategy = forgejoDateDecodingStrategy
        return d
    }

    private struct DateWrapper: Codable {
        let date: Date
    }

    private var utcCalendar: Calendar {
        var calendar = Calendar(identifier: .gregorian)
        calendar.timeZone = TimeZone(identifier: "UTC")!
        return calendar
    }

    // MARK: - ISO 8601 without fractional seconds

    @Test func decodesDateWithoutFractionalSeconds() throws {
        let json = #"{"date":"2024-01-15T10:30:00Z"}"#
        let result = try decoder().decode(DateWrapper.self, from: Data(json.utf8))

        #expect(utcCalendar.component(.year, from: result.date) == 2024)
        #expect(utcCalendar.component(.month, from: result.date) == 1)
        #expect(utcCalendar.component(.day, from: result.date) == 15)
        #expect(utcCalendar.component(.hour, from: result.date) == 10)
        #expect(utcCalendar.component(.minute, from: result.date) == 30)
    }

    // MARK: - ISO 8601 with fractional seconds

    @Test func decodesDateWithFractionalSeconds() throws {
        let json = #"{"date":"2024-06-20T14:05:30.123Z"}"#
        let result = try decoder().decode(DateWrapper.self, from: Data(json.utf8))

        #expect(utcCalendar.component(.year, from: result.date) == 2024)
        #expect(utcCalendar.component(.month, from: result.date) == 6)
        #expect(utcCalendar.component(.day, from: result.date) == 20)
        #expect(utcCalendar.component(.hour, from: result.date) == 14)
    }

    @Test func decodesDateWithTripleZeroFraction() throws {
        let json = #"{"date":"2024-01-15T10:30:00.000Z"}"#
        let result = try decoder().decode(DateWrapper.self, from: Data(json.utf8))

        #expect(utcCalendar.component(.second, from: result.date) == 0)
    }

    // MARK: - Invalid dates

    @Test func throwsOnInvalidDateString() {
        let json = #"{"date":"not-a-date"}"#
        #expect(throws: DecodingError.self) {
            _ = try decoder().decode(DateWrapper.self, from: Data(json.utf8))
        }
    }

    @Test func throwsOnEmptyDateString() {
        let json = #"{"date":""}"#
        #expect(throws: DecodingError.self) {
            _ = try decoder().decode(DateWrapper.self, from: Data(json.utf8))
        }
    }

    // MARK: - Both formats decode to same value

    @Test func bothFormatsProduceSameDate() throws {
        let jsonWithout = #"{"date":"2024-03-10T08:00:00Z"}"#
        let jsonWith = #"{"date":"2024-03-10T08:00:00.000Z"}"#

        let d = decoder()
        let resultWithout = try d.decode(DateWrapper.self, from: Data(jsonWithout.utf8))
        let resultWith = try d.decode(DateWrapper.self, from: Data(jsonWith.utf8))

        #expect(resultWithout.date == resultWith.date)
    }
}