//
//  TravelPlacementTests.swift
//  SportsTimeTests
//
//  Regression tests for travel segment day placement.
//  Specifically tests that repeat cities (e.g., Follow Team mode)
//  don't cause travel segments to be placed on non-existent days.
//

import XCTest
@testable import SportsTime

@MainActor
final class TravelPlacementTests: XCTestCase {

    // MARK: - Helpers

    private let calendar = TestClock.calendar

    /// Create a date for May 2026 at a given day number.
    private func may(_ day: Int) -> Date {
        var components = DateComponents()
        components.year = 2026
        components.month = 5
        components.day = day
        return calendar.startOfDay(for: calendar.date(from: components)!)
    }

    /// Create a date for March 2026 at a given day number.
    private func mar(_ day: Int) -> Date {
        var components = DateComponents()
        components.year = 2026
        components.month = 3
        components.day = day
        return calendar.startOfDay(for: calendar.date(from: components)!)
    }

    /// Build an array of trip days from start to end (inclusive).
    private func tripDays(from start: Date, to end: Date) -> [Date] {
        var days: [Date] = []
        var current = calendar.startOfDay(for: start)
        let endDay = calendar.startOfDay(for: end)
        while current <= endDay {
            days.append(current)
            current = calendar.date(byAdding: .day, value: 1, to: current)!
        }
        return days
    }

    private func makeStop(city: String, arrival: Date, departure: Date, games: [String] = []) -> TripStop {
        TripStop(
            stopNumber: 1,
            city: city,
            state: "XX",
            arrivalDate: arrival,
            departureDate: departure,
            games: games
        )
    }

    private func makeSegment(from: String, to: String) -> TravelSegment {
        TravelSegment(
            fromLocation: LocationInput(name: from, coordinate: nil),
            toLocation: LocationInput(name: to, coordinate: nil),
            travelMode: .drive,
            distanceMeters: 500_000,
            durationSeconds: 18000
        )
    }

    // MARK: - dayNumber Tests

    func test_dayNumber_returnsCorrectDayForDateWithinTrip() {
        let days = tripDays(from: may(1), to: may(5))

        XCTAssertEqual(TravelPlacement.dayNumber(for: may(1), in: days), 1)
        XCTAssertEqual(TravelPlacement.dayNumber(for: may(3), in: days), 3)
        XCTAssertEqual(TravelPlacement.dayNumber(for: may(5), in: days), 5)
    }

    func test_dayNumber_returnsZeroForDateBeforeTrip() {
        let days = tripDays(from: may(5), to: may(10))
        XCTAssertEqual(TravelPlacement.dayNumber(for: may(3), in: days), 0)
    }

    func test_dayNumber_returnsCountPlusOneForDateAfterTrip() {
        let days = tripDays(from: may(1), to: may(5))
        XCTAssertEqual(TravelPlacement.dayNumber(for: may(8), in: days), 6) // count + 1
    }

    // MARK: - Simple Trip (no repeat cities)

    func test_simpleTwoStopTrip_travelPlacedCorrectly() {
        // Chicago (May 1-3) → Detroit (May 5-6)
        // Travel should be on Day 4 (May 4)
        let stops = [
            makeStop(city: "Chicago", arrival: may(1), departure: may(3)),
            makeStop(city: "Detroit", arrival: may(5), departure: may(6))
        ]
        let segments = [makeSegment(from: "Chicago", to: "Detroit")]

        let trip = Trip(
            name: "Test",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(6))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 1, "Should have 1 travel segment placed")
        XCTAssertNotNil(result[4], "Travel should be placed on Day 4 (May 4)")
    }

    // MARK: - Repeat City Bug (Follow Team regression)

    func test_repeatCity_travelPlacedOnCorrectDay_notGlobalLastGameDay() {
        // Simulates the Astros May 2026 pattern:
        // Houston (May 4-6) → Cincinnati (May 8-10) → Houston (May 11-17) → Chicago (May 22-24) → Houston (May 29-31)
        //
        // BUG: The old code used findLastGameDay("Houston") which returned Day 31,
        // causing Houston→Cincinnati travel to be placed on Day 32 (doesn't exist).
        // FIX: Use stop indices so each segment uses its specific stop's dates.

        let stops = [
            makeStop(city: "Houston", arrival: may(4), departure: may(6)),      // Stop 0
            makeStop(city: "Cincinnati", arrival: may(8), departure: may(10)),   // Stop 1
            makeStop(city: "Houston", arrival: may(11), departure: may(17)),     // Stop 2
            makeStop(city: "Chicago", arrival: may(22), departure: may(24)),     // Stop 3
            makeStop(city: "Houston", arrival: may(29), departure: may(31))      // Stop 4
        ]

        let segments = [
            makeSegment(from: "Houston", to: "Cincinnati"),   // Seg 0: stops[0] → stops[1]
            makeSegment(from: "Cincinnati", to: "Houston"),   // Seg 1: stops[1] → stops[2]
            makeSegment(from: "Houston", to: "Chicago"),      // Seg 2: stops[2] → stops[3]
            makeSegment(from: "Chicago", to: "Houston")       // Seg 3: stops[3] → stops[4]
        ]

        let trip = Trip(
            name: "Follow Astros",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(4), to: may(31))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        // All 4 segments should be placed within the trip's day range
        XCTAssertEqual(result.count, 4, "All 4 travel segments should be placed")

        // Houston→Cincinnati: departure May 6 (Day 3), arrival May 8 (Day 5) → travel on Day 4 (May 7)
        XCTAssertNotNil(result[4], "Houston→Cincinnati travel should be on Day 4 (May 7)")

        // Cincinnati→Houston: departure May 10 (Day 7), arrival May 11 (Day 8) → travel on Day 8 (May 11)
        XCTAssertNotNil(result[8], "Cincinnati→Houston travel should be on Day 8 (May 11)")

        // Houston→Chicago: departure May 17 (Day 14), arrival May 22 (Day 19) → travel on Day 15 (May 18)
        XCTAssertNotNil(result[15], "Houston→Chicago travel should be on Day 15 (May 18)")

        // Chicago→Houston: departure May 24 (Day 21), arrival May 29 (Day 26) → travel on Day 22 (May 25)
        XCTAssertNotNil(result[22], "Chicago→Houston travel should be on Day 22 (May 25)")

        // Critical regression check: NO travel should be placed beyond the trip's day range
        for (day, _) in result {
            XCTAssertGreaterThanOrEqual(day, 1, "Travel day should be >= 1")
            XCTAssertLessThanOrEqual(day, days.count, "Travel day should be <= \(days.count), but got \(day)")
        }
    }

    func test_repeatCity_threeVisits_allTravelSegmentsVisible() {
        // A→B→A→B pattern (city visited 2x each)
        // A (Day 1-2) → B (Day 4-5) → A (Day 7-8) → B (Day 10-11)
        let stops = [
            makeStop(city: "CityA", arrival: may(1), departure: may(2)),
            makeStop(city: "CityB", arrival: may(4), departure: may(5)),
            makeStop(city: "CityA", arrival: may(7), departure: may(8)),
            makeStop(city: "CityB", arrival: may(10), departure: may(11))
        ]

        let segments = [
            makeSegment(from: "CityA", to: "CityB"),
            makeSegment(from: "CityB", to: "CityA"),
            makeSegment(from: "CityA", to: "CityB")
        ]

        let trip = Trip(
            name: "Test Repeat",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(11))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 3, "All 3 travel segments should be placed")

        // All within bounds
        for (day, _) in result {
            XCTAssertGreaterThanOrEqual(day, 1)
            XCTAssertLessThanOrEqual(day, 11)
        }
    }

    // MARK: - Consecutive Stops (no gap)

    func test_consecutiveStops_travelStillPlaced() {
        // Houston (May 1) → Chicago (May 2) - back to back, no rest day
        let stops = [
            makeStop(city: "Houston", arrival: may(1), departure: may(1)),
            makeStop(city: "Chicago", arrival: may(2), departure: may(2))
        ]
        let segments = [makeSegment(from: "Houston", to: "Chicago")]

        let trip = Trip(
            name: "Quick Trip",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(2))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 1, "Travel segment should be placed")
        XCTAssertNotNil(result[2], "Travel should be on Day 2 (arrival day)")
    }

    // MARK: - Next-Day Departure Bug (Featured/Suggested trips)

    func test_nextDayDeparture_travelPlacedOnArrivalDay() {
        // The exact bug scenario from featured trips:
        // Clearwater arrives May 1, departs May 2 (next-morning departure)
        // New Orleans arrives May 2, departs May 3
        //
        // BUG: fromDayNum=2 (May 2), minDay=fromDayNum+1=3, toDayNum=2 (May 2)
        //       minDay(3) > maxDay(2) → fallback uses minDay=3 → travel on Day 3 (WRONG)
        // FIX: Travel should be on Day 2 (the arrival day)
        let stops = [
            makeStop(city: "Clearwater", arrival: may(1), departure: may(2)),
            makeStop(city: "New Orleans", arrival: may(2), departure: may(3))
        ]
        let segments = [makeSegment(from: "Clearwater", to: "New Orleans")]

        let trip = Trip(
            name: "Featured Trip",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(3))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 1, "Should have 1 travel segment placed")
        XCTAssertNotNil(result[2], "Travel should be on Day 2 (arrival day, not Day 3)")
        XCTAssertNil(result[3], "Travel should NOT be on Day 3 (the overshoot)")
    }

    func test_nextDayDeparture_withGap_travelPlacedCorrectly() {
        // Next-day departure with a multi-day gap to next stop:
        // Stop A arrives May 1, departs May 2 (next morning)
        // Stop B arrives May 5, departs May 6
        //
        // fromDayNum=2, minDay=3, toDayNum=5 → minDay(3) <= maxDay(5) → travel on Day 3
        // But ideally travel should be on Day 2 (the departure day itself).
        // After fix: defaultDay = min(fromDayNum+1, toDayNum) = min(3, 5) = 3
        // This is still valid (day 3 is within range), but the key fix is the
        // invalid-range case doesn't apply here.
        let stops = [
            makeStop(city: "StopA", arrival: may(1), departure: may(2)),
            makeStop(city: "StopB", arrival: may(5), departure: may(6))
        ]
        let segments = [makeSegment(from: "StopA", to: "StopB")]

        let trip = Trip(
            name: "Gap Trip",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(6))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 1, "Should have 1 travel segment placed")
        // Travel should be within valid range [3...5], defaulting to Day 3
        let placedDay = result.keys.first!
        XCTAssertGreaterThanOrEqual(placedDay, 2, "Travel should be on or after departure day")
        XCTAssertLessThanOrEqual(placedDay, 5, "Travel should be on or before arrival day")
    }

    func test_threeStops_nextDayDeparture_allSegmentsPlaced() {
        // Full featured trip pattern with 3 stops, all next-day departures:
        // Stop A: arrival Mar 15, departure Mar 16
        // Stop B: arrival Mar 16, departure Mar 17
        // Stop C: arrival Mar 20, departure Mar 21
        //
        // Segment 0 (A→B): fromDayNum=2 (Mar 16), toDayNum=2 (Mar 16)
        //   BUG: minDay=3, maxDay=2 → fallback to minDay=3 (Day 3 = Mar 17) WRONG
        //   FIX: Travel on Day 2 (Mar 16, arrival day)
        //
        // Segment 1 (B→C): fromDayNum=3 (Mar 17), toDayNum=6 (Mar 20)
        //   minDay=4, maxDay=6 → travel on Day 4 (Mar 18) — this works correctly
        let stops = [
            makeStop(city: "StopA", arrival: mar(15), departure: mar(16)),
            makeStop(city: "StopB", arrival: mar(16), departure: mar(17)),
            makeStop(city: "StopC", arrival: mar(20), departure: mar(21))
        ]
        let segments = [
            makeSegment(from: "StopA", to: "StopB"),
            makeSegment(from: "StopB", to: "StopC")
        ]

        let trip = Trip(
            name: "Three Stop Featured",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: mar(15), to: mar(21))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 2, "Both travel segments should be placed")

        // Segment 0 (A→B): should be on Day 2 (Mar 16, the arrival/departure day)
        XCTAssertNotNil(result[2], "A→B travel should be on Day 2 (Mar 16)")

        // Segment 1 (B→C): should be on Day 3 or 4 (Mar 17 or 18, within valid range)
        let seg1Day = result.first(where: { $0.key != 2 })?.key
        XCTAssertNotNil(seg1Day, "B→C travel should be placed")
        if let day = seg1Day {
            XCTAssertGreaterThanOrEqual(day, 3, "B→C travel should be on or after Day 3")
            XCTAssertLessThanOrEqual(day, 6, "B→C travel should be on or before Day 6")
        }
    }

    // MARK: - Same-Day Collision (dictionary overwrite bug)

    func test_twoSegmentsSameDay_neitherLost() {
        // 3 back-to-back single-game stops with next-morning departures:
        // Stop A: arrival May 1, departure May 2
        // Stop B: arrival May 2, departure May 3
        // Stop C: arrival May 3, departure May 4
        //
        // Segment 0 (A→B): fromDayNum=2, toDayNum=2 → defaultDay=2, clampedDefault=2
        // Segment 1 (B→C): fromDayNum=3, toDayNum=3 → defaultDay=3, clampedDefault=3
        //
        // These don't collide, but a tighter scenario does:
        // If A departs May 2 and B arrives May 2 AND departs May 2, C arrives May 2:
        // Both segments resolve to Day 2 → collision.
        //
        // Realistic tight scenario:
        // Stop A: May 1-1 (same-day), Stop B: May 2-2, Stop C: May 2-3
        // Segment 0 (A→B): fromDayNum=1, toDayNum=2 → defaultDay=2
        // Segment 1 (B→C): fromDayNum=2, toDayNum=2 → defaultDay=2
        // Both = Day 2 → COLLISION: segment 0 overwritten.
        let stops = [
            makeStop(city: "CityA", arrival: may(1), departure: may(1)),
            makeStop(city: "CityB", arrival: may(2), departure: may(2)),
            makeStop(city: "CityC", arrival: may(2), departure: may(3))
        ]
        let segments = [
            makeSegment(from: "CityA", to: "CityB"),
            makeSegment(from: "CityB", to: "CityC")
        ]

        let trip = Trip(
            name: "Tight Trip",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(3))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        // Both segments must be present — neither should be silently dropped
        let allSegments = result.values.flatMap { $0 }
        XCTAssertEqual(allSegments.count, 2, "Both travel segments must be preserved (no collision)")

        // Day 2 should have both segments
        let day2Segments = result[2] ?? []
        XCTAssertEqual(day2Segments.count, 2, "Day 2 should have 2 travel segments")
    }

    // MARK: - Repeat City Pair ID Collision

    func test_repeatCityPair_overridesDoNotCollide() {
        // Follow Team pattern: Houston→Cincinnati→Houston→Cincinnati
        // Two segments share the same city pair (Houston→Cincinnati)
        // Each must get a unique travel anchor ID so overrides don't collide.
        _ = [
            makeStop(city: "Houston", arrival: may(1), departure: may(2)),      // Stop 0
            makeStop(city: "Cincinnati", arrival: may(4), departure: may(5)),   // Stop 1
            makeStop(city: "Houston", arrival: may(7), departure: may(8)),      // Stop 2
            makeStop(city: "Cincinnati", arrival: may(10), departure: may(11))  // Stop 3
        ]

        _ = [
            makeSegment(from: "Houston", to: "Cincinnati"),   // Seg 0: stops[0] → stops[1]
            makeSegment(from: "Cincinnati", to: "Houston"),   // Seg 1: stops[1] → stops[2]
            makeSegment(from: "Houston", to: "Cincinnati")    // Seg 2: stops[2] → stops[3]
        ]

        // Simulate what stableTravelAnchorId should produce WITH segment index
        let id0 = "travel:0:houston->cincinnati"
        let id1 = "travel:1:cincinnati->houston"
        let id2 = "travel:2:houston->cincinnati"

        // All IDs must be unique
        XCTAssertNotEqual(id0, id2, "Repeat city pair segments must have unique IDs")
        XCTAssertEqual(Set([id0, id1, id2]).count, 3, "All 3 travel IDs must be unique")

        // Simulate overrides dictionary — each segment gets its own entry
        var overrides: [String: Int] = [:]  // travel ID → day override
        overrides[id0] = 3   // Seg 0 overridden to day 3
        overrides[id2] = 9   // Seg 2 overridden to day 9

        // Verify no collision — seg 0 override is NOT overwritten by seg 2
        XCTAssertEqual(overrides[id0], 3, "Segment 0 override should be day 3")
        XCTAssertEqual(overrides[id2], 9, "Segment 2 override should be day 9")
        XCTAssertNil(overrides[id1], "Segment 1 has no override")
    }

    func test_singleSegmentPerDay_returnsArrayOfOne() {
        // Ensure the new array return type still works for the simple case
        let stops = [
            makeStop(city: "Houston", arrival: may(1), departure: may(3)),
            makeStop(city: "Chicago", arrival: may(5), departure: may(6))
        ]
        let segments = [makeSegment(from: "Houston", to: "Chicago")]

        let trip = Trip(
            name: "Simple",
            preferences: TripPreferences(),
            stops: stops,
            travelSegments: segments,
            totalGames: 0,
            totalDistanceMeters: 0,
            totalDrivingSeconds: 0
        )

        let days = tripDays(from: may(1), to: may(6))
        let result = TravelPlacement.computeTravelByDay(trip: trip, tripDays: days)

        XCTAssertEqual(result.count, 1, "Should have 1 day with travel")
        let day4Segments = result[4] ?? []
        XCTAssertEqual(day4Segments.count, 1, "Day 4 should have exactly 1 travel segment")
    }
}